共查询到18条相似文献,搜索用时 140 毫秒
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基于七阶加权紧致非线性格式(WCNS-E8T7),结合延迟分离涡模拟(DDES)和Ffowcs WilliamsHawkings声比拟方法,对亚临界雷诺数下单圆柱、圆柱-翼型的分离涡/涡致噪声问题进行了数值模拟.针对亚临界雷诺数下圆柱尾迹中的转捩问题,发展了基于γ-Reθ模型高精度转捩-延迟分离涡模拟(Tran-DDES)方法,并与传统基于全湍流剪切应力输运(SST)模型的高精度DDES方法进行了对比.单圆柱模拟结果表明:传统SST-DDES方法会造成平均流场的回流区增大,压差阻力偏小等问题;而添加转捩模型的Tran-DDES方法与实验符合得很好.圆柱尾迹中添加翼型后,翼型对圆柱附近流场产生影响,使SST-DDES方法造成的圆柱后回流区偏大的问题减弱,并与Tran-DDES模拟结果差异变小.但在脉动量预测以及脉动产生的噪声预测方面, Tran-DDES方法仍与实验符合得更好. 相似文献
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采用高精度直接数值模拟方法,研究平板可压缩流边界层转捩后期过程中的上喷和下扫运动.模拟结果清楚地显示了边界层转捩过程中的上喷下扫运动的复杂现象,展示与典型涡系及尖峰结构的紧密联系.详细剖析多层次的上喷下扫运动的形成机制,数值结果证实了实验的新发现,并进行相应的机理分析. 相似文献
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逆压梯度下层流分离泡转捩的大涡模拟 总被引:7,自引:1,他引:6
本文采用有限体积法,发展了适合复杂几何边界条件的可压缩流动大涡模拟程序,通过对槽道湍流的计算,验证了程序的可靠性。对低雷诺数、逆压梯度环境中的层流分离泡转捩现象进行了数值模拟,分析了其统计特性及大尺度相干结构的演化规律.初步的结果表明:大涡模拟可以很好地处理层流分离泡转捩问题,既能给出满意的统计平均结果,又可以通过相干结构的演化细致描述分离泡转捩的动力学过程。 相似文献
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高负荷低压涡轮边界层转捩预测及其机理分析 总被引:1,自引:0,他引:1
本文利用数值模拟方法在不同雷诺数、自由来流湍流度(FSTI)下对某高负荷低压涡轮叶型边界层转捩流动进行了数值模拟,并与实验测试结果进行了对比。结果表明:该转捩模型在不同的雷诺数和FSTI情况下均可以得到满意的数值计算结果,而仪仪利用湍流模型得不到合理的计算结果;当进口特征雷诺数较低时,叶型表面长分离泡的出现在很大范围内改变了壁面处的静压分布;随着自由来流湍流度的提高,叶型吸力面分离点的位置靠后且其对应的再附点位置靠前,即分离泡长度较短,高来流湍流度可以减小叶型吸力面的分离区域,减小叶型损失。而较低的自由流湍流度则在叶型尾缘对应着较长的分离泡,增大了流动分离再附的预测难度。 相似文献
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应用分离涡模型计算斜圆柱孔气膜冷却 总被引:5,自引:0,他引:5
分离涡模型(DES,Detached eddy simulation)兼有雷诺时均湍流模型计算量较小和大涡模拟计算精度高的优点。本文利用DES对平板单斜圆柱孔的气膜冷却进行了数值模拟,并将结果同RANS湍流模型的计算结果以及实验数据相比较,表明DES能有效弥补RANS湍流模型在计算三维不均匀非定常湍流场的不足,更接近实际地反映了气膜冷却中的流动和换热的本质规律。 相似文献
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基于边界层转捩后阶段的高精度直接数值模拟结果,发现流向条纹结构的低速条纹的演化过程中存在不连续现象,以及随高速条纹的发展会出现称之为"高速斑"的新特性. 通过详细剖析边界层转捩过程中的复杂涡系结构以及上喷下扫流动现象,证实流向高低速条纹新特性与流场涡系结构的演化过程紧密相关.
