Numerical Study On The Flow Characteristics Of Multi- Combined Hemisphere Based On CFD

Ships on the voyage will not only be decided by the action of wave force, but also be decided by the effect of wind load, although the interaction on the wind load effects among MOSS LNG carrier superstructures cannot be ignored, superstructures are relatively independent, has the obvious characteristics of flow around, and are similar to flow around multi-combined hemispheres. By the numerical study of flow around multi-combined hemispheres, a solid foundation will be laid for LNG carrier wind load numerical method and grid division method. And it can improve the accuracy of numerical prediction of LNG carrier wind load, and it has important effects on improving and enhancing the maneuverability and has an important role to ensure safety of navigation safety of LNG. Based on the viscous flow theory, the numerical simulation of the flow around multi-combined hemispheres is carried out by using the Fluent computing platform.The combined hemisphere were 3D modeled and computational domain set, in order to verify the selected grid division method and numerical method of reliability and stability, the numerical simulation of flow around hemisphere at Reynolds number Re=2×106was carried out, and numerical simulation results were compared with wind tunnel test results. grid partition method and realizable turbulence model for the numerical simulation were identified. Then the atmospheric boundary layer exponential law simulate the real wind field. Numerical study of flow around single combined hemisphere, double tandem combined hemispheres, three tandem combined hemispheres and four tandem combined hemispheres were carried out at Reynolds number Re=8×106, Re=4×107 and Re=7.2×107. The results show that when flow around single combined hemisphere, flow field characteristics are similar, The change of Reynolds number is less affected on width of recirculation zone and the boundary layer separation point location, the resistance coefficient increases along with increasing Reynolds number; when flow around multiple combined hemisphere tandem, streamline began to flow through the gap between the two combined hemispheres, and flow to the downstream from the other side of the downstream combined hemisphere, large scale eddies are still formed in the latter part of the hemisphere combination on both sides and back. Increasing the Reynolds number and the number of combined hemispheres, the number of large scale eddies do not change. Based on the numerical simulation method in this paper, more flow details of wind field and transient effects can be captured, the accuracy of numerical simulation can be improved. The LNG carrier longitudinal resistance coefficient is more close to the result of wind tunnel test, the error is within 20%.