Modification Method Of Testing And Computation Still Water Speed In Dynamic Waters

In speed and powering of ship, the still water speed is an important index. Got the speed accurately is significant for ship designing and regulating navigaton channels, especially the rapids shoal. At the present time, full scale tests and model ship experiments are the mian research methods, and the prototype testing usually was carried out in calm waters. But in some rivers, the absolutely suitable calm waters is difficult to be found, so sometimes the prototype testing has no choice to be done in relatively suitable dynamic waters.With the fast development of computer tecnology and ship's computational fluid dynamics, the function of CFD is more and more powerful, an increasing number of researchers begin to adopt numerical simulation technique to investigate the viscous flow around ship hull. Based on results of experiment, the test and compute still water speed method was investigated with prototype testing, numerical simulation and theoretical analysis. Works and products as follow:①By the results of"Hua Ping"ship's calm water trail in LanCang river dynamic waters, the initial still water speeds were compared, which were got by speed through the water method and average of up and down stream navigation method respectively. The speed through the water method is better than the second method to compute initial still water speed. Because the influence of slope drag was neglected in the initial still water speed, so drag balance method and resistance compared method were come up. The actual still water speed can be obtained by using these two methods to compute.②The"Hua Ping ship was simulated by software FLUENT, and various working conditions's flow resistance were obtained. The numerical calculation results indicated that Fluent can exactly predict the friction resistance of a ship hull; but the total drag must be need use more precise model and control parameters to get a good result.③Based on numerical simulation results, the full scale ship's flow resistance computed formula was established by making thrust equal resistance. The initial still water speed was corrected with resistance balance method. The computation results shows that the difference between revisal still water speed and through water speed was increasing linearly, along with slope drag proportion's growth in total resistance. Compared the two correction methods, the resistance compared method can keep a good precision at laking detailed ship parameters.④The propulsive force and total resistance of ship was discussed, there have many difference between downstream navigation and counter flow sailing effective propulsive force. Then some hypothesis has been done about the gravity slope componet, which could provide certain reference for the future research work.