Bulletin of the American Physical Society
76th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2023; Washington, DC
Session J13: Shock-Boundary Layer Interactions II |
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Chair: Anne-Marie Schreyer, RWTH Aachen University Room: 143C |
Sunday, November 19, 2023 4:35PM - 4:48PM |
J13.00001: Effect of Shock Strength on the Unsteadiness of Mach 5 Shock/Boundary-Layer Interaction Using Fast-Response PSP and High-Speed PIV Yoo Jin Ahn, Marc Eitner, Jayant Sirohi, Noel T Clemens Shock/boundary-layer interaction (SBLI) is known to exhibit large-scale, low-frequency unsteadiness. There have been a number of candidates identified as the driving mechanism of the low-frequency shock unsteadiness. Some researchers have argued that whether upstream or downstream mechanisms dominate depends on the strength of the interaction. The current study is an experimental investigation that aims to investigate the upstream and downstream flow effects on the SBLI unsteadiness and to identify how the importance of different mechanisms differ at two different shock strengths. In this study, SBLI was induced by compression ramps of 28 and 26.5 degree in Mach 5 flow. For these flows, the mean separated flow length scales are 3.3 and 1., respectively. The surface pressure was obtained using 20 kHz fast-response pressure-sensitive paint (PSP) and the velocity field was measured using planar and tomographic particle image velocimetry (PIV). Various correlation analyses between the shock foot motion extracted from PSP and the pressure fluctuations will be shown. In addition, low-order reconstruction of the velocity field using proper orthogonal decomposition (POD) will be used to explore differences in the characteristic large-scale flow structures. |
Sunday, November 19, 2023 4:48PM - 5:01PM |
J13.00002: Fluid-Structure Interaction of a Planar Shock Impinging on a One Degree-of-Freedom Axisymmetric Body in Mach 5 Flow Benjamin E Diaz Villa, Marc Eitner, Yoo-Jin Ahn, Jayant Sirohi, Noel T Clemens The fluid-structure interaction resulting from an oblique shock impinging on a structurally-compliant slender axisymmetric model is experimentally investigated in a Mach 5 blowdown wind tunnel. The model is comprised of a 5-degree half-angle rigid cone attached to a rigid cylinder by using an elastic flexure element to provide one degree-of-freedom in the motion of the cone. The planar shock-wave is generated from a compression ramp upstream which induces a low-frequency unsteadiness from the turbulent shock-wave/boundary-layer interaction (SWBLI). This low-frequency oscillating shock interacts with the conical shock before impinging on the cone in what is known as a Type-I shock impingement. The low-frequency unsteadiness from the shock couples with the natural frequency of the elastic slender vehicle which is restricted to motion in one degree-of-freedom. Fast-response pressure-sensitive paint (PSP) will temporally resolve the pressure forcing on the cone while direct imaging enables tracking of its motion. In addition to the high-speed PSP, important flow characteristics on the surface will be compared between the compliant and the rigid model through surface oil flow. High frequency particle image velocimetry (PIV) will measure the velocity components of the shock impingement and its effects downstream caused by the interaction with the structural motion. |
Sunday, November 19, 2023 5:01PM - 5:14PM |
J13.00003: On low-frequency unsteadiness in swept hypersonic shockwave/boundary layer interactions Alessandro Ceci, Andrea Palumbo, Johan Larsson, Sergio Pirozzoli We present Direct Numerical Simulations (DNS) of hypersonic Shockwave/Boundary-Layer Interactions (SBLIs) in the presence of cross flow, as a computational surrogate of genuine three-dimensional SBLIs. We analyze the low frequency dynamics of the SBLI configurations and we characterize the temporal and spatial dynamics of the shock system. |
Sunday, November 19, 2023 5:14PM - 5:27PM |
