Jeffrey W Jacobs
 Professor, AerospaceMechanical Engineering
 Distinguished Professor, Elwin Wood
Contact
 (520) 6218459
 Aerospace & Mechanical Engr., Rm. N705
 Tucson, AZ 85721
 jwjacobs@email.arizona.edu
Awards
 Elwyn Wood distinguished professor
 Fall 2008
Interests
No activities entered.
Courses
201819 Courses

Instrumentation Lab
AME 300 (Spring 2019) 
Research
AME 900 (Spring 2019) 
Internal Combustion Engines
AME 434 (Fall 2018) 
Research
AME 900 (Fall 2018)
201718 Courses

Instrumentation Lab
AME 300 (Spring 2018) 
Research
AME 900 (Spring 2018) 
Dissertation
AME 920 (Fall 2017) 
Instrumentation Lab
AME 300 (Fall 2017) 
Research
AME 900 (Fall 2017)
201617 Courses

Gasdynamics
AME 323 (Spring 2017) 
Thesis
AME 910 (Spring 2017) 
Research
AME 900 (Fall 2016) 
Thesis
AME 910 (Fall 2016)
Scholarly Contributions
Journals/Publications
 Morgan, R. V., Cabot, W. H., Greenough, J. A., & Jacobs, J. W. (2018). Rarefactiondriven RayleighTaylor instability. Part 2. Experiments and simulations in the nonlinear regime. JOURNAL OF FLUID MECHANICS, 838, 320355.
 Krivets, V. V., Ferguson, K. J., & Jacobs, J. W. (2017). Turbulent Mixing Induced by RichtmyerMeshkov Instability. SHOCK COMPRESSION OF CONDENSED MATTER  2015, 1793.
 Morgan, R. V., Likhachev, O. A., & Jacobs, J. W. (2016). Rarefactiondriven RayleighTaylor instability. Part 1. Diffuseinterface linear stability measurements and theory. JOURNAL OF FLUID MECHANICS, 791, 3460.
 Roberts, M. S., & Jacobs, J. W. (2016). The effects of forced smallwavelength, finitebandwidth initial perturbations and miscibility on the turbulent RayleighTaylor instability. JOURNAL OF FLUID MECHANICS, 787, 5083.
 Jacobs, J. W., Krivets, V. V., Tsiklashvili, V., & Likhachev, O. A. (2013). Experiments on the RichtmyerMeshkov instability with an imposed, random initial perturbation. SHOCK WAVES, 23(4), 407413.
 Jacobs, J. W., Krivets, V. V., Tsiklashvili, V., & Likhachev, O. A. (2013). Experiments on the RichtmyerMeshkov instability with an imposed, random initial perturbation. Shock Waves, 23(4), 407413.More infoAbstract: A vertical shock tube is used to perform experiments on the RichtmyerMeshkov instability with a threedimensional random initial perturbation. A membraneless flat interface is formed by opposed gas flows in which the light and heavy gases enter the shock tube from the top and from the bottom of the shock tube driven section. An air/SF6 gas combination is used and a Mach number M = 1.2 incident shock wave impulsively accelerates the interface. Initial perturbations on the interface are created by vertically oscillating the gas column within the shock tube to produce Faraday waves on the interface resulting in a short wavelength, threedimensional perturbation. Planar Mie scattering is used to visualize the flow in which light from a laser sheet is scattered by smoke seeded in the air, and image sequences are captured using three highspeed video cameras. Measurements of the integral penetration depth prior to reshock show two growth behaviors, both having power law growth with growth exponents in the range found in previous experiments and simulations. Following reshock, all experiments show very consistent linear growth with a growth rate in good agreement with those found in previous studies. © 2013 SpringerVerlag Berlin Heidelberg.
 Morgan, R. V., Aure, R., Stockero, J. D., Greenough, J. A., Cabot, W., Likhachev, O. A., & Jacobs, J. W. (2012). On the latetime growth of the twodimensional RichtmyerMeshkov instability in shock tube experiments. JOURNAL OF FLUID MECHANICS, 712, 354383.
 Morgan, R. V., Aure, R., Stockero, J. D., Greenough, J. A., Cabot, W., Likhachev, O. A., & Jacobs, J. W. (2012). On the latetime growth of the twodimensional RichtmyerMeshkov instability in shock tube experiments. Journal of Fluid Mechanics, 712, 354383.More infoAbstract: In the present study, shock tube experiments are used to study the very latetime development of the RichtmyerMeshkov instability from a diffuse, nearly sinusoidal, initial perturbation into a fully turbulent flow. The interface is generated by two opposing gas flows and a perturbation is formed on the interface by transversely oscillating the shock tube to create a standing wave. The puncturing of a diaphragm generates a Mach 1.2 shock wave that then impacts a density gradient composed of air and SF6, causing the RichtmyerMeshkov instability to develop in the 2.0 m long test section. The instability is visualized with planar Mie scattering in which smoke particles in the air are illuminated by a Nd:YLF laser sheet, and images are recorded using four highspeed video cameras operating at 6 kHz that allow the recording of the time history of the instability. In addition, particle image velocimetry (PIV) is implemented using a doublepulsed Nd:YAG laser with images recorded using a single CCD camera. Initial modal content, amplitude, and growth rates are reported from the Mie scattering experiments while vorticity and circulation measurements are made using PIV. Amplitude measurements show good earlytime agreement but relatively poor latetime agreement with existing nonlinear models. The model of Goncharov (Phys. Rev. Lett., vol. 88, 2002, 134502) agrees with growth rate measurements at intermediate times but fails at late experimental times. Measured background acceleration present in the experiment suggests that the latetime growth rate may be influenced by RayleighTaylor instability induced by the interfacial acceleration. Numerical simulations conducted using the LLNL codes Ares and Miranda show that this acceleration may be caused by the growth of boundary layers, and must be accounted for to produce good agreement with models and simulations. Adding acceleration to the RichtmyerMeshkov buoyancydrag model produces improved agreement. It is found that the growth rate and amplitude trends are also modelled well by the LikhachevJacobs vortex model (Likhachev & Jacobs, Phys. Fluids, vol. 17, 2005, 031704). Circulation measurements also show good agreement with the circulation value extracted by fitting the vortex model to the experimental data. © 2012 Cambridge University Press.
