Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session S05: Compressible Flows: Shock Interactions |
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Chair: Dale Pullin, Caltech Room: 204 |
Tuesday, November 26, 2019 10:31AM - 10:44AM |
S05.00001: Evolution of perturbed planar shock waves Dale Pullin, Naijian Shen, Ravi Samtaney, Vincent Wheatley We consider the evolution of a planar gas-dynamic shock wave subject to smooth initial perturbations in both Mach number and shock-shape profile. A complex-variable formulation for the general shock motion is developed based on an expansion of the Euler equations proposed by Best [\textit{Shock Waves}, \textbf{1}, 4, (1991)], The zeroth-order truncation of Best's system corresponds to the equations of Whitham's geometrical shock dynamics (GSD) while higher-order corrections provide a hierarchical description that can be closed at any order, as detailed initial flow conditions for the flow immediately behind the shock are prescribed. Solutions to the first- and second-order closure of Best's system for the evolution of planar perturbations are explored numerically to investigate the development of a finite-time singularity in the shock shape profile. Results are compared to those obtained using GSD [Mostert \textit{et al.}, \textit{J. Fluid Mech.}, 846, (2018)]. [Preview Abstract] |
Tuesday, November 26, 2019 10:44AM - 10:57AM |
S05.00002: Image processing and edge detection techniques to quantify regular to irregular shock wave transition obtained from experiments Lingzhi Zheng, Benjamin Katko, Barry Lawlor, Claire Mcguire, Jane Zanteson, Kevin Nguyen, Veronica Eliasson Experimental studies of multiple shock wave interaction to study transition from regular to irregular reflection rely on the processing of a large amount of schlieren photographs. Here we present an automated algorithm to track individual shock fronts and triple points. First, correction to any optical distortions is applied to the photographs. Next, noise removal and edge detection algorithms are implemented to extract the pixel locations of the shocks. The edge detection algorithm takes advantage of shock waves' light intensity feature to distinguish shock fronts from background noise. This algorithm is also capable of separating entangled shock fronts through pattern recognization, which utilizes a discretization method to reduce complex shock geometries to localized linear patterns. Collectively, the algorithms can track shock wave characteristics to sub-pixel precision. Extractable characteristics include positions and propagation velocities of shock fronts, vertical and horizontal velocities of the Mach stem, and triple point trajectories during shock interactions. This algorithm can process large volumes of data with minimal manual operations, making image processing more efficient and productive. [Preview Abstract] |
Tuesday, November 26, 2019 10:57AM - 11:10AM |
S05.00003: On the Use of Non-Staggered Central Schemes for Large Eddy Simulation of the Canonical Shock-Turbulence Interaction Rozie Zangeneh The objective of this study is to investigate the ability of the semi-discrete, non-staggered central scheme to capture the shock with adequately low dissipation for the minimum influence of Large Eddy Simulation (LES) of turbulent flows. To this end, high-resolution LES simulations are performed to study the interaction of a stationary shock with fully developed turbulent flows. The presence of discontinuities, such as shocks and contact surfaces, in high-speed compressible flows with interactions of shear driven turbulence, requires dissipation numerical schemes that can capture flow discontinuity at the shock while capturing broadband spatial and temporal variations in a turbulent flow suggests the use of high-bandwidth schemes with minimal dissipation and dispersion. The existing methods such as ENO, WENO, and RKDG method typically involve Riemann solvers, characteristic decomposition and Jacobian evaluation, making them complex and difficult to implement in a collocated polyhedral framework. Here, a central scheme which developed by Nessyahu and Tadmor is introduced as an alternative approach for an accurate, non-oscillatory solution which unlike the existing methods, does not involve Riemann solvers or characteristic decomposition, therefore can avoid Jacobian evaluation. [Preview Abstract] |
Tuesday, November 26, 2019 11:10AM - 11:23AM |
S05.00004: Phase Analysis of Disturbances within Transitional Shock Boundary Layer Interactions. James Threadgill, Jesse Little Two-dimensional laminar/transitional Shock Boundary Layer Interactions (SBLIs) have been investigated to assess the influence of Reynolds number and interaction strength, and to probe unsteadiness mechanisms. SBLIs are induced by various ramps (15$^{\circ}$~\textless $~\theta $~\textless ~28$^{\circ})$ mounted to a flat plate in Mach 4 flow (Re/$L$~$=$~4.6$\times $10$^{\mathrm{6}}$ m$^{\mathrm{-1}})$ at various locations (1.2$\times $10$^{\mathrm{5}}$~\textless ~Re$_{x}$~\textless ~2.5$\times $10$^{\mathrm{5}})$. Oil-flow visualization and high-speed schlieren (50~kHz) have been employed to characterize the flow. The naturally laminar incoming boundary layer experiences significant separation within the SBLI (24~\textless ~$L$/$\delta_{0}$~\textless ~40). Strong