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排序方式: 共有115条查询结果,搜索用时 984 毫秒
41.
OpenFOAM模拟风洞边界层风场 总被引:2,自引:0,他引:2
使用开源CFD软件OpenFOAM进行了风洞边界层风场的模拟,通过模拟一方面验证了采用开源CFD软件OpenFOAM进行计算风工程模拟的有效性,另一方面也对模拟结果中边界层风场的特性进行了一定的讨论。 相似文献
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M.F. HuangI.W.H Lau C.M. Chan K.C.S. Kwok G. Li 《Journal of Wind Engineering & Industrial Aerodynamics》2011,99(11):1126-1138
Up till recent years, predicting wind loads on full-scale tall buildings using Large Eddy Simulation (LES) is still impractical due to a prohibitively large amount of meshes required, especially in the vicinity of the near-wall layers of the turbulent flow. A hybrid approach is proposed for solving pressure fluctuations of wind flows around tall buildings based on the Reynolds Averaged Navier-Stokes (RANS) simulation, which requires coarse meshes, and the mesh-free Kinematic Simulation (KS). While RANS is commonly used to provide mean flow characteristics of turbulent airflows, KS is able to generate an artificial fluctuating velocity field that satisfies both the flow continuity condition and the specific energy spectra of atmospheric turbulence. The kinetic energy is split along three orthogonal directions to account for anisotropic effects in atmospheric boundary layer. The periodic vortex shedding effects can partially be incorporated by the use of an energy density function peaked at a Strouhal wave number. The pressure fluctuations can then be obtained by solving the Poisson equation corresponding to the generated velocity fluctuation field by the KS. An example of the CAARC building demonstrates the efficiency of the synthesized approach and shows good agreements with the results of LES and wind tunnel measurements. 相似文献
44.
《International Journal of Hydrogen Energy》2023,48(39):14896-14907
Using solid obstacles to accelerate the deflagration to detonation transition (DDT) process induces additional thrust loss, and fluidic obstacles can alleviate this problem to a certain extent. A detailed simulation is conducted to investigate the effects of multiple groups of fluidic obstacles on the flame acceleration and DDT process under different initial velocities and gas types. The results show that, initially, the propagation of reflected shock wave formed by jet impingement is opposite to the flame acceleration direction, thus increasing the initial jet velocity will hinder the flame acceleration. Later, the vortex structure and enhanced turbulence can promote flame acceleration. As the flame accelerates, the virtual blockage ratio of the fluidic obstacles decreases, and increasing initial jet velocity or using reactive jet gases both affect the virtual blockage ratio. Further, increasing initial jet velocity or using reactive jet gases can shorten the detonation initiation time and distance. Compared with solid obstacles, it is concluded that fluidic obstacles can achieve faster detonation initiation with a smaller blockage ratio. Overall, the detonation phenomena in this study are all triggered by hot spots formed by the interaction between reflected waves and distorted flame, but the formation of reflected waves varies. 相似文献
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Experimental and numerical investigations of aerodynamic loads and 3D flow over non‐rotating MEXICO blades
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Ye Zhang Thijs Gillebaart Alexander van Zuijlen Gerard van Bussel Hester Bijl 《风能》2017,20(4):585-600
This paper presents the experimental and numerical study on MEXICO wind turbine blades. Previous work by other researchers shows that large deviations exist in the loads comparison between numerical predictions and experimental data for the rotating MEXICO wind turbine. To reduce complexities and uncertainties, a non‐rotating experimental campaign has been carried out on MEXICO blades Delft University of Technology. In this new measurement, quasi‐2D aerodynamic characteristics of MEXICO blades on three spanwise sections are measured at different inflow velocities and angles of attack. Additionally, RANS simulations are performed with OpenFOAM‐2.1.1 to compare numerical results against measured data. The comparison and analysis of aerodynamic loads on the blade, where three different airfoil families and geometrical transition regions are used, show that for attached flow condition, RANS computation predicts excellent pressure distribution on the NACA airfoil section (r/R = 0.92) and good agreement is observed on the DU (r/R = 0.35) and RISØ (r/R = 0.60) airfoil sections. Unexpected aerodynamic characteristics are observed at the intermediate transition regions connecting the RISØ and DU airfoils, where sudden lift force drop is found at the radial position r/R = 0.55. Through numerical flow visualization, large‐scale vortical structures are observed on the suction side of the blade near the mid‐span. Moreover, counter‐rotating vortices are generated behind the blade at locations where unexpected loads occurs. Consequently, the RISØ airfoil could not give expected 2D aerodynamic characteristics because of upwash/downwash effects induced by these counter‐rotating vortices, which make 3D effects play an important role in numerical modeling when calculating the aerodynamic loads for MEXICO rotor. ©2016 The Authors Wind Energy Published by John Wiley & Sons Ltd 相似文献
47.
