Interaction of Isotropic Turbulence with an Actuator Disk

Speaker: Aditya Ghate, Stanford University
April 5, 2018

Presentation

Abstract

The interaction of a dragging, fixed thrust coefficient actuator disk with decaying homogeneous isotropic turbulence (HIT) of varying spatial length scales and dissipation rates is studied using Large Eddy Simulation (LES). In the first half of the talk, the deformation of the inflow turbulence as it enters the core, and the wake shear layer turbulence are characterized in detail. The strong sensitivity of the shear layer entrainment to the integral length scale of the incident turbulence (as opposed to its “intensity”) is explained in terms of excitation of low Strouhal number Kelvin-Helmholtz wave packets using a space-time modal decomposition (SPOD) of the pressure field. This ability of the SPOD in isolating shear layer turbulence from the incident/ambient HIT is used to motivate the second half of the talk when an algorithm to enrich large scale turbulence with consistent smaller scale turbulence is introduced. There two main advantages of representing finer scale turbulence using spatially localized Gabor modes: a) the Gabor-transformed sub-filter scale equations result in ODEs in time after appropriate modeling, and b) the representation of the fine scales is highly compressed due to efficient sampling in wavespace.

Biography

Aditya Ghate is a Ph.D. candidate in a Ph.D. candidate at Stanford University majoring in Aeronautics and Astronautics using the supervision of Prof. Sanjiva Lele. His thesis work has focused on subgrid scale enrichment in LES and stratified turbulence. His research interests include atmospheric turbulence, turbulence modeling and wind energy. Aditya received his master's degree in Aeronautics and Astronautics at Stanford University and bachelor's degree in Aerospace engineering from the University of Kansas.

Seminar Participation

Attending In Person

For select seminars, you may wish to attend in-person if you are in the vicinity of NASA Ames Research Center. These AMS seminars are held in Building N258 in Room 127, just off the front lobby. Sessions available to attend in-person will be indicated in the announcement information. In-person participants without NASA badges will need a valid visitor badge (US citizenship or permanent residency is required) to enter the facility.

Join Us Online

To attend an AMS seminar, click on the Microsoft Teams link in the seminar description. You can connect through the desktop Teams App if you have it, or you can select "Watch on the Web Instead" to enter the meeting as a guest. Please ensure that you've muted your microphone in Teams before you select "Join Now" to enter the meeting lobby.