首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到10条相似文献,搜索用时 109 毫秒
1.
为研究不同湍流模型对压缩机总体性能及内部流场数值模拟结果的影响,本文采用3个高雷诺数湍流模型和1个低雷诺数湍流模型对Krain实验研究的离心叶轮和等面积无叶扩压器进行三维定常流场计算,并与相应的实验结果进行对比。研究结果表明,4种湍流模型的数值模拟结果与实验结果均存在差异,这一差异与流量和转速有关。在高转速、小流量工况下,湍流模型对数值模拟结果的影响更为显著。数值模拟预测到的失速流量均与实验值差别较大。而从流场和总体性能两方面来看,与高雷诺数湍流模型相比,低雷诺数湍流模型的模拟精度更高,在设计工况附近区域,数值模拟的效率与实验符合良好。  相似文献   

2.
Current research on pump-turbine units is focused on the unstable operation at off-design conditions, with the characteristic curves in generating mode being S-shaped. Unlike in the traditional water turbines, pump-turbine operation along the S-shaped curve can lead to difficulties during load rejection with unusual increases in the water pressure, which leads to machine vibrations. This paper describes both model tests and numerical simulations. A reduced scale model of a low specific speed pump-turbine was used for the performance tests, with comparisons to computational fluid dynamics(CFD) results. Predictions using the detached eddy simulation(DES) turbulence model, which is a combined Reynolds averaged Naviers-Stokes(RANS) and large eddy simulation(LES) model, are compared with the two-equation turbulence mode results. The external characteristics as well as the internal flow are for various guide vane openings to understand the unsteady flow along the so called S characteristics of a pump-turbine. Comparison of the experimental data with the CFD results for various conditions and times shows that DES model gives better agreement with experimental data than the two-equation turbulence model. For low flow conditions, the centrifugal forces and the large incident angle create large vortices between the guide vanes and the runner inlet in the runner passage, which is the main factor leading to the S-shaped characteristics. The turbulence model used here gives more accurate simulations of the internal flow characteristics of the pump-turbine and a more detailed force analysis which shows the mechanisms controlling of the S characteristics.  相似文献   

3.
为了探讨不同湍流模型在小型潜水泵性能预测中的适用性,本文以QDX6-18-0.75型潜水电泵为研究对象,分别选取Standard k-ε、Reliable k-ε、RNG k-ε、RSM 4种不同湍流模型对小型潜水电泵进行全流场模拟,得到6种工况下泵扬程和效率的预测值,并与试验台测得的数据进行对比分析。结果表明:设计工况下,4种湍流模型的扬程相对误差均小于1.5%,效率相对误差均小于2.5%,满足工程应用需求;小流量工况下,Reliable k-ε模型相对误差最小,扬程最大偏移0.75%,效率最大偏移4.36%;大流量工况下,Standard k-ε模型扬程预测精度高于其它3种湍流模型,RSM模型的效率预测精度最高。综上Reliable k-ε模型的适用性最强,Standard k-ε模型次之。该结论为小型潜水电泵性能预测的可靠性提供依据,并已在产品改型中得以应用。  相似文献   

4.
A second moment turbulence closure using the elliptic-blending equation is introduced to analyze the turbulence and heat transfer in a square sectioned U-bend duct flow. The turbulent heat flux model based on the elliptic concept satisfies the near-wall balance between viscous diffusion, viscous dissipation and temperature-pressure gradient correlation, and also has the characteristics of approaching its respective conventional high Reynolds number model far away from the wall. Also, the traditional GGDH heat flux model is compared with the present elliptic concept-based heat flux model. The turbulent heat flux models are closely linked to the ellipticblending second moment closure which is used for the prediction of Reynolds stresses. The predicted results show their reasonable agreement with experimental data for a square sectioned U-bend duct flow field adopted in the present study.  相似文献   

5.
The paper reported herein presents the laboratory measurement of near-bed flow and turbulence induced by non-submerged spurs protruding from the bank of a meandering-like laboratory flume with smooth rigid bed. The flow property was measured using a 3D acoustic doppler velocimeter for various combinations and locations of spurs in order to assess their effect on mean flow field. Likewise, turbulent characteristics were computed from the measured data for one of the experimental cases. Furthermore, a 2D numerical model was developed for the simulation of mean flow property, turbulent intensities as well as vorticity field using cubic-interpolated pseudoparticle (CIP) numerical technique. The simulated down-stream and cross-stream mean flow property as well as turbulent intensities in shear layer was found to be in good agreement with the experimental results. The numerical simulation of vortices, generated from the tip of the spur, was seen to be reliable. In addition, the migration of small vortices was visualized in the experimental flume using a simple technique.  相似文献   

