Numerical Simulation And Research Of Current Load On Dynamic Position Supply Ship

This paper calculates the current load coefficients under different Reynoldsnumber, using computational fluid dynamics software Fluent, when dynamic positionsupply ship confronts with current. And ship type parameters, deadwood andReynolds number are studied the influence law of current load coefficients throughthe transformation of bare ship type and geometric parameters of deadwood. Theregression of coefficient calculation formula is obtained.Before calculating the dynamic positioning ship, a tanker ship with experimentaldata is studied the flow field within0~180°to validate the numerical calculationmethod. And through the analysis of hull surface stress and shear stress, the viscouspressure resistance coefficient and friction coefficient are studied with the flowdirection angle. And then based on a dynamic positioning ship as the parent ship, thebare ship hull form is transformed by controlling the displacement and the captainchangeless. The transformed bare ships are calculated the load coefficient underdifferent Reynolds number. In the tail of the mother ship, by changing the deadwoodof area and centroid position, the parent ship with different deadwood parameters iscalculated the flow coefficient of current load. Finally, considering the deadwoodparameters and the influence of Reynolds number, by adopting the partialleast-squares regression, the calculation formulas of current load coefficients areobtained. In this paper, calculation of numerical methods and the results aresummarized as follows:(1) The numerical methods: The calculation domain choices the domain ofcylindrical inside and square outland. When calculating the current flow load underdifferent flow angle, just turn the cylindrical domain in the grid. The meshing methodis different from direct route: slightly reducing the area of the grid density of adjacentto the hull surface; reducing the grid spacing of parallel middle body place andincreasing of the outer hull grid density. SST turbulence model is suitable for low andhigh Reynolds number;(2) Longitudinal current load coefficient: When the current angle is small,friction coefficient is main ingredient. But when the angle is40°~130°, viscous pressure drag coefficient increases, and is the main ingredient. Viscous pressureresistance coefficient is related with pressure of the fore and aft ship on the horizontalprojection;(3) Lateral current load coefficient: When the current angle is60°, the lateralcurrent load coefficient is the peak value. The friction coefficient is very small andcan be negligible. Viscous pressure resistance coefficient is related with pressure ofthe fore and aft ship on the vertical projection;(4)The added deadwood increases the tail vortex resistance and leads to thecurrent load coefficients increasing. The formula of impact factor is obtained byregression and the formulas are verified;(5)Reynolds number mainly influences coefficient of frictional resistance. Andthe coefficient of frictional resistance increases when Reynolds number decreases;(6)The major ship form parameters that affect the coefficient of current load arethe block coefficient Cband the captain of the ship width ratio L/B. And through themethod of least squares regression, the current load coefficient of each angle isobtained. Eventually current flow under arbitrary angle can be obtained by linearinterpolation coefficient of load.