Showing papers on "Supersonic speed published in 1997"
TL;DR: Schlieren et al. as mentioned in this paper presented a quantitative, experimental study of a single, sonic, underexpanded, transverse, round jet injected into a Mach 1.6 mainframe.
Abstract: This paper presents a quantitative, experimental study of a single, sonic, underexpanded, transverse, round jet injected into a Mach 1.6 crosse ow. This investigation is applicable to studies of supersonic combustors, thrust vector control of rocket nozzles, the cooling of nozzle walls, and jet reaction force prediction. Schlieren/shadowgraph photography and two-component, frequency preshifted laser Doppler velocimetry are used to visualize the e ow and to measure three mean velocity components, e ve of the six kinematic Reynolds stresses, and turbulent kinetic energy at over 4000 locations throughout the e owe eld. The study focuses on the transverse, midline plane and on two crosse ow planes. These measurements are used to study the size and orientation of the recirculation regions upstream and downstream of the jet; the structure and strength of the bow shock, barrel shock, and Mach disk; the structure, strength, and development of the kidney-shaped, counter-rotating vortex pair; the growth of the annular shear layer between the jet plume and the crosse ow; and the growth of the boundary layer beneath the jet. In addition, the present study provides validation data for analytical and numerical predictions of the transverse jet e owe eld.
217 citations
TL;DR: In this article, the effects of compressibility on the large-scale structural development and near-field mixing characteristics of transverse injection of sonic gaseous jets through a circular nozzle into a supersonic crossflow have been experimentally investigated using planar Rayleigh/Mie scattering from silicon dioxide particles seeded into the crossflow stream.
Abstract: The flowfields created by transverse injection of sonic gaseous jets through a circular nozzle into a supersonic crossflow have been experimentally investigated using planar Rayleigh/Mie scattering from silicon dioxide particles seeded into the crossflow stream. Helium and air were used as injectant gases allowing an examination of the effects of compressibility on the large-scale structural development and near-field mixing characteristics present within the flowfield. Instantaneous images from end and side view image planes show a highly three-dimensional interaction dominated by both large- and small-scale vortices. Analyses of these image ensembles provide jet spreading and penetration characteristics, standard deviation statistics, large-scale mixing information, and two-dimensional spatial correlation fields. Results indicate that injectant molecular weight variations do not strongly affect the jet’s transverse penetration into the crossflow, although they lead to substantially different compressibi...
147 citations
TL;DR: In this article, a method that eliminates Mach waves from the exhaust of supersonic jets was proposed to increase takeoff thrust with minimal impact on overall fuel consumption by surrounding the jet with an annular stream.
Abstract: Experimental results are presented on a method that eliminates Mach waves from the exhaust of supersonic jets and, hence, that removes a strong component of supersonic jet noise. Elimination is achieved by surrounding the jet with an annular stream at prescribed velocity and temperature so that all turbulent motions become intrinsically subsonic. No mechanical suppressors are used. Implementation of the technique in a typical turbofan engine is estimated to increase takeoff thrust with minimal impact on overall fuel consumption.
94 citations
TL;DR: In this article, the evolution of large turbulent eddies has been investigated in seven supersonic shear layers with average convective Mach numbers ranging from 0.22 to 0.86 and with large variation in density and velocity ratios.
Abstract: The evolution of large turbulent eddies has been investigated in seven supersonic shear layers with average convective Mach numbers Mc¯ ranging from 0.22 to 0.86 and with large variation in density and velocity ratios. A two-laser, single-detector planar laser-induced fluorescence technique was used to visualize the flow and its evolution. Two-dimensional pattern matching yielded the convective velocity of the eddies. For Mc¯>0.3, fast and slow modes of eddy propagation were detected in supersonic–subsonic and supersonic–supersonic combinations, respectively. An empirical model for the convective velocity is proposed. Plan views reveal coexistence of two- and three-dimensional disturbances. Interaction among eddies appears significantly suppressed. The findings have direct impact on supersonic jet noise and are very relevant to supersonic combustion.
93 citations
29 Jun 1997
TL;DR: In this paper, the authors considered three gas models: perfect gas, chemical equilibrium and non-equilibrium (finite-rate chemistry) for a Mach-20 flow past a 6° wedge.
