Effect of Grid Topology and Resolution on Computation of Steady and Unsteady Internal Flows
Open Access
- Author:
- McHale, Steven Patrick
- Graduate Program:
- Mechanical Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- November 23, 2008
- Committee Members:
- Eric Paterson, Thesis Advisor/Co-Advisor
Eric G Paterson, Thesis Advisor/Co-Advisor - Keywords:
- openfoam
pulsatile
internal flow
grid topology
grid study - Abstract:
- Internal flow has been studied under steady and unsteady conditions. The work was motivated by previous research in canine olfaction which showed that the structure of the dog's nose consists of a highly complex pipe network in which the unsteady air flow transports odorant molecules to the sensory region. Due to geometric complexity of the canine turbinates, a body-fitted hex-dominant mesher was used, thus generating the question: What is the impact of grid topology and resolution on solution accuracy? The governing equations are defined and reduced to an analytical solution for a circular pipe with both steady and unsteady components. The numerical methods and solution algorithms are described. Simple test cases are performed using an open source computational fluid dynamics (CFD) code, OpenFOAM, to understand the underlying physics and computational challenges inherent in internal pipe flows. The characteristic steady, Poiseuille flow was found and a grid study was performed over a range of Womersley numbers (Wo) for the oscillatory, unsteady calculations of the straight pipe. It was shown that the Womersley number directly affects the amount of near wall resolution needed to accurately resolve the Stokes layer. The same calculations were also performed for two other grid topologies to compare the effectiveness of alternate grid types. The final simulations performed were steady inhalation/exhalation and unsteady respiration of a straight pipe within an external environment.