The Numerical Simulation Of Turbulent Flow Over A Blunt Body

The bluff body is a common structure in engineering. It widely exists in aerospace, transportationand other fields. Bluff body includes cylinder, square cylinder, trapezoid, triangle and so on. In allkinds of bluff body, the research on the flow around a square cylinder has been carried out a lotbecause the square cylinder has a simple structure and is easy to control. When the fluid encountersa square cylinder, the flow state of it will change a lot. The complex turbulence phenomena willhappen, including vortex generation, development, maturity and dissipation. These phenomenainvolve the details of separation, surrounding, shearing and so on. The related research has been oneof the most complex subject in fluid mechanics. So it is veay important to study the flow around asquare cylinder. The shutter shaped blade has the advantages of simple structure and excellentperformance, so it has a wide application prospect in the refrigeration industry, aerospace and otherfields. The static mixer is an important component of the water treatment equipment. If the shuttershaped blades are used in the static mixer, the initial flocculation reaction in the pipe can be greatlyimproved.In this paper, we reviews the research progress of the flow around a bluff body. And thenumerical simulation method is used to study the flow around a square cylinder and a shutter shapedblade.Fisrt we study the effect of attact angle on the state of the fluid movement and the length of wakerecirculation region of the square cylinder. The lift coefficient and drag coefficient are simulated andanalysed. We find that the two eofficients reach the minimum value when an atact angle of12degreesis used. The motion of the fluid around the square cylinder is analysed and it is found that the flowseparation position is quite different with the attack angle.Secondly, the effect of Reynolds number on the flow field characteristics are studied. The LESmehod is used to simulate the flow field around a square cylinder under three different Reynoldsnumbers. The results show that the Reynolds number has certain influence on the length of therecirculation zone. With the change of attack angle, the change trends of the drage coefficient and thelift coefficient are the same at different Reynolds numbers. And their values increase with the increaseof Reynolds number. The frequency characteristic of flow around a square cylinder is one of the keyresearch contents. At low Reynolds numbers, the frequency value has little difference under differentattack angle. At high Reynolds numbers, the frequency value changes with the different attact angle.The Reynolds number is the main factor affecting the vortex shedding frequency. The impact of attact angle on the shedding frequency is obvious only at high Reynolds numbers.The k-ε model and LES model are used in the numerical research and the calculated results arecompared with experimental data. It is found that the accuracy of calculated results using themodel is higher than that of using k-ε model. These results include the length of recirculation region,lift coefficient, drag coefficient and so on.In addition, the characteristics of flow around the shutter shaped blade is studied at three lowReynolds numbers. The change trends of the vortex shedding frequency, the lift coefficient and thedrag coefficient in the wake region are analysed. And we have studied the relationship between thecharacteristics of flow field and attact angle at different Reynolds numbers. The variationcharacteristics of the lift coefficient and the drag coefficient are investigated.The research content in this paper is of great importance to the theoretical development andpractical application of related field. The study of flow around a square cylinder provides guidancefor the building structure design in engineering field. The research on flow around a shutter shapedblade can lay the foundation for the improvement of the static mixer.