关键词:
流向条纹
边界层
转捩
直接数值模拟 相似文献
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可压缩流动稳定性方程求解与转捩预测 总被引:1,自引:0,他引:1
讨论了Rayleigh逆迭代法与边界层渐近匹配合的方法,并应用于求解高速可压缩边界怪流动稳定性和预报转捩点的数值计算方法。给出了平板边界层第一模式的稳定性分析和转捩区数值预报结果,与已有的实验结果进行了比较。 相似文献
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Guoliang Xu & Song Fu 《advances in applied mathematics and mechanics.》2014,6(4):523-538
It is very important to predict the bypass transition in the simulation of flows through turbomachinery. This paper presents a four-equation eddy-viscosity turbulence transition model for prediction of bypass transition. It is based on the SST turbulence model and the laminar kinetic energy concept. A transport equation for the non-turbulent viscosity is proposed to predict the development of the laminar kinetic energy in the pre-transitional boundary layer flow which has been observed in experiments. The turbulence breakdown process is then captured with an intermittency transport equation in the transitional region. The performance of this new transition model is validated through the experimental cases of T3AM, T3A and T3B. Results in this paper show that the new transition model can reach good agreement in predicting bypass transition, and is compatible with modern CFD software by using local variables. 相似文献
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An experimental study has been conducted to investigate the combined influence of length scale of free-stream turbulence, A, and cylinder diameter, D, on heal transfer from slightly heated circular cylinders in cross flow. By using a hot-wire anemometer, spectrum analysis of its signal with a Fourier analyzer is employed to investigate the separated shear layer formed behind the circular cylinder. A resistance thermometer is used to measure the time-averaged temperature behind the cylinder and the power-spectral density of the temperature fluctuation in the thermal boundary layer. It is found that (I) the Nusselt number at the rear stagnation point varies with the relative scale A / D, at the same Reynolds number, (2) the laminar-to-turbulence transition region in the separated shear layer moves in the streamwise direction with the change in the length-scale ratio, and (3) a streamwise shift of the transition region in the separated shear layer causes a substantial increase in the power spectrum of the temperature fluctuation. A correlation equation with A/ Das a parameter is derived to predict the heat transfer rate at the rear stagnation point. 相似文献
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In this work, we present a numerical study of the laminar-turbulence transition flow around a symmetrical air-foil at a low Reynolds number in free flow and near the ground surface at different angles of attack. Finite volume method is employed to solve the unsteady Reynolds-averaged Navier–Stokes (RANS) equation. In this way, the Transition SST turbulence model is used for modeling the flow turbulence. Flow around the symmetrical airfoil SD7003 is numerically simulated in free stream and near the ground surface. Our numerical method can detect different aspects of flow such as adverse pressure gradient, laminar separation bubble and laminar to turbulent transition onset and the numerical results are in good agreement with the experimental data. 相似文献
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Many complex fluid motions are driven by physical processes of instability, transition and turbulence dependent upon nonlinear mechanisms. Here, we solve the flow past cylinder(s) using single-block structured and overset grids by computing Navier–Stokes equation in two-dimensions. The suitability of a compact scheme in discretizing convection and diffusion terms are investigated first by looking at relevant numerical properties. Also, for the overset grid method, one of the methods is identified that shows the best results in minimizing interpolation error at sub-domain boundaries for an analytical test function. We provide extensive comparisons with experimental and other computational results for flow past a single cylinder, utilizing both single-block structured and Chimera or overset grids. Apart from showing instability of this flow calculated by these methods, we also compare the computed vorticity and velocity data using these two grids by employing the proper orthogonal decomposition (POD). We have analyzed and developed an overset grid method with compact scheme that does not need any filtering to control error. This has been ascertained by performing POD analysis. To show that the developed method is capable of handling complex geometries, we have computed flow past two cylinders in side-by-side arrangement. Results obtained capture the known flow characteristics for this arrangement well using relatively fewer number of grid points. 相似文献
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D. I. Okhotnikov V. M. Molochnikov A. B. Mazo A. V. Malyukov A. E. Goltsman I. I. Saushin 《Thermophysics and Aeromechanics》2017,24(6):873-882
Here we present the results of experimental investigation of a cross flow around a circular cylinder mounted near the wall of a channel with rectangular cross section. The experiments were carried out in the range of Reynolds numbers corresponding to the transition to turbulence in a wake of the cylinder. Flow visualization and SIV-measurements of instantaneous velocity fields were carried out. Evolution of the flow pattern behind the cylinder and formation of the regular vortex structures were analyzed. It is shown that in the case of flow around the cylinder, there is no spiral motion of fluid from the side walls of the channel towards its symmetry plane, typical of the flow around a spanwise rib located on the channel wall. The laminar-turbulent transition in the wake of the cylinder is caused by the shear layer instability. 相似文献
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