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High-fidelity Computational Study of High-speed Reacting Jets in Crossflow
... While low-speed jet in crossflow configurations exhibit several similar features, such as horseshoe, shear-layer, and counter-rotating vortex pairs [1,2], other features, such as bow and separation shocks upstream of the injection point, are unique to supersonic flows. In the past, JISCs with gaseous injection have been studied more extensively both experimentally [6][7][8][9] and computationally [10][11][12][13]. However, several have also considered liquid injection [14][15][16][17], which introduces additional multi-scale phenomena such as fuel atomization and evaporation. ...
... To date, computational studies of reacting JISC have primarily considered gaseous jets-typically hydrogen [11][12][13] or ethylene [10,51]. Simulations of liquid JISC have been predominantly conducted with water [47,52,53], as have experiments [16,17,34,[54][55][56]. ...
... ρE = ρ l α l e l + ρ g α g e g + 1 2 ρu i u i (10) In these equations, the mixture density (ρ), viscosity (µ), and thermal conductivity (λ) are computed using volumetric mixture rules with components from each phase. The chemical source term for the k-th species,Ω k , is only integrated where the gas phase is dominant-i.e., where α l < α min . ...
Canonical jet in supersonic crossflow studies have been widely used to study fundamental physics relevant to a variety of applications. While most JISC works have considered gaseous injection, liquid injection is also of practical interest and introduces additional multiscale physics, such as atomization and evaporation, that complicate the flow dynamics. To facilitate further understanding of these complex phenomena, this work presents multiphase simulations of reacting and non-reacting JISC configurations with freestream Mach numbers of roughly 4.5. Adaptive mesh refinement is used with a volume of fluid scheme to capture liquid breakup and turbulent mixing at high resolution. The results compare the effects of the jet momentum ratio and freestream temperature on jet penetration, mixing, and combustion dynamics. For similar jet momentum ratios, the jet penetration and mixing characteristics are similar for the reacting and non-reacting cases. Mixing analyses reveal that vorticity and turbulent kinetic energy intensities peak in the jet shear layers, where vortex stretching is the dominant turbulence generation mechanism for all cases. Cases with lower freestream temperatures yield negligible heat release, while cases with elevated freestream temperatures exhibit chemical reactions primarily along the leading bow shock and within the boundary layer in the jet wake. The evaporative cooling quenches the chemical reactions in the primary atomization zone at the injection height, such that the flow rates of several product species plateau after x/d=20. Substantial concentrations of final product species are only observed along the bow shock-due to locally elevated temperature and pressure-and in the boundary layer far downstream-where lower flow velocities counteract the effects of prolonged ignition delays. This combination of factors leads to low combustion efficiency at the domain exit.
... All numerical simulations in this study are based on the combustion suite PeleC 22 from AMReX, 23 and the solutions are run on a heterogeneous high performance computing (HPC) cluster consisting of NVIDIA RTX3090 graphic processing units (GPUs) and Intel i7-10700 central processing units (CPUs), with up to 10 GPUs used in parallel. This suite has been extensively validated and is widely used for simulations of compressible flow, including turbulent boundary layers, 24 shock-induced boundary layer separations, 25 combustion, 22,26 and detonation, 27,28 ensuring reliable and accurate results. ...
