Bulletin of the American Physical Society
Far West Section Fall 2021 Meeting
Volume 66, Number 12
Friday–Saturday, October 29–30, 2021; Virtual
Session M02: Astro and Grav and Applied Physics -2 |
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Chair: Gerardo Dominguez, California State University, San Marcos |
Saturday, October 30, 2021 11:00AM - 11:12AM |
M02.00001: A Simulation Study of the Interaction of a Blasius Boundary Layer with a Roughness Element Ian Sysyn, Patrick Bonner, Frank Jacobitz, Jonathan Lemarechal, Marco Costantini Roughness elements on surfaces of transportation systems can contribute to the transition from laminar to turbulent flow, impacting the overall energy requirements due to increased drag, and improving the stability of lift forces. The present study considers the interaction of a Blasius Boundary Layer developing on a flat surface with a cylindrical roughness element of small aspect ratio and a height smaller than the local boundary layer thickness. Using Ansys CFD, the development of a horseshoe-shaped vortical structure around the roughness element as well as a recirculation zone directly downstream of the roughness element is observed. The simulations aim to reproduce previous experiments (J. Lemarechal et al., 2018) visualizing the flow structure through the use of temperature-sensitive paint (TSP) applied to a heated surface. The simulations and experiments qualitatively show the same vortical flow structure. A direct comparison of the surface temperatures in the roughness element’s wake region yields a correlation coefficient of 0.85, also indicating strong quantitative agreement between simulations and experiments. The temperature signature is also a good indicator for regions of high wall shear stress. due to the horseshoe-vortex. [Preview Abstract] |
Saturday, October 30, 2021 11:12AM - 11:24AM |
M02.00002: Unmanned Aerial Systems Guidance and Control Utilizing Instantaneous Screw Motion Invariants Jasur Abdinabiev, Dilmurat Azimov The purpose of this research is to study the application of the concept of instantaneous screw motion (ISM) to unmanned aerial vehicle (UAV) dynamics, guidance, and control. The proposed approach to the utilization of this concept in flight dynamics is based on the ISM invariants. The equations of motion of the instantaneous screw axis (ISA) are presented. Thrust and angle of attack are considered as the control parameters. The motion invariants are determined in terms of the traditional kinematic and dynamic parameters by using the dynamic models of a quadcopter and a fixed-wing aircraft. The profiles of the invariants for various maneuvers of the UAVs are determined in terms of time and control parameters. Various characteristics of the ISM invariants and their profiles have been explained. Illustrative examples of utilizing these invariants in the analyses of motion dynamics and control are presented. [Preview Abstract] |
Saturday, October 30, 2021 11:24AM - 11:36AM |
M02.00003: Explanation of the nature of black hole and its possible creation ways. Gh. Saleh, M. J. Faraji, R. Hashemizadeh Since black holes were discovered, scientists have been searching for their structure and ways of creation. By knowing that the density of a black hole is extremely high, like protons (10\textasciicircum 18 kg/m3), we can conclude that in a black hole there is a compact set of protons and neutrons that could create such a high density. Taking into account that a black hole has a surrounding area we should imagine that this area could be like a oceans of electrons, protons and neutrons. One can also imagine the black hole as a extremely large atom whose nucleus is made of protons and neutrons and the electrons revolving around it are ocean of electrons, protons and neutrons. In this paper we are going to explain more about this structure and we will introduce three possible ways in which the black holes could be created. [Preview Abstract] |
Saturday, October 30, 2021 11:36AM - 11:48AM |
M02.00004: Signatures of asymptotic symmetries in gravitational memory Shailesh Kumar, Srijit Bhattacharjee, Arpan Bhattacharyya The direct detection of the gravitational wave has enabled researchers to look for various aspects of black hole spacetimes; gravitational-wave memory (GW memory) is one of such effects which has not been detected yet. The memory effect manifests a permanent displacement in the spacetime, i.e., a relative change in the position of freely falling LIGO test masses. It has been shown that memory is related to the asymptotic symmetries of spacetimes originally discovered by Bondi-van der Berg-Metzner Sachs (BMS). From a theoretical perspective, recovering asymptotic symmetries near the horizon of black holes has become a matter of interest to the researchers as Hawking, Perry and Strominger conjectured that the charges corresponding to such symmetries would help to retrieve information in the information loss puzzle. Therefore, the memory effect must be well-studied in the context of asymptotic symmetries from theoretical as well as experimental standpoints. In this direction, I would focus on investigating some of these aspects by estimating measurable effects on the detectors after the passage of GWs. My aim would be to provide some theoretical features of the displacement memory effect near the horizon of black holes and its possible connection with near-horizon BMS symmetries. [Preview Abstract] |
Saturday, October 30, 2021 11:48AM - 12:00PM |
M02.00005: Defining a finite universe from a holographic horizon. Paul OBrien By combining Carl Schwarzschild's solution for BH mass and radius with Hawking's solution for the BH mass and temperature one can define both the initial and final condition of a finite Universe, (U); which conserves Mass, (M$_{u})$, Energy (E$_{u})$ and Quantum Information, (I$_{u})$ measured from a holographic horizon that contains the entire universe at some time (t) where (c$^{2}$t$^{2}) \quad =$ (R$^{2})$. Since (c) is a constant then (t$^{2})$ $=$ (R$^{2}) \quad =$ (M$_{u})$/(T). I will derive 4 equations that prove this. [Preview Abstract] |
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