A NONLINEAR BOUNDARY ELEMENT METHOD FOR THE ANALYSIS OF UNSTEADY PROPELLER SHEET CAVITATION

The unsteady flow around a cavitating marine propeller is treated in nonlinear theory by employing a low-order potential-based boundary element method and a time-marching scheme. The kinematic and dynamic boundary conditions, which are fully three- dimensional and time-dependent, are satisfied on the propeller surface beneath the cavity and on the portion of the blade wake surface which is overlapped by the cavity. The formulation and algorithm are developed to treat arbitrary cavity planforms in an efficient and robust manner. The results from the numerical method are shown to converge quickly with number of panels and number of time steps per propeller revolution. The produced cavity shapes are validated and shown to satisfy the imposed dynamic boundary condition within acceptable accuracy. Computed cavity planforms are compared to those from linear theory and linear theory with leading edge corrections.