This study investigates the mechanisms of flame acceleration and deflagration-to-detonation transition (DDT) in supersonic flows using transverse hydrogen injection and downstream ignition. Utilizing the graphics processing unit accelerated adaptive mesh refinement approach, we examine the influence of downstream ignition jet pressure on DDT through high-resolution computational simulations. Our results indicate that the transverse injection of hydrogen into the supersonic mainstream generates strong turbulence and numerous vortices due to Kelvin–Helmholtz instability, enhancing fuel mixing efficiency along the flow but deviating from the ideal premixed state. Following the injection of the downstream ignition jet into the supersonic main flow, initial flame acceleration is less effective than in the premixed state due to the non-uniformity of the incoming flow. However, within the boundary layer, the flame remains stable, and the intense turbulence fosters shock–flame interactions. The convergence of multiple compression waves into a shock wave facilitates energy deposition, coupling with the flame to trigger local detonation via the reactive gradient mechanism. The detonation wave exhibits complex wavefront structures, including vertical and oblique fronts induced by boundary layer interactions. Ignition jet pressure significantly impacts the DDT process and detonation wave characteristics, reducing ignition time and affecting the detonation temperature, pressure, and propagation speed. This study provides valuable insights into the dynamics of flame acceleration and DDT in supersonic flows with non-uniform fuel distribution and downstream jet ignition. The findings highlight the critical role of ignition jet pressure in optimizing ignition and detonation processes, offering new perspectives for achieving low-energy, rapid detonation initiation within the tube.
This paper reports on a series of large-eddy simulations of a round jet issuing normally into a crossflow. Simulations were performed at two jet-to-crossflow velocity ratios, 2.0 and 3.3, and two Reynolds numbers, 1050 and 2100, based on crossflow velocity and jet diameter. Mean and turbulent statistics computed from the simulations match experimental measurements reasonably well. Large-scale coherent structures observed in experimental flow visualizations are reproduced by the simulations, and the mechanisms by which these structures form are described. The effects of coherent structures upon the evolution of mean velocities, resolved Reynolds stresses, and turbulent kinetic energy along the centreplane are discussed. In this paper, the ubiquitous far-field counter-rotating vortex pair is shown to originate from a pair of quasi-steady `hanging' vortices. These vortices form in the skewed mixing layer that develops between jet and crossflow fluid on the lateral edges of the jet. Axial flow through the hanging vortex transports vortical fluid from the near-wall boundary layer of the incoming pipe flow to the back side of the jet. There, the hanging vortex encounters an adverse pressure gradient and breaks down. As this breakdown occurs, the vortex diameter expands dramatically, and a weak counter-rotating vortex pair is formed that is aligned with the jet trajectory.
A three-dimensional unsteady reacting flowfield that is generated by transverse hydrogen injection into a supersonic mainstream is numerically investigated using detached-eddy simulation and a finite-rate chemistry model. Grid refinement with the grid-convergence-index concept is applied to the instantaneous flowfield for assessing the grid resolution and solution convergence. Validation is performed for the jet penetration height, and the predicted result is in good agreement with experimental trends. The results indicate that jet vortical structures are generated as the interacting counter-rotating vortices become alternately detached in the upstream recirculation region. Although the numerical OH distribution reproduces the experimental OH-planar-laser-induced fluorescence well, there are some disparities in the ignition delay times due to the restricted availability of experimental and numerical data. The effects of the turbulence model on combustion are identified by a comparative analysis of the Reynolds-averaged Navier-Stokes and detached-eddy simulation approaches. Their effects are quantified by the production of H(2)O, Which is the primary species of hydrogen combustion.
We report an experimental investigation that reveals significant differences in the near-flowfield properties of hydrogen and ethylene jets injected into a supersonic crossflow at a similar jet-to-freestream momentum flux ratio. Previously, the momentum flux ratio was found to be the main controlling parameter of the jet's penetration. Current experiments, however, demonstrate that the transverse penetration of the ethylene jet was altered, penetrating deeper into the freestream than the hydrogen jet even for similar jet-to-freestream momentum flux ratios. Increased penetration depths of ethylene jets were attributed to the significant differences in the development of large-scale coherent structures present in the jet shear layer. In the hydrogen case, the periodically formed eddies persist long distances downstream, while for ethylene injection, these eddies lose their coherence as the jet bends downstream. The large velocity difference between the ethylene jet and the freestream induces enhanced mixing at the jet shear layer as a result of the velocity induced stretching-tilting-tearing mechanism. These new observations became possible by the realization of high velocity and high temperature freestream conditions which could not be achieved in conventional facilities as have been widely used in previous studies. The freestream flow replicates a realistic supersonic combustor environment associated with a hypersonic airbreathing engine flying at Mach 10. The temporal evolution, the penetration, and the convection characteristics of both jets were observed using a fast-framing-rate up to 100 MHz camera acquiring eight consecutive schlieren images, while OH planar laser-induced fluorescence was performed to verify the molecular mixing. © 2006 American Institute of Physics.
