毕业论文移动版

摘要流动分离是导致超声速飞行器进气道性能下降或者不启动的主要原因，寻求高马赫数下高效、稳定的超声速湍流边界层的控制技术，对高超声速飞行器或者高性能火箭发动机的研制及性能优化具有深远的意义。本毕业设计利用微型涡流发生器对超声速湍流边界层的控制进行了数值研究，研究的方法是：利用ProE三维绘图软件建立微型涡流发生器的流场几何模型；运用ANSYS软件中的ICEM CFD生成计算网格；在fluent利用大涡模拟模型对工作于超声速流场中的微型涡流发生器的边界层控制进行数值计算；讨论了网格疏密度对计算结果的影响，根据计算结果选取了最优的计算网格。利用Tecplot软件对数据结果进行了分析，从流线、压力、速度和涡量四个角度对数值模拟结果进行分析讨论，研究结果表明：①发生器前后缘出现两道激波以及其间的膨胀波系，在激波及膨胀波的强压差作用下，发生器后缘上表面附近流体向发生器两侧运动，将后缘近壁面两侧流体被卷入中心上方形成流向涡对；②主逆旋流向涡对中心上升，两边下沉的运动形态使得外部高能量流体吸进并使边界层内部流体上扬，形成能量的交换，增加边界层动量，增强边界层抵抗逆压梯度的能力，可有效的抑制流动分离；③主逆旋流向涡对随着时间的发展，在向下游移动的同时逐渐升离壁面，该现象表明：完全的控制超声速湍流边界层需要在微型涡流发生器下游合适的位置再增加微型涡流发生器。④流场中绕尾涡表面存在向下游发展的K-H涡，它可有效增强外层高速流与内层低速流之间的混合，起到能量传输的作用。综上所述，微型涡流发生器可在其尾缘处形成主逆流向涡对及K-H涡，这两种涡系结构可增强外层高速流与边界层底部低速流的混合，增加边界层抵抗逆压梯度的能力，可有效的延缓边界层向湍流转捩。65225

毕业论文关键词  微型涡流发生器  湍流边界层  大涡模拟法  逆旋流向涡对   K-H涡   

毕业设计说明书（论文）外文摘要

Title        Numerical Studies for Micro-Ramp Flow  

Control of Supersonic Turbulent Boundary Layer 

Abstract

Flow separation is the main reason of performance degradation or non-operating for supersonic aircraft inlet.Seeking the control technology of efficient and stable supersonic turbulent boundary layer under high mach number which has profound significance for the development and performance optimization of hypersonic flight vehicle and high-performance rocket motor.An numerical investigation of supersonic turbulent boundary-layer flow control by using micro-ramp is presented.Research method was as follows: Three-dimensional ProE was used to establish geometric model of the micro-ramp.ICEM CFD was used to grid the model. The supersonic flow field was calculated by using the large eddy simulation method in Fluent.Discussed the influence of the mesh density on the computation,and selected the optimal computing grid.Analyzed the simulated results from streamlines, pressure,velocity and vorticity by using Tecplot.The results were as follows:①Two shock waves and expansion waves were found around the edge  of generator,and the fluid near the rear surface of the generator flew to the sides and the original on both sides got involved in center under the action of differential pressure,that was inverse spiral flow.②The counter-rotating vortex pair near the wake which hasd the motion state of center rising and sinking on both sides can make high-energy fluid in external sucked and the fluid in the boundary layer lifted up,formed the exchange of energy and then increased the momentum and ability of resisting the adverse pressure gradient of boundary layer to effectively suppress flow-separation.③With the development of time,the counter-rotating vortex pair gradually left away from the near-wall surface when flowing to the downstream.This phenomenon showed that completed control of supersonic turbulent boundary layer needed to add the micro-ramp at the appropriate position downstream of the original one.④Downstream development of the K-H vortex was found surrounding the wake, played the role of energy transfer that can effectively enhance the mixing between low speed flow at the bottom of boundary layer and the outer high-speed flow.To sum up,the micro-ramp can product counter-rotating vortex pair and K-H vortex at the trailing edge,these two kinds of vortical organization can strengthen the mixing between low speed flow at the bottom of boundary layer and the outer high-speed flow, increasing the boundary layer resistance ability of adverse pressure gradient, which can effectively delay the boundary layer transition to turbulence. (责任编辑：qin)