Rankine涡作用下激波变形和分叉的数值研究

数值模拟了激波和Rankine涡相互作用，重点研究了波涡相互作用引起的激波结构的变化过程。应用非结构化适应网格下的二阶精度Godunov型的PLM格式来求解Elder方程，对一平面激波与不同涡强Rankine涡相互作用下瞬态激波的运动、发展进行了研究。漩涡与激波间相对强度的大小对激波结构的影响明显，弱相互作用诱导激波变形，强相互作用诱导激波变形并产生分叉。计算结果表明，应用非结构化适应网格的PLM格式所得到的数值解较好地反映了瞬态激波结构的有关特征和信息。     

漩涡发生器对燃油喷嘴的雾化性能影响的数值研究

为了探讨漩涡发生器(简称V.G)对燃油喷嘴雾化性能的影响,利用Gambit分别建立了原型喷嘴、加装2个漩涡发生器和加装4个漩涡发生器喷嘴的模型,并利用FLUENT软件进行了数值模拟,得到了三种模型的出口流场分布图。计算结果表明:在相同燃油压力下,加装漩涡发生器可以加快射流的混合速度,其中加装4个漩涡发生器的喷嘴的加速掺混能力最高,加装2个的其次,但仍比"原型"的情况有明显的改善;当燃油压力改变时,掺混能力会随着燃油压力的提高而提高。     

空中受油管的绕流特性研究

空中加油是提高飞机航程、活动半径的重要方法。通过对四种固定受油管的数值模拟,从流动特性的改进方面说明了合适的截面及倾角会降低受油管绕流的压力脉动,进而使噪声降低。     

基于自适应网格的超声速液体射流破碎过程研究

为研究超声速气流中液体横向射流的破碎过程,采用脉冲背景光方法和VOF方法开展了实验和数值研究。为提高液体横向射流中气液界面和气流场特征捕捉的精确性,采用自适应网格技术对于气液界面、激波出现位置进行网格细化,计算得到了较为精细的气液界面、激波特征及涡系结构。研究结果表明:在低成本仿真模拟条件下,利用自适应网格计算得到的射流轨迹和轮廓与实验吻合较好,射流轨迹的最大误差为10%;射流初始段在超声速气流条件下,仍然存在一段高度约为1.9倍喷孔直径且圆柱形态保持较好的连续光滑液柱。随着喷注压降的升高,液柱的长度逐渐增大;主流气体流经液柱发生三维绕流,在射流附近和近壁面区域形成不断演化的反转涡对,反转涡对的形成加速了液体射流一次破碎过程。     

Generalized Kutta–Joukowski theorem for multi-vortex and multi-airfoil flow(a lumped vortex model)

For purpose of easy identification of the role of free vortices on the lift and drag and for purpose of fast or engineering evaluation of forces for each individual body,we will extend in this paper the Kutta–Joukowski(KJ) theorem to the case of inviscid flow with multiple free vortices and multiple airfoils. The major simplification used in this paper is that each airfoil is represented by a lumped vortex,which may hold true when the distances between vortices and bodies are large enough. It is found that the Kutta–Joukowski theorem still holds provided that the local freestream velocity and the circulation of the bound vortex are modified by the induced velocity due to the outside vortices and airfoils. We will demonstrate how to use the present result to identify the role of vortices on the forces according to their position,strength and rotation direction. Moreover,we will apply the present results to a two-cylinder example of Crowdy and the Wagner example to demonstrate how to perform fast force approximation for multi-body and multi-vortex problems. The lumped vortex assumption has the advantage of giving such kinds of approximate results which are very easy to use. The lack of accuracy for such a fast evaluation will be compensated by a rigorous extension,with the lumped vortex assumption removed and with vortex production included,in a forthcoming paper.     

高超声速楔形模型飞行流场数值模拟

针对典型的高超声速飞行器结构模型,利用COMSOL Multiphysics多物理场耦合软件对其流场进行建模仿真.研究了楔形头部对高超声速气流的影响,分析了气流流过楔形模型时的流线、压力、温度分布.对不同楔角的模型进行了模拟,观察其对气流速度分布的影响.依据数值模拟的结果对高超声速气流流场的流动特性进行了细节分析.     

翼型失速的非线性动力学特性及其控制

以NACA0012翼型为研究对象,应用CBS( Characteristic-Based Split)有限元方法对翼型绕流流场进行数值模拟,着重对翼型失速现象的动力学机理和特征进行研究.首先给出了静止翼型在不同迎角下流场的瞬时流线图以及静态翼型的迎角-升力系数关系曲线,并且分析出此曲线具有滞后、突跳等典型的非线性动力学...     

Rankine涡作用下激波变形和分叉的数值研究

数值模拟了激波和Rankine涡相互作用,重点研究了波涡相互作用引起的激波结构的变化过程.应用非结构化适应网格下的二阶精度Godunov型的PLM格式来求解Euler方程,对一平面激波与不同涡强Rankine涡相互作用下瞬态激波的运动、发展进行了研究.漩涡与激波间相对强度的大小对激波结构的影响明显,弱相互作用诱导激波变形,强相互作用诱导激波变形并产生分叉.计算结果表明,应用非结构化适应网格的PLM格式所得到的数值解较好地反映了瞬态激波结构的有关特征和信息.     

Design and numerical investigation of swirl recovery vanes for the Fokker 29 propeller

Swirl recovery vanes（SRVs） are a set of stationary vanes located downstream from a propeller, which may recover some of the residual swirl from the propeller, hoping for an improvement in both thrust and efficiency. The SRV concept design for a scaled version representing the Fokker 29 propeller is performed in this paper, which may give rise to a promotion in propulsive performance of this traditional propeller. Firstly the numerical strategy is validated from two aspects of global quantities and the local flow field of the propeller compared with experimental data, and then the exit flow together with the development of propeller wake is analyzed in detail.Three kinds of SRV are designed with multiple circular airfoils. The numerical results show that the swirl behind the propeller is recovered significantly with Model V3, which is characterized by the highest solidity along spanwise, for various working conditions, and the combination of rotor and vane produced 5.76% extra thrust at the design point. However, a lower efficiency is observed asking for a better vane design and the choice of a working point. The vane position is studied which shows that there is an optimum range for higher thrust and efficiency.     

种子叶片自旋下落过程涡系的PIV实验研究

本文利用粒子图像测速技术研究种子叶片自由旋转下落过程中不同涡系的相互作用机理。以典型枫树种子叶片为研究对象,通过对比不同叶片长度、叶面厚度、叶面宽度、下落锥角、自旋角速度、下落速度和下落初始角度等参数对过渡期和稳定期的影响,分析了诱发叶片自旋的外形特征和空间特性。结合特征参数分析,对叶片自旋稳定期开展了PIV流场测量实验,解析了无干扰下种子叶片下落过程中涡系的产生和演化机理。实验结果表明:稳定期气流在叶尖正面位置产生前缘涡（沿展向呈圆锥状结构）,后缘位置产生反方向的后缘涡;两个涡发生相互耦合运动,前缘涡的强度大于后缘涡,从而导致叶面产生锥角。在前缘和叶尖前方观测到较高的速度向上的区域,而在后缘和叶根附近则出现较高的速度向下的区域,从而对种子产生向上的升力,使叶片实现自旋稳定下落。通过枫叶种子自由下落的无干扰PIV测量,初步获得了贴近叶片表面前缘涡的运动性状,验证了后缘涡的存在,结论对单翼型旋转叶片的设计有一定指导意义。