J13.00004: Shock-induced turbulence amplification on a supersonic compression ramp: a DNS investigation Yujoo Kang, Sang Lee The turbulence amplification mechanism on the shock-turbulent boundary layer interaction (STBLI) using direct numerical simulation (DNS) is investigated. The STBLI is generated by a compression ramp at an inflow Mach number of 2.9. An in-house code based on a compact finite difference scheme for solving compressible flow has been developed and extensively validated using experimental and existing DNS data. The turbulent kinetic energy (TKE) distribution analysis reveals two distinct hotspots and in which the second TKE peak is located within the shear layer near the reattachment point. An investigation of the power spectral density of the pressure at the second TKE hotspots reveals the presence of mid-frequencies characteristic, indicating a secondary shock dynamic behavior. The amplification of turbulence at the second hotspot is found to be influenced not solely by the free shear layer, but rather by the mean flow deceleration attributed to the secondary shock. Detailed TKE budget analysis provides that the turbulence production due to the velocity gradient is notably greater around the second TKE hotspot, and intriguingly, the strongest production region is slightly displaced above the actual TKE maximum region. Furthermore, our findings indicate that the transfer of the turbulent energy is primarily influenced by transport through velocity fluctuation and pressure-velocity gradient interaction, serving as the dominant mechanism for the formation of the TKE maximum region. |
Sunday, November 19, 2023 5:27PM - 5:40PM |
J13.00005: Kinetic Modeling of Traverse Jets in Hypersonic Flow Over a Cone IRMAK TAYLAN KARPUZCU, Deborah A. Levin The interaction of a side jet with incoming hypersonic flows at M=6 and M=12 has been modeled using direct simulation Monte Carlo (DSMC). The geometry is a 7 half angle cone that has been used in several experimental studies in the literature. The presence of the jet creates several shocks, shear layers and recirculation zones and it is observed that in these shocks and shear layers continuum breakdown occurs. In addition to these high gradient layers, continuum breakdown occurs within the jet expansion itself which strongly affects the interaction region. The presence of continuum breakdown even though free stream conditions are continuum suggests the use of a kinetic method such as DSMC. We observe many of the classical shock structures that are discussed in the literature for both Mach numbers. The presence of the jet causes the drag force and heat transfer to decrease and normal force to increase in all cases. The interaction of shocks, shear layers and boundary layer causes unsteadiness in the shock system. The frequencies related to this unsteadiness were found to agree with those in the literature which increase with Mach number but are mostly insensitive to the Reynolds number. It is also observed that this low frequency unsteadiness in the shock system causes the local surface properties to be unsteady with very high fluctuations especially near shock interaction and separation regions. |
Sunday, November 19, 2023 5:40PM - 5:53PM |
J13.00006: Centrifugal Instabilities in a Shock-Separated Flow over a Hollow Cylinder-Flare Vishal Bhagwandin, Pino Martin Priebe and Martin JFM 2012 used Direct Numerical Simulation (DNS) of a Mach 3 24 compression ramp to show that the unstable shock motion is associated with an inviscid instability. Priebe, Tu, Martin and Rowley JFM 2016 reconstructed the flowfield using Dynamic Mode Decomposition and showed a pair of counter-rotating vortical instabilities generated near separation and developing downstream. Martin, Helm and Gonzalez-Kosasky APS 2016 visualized the instability on a Mach 7 33 case. Helm and Martin JFM 2021 and PRF 2022 extended the findings to Mach 10 with Wall-Resolved Large-Eddy Simulation (WRLES), and Helm and Martin PRF 2021 explored the flow scaling using experimental, DNS and LES data. Here, we investigate the flow on a Mach 10 hollow cylinder with flare using WRLES. Spectra and low-pass filtered turbulent fields are used to identify the streamwise centrifugal instabilities. The effect of three-dimensional relaxation due to the spanwise curvature of the flare on the extent of flow separation and the strength of the centrifugal instabilities is characterized. The resulting impact on pressure and heat transfer is also presented. |
Sunday, November 19, 2023 5:53PM - 6:06PM |
