Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session A31: Compressible Flows: General; Thermal Effects |
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Chair: Roy Baty, Los Alamos National Laboratory (LANL) Room: 255 C |
Sunday, November 24, 2024 8:00AM - 8:13AM |
A31.00001: Shock Interaction with a Contact Surface Roy S Baty In this work the classical problem of the interaction of a shock wave and a contact surface (or contact discontinuity) is analyzed using modern methods of infinitesimal analysis. A shock wave and a contact surface, defined on planar characteristics in space and time, are modeled as traveling waves in a one-dimensional, inviscid, ideal gas. The shock wave and the contact surface are represented by nonstandard Heaviside jump functions and are defined using infinitesimal analysis. For the case in which the shock wave is incident on a denser gas, it is shown that the interaction of the shock with the contact surface admits a solution that may be expressed using a third nonstandard Heaviside function that represents a shock wave reflected off the contact surface. Nonstandard analysis is applied to describe the jump functions and their derivatives. Nonstandard analysis is an area of modern mathematics that studies extensions of the real number system to number systems that contain both infinitesimal numbers and infinitely large numbers and provides a rigorous framework for infinitesimal analysis. It is assumed that the shock wave and contact surface thicknesses occur on idealized infinitesimal intervals and that the nonstandard jump functions in the thermodynamic and kinematic parameters vary smoothly across these idealized discontinuities. The equations of motion are cast in nonconservative form and applied to derive unambiguous relationships between the nonstandard jump functions and their products for the flow parameters in the regions surrounding the shock wave and the contact surface. |
Sunday, November 24, 2024 8:13AM - 8:26AM |
A31.00002: Shock Transmission Across a Low-Impedance Contact Surface Scott D Ramsey, Roy S Baty The classical problem of a shock wave incident upon a contact surface between two materials manifests a variety of flow patterns. These patterns are typically characterized through comparison of the shock impedance of the adjacent materials. For the case where a shock in a high-impedance material transmits into a low-impedance material, the wave reflected from the contact surface is a rarefaction wave. This work treats this classical problem using modern techniques of infinitesimal analysis rooted in nonstandard analysis. In this construction the time-dependent shock wave and contact surface trajectories are readily captured using idealized infinitesimal intervals defined on generalized number systems containing infinitely small numbers; within this representation the nonstandard jump functions in the flow and state variables may vary continuously. The reflected wave is characterized using this same technique, so that the notion of continuity in the infinitesimal sense must be reconciled with that in the global sense, as is expected for rarefaction wave structures. |
Sunday, November 24, 2024 8:26AM - 8:39AM |
A31.00003: Density reconstruction of interacting conical and detonator shocks using quantitative schlieren Jessica Cooke, Michael J Hargather Quantitative schlieren is a non-intrusive optical method which can be used to measure the refractive index fields which can be related to gas density via the Gladestone-Dale relationship. Quantitative schlieren was previously used to measure the air density around an axisymmetric supersonic conical projectile. Here the methods are extended to measure the density field around the axisymmetric supersonic projectile passing through an explosively driven shock wave. Ultra-high-speed imaging is utilized to capture time-resolved images of the projectile interacting with the explosively driven shock wave. Flow features of the intersecting shocks including the conical shock, detonation shock, and reflection waves are analyzed and compared to analytical and computational models. Methods for three-dimensional reconstruction are discussed along with the limitations of the axisymmetric assumptions. |
Sunday, November 24, 2024 8:39AM - 8:52AM |
A31.00004: Measuring the four fields in high-speed aerodynamics: Pressure, temperature and density from velocity using the Matrix Omnidirectional Pressure Integrator Fernando Zigunov With the introduction of full-field, 3D velocity measurement techniques and the recent developments in rapid and accurate solution of pressure from PIV in large 3D domains, it is now possible to obtain measurements of the remaining thermodynamic variables (temperature and density) exclusively from field velocity (PIV, PTV) measurements in complex domains, enabling the reconstruction of volumetric measurements that can usher new physical understanding of the topologies of complex, practical flows under highly compressible conditions. The development of the one-shot matrix-based omnidirectional pressure integrator (OS-MODI, Zigunov & Charonko, 2024) enables the reconstruction of large 3D domains with cropped boundaries in a few seconds on a consumer-grade graphics card, requiring no specification of boundary conditions except for a reference pressure at a node on the free stream. This opens new doors for reconstruction of all four field variables in a compressible fluid flow exclusively from PIV measurements. |
Sunday, November 24, 2024 8:52AM - 9:05AM |
A31.00005: Assimilation of wall-pressure measurements in DNS of Mach 6 flow over a cone-flare geometry Pierluigi Morra, Brett Tillman, Tamer A Zaki We perform ensemble-variational assimilation of wall-pressure measurements in direct numerical simulations of Mach 6 flow over a cone-flare. The experimental data are the pressure spectra and intensities at seven wall-mounted PCB sensors, distributed upstream, within, and downstream of the separation region that is established due to the corner shock. The assimilated flow captures the typical intense rope-like structures within the upstream attached boundary layer. A localized amplification of disturbances below the separation shock is predicted, which is not seen in the measurements due to the placement of the sensors. Additionally, the simulations show that the dynamics downstream of separation are the most difficult to predict, due to uncertainty caused in part by the low-frequency unsteady dynamics of the corner shock. This unsteadiness modulates the boundary-layer thickness and modifies the disturbance field. |
Sunday, November 24, 2024 9:05AM - 9:18AM |
