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Mechanical Engineering Seminar on 10/22/21 by Dr. Jing Wang, SDE Amazon Inc.

When: Friday, October 22, 2021
2:00 PM - 3:00 PM
Description: Mechanical Engineering (MNE) SEMINAR

October 22, 2021

2:00 p.m. - 3:00 p.m.

Charlton College of Business (CCB), Room 115

Dr. Jing Wang, SDE Amazon Inc.

Deformation of a Compliant Wall in a Turbulent Boundary Layer

The interactions between a compliant wall and turbulent or laminar boundary layer have been investigated extensively for over 60 years. Most of the studies are focused on turbulent drag reduction or noise suppression. With the development of 3D flow diagnostic techniques like tomographic PIV, or Shake-The-Box, it's able to measure the 3D flow including 3D velocities and 3D pressure field coupled with the compliant surface deformation. Among them, 3D pressure is difficult to measure directly and is forcing the deformation, thus, it's calculated indirectly from 3D velocities. In this talk, I will first present a robust and accurate GPU-based method for direct integration of velocity field to obtain the 3D pressure. This method is applied to the experiment of turbulent channel flow over a compliant surface. The experiment utilized a relatively stiffer compliant wall with Young's modulus of 1 Mpa and had a center-line flow speed (Uc) of 2.5 m/s. The resulting deformation amplitude is too small (20 nm) to affect the near wall flow field, thus a one-way coupling between the flow and the deformation is observed. The deformation has two modes, the fast mode move with Uc and slow mode is advecting at 0.72Uc. Statistics show the positive slow mode deformation is correlated with low pressure which resides in a vortical structure and the negative deformation is located at sweep ejection transition where there is a high pressure. Aiming at revealing the two-way coupling of deformation and turbulent boundary layer, we redesigned the experiment based on the Chase (Chase 1991) model prediction. Careful selections of freestream velocity (U0 = 6.0 m/s) and compliant surface Young's modulus (180 kPa) ensures the deformation amplitude is comparable to the wall unit. In this experiment, a spanwise propagating deformation mode which is aligned in the streamwise direction is observed. This mode does not move with the flow and seems to be associated with the shearr wave. Another mode of deformation advects downstream with 0.66U0 and is preferentially aligned in the spanwise direction. Different with turbulent flow over a rough wall, the near wall velocity profile showing a sharp increase of velocity gradient at 10 wall units. These findings are consistent with recent DNS results by Rosti and Brandt (2017).

Dr. Jin Wang received his Bachelor of Science at University of Science and Technology of China in 2012. Then he moved to Johns Hopkins University to pursue his PhD degree in Whiting School of Engineering under the supervision of Professor Joseph Katz focusing on flow diagnostics and turbulent flow over compliant surfaces. Dr. Wang received his PhD degree in 2019.

For more information please contact Dr. Hangjian Ling, MNE Seminar Coordinator (

All are welcome.

Students taking MNE-500 are REQUIRED to attend!

All other MNE BS and MS students are encouraged to attend. EAS students are encouraged to attend.

Thank you,

Sue Cunha, Administrative Assistant
Department of Mechanical Engineering
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