椭圆翼梢涡流场的数值模拟
发布时间：2019-01-09 05:54
【摘要】：空化是工程科学的一个重要论题,水利机械系统都可能发生空化现象,空化的发生会改变流动系统的特性,带来诸多问题。例如,在船舶螺旋桨高速运转时,桨叶梢部会产生螺旋形的漩涡空化,它的发生会伴随着强烈的噪声,不利于舰船的隐蔽性,了解这种漩涡流场的非稳态特性是很有意义的。涡流场并非理想的线涡,国内外学者通过理论、实验及数值方法进行研究,以期揭示其流场的特点,但是毫米量级的涡核尺度模拟难度较大,并且其脉动特点及多重涡结构尚不明确,急需进一步的研究。计算平台是开源软件OpenFoam,采用基于隐式压力修正的算法,通过算例验证,模拟的结果与实验值吻合较好,验证了算法的有效性。本论文以椭圆翼为计算模型,通过延迟分离涡模型(DDES)计算流场,采用特殊的网格处理方法,使用GGI处理内外区域的数值传递,实现了椭圆翼的梢涡全湿流场的数值模拟。计算中需要对椭圆翼拖出的梢涡位置进行高精度加密,为了准确加密梢涡,首先用一个分辨率较低的网格进行预算,确定其梢涡的空间坐标,进行高分辨率的网格加密。对两种工况下的梢涡流场进行了计算,从平均流场和脉动流场两方面对流场进行了全面的分析,评估了理论涡模型和模拟耗散涡之间的差别。
[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.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O35
本文编号：2405220
[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.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O35
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