本文選題：突擴(kuò)通道 + 多孔材料　； 參考：《華東理工大學(xué)》2017年碩士論文

【摘要】：突擴(kuò)通道流動(dòng)廣泛存在于流體機(jī)械與過(guò)程裝備中,其主要特點(diǎn)是在臺(tái)階下游存在分離漩渦運(yùn)動(dòng),造成下游的速度分布不均勻以及流體與固體壁面之間的相互作用,產(chǎn)生結(jié)構(gòu)振動(dòng)和噪音,不利于安全環(huán)保。多孔材料結(jié)構(gòu)是通道內(nèi)整流消聲的常用方法,但是在實(shí)際應(yīng)用過(guò)程中,參數(shù)的選擇基本上依賴于設(shè)計(jì)與操作人員的經(jīng)驗(yàn)。參數(shù)選擇不當(dāng),有可能不僅增大了管道內(nèi)的流動(dòng)阻力,而且臺(tái)階下游的渦運(yùn)動(dòng)也可能并未消除。為此,本文研究不同多孔材料參數(shù)對(duì)突擴(kuò)通道內(nèi)的流場(chǎng)及聲場(chǎng)的影響,為管道內(nèi)使用多孔材料插件進(jìn)行整流與消聲的應(yīng)用提供參考。首先對(duì)N-S方程進(jìn)行體積平均和時(shí)均處理,得到了描述多孔介質(zhì)內(nèi)部的流動(dòng)控制方程。對(duì)比純流體控制方程,多孔介質(zhì)內(nèi)部流動(dòng)方程由于慣性阻力與粘性阻力的存在,分別增加了 Forchheimer項(xiàng)和Brinkman項(xiàng)。采用k-ε模型計(jì)算湍流應(yīng)力,多孔介質(zhì)與純流體交界面為多孔介質(zhì)邊界條件,求解包含自由空間與多孔材料為一體的流場(chǎng)控制方程。通過(guò)控制變量法,分別研究了二維和三維突擴(kuò)通道內(nèi)嵌入多孔插件后,流場(chǎng)隨滲透率、插件位置和厚度的變化規(guī)律。結(jié)果表明,多孔插件厚度的增大或者滲透率的減小,都會(huì)增大通道內(nèi)的壓力損失,并且它們對(duì)壓力損失的變化起決定性作用。管道內(nèi)的渦強(qiáng)和速度脈動(dòng)強(qiáng)度均隨著滲透率的增大而減小,在多孔插件內(nèi)的渦強(qiáng)與材料滲透率相關(guān)。對(duì)于包含單頻諧波的非定常來(lái)流,經(jīng)過(guò)多孔插件后的壓力信號(hào)、軸向速度脈動(dòng)、湍動(dòng)能及湍動(dòng)能耗散率等參數(shù)的波動(dòng)幅值均降低,相位幾乎不發(fā)生變化。在流場(chǎng)計(jì)算基礎(chǔ)上,采用ACTRAN軟件對(duì)管道內(nèi)進(jìn)行聲學(xué)計(jì)算。管道兩側(cè)定義為管道聲模態(tài)面,以模擬無(wú)限長(zhǎng)管道。聲場(chǎng)計(jì)算結(jié)果揭示了多孔材料插件對(duì)低頻區(qū)噪聲的抑制作用,并且隨著頻率的上升,一部分聲波的傳播方向從軸向偏轉(zhuǎn)至徑向。
[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.
【學(xué)位授予單位】：華東理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：O357.5

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