Abstract: Linear stability of reacting flows in hypersonic boundary layers is studied via the parabolized stability equations (PSE) method. Three gas models are considered in the basic flow as well as stability calculations: perfect gas, chemical equilibrium and non-equilibrium (finite-rate chemistry). The finite-rate chemistry model for air contains five species, eight reactants and six reactions. The equilibrium calculation is performed by a table look-up procedure. Amplifying supersonic modes characterized by an oscillating disturbance structure outside the boundary-layer and a relative phase velocity faster than the free-stream sonic speed were found to appear in a Mach-20 flow past a 6° wedge when either equilibrium or finite-rate chemistry model is incorporated. These supersonic modes emerge just downstream of the unstable subsonic second-mode region and they propagate into the free-stream with a phase speed different from the corresponding acoustic wave and decay at a finite distance outside the boundary layer. The Rankine-Hugoniot (shock) conditions applied at the shock have very little effect on the supersonic modes studied here since the mode structure decays before the shock is reached. Due to the presence of supersonic modes, which are enhanced by the chemistry effect, the transition onset (based on N = 10) for the Mach-20 wedge flow is estimated to be at 14 ft, 24ft and 39 ft if one uses equilibrium, non-equilibrium and perfect gas models, respectively. It is therefore very important to account for the chemistry effect in future transition prediction for hypersonic vehicles.
89 citations
TL;DR: In this article, a computational approach to the prediction of jet mixing noise is described based on Lighthill's analogy, used together with a semi-deterministic modelling of turbulence (SDM), where only the large-scale coherent motion is evaluated.
Abstract: A computational approach to the prediction of jet mixing noise is described. It is based on Lighthill's analogy, used together with a semi-deterministic modelling of turbulence (SDM), where only the large-scale coherent motion is evaluated. The features of SDM are briefly illustrated in the case of shear layers, showing that suitable descriptions of the mean flow and of the large-scale fluctuations are obtained. Aerodynamic calculations of two cold fully expanded plane jets at Mach numbers 0.50 and 1.33 are then carried out. The numerical implementation of Lighthill's analogy is described and different integral formulations are compared for the two jets. It is shown that the one expressed in a space-time conjugate (κ, ω)-plane is particularly convenient and allows a simple geometrical interpretation of the computations. Acoustic results obtained with this formulation are compared to relevant experimental data. It is concluded that the radiation of subsonic jets cannot be explained only by the contribution of the turbulent coherent motion. In this case, directivity effects are well recovered but the acoustic spectra are too narrow and limited to the low-frequency range. In contrast at Mach number 1.33, especially in the forward quadrant, results are satisfactory, showing that coherent structures indeed provide the main source of supersonic jet mixing noise.
86 citations
TL;DR: In this article, a tetrahedron-based, h-refinement-type algorithm for the solution of problems in 3D gas dynamics using unstructured mesh adaptation is presented.
Abstract: SUMMARY In this paper we present a tetrahedron-based, h-refinement-type algorithm for the solution of problems in 3D gas dynamics using unstructured mesh adaptation. The mesh adaptation algorithm is coupled to a cell-centred, Riemann problem-based, finite volume scheme of the MUSCL type, employing an approximate Riemann solver. The adaptive scheme is then used to compute the diffraction of shock waves around a box section corner for subsonic and supersonic post-shock flow. In the subsonic case, preliminary measurements of vortex filament speed and vortical Mach number are in broad quantitative agreement with known theoretical results. # 1997 by John Wiley & Sons, Ltd.
86 citations
TL;DR: A unified hypersonic - supersonic lifting surface method has been developed, where the concept of piston theory is generalized and suitably integrated with the aerodynamic influence coefficient (AIC) matrix due to linear theory as mentioned in this paper.
Abstract: A unified hypersonic - supersonic lifting surface method has been developed, where the concept of piston theory is generalized and suitably integrated with the aerodynamic influence coefficient (AIC) matrix due to linear theory. Thus, this unified method can account for the effects of wing thickness and/or flow incidence, upstream influence, and three dimensionality for an arbitrary lifting surface system in an unsteady flow, whereas piston theory fails to account for the latter effects. In particular, the present composite series renders the AIC matrix uniformly valid for all supersonic-hypersonic Mach numbers, thus extending the method applicability to cover both the Ackeret limit at the low supersonic end and the Newtonian limit at the hypersonic end. From various cases studied it is concluded that the present method makes a substantial improvement over the linear lifting surface theory and piston theory in terms of unsteady pressures, stability derivatives, and flutter speeds. Among other theories it also predicts the most conservative flutter boundary and it confirms that the supersonic thickness effect is to reduce the flutter speed.
