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At least 37 records · Page 2

Equivalent Source Method Applied to Launch Acoustic Simulations

Aeroacoustic simulations of the launch environment are described. A hybrid computational fluid dynamics (CFD)/computational aeroacoustic (CAA) approach is developed in order to accurately and efficiently predict the sound pressure level spectrum on the launch vehicle and surrounding structures. The high-fidelity CFD code LAVA (Launch Ascent and Vehicle Analysis), is used to generate pressure time history at select locations in the flow field. A 3D exterior Helmholtz solver is then used to iteratively determine a set of monopole sources which mimic the noise generating mechanisms identified by the CFD solver. The acoustic pressure field generated from the Helmholtz solver is then used to evaluate the sound pressure levels.

Housman, Jeffrey A.↗

Development of a Aerothermoelastic-Acoustics Simulation Capability of Flight Vehicles

A novel numerical, finite element based analysis methodology is presented in this paper suitable for accurate and efficient simulation of practical, complex flight vehicles. An associated computer code, developed in this connection, is also described in some detail. Thermal effects of high speed flow obtained from a heat conduction analysis are incorporated in the modal analysis which in turn affects the unsteady flow arising out of interaction of elastic structures with the air. Numerical examples pertaining to representative problems are given in much detail testifying to the efficacy of the advocated techniques. This is a unique implementation of temperature effects in a finite element CFD based multidisciplinary simulation analysis capability involving large scale computations.

Gupta, K. K.↗

Efficient three-dimensional Laplace-Fourier domain acoustic-wave simulations using discontinuous finite-difference meshes with embedded boundaries

© 2018 SEG. We develop embedded boundary and discontinuous mesh methods to handle arbirarily shaped topography and accurately simulate acoustic seismic wave propagation in Laplace-Fourier domain. The purpose of the embedded boundary method is to enhance accurate wave simulation near the surface and the discontinuous mesh method is used to achieve considerable savings in both computation time and memory savings relative to fixed mesh schemes.

AlSalem, Hussain↗

My Internship at NASA

My name is Isaac Lopez and I am a junior at the University of Houston majoring in Mechanical Engineering Technology. I will be completing my first tour at the NASA-Johnson Space Center ("JSC") as a Mechanical Engineer within the Human Interfaces Branch. Throughout my tour, I was given the opportunity to work on multiple projects that have expanded my knowledge and interest in acoustics and engineering design. One of the projects I worked on at JSC consisted of doing acoustic simulation of the EVA comm. cap. While working on the comm. cap headset, my main duty consisted of simulating the acoustics of the headset to find a solution to the condensing water that can accumulate and block the acoustic tube, causing attenuation or complete loss of audio in one ear for an astronaut using the EVA. For this project, I had to create a Creo model of the comm. cap so that I would be able to import it into Comsol for acoustic simulation. I also had the opportunity to design a portable and lightweight beam degrader for the EEE Parts and Radiation team. With the help of Creo, I was able to make a CAD design and put together a small working prototype for the radiation team to demonstrate the capabilities that the beam degrader had. In addition to these projects, JSC allowed me to work closely on projects with other interns. I had the opportunity to help another intern with his acoustic diverter, intended to improve the sound quality in Node 1 of the ISS. During this project, I helped with some of the acoustic testing inside the anechoic chamber as well as helping record data during testing at the ISS mock up. During the course of my first tour, I was able to learn and continually improve on my CAD drafting skills. With each project I worked on, I acquired new ways to create and improve various designs with various constraints. Furthermore, I also had the opportunity to work with electrical engineers and learn about the electronic components that would provide control of the beam degrader functions. I was able to take the knowledge, skills and designs I had acquired during my tour at JSC (such as Finite Element Analysis) and apply them to my work on the Comsol Multiphysics software for acoustics simulation. I was also able to use it to do some stress analysis on a proposed design for a proposed Habitat structure. My time at JSC has been invaluable as it helped me grow and more fully-comprehend my major as well as spark an interest in acoustics and how much it relates to mechanical engineering. This internship has taught me that engineering is much more than a profession - it is embedded in our daily lives as a puzzle that requires critical thinking as an everyday challenge that makes life more interesting.

Lopez, Isaac↗

Acoustic and turbulence measurements of a tone-excited jet with and without flight simulation

Acoustic as well as turbulence measurements were made of tone-excited jets to obtain an understanding of the broadband noise augmentation mechanism. Results for both heated and unheated jets with and without flight simulation are presented for a range of excitation frequencies and levels, as well as for the zero order and first order spinning modes. It is argued that although the phase-locked large-scale turbulence structure is at the root of the noise amplification process, the actual noise generation mechanism lies in the small-scale turbulence. Results show that (1) the phase velocity of the excited large scale instability waves is subsonic relative to the ambient fluid and (2) broadband jet noise is almost uniform at all frequencies. Moreover, when the large-scale and small-scale structures are plotted against forward velocity (for a given upstream excitation level of 141 dB), the change in large-scale turbulence is negligible with forward velocity, whereas the small-scale turbulence decreases for both excited and unexcited jets. Also, the corresponding difference in far-field noise does not appear to change significantly, indicating that the changes in small-scale turbulence are responsible for jet noise amplification.

Ahuja, K. K.↗