6.
A mathematical model is set to evaluate the 3-D dense solid-liquid two-phase turbulent flow in a non-clogging mud pump, the flow feature in the impeller channel is simulated with the tool of IPSA. Meanwhile, resort to TECPLOT as the post-processor, the simulation results is visualized. The results show the main flow characteristics: There exists backflow and aberrant velocities at inlet area and a relative velocity slip between two phases; A jet-wake flow pattern is discerned around the shroud-suction side area; The relative velocity vector of solid phase is closer to the pressure surface than that of liquid phase and the trend is more obvious with the increase of diameter; The kinetic energy of turbulence k and the dissipation rate s reach their peaks at the corner of pressure and suction surface. The simulation results show a good agreement with the experimental flow features in the impeller channel, which prove the turbulent model used is valid and provide a theoretical design basis to non-clogging pu  相似文献   

7.
One of the relatively new types of differential pressure flowmeters is the V-Cone (conical or cone) meter. In addition to having many advantages over other types, this flowmeter can also be used in multiphase flows. In the last few decades, many numerical works have been presented for single-phase flows. But in the discussion of two-phase flow, most of the available works are related to experimental research. Therefore, in this paper, the separated two-phase flow with a low gas volume fraction (GVF) has been numerically investigated. For this purpose, an unstructured grid and finite volume numerical method were used. In order to model the two-phase flow and turbulence, the existing approaches were compared. According to the results obtained, the volume of fluid (VOF) method for simulating two-phase flow and the Realizable k-ε model for turbulence modeling lead to better results than other investigated models. Also, by stimulating the flow with the aforementioned methods, it was found that the accuracy of the pressure calculation decreases with the reduction of the superficial velocity and volume fraction of the gas. Furthermore, for a more detailed analysis, the superiority of the Realizable k-ε turbulence model compared to other investigated models was proved quantitatively.  相似文献   

8.
This paper presents a comparative study of a fully coupled, upwind, compressible Navier-Stokes code with three two-equation models and the Baldwin-Lomax algebraic model in predicting transonic/supersonic flow. Thek - ε turbulence model of Abe performed well in predicting the pressure distributions and the velocity profiles near the flow separation over the axisymmetric bump, even though there were some discrepancies with the experimental data in the shear-stress distributions. Additionally, it is noted that this model hasy* in damping functions instead of y+. The turbulence model of Abe and Wilcox showed better agreements in skin friction coefficient distribution with the experimental data than the other models did for a supersonic compression ramp problem. Wilcox’ s model seems to be more reliable than the other models in terms of numerical stability. The two-equation models revealed that the redevelopment of the boundary layer was somewhat slow downstream of the reattachment portion.  相似文献   

9.
垂直管内气固两相流数值模拟计算--颗粒动力学理论方法   总被引:3,自引:0,他引:3  
基于气固两相流体动力学模型、颗粒动力学理论的颗粒脉动动能模型(KTGF)和气体湍流动能模型(SGS),对气固两相垂直上升流动进行数值计算,模拟计算结果得到了与试验研究所揭示的环—核流动结构。模拟计算与Miller和Gidaspow (1992)试验结果进行了比较,颗粒相浓度、速度和颗粒相动力粘性系数分布与试验值基本吻合  相似文献   

10.
采用纯黏性润滑方程和基于层流模式、SST k-ω湍流模式的N-S方程,对环面节流静压气体润滑推力轴承内的压力分布进行了研究,分析了随着气膜厚度的变化,轴承流场内压力的变化及其变化机理。实验证明,在轴承厚度很小时两种方程求得的压力值与实验结果一致,然而随着气膜厚度的增大,采用纯黏性润滑方程计算所得结果的偏差很大,而采用N-S方程计算所得结果与实验结果基本一致,但在逆压力梯度段存在偏差;SST k-ω 湍流模式能较好地处理湍流剪切应力在逆压梯度边界层内的输运和激波与边界层的相互作用,准确模拟出气膜入口附近复杂的流动状态。   相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号