82 citations
Patent•
27 Oct 1997
TL;DR: In this paper, a supersonic manifold is used to accelerate a compressed air source to a speed of several hundred meters per second by passing the compressed air through a powder feeder.
Abstract: The apparatus is comprised of a compressed air source which is connected by a gas conduit to a heating unit whose outlet is connected to a supersonic nozzle inlet in which a supersonic portion is connected by a conduit to a powder feeder. Compressed air of pressure P0 from the compressed air source by the gas conduit is delivered to the heating unit to be heated to the required temperature. The heated air enters the supersonic nozzle in which it is accelerated to a speed of several hundred meters per second. The powdered material is passed from the powder feeder by the powder feeding conduit to the supersonic nozzle portion in which it is accelerated by the air flow at section of the nozzle from the injection point to the nozzle outlet.
76 citations
TL;DR: In this paper, a combination of a k-≤ turbulence closure with an acoustic analogy provides an interesting way to compute such radiated acoustic e elds, and the last two models yield improved supersonic jet mixing noise predictions.
Abstract: Subsonicandsupersonicjetnoiseisdeterminednumerically from statisticalsourcemodels.Thegoalistodevelop prediction methods for high-speed jet noise for application to aeronautical and space transportation systems. In this framework, a combination of a k-≤ turbulence closure with an acoustic analogy provides an interesting way to compute such radiated acoustic e elds. Three acoustic analogies are investigated. First, the classical Lighthill theory in combination with Ribner' s results is applied to calculate jet mixing noise. The second method relies on the Goldstein -Howes convected wave equation, which is used to improve the predicted supersonic jet mixing noise in the upstream direction. It is necessary to properly account for acoustic wave convection, and then, one e nds that the Doppler factor features an exponent of i 3 in the associated power law. A model based on the Ffowcs Williams-MaidanikanalysisthenisdevelopedtoestimatetheMach-wavenoisecomponentthatdominatesforward arc radiation when theconvection Mach number is supersonic. Comparisons between aerodynamicand calculated acoustic results on the one hand, and available measurements on the other hand, are carried out. It is shown that the last two models yield improved supersonic jet mixing noise predictions.
74 citations
TL;DR: In this article, the formation of the liquid phase is modelled using the classical nucleation theory for the steady state together with the Hertz-Knudsen droplet growth law and yields qualitatively and quantitatively excellent agreement with experiments in the unsteady flow regime with high-frequency oscillations including the unstable transient change of the structure from symmetric to unsymmetric flow.
Abstract: New instabilites of unsteady transonic flows with non-equilibrium phase transition are presented including unsymmetric flow patterns with moving oblique shock systems in supersonic nozzles with perfectly symmetric shapes. The phenomena were first detected when performing experiments in our supersonic wind tunnel with atmospheric supply and could be perfectly reproduced by numerical simulations based on the Euler equations, i.e. neglecting the viscosity of the fluid. The formation of the liquid phase is modelled using the classical nucleation theory for the steady state together with the Hertz-Knudsen droplet growth law and yields qualitatively and quantitatively excellent agreement with experiments in the unsteady flow regime with high-frequency oscillations including the unstable transient change of the structure from symmetric to unsymmetric flow. For engineering applications the sudden increase or decrease of the frequency by a factor 2 or more and of the pressure amplitude at the bifurcation limits is of immediate practical interest, e.g. for flutter excitation of turbomachinery blading.
TL;DR: In this paper, the aerodynamic properties of the Earth entry vehicle were analyzed in the free-molecular and early transitional flow regime, and the aerodynamics across the hypersonic regime were compared with the Newtonian flow approximation and a correlation between the accuracy of the Newtonian flow assumption and the sonic line position.
Abstract: Successful return of interstellar dust and cometary material by the Stardust Sample Return Capsule requires an accurate description of the Earth entry vehicle''s aerodynamics. This desciption must span the hypersonic-rarefied, hypersonic-continuum, supersonic, transonic, and subsonic flow regimes. Data from numerous sources are compiled to accomplish this objective. These include Direct Simulation Monte Carlo analyses, thermochemical nonequilibrium computational fluid dynamics, transonic computational fluid dynamics, existing wind tunnel data, and new wind tunnel data. Four observations are highlighted: 1) a static instability is revealed in the free-molecular and early transitional-flow regime due to aft location of the vehicle''s center-of-gravity, 2) the aerodynamics across the hypersonic regime are compared with the Newtonian flow approximation and a correlation between the accuracy of the Newtonian flow assumption and the sonic line position is noted, 3) the primary effect of shape change due to ablation is shown to be a reduction in drag, and 4) a subsonic dynamic instability is revealed which will necessitate either a change in the vehicle''s center-of-gravity location or the use of a stabilizing drogue parachute.
