Simulation Research For Branching-pipe Structure And Turbulent Field Laws

Pipeline systems is an important part of the ship, including many main and branch pipes, etc; which is an important bridge connecting the relative systems. The actual measured noise caused by piping is an important contribution to the noise source radiation of the whole ship. Thus, lowering the noise of the ship effectively has an important significance on structure system optimization.This paper relies on large eddy simulation technology with FLUENT software. Straight-pipe field with the origins existed, two-branch pipe field without origins, and three-branch pipe field without origins will be calculated and analyzed. And also, the establishment of mathematical model for the vortex pair phenomena which appears in a turbulent flow field will be completed.The above calculation cases will be finished respectively in FLUENT platform. When there are origins in the straight pipe, its flow flied will generate eddy current. RSM and k-ε two models were used to validate the value of steady-state calculations; Two-branch pipe is from30°to90°, as a numerical case at intervals of5°; Three-branch pipe including the ipsilateral and the opposite side, spacing between the two branches of tube is from1d to8d, as a numerical case at intervals of Id. Respectively, analysis and comparing the numerical case will be accomplished from the velocity field, vorticity field and sound pressure level.As results claim, when the two-branch branch angle is between50°and70°, its basic physical parameters of flow field are the most ideal, then the configuration of the ship structure is a top priority; with regard to the three-branch pipe,when the two tube spacing of the opposite side is2d, its physical parameters of the flow field is optimal, so2d spacing three-branch pipe is a top priority; two ipsilateral tubes of three-branch have a zoom effect on the disturbance source in the piping flow field.In the calculation, the coherent sequence and the vortex pair appears; as there is the large vortices gradient between the coherent vortices and the non-turbulent region, where the strong eddy diffusion can occur, so that the non-turbulent fluid turbulence quickly integrated into the large-eddy of turbulence and participate in the following development process.