Author Vaz, G.
Title Modelling of Sheet Cavitation on Hydrofoils and Marine Propellers using Boundary Element Methods
Conference/Journal PhD-thesis Technical University of Lisbon -IST
Month November
Year 2005

Abstract (EN)
In this Thesis inviscid models based on the Boundary Element Method are developed for the calculation of partial and super sheet cavitation on hydrofoils and marine propellers.

The two and three-dimensional, steady and unsteady cases are considered. The theoretical formulation of the potential flow problem is presented for the general unsteady case with non-linear boundary conditions on the cavity surfaces. Different levels of approximation to the boundary conditions are introduced. The numerical solution method is based on the Boundary Element Method for the Morino integral formulation of the perturbation potential.

The two-dimensional steady and unsteady wetted flow models consider low and higher-order methods. Comparisons with analytical solutions are presented for both steady and unsteady wetted flows. The two-dimensional steady cavitating flow is tested with different cavitation models: a fully non-linear model, a partially non-linear model with re-meshing, and without re-meshing. The partially non-linear model with re-meshing is extended to the unsteady cavitating flow case. Several unsteady flows characteristic of propeller sections are tested, and the effect of the reduced frequency on the cavitation behaviour is studied. Verification techniques are applied for the numerical assessment of the two-dimensional models.

The three-dimensional wetted flow model is investigated, verified by comparison with the ellipsoid analytical solution, and validated by comparison with experimental data for rectangular and elliptical wings in steady flow, and for three different propellers, DTMB P4119, DTMB P4679 and Seiun-Maru, in steady and unsteady flow. The model is found to be fast, robust and accurate, hence suitable for the implementation of a cavitation model.

A three-dimensional cavitation model without re-meshing is implemented and extensive numerical studies are performed for hydrofoils and propellers. The numerical results for cavitating flow show good agreement with the experimental data for the MARIN S-Propeller and the INSEAN E779A propeller.

The three-dimensional computer code resuting from this Thesis forms the basis of the code "PROCAL" currently used at MARIN for the analysis of flow on ship-propellers.

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