Effects of shock on the stability of hypersonic boundary layers (original) (raw)
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Hypersonic shock wave transitional boundary layer interactions - A review
Acta Astronautica, 2018
Hypersonic shock wave transitional boundary layer interactions can result in significantly greater peak surface heat transfer than laminar or turbulent interactions. Consequently, the understanding of the flowfield structure of hypersonic shock wave transitional boundary layer interactions is important. Moreover, the capability to predict the mean and fluctuating aerothermodynamic loading due to such interactions is needed for effective design of hypersonic vehicles. A review of hypersonic shock wave transitional boundary layer interaction research since 1993 is presented. Significant progress has been achieved in the understanding of the flowfield structure. The most promising prediction methodology is Direct Numerical Simulation (DNS); however, DNS requires dynamic (i.e., time varying) inflow boundary conditions for five flow variables (i.e., three components of velocity, and two thermodynamic variables), and such experimental data is presently infeasible. Additional research is needed to understand the effect of assumed dynamic inflow boundary conditions on DNS prediction of aerothermodynamic loads.
Physics of Fluids, 2018
Unsteadiness of axisymmetric shock-dominated hypersonic laminar separated flow over a double cone is studied for the first time using a combination of time accurate Direct Simulation Monte Carlo (DSMC) calculations, linear global instability analysis, and momentum potential theory (MPT). Close to steady state linear analysis reveals the spatial structure of the underlying temporally stable global modes. At all Reynolds numbers examined, the amplitude functions demonstrate the strong coupling between the separated flow region at the cone junction with the entire shock system, including pressure and temperature waves generated behind the shock and spatially amplified Kelvin-Helmholtz waves. In addition, as the Reynolds number is increased, temporally damped harmonic shock oscillations and multiple-reflected λ-shock patterns emerge in the eigenfunctions. Application of the MPT (valid for both linear and nonlinear signals) to the highest Reynolds number DSMC results shows that large aco...
Multi-scale study of the transitional shock-wave boundary layer interaction in hypersonic flow
Theor. Comput. Fluid Dyn., 2021
A high-fidelity simulation of the massively separated shock/transitional boundary layer interaction caused by a 15-degrees axisymmetrical compression ramp is performed at a free stream Mach number of 6 and a transitional Reynolds number. The chosen configuration yields a strongly multiscale dynamics of the flow as the separated region oscillates at low-frequency, and high-frequency transitional instabilities are triggered by the injection of a generic noise at the inlet of the simulation. The simulation is post-processed using Proper Orthogonal Decomposition to extract the large scale low-frequency dynamics of the recirculation region. The bubble dynamics from the simulation is then compared to the results of a global linear stability analysis about the mean flow. A critical interpretation of the eigenspectrum of the linearized Navier-Stokes operator is presented. The recirculation region dynamics is found to be dominated by two coexisting modes, a quasi-steady one that expresses itself mainly in the reattachment region and that is caused by the interaction of two self-sustained instabilities, and an unsteady one linked with the separation shock-wave and the mixing layer. The unsteady mode is driven by a feedback loop in the recirculation region, which may also be relevant for other unsteady shock-motion already documented for shock-wave/turbulent boundary layer interaction. The impact of the large-scale dynamics on the transitional one is then assessed through the numerical filtering of those low wavenumber modes; they are found to have no impact on the transitional dynamics.
Shock wave boundary layer interactions in hypersonic flows
International Journal of Heat and Mass Transfer, 2014
Shock wave boundary layer interaction phenomena play a critical role in the design of supersonic and hypersonic vehicles. Consequently, this paper mainly focuses on hypersonic flow over a double wedge
39th Aerospace Sciences Meeting and Exhibit, 2001
A high-order upwind finite difference shock fitting scheme and semi-implicit method is applied in the simulation of transient nonequilibrium hypersonic boundary-layer flows. The results from TVD method are used as inflow conditions to commence numerical simulation of hypersonic flow over flat plates by shockfitting method, which are validated by comparing the numerical results with experimental resutls. The receptivities to three different types of forcing disturbances for a Mach 4.5 flow over a flat plate are studied. A LST-code based on multi-domain spectral method is also developed to identify instability modes. The results of stability from DNS are compared with that of LST prediction. The receptivity coefficient for flow over a flat plat at MacM.5 to plane acoustic waves at zone angle is close to 1. The receptivity and stability of a Mach 10 oxygen flow over a flat plate is studied in both perfect gas and thermochemically nonequilibrium regime. Real gas effect is destabilizing for the boundary-layer disturbances in this case.