J13.00007: Forced Separation Unsteadiness in a Sharp Fin Induced Shock-Wave / Boundary-Layer Interaction Haryl Ngoh, Jonathan Poggie Using detached eddy simulations, unsteady perturbations were injected into the incoming boundary layer of a Mach 2, sharp-fin induced shock-wave / boundary-layer interaction to explore flow control of the separation unsteadiness. Analysis of the baseline flow showed that the separation shock fluctuated at a lower frequency range and amplitude, compared with the unsteadiness of the separation position. From the baseline data, an artificial upstream time-periodic body force was designed using profiles of the streamwise velocity perturbations in the incoming boundary-layer, which were conditionally averaged based on the separation position. Simulations with forcing showed that both the frequency and spanwise form of the forcing had significant effects on the separation unsteadiness. The responses of the separation shock and separation position were generally dissimilar. These responses were strongest with a forcing frequency representative of the baseline separation shock unsteadiness, and with a particular spanwise form that accounted for the mean spanwise flow near separation. These results demonstrate that the separation unsteadiness of the sharp-fin flow can be modulated by upstream forcing of a certain form, and highlight potential flow control strategies for this flow. |
Sunday, November 19, 2023 6:06PM - 6:19PM |
J13.00008: Wall thermal effects in wall-modeled and wall-resolved large-eddy simulation of compressible flows Vanessa Rubien, Ivan Bermejo-Moreno High-fidelity numerical simulations are performed to investigate the impact of wall temperature on shock wave-induced flow separation. The numerical methodology employs an unstructured-mesh, finite-volume, second-order shock-capturing LES flow solver. We conduct wall-resolved large-eddy simulations (WRLES) and wall-modeled large-eddy simulations (WMLES), comparing both to a direct numerical simulation (DNS) study by Bernardini et al. (2016) of a Mach 2.28 oblique shock-turbulent boundary layer interaction (STBLI) over a wall at cooled, adiabatic, and heated thermal conditions. An experimental study by Debiève et al. (1997) investigating Mach 2.3 flow over a flat plate subjected to changes in wall temperature provides an additional validation case for thermal effects in our WMLES simulations. We investigate the impact of several modeling parameters, such as the turbulent Prandtl number of the subgrid-scale and wall models, on the simulation results and evaluate the adequacy of various mean velocity profile transformations in the compressible flow regime. Results from WRLES and WMLES are compared, assessing how each simulation method performs against the reference data in the prediction of thermal transport, boundary layer separation, and unsteady low-frequency STBLI motions. |
Sunday, November 19, 2023 6:19PM - 6:32PM |
J13.00009: Mapping the Three-Dimensional Flowfield in Double-Fin SBLI Serdar Seckin, MyungJun Song, Fernando Zigunov, Farrukh S Alvi Shock-Wave/Boundary-Layer Interactions (SBLI), ubiquitous in most supersonic internal and external flows, pose major challenges in advancing super/hypersonic flight. Even simple geometries produce intricate SBLI flowfields that can have detrimental effects on the aerodynamics of high-speed air vehicles. Hence, an understanding of the underlying fundamental flow physics is imperative to effectively mitigate their adverse impact. In the present study, a crossing-shock induced by a Double-Fin (DF) SBLI is studied experimentally at Mach 2 and 3. This study explores the fully volumetric (3-dimensions, 3-components) mean flowfield topology of the DF interaction using a novel method, Scanning-Stereoscopic Particle Image Velocimetry (S-SPIV). S-SPIV is an innovative adaptation to SPIV, where the SPIV system is continuously traversed over the entire interaction region and reconstructed through spatio-temporal averaging of the instantaneous snapshots. This flowfield is highly three-dimensional and these direct measurements, first-of-a-kind for this flow, provide crucial insights into the interaction dynamics, identifying features and regions that are of interest from both fundamental and application perspectives. |
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