Experimental results on the mixing of non-aerated and aerated transverse liquid jet in supersonic cross flow (M=1.5) are presented in this paper. The goal of this study is to investigate the effect of the gas/liquid mass ratio on the
penetration and atomization of an aerated liquid jet in high speed cross flow and to develop correlations for the penetration
heights. High speed imaging system was used in this study for the visualization of the injection of aerated liquid jet. The
results show the effect of jet/cross flow momentum flux ratio, the gas/liquid mass ratio and the Ohnesorge number on the penetration
of aerated liquid jet in supersonic cross-flow. New correlations of the spray penetration height for the non-aerated liquid
jet (GLR=0) and the net gain in spray penetration height for the aerated liquid jet (GLR>0) are presented.
In this paper we further explore a class of high order Total Variation Diminishing (TVD) Runge-Kutta time discretization initialized in Shu & Osher (1988), suitable for solving hyperbolic conservation laws with stable spatial discretizations. We illustrate with numerical examples that non-TVD but linearly stable Runge-Kutta time discretization can generate oscillations even for TVD spatial discretization, verifying the claim that TVD Runge-Kutta methods are important for such applications. We then explore the issue of optimal TVD Runge-Kutta methods for second, third and fourth order, and for low storage Runge-Kutta methods.
Effects of fuel jet penetration height on supersonic combustion behaviors were investigated experimentally in a supersonic combustion ramjet model combustor at a Mach speed of 2 and at a stagnation temperature of 1900 K. The jet-to-crossflow momentum flux ratio was varied to control the fuel-jet penetration height, using several injectors with different orifice diameters: 2, 3, and 4 mm. First, transverse nitrogen jets were observed to identify a relationship between the fuel jet penetration height and the momentum flux ratio by focusing Schlieren photography. Then, supersonic combustion behaviors of ethylene were investigated through combustion pressure measurements. Simultaneously, time-resolved images of CH* chemiluminescence and shadowgraphs were recorded with high-speed video cameras. Furthermore, a morphology of supersonic combustion modes was investigated for various equivalence ratios and fuel penetration heights in a two-dimensional latent space trained by the shared Gaussian process latent variable models (SGPLVM), considering CH* chemiluminescence images and the shock parameters. The results indicated that the penetration height of nitrogen jets was a function of the jet momentum flux ratio; this function was expressed by a fitting curve. Five typical combustion modes were identified based on time-resolved CH* chemiluminescence images, shadowgraphs, and pressure profiles. Even for a given equivalence ratio, different combustion modes were observed depending on the fuel penetration height. For an injection diameter of 3 and 4 mm, cavity shear-layer and jet-wake stabilized combustions were observed as the scram modes. On the other hand, although the cavity shear-layer and lifted-shear-layer stabilized combustions were observed, no jet-wake stabilized combustion was observed for an orifice diameter of 2 mm. Fuel penetration heights above the cavity aft wall were expected to affect the combustion behavior. Finally, a morphology of the supersonic combustion modes was clearly shown in the two-dimensional latent space of the SGPVLM.
