發(fā)布時(shí)間：2019-01-09 05:54

【摘要】：空化是工程科學(xué)的一個(gè)重要論題,水利機(jī)械系統(tǒng)都可能發(fā)生空化現(xiàn)象,空化的發(fā)生會(huì)改變流動(dòng)系統(tǒng)的特性,帶來(lái)諸多問(wèn)題。例如,在船舶螺旋槳高速運(yùn)轉(zhuǎn)時(shí),槳葉梢部會(huì)產(chǎn)生螺旋形的漩渦空化,它的發(fā)生會(huì)伴隨著強(qiáng)烈的噪聲,不利于艦船的隱蔽性,了解這種漩渦流場(chǎng)的非穩(wěn)態(tài)特性是很有意義的。渦流場(chǎng)并非理想的線渦,國(guó)內(nèi)外學(xué)者通過(guò)理論、實(shí)驗(yàn)及數(shù)值方法進(jìn)行研究,以期揭示其流場(chǎng)的特點(diǎn),但是毫米量級(jí)的渦核尺度模擬難度較大,并且其脈動(dòng)特點(diǎn)及多重渦結(jié)構(gòu)尚不明確,急需進(jìn)一步的研究。計(jì)算平臺(tái)是開(kāi)源軟件OpenFoam,采用基于隱式壓力修正的算法,通過(guò)算例驗(yàn)證,模擬的結(jié)果與實(shí)驗(yàn)值吻合較好,驗(yàn)證了算法的有效性。本論文以橢圓翼為計(jì)算模型,通過(guò)延遲分離渦模型(DDES)計(jì)算流場(chǎng),采用特殊的網(wǎng)格處理方法,使用GGI處理內(nèi)外區(qū)域的數(shù)值傳遞,實(shí)現(xiàn)了橢圓翼的梢渦全濕流場(chǎng)的數(shù)值模擬。計(jì)算中需要對(duì)橢圓翼拖出的梢渦位置進(jìn)行高精度加密,為了準(zhǔn)確加密梢渦,首先用一個(gè)分辨率較低的網(wǎng)格進(jìn)行預(yù)算,確定其梢渦的空間坐標(biāo),進(jìn)行高分辨率的網(wǎng)格加密。對(duì)兩種工況下的梢渦流場(chǎng)進(jìn)行了計(jì)算,從平均流場(chǎng)和脈動(dòng)流場(chǎng)兩方面對(duì)流場(chǎng)進(jìn)行了全面的分析,評(píng)估了理論渦模型和模擬耗散渦之間的差別。
[Abstract]:Cavitation is an important topic in engineering science. Cavitation may occur in hydraulic and mechanical systems. Cavitation will change the characteristics of flow system and bring many problems. For example, when the ship's propeller is running at high speed, the tip of the propeller will produce a spiral vortex cavitation, which will be accompanied by strong noise, which is not conducive to the ship's concealment. It is very meaningful to understand the unsteady characteristics of the swirl flow field. Eddy current field is not an ideal linear vortex. Scholars at home and abroad have studied it by theoretical, experimental and numerical methods in order to reveal the characteristics of its flow field. However, it is difficult to simulate the eddy core in millimeter scale. The pulsation characteristics and multi-vortex structure are not clear, and need further study. The calculation platform is an open source software OpenFoam, which uses an algorithm based on implicit pressure correction. The simulation results are in good agreement with the experimental data and the validity of the algorithm is verified by an example. In this paper, the elliptical wing is taken as the computational model, the flow field is calculated by the delayed separation vortex model (DDES), the special mesh processing method is adopted, and the numerical transfer in the inner and outer region is processed by using GGI. The numerical simulation of the full wet flow field of the tip vortex of the elliptical wing is realized. It is necessary to encrypt the position of the vortex in the elliptical wing with high precision. In order to encrypt the vortex accurately, a lower resolution grid is used to estimate the spatial coordinates of the vortex, and the high resolution mesh is used to encrypt the vortex. In this paper, the tip vortex field under two conditions is calculated, and the difference between the theoretical vortex model and the simulated dissipative vortex is evaluated from the mean flow field and the pulsating flow field.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：O35

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