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Numerical research on mixing characteristics of different injection schemes for supersonic transverse jet

Science China(Technological Sciences) 2011年第4期54卷 883-893页

作者： lee chunhian School of Aeronautical Science and Engineering Beihang University

A numerical method using AUSMDV scheme and k-ω SST turbulence model with an explicit compressibility correction was developed,and a 3-D numerical simulation of a supersonic flow field with a vertical sonic jet of hydrogen was *** agreement between numerical results and experimental data validated the reliability of the numerical ***,two parameters,mass-weighted average total pressure and mixing efficiency,were defined to evaluate the mixing performance of different injection *** on the numerical method and evaluation criterion,the mixing characteristics of different injection schemes were studied in *** was found that for the mixing field of supersonic transverse jet,the near-field mixing is controlled by convection transport while the far-field mixing is controlled by mass diffusion;the circular-hole injection causes a loss of total pressure comparable to the slot injection,but can induce a much higher mixing efficiency because of its 3-D flow characteristic;the variation of injection angle under circular-hole injection mainly affects the near-field mixing degree,and among the five injection angles studied in the present paper,angle 120° is the optimal one;with the increase of the ratio between injector space and diameter,the induced mixing efficiency increases while the caused loss of total pressure can grow greatly;the two-stage injection method designed through reducing the injector area to keep the same hydrogen mass flowrate can induce a much higher mixing efficiency while only a bit larger loss of total pressure when compared to the single-stage injection,and hence the two-stage injection is superior to the single-stage *** research results can direct the design of the fuel injection method in the combustor of scramjet engine.

关键词： supersonic mixing mixing efficiency injection scheme numerical simulation

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A Favré averaged transition prediction model for hypersonic flows

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Science China(Technological Sciences) 2010年第8期53卷 2049-2056页

作者： lee chunhian School of Aeronautical Sciences and Engineering Beijing University of Aeronautics and Astronautics

Transition prediction is crucial for aerothermodynamic and thermal protection system design of hypersonic *** compressible form of laminar kinetic energy equation is derived based on Favréaverage formality in the present paper.A closure of the equation is deduced and simplified under certain hypotheses and scaling analysis.A laminar-to-turbulent transition prediction procedure is proposed for high Mach number flows based on the modeled Favré-averaged laminar kinetic energy equation,in conjunction with the Favré-averaged Navier-Stokes *** proposed model,with and without associated explicit compressibility terms,is then applied to simulate flows over flared-cones with a free-stream Mach number of 5.91,and the onset locations of the boundary layer transition under different wall conditions are *** computed onset locations are compared with those obtained by the model based on a compressibility correction deduced from the reference-temperature concept,together with experimental *** is revealed that the present model gives a more favorable transition prediction for hypersonic flows.

关键词： transition prediction laminar fluctuation hypersonic compressibility

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Numerical investigation of compressibility effects in turbulent channel flows using large eddy simulation

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Science China(Physics,Mechanics & Astronomy) 2012年第2期55卷 305-315页

作者： lee chunhian School of Aeronautic Sciences and Engineering Beihang UniversityBeijing 100191 China

The large eddy simulation (LES) of compressible turbulent channel flows at three different Mach numbers is performed in the present work,by extending the dynamic mixed subgrid-scale (SGS) model to compressible *** turbulent statistics agree well with those from the existing direct numerical simulation (DNS) results,indicating that the LES method established in the present work is *** analysis of the turbulent fluctuations computed by the present LES reveals that the flows considered in this work follow the Morkovin's ***,the compressibility effects are dominated by the mean field properties,and the relevant statistical ratios are invariant to the variation of Mach *** near-wall streamwise streaks are more coherent and the spacing between streaks is wider as the Mach number *** can be regarded as a direct feature characterized by the compressibility *** restrained influences of compressibility effects on the production and dissipation of the turbulence kinetic energy are also identified based on the present LES results.

