Analysis Of Propeller-induced Pressure Fluctuation On Ship Surface

People never stop their studies on pressure fluctuation of propeller since it was foundin1952. Accompanied by the rapid development of large-scale and high-speed ships inrecently years, the thrust and power of the host increase and these make the pressurepropeller-induced fluctuation more and more serious. Use traditional theory to calculatepressure fluctuation is very cumbersome; the limitations of the empirical formula are toomuch; and the cost of model experiments is too high. However, the maturing ofcomputational Fluid Dynamics cause people’s attention, it’s now widely used on the studyof hydrodynamic performance, thus, this paper hopes to solve the problem ofpropeller-induced pressure fluctuation with CFD, the major work are as follows:Firstly, ignore the influence of the free surface, make the feasibility of calculatinghydrodynamic performance of the ship with CFD be verified. Take a certain container shipand KCS container ships as examples, establish their3D models and make them to becalculated and analyzed with ANSYS. After the calculation, do post-processing to theresults, compare axial-velocity distribution and velocity vector at propeller disk of thecertain container ship and the resistance of KCS to experimental values. Furthermore, inorder to improve the accuracy of the flow fields of the ship, this paper also do some studieson compensation duct and flow deflector to observe the different flows of KCS.Secondly, ignore the influences of the free surface, make KCS sails at several specificspeeds and rotation speeds in the water and do unsteady simulation. While the calculationfinishes, we would get the fluctuation curves of the pressure to the five monitoring points inthe plane above the propeller. From these five curves, we can found the influences ofpropeller to the distribution of pressure at stern surface. Then, do FFT to the data to get theamplitude of pressure fluctuation at each order blade frequency.Lastly, choosing VOF model to do simulation and analysis to the ship KCS whileconsidering the influence of free surface, get different results at different speeds with onerotation speed and different rotation speeds with one speed. Comparing the results toexperimental values and the results while ignoring the free surface, and also doing FFT tothe getting cures of pressures of the five monitoring points. Studying on the amplitude of pressure fluctuation at first order blade frequency and analyzing the causing reasons of thedifferences.