 Tsiklashvili, V., E., P., Likhachev, O. A., & Jacobs, J. W. (2012). An experimental study of small Atwood number RayleighTaylor instability using the magnetic levitation of paramagnetic fluids. Physics of Fluids, 24(5).More infoAbstract: Experiments that take advantage of the properties of paramagnetic liquids are used to study RayleighTaylor (RT) instability. A gravitationally unstable, miscible combination of a paramagnetic salt solution and a nonmagnetic solution is initially stabilized by a magnetic field gradient that is produced by the contoured polecaps of a large electromagnet. RayleighTaylor instability originates from infinitesimal random background noise with the rapid removal of current from the electromagnet, which results in the heavy liquid falling into the light liquid due to gravity and, thus, mixing with it. The mixing zone is visualized by backlit photography and is recorded with a digital video camera. Several miscible, small Atwood number (A ≤ 0.1) combinations of paramagnetic and nonmagnetic solutions are used. It is found that the RT flow is insensitive to the viscosities of the fluids composing the twofluid system, and that the growth parameter α also does not show dependence on the Atwood number when the experiments are initialized under the same conditions. It is also observed that the turbulent mixing zone grows linearly with time following a period of selfsimilar quadratic growth. When the width of the mixing zone becomes comparable with the crosssectional length scale of the experimental container, the bubble front characteristic velocity approaches a constant value, similar to that observed with a single bubble rising in the confined volume, with Froude number measured in the range Fr = 0.38÷0.45. However, flow visualization does not reveal any persistent largescale perturbations, which would dominate the flow during this stage. We believe that this phenomenon is not an attribute of the given magnetic experiments and has been observed in many other experimental studies, which involve RT instability evolving in confined volumes. © 2012 American Institute of Physics.
 Tsiklashvili, V., Romero, C., Likhachev, O. A., & Jacobs, J. W. (2012). An experimental study of small Atwood number RayleighTaylor instability using the magnetic levitation of paramagnetic fluids. PHYSICS OF FLUIDS, 24(5).
 Aure, R., & Jacobs, J. W. (2009). Particle image velocimetry study of shockinduced single mode RichtmyerMeshkov instability. SHOCK WAVES, VOL 2, PROCEEDINGS, 11931198.
 Krivets, V. V., Long, C. C., Jacobs, J. W., & Greenough, J. A. (2009). Shock tube experiments and numerical simulation of the single mode threedimensional RichtmyerMeshkov instability. SHOCK WAVES, VOL 2, PROCEEDINGS, 1205+.
 Long, C. C., Krivets, V. V., Greenough, J. A., & Jacobs, J. W. (2009). Shock tube experiments and numerical simulation of the singlemode, threedimensional RichtmyerMeshkov instability. PHYSICS OF FLUIDS, 21(11).
 Long, C. C., Krivets, V. V., Greenough, J. A., & Jacobs, J. W. (2009). Shock tube experiments and numerical simulation of the singlemode, threedimensional RichtmyerMeshkov instability. Physics of Fluids, 21(11), 19.More infoAbstract: A vertical shock tube is used to perform experiments in which an interface is formed using opposed flows of air and SF6. A threedimensional singlemode perturbation is created by the periodic vertical motion of the gases within the shock tube. RichtmyerMeshkov instability is produced by an impulsive acceleration by a weak shock wave (Ms=1.2). Planar laser induced fluorescence produces still images, and planar Mie scattering produces movies of the experiment. A threedimensional numerical simulation of this experiment utilizing the Eulerian adaptive mesh refinement code, RAPTOR, was also conducted. Good agreement is obtained between experiments and the simulations. However, existing late time models, which have a 1/t dependence, disagree with measurements of the late time instability development. In contrast, both the experiments and simulation suggest a t0.54 late time dependence for the overall growth rate. Comparisons with individual bubble and spike velocities show the bubbles appear to decay approximately at 1/t and the spikes to decay at a much slower rate of t0.38. © 2009 American Institute of Physics.
 Olson, D. H., & Jacobs, J. W. (2009). Experimental study of RayleighTaylor instability with a complex initial perturbation. PHYSICS OF FLUIDS, 21(3).
 Aure, R., & Jacobs, J. W. (2008). Particle image velocimetry study of the shockinduced single mode RichtmyerMeshkov instability. SHOCK WAVES, 18(3), 161167.
 Aure, R., & Jacobs, J. W. (2008). Particle image velocimetry study of the shockinduced single mode RichtmyerMeshkov instability. Shock Waves, 18(3), 161167.More infoAbstract: Full field particle image velocimetry (PIV) measurements are obtained for the first time in RichtmyerMeshkov instability shock tube experiments. The experiments are carried out in a vertical shock tube in which the light gas (air) and the heavy gas (SF6) flow from opposite ends of the shock tube driven section and exit through narrow slots at the interface location. A sinusoidal perturbation is given to the interface by oscillating the shock tube in the horizontal direction. RichtmyerMeshkov instability is then produced by the interaction with a weak shock wave (M s = 1.21). PIV measurements are obtained by seeding the flow with 0.30 μm polystyrene Latex spheres which are illuminated using a doublepulsed Nd:YAG laser. PIV measurements indicate the vorticity to be distributed in a sheetlike distribution on the interface immediately after shock interaction and that this distribution quickly rolls up into compact vortices. The integration of the vorticity distribution over one half wave length shows the circulation to increase with time in qualitative agreement with the numerical study of Peng et al. (Phys. Fluids, 15, 37303744, 2003). © 2008 SpringerVerlag.
 Wilkinson, J. P., & Jacobs, J. W. (2007). Experimental study of the singlemode threedimensional RayleighTaylor instability. PHYSICS OF FLUIDS, 19(12).
