Comparative Study on Hydrodynamic Performance of Planing Hull based on Empirical and Numerical Methods

Abstract

Predicting the resistance of a planing hull is a challenging task due to its complex hydrodynamic behavior. The present study evaluates the hydrodynamic performance of a high speed patrol boat using Savitsky’s empirical method and an open-source RANS-based CFD (Computational Fluid Dynamics) solver, OpenFOAM 11. The key performance parameters include resistance, trim, and sinkage. The study begins with the validation of results obtained from CFD and empirical method against the experimental result of a deep V-type planing hull, known as the GPPH (Generic Prismatic Planing Hull), towed in calm water. The numerical results are also compared with the well-known Savitsky's 1964 method. The validation reveals that the CFD model, with an error of 0.95%, is more reliable than the empirical method, which has an error of 2.79%, as the CFD approach captures the dynamic behavior of the planing hull more effectively. A systematic verification study is performed to assess the numerical uncertainty based on grid size. Following the validation study, the same CFD model and empirical method were applied to a similar deep V-type patrol boat sailing in the waterways of Bangladesh. At higher speeds, a lower deviation between the empirical and numerical methods is observed. The dynamic pressure distribution on the hull and wave pattern were less affected due to a reduction in wave making resistance at a higher Froude number. Finally, the study extrapolates the resistance to the full scale, and the power requirements at five different speeds are obtained using both empirical and numerical methods. Savitsky's method and CFD method provide reliable resistance and power prediction for planing hull, with a deviation of 5% at higher Froude numbers.