Hydrodynamic Optimization of a Containership

Using open-source software Dakota, this paper describes the process of generating an optimal parametric hull shape for a generic containership. Selected design variables defined the ship’s hull, and the influence of these variables on calm water resistance was analyzed. Computations of the flow around the hull were obtained from a validated nonlinear potential flow boundary element method. Using the multi-objective optimization algorithm Surrogate Based Global Optimization (SBGO) reduced the computational effort. The hydrodynamic calm water ship resistance defined the objective function. Compared with the original hull, wave resistance of the optimal hull was significantly reduced for the ship at Froude numbers corresponding to its design speeds.

Research on Groove Method to Suppress Stall in Pump Turbine

The pump turbine is prone to stall when running at part-load operation. Stalls would cause a hump-like head characteristic curve, low-frequency high-amplitude pressure pulsation, and surge or resonance in the system. There is a lack of efficient methods for pump turbine stall suppression. The traditional blade hydrodynamic optimization method has limited effect and would influence the other characteristics. As the essence of stall is flow separation, forming a severe backflow vortex, a “Groove Method” is put forward and employed to suppress stall in a pump turbine with the full consideration of the mechanical structure, flow field, and pressure field. Both experiments and calculations are carried out to test the effectiveness of this new method. Furthermore, its deep mechanisms are revealed. This method can weaken the head hump to a certain extent and reduce the pressure pulse amplitude induced by stall. Meanwhile, the performance at the design operating point is not disturbed much.