水翼端部间隙泄漏流的压降及黏性损失机理  

INSIGHT INTO PRESSURE DROP AND VISCOUS LOSSES IN TIP-LEAKAGE FLOW BETWEEN A HYDROFOIL AND STATIONARY ENDWALL

作　　者：向秋杰 陈为升 黎耀军[1,2] 刘竹青 Xiang Qiujie;Chen Weisheng;Li Yaojun;Liu Zhuqing(College of Water Resources and Civil Engineering,China Agricultural University,Beijing 100083,China;Beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System,Beijing 100083,China;School of Water Conservancy and Civil Engineering,Northeast Agricultural University,Harbin 150030,China)

机构地区：[1]中国农业大学水利与土木工程学院,北京100083 [2]北京市供水管网系统安全与节能工程技术研究中心,北京100083 [3]东北农业大学水利与土木工程学院,哈尔滨150030

出　　处：《力学学报》2023年第10期2297-2308,共12页Chinese Journal of Theoretical and Applied Mechanics

基　　金：国家自然科学基金资助项目(51679240).

摘　　要：叶顶泄漏流产生的局部压降及黏性损失是导致轴流式水力机械效率下降和轮缘间隙空化的主要原因.为探明间隙泄漏流的黏性损失特性和低压形成机制,以NACA0009水翼为对象,采用超大涡模拟方法(VLES)对翼端间隙流动进行数值模拟,基于平均流动动能转换与输运分析,提出了间隙区黏性损失定量计算模型,研究了翼端间隙区湍动能生成、黏性损失和压降的产生机理及主要影响因素.结果表明,间隙区存在间隙分离涡(TSV)、间隙泄漏涡(TLV)和诱导涡(IV)等流动结构;湍动能生成是导致TSV内压降的主导因素,TLV内压降则主要受湍动能生成和平均动能的对流和扩散效应影响;湍动能耗散导致的翼端区域黏性损失占间隙区黏性损失总量的91.2%.间隙区不同流动结构对湍动能生成的影响存在明显差异,水翼吸力面的强剪切效应主要生成湍动能的■分量,而TLV,TSV和IV等间隙涡结构则主要生成湍动能的■和■分量;湍动能产生机制分析表明,湍动能生成项分量Pvw是TLV和TSV中湍动能生成的主导因素,减小TSV和TLV内的速度梯度■,可有效降低湍动能生成,进而减少翼端区域因湍流耗散导致的黏性损失.研究结果可为间隙流动控制提供参考.Viscous losses and local pressure drop due to tip-clearance flow are the primary factors for efficiency decline and tip-clearance cavitation in axial-flow hydraulic machinery.In this paper,the tip-clearance flow between a NACA0009 hydrofoil and a stationary endwall is investigated using very large eddy simulation,with the aim of exploring the viscous loss properties and the underlying mechanism of pressure drop in the tip-gap region.A quantitative model for the evaluation of viscous losses has been proposed based on the analysis of mean-flow kinetic energy conversion and transport,and the viscous losses and pressure drop associated with the tip-clearance flow are extensively discussed.Gross features of the tip separation vortex(TSV),tip-leakage vortex(TLV),and induced vortex(IV)have been revealed by investigating the mean-flow fields.The production of turbulent kinetic energy(TKE)is found to be the dominant contributor to pressure drop in the TSV,while pressure drop in the TLV is mainly affected by TKE production as well as the convection and transport of mean-flow kinetic energy.In the tip-clearance region,the dissipation of TKE is the main contributor to the viscous losses,accounting for 91.2%of the total losses.The flow structures in the tip gap region have different influences on TKE production.It shows that the shear flow close to the suction surface of the hydrofoil mainly generates the TKE component■,while the tip-clearance vortices mainly generate the components■and■.The analysis of the mechanism of TKE production indicates that the TKE production term component Pvw is the dominant contributor to TKE production in both TLV and TSV,suggesting that reducing the spanwise derivative of the pitchwise velocity∂■∂z in the TSV and TLV is a potential way to reduce TKE production,and then alleviate the viscous losses associated with turbulent dissipation in the tip-clearance region.The findings provide a reference for tip-clearance flow control.

关 键 词：水翼 超大涡模拟 黏性损失 压降 间隙流 

分 类 号：O357.5[理学—流体力学]