Advances in complex low speed flow around a prolate spheroid

Abstract

Understanding and predicting the flow around the prolate spheroid is of great engineering significance to guide the design of vehicles such as aircraft and submarines. In recent years, a lot of experimental and numerical studies have been carried out on the flow around the prolate spheroid. The qualitative description and quantitative research of flow separation around prolate spheroid at attack angle are presented, promoting the identification and topology research of three-dimensional separation. The experimental results of oil flow, smoke, dye, hydrogen bubble, and LDV are given. The flow field characteristics are analyzed, and the existing problems are pointed out. Based on the introduction of the above phenomena, the effects of separation on aerodynamic force, noise, and wake are introduced. The effects of test conditions such as transition zone, protrusion, depression, and tail support on flow are also discussed. There are obvious differences between the above steady flow and the unsteady maneuvering process. The unsteady maneuvering process can not be treated as a steady or quasi-steady problem. During the maneuvering process, the separation will be delayed obviously, and the aerodynamic force will also change obviously. The greater the angle of attack, the higher the maneuvering rate, the more noticeable this effect will be. At present, RANS turbulence model is still the primary engineering method to solve the large-scale separated flow around the prolate spheroid. However, LES, DES, and other methods have gradually been widely used. Due to the limitation of computer capability, DNS can only be used in the case of lower Reynolds number but not in high Reynolds number flow. The difference between the numerical simulation and the unsteady simulation is more significant. Finally, the research progress of prolate spheroid transition is introduced. The mechanism and identification of TS transition and cross-flow transition are more accurate. The numerical simulation results are basically consistent with the experimental results, but the understanding of reattachment transition is not clear enough, especially on the windward side. Therefore, the research of prolate spheroid transition still needs to rely on experiments.