格栅—空腔绕流流场自激振荡研究及其在高速列车中的应用

发布时间：2018-02-26 21:23

本文关键词： 格栅-空腔绕流自激振荡振荡频谱高速列车通风格栅车辆设备舱　出处：《北京交通大学》2017年博士论文　论文类型：学位论文

【摘要】：很多设备、建筑、载运工具都具有通风格栅,格栅与其内侧空间共同构成格栅-空腔结构。当流体沿切向流经该结构时即形成格栅-空腔绕流。一定条件下,此类流场会产生自激振荡现象。流场自激振荡是一类稳定的周期性振荡过程,能够导致结构振动、流动噪声等问题,也会影响设备通风散热或空调系统运行。同时,流场自激振荡过程包含着复杂的流动现象和很多流体力学基本问题。对于该问题的研究具有重要的工程应用及理论研究意义。本文以地面载运工具为应用对象,使用数值模拟方法对格栅-空腔绕流流场自激振荡现象进行研究。主要研究内容有:格栅-空腔绕流流场自激振荡产生机理、基本特征、激发条件、变化规律、控制方法及其在高速列车中的应用,以期加深对该流动现象产生原因的理解,明确流场自激振荡的时频特征及空间分布特征,提出流场自激振荡频率、幅值的预测方法,为解决流场自激振荡在载运工具运行中所引起的一系列问题以及相关设计研究工作提供技术及理论依据。建立了格栅-空腔绕流数值模拟模型,使用粒子图像测速法对模型进行了验证。得到了流场变化过程,分析了流场自激振荡的产生原因。使用频谱分析方法,得到了不同流动参数的时频特征及其空间分布规律,明确了自激振荡基本特征。结果表明:大尺度涡团的运动导致格栅-空腔绕流流场产生自激振荡;大尺度涡团的形成与格栅周围涡量的聚集过程密切相关;不同位置的振荡频率相同;沿来流方向,压力振荡幅值呈现先增后减的变化趋势。研究了流场自激振荡的激发条件。得到的主要结论有:不同条件下,流场可能处于非振荡状态、过渡状态及自激振荡状态。当流动处于相对稳定的状态时,若流场振荡幅值大于零且振荡幅值变化率接近零则表明流场中存在自激振荡现象。当分离边缘边界层动量厚度δd较小,流动雷诺数Reδ较大,格栅间隔长高比G/H较大时,流场自激振荡更容易被激发。当空腔相对长度Lc/L1.5,空腔相对高度Hc/L5时,空腔壁面不会对流场自激振荡造成影响。对流场自激振荡变化规律进行了研究,包括流动状态研究及模式转变研究。得到了不同流动状态、振荡模式下振荡频率、幅值的变化规律。主要结论有:格栅-空腔绕流流动状态可以用参数λ=(Reδ)~(1/2)/(δd/G)进行区分。随着λ的增加,流场将经历三种流动状态。在不同流动状态下,振荡频率、幅值的变化规律具有较大差异。随着格栅间隔长高比G/H的增加,流动状态转变的临界参数λ_1和λ_2均呈线性减小。随着λ的增加,模式转变发生的临界参数(L/G)_j呈单调下降趋势。两者之间的关系可以用指数函数表示。对流场振荡控制方法进行了分析。分别对两种典型控制手段对于流场振荡的抑制效果进行了评价。提出了改变格栅肋片角度控制流场振荡的方法。总体来看,在分离边缘添加斜面能够有效降低格栅-空腔绕流流场的自激振荡强度。而在冲击边缘切割斜面对流场振荡的抑制效果不明显。改变格栅肋片角度对流场振荡的抑制效果较好。建立了考虑通风格栅影响的高速列车设备舱流动数值模拟模型,着重对通风格栅附近的流动情况进行了分析。模拟结果表明:高速列车设备舱通风格栅附近会产生流场自激振荡现象。在其影响下,高速列车设备舱裙板受到周期性气动载荷的作用。
[Abstract]:A lot of equipment, buildings, vehicles have ventilation grille grille, its inner space constitute the grille - cavity structure. When the fluid flows through the tangential structure is formed around the grille flow cavity. Under certain conditions, this kind of flow will produce self oscillation. The flow field is a kind of self-excited oscillation and stable periodic oscillation the process, can lead to structural vibration, flow noise and other issues, will also affect the equipment ventilation or air conditioning system operation. At the same time, the flow field oscillation process contains the basic problem of complex flow phenomena and many fluid mechanics. It has important engineering application and theoretical significance for the study of the problem. This article takes the ground vehicles for application the object, using numerical simulation method to study the grid - cavity flow around the self oscillation of the flow field. The main contents are: Grid - cavity flow oscillation generated The mechanism, basic characteristics, excitation conditions, variation, control method and its application in high speed train, in order to deepen the causes of the flow phenomena, clear flow self-excited oscillation frequency characteristics and spatial distribution characteristics, the flow field of self-excited oscillation frequency, amplitude value prediction method, to solve the technology and theory based on the flow field of self-excited oscillations in a series of problems caused by carrying tools in operation and related design work. A numerical simulation of flow around grid - cavity model, using particle image velocimetry method to validate the model. The flow field change process, analyzes the causes of the self-excited oscillation flow. Using spectrum analysis method. The