Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Fluid Dynamics
Volume 56, Number 18
Sunday–Tuesday, November 20–22, 2011; Baltimore, Maryland
Session D25: Supersonic and Hypersonic Flows 
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Chair: C.R. Truman, University of New Mexico Room: 328 
Sunday, November 20, 2011 2:10PM  2:23PM 
D25.00001: Respirable Particle Transport from Surfaces by Shock Waves C.R. Truman, P. Vorobieff, J. Conroy, P. Wayne, R. White, M. Anderson, S. Kumar Resuspension of particles from planar surfaces was studied in a shock tube. Respirable particles (aerodyn. diam.$\le $ 5 $\mu $m) and slightly larger nonrespirable particles were tested on smooth and rough surfaces at Mach 1.2 to 2.0. Particles of specified size were deposited on substrates of prescribed roughness. Surface roughness and particlesurface adhesion forces were quantified by atomic force microscopy. Alkylthiol self assembled monolayers (SAMs) were applied to precisely control surface roughness and surface chemistry. The advection of particles initially at rest on the surface by the rapidly accelerated flow were measured by Mie scattering. An ultrahighspeed digital camera with pulsed laser sheet illumination enables timeresolved particle transport diagnostics. Although particles are initially swept off a smooth surface with greater ease, cloud propagation speed is higher for a rough surface. At late times the cloud height is greater for a rough surface so that particles end up in a faster region of the boundary layer. Because our respirable and nonrespirable particle size distributions overlap, further study is required. Sheardriven KelvinHelmholtz vortices clearly visible in some images likely play a prominent role in particle transport. [Preview Abstract] 
Sunday, November 20, 2011 2:23PM  2:36PM 
D25.00002: DNS of a Hypersonic Shock Wave/Turbulent Boundary Layer Interaction Stephan Priebe, Justine Li, Pino Martin The direct numerical simulation of a hypersonic shock wave/turbulent boundary layer interaction (STBLI) generated by a 33degree compression ramp is presented. The fullyturbulent inflow boundary layer is at Mach 7.2, and the Reynolds number based on momentum thickness is $Re_{\theta}=3500$. The evolution of the mean and fluctuating field through the interaction region is investigated. In the supersonic regime, STBLI flows are known to display lowfrequency unsteadiness, typically at frequencies 12 orders of magnitude lower than the characteristic frequency of the incoming undisturbed boundary layer. Preliminary observations are made about the properties of the lowfrequency unsteadiness in the present hypersonic interaction. [Preview Abstract] 
Sunday, November 20, 2011 2:36PM  2:49PM 
D25.00003: Highspeed boundary layer transition induced by a discrete roughness element Prahladh Iyer, Krishnan Mahesh The effect of a hemispherical bump on a Mach 3.37 laminar boundary layer is studied using DNS for three conditions with $k/\delta=$ 2.54, 0.25 and 0.125, where $k$ is the roughness height. The simulation parameters are based on the experiment by Danehy {\it et. al.} (AIAA2009394). The flow downstream of the roughness is transitional for all the three conditions accompanied by a rise in skin friction and heat transfer. Upon interaction with the roughness element, the boundary layer separates to form a series of spanwise vortices upstream and a shear layer. These vortices wrap around the roughness to yield a system of streamwise vortices downstream. Perturbation of the shear layer due to the vortices results in the formation of hairpinshaped vortices further downstream of the roughness. While hairpin vortices were observed in both the center plane and offsymmetry planes on either side for the smallest $\delta$ case, they were observed only in the center plane for the other cases. [Preview Abstract] 
Sunday, November 20, 2011 2:49PM  3:02PM 
D25.00004: Velocity and Scalar Measurements of StrutBased Hypermixing Geometries in a Mach 3 Flow Ross Burns, Noel Clemens Strutbased fuel injection with hypermixing exhibits great potential as a fuelinjection strategy for future scramjet engine design. Hypermixing entails the introduction of strong streamwise vorticity by means of geometricallyinduced pressure gradients at the trailing edge of the strut; however, these complex flowfields are not well understood. An experimental investigation is being conducted on the flowfield characteristics of several strutbased hypermixers in a Mach 3 freestream. The hypermixing flowfields are generated from an injection pylon with interchangeable trailingedge geometries including compressive and expansive wedges. Particle image velocimetry (PIV) in conjunction with two scalar visualization techniques are used to obtain velocity and scalar field data. The scalar imaging techniques include twophoton absorption planar laserinduced fluorescence (PLIF) of krypton gas, which simulates fuel injection into the wake, and planar laser scattering (PLS) from condensed carbon dioxide fog, which marks the outer flow structures. The velocity and scalar data reveal details of the underlying flow physics as well as the turbulent mixing characteristics. [Preview Abstract] 
