Research On The Applicability Of CFD Based On FLUENT In The Projects Of Ships And Ocean Structures

Research on the numerical calculation in the field of ships and ocean structures about resistance and the fluid field becomes more and more mature. As one method of numerical methods, its computational accuracy is becoming higher and higher following the development of computer technique and the theory of numerical method. At present researchers mainly use commercial codes to realize the numerical calculation and analysis. Researchers in the field of ships and ocean structures focus on the prediction of ship resistance and the vortex-induced vibration of ocean structures, and the most popular CFD code is FLUENT.This paper is mainly on the engineering applicability of CFD especially on the analysis of the load of ships and ocean pipeline based on FLUENT. There are a lot of research about the pipeline, but most of them are focused on the stand pipe. The model calculated in this paper is an oil pipeline on the horizontal direction. The accuracy of numerical calculating the resistance of ships is proved by many papers, but most of them do not take the real project as conferences. There is only comparison of the results of numerical calculation and the experience formula or no more than five velocities have they chosen to calculate, which declines the persuasion of numerical calculation. Two engineering models are chosen:a mono-hull ship and a trimaran. More than ten velocities are calculated in numerical calculation. The results of numerical calculation are compared with the results of the experiment.The realization of the numerical calculation is based on the Finite Volume Method (FVM). There are three points in meshing the grid:using the technology of SIZE FUNCTION in Gambit as the pre-process code, hybrid grid in the calculation region of mono-hull using ICEM as the CFD pre-process code of ANSYS and all structural grid around the trimaran body. The analysis of the oil pipeline under water is simulation of single phase flow and the others are simulations of multiphase flow. Wall function method, RNG k-e turbulent model are adopted for the calculating. SIMPLE algorithm is adopted in the single phase flow. In multiphase flow, the free surface is captured by VOF method and PISO algorithm is chosen instead of SIMPLE algorithm in order to have a faster convergence of continuous.This article studies the application of CFD in designing new ships and optimizing the ship shape and compares the results of numerical calculation and physical test. In these conditions bellow the numerical method used in this article can be used to analyze the load of ships and ocean structures:The oil pipeline is under water:when0.03<Fr<1.2, the relative error is smaller than7%. The oil pipeline is in water and air:when0.2<Fr<0.85, the relative error is smaller than5%. In these conditions, it is reasonable to use CFD method for the force analysis of pipeline.The mono-hull ship moves in water and air:when0.4<Fr<0.8, the relative error is smaller than7%. And the result has a higher precision when the high speed ship has a trim by the stern.The trimaran moves in water and air:when0.3<Fr<1.1, the relative error is smaller than6.1%, which certificates that CFD method is of engineering applicability.