关键词： compressibility channel flow large eddy simulation subgrid-scale model

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Characterization of the three-dimensional supersonic flow for the MHD generator

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Science China(Physics,Mechanics & Astronomy) 2009年第4期52卷 534-545页

作者： lee chunhian National Laboratory for Computational Fluid Dynamics Beihang University

A numerical procedure based on a five-wave MHD model associated with non-ideal,low magnetic Reynolds number MHD flows was developed in the present study for analyzing the flow fields in the MHD generator of a MHD bypass scramjet. The numerical procedure is composed of an entropy conditioned scheme for solving the non-homogeneous Navier-Stokes equations,in conjunction with an SOR method for solving the elliptic equation governing the electrical potential. It was found that a separation would take place near the downstream edge of the second electrode,where the local adverse pressure gradient is large,and the core of the flow field is characterized as a 2-D flow due to the Hartmann effects along the direction of the magnetic field. The electric current lines would be increasingly distorted as the magnetic interactive parameter increases,and even induce an eddy current. Induced eddy current was also found in the different cross-sections along the axial direction,all of these would definitely deteriorate the performance of the MHD generator. The cross-sectional M-shape velocity profile found along the axial direction between the insulating walls is responsible for the formation of the vortex flow at the corner of the insulator cross-section,which,in turn,induces the corner eddy current at the corner. A numerical parametric study was also performed,and the computed performance parameters for the MHD generator suggest that,in order to enhance the performance of MHD generator,the magnetic interaction parameter should be elevated.

关键词： MHD generator entropy conditioned scheme SOR numerical simulation

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Direct numerical simulation of the turbulent MHD channel flow at low magnetic Reynolds number for electric correlation characteristics

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Science China(Physics,Mechanics & Astronomy) 2010年第10期53卷 1901-1913页

作者： lee chunhian School of Aeronautic Science and Engineering Beijing University of Aeronautics and Astronautics

Direct numerical simulation (DNS) of incompressible magnetohydrodynamic (MHD) turbulent channel flow has been performed under the low magnetic Reynolds number *** velocity-electric field and electric-electric field correlations were studied in the present work for different magnetic field *** Kenjeres-Hanjalic (K-H) model was validated with the DNS data in a term by term *** numerical results showed that the K-H model makes good predictions for most components of the velocity-electric field *** mechanisms of turbulence suppression were also analyzed for different magnetic field orientations utilizing the DNS data and the K-H *** results revealed that the dissipative MHD source term is responsible for the turbulence suppression for the case of streamwise and spanwise magnetic orientation,while the Lorentz force which speeds up the near-wall fluid and decreases the production term is responsible for the turbulence suppression for the case of the wall normal magnetic orientation.

关键词： low magnetic Reynolds number assumption magnetohydrodynamic turbulence DNS velocity-electric field correlation electric-electric field correlation channel flow

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A numerical study of turbulent combustion characteristics in a combustion chamber of a scramjet engine

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Science China(Technological Sciences) 2010年第8期53卷 2111-2121页

作者： lee chunhian School of Aeronautical Sciences and Engineering Beihang University

3D numerical simulation of flow fields in a combustion chamber of a scramjet engine using an SST turbulence model with an explicit compressibility correction was performed and the results were compared to the experimental *** characteristics of the turbulent combustion flow fields were analyzed via the numerical results and *** order to identify the mechanisms of turbulent combustion in supersonic flows,the evolutions of governing dimensionless parameters in the flow fields were investigated based on the theory of combustion and the available numerical *** was found that the supersonic combustion takes place in the region of fully developed turbulence and that the strongest effects of turbulence and combustion processes appear in the vicinity of the *** unsteady effects and the local flame extinction phenomenon induced by turbulent flows were found to be negligibly small,and the steady flamelet approximation will hold for practical applications.

关键词： scramjet turbulent combustion flamelet approximation numerical simulation

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A flamelet model for turbulent diffusion combustion in supersonic flow

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Science China(Technological Sciences) 2010年第12期53卷 3379-3388页

作者： lee chunhian School of Aeronautical Science and Engineering Beihang University

In order to develop a turbulent diffusion combustion model for supersonic flow, the physical argument of the extension of the flamelet model to supersonic flow was presented, and the flow field of a hydrogen/air diffusion combustion generated by axisymmetric supersonic jets was numerically simulated by employing the flamelet model. Using the experimental data, value of the model coefficient of scalar dissipation in the flamelet model was revised specifically for supersonic flow. The computational results of the modified flamelet model were compared with the experimental results, and it was indicated that the precision of the modified flamelet model was satisfying. Based on the numerical results and flamelet theory, the influence mechanisms of turbulence fluctuation on the average state equation and chemical reaction rate were studied for the first time. It was found that the fluctuation correlation of species mass fractions and temperature has little effect on the averaged gas state equation; the temperature fluctuation decreases the product of H2O, but its effect is small; the fluctuation of species mass fractions increases the product of H2O in the region close to oxidizer while decreases the product of H2O in other regions; the fluctuation correlation of species mass fractions and temperature largely decreases the product of H2O.