TL;DR: In this paper, it is shown that linear stability theory can be used to specify the source terms in Lighthill's equation; the resulting predictions are also in good agreement with the direct computations.
Abstract: The intense Mach waves radiated by the growth and decay of linear instability waves in the shear layer of a perfectly expanded, axisymmetric jet with an initial centerline Mach number of Mj = 2.0 are directly computed by solution of the compressible Navier-Stokes equations on a computational domain that includes both the near and far fields. The directly computed far-field sound is compared to predictions obtained using an analysis based on linear stability theory, Lighthill's equation, and the Kirchhoff surface method. All of the predictions are in good agreement with the direct computations. Using Lighthill's equation, we demonstrate that it is essential to properly address the acoustical noncompactness of the sources. It is also shown that linear stability theory can be used to specify the source terms in Lighthill's equation; the resulting predictions are also in good agreement with the computations.
TL;DR: In this article, a new method for the design of a supersonic nozzle tip for high gas pressure laser cutting is presented based on the theory of gas dynamics in that the potential energy of high stagnation pressure is converted totally into effective velocity energy so that a high momentum of the exit jet can be obtained.
TL;DR: In this paper, the steady, inviscid, supersonic flow of Bethe-Zel'dovich-Thompson (BZT) fluids in two-dimensional cascade configurations was examined.
Abstract: We examine the steady, inviscid, supersonic flow of Bethe-Zel'dovich-Thompson (BZT) fluids in two-dimensional cascade configurations. Bethe-Zel'dovich-Thompson fluids are single-phase gases having specific heats so large that the fundamental derivative of gasdynamics is negative over a finite range of pressures and temperatures. The equation of state is the well-known Martin-Hou equation, and the numerical scheme is the explicit predictor-corrector method of MacCormack. Numerical comparisons between BZT fluids and lighter fluids such as steam are presented. It was found that the natural dynamics of BZT fluids can result in significant reductions in the adverse pressure gradients associated with the collision of compression waves with neighboring turbine blades. A numerical example of an entirely isentropic supersonic cascade flow is also presented.
TL;DR: In this paper, the authors presented a simple formulation based on the acoustic analogy that is valid for both subsonic and supersonic quadrupole noise prediction for high speed helicopter rotor impulsive noise.
TL;DR: In this paper, a uniform supersonic flow of a rarefied gas past a flat plate at zero angle of attack is considered, and the steady behavior of the gas around the plate is investigated numerically on the basis of the Boltzmann-Krook-Welander equation and the diffuse reflection boundary condition.
Abstract: A uniform supersonic flow of a rarefied gas past a flat plate at zero angle of attack is considered, and the steady behavior of the gas around the plate is investigated numerically on the basis of the Boltzmann–Krook–Welander equation (or the so-called BGK model) and the diffuse reflection boundary condition. An accurate finite-difference analysis, which gives the correct description of the discontinuity of the velocity distribution function of the gas molecules occurring in the gas, is carried out, and the features of the flow field (the velocity distribution function and the macroscopic variables such as the density, temperature, and flow velocity of the gas), in particular, those around the leading and trailing edges, are clarified for a wide range of the Knudsen number. The drag acting on the plate and the energy transferred to it are also obtained accurately. In addition, on the basis of the results for small Knudsen numbers, the behavior of the gas around the leading edge of a semi-infinite plate is...
06 Jul 1997
TL;DR: In this paper, numerical simulations of several turbulent supersonic flows related to scramjet combustors are carried out using a new unified-grid computational methodology using the Reynoldsaveraged Navier-Stokes equations along with oneequation and three-equation pointwise turbulence models.
Abstract: Numerical simulations of several turbulent supersonic flows related to scramjet combustors are carried out using a new unified-grid computational methodology. Five problems are considered: a 2-D ramp unit problem; a reattaching turbulent shear layer, the 3-D University of Virginia two-hole supersonic transverse Air-Air injector; and the NASA P2 and P8 supersonic inlets. The numerical simulations are conducted using the Reynoldsaveraged Navier-Stokes equations along with oneequation and three-equation pointwise turbulence models. Both turbulence models enable accurate prediction of the flowfields and numerical results compare favorably with experimental data in all cases.
