【作者】 黄勇；

【导师】 周新平；

【作者基本信息】 华中科技大学 ， 流体力学， 2017， 硕士

【摘要】 扑翼昆虫飞行的空气动力学机理复杂而有趣,一直是研究中的热点。通过研究昆虫飞行的非定常气动特性可有力促进微型飞行器(MAV)的发展,具有重大的科研和民用前景。昆虫飞行时通过翅膀上下拍动,形成强烈的前缘涡(LEV),能够有效提升升力,其升力数值比定常情况下大很多,足以平衡昆虫的重量。本文意在探究低雷诺数昆虫扑翼飞行中,运动参数的变化对漩涡分布以及升阻力系数的影响,在此基础上,进一步研究地面效应,墙壁效应以及地面开孔情况下对漩涡分布等气动特性的影响。本文中针对雷诺数为100,运动模式为normal-flapping model的二维扑翼模型,参数无量纲化,通过Fluent商业软件求解不可压Navier-Stokes方程,分别数值模拟不同相位差,拍动幅度和旋转中心条件下漩涡分布情况以及升阻力系数变化趋势。后续选取不同的离地间隙,墙壁间隙和孔径间隙来对比分析地面效应,墙壁效应和孔径大小对气动特性的影响。研究发现翅膀的运动参数会明显影响漩涡分布情况,前缘涡则会明显影响升阻力系数。当地面间隙小于2个弦长时,地面效应会明显影响尾缘涡的分布情况,增大升阻力系数,在2~3个弦长时会降低升阻力系数,大于3个弦长是地面效应逐渐消失。墙壁效应则对漩涡分布和气动参数影响不大。孔径的存在会明显影响尾缘涡的分布情况,随着孔径的增大,升阻力系数均明显降低,逐渐趋近于标准值。更多还原

【Abstract】 Insect aerodynamics is always a hot issue in the research,which is also interesting and complex.a better understanding of insect aerodynamics is necessary to improve the design of Micro Air Vehicles(MAVS)which has significant prospects in both scientific research and civil aspects.During insect flight,the wing flapping in the upstroke and downstroke,causing a leading edge vortex(LEV)which increases lift strongly.The lift is much bigger than the quasi-steady one and can hold the weight of insect.The main objective was to investigate the influence of wing kinematics on vortex dynamics and force coefficients concerning the flight of a hovering insect at Re=100.performance of normal-flapping model,and based on that ground effects,wall effects and holes effects.Concerning the flight of a hovering insect at Re=100 in the 2D normal-flapping model,a numerical simulation is developed within the CFD solver Fluent.this simulation model is used to investigate the influence of arbitrary wing kinematics such as phase difference,amplitude,rotation center on vortex dynamics and force coefficients.Also different ground clearance,wall clearance and aperture are used too investigate on vortex dynamics and force coefficients.The results shows the wing kinematics have strong influence on vortex dynamics,and the force coefficients depend strongly on the strength of LEVs.When the ground clearance is smaller than two chords,the ground effects can strongly influence the vortex dynamics,and enhance the force coefficients.When the ground clearance is between two chords and three chords,it will decrease the force coefficients and when ground clearance increase bigger than 3 chords,the ground effects will disappear gradually.The wall clearance has litter influence on the vortex dynamics and force coefficients.The existence of aperture will strongly influence the trailing edge vortex dynamics,and with the increase of aperture distance,force coefficients move to normal values in no-aperture gradually.更多还原