The 12th International Conference on Hydrodynamics
18 – 23 september 2016, Egmond aan Zee, The Netherlands
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Session: Linear and non-linear waves II
Room: Room 2
Session start: 16:00 Tue 20 Sep 2016

G.D. Xu
Affifliation: Harbin Engineering University

Q. Meng
Affifliation: University College London

Topics: - Linear and non-linear waves and current


When a hydrofoil craft cruises in shallow water, such as a river or marginal sea, the hydrodynamic performance of the hydrofoil travelling at super-critical and hyper-critical speed should be considered. The nonlinear free surface effects of shallow water would become important, especially when the submergence h is small with respect to the chord length of the foil . It has been observed that a rigid body or pressure distribution moving in finite water zone may cause upstream solitary waves when the advancing velocity Fh= U/sqrt(gH) is around ([1][2][3][4]), where U is the speed of the body or pressure distribution, g is the gravitational acceleration and H is the depth of undisturbed water. In present study the nonlinear hydrodynamics and the wave patterns caused by a 2D foil advancing in water zone of finite depth are concerned with. It has been found that there would be a strong circulation when there is an attack angle. The cross effects of circulation, bottom and free surface, and the resulting resistance, lifting force and the moment at various speeds will be investigated. A NACA0012 foil moving at constant speed U in quiescent shallow water will be simulated using Boundary Element Method (BEM) through time stepping scheme. The nonlinear free surface boundary conditions and the unsteady Kutta condition[5] are imposed. Numerical simulations have been carried out to study the wave patterns caused by the hydrofoil in shallow water. When the supercritical speed is concerned, the upstream wave is above the initial calm surface and run forward; the trailing wavetrain propagates aftward and a depressed region behind the hydrofoil forms. When ‘hyper-critical’ speed is considered, a single soliton forms above the foil as the trailing waves propagate aftward. The effects of the speed, submergence and angle of attack on the hyper-critical soliton will be further investigated.