Research On Shock/boundary-layer Interactions And Control Techniques Based On Vortex Generator Jets Of Hypersonic Inlets

A set of numerical simulation method for supersonic wall-bounded turbulent flowswere studied and a freejet experimental facility was built in the present work.Shock/boundary layer interactions and the control of boundary-layer separation withvortex generator jets in hypersonic inlets were investigated and experimental validationswere performed.A WENO scheme based on low diffusion flux splitting method was constructedand used in the calculation of Riemann problem. The results showed it has betterresolution than the traditional WENO scheme based on Lax-Fridrichs splitting.A hybrid Large-Eddy/Reynolds-Averaged Navier-Stokes(hybrid LES/RANS)method for supersonic wall-bounded turbulent flows was established and analyzedtheoretically. In the calculation of a high Reynolds-number supersonic turbulentboundary-layer, geometric dimensions, grid resolution and the transition characteristicsof the blending function were considered. The results showed that the mean parametersof the inflow boundary-layer shifted unreasonably in two-dimensional calculation. TheRANS to LES transition zone should be placed in the interface region of logarithmiclayer and wake layer and the transition zone should be narrow. Acceptable predictionsof Reynolds stress can be obtained if streamwise and spanwise grid spacings are scaledaccording to the Escudier mixing length.A recycling/rescaling method for generating turbulent inflow flucutations wasestablished. The effects of spanwise width, recycling distance and grid resolution werestudied in the calculation of a supersonic turbulent boundary-layer. The results showedthat inadequate spanwise width led to shift of the mean inflow parameters.Unreasonable periodic vortex structures and streaks of streamwise velocity appearedwith inadequate recycling distance. Good predictions of Reynolds stress could beobtained by the recycling/rescaling method with enough grid resolution. Klebanoffintermittency function helped attenuate fluctuations in the outer layer of theboundary-layer and thus improved the calculation of Reynolds stress.Flow fileds in hypesonic inlets were simplified and calculated, including anunstarted flow field in a two-dimensional inlet and two crossing-shock/boundary-layerinteraction(CSBLI) cases. The results showed that the shock systems and separationzones in all three cases exhibited low-frequency motions in large scale of time andspace and their main frequencies were close to theoretic values. In the two-dimensionalinlet case, the flow field might be switch between start and unstart intermittently, andthe flow in the isolator exhibited similar low-frequency characteristic in the separationregion. In the two CSBLI cases, the motion of the shock system and separation regionexhibited in larger scale when interaction strength increased. The interaction of between vortex generator jet and supersonic boundary-layer wasinvestigated. The flow field includes asymmetric bow shock, barrel shock andstreamwise vortex pairs. The streamwise vortex on the side which the jet inclined to wasstronger, closer to the wall, generated earlier and existed with shorter duration than itscounterparts on the other side of the jet. The control effect of a two-dimensionalboundary-layer separation zone with a vortex generator was validated. The resultsshowed that increasing pressure of the jet makes the separation zone become smaller.An optimal pitch angle is close to45degrees and the change of yaw angle seemsineffective to the flow field. The distance from the jet to the separation region should belong enough for the streamwise vortexes to play a role on the separation. Double jetswith inadequate distance of each other promoted the interaction of the streamwisevortexes and make them dissipate fastser. Co-direction jets did a better job thancounter-direction jet in the control of the separation zone.