Based on the theory of computational fluid dynamics(CFD),the bottomhole flow field of the ϕ75/ϕ49 mm diamond bits is simulated using the RNG
k-ε model.Meanwhile,the effects of bottomhole pressure,flow velocity,shear strain and the eddy of water gap on the crown surface are analyzed.The diamond arrangement is optimized in the insufficient cooling location and serious erosion area.The simulation results show that the pressure distribution gradient on the ϕ75/ϕ49 mm diamond bit's crown surface declines from the inner edge to the outside edge.Because of the eddies in the water gap,the medium flow nephogram and the shear force vector nephogram show a distorted convex form.