Fluctuating Shear Stress Calibration Method Using a Channel Flow

Open Access
Author:
Cole, Daniel Clifton
Graduate Program:
Mechanical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
March 04, 2011
Committee Members:
  • Michael Lester Jonson, Thesis Advisor
  • H J Sommer Iii, Thesis Advisor
  • Kendra V Sharp, Thesis Advisor
Keywords:
  • fluctuating shear stress
Abstract:
An oscillating plate test facility was designed for the unsteady calibration of a skin-friction shear stress sensor in a liquid. The facility is comprised of a test section with dimensions of 5 mm by 60 mm by 300 mm, with a 48 mm by 25 mm oscillating plate in one wall. The oscillating plate is actuated by an electric motor coupled with an 18-lobed sinusoidal path cam and follower system, which allows oscillation of 1 mm amplitude at frequencies between 10 and 1000 Hz. Glycerin is used as the working fluid. Three actuator configurations are designed and built, and acceleration data is taken for the motion of each. In addition to the test facility design, a full three-dimensional solution to the flow velocity and shear stress inside the test facility is presented. This solution is based on a modification to Stokes' second problem; finite length and width of the oscillating plate are assumed. The work is robust enough that it is theoretically possible to start from a given shear stress distribution and back-calculate a plate configuration and motion description. A one-dimensional unsteady heat transfer solution is also described in detail herein. This solution accounts for the heat generated by the plate oscillation and its effects on glycerin viscosity. Complete comparison between the theoretical and experimental shear stresses was not achieved because of excessive vibrations from all three oscillating plate actuators. Acoustic waves are presented as possible reasons for the excess forces acting on the calibration device. Further work is required to verify that the shear stress generated by the oscillating plate can be fully modeled by the theoretical solution.