FINITE ELEMENT SIMULATION OF SIMPLE THREE DIMENSIONAL FULLY CAVITATING FLOWS
Based on potential flow theory, a formulation is given for three-dimensional fully cavitating flow with a Riabouchinsky model. The model is nonlinear and the location of the free surface of the cavity is not known priori. Therefore, an iterative procedure is used to locate the free surface boundary. The employment of a trial-free-boundary approach effectively reduces the fully nonlinear model to a linear one, and the solution at each iteration is obtained by means of the finite element method (FEM). Examples studied were fully cavitating flow past flat plates in a water tunnel. Results are given for pure drag flows past circular and elliptic plates and a lifting flow past a circular plate. Because of the change in flow boundary conditions at the separation edge and the failure of the FEM to resolve these conditions accurately, the ability of the numerical solution to maintain a constant pressure over the entire cavity decreases as the three dimensionality of the free surface increases. However, the present procedure produces absolutely stable iterations and shows no sign of drifting of the free surface. It is found that satisfaction of a tangent separation condition of the free surface from the flat plate body is crucial for the stability of the iterative procedure. Grid refinement in both the streamwise and transverse directions reduces the computational error. While free surface movement between iterations is a useful convergence criterion, a flow-rate balance between upstream and downstream cross-sections appears not to be a good criterion.
Stanford UniversityDepartment of Civil Engineering
Stanford, CA United States 94305
- Ko, P Y
- Street, R L
- Publication Date: 1979-11
- Pagination: 126 p.
- TRT Terms: Boundary layer flow; Boundary layer separation; Cavitation (Mechanics); Finite element method; Free surface; Potential flow; Three dimensional flow
- Old TRIS Terms: Cavity dynamics; Free surface effects
- Subject Areas: Design; Marine Transportation;
- Accession Number: 00317461
- Record Type: Publication
- Source Agency: National Technical Information Service
- Report/Paper Numbers: TR-241 Final Rpt.
- Contract Numbers: N00014-75-C-0277
- Files: TRIS
- Created Date: Sep 16 1980 12:00AM