Mortar Shells Numerical Simulation Of Drag Reduction By Golf

It's important to research varies of blunt body which include the sphere flow around for the industry and theory. One of the aim for people to study it is to know the way that can reduce the drag and save the source of the energy. The flow Past the golf and the mortar bomb with pits are simulated according to the boundary layer theory. The results show that the Past flow drag is diminished effect when the pits are on their surface. The Paper is divided into three Parts:Firstly simulating for uniform Past sphere and the sphere with pits using DES method that is based on the k-ωSST equations and LES method that is based on the Smagorinsky-Lily subgrid model have been researched. The simulations are used on Re=500,1000,2000 and 5000.The calculations of drag coefficients and velocity contours and comPared with the results of experiments show that there is little difference on the two methods'results for the sphere when the Re number is low. The both two methods are could be used for the simulation on the smooth sphere at this time. The features of results are general agreement though, and the differences have been greater in details on the sphere whether with or without pits followed the Re increasing and the results using the LES are better than the DES'.Using Numerical simulation of uniform flow Past a golf that the diameter is 42.6mm, with well-distributed pits using LES method which is based on the Smagorinsky—Lilly subgrid scale model in the next. The results confirm that the detached point of golf's wake is farther than the smooth sphere's and the drag on the golf is smaller than the smooth one's. Considering the uniform flow Past a golf with the effect of clockwise and anticlockwise revolve that the speed is 80rad/s,100rad/s, 200rad/s,2000rad/s. The drag coefficients reach the minim when the revolve speeds are positive or negative 100rad/s The results show that the wake structure is more uneven and come into being the pressure perpendicular to the uniform. The amount of pressure has nothing to do with the direction of the rotation and the drag coefficient is larger than the non-rotation golf.Revolve has important influence on the pressure. The theory, method and results are used to research the mortar bomb which flies with supersonic speed in the final chapter. The results state the pressure drop of mortar bomb with pits reduced obviously comPared with the smooth one so that the range of the mortar bombs is improved. The drag of mortar bombs is related with the angle of attack under the same Reynolds number.