Sunday, November 20, 2011 3:02PM  3:15PM 
D25.00005: Thermal Loads on a Domed Protuberance Under a Mach 5.7 Boundary Layer Christopher Ostoich, Daniel Bodony, Philippe Geubelle A highfidelity, highaccuracy multiphysics computational tool has been developed to make predictions of structuralthermal response in the hypersonic regime. The predicted surface heat flux distribution was compared with measured data taken from a 1986 experiment in the NASA Langley 8foot hightemperature tunnel in which a flat plate with a domed protuberance was inserted into a Mach 6.59 flow. The solution from the fluid and thermal domains obtained from the coupled simulation, with experimental comparisons, will be presented. In addition to the typical heating associated with windwardfacing surfaces, several other sources of significant differential heating were observed near the domeplate interface and due to a trailing horseshoe vortex of small size. Data were collected over a long time record (50 seconds) and comments will be given about ignoring transient thermal effects in hypersonic boundary layer calculations. An assessment of gas thermal model assumptions will also be discussed. [Preview Abstract] 
Sunday, November 20, 2011 3:15PM  3:28PM 
D25.00006: Experimental Study of Supersonic Inlet Flow Unstart Induced by Mass Injection Hyungrok Do, Seongkyun Im, Mark G. Mungal, Mark A. Cappelli It is demonstrated that the boundary layer conditions of supersonic model inlet flows strongly affect the unstart that is induced by a transverse jet injection. Planar laser Rayleigh scattering from condensed CO$_{2}$ particles is utilized to visualize flow features. Studies conducted over a range of inlet configurations reveal that relatively thick turbulent boundary layers in asymmetric wall boundary layer conditions prompt the formation of oblique unstart shocks that facilitates fast inlet unstart. In contrast, thin symmetric boundary layers span pseudoshocks which appear to be quasistationary under some configurations. The unstart threshold is found to be sensitive to channel height and the relative concentration of injected CO2. We find that higher jet injection pressure can be accommodated with higher CO$_{2}$ concentration because of the heavier molecular weight of CO$_{2}$, and that unstart occurs at lower jet injection rates for smaller inlet model heights. [Preview Abstract] 
Sunday, November 20, 2011 3:28PM  3:41PM 
D25.00007: Unsteady Aspects of an Oblique Shock Reflection over a Heated Wall Vincent Jaunet, Pierre Dupont, JeanPaul Dussauge In supersonic flows, when an oblique shock wave impinges a boundary layer and makes it separate, strong aerodynamical loads at low frequency are created. This study aims at studying density effects on these structures by means of wall heating. Experiments are conducted at Mach 2.3. The temperature of the floor of the test section can be heated up to twice the recovery value. The interaction length is investigated through mean schlieren visualizations. It turns out that the interaction length increases of about 30\% between the adiabatic case and the heated one, whatever the adverse pressure gradient involved. Hotwire measurements are performed in the external flow in order to characterize the unsteadiness of the reflected shock. Results show that lower frequencies are involved in the heated case, in accordance with the Strouhal number of the interaction based on the interaction length $L$ and the external velocity $U_e$: $S_t=\frac{f*L}{U_e} \simeq 0.03$. [Preview Abstract] 

D25.00008: ABSTRACT WITHDRAWN 
Sunday, November 20, 2011 3:54PM  4:07PM 
D25.00009: Bifurcation of Scramjet Unstart Ik Jang, Joseph Nichols, Karthik Duraisamy, Parviz Moin We investigate the bifurcation structure of catastrophic unstart in scramjets. The bifurcation of quasionedimensional Rayleigh flow is first analyzed, followed by a numerical investigation of a more realistic model scramjet isolator (Wagner et al., AIAA paper, 2010). We show that the quasionedimensional model recovers a similar hysteresis behavior as that observed in steady ReynoldsAveraged NavierStokes simulations of the model scramjet isolator close to the onset of unstart. In the hysteresis zone, steady but unstable solutions are obtained by means of pseudoarclength continuation. Automatic differentiation permits the use of fully discrete Jacobians that result in an accurate representation of functional dependencies and linearized dynamics. Furthermore, we use an Arnoldi method to extract the least stable direct and adjoint eigenfunctions spanning the system dynamics close to unstart and obtain the system response to both harmonic and stochastic forcing. This information, along with the final bifurcation structure, allows us to evaluate the effectiveness of different metrics as indicators of the onset of unstart. [Preview Abstract] 
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