LCG EFFECTS ON RESISTANCE, LIFT AND TRIM CHARACTERISTICS OF R/V ATHENA HULL

摘要

The proper prediction of resistance and lift values of high-speed planning crafts is of importance in hydrodynamic design. Modelling of free water surface has also a great importance on the simulation of flow around a planing hull running at high speeds. Another issue that must be taken into account is the vertical plane motions, i.e., trim and sinkage values. Dynamic trim and hence the planing performance of the hull are directly related to LCG (Longitudinal Center of Gravity). In this study, hydrodynamic analyses (including LCG effects) of R/V Athena hull which has a round-bilge and transom stern planing craft have been performed with overset and rigid grid techniques and the numerical results have been compared with the available experimental data. It has been found that the overset grid technique is more stable than the rigid grid technique in the transition region to the planing regime in terms of dynamic trim and sinkage. The hydrodynamic computations of R/V Athena hull arc then repeated for different LCG values using only overset grid technique in a wide range of Froude numbers. For CFD (Computational Fluid Dynamics) analyses, a commercial unsteady RANS (Reynolds-averaged Navier Stokes) solver based on finite volume method (FVM) has been used. The free surface effects have been included in the computations by volume of fluid (VOF) method. The effects of LCG on resistance coefficients, dynamic trim and sinkage values, hydrodynamic lifting forces and wetted surface areas are discussed.