different flow parameters and spatial distribution features of time-frequency, clear the basic characteristics of the self-excited oscillation. The results show that the movement of vortexes in Grid - cavity flow The flow field of self-excited oscillation; closely related to the formation and accumulation of vorticity around the grille vortexes at the different positions of the same; oscillation frequency; along the flow direction, pressure oscillation amplitude showed a trend of first increase and then decrease. The excitation conditions flow self-excited oscillation. The main conclusions are: different conditions under the field in a non oscillatory state, transition state and self-excited oscillation. When the flow is in a relatively stable state, if the flow oscillation amplitude is greater than zero and the oscillation amplitude change rate is close to zero indicates that the self-excited oscillation phenomenon in the flow field. When the separation edge boundary layer momentum thickness Reynolds number D is small, Re 8 the larger, taller than G/H large grid spacing, flow field oscillation is excited easily. When the relative length of the Lc/L1.5 cavity, the cavity relative height of Hc/L5, the cavity surface will not affect the flow field of self-excited oscillation Ring. The flow field oscillation changes were studied, including the change of flow state and study mode. Under different flow conditions, oscillation frequency of the oscillation mode, the amplitude of variation. The main conclusions are: Grid - cavity flow around the state with parameter = (Re delta) ~ (1/2) / (8 d/G) were distinguished. With lambda increases, the flow field will experience the three flow. Under different flow conditions, the oscillation frequency, with larger differences in variation amplitude. With the increase of G/H grid interval height, flow state transition critical parameters of a _1 and a _2 were decreased linearly with lambda. Increase the critical parameters change mode (L/G) _j is a monotone decreasing trend. The relationship between the two can be expressed by exponential function. The flow field oscillation control methods are analyzed respectively. Two kinds of typical control methods for the inhibitory effect of flow oscillation The evaluation method is put forward. The change of fin angle control grid flow oscillation. Overall, add a bevel can effectively reduce the intensity of the self-excited oscillation cavity flow around the grille in the separation edge. With the impact of the cutting edge oblique face the inhibitory effect of flow oscillation is not obvious. The best inhibition grille rib angle convection field oscillation the change. A high-speed train equipment cabin numerical flow simulation model considering the influence of ventilation grille, especially near the flow situation of the ventilation grille is analyzed. The simulation results show that near the high-speed train compartment ventilation grid will have a flow of self oscillation. Under its influence, the high-speed train equipment cabin apron by action cycle of the aerodynamic load.

【学位授予单位】：北京交通大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：U270.1

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