 Wilkinson, J. P., & Jacobs, J. W. (2007). Experimental study of the singlemode threedimensional RayleighTaylor instability. Physics of Fluids, 19(12).More infoAbstract: The threedimensional RayleighTaylor instability is studied in a low Atwood number (A≈0.15) miscible fluid system. The two fluids are contained within a Plexiglas tank that is mounted on vertical rails and accelerated downward by a weight and pulley system. A net acceleration between 13 and 23m/s2 can be maintained, resulting in an effective body force equivalent to 0.331.35 times Earth's gravity. A singlemode, threedimensional perturbation is produced by oscillating the tank, which has a square cross section, along its diagonal. Early time measured growth rates are shown to have good agreement with linear stability theory. At late time, the instability exhibits a nonconstant vertical interfacial velocity in agreement with the recent numerical computations of Ramaprabhu [Phys. Rev. E 74, 066308 (2006)]. Both the latetime bubble and spike velocities have values greater than those predicted by both the simple buoyancydrag model developed by Oron [Phys. Plasmas 8, 2883 (2001)] and the potential flow model of Goncharov [Phys. Rev. Lett. 88, 134502 (2002)]. The disagreement with the models can be attributed to the formation of vortices, in this case vortex rings, observed in the experiments but not accounted for by the models. © 2007 American Institute of Physics.
 Chapman, P. R., & Jacobs, J. W. (2006). Erratum: "Experiments on the threedimensional incompressible RichtmyerMeshkov instability" (Physical Fluids (2006) vol. 18). Physics of Fluids, 18(12).
 Chapman, P. R., & Jacobs, J. W. (2006). Experiments on the threedimensional incompressible RichtmyerMeshkov instability" (vol 18, art no 074101, 2006). PHYSICS OF FLUIDS, 18(12).
 Chapman, P. R., & Jacobs, J. W. (2006). Experiments on the threedimensional incompressible RichtmyerMeshkov instability. PHYSICS OF FLUIDS, 18(7).
 Chapman, P. R., & Jacobs, J. W. (2006). Experiments on the threedimensional incompressible RichtmyerMeshkov instability. Physics of Fluids, 18(7).More infoAbstract: The threedimensional (3D) RichtmyerMeshkov instability of incompressible, miscible liquids with a 3D singlemode initial perturbation is investigated. This study uses the apparatus of the earlier experiments of Niederhaus and Jacobs [J. Fluid Mech. 485, 243 (2003)] in which the instability is generated by impulsively accelerating a tank containing the two liquids. However, the present investigation uses a tank with square cross section allowing the generation of a squaremode 3D initial perturbation by lateral oscillation along the tank's diagonal. Amplitude measurements of the 3D instability are found to be effectively collapsed by the dimensionless scaling used in the twodimensional (2D) study and to be in good agreement with linear stability theory up until a dimensionless time kv0t ≈ 1, later than is found for the 2D flow. Latetime 3D amplitude measurements show faster growth than 2D as is predicted by popular bubble models. However, latetime growth rate measurements are found to deviate from model predictions at the latest times showing a constant growth rate instead of the 1/t dependence given by the models. The constant latetime growth rate is the result of the observed vorticity distribution which takes the form of an array of upward and downward traveling vortex rings. This fundamental difference between existing models and observation indicates that bubble models may not be suitable for predicting the behavior of the low Atwood number instability which is vortex dominated. © 2006 American Institute of Physics.
 Jacobs, J. W., & Dalziel, S. B. (2005). RayleighTaylor instability in complex stratifications. JOURNAL OF FLUID MECHANICS, 542, 251279.
 Jacobs, J. W., & Dalziel, S. B. (2005). RayleighTaylor instability in complex stratifications. Journal of Fluid Mechanics, 542, 251279.More infoAbstract: The RayleighTaylor instability of a system of three fluids separated by one unstable and one stable interface has been investigated experimentally. The experiments were gravitationally driven and conducted with miscible liquids consisting of salt solutions and fresh water. The lower two layers are initially gravitationally stable and are formed by depositing the lighter fluid on top of a thicker layer of the heavier one. The relatively thick top layer is initially separated from the two lower layers by a rigid barrier that is removed at the start of an experiment. In situations where the density of the bottomlayer fluid equals that of the toplayer fluid, the resulting turbulent flow is found to be selfsimilar as demonstrated by the collapse of the mean concentration distributions as well as the behaviour of the decay of the peak of the mean concentration profiles. In this configuration, the erosion of the bottom layer by the turbulence generated by the upper unstable interface is found to be small. When the density of the bottomlayer fluid is increased above that of the toplayer fluid, the degree of erosion is further decreased. In the cases where the lower interface is stably stratified at latetime, the entrainment rate E at the lower (statically stable) interface is found to follow a power law of the Richardson number, i.e. E ∝ Rin, with n ≈ 1.3, a result in agreement with studies of mixing induced by oscillating grids. When the density of the bottomlayer fluid is decreased below that of the toplayer fluid, the erosion increases as expected. However, in this case, the overall density distribution is such that it is globally RayleighTaylor unstable at late time. In this situation, the turbulent mixing region at late times grows similarly to that of singleinterface RayleighTaylor instability with approximately the same value of the growth constant. In these latetime unstable experiments the density profile approaches that of an equivalent twolayer RayleighTaylor unstable system. © 2005 Cambridge University Press.
 Jacobs, J. W., & Krivets, V. V. (2005). Experiments on the latetime development of singlemode RichtmyerMeshkov instability. PHYSICS OF FLUIDS, 17(3).
 Jacobs, J. W., & Krivets, V. V. (2005). Experiments on the latetime development of singlemode RichtmyerMeshkov instability. Physics of Fluids, 17(3), 034105103410510.More infoAbstract: The latetime development of RichtmyerMeshkov instability is studied in shock tube experiments. This investigation makes use of the experimental apparatus and visualization methods utilized in the earlier study of Collins and Jacobs [J. Fluid Mech. 464, 113 (2002)] but employs stronger shocks and initial perturbations with shorter wavelengths to obtain much latertime (in the dimensionless sense) images of the singlemode instability. These modifications produce a very detailed look at the evolution of the latetime singlemode instability, revealing the transition and development of turbulence in the vortex cores that eventually results in the disintegration of the laminar vortex structures into small scale features. Amplitude measurements taken from these images are shown to be effectively collapsed when plotted in dimensionless variables defined using the wave number and the initial growth rate. The amplitude measurements are compared with several latetime nonlinear models and solutions. The best agreement is obtained with the model of Sadot [Phys. Rev. Lett. 80, 1654 (1998)] which can be slightly improved by modifying the expression for the latetime asymptotic growth rate. © 2005 American Institute of Physics.
