Bulletin of the American Physical Society
2021 Joint Spring Meeting of the Texas Sections of APS, AAPT and Zone 13 of the SPS
Volume 66, Number 2
Thursday–Sunday, April 8–11, 2021; Virtual
Session A04: APS: Applied Physics and Engineering-I |
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Thursday, April 8, 2021 5:00PM - 5:12PM |
A04.00001: Nitsche-type Unfitted Fluid Structure Interaction Model Coupled with Material Point Method Erdi Kara, Eugenio Aulisa We propose a novel hybrid method that incorporates the Arbitrary Lagrangian-Eulerian (ALE)approach into material point method(MPM) for fluid-structure interaction(FSI) problems. In this formulation, fluid motion is described by Navier- Stokes equations formulated in ALE form. Variational formulation concerning the fluid is supported by the stabilizing residual-based variational multiscale(RBVM) method. Variational structural equations concerning the solid are assembled using MPM. We let fluid-solid interface cut the elements arbitrarily. To ensure well system conditioning and stability of the resulting system irrespective of how the interface intersects the cut elements, face-oriented ghost penalty stabilization is applied on the cut element faces. Continuity of velocities and normal stresses on the boundary is weakly enforced by the Nitsche's method. The advantage of our hybrid approach is that it provides a dynamic framework which eliminates certain shortcomings of ALE based finite element methods for fluid structure interaction problems involving large structural deformation. [Preview Abstract] |
Thursday, April 8, 2021 5:12PM - 5:24PM |
A04.00002: Measurement of Small-Scale Surface Velocity and Turbulent Kinetic Energy Dissipation Rates Using Infrared Imaging Shelby Metoyer, Mohammad Barzegar, Darek Bogucki, Brian Haus, Mingming Shao Short-range infrared (IR) observations of ocean surface reveal complicated spatially varying and evolving structures. Here we present an approach to use spatially correlated time series IR images, over a time scale of one-tenth of a second, of the water surface to derive underlying surface velocity and turbulence fields. The approach here was tested in a laboratory using grid-generated turbulence and a heater assembly. The technique was compared with in situ measurements to validate our IR-derived remote measurements. The IR-measured turbulent kinetic energy (TKE) dissipation rates were consistent with in situ--measured dissipation using a vertical microstructure profiler (VMP). We used measurements of the gradient of the velocity field to calculate TKE dissipation rates at the surface. Our future work seeks to expand the accuracy, resolution, and capability of such measurements by use of a deep convolutional neural network (DCNN). The DCNN will be trained with a direct numerical simulation (DNS) of the water surface and compared with our previous results. [Preview Abstract] |
Thursday, April 8, 2021 5:24PM - 5:36PM |
A04.00003: Insect flight velocity measurement with a CW near-IR Scheimpflug lidar system. Yiyun Li, Kai Wang, Rafael Quintero-Torres, Robert Brick, Alexei Sokolov, Marlan Scully Flight velocity measurement has attracted a significant interest since it can aid insect identification and facilitate studies and monitoring of insect behavior. We propose a novel scheme for the 1-D flight velocity measurement of insects, based on a near-IR Scheimpflug lidar system we established at Texas A{\&}M University. This new technique has been implemented and applied to study insects at the Salter Research Farm, Robertson County, Texas. The resolution property perpendicular to the probing direction of the Scheimpflug lidar system is explored and reveals the capability of retrieving the velocity component normal to the probing direction of insects passing through the field of view of our system. We observe a shift in wingbeat frequency, which indicates the presence of new insect species during the multi-day measurement. The study on 1-D flight velocity reveals a net directional movement of insects in the probing volume, providing supportive evidence of new species' arrival. [Preview Abstract] |
Thursday, April 8, 2021 5:36PM - 5:48PM |
A04.00004: Fluid Modelling of Plasma Sheaths with Thermionically Emitted Electrons Rupali Sahu, Albina Tropina, Richard Miles Leading edges of hypersonic vehicles are exposed to excessive thermal fluxes and need management of surface heating rates. Electron transpiration cooling (ETC) is a prospective and effective concept of thermal control of the leading edge temperature. The surface is covered by a low work-function material that emits electrons thermionically when heated. The emitted electrons take away some part of the energy that leads to a transpiration cooling of the surface of the hypersonic vehicle. Instead of thermionic emission to vacuum, the ambient air is partially ionized and a plasma sheath forms near the surface, which affects the emission of electrons through various phenomena like the space charge limited emission and the Schottky effect. Numerical studies are performed using a full fluid moment model of plasma to study plasma sheath behavior near such surfaces. The presence of counter-propagating streams of charged particles in the sheaths near emissive surfaces in addition to high wall biases tends to make the sheath simulation very sensitive to various physical and numerical instabilities. In this study, we analyzed the effect of the flux functions, boundary conditions, and Bohm criterion on the stability of plasma sheaths in the presence of the thermionic emission. [Preview Abstract] |
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