TL;DR: A multilevel design strategy for supersonic missile inlet design is developed that combines an efe cient simple physical model analysis tool and a sophisticated computational computational dynamics (CFD) Navier ‐ Stokes analysis tool.
Abstract: A multilevel design strategy for supersonic missile inlet design is developed. The multilevel design strategy combines an efe cient simple physical model analysis tool and a sophisticated computational e uid dynamics (CFD) Navier ‐ Stokes analysis tool. The efe cient simple analysis tool is incorporated into the optimization loop, and the sophisticated CFD analysis tool is used to verify, select, and e lter the e nal design. The genetic algorithms and multistart gradient line search optimizers are used to search the nonsmooth design space. A geometry model for the supersonic missile inlet is developed. A supersonic missile inlet that starts at Mach 2.6 and cruises at Mach 4 was designed. Signie cant improvement of the inlet total pressure recovery has been obtained. Detailed e owe eld analysis is also presented.
TL;DR: In this article, it was shown that freestream noise is the mechanism that drives resonant pressure oscillations within relatively shallow cavities and that the sensitivity of cavity ampliµ cation, i.e., the relative strength of resonance oscillations, to the characteristics of free-streamnoise (frequency, amplitude,perturbation variable), cavitygeometry (depth, geometric scale, lip radius), Mach number, viscous effects, and thermal wall boundary condition is studied.
Abstract: Hypersonic ow over the nose of a blunt body with a forward-facing cylindrical cavity is studied. Extensive numerical results involvinga wide range of cavity depths are veri ed by experimental runs including a new set of runs performed in a quiet ow supersonic tunnel at Mach 4. It is shown that freestream noise is the mechanism that drives resonant pressure oscillations within relatively shallow cavities. Numerical results and conventional tunnel experiments show that deeper cavities oscillate strongly without freestream noise. For shallow cavities the sensitivity of cavity ampli cation, i.e., the relative strength of resonant pressure oscillations, to the characteristics of freestreamnoise (frequency, amplitude,perturbationvariable), cavitygeometry (depth, geometric scale, lip radius), Mach number, viscous effects, and thermal wall boundary condition is studied. There is a strong dependence of oscillation strength on freestream noise frequency. Oscillation strength increases nearly proportionally to input noise amplitude, increases rapidly with cavity depth, and increases with Mach number but levels off at highMach numbers. The pressure oscillations exhibit behavior analogous to that of a damped harmonic oscillator.
TL;DR: In this article, a multigrid convergence acceleration technique has been developed for solving both the Navier-Stokes and turbulence transport equations, and several ramped duct test cases are presented to demonstrate the improvements in performance of the numerical scheme.
Abstract: A multigrid convergence acceleration technique has been developed for solving both the Navier-Stokes and turbulence transport equations. For turbulence closure a low-Reynolds-number q-ω turbulence model is employed. To enable convergence, the stiff non-linear turbulent source terms have to be treated in a special way. Further modifications to standard multigrid methods are necessary for the resolution of shock waves in supersonic flows. An implicit LU algorithm is used for numerical time integration. Several ramped duct test cases are presented to demonstrate the improvements in performance of the numerical scheme. Cases with strong shock waves and separation are included. It is shown to be very effective to treat fluid and turbulence equations with the multigrid method.
01 Jan 1997
TL;DR: In this paper, the influence of forward flight on the far-field noise of an underexpanded heated supersonic jet has been studied experimentally with a 12.5 cm-diam convergent nozzle operated in the NASA Ames Research Center 12.2 x 24.4 m (40 x 80 ft) wind tunnel.
Abstract: The influence of forward flight on the far-field noise of an underexpanded heated supersonic jet has been studied experimentally with a 12.5-cm-diam convergent nozzle operated in the NASA Ames Research Center 12.2 x 24.4 m (40 x 80 ft) wind tunnel. The nozzle was operated at nozzle pressure ratios up to 4.5 and stagnation temperature ratios from 2.45 to 3.45. The resulting velocity (based on fully expanded condition) range is from 586 to 858 m/s. The freestream Mach number was varied from 0 to 0.32. Far-field narrow band spectra were obtained at angles (measured from the inlet axis) covering a range from 30 to 155 deg. A small amplification of the overall sound-pressure level (2 dB) due to forward flight is observed in the forward quadrant. The mixing noise reduction in the aft quadrant due to forward flight is much smaller than that observed in corresponding cold jets.