 Likhachev, O. A., & Jacobs, J. W. (2005). A vortex model for RichtmyerMeshkov instability accounting for finite Atwood number. PHYSICS OF FLUIDS, 17(3).
 Likhachev, O. A., & Jacobs, J. W. (2005). A vortex model for RichtmyerMeshkov instability accounting for finite Atwood number. Physics of Fluids, 17(3), 03170410317043.More infoAbstract: The vortex model developed by Jacobs and Sheeley ["Experimental study of incompressible RichtmyerMeshkov instability," Phys. Fluids 8, 405 (1996)] is essentially a solution to the governing equations for the case of a uniform density fluid. Thus, this model strictly speaking only applies to the case of vanishing small Atwood number. A modification to this model for small to finite Atwood number is proposed in which the vortex row utilized is perturbed such that the vortex spacing is smaller across the spikes and larger across the bubbles, a fact readily observed in experimental images. It is shown that this modification more effectively captures the behavior of experimental amplitude measurements, especially when compared with separate bubble and spike data. In addition, it is shown that this modification will cause the amplitude to deviate from the logarithmic result given by the heuristic models at late time. © 2005 American Institute of Physics.
 Mueschke, N. J., Kraft, W. N., Andrews, M. J., & Jacobs, J. W. (2005). Numerical investigation of internal vortex structure in two dimensional, incompressible RichtmyerMeshkov flows. American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FED, 261 FED, 109118.More infoAbstract: RichtmyerMeshkov (RM) instability occurs when one fluid is impulsively accelerated into a second fluid, such that ρ1 ρ2. This research numerically investigates RM instabilities between incompressible media, similar to the experiments reported by Niederhaus & Jacobs [1]. A twodimensional, finitevolume numerical algorithm has been developed to solve the variable density NavierStokes equations explicitly on a Cartesian, colocated grid. In previous calculations, no physical viscosity was implemented; however, small scale fluctuations were damped by the numerical algorithm. In contrast, current simulations incorporate the physical viscosities reported by Niederhaus & Jacobs [1] and are explicitly used. Calculations of volume fraction and momentum advections are secondorder accurate in space. Unphysical oscillations due to the higherorder advection scheme are minimized through the use of a Van Leer flux limiting algorithm. An initial velocity impulse [2] has been used to model the impulsive acceleration history found in the experiments of Niederhaus & Jacobs [1]. Both inviscid and viscous simulations result in similar growth rates for the interpenetration of one fluid into another. However, the inviscid simulations (i.e. no explicit viscosity) are unable to capture the full dynamics of the internal vortex structure that exists between the two fluids due to the absence of viscous effects. Copyright © 2005 by ASME.
 Mueschke, N., Kraft, W. N., Dibua, O., Andrews, M. J., & Jacobs, J. W. (2005). Numerical investigation of singlemode RichtmyerMeshkov instability. Proceedings of 2005 ASME Fluids Engineering Division Summer Meeting, FEDSM2005, 2005, 625633.More infoAbstract: The RichtmyerMeshkov (RM) instability occurs when a shock passes through a perturbed interface separating fluids of different densities. Similarly, RM instabilities may also occur when a perturbed interface between two incompressible fluids of different density is impulsively accelerated. We report work that investigates RM instabilities between incompressible media by way of numerical simulations that are matched to experiments reported by Niederhaus & Jacobs [1]. We also describe a compact, fractional timestep, twodimensional, finitevolume numerical algorithm that solves the nonBousinesq Euler equations explicitly on a Cartesian, colocated grid. Numerical advection of volume fractions and momentum is secondorder accurate in space and unphysical oscillations are prevented by using Van Leer flux limiters [2,3]. An initial velocity impulse has been used to model the impulsive acceleration history found in the experiments [1]. We report accurate simulation of the experimentally measured early, intermediate, and latetime penetrations of one fluid into another. Copyright © 2005 by ASME.
 Niederhaus, C. E., & Jacobs, J. W. (2004). An experimental study of the RichtmyerMeshkov instability in microgravity. Annals of the New York Academy of Sciences, 1027, 403413.More infoPMID: 15644371;Abstract: RichtmyerMeshkov (RM) instability occurs when a planar interface separating two fluids of different density is impulsively accelerated in the direction of its normal. It is one of the most fundamental fluid instabilities and is of importance to the fields of astrophysics and inertial confinement fusion. Because RM instability experiments are normally carried out in shock tubes, where the generation of a sharp, wellcontrolled interface between gases is difficult, there is a scarcity of good experimental results. The experiments presented here use a novel technique that circumvents many of the experimental difficulties that have previously limited the study of RM instability in shock tubes. In these experiments, the instability is generated incompressibly, by bouncing a rectangular tank containing two liquids off of a fixed spring. These experiments, which utilize PLIF flow visualization, yield timemotion image sequences of the nonlinear development and transition to turbulence of the instability that are of a quality unattainable in shock tube experiments. Measurements obtained from these images, therefore, provide benchmark data for the evaluation of nonlinear models for the latetime growth of the instability. Because the run time in these experiments is limited, new experiments in the NASA Glenn 2.2 second drop tower, capable of achieving longer run times, are currently under way.
 Niederhaus, C. E., & Jacobs, J. W. (2004). An experimental study of the RichtmyerMeshkov instability in microgravity. TRANSPORT PHENOMENA IN MICROGRAVITY, 1027, 403413.
 Niederhaus, C. E., & Jacobs, J. W. (2003). Experimental study of the RichtmyerMeshkov instability of incompressible fluids. JOURNAL OF FLUID MECHANICS, 485, 243277.
