4:10 pm Presentation
“Compliant Surface Deformation under Turbulence”
Presented by YUHUI LU (Adviser: Prof. Katz)
Study of turbulence over compliant surface has been of considerable interest for decades since its first investigation on dolphin skins. Measurement techniques of surface deformation caused by pressure and shear near the wall using Mach-Zehnder Interferometry will be reviewed. Two models developed by Chase and Beschop enables us to predict surface deformation from pressure spectra using data from turbulence over rigid wall. Manufacturing process of compliant coating and a new chemical bonding method to avoid peeling when running at high speed flow around U~6m/s will be introduced. Also, progress of our new water tunnel under construction in Laboratory for Experimental Fluid Dynamics will be shown.
4:35 pm Presentation
“On the Response of a Turbulent Separation Bubble to Sinusoidal ZNMF Actuations”
Presented by WEN WU (Advisers: Profs. Meneveau & Mittal)
In this computational study the response of an adverse-pressure-gradient-induced turbulent separation bubble (TSB) to a continuous actuation is examined. The array of streamwise-elongated actuators are arranged to act as streamwise vortex generators. Direct numerical simulation is perform for the suction-only configuration at Re_theta=490, in which unsteady modes at three distinct frequencies are observed. The actuation is applied at both the lowest and highest natural frequencies of the TSB, as well as a much higher one that is ten times of the lowest natural frequency. The three disturbed cases are compared with each other and with the one without actuation. The differences in the mean flow and turbulent statistics can be explained by the formation of large-scale vortices by actuation.