The paper evaluates the evolvement of coherent structures and penetration height of gaseous transverse jet penetration into a supersonic turbulent flow.The high spatiotemporal resolution coherent structures of the jet plume are obtained by utilizing the nanoparticle-based planar laser scattering technique(NPLS).The evolving pattern of the coherent structures generated on the upwind surface of the transverse jet is analyzed based on the NPLS images.The shedding eddies from the jet near-field have lower convection velocity along freestream direction,while vortex growth rate is apparently higher than the far-field.Farther downstream,the large-scale eddies have less deformation and translate at velocities near the freestream velocity.Thus the near-field determines the scale of eddies in the far-field and affects the whole mixing process.The effect of injection stagnation pressure on the coherent structures is discussed and a modified penetration correlation is proposed based on an edge approximation definition and least square method with various injection pressures.
SUN MingBoZHANG ShunPingZHAO YanHuiZHAO YuXinLIANG JianHan
Combustion oscillations in a supersonic combustor with hydrogen injection upstream of a cavity flameholder are investigated using nonlinear analysis based on experimental measurements.Time series of both flamefront and wall pressure are acquired,and the state space reconstruction approach is adopted to characterize the nonlinear behavior of the combustion oscillations.Three overall equivalence ratios,0.038,0.076 and 0.11,are considered.The existence of a chaotic source in the present combustion system is demonstrated.The correlation dimension and the largest Lyapunov exponent tend to become larger with the increasing equivalence ratio,indicating a more complicated and unstable combustion system.In particular,it is found that the correlation dimension for the highest equivalence ratio is much greater than those of the two lower equivalence ratios.Two possible reasons responsible for the observed nonlinear behaviors are identified.One is the shock-related instabilities and the other is the transition of combustion stabilization mode between the cavity and jet-wake stabilized mode.
The study has evaluated the coherent structures and the velocity field of gaseous transverse jet upstream of a scramjet flameholder in a supersonic turbulent flow.The high spatiotemporal resolution coherent structures of the jet plume/wakes and the cavity shear layer were obtained by utilizing the nanoparticle-based planar laser scattering technique.Compared to the no upstream injection case,the cavity shear layer downstream of the jet shows significant mass exchange with mainstream.The particle image velocimetry velocity field and the velocity profiles demonstrated that the interaction intensity of the cavity shear layer with the upstream injection is further enhanced as the injection stagnation pressure increases.
A sonic under-expanded transverse jet injection into a Ma 1.6 supersonic crossflow is investigated numerically using our hybrid RANS/LES (Reynolds-averaged Navier-Stokes/large eddy simulation) method. First, a calculation is carried out to validate the code, where both the instantaneous and statistical results show good agreement with the existing experimental data. Then the jet-mixing characteristics are analyzed. It is observed that the large-scale vortex on the windward portion of the jet boundary is formed mainly by the intermittent impingement of the incoming high-speed fluid on the relatively low-speed region of the upstream jet boundary, where the interaction between the upstream separated region and the jet supplies a favorable pressure condition for the sustaining acceleration of the high-speed fluid during the vortex forming, associated with which the incoming fluid is entrained into the jet boundary and large-scale mixing occurs. Meanwhile, the secondary recirculation zone between the upstream separated region and the jet is observed to develop evidently during the vortex forming, inducing the entrainment of jet fluid into the upstream separated region. Moreover, effects of the incoming boundary layer on the jet mixing are addressed.
