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Direct Numerical and Large Eddy Simulation of Stratified Turbulent Flows

Rahimi, Abbas,
http://orcid.org/0000-0002-9217-5785
http://rave.ohiolink.edu/etdc/view?acc_num=akron1429456746

Abstract Details

2015, Doctor of Philosophy, University of Akron, Engineering.
Oceanic and atmospheric flows have very large length and time scales, they also undergo intense vertical stratification with the consequence that the horizontal motions have larger scales compared to vertical motions. These effects make the simulation of geophysical flows very difficult, more challenging, and quite different from the simulation of manufacturing flows. Thanks to recent progress in computational technology, as well as, scientific availability of super computers, researchers can investigate some fundamental characteristics of these flows using direct numerical simulation (DNS) for relatively low Reynolds numbers $Re$. However, natural stratified turbulent flows represent very high turbulent intensity i.e. ${Re}\sim 10^6-10^8$ in geophysical flows, and $Re\sim 10^{10}-10^{12}$ in astrophysical flows. Therefore, with current computation limitations, it may take years to carry out simulation of these flows for very few eddies turn over time. To defeat this issue, researchers are inclined to apply large eddy simulation (LES) to resolve large energetic scales of motion and model subgrid scales of motion statistically. First, a code was developed to numerically solve Navier Stokes (NS) and scalar transport equations using pseudo-spectral method in a triple periodic box, and the code has been validated with the previously relevant DNS of weakly to strongly stratified decaying homogeneous turbulence. Also, numerous useful quantities, which help to describe these types of flows, are derived and discussed. Next, well-known subgrid-scale (SGS) turbulence models for large eddy simulations (LES), in presence of helical and non-helical stratified turbulent flows, are quantitatively assessed. Lastly, three new models based on the hybridization of concepts behind the SGS models, and the modified time scaling of Smagorinsky model for stratified turbulent flows has been proposed and tested. The new models show improvement in prediction of anistropy in turbulence which is initiated due to stratification.
Abhilash Chandy, Dr. (Advisor)
Kevin Kreider, Prof. (Committee Member)
Sadhan Jana, Prof. (Committee Member)
Alex Povitsky, Dr. (Committee Member)
Qindan Huang, Dr. (Committee Member)
Junliang Tao, Dr. (Committee Member)
185 p.
Civil Engineering; Mechanical Engineering; Meteorology
DNS, LES, Stratification, simulation

Recommended Citations

Citations

  • Rahimi, , A. (2015). Direct Numerical and Large Eddy Simulation of Stratified Turbulent Flows [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1429456746

    APA Style (7th edition)

  • Rahimi, , Abbas. Direct Numerical and Large Eddy Simulation of Stratified Turbulent Flows. 2015. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1429456746.

    MLA Style (8th edition)

  • Rahimi, , Abbas. "Direct Numerical and Large Eddy Simulation of Stratified Turbulent Flows." Doctoral dissertation, University of Akron, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1429456746

    Chicago Manual of Style (17th edition)

akron1429456746
1,162
© 2015, all rights reserved.
This open access ETD is published by University of Akron and OhioLINK.