Dr. Javier Urzay was a Sr. Research Aerospace Engineer at the Stanford Center for Turbulence Research, where he worked for more than a decade. He was also the Associate Director of the DoE/NNSA Stanford PSAAP-III Center -- a 40+ persons team dedicated to supercomputing of laser ignition of cryogenic rocket propellants. His technical field of expertise is high-speed, chemically reacting, multi-phase turbulent flow physics and their engineering applications to aeronautics and astronautics, including rocket propulsion, supersonic combustion, and hypersonic aerothermodynamics of air and space flight systems. He taught the Stanford graduate classes ME356 Hypersonic Aerothermodynamics (he created this class), ME451C Compressible Turbulence, ME355 Compressible Flows, and ME471 Turbulent Combustion. He received his B.Sc./M.Sc. (Ingeniero Superior) degree in Mechanical Engineering in 2005 from the Carlos III University of Madrid (Spain), and his M.Sc. and Ph.D. degrees in Aerospace Engineering in 2006 and 2010 from the University of California San Diego (UCSD) working on theoretical combustion physics and fluid mechanics. At UCSD he taught the undergraduate class MAE180A Spacecraft Guidance (Astrodynamics). He is also a graduate of USAF Basic Military Training School and USAF Officer Training School. Dr. Javier Urzay is currently the Chief of the Combustion Devices Branch in the US Space Force, Rocket Propulsion Division at the Air Force Research Laboratory, Edwards AFB. Dr. Urzay is also an Air Force Reserve Commissioned Officer (Developmental Engineer), core member of the US Air Force Reserve Hypersonics Team, and is currently assigned to the Space Systems Integration Office in the USSF Space Systems Command at Los Angeles SFB, where he works on hypersonic missile defense.

Academic Appointments

Professional Education

  • Ph.D. Aerospace Engineer, University of California San Diego (UCSD), Theoretical Combustion Physics and Fluid Mechanics (Adviser: Prof. Forman Williams) (2010)
  • M.Sc. Aerospace Engineer, University of California San Diego (UCSD), Fluid Mechanics, Physical Gasdynamics and Applied Mathematics (2006)
  • B.Sc.+M.Sc. Mechanical Engineer, Carlos III University of Madrid (Spain), Fluid Mechanics, Propulsion and Energy (2005)

Current Research and Scholarly Interests

High-speed, chemically reacting, multi-phase flow physics
and their engineering applications to aeronautics and astronautics,
including rocket propulsion, supersonic combustion, and hypersonic aerothermodynamics
of air and space flight systems.

2022-23 Courses

All Publications

  • Transcritical diffuse-interface hydrodynamics of propellants in high-pressure combustors of chemical propulsion systems PROGRESS IN ENERGY AND COMBUSTION SCIENCE Jofre, L., Urzay, J. 2021; 82
  • Engineering aspects of hypersonic turbulent flows at suborbital enthalpies Annual Research Briefs, Center for Turbulence Research, Stanford University Urzay, J., Di Renzo, M. 2020: 7-32
  • Aerodynamic generation of electric fields in turbulence laden with charged inertial particles NATURE COMMUNICATIONS Di Renzo, M., Urzay, J. 2018; 9: 1676


    Self-induced electricity, including lightning, is often observed in dusty atmospheres. However, the physical mechanisms leading to this phenomenon remain elusive as they are remarkably challenging to determine due to the high complexity of the multi-phase turbulent flows involved. Using a fast multi-pole method in direct numerical simulations of homogeneous turbulence laden with hundreds of millions of inertial particles, here we show that mesoscopic electric fields can be aerodynamically created in bi-disperse suspensions of oppositely charged particles. The generation mechanism is self-regulating and relies on turbulence preferentially concentrating particles of one sign in clouds while dispersing the others more uniformly. The resulting electric field varies over much larger length scales than both the mean inter-particle spacing and the size of the smallest eddies. Scaling analyses suggest that low ambient pressures, such as those prevailing in the atmosphere of Mars, increase the dynamical relevance of this aerodynamic mechanism for electrical breakdown.