TL;DR: In this article, a basic theory is developed to explain the transition from bubbling to jetting, and the instability of a circular compressible gas jet in a liquid was studied.
TL;DR: In this article, the authors analyzed the ignition evolution in a supersonic non-premixed hydrogen/air laminar mixing layer, consisting of a relatively hot, fast air stream next to a cold, slower hydrogen stream, compared with results from asymptotic analysis with reduced mechanisms.
TL;DR: In this article, a new axisymmetric throughflow method for analyzing and designing turbomachines is proposed, which utilizes body-force terms to represent blade forces and viscous losses.
Abstract: A new axisymmetric throughflow method for analyzing and designing turbomachines is proposed. This method utilizes body-force terms to represent blade forces and viscous losses. The resulting equations of motion, which include these bod-force terms, are cast in terms of conservative variables and are solved using a finite-volume time-stepping scheme. In the inverse mode, the swril schedule in the bladed regions (i.e., the radius times the tangential velocity rV O ) is the primary specified flow quantity, and the corresponding blade shape is sought after. In the analysis mode, the blade geometry is specified and the flow solution is computed. The advantages of this throughflow method compared to the current family of streamline curvature and matrix methods are that the same code can be used for subsonic/transonic/supersonic throughflow velocities, and the proposed method has a shock capturing capability. This method is demonstrated for designing a supersonic throughflow fan stage and a transonic throughflow turbine stage.
TL;DR: In this article, the selection of the unique aeroshell for the Mars Microprobes is discussed, and a description of its aerodynamics in hypersonic rarefied, hypersonIC continuum, supersonic, and transonic flow regimes is presented.
Abstract: The selection of the unique aeroshell for the Mars Microprobes is discussed. A description of its aerodynamics in hypersonic rarefied, hypersonic continuum, supersonic, and transonic flow regimes is then presented. This description is compiled from Direct Simulation Monte Carlo simulations, computational fluid dynamics, wind tunnel data, and ballistic range data. The aeroshell is shown to possess the correct combination of aerodynamic stability and drag to convert the probe''s initial tumbling attitude at atmospheric-interface into the desired surface-impact orientation and velocity.
06 Jan 1997
TL;DR: In this article, a new high-order upwind finite difference shock fitting method for direct simulations of hypersonic flows with strong bow shocks is presented and tested, and the results of accuracy tests of the new fifth-order shock-fitting method are presented for four test cases: 1D wave equation, 2D direct numerical simulation (DNS) of stability of supersonic Couette flow, steady viscous hyperersonic flow over a circular cylinder and the DNS of receptivity to freestream acoustic disturbances for hypersonIC boundary layers over a parabola.
Abstract: This paper presents and tests a new high-order upwind finite difference shock fitting method for the direct simulations of hypersonic flows with strong bow shocks. There are three main aspects of the new method: a simple unsteady shock fitting formulation, new upwind high-order finite difference schemes for spatial discretization, and new third-order semi-implicit Runge-Kutta schemes for temporal discretization. The results of accuracy tests of the new fifth-order shock-fitting method are presented for four test cases: 1D wave equation, 2D direct numerical simulation (DNS) of stability of supersonic Couette flow, steady viscous hypersonic flow over a circular cylinder, and the DNS of receptivity to freestream acoustic disturbances for hypersonic boundary layers over a parabola. (Author)
12 May 1997
TL;DR: In this paper, a parallel three-dimensional computational aeroacoustics method, based on large eddy simulation and a split between the mean flow and perturbations, has been developed to predict the unsteady characteristics of supersonic jet flows and their radiated noise.
Abstract: A parallel three-dimensional computational aeroacoustics method, based on large eddy simulation and a split between the mean flow and perturbations, has been developed to predict the unsteady characteristics of supersonic jet flows and their radiated noise. The instantaneous quantities are decomposed into a time-independe nt mean component, a large-scale perturbation, and a small-scale perturbation. Only the large-scale fluctuations are resolved directly while the mean quantities are obtained from a traditional Reynolds averaged method. The effects of the small-scale fluctuations are parameterized using a subgrid scale model. In order to reduce the wall-clock time for the simulations, the threedimensional code has been parallelized using a domain decomposition strategy and Message Passing Interface (MPI) routines are used to facilitate exchange of data between different processors. Results for both the flow and acoustic fields of a circular jet simulation at a nozzle exit Mach number of 2.1 are presented and comparisons with several experimental measurements are made.