Reacting flow simulations for combustion applications require extensive computing capabilities. Leveraging the AMReX library, the Pele suite of combustion simulation tools targets the largest supercomputers available and future exascale machines. We introduce PeleC, the compressible solver in the Pele suite, and detail its capabilities, including complex geometry representation, chemistry integration, and discretization. We present a comparison of development efforts using both OpenACC and AMReX’s C++ performance portability framework for execution on multiple GPU architectures. We discuss relevant details that have allowed PeleC to achieve high performance and scalability. PeleC’s performance characteristics are measured through relevant simulations on multiple supercomputers. The success of PeleC’s design for exascale is exhibited through demonstration of a 160 billion cell simulation and weak scaling onto 100% of Summit, an NVIDIA-based GPU supercomputer at Oak Ridge National Laboratory. Our results provide confidence that PeleC will enable future combustion science simulations with unprecedented fidelity.
State redistribution is an algorithm that stabilizes cut cells for embedded boundary grid methods. This work extends the earlier algorithm in several important ways. First, state redistribution is extended to three spatial dimensions. Second, we discuss several algorithmic changes and improvements motivated by the more complicated cut cell geometries that can occur in higher dimensions. In particular, we introduce a weighted version with less dissipation in an easily generalizable framework. Third, we demonstrate that state redistribution can also stabilize a solution update that includes both advective and diffusive contributions. The stabilization algorithm is shown to be effective for incompressible as well as compressible reacting flows. Finally, we discuss the implementation of the algorithm for several exascale-ready simulation codes based on AMReX, demonstrating ease of use in combination with domain decomposition, hybrid parallelism and complex physics.
The rotating detonation engine (RDE) is an important realization of pressure gain combustion for rocket applications. The RDE system is characterized by a highly unsteady flow field, with multiple reflected pressure waves following detonation and an entrainment of partially-burnt gases in the post-detonation region. While experimental efforts have provided macroscopic properties of RDE operation, limited accessibility for optical and flow-field diagnostic equipment constrain the understanding of mechanisms that lend to wave stability, controllability, and sustainability. To this end, high-fidelity numerical simulations of a methane-oxygen rotating detonation rocket engine (RDRE) with an impinging discrete injection scheme are performed to provide detailed insight into the detonation and mixing physics and anomalous behavior within the system. Two primary detonation waves reside at a standoff distance from the base of the channel, with peak detonation heat release at approximately 10 mm from the injection plane. The high plenum pressures and micro-nozzle injector geometry contribute to fairly stiff injectors that are minimally affected by the passing detonation wave. There is no large scale circulation observed in the reactant mixing region, and the fuel distribution is asymmetric with a rich mixture attached to the inner wall of the annulus. The detonation waves’ strengths spatially fluctuate, with large variations in local wave speed and flow compression. The flow field is characterized by parasitic combustion of the fresh reactant mixture as well as post-detonation deflagration of residual gases. By the exit plane of the RDRE, approximately 95.7% of the fuel has been consumed. In this work, a detailed statistical analysis of the interaction between mixing and detonation is presented. The results highlight the merit of high-fidelity numerical studies in investigating an RDRE system and the outcomes may be used to improve its performance.
In this paper we develop a new technique, called state redistribution, that allows the use of explicit time stepping when approximating solutions to hyperbolic conservation laws on embedded boundary grids. State redistribution is a postprocessing technique applied after each time step or stage of the base finite volume scheme, using a time step that is proportional to the volume of the full cells. The idea is to stabilize the cut cells by temporarily merging them into larger, possibly overlapping neighborhoods, then replacing the cut cell values with a stabilized value that maintains conservation and accuracy. We present examples of state redistribution using two base schemes: MUSCL and a second order Method of Lines finite volume scheme. State redistribution is used to compute solutions to several standard test problems in gas dynamics on cut cell meshes, with both smooth and discontinuous solutions. We show that our method does not reduce the accuracy of the base scheme and that it successfully captures shocks in a non-oscillatory manner.