    View details for DOI 10.1038/s41467-018-03958-7

    View details for Web of Science ID 000430923500001

    View details for PubMedID 29700300

    View details for PubMedCentralID PMC5920100

  • Supersonic combustion in air-breathing propulsion systems for hypersonic flight ANNUAL REVIEW OF FLUID MECHANICS Urzay, J. 2018; 50: 593-627
  • Thermochemical effects on hypersonic shock waves interacting with weak turbulence PHYSICS OF FLUIDS Huete, C., Cuadra, A., Vera, M., Urzay, J. 2021; 33 (8)

    View details for DOI 10.1063/5.0059948

    View details for Web of Science ID 000686748400008

  • The turbulent bubble break-up cascade. Part 2. Numerical simulations of breaking waves JOURNAL OF FLUID MECHANICS Chan, W., Johnson, P. L., Moin, P., Urzay, J. 2021; 912
  • Direct numerical simulation of a hypersonic transitional boundary layer at suborbital enthalpies JOURNAL OF FLUID MECHANICS Di Renzo, M., Urzay, J. 2021; 912
  • Shock-induced heating and transition to turbulence in a hypersonic boundary layer Journal of Fluid Mechanics Fu, L., Karp, M., Bose, S., Moin, P., Urzay, J. 2021; 909: A8

    View details for DOI 10.1017/jfm.2020.935

  • Direct numerical simulation of a hypersonic transitional boundary layer at suborbital enthalpies Journal of Fluid Mechanics Di Renzo, M., Urzay, J. 2021; 912
  • HTR solver: An open-source exascale-oriented task-based multi-GPU high-order code for hypersonic aerothermodynamics Computer Physics Communications Renzo, M., Fu, L., Urzay, J. 2020; 255: 107262
  • Mitigation of turbophoresis in particle-laden turbulent channel flows by using incident electric fields PHYSICAL REVIEW FLUIDS Di Renzo, M., Johnson, P. L., Bassenne, M., Villafane, L., Urzay, J. 2019; 4 (12)
  • Birth of microbubbles in turbulent breaking waves Chan, W., Mirjalili, S., Jain, S. S., Urzay, J., Mani, A., Moin, P. AMER PHYSICAL SOC. 2019
  • A dynamic spectrally enriched subgrid-scale model for preferential concentration in particle-laden turbulence INTERNATIONAL JOURNAL OF MULTIPHASE FLOW Bassenne, M., Esmaily, M., Livescu, D., Moin, P., Urzay, J. 2019; 116: 270–80
  • The breakdown of self-similarity in electrified counterflow diffusion flames COMBUSTION AND FLAME Di Renzo, M., Pascazio, G., Urzay, J. 2019; 205: 231–40
  • Wavelet multiresolution analysis of particle-laden turbulence PHYSICAL REVIEW FLUIDS Bassenne, M., Moin, P., Urzay, J. 2018; 3 (8)
  • The effects of incident electric fields on counterflow diffusion flames COMBUSTION AND FLAME Di Renzo, M., Urzay, J., De Palma, P., de Tullio, M. D., Pascazio, G. 2018; 193: 177–91
  • Spatially localized multi-scale energy transfer in turbulent premixed combustion JOURNAL OF FLUID MECHANICS Kim, J., Bassenne, M., Towery, C. Z., Hamlington, P. E., Polunenko, A. Y., Urzay, J. 2018; 848: 78–116
  • Aerodynamic Heating in Wall-Modeled Large-Eddy Simulation of High-Speed Flows AIAA JOURNAL Yang, X. A., Urzay, J., Bose, S., Moin, P. 2018; 56 (2): 731–42

    View details for DOI 10.2514/1.J056240

    View details for Web of Science ID 000423512500022

  • Multi-scale statistics of turbulence motorized by active matter JOURNAL OF FLUID MECHANICS Urzay, J., Doostmohammadi, A., Yeomans, J. M. 2017; 822: 762–73
  • Extraction of coherent clusters and grid adaptation in particle-laden turbulence using wavelet filters PHYSICAL REVIEW FLUIDS Bassenne, M., Urzay, J., Schneider, K., Moin, P. 2017; 2 (5)
  • A simple dynamic subgrid-scale model for LES of particle-laden turbulence PHYSICAL REVIEW FLUIDS Park, G., Bassenne, M., Urzay, J., Moin, P. 2017; 2 (4)
  • The cross-scale physical-space transfer of kinetic energy in turbulent premixed flames PROCEEDINGS OF THE COMBUSTION INSTITUTE O'Brien, J., Towery, C. A., Hamlington, P. E., Ihme, M., Poludnenko, A. Y., Urzay, J. 2017; 36 (2): 1967-1975
  • Spectral kinetic energy transfer in turbulent premixed reacting flows PHYSICAL REVIEW E Towery, C. A., Poludnenko, A. Y., Urzay, J., O'Brien, J., Ihme, M., Hamlington, P. E. 2016; 93 (5)