关键词： scramjet turbulent diffusion combustion flamelet model numerical simulation

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Simulation of three-dimensional nonideal MHD flow at low magnetic Reynolds number

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Science China(Technological Sciences) 2009年第12期52卷 3690-3697页

作者： lee chunhian National Laboratory for Computational Fluid Dynamics Beihang University

A numerical procedure based on a five-wave model associated with non-ideal,low magnetic Reynolds number magnetohydrodynamic(MHD)flows was *** is composed of an entropy conditioned scheme for solving the non-homogeneous Navier-Stokes equations,in conjunction with an SOR method for solving the elliptic equation governing the electrical potential of flow *** validate the developed procedure,two different test cases were used which included MHD Rayleigh problem and MHD Hartmann *** simulations were performed under the assumption of low magnetic Reynolds *** simulated results were found to be in good agreement with the closed form analytical solutions deduced in the present study,showing that the present algorithm could simulate engineering MHD flow at low magnetic Reynolds number *** the end,a flow field between a pair of segmented electrodes in a three dimensional MHD channel was simulated using the present algorithm with and without including Hall *** the introduction of Hall effects,no distortion was observed in the current and potential *** taking the Hall effects into account,the potential lines distorted and clustered at the upstream and downstream edges of the cathode and anode,respectively.

关键词： magnetohydrodynamics(MHD) numerical simulation MHD Rayleigh flow MHD Hartmann flow MHD generator

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An implicit algorithm based on iterative modified approximate factorization method coupling with characteristic boundary conditions for solving subsonic viscous flows

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Science China(Physics,Mechanics & Astronomy) 2013年第6期56卷 1187-1208页

作者： lee XuZhi lee chunhian National Laboratory for Computational Fluid Dynamics Beihang University

An algorithm composed of an iterative modified approximate factorization(MAF(k)) method with Navier-Stokes characteristic boundary conditions(NSCBC) is proposed for solving subsonic viscous flows.A transformation on the matrix equation in MAF(k) is made in order to impose the implicit boundary conditions *** be in consistent with the implicit solver for the interior domain,an implicit scheme for NSCBC is *** performance of the developed algorithm is investigated using spatially evolving zero pressure gradient boundary layer over a flat plate and a wall jet mixing with a cross flow over a flat plate with a square hole as the test *** numerical results are compared to the existing experimental datasets and a number of general correlations,together with other available numerical solutions,which demonstrate that the developed algorithm possesses promising capacity for simulating the subsonic viscous flows with large CFL number.

关键词： iterative modified approximate factorization Navier-Stokes characteristic boundary conditions subsonic viscous flow

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Numerical investigation on jet interaction with a compression ramp

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Chinese Journal of Aeronautics 2013年第4期26卷 898-908页

作者： Zhen Huaping Gao Zhenxun lee chunhian School of Aeronautic Science and Engineering Beihang University

A numerical investigation on jet interaction in supersonic laminar flow with a compres- sion ramp is performed utilizing the AUSMDV scheme and a parallel solver. Several parameters dominating the interference flowfield are studied after defining the relative increment of normal force and the jet amplification factor as the evaluation criterion of jet control performance. The computational results show that most features of the interaction flowfield between the transverse jet and the ramp are similar to those between a jet and a flat plate, except that the flow structures are more complicated and the low-pressure region behind the jet is less extensive. The relative force increment and the jet amplification factor both increase with the distance between the jet and the ramp shortening till quintuple jet diameters. Inconspicuous difference is observed between the jet-before-ramp and jet-on-ramp cases. The variation of the injection angle changes the extent of the separation region, the plateau pressure, and the peak pressure near the jet. In the present computational conditions, 120 is indicated relatively optimal among all the injection angles studied. For cold gas simulations, although little influence of the jet temperature on the pressure distribution near the jet is observed under the computation model and the flow parameters studied, reducing jet temperature somehow benefits the improvement of the normal force and the jet efficiency. When the pressure ratio of jet to freestream is fixed, the relative force increment varies little when increasing the freestream Mach number, while the jet amplification factor increases.

关键词： Air pressure Amplification factor Computational aerodynam- ics Navier-Stokes equations Pitch control Transverse jet

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