Rotating detonation engines (RDEs) are gaining significant interest as a practical approach to increasing the operating efficiency of propulsion systems through pressure gain combustion. To use RDEs in practical gas turbines, their stability and performance with regard to hydrocarbon fuels need to be tested. Prior experimental work has shown that ethylene/air systems exhibit suppressed wave propagation, with speeds that are nearly half the ideal wave speeds. The purpose of this study is to simulate realistic RDE configurations that have been experimentally studied to gain insight into this wave suppression. Detailed numerical simulations using a reduced 8-species 2-step and a 21-species 38-step chemistry model are conducted. When ethylene is diluted with hydrogen, the system reaches a stable mode comparable to detonation propagation after unsteady transition period between a weak deflagrative and a stronger detonation mode. It is further shown that pure ethylene cases stay in the weak regime with weak pressure propagation aided by deflagration along the wave path. Species, temperature, and pressure profiles normal to the wave front show a weak pressure rise followed by a broad reaction zone. As a result, heat release is not confined to the near-shock region but is distributed across the detonation chamber.
Direct numerical simulations were conducted to uncover physical aspects of a transverse sonic jet injected into a supersonic cross flow at a Mach number of 2.7. Simulations were carried out for two different jet-to-crossflow momentum flux ratios (J ) of 2.3 and 5.5. It is identified that collision shock waves behind the jet induce a herringbone separation bubble in the near-wall jet wake and a reattachment valley is formed and embayed by the herringbone recirculation zone. The recirculating flow in the jet leeward separation bubble forms a primary TCVP (trailing counter-rotating vortex pair) close to the wall surface. Analysis on streamlines passing the separation region shows that the wing of the herringbone separation bubble serves as a micro-ramp vortex generator and streamlines acquire rotating momentum downstream to form a secondary surface TCVP in the reattachment valley. Herringbone separation wings disappear in the farfield due to the cross interaction of lateral supersonic
flow and the expansion flow in the reattachment valley, which also leads to the vanishing of the secondary TCVP. A three-dimensional schematic of surface trailing wakes is presented and explains formation mechanism of the surface TCVPs.
Jet in supersonic crossflow (JISC) provide efficient mixing and flame stabilization in supersonic combustion. A LES-DQMOM based comprehensive methodology was developed and calculated sonic jet in Mach 2.0 crossflow with momentum ratio of 0.5, 1.03, and 1.52. JISC configuration were matched to experiment from Air Force Research Laboratory.1 After careful validation of the code, flow feature of non-reacting and reacting JISC were studied including shock structures and interaction of vortical structures. Turbulence-chemistry interactions are modeled using a DQMOM based combustion model. High temperature region near the wall upstream of the jet and the recirculated flow behind the barrel shock from the jet provided suitable condition of auto-ignition and flame stability.
The effects of injectant species on the turbulent structure and mixing state of jets in supersonic crossflow were investigated using a large-eddy simulation. Hydrogen, helium, nitrogen, and ethylene were transversely injected into a Mach 1.9 airflow at a constant jet-to-crossflow momentum flux ratio. The time-averaged distribution of jet concentration was roughly the same for all the injectant species, but the large-scale structure of scalar fluctuation differed significantly. The probability density functions of injectant mass fraction revealed that the turbulent behavior of nitrogen and ethylene jets was highly intermittent. The velocity field was considerably different between the injectants, owing to the different injection velocities. The hydrogen and helium jets had a much higher velocity difference between jet and crossflow in the near field; thus, the observed turbulent intensities for these two injectants were much higher than those for nitrogen and ethylene. In addition, the spectral analysis of velocity fluctuations in the windward mixing layer showed that the scale of energetic eddies was larger in the hydrogen and helium jets than in the nitrogen and ethylene jets. These characteristics resulted in better mixing in the hydrogen jet than in the ethylene jet for the studied injection conditions.
