Preliminary Research On Flow Characteristic Of Transonic Wind Tunnel Slotted Test Section

Most of aeronautic and astronautic aerodynamic models want to be experimentized on transonic wind tunnels. There are four major problems for transonic wind tunnels to generate transonic airflow: Solving the air-logged condition; Generating the equably low supersonic airflow; Reducing or eliminating the wall interference of subsonic airflow; Reducing or eliminating the influence of the shock waves'reflection. How to solve the four major problems is the key technology to get high flow quality. Recently, the domestic operative transonic wind tunnels use the orifice plate as the wall of the test section on the whole. However, representation by Langley 8 Foot wind tunnel and European transonic wind tunnel, most euramerican transonic wind tunnels use the slotted plate as the wall of test section, whose flow stability, flow uniformity, flow angularity, Reynolds numbers and noise level are the best of the world. Since the 11th five-year plan is carried out, the heavy aircraft project, the advanced battle-plane project and the new astronautic transport system project have been developed, which demand more stringent target, whereas the test ability of domestic transonic wind tunnels is not satisfied with the demands of our advanced aircraft's research. So, it's very necessary to do research on the slotted test section as the technical prepare for the next generation of transonic wind tunnel.The development of the CFD makes the numerical simulation to be one of effectual ways to study multi-style flows. To accurately describe the characteristic of flow, the problems of the method of numerical simulation need to be resolved, including the number of computing mesh, the turbulence model, the computing precision and the method of compute. All of these need to be compared with the theoretic research or the testing result aforehand to minimize the disparity between simulation result and the matter of fact.In the preface of the thesis, we introduce the concerning research background of the transonic wind tunnel slotted test section. Most words expatiate on the domestic and overseas actuality research on the flow near the slotted test section. A brief discussion of the method of research is made also. Then, a description was given about the work in the thesis.In the second chapter, we give a review about three primary discrete format of the computational fluid dynamics. Discussion among these on each characteristic and comparison is given. Then, the discrete format used in this thesis is illuminated also. The reader will know the computational instrument by the introduction of Fluent. At the same time, the control equations of the flow are given, which are the theoretic analysis base of flow mechanism. The numerical simulation of turbulence is introduced afterwards, which shows that the selection of turbulence model is very important influence for the result of simulation. The selection of the solver of Fluent is explained at the end.In the third chapter, we establish the three dimension geometry of the research object by the Autocad and SolidWorks tool software. Two different geometries of slot are illuminated detailed by chart. Then, we carry out the mesh work on the three dimension geometry by Gridgen. The initial conditions and the boundary conditions of the simulation are explained at the end.In the fourth chapter, we put our attention to the number of grid and the selection of the turbulence model. Comparison among the number of calculation grid as 670,000 and 1,070,000 and 1,600,000 is given, which on the flow uniformity and flow angularity. Then we get the result that 1,070,000 is the suitable number of calculation grid for the research object. Study on the selection of turbulence model is carried out by comparison of four different models: skw, sstkw, sa, ske, all of whose simulation result are contrast to the result of reference literature. The skw turbulence model is confirmed as the suitable model for this research.In the fifth chapter, we do some research on the influence of different slotted planes in the test section. First, the ETW and Langley 8 Foot, two kinds of slot model are compared when the Mach number on the test section is 0.9 and 1.1. And we find out that the model of ETW slot is more suitable for this thesis. Then, we carry out the research on different slots, different open area ratios, different angles of the slot plate, and different masses of the air pump flow. Analysis on the influence of each parameter is done. The influence of step in the test section when the Mach number is 1.6 is discussed also.At the last chapter, a review about the work in the thesis is made, the shortage of the work and the direction about the future research are presented.