    Spectral kinetic energy transfer by advective processes in turbulent premixed reacting flows is examined using data from a direct numerical simulation of a statistically planar turbulent premixed flame. Two-dimensional turbulence kinetic-energy spectra conditioned on the planar-averaged reactant mass fraction are computed through the flame brush and variations in the spectra are connected to terms in the spectral kinetic energy transport equation. Conditional kinetic energy spectra show that turbulent small-scale motions are suppressed in the burnt combustion products, while the energy content of the mean flow increases. An analysis of spectral kinetic energy transfer further indicates that, contrary to the net down-scale transfer of energy found in the unburnt reactants, advective processes transfer energy from small to large scales in the flame brush close to the products. Triadic interactions calculated through the flame brush show that this net up-scale transfer of energy occurs primarily at spatial scales near the laminar flame thermal width. The present results thus indicate that advective processes in premixed reacting flows contribute to energy backscatter near the scale of the flame.

    View details for DOI 10.1103/PhysRevE.93.053115

    View details for Web of Science ID 000376644900015

    View details for PubMedID 27300986

  • Constant-energetics physical-space forcing methods for improved convergence to homogeneous-isotropic turbulence with application to particle-laden flows PHYSICS OF FLUIDS Bassenne, M., Urzay, J., Park, G. I., Moin, P. 2016; 28 (3)

    View details for DOI 10.1063/1.4944629

    View details for Web of Science ID 000373600600053

  • Weak-Shock Interactions with Transonic Laminar Mixing Layers of Fuels for High-Speed Propulsion AIAA JOURNAL Huete, C., Urzay, J., Sanchez, A. L., Williams, F. A. 2016; 54 (3): 962–75

    View details for DOI 10.2514/1.J054419

    View details for Web of Science ID 000375425800013

  • Diffusion-flame ignition by shock-wave impingement on a supersonic mixing layer JOURNAL OF FLUID MECHANICS Huete, C., Sanchez, A. L., Williams, F. A., Urzay, J. 2015; 784: 74–108
  • Computational hydrodynamics and optical performance of inductively-coupled plasma adaptive lenses PHYSICS OF PLASMAS Mortazavi, M., Urzay, J., Mani, A. 2015; 22 (6)

    View details for DOI 10.1063/1.4922477

    View details for Web of Science ID 000357689500012

  • The role of separation of scales in the description of spray combustion PROCEEDINGS OF THE COMBUSTION INSTITUTE Sanchez, A. L., Urzay, J., Linan, A. 2015; 35: 1549–77
  • Turbulence-induced resonance vibrations cause pollen release in wind-pollinated Plantago lanceolata L. (Plantaginaceae) JOURNAL OF THE ROYAL SOCIETY INTERFACE Timerman, D., Greene, D. F., Urzay, J., Ackerman, J. D. 2014; 11 (101)


    In wind pollination, the release of pollen from anthers into airflows determines the quantity and timing of pollen available for pollination. Despite the ecological and evolutionary importance of pollen release, wind-stamen interactions are poorly understood, as are the specific forces that deliver pollen grains into airflows. We present empirical evidence that atmospheric turbulence acts directly on stamens in the cosmopolitan, wind-pollinated weed, Plantago lanceolata, causing resonant vibrations that release episodic bursts of pollen grains. In laboratory experiments, we show that stamens have mechanical properties corresponding to theoretically predicted ranges for turbulence-driven resonant vibrations. The mechanical excitation of stamens at their characteristic resonance frequency caused them to resonate, shedding pollen vigorously. The characteristic natural frequency of the stamens increased over time with each shedding episode due to the reduction in anther mass, which increased the mechanical energy required to trigger subsequent episodes. Field observations of a natural population under turbulent wind conditions were consistent with these laboratory results and demonstrated that pollen is released from resonating stamens excited by small eddies whose turnover periods are similar to the characteristic resonance frequency measured in the laboratory. Turbulence-driven vibration of stamens at resonance may be a primary mechanism for pollen shedding in wind-pollinated angiosperms. The capacity to release pollen in wind can be viewed as a primary factor distinguishing animal- from wind-pollinated plants, and selection on traits such as the damping ratio and flexural rigidity may be of consequence in evolutionary transitions between pollination systems.