The pressure-sensitive-paint technique was used to determine the continuous surface-pressure held around a sonic jet injected transversely into a supersonic freestream of Mach 1.6. Three experimental conditions, with jet-to-crossflow momentum flux ratios of approximately 1.2, 1.7, and 2.2, were examined. The maximum static pressure upstream of the jet injection site was observed to increase with increasing momentum nu ratio, as did the size and streamwise extent of the low-pressure region downstream of the injector. About the circumference of the orifice, the pressure was observed to increase with increasing momentum flux ratio at the upstream edge of the jet, but was essentially independent of this ratio about the rest of the injector periphery. As a result of these pressure measurements, the effective back pressure, which is defined here as the circumferentially averaged wall pressure about the orifice periphery, was observed to increase weakly with increasing jet-to-crossflow momentum flux ratio over the range investigated.
A comparison of the penetration and mixing characteristics of three transverse/oblique injector configurations is presented. The three geometries studied include circular transverse, circular oblique, and elliptical transverse injectors, and the crossflow is at Mach 2. Planar Mie scattering images of three near-field flow planes produced substantial information about the flowfield created by each injector. In addition to global flowfield characteristics, the Mie scattering images provided transverse and lateral penetrations for each injector. Instantaneous and time-averaged information concerning the structural organization of the flowfields was obtained. Results demonstrate increasing jet penetration in the transverse direction with increasing jet-to-freestream momentum flux ratio. Penetration of the oblique jet is appreciably less in the near-field compared to the two transverse jets due to the reduced component of momentum in the transverse direction. The transverse elliptic jet appears to spread more quickly in the lateral direction than the other two jets, suggesting that some type of axis-switching phenomenon occurs. Large-scale structures at the interface between the jet and freestream fluids are shown for the two transversely oriented jets, while small-scale eddies are prominent in the oblique jet flowfield. Near-field mixing appears dominated by these eddies and the counter-rotating structures that develop in the streamwise direction.
The phenomena of penetration of gases into supersonic flow through circular orifices is discussed. Gases injected into a supersonic airstream penetrate to a height determined by the dynamic pressure ratio, with additional parameters influenced the process, including the boundary-layer (BL) thickness at the injector location, molecular weight ratio, and Reynolds number. The injected plume generates a bow shock that interacts with the incoming air BL and turbulent shear layer with a system of vortices spilling off the semicylindrical obstruction are formed. The jet is turned downstream and the vortices rotation axes align nearly with the airstream, facilitating jet-air mixing. Mixing is dominated by bulk mass transfer and the far-field mixing by the development of compressible shear layer. A lens-based schlieren system is used for penetration visualization. Gases injected into a Mach 1.6 airstream don't penetrate beyond the layer if the jet diameter is less than half of the BL thickness.
In the experiments highlighted here, incompressible skewed shear-layer mixing is studied. The mixing region is confined in the sense that the streams impinge somewhat on the side walls of the duct into which the two streams flow. Generally there are differences in the two streams'relative speeds in both the streamwise and spanwise directions, and therefore fluxes of two vorticity components separate from the splitter plate. The mass flow ratio is varied for a fixed amount of skewing, and mixing development within the duct is investigated.
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 compressibility levels that dramatically influence the characteristics of the large-scale structures formed in the shear layer and the entrainment and mixing occurring between the injectant and crossflow fluids. The large-scale eddies tend to rapidly break-up in the low compressibility injection case while those in the high compressibility case remain coherent over a longer spatial range. Mixing layer fluctuations present in the low compressibility case intrude deeply into the jet fluid as compared to the high compressibility case, where these fluctuations are confined near the jet edge.
