包含多孔材料插件的突扩通道湍流流场及声场计算研究

发布时间：2018-05-11 09:42

本文选题：突扩通道 + 多孔材料　；参考：《华东理工大学》2017年硕士论文

【摘要】：突扩通道流动广泛存在于流体机械与过程装备中,其主要特点是在台阶下游存在分离漩涡运动,造成下游的速度分布不均匀以及流体与固体壁面之间的相互作用,产生结构振动和噪音,不利于安全环保。多孔材料结构是通道内整流消声的常用方法,但是在实际应用过程中,参数的选择基本上依赖于设计与操作人员的经验。参数选择不当,有可能不仅增大了管道内的流动阻力,而且台阶下游的涡运动也可能并未消除。为此,本文研究不同多孔材料参数对突扩通道内的流场及声场的影响,为管道内使用多孔材料插件进行整流与消声的应用提供参考。首先对N-S方程进行体积平均和时均处理,得到了描述多孔介质内部的流动控制方程。对比纯流体控制方程,多孔介质内部流动方程由于惯性阻力与粘性阻力的存在,分别增加了 Forchheimer项和Brinkman项。采用k-ε模型计算湍流应力,多孔介质与纯流体交界面为多孔介质边界条件,求解包含自由空间与多孔材料为一体的流场控制方程。通过控制变量法,分别研究了二维和三维突扩通道内嵌入多孔插件后,流场随渗透率、插件位置和厚度的变化规律。结果表明,多孔插件厚度的增大或者渗透率的减小,都会增大通道内的压力损失,并且它们对压力损失的变化起决定性作用。管道内的涡强和速度脉动强度均随着渗透率的增大而减小,在多孔插件内的涡强与材料渗透率相关。对于包含单频谐波的非定常来流,经过多孔插件后的压力信号、轴向速度脉动、湍动能及湍动能耗散率等参数的波动幅值均降低,相位几乎不发生变化。在流场计算基础上,采用ACTRAN软件对管道内进行声学计算。管道两侧定义为管道声模态面,以模拟无限长管道。声场计算结果揭示了多孔材料插件对低频区噪声的抑制作用,并且随着频率的上升,一部分声波的传播方向从轴向偏转至径向。
[Abstract]:Sudden expansion channel flow widely exists in fluid machinery and process equipment, and its main characteristic is the separation vortex movement in the lower step, which results in uneven velocity distribution downstream and the interaction between fluid and solid wall. Produce structural vibration and noise, which is not conducive to safety and environmental protection. Porous material structure is a common method of rectifying and muffling in channels, but in practical application, the selection of parameters depends on the experience of design and operation personnel. Improper selection of parameters may not only increase the flow resistance in the pipeline, but also the vortex motion downstream of the step may not be eliminated. Therefore, the influence of different porous material parameters on the flow field and sound field in the sudden expansion channel is studied in this paper, which provides a reference for the application of rectifying and silencing by using porous material plug-in the pipeline. First, the volume average and time average of the N-S equation are processed, and the flow control equation is obtained to describe the internal flow of porous media. Compared with the pure fluid governing equations, the internal flow equations in porous media increase the Forchheimer term and the Brinkman term due to the existence of inertial resistance and viscous resistance, respectively. The turbulent stress is calculated by using k- 蔚 model. The interface between porous medium and pure fluid is a porous medium boundary condition, and the governing equation of flow field which contains free space and porous material is solved. By means of variable control method, the variation of flow field with permeability, location and thickness of the plug was studied after embedding the porous plug in the two-dimensional and three-dimensional sudden expansion channels, respectively. The results show that the increase of the thickness of porous plugs or the decrease of permeability will increase the pressure loss in the channel, and they play a decisive role in the change of pressure loss. The vortex strength and velocity pulsation intensity in the pipeline decrease with the increase of permeability, and the vortex strength in the porous plug-in is related to the material permeability. For unsteady flow with single frequency harmonics, the amplitude of pressure signal, axial velocity pulsation, turbulent kinetic energy and turbulent kinetic energy dissipation rate are all decreased, and the phase is almost unchanged. On the basis of flow field calculation, acoustic calculation in pipeline is carried out by ACTRAN software. The two sides of the pipeline are defined as the acoustic modal surface of the pipe to simulate the infinite pipeline. The results of acoustic field calculation reveal the suppression of the noise in the low frequency region by the plug-in of porous materials, and with the increase of the frequency, the propagation direction of part of the sound wave shifts from axial to radial direction.
【学位授予单位】：华东理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O357.5

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