Nima Samkhaniani 《亚洲传热研究》2017,46(4):331-346
In this paper, a direct numerical simulation of a two‐phase incompressible gas–liquid flow for simulation of bubble motion and convective heat transfer in a microtube is presented. The microtube radius is 10 μm. The interface between the two phases is tracked by the volume of fluid method with the continuous surface force model. Newtonian flows are solved using a finite volume scheme based on the PISO algorithm. Numerical simulation is done on an axisymmetric domain with a periodic boundary condition for different values of pressure gradient, void fraction, and bubble period. Mean pressure gradient is fixed for each simulation. The superficial Reynolds numbers of gas and liquid phases studied are 0.3 to 7 and 5 to 210, respectively. Numerical results are coincident with the Serizawa regime map, and there is a linear relation between the void fraction and gas flow ratio. Simulation shows local Nusselt number increases in the presence of a gas bubble. 相似文献
48.
提出嵌入方箱式防波堤的垂荡式振荡水柱(OWC)波能装置,利用开源计算流体动力学库OpenFOAM及工具箱waves2foam,对该波能装置的能量转换效率和水动力特性开展数值研究.采用流体体积法(VOF)捕捉气液界面,利用Rigid-Body Dynamic网格技术求解垂荡运动.在不同入射波频下,探究垂直线性弹簧约束(用无量纲弹簧刚度表示)对OWC波能装置的波能转换效率、反射系数、透射系数、能量耗散系数、相对压降、有效相对振荡幅度和相位差等的影响.结果表明,结构物适当的垂荡运动有利于提升OWC装置在特定频率条件下的波能转换效率;振荡水柱和结构物间的运动相位差是决定能量转换效率的关键因素;为了提升能量转换效率,调节结构物的垂荡运动来控制相位差的措施是可行的. 相似文献
49.
The streamlined weirs are a special type of weirs, designed on the basis of airfoil theory. Because of their particular design, they have some merits compared to the other types of weirs, such as; high discharge coefficient, more stability of overflow and less fluctuations of water free surface. In the present study, a numerical simulation performed using an open source software namely, OpenFOAM, to give details about the flow structure over, up- and downstream of these weirs. Also, an experimentation setup was devised to evaluate the numerical results and determine the best numerical model. Analyzing the results of different turbulence models including; standard k-ε, realizable k-ε, RNG k-ε, k-ω SST, and Reynolds stress LRR, indicated that all the aforementioned models accurately estimate the flow field and hydraulic parameters. However, the k-ω SST model gives more accurate results, very close to the experimental data especially for the Reynolds stresses. Accordingly, the k-ω SST turbulence model was chosen as the best turbulence model for analyzing the flow over the streamlined weirs. Numerical results for different relative eccentricities show that, by increasing the relative eccentricity, the flow velocity over the crest of the weirs increases and accordingly the pressure in such section decreases. For a constant flow discharge upstream of different types of the streamlined weirs, the lowest bed pressure and the most probable potential of cavitation belongs to a circular-crested weir (a streamlined weir with a relative eccentricity of unity). Furthermore, the greatest bed shear stresses and the compressive forces occur downstream of the circular-crested weir. Thus, downstream of a circular-crested weir is responsible for larger potential of bed erosion. This is partly due to the formation of shock waves, reduction of the flow depth, and enhancement of the flow velocity downstream of a circular-crested weir. Moreover, the lowest bed shear stresses were observed upstream of the circular-crested weir. Therefore, upstream of a circular-crested weir shows the greatest potential of sedimentation. Finally, applying the streamlined weirs with an appropriate curvature, diminishes the unfavorable flow conditions, as observed for the circular-crested weir, being the safer and economic hydraulic structures. 相似文献
50.
Hydroelectric facilities impact water temperature; low velocities in a reservoir increase residence time and enhance heat exchange in surface layers. In this study, an unsteady three-dimensional model was developed to predict the temperature dynamics in the McNary Dam forebay. The model is based on the open-source code OpenFOAM. RANS equations with the Boussinesq approximation were used to solve the flow field. A realizable κ-ε model that accounts for the production of wind turbulence was developed. Solar radiation and convective heat transfer at the free surface were included. The result of the model was compared with the field data collected on August 18, 2004. Changes in diurnal stratification were adequately predicted by the model. Observed vertical and lateral temperature distributions were accurately captured. Results indicate that the model can be used as a numerical tool to assess structural and operational alternatives to reduce the forebay temperature. 相似文献