排序方式: 共有146条查询结果,搜索用时 15 毫秒
51.
边界层逆压梯度作用下的流动是许多工程中的一个基础问题,由于逆压梯度作用,流动形态复杂,使得数值模拟有很大的难度。基于雷诺平均纳维‐斯托克斯RANS(Reynolds Averaged Navier‐Stokes)方程对二维平板逆压梯度边界层作数值计算研究,选取6种代表性的湍流模式,得到局部摩擦系数的数值解,与实验值比较,发现k‐ω模式具有很好的精度。基于该湍流模式,给出了湍动能分布,该结果有助于认识逆压梯度边界层流动的复杂特征。 相似文献
52.
Prediction of separation flows around a 6:1 prolate spheroid using RANS/LES hybrid approaches 总被引:2,自引:0,他引:2
Zhixiang Xiao Yufei Zhang Jingbo Huang Haixin Chen Song Fu 《Acta Mechanica Sinica》2007,23(4):369-382
This paper presents hybrid Reynolds-averaged Navier–Stokes (RANS) and large-eddy-simulation (LES) methods for the separated
flows at high angles of attack around a 6:1 prolate spheroid. The RANS/LES hybrid methods studied in this work include the
detached eddy simulation (DES) based on Spalart–Allmaras (S–A), Menter’s k–ω shear-stress-transport (SST) and k–ω with weakly nonlinear eddy viscosity formulation (Wilcox–Durbin+, WD+) models and the zonal-RANS/LES methods based on the
SST and WD+ models. The switch from RANS near the wall to LES in the core flow region is smooth through the implementation
of a flow-dependent blending function for the zonal hybrid method. All the hybrid methods are designed to have a RANS mode
for the attached flows and have a LES behavior for the separated flows. The main objective of this paper is to apply the hybrid
methods for the high Reynolds number separated flows around prolate spheroid at high-incidences. A fourth-order central scheme
with fourth-order artificial viscosity is applied for spatial differencing. The fully implicit lower–upper symmetric-Gauss–Seidel
with pseudo time sub-iteration is taken as the temporal differentiation. Comparisons with available measurements are carried
out for pressure distribution, skin friction, and profiles of velocity, etc. Reasonable agreement with the experiments, accounting
for the effect on grids and fundamental turbulence models, is obtained for the separation flows.
The project supported by the National Natural Science Foundation of China (10502030 and 90505005). 相似文献
53.
对超声速冷流条件下用于超燃冲压发动机的凹腔火焰稳定器的自激振荡特性进行研究.采用混合RANS/LES方法对非定常流场进行数值模拟,考虑了凹腔的长深比和后缘角度两个关键参数.混合RANS/LES方法很好的捕捉到流场非定常大尺度结构并揭示了凹腔自由剪切层的演化过程.对凹腔压力振荡历程进行幅频分析,所得到的频率和理论分析结果与文献计算结果符合的很好.结果表明,凹腔的长深比和后缘角度对凹腔自激振荡特性都有很大的影响.随着凹腔长深比的减小,振荡能量趋于集中到某些频率对应的振荡模式上.随着凹腔后缘倾角的减小,大部分频率对应的振荡很快的被削弱;相对于陡后缘凹腔,小角度后缘凹腔只有较高频率对应的振荡模式存在. 相似文献
54.
55.
56.
High‐order accurate DG discretization is employed for Reynolds‐averaged Navier–Stokes equations modeling of complex shock‐dominated, unsteady flow generated by gas issuing from a shock tube nozzle. The DG finite element discretization framework is used for both the flow field and turbulence transport. Turbulent flow in the near wall regions and the flow field is modeled by the Spalart–Allmaras one‐equation model. The effect of rotation on turbulence modeling for shock‐dominated supersonic flows is considered for accurate resolution of the large coherent and vortical structures that are of interest in high‐speed combustion and supersonic flows. Implicit time marching methodologies are used to enable large time steps by avoiding the severe time step limitations imposed by the higher order DG discretizations and the source terms. Sufficiently high mesh density is used to enable crisp capturing of discontinuities. A p ? type refinement procedure is employed to accurately represent the vortical structures generated during the development of the flow. The computed solutions showed qualitative agreement with experiments. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
57.
58.
Particles or droplets dispersed in turbulent flows at sufficiently high volume loadings lead to modifications of turbulence characteristics. More specifically, in a detailed experimental investigation by Poelma and coworkers, where the particle phase moves with a non-zero mean velocity relative to the fluid phase, it was found that anisotropic Reynolds-stress dissipation is induced. Recently, we have proposed a model that can account for this effect in RANS-based and PDF method simulations. In our previous work, however, no simulation results of the RANS model formulation were presented. In the present work, a new compact tensorial RANS formulation is presented and the new formulation is validated against the experimental data of Poelma and coworkers. 相似文献
59.
A three-dimensional unstructured finite-volume code developed for RANS computations with the artificial compressibility approach is described. The code is applied to prediction of adiabatic effectiveness of endwall flush-slot-cooling for a stator vane passage. Results obtained with the Spalart–Allmaras and the Menter SST turbulence models are presented and discussed in comparison with measurements and with the data computed using the FLUENT commercial software package. 相似文献
60.
Accurate prediction of the hydrodynamic forces and moments acting on a manoeuvring marine vehicle using Reynolds averaged Navier–Stokes simulations requires sufficient mesh resolution to capture off‐body vortical structures. Because the path of these structures is not known a priori, a vortex identification and capture strategy is required alongside an iterative mesh adaption process. An improved version of the VORTFIND algorithm, which can identify multiple vortices of variable strength and rotational direction using a K‐means algorithm is described. The algorithm is applied to velocity fields generated from Reynolds averaged Navier–Stokes simulations to increase the mesh resolution in the vortex core region, ensuring sufficient mesh density to capture the downstream propagation of the vortex for a submarine hull at drift and ship propeller–rudder interaction.Copyright © 2012 John Wiley & Sons, Ltd. 相似文献