 Niederhaus, C. E., & Jacobs, J. W. (2003). Experimental study of the RichtmyerMeshkov instability of incompressible fluids. Journal of Fluid Mechanics, 243277.More infoAbstract: The RichtmyerMeshkov instability of a lowAtwoodnumber miscible twoliquid system is investigated experimentally. The initially stratified fluids are contained within a rectangular tank mounted on a sled that rides on a vertical set of rails. The instability is generated by dropping the sled onto a coil spring, producing a nearly impulsive upward acceleration. The subsequent freefall that occurs as the container travels upward and then downward on the rails allows the instability to evolve in the absence of gravity. The interface separating the two liquids initially has a welldefined sinusoidal perturbation that quickly inverts and then grows in amplitude after undergoing the impulsive acceleration. Disturbance amplitudes are measured and compared to theoretical predictions. Linear stability theory gives excellent agreement with the measured initial growth rate, ao, for singlemode perturbations with the predicted amplitudes differing by less than 10% from experimental measurements up to a nondimensional time kaot = 0.7, where k is the wavenumber. Linear stability theory also provides excellent agreement for the individual mode amplitudes of multimode initial perturbations until the interface becomes multivalued. Comparison with previously published weakly nonlinear singlemode models shows good agreement up to kaot = 3, whereas published nonlinear singlemode models provide good agreement up to kaot = 30. The effects of Reynolds number on the vortex core evolution and overall growth rate of the interface are also investigated. Measurements of the overall amplitude are found to be unaffected by the Reynolds number for the range of values studied here. However, experiments carried out at lower values of Reynolds numbers were found to have decreased vortex core rotation rates. In addition, an instability in the vortex cores is observed. The time of appearance of this instability was found to increase when the Reynolds number is decreased.
 Collins, B. D., & Jacobs, J. W. (2002). PLIF flow visualization and measurements of the RichtmyerMeshkov instability of an air/SF6 interface. JOURNAL OF FLUID MECHANICS, 464, 113136.
 Collins, B. D., & Jacobs, J. W. (2002). PLIF flow visualization and measurements of the RichtmyerMeshkov instability of an air/SF_{6} interface. Journal of Fluid Mechanics, 464, 113136.More infoAbstract: Investigations of the RichtmyerMeshkov instability carried out in shock tubes have traditionally used membranes to separate the two gases. The use of membranes, in addition to introducing other experimental difficulties, impedes the use of advanced visualization techniques such as planar laserinduced fluorescence (PLIF). Jones and Jacobs (1997) recently developed a new technique by which a perturbed, membranefree gasgas interface can be created in a shock tube. The gases enter the shock tube from opposite ends and exit through two small slots on opposite sides of the test section, forming a stagnation point flow at the interface location. A gentle rocking motion of the shock tube then provides the initial perturbation in the form of a standing wave. The original investigation using this technique utilized dense for seeding for visualization, which allowed largescale effects to be observed, but was incapable of resolving smallerscale features. PLIF visualization is used in the present study to investigate the instability generated by two incident shock strengths (Ms = 1.11 and 1.21), yielding very clear digital images of the flow. Earlytime growth rate measurements obtained from these experiments are found to be in excellent agreement with incompressible linear stability theory (appropriately adjusted for a diffuse interface). Very good agreement is also found between the latetime amplitude measurements and the nonlinear models of Zhang and Sohn (1997) and Sadot et al. (1998). Comparison of images from the Ms = 1.11 and 1.21 sequences reveals a significant increase in the amount of turbulent mixing in the higherMachnumber experiments, suggesting that a mixing transition has occurred.
 Waddell, J. T., Niederhaus, C. E., & Jacobs, J. W. (2001). Experimental study of RayleighTaylor instability: Low Atwood number liquid systems with singlemode initial perturbations. PHYSICS OF FLUIDS, 13(5), 12631273.
 Waddell, J. T., Niederhaus, C. E., & Jacobs, J. W. (2001). Experimental study of RayleighTaylor instability: Low atwood number liquid systems with singlemode perturbations. Physics of Fluids, 13(5), 12631273.More infoAbstract: Singlemode RayleighTaylor instability is experimentally studied in low Atwood number fluid systems. The fluids are contained in a tank that travels vertically on a linear rail system. A singlemode initial perturbation is given to the initially stably stratified interface by gently oscillating the tank in the horizontal direction to form standing internal waves. A weight and pulley system is used to accelerate the fluids downward in excess of the earth's gravitational acceleration. Weight ranging from 90 to 450 kg produces body forces acting upward on the fluid system equivalent to those produced by a gravitational force of 0.331.35 times the earth's gravity. Two fluid combinations are investigated: A miscible system consisting of a salt water solution and a wateralcohol solution; and an immiscible system consisting of a salt solution and heptane to which surfactant has been added to reduce the interfacial tension. The instability is visualized using planar laserinduced fluorescence and is recorded using a video camera that travels with the fluid system. The growth in amplitude of the instability is determined from the digital images and the body forces on the fluid system are measured using accelerometers mounted on the tank. Measurements of the initial growth rate are found to agree well with linear stability theory. The average of the latetime bubble and spike velocities is observed to be constant and described by Uave = 0.22( √∏AG/k(1 + A) + √∏AG/k(1  A)), where A is the Atwood number, k is the wave number, and G is the apparent gravity of the fluid system (i.e., the fluid system acceleration minus the earth's gravity). © 2001 American Institute of Physics.
 Niederhaus, C. E., & Jacobs, J. W. (1998). Instability of an impulsively accelerated liquid/liquid interface. PHYSICS OF FLUIDS, 10(9), S6S6.
 Zuercher, E. J., Jacobs, J. W., & Chen, C. F. (1998). Experimental study of the stability of boundarylayer flow along a heated, inclined plate. JOURNAL OF FLUID MECHANICS, 367, 125.
 Zuercher, E. J., Jacobs, J. W., & Chen, C. F. (1998). Experimental study of the stability of boundarylayer flow along a heated, inclined plate. Journal of Fluid Mechanics, 367, 125.More infoAbstract: Experiments are conducted to study the longitudinal vortices that develop in the boundary layer on the upper surface of an inclined, heated plate. An isothermal plate in water is inclined at angles ranging from 20 to 60 degrees (from the vertical) while the temperature difference is varied from 2 to 23°C. A doublepass Schlieren system is used to visualize the vortices and particle image velocimetry (PIV) is used to measure velocities. In addition, a unique method is developed such that both the Schlieren visualization and PIV can be performed simultaneously. The wavelengths of the vortices and the critical modified Reynolds numbers (R̃) for the onset, merging, and breakup of the vortices are determined from Schlieren images for Pr = 5.8. The critical values for R̃ and the critical wavelengths are compared to results of previous experiments and stability analyses. The spatial growth rates of vortices are determined by using the PIV measurements to determine how the circulation in the vortices grows with distance from the leading edge. This is the first time that the growth rate of the vortices have been found using velocity measurements. These spatial growth rates are compared to the results of Iyer & Kelly (1974) and found to be in general agreement. By defining a suitable circulation threshold, the critical R̃ for the onset of the vortices can be found from the growth curves.
