Transitional Shock Boundary Layer Interactions on a Compression Ramp at Mach 4

We employ global input–output analysis to quantify amplification of exogenous disturbances in compressible boundary layer flows. Using the spatial structure of the dominant response to time-periodic inputs, we explain the origin of steady reattachment streaks in a hypersonic flow over a compression ramp. Our analysis of the laminar shock–boundary layer interaction reveals that the streaks arise from a preferential amplification of upstream counter-rotating vortical perturbations with a specific spanwise wavelength. These streaks are associated with heat-flux striations at the wall near flow reattachment and they can trigger transition to turbulence. The streak wavelength predicted by our analysis compares favourably with observations from two different hypersonic compression ramp experiments. Furthermore, our analysis of inviscid transport equations demonstrates that base-flow deceleration contributes to the amplification of streamwise velocity and that the baroclinic effects are responsible for the production of streamwise vorticity. Finally, the appearance of the temperature streaks near reattachment is triggered by the growth of streamwise velocity and streamwise vorticity perturbations as well as by the amplification of upstream temperature perturbations by the reattachment shock.

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An instability in supersonic boundary-layer flow over a compression ramp

Journal of Fluid Mechanics ◽

10.1017/s0022112095003685 ◽

1995 ◽

Vol 300 ◽

pp. 265-285 ◽

Cited By ~ 25

Author(s):

K. W. Cassel ◽

A. I. Ruban ◽

J. D. A. Walker

Keyword(s):

Boundary Layer ◽

Boundary Layer Flow ◽

Streamwise Velocity ◽

Supersonic Boundary Layer ◽

Recirculation Region ◽

Hypersonic Boundary Layer ◽

Recirculating Flow ◽

Inflection Points ◽

Compression Ramp ◽

Layer Flow

Separation of a supersonic boundary layer (or equivalently a hypersonic boundary layer in a region of weak global interaction) near a compression ramp is considered for moderate wall temperatures. For small ramp angles, the flow in the vicinity of the ramp is described by the classical supersonic triple-deck structure governing a local viscous-inviscid interaction. The boundary layer is known to exhibit recirculating flow near the corner once the ramp angle exceeds a certain critical value. Here it is shown that above a second and larger critical ramp angle, the boundary-layer flow develops an instability. The instability appears to be associated with the occurrence of inflection points in the streamwise velocity profiles within the recirculation region and develops as a wave packet which remains stationary near the corner and grows in amplitude with time.

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Compression Ramp Induced Shock-Wave/Turbulent Boundary-Layer Interactions on a Compliant Material

AIAA Journal ◽

10.2514/1.j056652 ◽

2018 ◽

Vol 56 (7) ◽

pp. 2925-2929 ◽

Cited By ~ 5

Author(s):

Harry T. Pham ◽

Zachary N. Gianikos ◽

Venkateswaran Narayanaswamy

Keyword(s):

Boundary Layer ◽

Shock Wave ◽

Turbulent Boundary Layer ◽

Compression Ramp ◽

Compliant Material

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Direct simulation of the turbulent boundary layer along a compression ramp at M = 3 and Reθ = 1685

Journal of Fluid Mechanics ◽

10.1017/s0022112000001257 ◽

2000 ◽

Vol 420 ◽

pp. 47-83 ◽

Cited By ~ 190

Author(s):

NIKOLAUS A. ADAMS

Keyword(s):

Boundary Layer ◽

Turbulent Boundary Layer ◽

Layer Thickness ◽

Boundary Layer Thickness ◽

Free Stream ◽

Shear Stresses ◽

Numerical Representation ◽

Computational Domain ◽

The Mean ◽

Compression Ramp

The turbulent boundary layer along a compression ramp with a deflection angle of 18° at a free-stream Mach number of M = 3 and a Reynolds number of Reθ = 1685 with respect to free-stream quantities and mean momentum thickness at inflow is studied by direct numerical simulation. The conservation equations for mass, momentum, and energy are solved in generalized coordinates using a 5th-order hybrid compact- finite-difference-ENO scheme for the spatial discretization of the convective fluxes and 6th-order central compact finite differences for the diffusive fluxes. For time advancement a 3rd-order Runge–Kutta scheme is used. The computational domain is discretized with about 15 × 106 grid points. Turbulent inflow data are provided by a separate zero-pressure-gradient boundary-layer simulation. For statistical analysis, the flow is sampled 600 times over about 385 characteristic timescales δ0/U∞, defined by the mean boundary-layer thickness at inflow and the free-stream velocity. Diagnostics show that the numerical representation of the flow field is sufficiently well resolved.Near the corner, a small area of separated flow develops. The shock motion is limited to less than about 10% of the mean boundary-layer thickness. The shock oscillates slightly around its mean location with a frequency of similar magnitude to the bursting frequency of the incoming boundary layer. Turbulent fluctuations are significantly amplified owing to the shock–boundary-layer interaction. Reynolds-stress maxima are amplified by a factor of about 4. Turbulent normal and shear stresses are amplified differently, resulting in a change of the structure parameter. Compressibility affects the turbulence structure in the interaction area around the corner and during the relaxation after reattachment downstream of the corner. Correlations involving pressure fluctuations are significantly enhanced in these regions. The strong Reynolds analogy which suggests a perfect correlation between velocity and temperature fluctuations is found to be invalid in the interaction area.

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