Numerical And Experimental Study A Body Moving Near Free Surface

The problem of the free-surface flows is being one of focus and difficulty in hydrodynamics. The key to discover the character of the free-surface flows depends on developing and perfecting methods and instruments. This paper introduced the author抯 investigation on the flow field around a moving body near free surface, especially the author抯 development in both numerical simulation and experimental measurement. In the paper, Kinds of methods to solve problem of the free- surface flows were reviewed firstly, their advantage and also the disadvantage were analyzed respectively, and then the VOF method is introduced in detail. In order to track the free surface more precisely and simulate the deformation of complex free surface, the VOF method was improved. The author developed a free surface reconstruction 0 method, the logic of this method was simple, the algorithm with the second order accuracy on space was proved to be fine. A new iteration factor of the pressure interpolation cell was given out at the same time, it was able to improve the convergence of iteration, and enhanced the ability to deal with complex free surface flows. Another a hybrid means of combined suitably Nirth- Nichols抯 donor-acceptor method and Lagrange line segment method was used to update the faction F, it was able embody their virtue and overcame their shortcoming, thereby it could track the free surface more accurately. The PIV is a technique for measurement of whole, instantaneous fields of velocity, but it contains experimental errors inevitably and maybe some data is false. To ease up these, two post- processing methods of PLV were developed in this paper. One is a method of combining Ply and BEM, it combine CFD and PIV through the boundary cell method, could be used to correct the PIV data, reduce measurement errors, and estimate velocity at invalid measurement points. A good result was obtained when it was applied to process the data in flow field measurement of water entry of wedge-body. The other is a post-processing means based on continuity equation of fluid. It could settle the directional ambiguity in film PIV, and could correct the measurement data to be more close to continuity restriction. This software-based method to solve the directional ambiguity problem could reduce the spending on finance and labor. The 2D and 3D flow fields around square column moving near free surface were simulated by the improved VOF method. The calculated results were analyzed in detailed. In order to understand further the flow fields and evaluate simulated result, the flow fields around square column move near free surface were measured by PIV. The results of calculation and experiment indicated that the improvement for VOF method and the means for post-processing of PIV in this paper were effective.