 Jones, M. A., & Jacobs, J. W. (1997). A membraneless experiment for the study of RichtmyerMeshkov instability of a shockaccelerated gas interface. PHYSICS OF FLUIDS, 9(10), 30783085.
 Jones, M. A., & Jacobs, J. W. (1997). A membraneless experiment for the study of RichtmyerMeshkov instability of a shockaccelerated gas interface. Physics of Fluids, 9(10), 30783085.More infoAbstract: Previous RichtmyerMeshkov instability experiments carried out in shock tubes have been hampered by the need to separate the two gases with a thin plastic membrane. As a result, many of these experiments have had poor agreement with the linear stability theory of Richtmyer [Commun. Pure Appl. Math. 23, 297 (1960)]. This limitation has been removed in the present investigation by the use of a novel technique in which the interface is formed by flowing light (N2) and heavy (SF6) gases from opposite ends of a vertical shock tube. Both gases exit the shock tube through slots in the test section walls leaving behind a flat motionless interface which is then given a sinusoidal initial shape by gently oscillating the shock tube at a prescribed frequency in the horizontal direction. A weak shock wave (Ms = 1.10), generated in the shock tube, impacts the interface and produces the instability. Photographs of the interface, which is visualized by seeding the heavy gas with a water droplet fog and illuminating it with a strobe light source, provide particularly clear views of the developing instability far into the nonlinear regime. In addition, amplitude measurements obtained from these photographs are found to be in good agreement with Richtmyer's theory. © 1997 American Institute of Physics.
 Niederhaus, C. E., Champagne, F. H., & Jacobs, J. W. (1997). Scalar transport in a swirling transverse jet. AIAA JOURNAL, 35(11), 16971704.
 Niederhaus, C. E., Champagne, F. H., & Jacobs, J. W. (1997). Scalar transport in a swirling transverse jet. AIAA Journal, 35(11), 16971704.More infoAbstract: The scalar transport in a swirling jet in a crossflow has been investigated in water tunnel experiments. The jet to freestream velocity ratio was varied from 4.9 to 11.1, and the jet swirl numbers ranged from 0 to 0.17. The jet exit Reynolds number was kept at 1.3 × 104 during the experiments. Planar laserinduced fluorescence was utilized to measure planar cross sections of the mean concentration field of the jet up to 68 jet diameters downstream of the exit. The jet penetration depth, halfvalue radius, and maximum concentration were determined from these concentration fields. For jets without swirl, measured crosssectional mean concentration distributions have symmetric doublelobed kidney shapes that are consistent with the counterrotating vortex pair that is known to exist in the far field of the jet. The addition of swirl causes the farfield distributions to become nonsymmetric, with one of the lobes increasing in size and the other decreasing, resulting in a comma shape. Swirl is also observed to decrease jet penetration but not to significantly affect the decay of maximum mean concentration for the range of swirl numbers investigated.
 Jacobs, J. W., & Niederhaus, C. E. (1996). Experimental study of RichtmyerMeshkov instability. NASA Conference Publication, 271276.More infoAbstract: RichtmyerMeshkov (RM) instability occurs when a planar interface separating two fluids of different density is impulsively accelerated in the direction of its normal. It is one of the most fundamental of fluid instabilities and is of importance in fields ranging from astrophysics to materials processing. Because RM instability experiments are normally carried out in shock tubes, where the generation of a sharp well controlled interface between gases is difficult, there is a scarcity of good experimental results. The experiments presented here utilize a novel technique which circumvents many of the experimental difficulties that have previously limited the study of RM instability. In this system, the instability is generated by bouncing a thin rectangular tank containing two liquids off of a fixed spring. Results obtained from these experiments yield particularly well visualized images of the nonlinear development of the instability. However, because the run time in these experiments is limited, new experiments capable of achieving longer run times are planned.
 Jacobs, J. W., & Sheeley, J. M. (1996). Experimental study of incompressible RichtmyerMeshkov instability. PHYSICS OF FLUIDS, 8(2), 405415.
 Jacobs, J. W., & Sheeley, J. M. (1996). Experimental study of incompressible RichtmyerMeshkov instability. Physics of Fluids, 8(2), 405415.More infoAbstract: The RichtmyerMeshkov instability of a twoliquid system is investigated experimentally. These experiments utilize a novel technique that circumvents many of the experimental difficulties that have previously limited the study of RichtmyerMeshkov instability. The instability is generated by vertically accelerating a tank containing two stratified liquids by bouncing it off of a fixed coil spring. A controlled twodimensional sinusoidal initial shape is given to the interface by oscillating the container in the horizontal direction to produce standing waves. The motion of the interface is recorded during the experiments using standard video photography. Instability growth rates are measured and compared with existing linear theory. Disagreement between measured growth rates and the theory are accredited to the finite bounce length. When the linear stability theory is modified to account for an acceleration pulse of finite duration, much better agreement is attained. Late time growth curves of many different experiments seem to collapse to a single curve when correlated with the circulation deposited by the impulsive acceleration. A theory based on modeling the late time evolution of the instability using a row of vortices is developed. The growth curve given by this model has similar shape to those measured, but underestimates the latetime growth rate. © 1996 American Institute of Physics.
 James, R. D., Jacobs, J. W., & Glezer, A. (1996). A round turbulent jet produced by an oscillating diaphragm. PHYSICS OF FLUIDS, 8(9), 24842495.
