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The Effect of Domain Length and Initialization Noise on Direct Numerical Simulation of Shear Stratified Turbulence
by
Vashkar Palma
Vashkar Palma 1,
Daniel MacDonald
Daniel MacDonald
Daniel MacDonald received his BSCE from the Univeristy of New Hampshire in 1992, his MS in Civil and [...]
Daniel MacDonald received his BSCE from the Univeristy of New Hampshire in 1992, his MS in Civil and Environmental Engineering from Cornell University in 1996, and his PhD in Oceanographic Engineering from the Massachusetts Institute of Technology/Woods Hole Oceanographic Institute Joint Program in 2003. Currently, he is a Professor with the Department of Civil and Environmental Engineering, University of Massachusetts Dartmouth. At UMass Dartmouth, Dr. MacDonald leads the Coastal Engineering and Fluid Mechanics Laboratory, which focuses research on a variety of areas related to coastal physics and engineering. His basic and applied research encompasses the areas of stratified hydrodynamics, turbulence and frontal dynamics—with specific emphasis on estuarine flows, river plumes, and industrial discharge. A significant research focus also lies in the area of renewable energy, including wave energy and the hydrodynamic aspects of other marine renewable technologies and conventional hydropower. He is also actively involved in the utilization of robotic platforms for environmental data acquisition in coastal and inland aquatic environments. Dr. MacDonald is a member of the American Society of Civil Engineers and the American Geophysical Union.
1,2,*
and
Mehdi Raessi
Mehdi Raessi
Mehdi Raessi is a Professor and Graduate Program Director with the Department of Mechanical of He BS [...]
Mehdi Raessi is a Professor and Graduate Program Director with the Department of Mechanical Engineering, University of Massachusetts Dartmouth. He received his BS degree in Mechanical Engineering from the University of Tehran in 1998 and his MS and PhD in Mechanical Engineering from the University of Toronto in 2003 and 2008, respectively. During his graduate studies, he worked at the Centre for Advanced Coating Technologies (CACT). Mehdi Raessi joined the University of Massachusetts Dartmouth in 2010 following postdoctoral studies at NASA–Stanford University's Center for Turbulence Research (CTR). Dr. Raessi's research is primarily focused on numerical simulations of interfacial flows and multi-phase flows with phase change. Using numerical simulations, he has been studying fluid flow and heat transfer in various applications, including energy systems (renewable and conventional), materials processing, and environmentally friendly refrigeration systems. In addition to academic research and teaching, Dr. Raessi has industrial experience as a research and development (R&D) specialist and applied engineer.
3
1
Department of Civil and Environmental Engineering, University of Massachusetts-Dartmouth, Dartmouth, MA 02747, USA
2
Department of Estuarine and Ocean Sciences, University of Massachusetts-Dartmouth, Dartmouth, MA 02747, USA
3
Department of Mechanical Engineering, University of Massachusetts-Dartmouth, Dartmouth, MA 02747, USA
*
Author to whom correspondence should be addressed.
Fluids 2024, 9(8), 171; https://doi.org/10.3390/fluids9080171 (registering DOI)
Submission received: 28 June 2024
/
Revised: 18 July 2024
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Accepted: 19 July 2024
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Published: 27 July 2024
Abstract
Direct numerical simulation (DNS) has been employed with success in a variety of oceanographic applications, particularly for investigating the internal dynamics of Kelvin–Helmholtz (KH) billows. However, it is difficult to relate these results directly with observations of ocean turbulence due to the significant scale differences involved (ocean shear layers are typically on the order of tens to hundreds of meters in thickness, compared to DNS studies, with layers on the order of one to tens of centimeters). As efforts continue to inform our understanding of geophysical-scale turbulence by extrapolating DNS results, it is important to understand the impact of model setup and initial conditions on the resulting turbulent quantities. Given that geophysical-scale measurements, whether through microstructures or other techniques, can only provide estimates of averaged TKE quantities (e.g., TKE dissipation or buoyancy flux), it may be necessary to compare mean turbulent quantities derived from DNS (i.e., across one or more complete billow evolutions) with ocean measurements. In this study, we analyze the effect of domain length and initial velocity noise on resulting turbulent quantities. Domain length is important, as dimensions that are not integer multiples of the natural KH billow wavelength may compress or stretch the billows and impact their energetics. The addition of random noise in the initial velocity field is often used to trigger turbulence and suppress secondary instabilities; however, the impact of noise on the resulting turbulent energetics is largely unknown. In this study, we conclude that domain lengths on the order of 1.5 times the natural wavelength or less can affect the resulting turbulent energetics by a factor of two or more. We also conclude that increasing the amplitude of random initial velocity noise decreases the resulting turbulent energetics, but that different realizations of the random noise field may have an even greater impact than amplitude. These results should be considered when designing a DNS experiment.
Share and Cite
MDPI and ACS Style
Palma, V.; MacDonald, D.; Raessi, M.
The Effect of Domain Length and Initialization Noise on Direct Numerical Simulation of Shear Stratified Turbulence. Fluids 2024, 9, 171.
https://doi.org/10.3390/fluids9080171
AMA Style
Palma V, MacDonald D, Raessi M.
The Effect of Domain Length and Initialization Noise on Direct Numerical Simulation of Shear Stratified Turbulence. Fluids. 2024; 9(8):171.
https://doi.org/10.3390/fluids9080171
Chicago/Turabian Style
Palma, Vashkar, Daniel MacDonald, and Mehdi Raessi.
2024. "The Effect of Domain Length and Initialization Noise on Direct Numerical Simulation of Shear Stratified Turbulence" Fluids 9, no. 8: 171.
https://doi.org/10.3390/fluids9080171
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