    View details for DOI 10.1098/rsif.2014.0866

    View details for Web of Science ID 000343672800012

    View details for PubMedID 25297315

    View details for PubMedCentralID PMC4223907

  • A spinning puzzle of the release of a giant multinucleate multiflagellate zoospore. Urzay, J., Ott, D., Prakash, M. AMER SOC CELL BIOLOGY. 2014
  • Subgrid-scale backscatter in reacting and inert supersonic hydrogen-air turbulent mixing layers JOURNAL OF FLUID MECHANICS O'Brien, J., Urzay, J., Ihme, M., Moin, P., Saghafian, A. 2014; 743: 554-584
  • Uncertainty-quantification analysis of the effects of residual impurities on hydrogen-oxygen ignition in shock tubes COMBUSTION AND FLAME Urzay, J., Kseib, N., Davidson, D. F., Iaccarino, G., Hanson, R. K. 2014; 161 (1): 1-15
  • Dynamics of thermal ignition of spray flames in mixing layers JOURNAL OF FLUID MECHANICS Martinez-Ruiz, D., Urzay, J., Sanches, A. L., Linan, A., Williams, F. A. 2013; 734: 387–423
  • Theory of the propagation dynamics of spiral edges of diffusion flames in von Karman swirling flows COMBUSTION AND FLAME Urzay, J., Nayagam, V., Williams, F. A. 2011; 158 (2): 255–72
  • Asymptotic theory of the elastohydrodynamic adhesion and gliding motion of a solid particle over soft and sticky substrates at low Reynolds numbers JOURNAL OF FLUID MECHANICS Urzay, J. 2010; 653: 391–429
  • Wind gusts and plant aeroelasticity effects on the aerodynamics of pollen shedding: A hypothetical turbulence-initiated wind-pollination mechanism JOURNAL OF THEORETICAL BIOLOGY Urzay, J., Smith, S., Thompson, E., Glover, B. J. 2009; 259 (4): 785–92


    Plant reproduction depends on pollen dispersal. For anemophilous (wind-pollinated) species, such as grasses and many trees, shedding pollen from the anther must be accomplished by physical mechanisms. The unknown nature of this process has led to its description as the 'paradox of pollen liberation'. A simple scaling analysis, supported by experimental measurements on typical wind-pollinated plant species, is used to estimate the suitability of previous resolutions of this paradox based on wind-gust aerodynamic models of fungal-spore liberation. According to this scaling analysis, the steady Stokes drag force is found to be large enough to liberate anemophilous pollen grains, and unsteady boundary-layer forces produced by wind gusts are found to be mostly ineffective since the ratio of the characteristic viscous time scale to the inertial time scale of acceleration of the wind stream is a small parameter for typical anemophilous species. A hypothetical model of a stochastic aeroelastic mechanism, initiated by the atmospheric turbulence typical of the micrometeorological conditions in the vicinity of the plant, is proposed to contribute to wind pollination.

    View details for DOI 10.1016/j.jtbi.2009.04.027

    View details for Web of Science ID 000274798100012

    View details for PubMedID 19445957

  • Diffusion-flame extinction on a rotating porous-disk burner PROCEEDINGS OF THE COMBUSTION INSTITUTE Urzay, J., Nayagam, V., Williams, F. A. 2009; 32: 1219–26
  • The elastohydrodynamic force on a sphere near a soft wall PHYSICS OF FLUIDS Urzay, J., Smith, S., Glover, B. J. 2007; 19 (10)

    View details for DOI 10.1063/1.2799148

    View details for Web of Science ID 000250589600024