 James, R. D., Jacobs, J. W., & Glezer, A. (1996). A round turbulent jet produced by an oscillating diaphragm. Physics of Fluids, 8(9), 24842495.More infoAbstract: A round turbulent water jet produced normal to, and at the center of a submerged, resonantly driven diaphragm is investigated experimentally. The jet which is formed without mass injection and is comprised entirely of radially entrained fluid, is present only when the excitation amplitude exceeds a given threshold. Above this excitation level, a small cluster of cavitation bubbles appears near the center of the diaphragm. The bubbles grow, apparently collapse, and then disappear during each oscillation cycle. It is conjectured that the jet is synthesized by timeperiodic coalescence of vortex rings that are produced by secondary flow around the bubbles or by the collapse of the bubbles. It is remarkable that even though the jet results from a strong timeperiodic excitation and its timeperiodic features are detected throughout the present range of measurements, the timeaveraged jet structure is similar to that of a conventional turbulent round jet in that the increase in its width and in the inverse of its centerline velocity are both linear functions of the distance from the actuator. In contrast to conventional jets, the present synthetic jets can be manipulated on relatively short time scales that are comparable to the excitation period. © 1996 American Institute of Physics.
 JACOBS, J. W., JENKINS, D. G., KLEIN, D. L., & BENJAMIN, R. F. (1995). NONLINEAR GROWTH OF THE SHOCKACCELERATED INSTABILITY OF A THIN FLUID LAYER. JOURNAL OF FLUID MECHANICS, 295, 2342.
 Jacobs, J. W., Jenkins, D. G., Klein, D. L., & Benjamin, R. F. (1995). Nonlinear growth of the shockaccelerated instability of a thin fluid layer. Journal of Fluid Mechanics, 295, 2342.More infoAbstract: RichtmyerMeshkov instability causes spatially periodic perturbations initially imposed on a shockaccelerated, thin gas layer to develop into one of three distinct flow patterns. Planar laserinduced fluorescence imaging of the evolving layer, produced by a perturbed SF6 planar jet in air, shows an apparent flow bifurcation that is observed as mushroomshaped or sinuousshaped interfacial patterns. Analysis of this nonlinear instability growth, accomplished by modelling the flow field as a row of line vortices, predicts that the layer thickness grows logarithmically at later times and compares well with our measurements. Because the row of vortices is unstable, the model also provides an explanation for the appearance of the three observed interfacial patterns.
 Budzinski, J. M., Benjamin, R. F., & Jacobs, J. W. (1994). Influence of initial conditions on the flow patterns of a shockaccelerated thin fluid layer. Physics of Fluids, 6(11), 35103512.More infoAbstract: Previous observations of three flow patterns generated by shock acceleration of a thin perturbed, fluid layer are now correlated with asymmetries in the initial conditions. Using a different diagnostic (planar laser Rayleigh scattering) than the previous experiments, upstream mushrooms, downstream mushrooms, and sinuous patterns are still observed. For each experiment the initial perturbation amplitude on one side of the layer can either be larger, smaller, or the same as the amplitude on the other side, as observed with two images per experiment, and these differences lead to the formation of the different patterns. © 1994 American Institute of Physics.
 JACOBS, J. W., KLEIN, D. L., JENKINS, D. G., & BENJAMIN, R. F. (1993). INSTABILITY GROWTHPATTERNS OF A SHOCKACCELERATED THIN FLUID LAYER. PHYSICAL REVIEW LETTERS, 70(5), 583586.
 Jacobs, J. W., Klein, D. L., Jenkins, D. G., & Benjamin, R. F. (1993). Instability growth patterns of a shockaccelerated thin fluid layer. Physical Review Letters, 70(5), 583586.More infoAbstract: Laserinduced fluorescence imaging of a shockaccelerated thin gas layer, produced by a planar SF6 jet in air, shows multiple flow evolutions. RichtmyerMeshkov instability causes spatially periodic perturbations initially imposed on the jet to develop into one of three distinct flow patterns, indicating nonlinear instability growth. Slight differences in the vorticity distribution deposited on the airSF6 interfaces by the shock interaction produce a bifurcated flow, observed as mushroomshaped or sinuousshaped interfacial patterns.
 Jacobs, J. W. (1992). Shockinduced mixing of a lightgas cylinder. J. FLUID MECHANICS, 234, 629649.More infoAbstract: Discusses experiments to quantify the mixing induced by the interaction of a weak shock wave with a cylindrical volume of a gas (helium) that is lighter than its surroundings (air). A round laminar jet was used to produce the light gas cylinder, and planer laser induced fluorescence (PLIF) used for flow visualization. The distortion of the helium cylinder, and downstream displacement of several points on the boundary of the light gas cylinder, were similar to other experimental and computational findings. As the PLIF image area inside the contour (at one half the maximum concentration of the tracer) decreases as the two gases are mixed, a measure of mixing rate is obtained as 0.7 X10 "SUP 3" s "SUP 1" (time rate of change in the image area divided by area of the initial jet). (from Author)
 Jacobs, J. W. (1992). The dynamics of shock accelerated light and heavy gas cylinders. Physics of Fluids A, 5(9), 22392247.More infoAbstract: Experiments have been carried out in which a cylindrical volume of a gas, that is either lighter or heavier than its surroundings, is impulsively accelerated by a weak shock wave. Laminar jets of helium or sulphur hexafluoride (SF6) are used to produce the cylinders, and planar laserinduced fluorescence is used to visualize the flow. It is found that the vorticity deposited on the boundary of the SF6 cylinder by the interaction with the shock wave, separates from the heavy gas to form a pair of vortices, which subsequently wrap the SF6 around them. This process is quite different from what is observed in the light gas experiments, which showed a small amount of helium to remain with the vorticity, eventually becoming part of the vortex cores. Centrifugal forces combined with differences in the rates of the diffusion of vorticity in the two gases are given as possible reasons for these differences. Measurement of the initial downstream velocity for a heavy gas cylinder is found to agree well with a theory based on two simple models. But, because diffusion causes the light gas jet density to be significantly greater than that of pure helium, the theory overpredicts the measured velocity of the light gas experiments. The final translational velocities for both light and heavy gas experiments are not accurately predicted by the model, and measurements of the vortex spacing are found to be significantly larger than those indicated by this theory. These differences are likely caused by the theory's inability to accurately describe the viscous nonuniform flow. © 1993 American Institute of Physics.
