Proceedings ArticleDOI
Temperature / rarefaction effects in hypersonic boundary-layer flow with an oblique roughness element
TLDR
In this article, three-dimensional laminar hypersonic boundary-layer flows are investigated applying the compressible bi-global linear stability theory (B-LST) in flow crossplanes.Abstract:
Three-dimensional laminar hypersonic boundary-layer flows are investigated applying the compressible bi-global linear stability theory (B-LST) in flow crossplanes. The flat-plate flow is altered by an obliquely placed discrete fence-like roughness element that is about half the boundary-layer thickness high. Roughness setup and flow conditions resemble the STS-119 flight experiment. A cold-flow case and hot-flow cases are considered. The influence of non-perfect gas properties such as variable chemical composition, or thermal energy relaxation are included. The steady base flows are extracted from Navier-Stokes simulations. The underlying gas modell for reacting and non-reacting air accounts for thermal as well as chemical nonequilibrium. Rarefaction effects are considered in terms of a slip condition for velocity and temperature at the wall. Stability properties of the roughness wake under cold, hot, and hot rarefied flow conditions are compared in terms of local and integral growth.read more
Citations
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Proceedings ArticleDOI
Wake Instabilities Behind Discrete Roughness Elements in High Speed Boundary Layers
TL;DR: In this paper, the authors studied the flow past an isolated, spanwise symmetric roughness element in zero pressure gradient boundary layers at Mach 3.5 and 5.9, with an emphasis on roughness heights of less than 55 percent of the local boundary layer thickness.
Journal ArticleDOI
Instability and transition mechanisms induced by skewed roughness elements in a high-speed laminar boundary layer
Gordon Groskopf,Markus J. Kloker +1 more
TL;DR: In this paper, the disturbance evolution in a Mach-4.8 zero-pressure-gradient flat-plate boundary-layer flow altered by discrete three-dimensional roughness elements is investigated including a laminar breakdown scenario.
Computations of Disturbance Amplification Behind Isolated Roughness Elements and Comparison with Measurements
TL;DR: In this article, a laminar-turbulent transition due to isolated roughness elements in boundary layers at Mach 3.5 and 5.95 was investigated. But the authors focused on flow configurations for which experimental measurements from low disturbance wind tunnels are available.
Proceedings ArticleDOI
Transition Delay by Oblique Roughness Elements in a Blasius Boundary-Layer Flow
TL;DR: In this article, a passive device to delay the laminar-turbulent transition in a Blasius boundary-layer flow is tested at low Reynolds numbers in the Laminar water channel.
Dissertation
Development of a hybrid DSMC/CFD method for hypersonic boundary layer flow over discrete surface roughness
TL;DR: In this paper, the authors propose a method to solve the problem of "uniformity" and "uncertainty" in the context of data mining, and propose a solution.
References
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Steady solutions of the Navier-Stokes equations by selective frequency damping
TL;DR: In this article, the Navier-Stokes equations in globally unstable configurations are computed by damping the unstable (temporal) frequencies, which is achieved by adding a dissipative relaxation term proportional to the high-frequency content of the velocity fluctuations.
Journal ArticleDOI
Real gas effects on hypersonic boundary-layer stability
M. R. Malik,E. C. Anderson +1 more
TL;DR: In this paper, the authors investigated the stability of high-temperature boundary layers under the assumption of chemical equilibrium and this gas model is labeled as real gas model and found that real gas effects cause the first mode instability to stabilize while the second mode is made more unstable.
Journal ArticleDOI
Secondary instability of crossflow vortices: validation of the stability theory by direct numerical simulation
TL;DR: In this paper, a comparison of spatial direct numerical simulations (DNS) and secondary linear stability theory (SLST) is provided for the three-dimensional crossflow-dominated boundary layer also considered at the DLR-G for experiments and theory.
Journal ArticleDOI
Linear stability of hypersonic flow in thermochemical nonequilibrium
TL;DR: In this article, the effect of thermal and chemical nonequilibrium on stability is shown to depend on the disturbance mode and the frequency and spatial ampli® cation of disturbances that may lead to boundary layertransition on cold wall and adiabaticat plates.
Journal ArticleDOI
Nonlinear equilibrium solutions in a three-dimensional boundary layer and their secondary instability
TL;DR: In this article, the authors used Floquet theory to study the dependence of the secondary, high-frequency instabilities on the saturation amplitude of the equilibrium solutions and found that the most amplified instability mode can be clearly traced to spanwise inflectional shear layers that occur in the wake-like portions of equilibrium solutions.