A31.00006: Compressible flow over a heated cylinder with constant and temperature-dependent transport coefficients Ahmet F Kula, Man Long Wong, Denis Aslangil A flow over a heated cylinder is a strongly coupled heat transfer and fluid dynamics problem that arises in various engineering applications, such as hypersonic flight conditions, particle-fluid interactions, and re-entry problems. Due to the high-temperature variations observed in these flows, the constant fluid transport property assumptions may not be sufficient to capture the actual physics. This study compares constant and temperature-dependent (using a power-law with a power of 0.75) transport coefficient models where thermal conductivity and shear viscosity depend on the temperature for compressible flows over a two-dimensional cylinder using direct numerical simulations (DNS). For such comparison, we have performed DNS at different temperature ratios where the cylinder surface temperature is 1.2, 1.5, and 3.0 times larger than the free-stream flow temperature. In addition, we compare two Mach numbers with Reynolds numbers ranging from 20 to 150. It is observed that both models provide similar aerodynamic characteristics at the low-temperature ratio (1.2); however, the aerodynamic characteristics calculated for the two different models start to show significant differences when the temperature ratio is higher than 1.5. For example, the mean drag coefficient and separation angle are considerably larger for the cases where we account for temperature-dependent fluid transport properties compared to their counterparts with constant fluid transport properties. We also found that the heat transfer parameters, such as Nusselt number and total convective heat flux, of the problem become highly sensitive to the choice of the transport coefficient model even with low-temperature ratios, and the differences become more prominent with increasing temperature ratios. A detailed comparison of the effects of transport coefficient models on aerodynamics, heat transfer, and vortex dynamics will be presented. |
Sunday, November 24, 2024 9:18AM - 9:31AM |
A31.00007: Chemistry similarity in turbulent hypersonic boundary layers Donatella Passiatore, Mario Di Renzo Vehicles traveling at hypersonic speed experience intense mechanical and thermal stresses due to aerodynamic effects, which become significantly more severe as the flow transitions to turbulence. At high Mach numbers, the elevated temperatures trigger thermochemical phenomena, leading to the coupling of chemical dissociation with turbulent dynamics. |
Sunday, November 24, 2024 9:31AM - 9:44AM |
A31.00008: Aerothermal simulations of a multimaterial cone at Mach 22 Paul Poovakulam, Blaine Vollmer, Alessandro Munafo, Marco Panesi, Daniel J Bodony The ability to predict boundary layer transition is critical to obtaining an accurate estimation of heat transfer in hypersonic flows. Perturbation methods used to predict transition require a good base flow to provide correct results. This study uses a 2D axisymmetric simulation to model the re-entry of a 22-degree cone at Mach 22 and obtain a base flow for future stability analyses. A coupled approach is used, with a finite volume fluid solver (HEGEL) and a finite element ablative solid solver (CHyPS) connected using a coupling library (preCICE). HEGEL uses an 11-species air model and accounts for the NLTE (non-local thermal equilibrium) effects in the flow. CHyPS is used to model the thermal response of a multi-material cone composed of a graphite nose, quartz spacer and beryllium afterbody. The re-entry process is simulated and the results are validated by comparing flow parameters and cone surface temperatures to values from literature. |
Sunday, November 24, 2024 9:44AM - 9:57AM |
A31.00009: Multi-fidelity numerical study of heat augmentation on a hypersonic inflatable aerodynamic decelerator Ryan Zapp, Ivan Bermejo-Moreno We present a numerical investigation of the transitional flow and associated heat transfer augmentation experienced on the front of a hypersonic inflatable aerodynamic decelerator (HIAD) during atmospheric reentry. These simulations aim to replicate hypersonic wind-tunnel experiments conducted by Hollis (2018) for a scaled model geometry similar to the NASA Inflatable Reentry Vehicle Experiment (IRVE). The aerodynamic deflection experienced by a flexible sphere-cone aeroshell results in a large-scale roughness pattern following a scalloped axisymmetric shape, which induces earlier transition and increased heat transfer, affecting the design of the thermal protection system. We perform simulations at different freestream conditions of Mach number (M ≈ 6), Reynolds number (Re∞ ≈ 7×106 /m to 27×106 /m), angle of attack (0° to 18°), and for varying scallop (roughness) heights. Results from Reynolds-averaged Navier-Stokes (RANS) simulations using different turbulence models, as well as wall-modeled large-eddy simulations (WMLES) will be presented. |
Sunday, November 24, 2024 9:57AM - 10:10AM |
A31.00010: Plasma Formation in Ambient Fluid from Hypervelocity Impacts Kevin Wang, Shafquat Islam Ionization and plasma plumes have been detected in some hypervelocity impact experiments. However, knowledge of the plasma’s origin, composition, and energy is limited. We hypothesize that in atmospheric hypervelocity impacts, the ambient gas ionizes and contributes significantly to the plasma, despite the small amount of energy it receives. To test this hypothesis, we develop a fluid-solid coupled computational model that combines the multi-material compressible Navier-Stokes equations, a complete thermodynamic equation of state for each material, and a non-ideal, multi-species Saha equation for ionization prediction. Material interfaces are tracked using an extended two-equation level set method, and the interfacial mass, momentum, and energy fluxes are computed by the FIVER method. The impact of tantalum on soda-lime glass (SLG) within argon gas is simulated, with impact velocity varied between 3 km/s and 7 km/s. We show that for impact velocities above 4 km/s, ionization is clearly detected in both argon and SLG. The temperature and plasma density are both higher in the argon gas than in SLG and tantalum. In general, the results show that the plasma's density and energy depend on both impact velocity and the material combination, including the ambient gas. The plasma's composition further reflects the properties (e.g., ionization energies) of the chemical elements in each material. Acknowledgement: Office of Naval Research (ONR). |
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