 Jacobs, J. W., & Catton, I. (1988). THREEDIMENSIONAL RAYLEIGHTAYLOR INSTABILITY. PART 1. WEAKLY NONLINEAR THEORY.. Journal of Fluid Mechanics, 187, 329352.More infoAbstract: Threedimensional weakly nonlinear RayleighTaylor instability is analyzed. The stability of a confined inviscid liquid and an overlying gas with density much less than that of the liquid is considered. An asymptotic solution for containers of arbitrary crosssectional geometry, valid up to order epsilon **3 (where epsilon is the rootmeansquared initial surface slope) is obtained. The solution is evaluated for the rectangular and circular geometries and for various initial modes (square, hexagonal, axisymmetric, etc. ). It is found that the hexagonal and axisymmetric instabilitie grow faster than any other shapes in their respective geometries. In addition it is found that, sufficiently below the cutoff wavenumber, instabiilties that are equally proportioned in the lateral directions grow faster than those with longer, thinner shape. However, near the cutoff wavenumber this trend reverses with instabilities having zero aspect ratio growing faster than those with aspect ratio near 1.
 Jacobs, J. W., & Catton, I. (1988). THREEDIMENSIONAL RAYLEIGHTAYLOR INSTABILITY. PART 2. EXPERIMENT.. Journal of Fluid Mechanics, 187, 353371.More infoAbstract: Threedimensional RayleighTaylor instability, induced by accelerating a small volume of water down a vertical tube using air pressure, is investigated. Two geometries are studied: a 15. 875 cm circular tube and a 12. 7 cm square tube. Runs were made with initial disturbances in the form of standing waves forced by shaking the test section in a lateral direction. Accelerations ranging from 5 to 10 times gravitational acceleration and wavenumbers from 1 cm** minus **1 to 8 cm** minus **1 are studied. The resulting instabiilty was recorded and later analyzed using highspeed motion picture photography. Measurements of the growth rate are found to agree well with linear theory. In addition, good qualitative agreement between photographs and threedimensional surface plots of the weakly nonlinear solution of Part 1 of this series is obtained.
 Jacobs, J. W., Bunster, A., Catton, I., & Plesset, M. S. (1985). EXPERIMENTAL RAYLEIGHTAYLOR INSTABILITY IN A CIRCULAR TUBE.. Journal of Fluids Engineering, Transactions of the ASME, 107(4), 460466.More infoAbstract: The RayleighTaylor instability of an airwater system has been investigated experimentally. The instability was produced by accelerating a slug of water down a vertical circular tube of 6. 25 in. inside diameter employing a pressure differential. Accelerations from 3 to 25 times gravitational acceleration with fluid depths from 5 to 20 centimeters were studied. The disturbances first observed were purely axisymmetric with wave numbers corresponding closely to the fastest growing values given by linear theory. Later stages of planform development were characterized by a series of transitions which cannot be predicted by linear theory. These transitions were correlated with disturbance height.
 Jacobs, J. W., Catton, I., & Plesset, M. S. (1984). HYDRODYNAMIC STABILITY OF RAPIDLY EVAPORATING LIQUIDS WITH TIME DEPENDENT BASE STATES.. Journal of Fluids Engineering, Transactions of the ASME, 106(3), 352358.More infoAbstract: The hydrodynamic stability of a rapidly evaporating liquid surface is examined. The problem is modeled to mimic the case of a superheated liquid in equilibrium with its vapor in which, the pressure above the liquid surface is dropped suddenly. Both the liquid and its vapor are assumed to be inviscid, incompressible and semiinfinite in extent. In addition, the temperature dependence of fluid properties is neglected. A linear stability analysis is applied to this model. This study differs from previous work in that time dependent base states are used. As a result, a system of linear homogeneous diffential equations must be integrated in time.
 Prosperetti, A., & Jacobs, J. W. (1983). A numerical method for potential flows with a free surface. Journal of Computational Physics, 51(3), 365386.More infoAbstract: A finitedifference numerical method for an accurate and efficient solution of transient potential flow problems with a free surface is described and illustrated with application to the RayleighTaylor instability and the expulsion of liquid from a pipe immersed in a tank. The novel feature of the method consists of the adoption of special differentiation formulae to calculate the liquid velocity at the free surface with much greater accuracy and stability than previously possible. © 1983.
Presentations
 Ferguson, K., Mokler, M., & Jacobs, J. W. (2018, July). The RichtmyerMeshkov Instability in a TwoShock Vertical Shock Tube. 16th International Workshop on the Physics of Compressible Turbulent Mixing. Marseille, France.
 Ferguson, K., Sewell, E., & Jacobs, J. W. (2018, November). Experiments on the RichtmyerMeshkov Instability in a dualshock vertical shock tube. 71st Annual Meeting of the APS Division of Fluid Dynamics. Atlanta, GA.
 Jacobs, J. W. (2018, February). An Experimental Study of the Turbulent Development of RayleighTaylor and RichtmyerMeshkov Instabilities. The Stockpile Stewardship Academic Alliances Program Symposium. Washington, DC: National Nuclear Security Administration.
 Jacobs, J. W. (2018, July). Experiments and Models of the RayleighTaylor and RichtmyerMeshkov Instabilities. 16th International Workshop on the Physics of Compressible Turbulent Mixing. Marseille, France.
 Jacobs, J. W., & Mokler, M. (2018, November). Experimental Study of the Incompressible RichtmyerMeshkov Instability. 71st Annual Meeting of the APS Division of Fluid Dynamics. Atlanta, GA.
 Mokler, M., Krivets, V., & Jacobs, J. W. (2018, July). Incompressible RichtmyerMeshkov Instability Experiments using Miscible and Immiscible Fluids. 16th International Workshop on the Physics of Compressible Turbulent Mixing. Marseille, France.
 Jacobs, J. W. (2016, July). Experiments on the RichtmyerMeshkov instability. International Workshop on the Physics of Compressible Turbulent Mixing. Sydney, Australia.
 Jacobs, J. W. (2013, July). Vorticity and vortex models in shock accelerated gas inhomogeneities. 29th International Symposium on Shock Waves. Madison, WI.
Poster Presentations
 Sewell, E., Krivets, V., & Jacobs, J. W. (2018, July). Time Resolved Particle Image Velocimetry Measurements of the Richtmyer Meshkov Instability. 16th International Workshop on the Physics of Compressible Turbulent Mixing. Marseille, France.