Shock Wave/Transitional Boundary-Layer Interactions in Hypersonic Flow
AIAA Journal, 2006
The experimental and numerical transitional interactions in hypersonic flow are studied. The experiments were performed on a hollow cylinder-flare model in the ONERA R2Ch wind tunnel at a Mach number of 5 and for varying stagnation pressure. Wall pressure and heat-flux measurements, laser Doppler velocimetry, pitot boundary-layer surveys, surface flow visualizations, and schlieren photographs provide a precise and complete description of the flowfield. In all of the cases examined here, grid-converged axisymmetric mathematical solutions of the problem were obtained by use of the two-dimensional numerical simulation, but it was found that these solutions do not fit experiments when the Reynolds number is increased. A purely three-dimensional organization of the flow then appears, characterized by the Görtler vortices. Two families of solutions were thus evidenced, and the precise calculation of the physical one remains a numerical challenge. The prediction of transition by use of stability calculations is only partly possible because the waves used do not have a sufficiently general form to model such a complex physical problem. New information on the true nature of what is commonly called a transition mechanism in this kind of flow is deduced from these results.
Simulation of Hypersonic Shock/Turbulent Boundary-Layer Interactions Using Shock-Unsteadiness Model
In hypersonic flows, the interaction of a shock wave with a turbulent boundary layer can result in flow separation and high aerothermal loads. In this paper, cone–flare configurations with different flare angles and freestream Mach numbers are simulated using Reynolds-averaged Navier–Stokes method, and results are compared with experimental data. The standard Spalart–Allmaras and k-!turbulence models do not predict flow separation at the cone–flare junction, and therefore yield a large deviation from the surface pressure measurements. Sinha et al. (“Modeling Shock-Unsteadiness in Shock/Turbulence Interaction,” Physics of Fluids, Vol. 15, No. 8, 2003, pp. 2290– 2297) proposed a shock-unsteadiness model to account for the effect of unsteady shock motion in a steady mean flow. The shock-unsteadiness correction damps turbulence amplification at the shock and results in significant improvement in predicting flow separation and reattachment. The flow topology in the interaction region, in terms of the pattern of shocks and expansion waves, is predicted correctly by the modified turbulence models. The resulting surface pressure distribution matches experimental data well.
Numerical Study of Shock-Boundary Layer Interaction in Hypersonic Flow
The aim of the present work is to access the ability of the three-dimensional RANS code MB-EURANIUM is predicting shock wave boundary-layer interaction. Results are presented for two cases in this paper. The first is the turbulent boundary-layer shock interaction on a twodimensional ramp. The second case is that of laminar boundary-layer shock interaction over a blunted cone-flare.
Nonparallel effects in hypersonic boundary layer stability
33rd Aerospace Sciences Meeting and Exhibit, 1995
their strength at yet higher temperatures. Failing this, the designers must add heat shielding, further weighing The nonparallel effects on the stability of the flow over the vehicle down, a Mach 8, 7 ' half-angle cone at 2' angle of attack are The prediction of transition to turbulence of hyperinvestigated with the Parabolized Stability Equations. sonic flows is a daunting task. While much progress The results are compared to those from local stability has been made in the of transition in analyses. Both analyses are performed with two difsubsonic floWs12, the methods used are difficult to exferent sets of flow variables. It is found that the local tend to hypersonic flows. analyses produce different results for different Sets of M~~~ of these difficulties are experimental in navariables when nonparallel terms are evaluated locally. ture, Controlled disturbances in subsonic boundary This is an artifact of the local approximation. The PSE layers can be excited with vibrating ribbons, The die analyses converge to the same solution downstream inturbances can then be carefully measured as they grow dependent of the variables chosen. The nonparallel efand evolve downstream. This is much difficult to fects for this flow are thus very significant but can be do in hypersonic flows. Rypersonic test facilities instead modeled accurately with the PSE. are often plagued with noise generated by the turbulent boundary layers on the wind tunnel walls. This excites a broad and unknown spectrum of disturbances in the