Aerodynamics Design And Store Separation Research Of An Aviation Bomb

The aviation bomb is flying in the high density atmosphere layer. Its fight Mach number is generally 0.9. In order to fit the transonic flight, the body is slim and the aerofoil is thin and with short wingspan. When the store is hanged on the plane, it is under the plane flow which is at different velocity and different direction at each point. The interference flow of the plane affects the store significantly. The store has initial lift force when it is at hanged status. When it is separate from the mother plane, it may crash with the plane. The main job of this paper is to develop the aerodynamic shape of an aviation bomb and study its' safe separation from the mother plane.In order to achieve the design goal, CFD simulation is done firstly in this paper, a way of wind tunnel and flight test combined together is applied. Finally, the aerodynamic assignment of this model is fulfilled very excellently. During the study of aerodynamic shape design and store separation, a new CFD solver and dynamic mesher are developed for this project and successfully applied to this model.The advantage of Euler equation solver is its calculation speed is fast, but its disadvantage is the viscosity is ignored. The flight mach number of the bomb in this project is from 0.6 to 1.2 which is subsonic/transonic/supersonic period flight, so the viscosity of the air can not be ignored. The N-S equation has to be considered for this solution. Considering the fast speed of Euler equation and its solution may close to the accurate solution, it can be used as a very good initial condition for iteration of the N-S equation solver. A good initial condition may be benefit for the convergence of the control equation and accelerate the solver. In order to achieve this goal, a high quality mixed grids of Euler equation solver based on Finite Volume Method is developed in this paper firstly. Further more, a mixed mesh N-S equation solver based on previous Euler equation by Spalart-Allmaras turbulence model is developed too. Some fast convergence methods and proper dissipation terms model are included in the solver. The 3D N-S equation solver developed in this paper is faster to convergence and more stable.The 3D N-S equation solver is applied in aerodynamic design of this aviation bomb and a successful result is achieved. Some cases accurate wind tunnel test are done to compared with the corresponding simulation solution. Then the parameters in the solver are adjusted according to the test result. When an ideal solution is got the solver begins to apply for the large amount of cases simulation. The simulation conducts the later-on wind tunnel test and the wind tunnel result verifies the simulation method and result. This combination between simulation and wind tunnel test for a real model design is successful.Based on 3D unsteady dynamic mesh conservative equations and unstructured dynamicmesh technology, the store separation problems are simulated. When the store separation, the trajectory of the store is unknown and its movement is in large scope. Considering of these features of store separation, spring-based smoothing method and local remeshing method technique are developed in this paper. Combined with 6-DOF movement trajectory equation, 2D and 3D dynamic mesh simulation for store separation problems are developed. This method is feasible and in large application for any geometry store and any movement. It can directly get the store separation unsteady effect. It occupies less memory of CPU and data structure is clear. This method is firstly applied to 2D store separation. The decomposition method is applied to make sure the accuracy of the simulation of each step. A whole store free separation procedure during transonic period is demonstrated and rich flow information is achieved including motion trajectory and loads on the body that varies with Mach number and attack angle. Based on the successful 2D solution, the solver is extended to 3D problem. A 3D dynamic mesh solver is developed. Not only the store movement velocity, trajectory and loads can be achieved, but also the whole flow character of the store and plane interference.The Captive Trajectory System (CTS) wind tunnel test is very expensive and it is not easy to get unsteady data as simulation. The wind tunnel is cancelled because of large amount of store separation simulation which shows the separation is safe. The final flight test is finished by successful store separations. The precision of the bomb is 10m to the target. The test data is compared with the CFD solution. The good consistence shows the dynamic mesh method is available for the store separation problem. It also shows the method has good prospects on prediction of store separation problem.