SBLIs with high Reynolds numbers initiate transition within the elongated separated shear layer, promoting unsteadiness. Low-frequency separation shock motion is observed, similar to strong turbulent SBLIs (St$_{L}$~$\approx $~0.03). This motion is incoherent with all upstream features, supporting claims of a downstream mechanism driving SBLI unsteadiness. Phase analysis shows that the reattachment shock motion precedes the shear layer which precedes the separation shock motion. In addition, an upstream propagating convective density disturbance was identified within the separated flow ($u$~$\approx $~-0.2$u_{\infty })$ which directly influences subsequent motion of the separation shock. These observations provide vital input when characterizing complex turbulent unsteady SBLI mechanisms. [Preview Abstract] |
Tuesday, November 26, 2019 11:23AM - 11:36AM |
S05.00005: A Compression - Ramp Shock/Boundary-Layer Interaction Over a Compliant Panel at Mach 5 Mustafa Musta, Leon Vanstone, Marc Eitner, Jayant Sirohi, Noel Clemens A compression ramp induced shock wave/boundary layer interaction over a rigid and compliant surface was studied in a Mach 5 flow using high-speed stereo digital image correlation (DIC) and high-speed pressure-sensitive paint (PSP). The compliant panel, made of polycarbonate, is 2 mm thick and gives a fundamental first three mode frequency of about 700, 949, and 1350 Hz. The compression ramp, located at the downstream end of the compliant panel, is the compression angle of 28-degree compression ramp with 1-inch fence distance. The DIC will give time-resolved measurements of the displacement of the compliant panel, and the PSP will give the surface pressure over the entire panel. The simultaneous high-speed pressure and displacement measurements will allow analyzing the structural response of the compliant panel, flow unsteadiness, and the shock-foot in frequency and the time domain and compare with the rigid panel case. [Preview Abstract] |
Tuesday, November 26, 2019 11:36AM - 11:49AM |
S05.00006: Thermally driven unsteadiness of Shock Boundary Layer Interaction Sang Lee, Brian Romero, Tonghun Lee Deficiencies still remain in understanding the unsteadiness associated with the shock interacting with the incoming turbulent boundary layer flow exposed to thermal variation which is caused by the difference in the wall temperature and that of the ambient flow. The present study examines the effects of wall temperature on the dynamics of the unsteady separation bubble in a shock boundary layer interaction region at various Mach numbers. High order numerical simulations of a compression ramp are validated with existing experimental and numerical data at low Mach numbers, then various ratios of wall temperature to recovery temperature are investigated for increasing Mach numbers. [Preview Abstract] |
Tuesday, November 26, 2019 11:49AM - 12:02PM |
S05.00007: Predictability of wall-modeled large-eddy simulation for shock wave/turbulent boundary layer interacting separated flows Yuma Fukushima, Soshi Kawai In this talk, we first discuss the important flow features (such as separation and reattachment) of the shock wave and turbulent boundary layers interaction based on wall-resolved large-eddy simulation (WRLES) database. By using the WRLES database, we then investigate the capability of the wall-stress-model-based equilibrium and non-equilibrium wall-modeling in LES [Kawai and Larsson, PoF 2012, 2013] for predicting the boundary layer separation and reattachment induced by a strong pressure gradient of the shock wave. In this study, we focus on non-equilibrium terms in the streamwise momentum equation (pressure gradient and convection terms) that are important in the flow separation and reattachment and investigate how these terms are treated in the wall-modeled LES (WMLES). We also discuss the WMLES of transonic airfoil buffet phenomena at high Reynolds number, where the unsteady shock wave induces the separation and reattachment. [Preview Abstract] |
Tuesday, November 26, 2019 12:02PM - 12:15PM |
S05.00008: Direct numerical simulations (DNS) to study the effect of particle motion and Reynolds number on the drag force during shock-particle interactions Yash Mehta, Jonathan D. Regele The large disparity between length and time scales associated with explosive dispersal of particles makes the numerical study of these flows extremely challenging. With the recent availability of large-scale computational resources, the number of particle-resolved studies are increasing but most neglect particle motion, viscous effects or both. In the present study, we are interested in studying the effect of viscosity as well as motion on the drag forces experienced by a cluster of spherical particles during shock interaction. We are also interested in studying the anomalous drag reported by Bordoloi et al. (JFM Rapids 2017) in their experiments of a shock interacting with a dilute cloud of micro-particles. Towards this end, as a first step, we perform a direct numerical simulation of a spherical particle under shock-wave loading by solving the Navier-Stokes equations. We use an adaptive wavelet collocation method solver with volume penalization IBM for the particles.LA-UR-19-27293 [Preview Abstract] |
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