Evaluation of Pressure Field Estimation From Measured Velocity Fields, With Application to Tip Vortex Flows

Open Access
- Author:
- Sinding, Kyle Matthew
- Graduate Program:
- Engineering Science and Mechanics
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- December 04, 2018
- Committee Members:
- Michael H Krane, Dissertation Advisor/Co-Advisor
Judith Todd Copley, Committee Chair/Co-Chair
Francesco Costanzo, Committee Member
Michael H Krane, Committee Member
Stephen P Lynch, Outside Member
Jeff R Harris, Special Member
John Dabiri, Special Member - Keywords:
- Pressure Estimation
Tip Vortex
Error propagation
Stereo Particle Image Velocimetry
Measured Velocity Fields
Pressure Fluctuations - Abstract:
- This dissertation introduces a framework to compare existing pressure estimation techniques to determine the influence of boundary conditions, velocity error profile, error magnitude, and domain size on propagation of error from the velocity field to the pressure solution. The framework utilized in this study is used to select the best pressure estimation technique. Next, the best pressure estimation technique is applied to LES data to confirm the accuracy of the pressure estimation for tip vortex flows, evaluate the impact of the velocity statistics and vortex characteristics on the pressure estimates, and determine the appropriate spatial resolution requirements of the velocity field measurements. The pressure estimation tool is then applied to instantaneous velocity realizations from stereo PIV of a tip vortex flow to determine core pressure fluctuations. Many factors contribute to the propagation of error from the velocity field to the pressure estimate. A complete understanding of these factors is required to understand how the uncertainty of the measured velocity field propagates into the pressure estimation. The application of the pressure estimation technique is ultimately intended to predict the onset of tip vortex cavitation which is a source of noise, causes damage, and decreases efficiency in many naval applications. The goal of the current research is to provide a framework to determine the best pressure estimation technique and provide a method to evaluate error bounds in the estimated pressure field. Further this dissertation aims to apply the pressure estimation technique to a tip vortex flow in order to characterize the vortex core pressure fluctuations. Previous comparisons of pressure estimation techniques have focused on the effects of resolution, noise magnitude, method of calculating the source term, boundary conditions, or error profile, but have not studied the interdependence of these factors to effect the propagation of error into the pressure solution. Cavitation calls and seven-hole pressure probes have been used to study the pressure in a tip vortex in an average sense. The minimum pressure coefficient in a tip vortex has been estimated from time averaged fields and fluctuations have been estimated using the turbulent kinetic energy, but no studies have investigated instantaneous pressure fields of a tip vortex. This study provides a comparison between four existing methods to determine how boundary conditions, error profile, error magnitude, and domain size effect the propagation of error to the pressure field in order to determine the best pressure estimation technique for application to a tip vortex flow and bound the error of a pressure estimation. This study also conducts high speed SPIV of a tip vortex in order to characterize vortex structure and employs the pressure estimation technique to compare the estimated pressure fluctuations to the pressure fluctuations from the turbulent kinetic energy. The framework presented in this study can be used to determine the best pressure estimation technique for a given application. The insight into the unsteady pressure fluctuations can be used to predict cavitation inception and by marine vehicle designers to produce more efficient lifting surfaces.