Large-eddy simulation of an underexpanded sonic jet injection into supersonic crossflows is performed to obtain insights into key physics of the jet mixing. A high-order compact differencing scheme with a recently developed localized artificial diffusivity scheme for discontinuity-capturing is used. Progressive mesh refinement study is conducted to quantify the broadband range of scales of turbulence that are resolved in the simulations. The simulations aim to reproduce the flow conditions reported in the experiments of Santiago and Dutton [Santiago, J. G. and Diatom.). C., "Velocity Measurements of a Jet Injected into a Supersonic Crossflow," Jourual of Propulsion and Power, Vol. 132, 1997, pp. 264-273] and elucidate the physics of the jet mixing. A detailed comparison with these data is shown. Statistics obtained by the large-eddy simulation with turbulent crossflow show good agreement with the experiment, and a series of mesh refinement studies shows reasonable grid convergence in the predicted mean and turbulent flow quantities. The present large-eddy simulation reproduces the large-scale dynamics of the flow and jet fluid entrainment into the boundary-layer separation regions upstream and downstream of the jet injection reported in previous experiments, but the richness or data provided by the large-eddy simulation allows a much deeper exploration of the flow physics. Key physics of the jet mixing in supersonic crossflows are highlighted by exploring the underlying unsteady phenomena. The effect of the approaching turbulent boundary layer on the jet mixing is investigated by comparing the results of jet injection into supersonic crossflows with turbulent and laminar crossflows.
It is common for jets of fluid to interact with crossflow. This article reviews our understanding of the physical behavior of this important class of flow in the incompressible and compressible regimes. Experiments have significantly increased in sophistication over the past few decades, and recent experiments provide data on turbulence quantities and scalar mixing. Quantitative data at high speeds are less common, and visualization still forms an important component in estimating penetration and mixing. Simulations have progressed from the Reynolds-averaged methodology to large-eddy and hybrid methodologies. There is a general consensus on the qualitative structure of the flow at low speeds; however, the flow structure at low-velocity ratios (jet speed/crossflow speed) might be fundamentally different from the common notion of shear-layer vortices, counter-rotating vortex pairs, wakes, and horseshoe vortices. Fluid in the near field is strongly accelerated, which affects the jet trajectory, entrainment, ...
We present a second-order Godunov algorithm to solve time-dependent hyperbolic systems of conservation laws on irregular domains. Our approach is based on a formally consistent discretization of the conservation laws on a finite-volume grid obtained from intersecting the domain with a Cartesian grid. We address the small-cell stability problem associated with such methods by hybridizing our conservative discretization with a stable, nonconservative discretization at irregular control volumes, and redistributing the difference in the mass increments to nearby cells in a way that preserves stability and local conservation. The resulting method is second-order accurate in L1 for smooth problems, and is robust in the presence of large-amplitude discontinuities intersecting the irregular boundary.
The jet in crossflow or transverse jet has been studied extensively because of its relevance to a wide variety of flows in technological systems, including fuel or dilution air injection in gas turbine engines, thrust vector control for high speed airbreathing and rocket vehicles, and exhaust plumes from power plants. These widespread applications have led over the past 50+ years to experimental, theoretical, and numerical examinations of this fundamental flowfield, with and without a combustion reaction, and with single or multi-phase flow. The complexities in this flowfield, whether the jet is introduced flush with respect to the injection wall or from an elevated pipe or nozzle, present challenges in accurately interrogating, analyzing, and simulating important jet features. This review article provides a background on these studies and applications as well as detailed features of the transverse jet, and mechanisms for its control via active means. Promising future directions for the understanding, interrogation, simulation, and control of transverse jet flows are also identified and discussed.
In this paper we describe an adaptive Cartesian grid method for modeling timedependent inviscid compressible flow in irregular regions. In this approach a body is treated as an interface embedded in a regular Cartesian mesh. The single grid algorithm uses an unsplit second-order Godunov algorithm followed by a corrector applied to cells at the boundary. The discretization near the fluid-body interface is based on a volume-of-fluid approach with a redistribution procedure to maintain conservation while avoiding time step restrictions arising from small cells where the boundary intersects the mesh. The single grid Cartesian mesh integration scheme is coupled to a conservative adaptive mesh refinement algorithm that selectively refines regions of the computational grid to achieve a desired level of accuracy. Examples showing the results of the combined Cartesian grid integration/adaptive mesh refinement algorithm for both two- and three-dimensional flows are presented. 2 (This page inte...
Mixing, Chemical Reactions, and Combustion in Supersonic Flows
- N Cymbalist