Type of Document Master's Thesis Author Betts, Juan Fernando Author's Email Address firstname.lastname@example.org URN etd-41898-17429 Title Finite Element Study of Plane Wave Acoustic Phenomena in Ducts Degree Master of Science Department Mechanical Engineering Advisory Committee
Advisor Name Title Knight, Charles Eugene Committee Chair Burdisso, Ricardo A. Committee Member West, Robert L. Jr. Committee Member Keywords
- Finite Elements
Date of Defense 1998-04-29 Availability unrestricted AbstractThis thesis studied the finite element modeling of plane wave acoustic phenomena
in ducts. The study looked into finite element factors such as shape functions, mesh
refinement, and element distortion.
The study concluded that the higher order shape function eight-node quadrilateral
element gave considerably better results than lower order shape function four-node
quadrilateral element. The eight-node element converged much faster to the analytical
solution than the four-node element. The average error, taking all the cases in
consideration, for the four-node element was around 30 % for a mesh refinement of about
14 elements per wavelength at 100 Hz frequency. The eight-node element in the other
hand had average absolute errors of less than 1% under the same conditions.
This section also found that the eight-node element was substantially more
resistant to solution deterioration due to element distortion than the four-node element.
For example distorting the four-node element up to 60* degrees usually increased errors
very rapidly to above 100 % errors. The eight-node element on the other hand usually
produced errors of less than 5 % for the same level of distortion.
The study showed that the type of boundary condition used had a significant
effect on the solution accuracy. The study demonstrated that the effect of the natural
boundary conditions was more global. Meeting this kind of boundary condition through
mesh convergence produced accurate results throughout the duct.
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