共查询到19条相似文献,搜索用时 140 毫秒
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[目的]为探讨近壁旋转圆柱尾流及流体力特性,对典型间隙比下旋转圆柱绕流进行研究。[方法]对雷诺数Re=200下3种典型间隙比(G/D=0.2,0.8,1.4)的旋转圆柱绕流展开数值模拟,对比不同间隙比和转速比下的圆柱尾流及流体力特性。[结果]结果显示:当G/D=0.2时,圆柱表面脱涡会受到显著抑制,圆柱表面升阻力无波动;当G/D=0.8和1.4且转速比较低时,会发生“尾流涡”脱落现象,其结构与2S模式相似,升阻力系数呈正弦周期性波动,振幅较小;当正旋转速较大时,圆柱表面无漩涡脱落,形成稳定的D模式尾流(随转速比增大由D+模式变为D-模式),“尾流涡层”与“壁面涡层”发生分离,“壁面涡”呈现多周期性脱落现象,升阻力系数呈多周期波动,振幅显著增大;当反旋转速较大时,圆柱表面被一层正涡量的涡层包裹,漩涡脱落受到显著抑制,升阻力无波动。[结论]所得结论可为高效流动控制技术发展提供参考。 相似文献
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王成彦巫凯旋陈沛楷黄技 《船舶与海洋工程》2023,(2):7-13
为研究不同来流角度下方形排列四圆柱的水动力特性,利用Fluent软件模拟雷诺数为3 900、来流角度不同时,临界间距比为2.0和3.5情况下的四圆柱互扰效应。通过数值模拟,重点分析来流角度发生变化引起的下游圆柱升阻力系数和尾流模态的改变,比较其在这个临界间距比下呈现出的不同特征。研究结果表明:随着来流角度的增大,在2种临界间距比下同号圆柱呈现出的阻力系数变化趋势的特点相似;2种间距比下圆柱的升力系数均表现出由离散到收敛的趋势,但具体特点有所差异;斯特鲁哈数在2种间距比下的特点存在明显不同。研究成果可供海上钻井平台等海洋结构物设计参考。 相似文献
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文中用数值方法研究了圆柱在流体中的强迫振动对其流场特性及受力的影响。主要包括圆柱振动频率对圆柱尾涡形态及升阻力系数的影响,振动频率比e sf f的范围取为0.8~3.0,ef为圆柱振动频率、sf为静止圆柱涡脱落频率。文中采用的数值方法是Lattice Boltzmann Method(LBM),它具有并行效率高,边界处理简单的特点。本文比较并讨论了LBM中几种边界条件的处理方法,并提出一种能对移动边界进行更容易处理的新方法。模拟的结果与参考文献进行了比较,结果表明,用此方法处理移动边界是可行的。 相似文献
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风力转子推进装置节能环保,降低推力成本,有利于船舶行业的绿色发展。基于多松弛格子Boltzmann方法,对并列风力助推转子绕流进行数值模拟。首先模拟单圆柱绕流的流动特性,以验证程序的可靠性,重点探究双圆柱的间距比和转速比对圆柱绕流特性的影响。获取圆柱的升阻力系数以及尾流流型,验证临界转速比的存在。结果显示:旋转可以有效地抑制涡的生成和脱落,当转速比达到临界转速比时,漩涡彻底消失,流场变得稳定;时均升力系数的绝对值和时均阻力系数随转速比的增大分别增大和减小。 相似文献
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在圆柱表面布置不同深度的V形沟槽,采用k-ω/SST湍流模型进行数值计算,研究其减阻效果,分析圆柱表面的升力系数、阻力系数、速度分布及尾流漩涡脱落状态.结果 表明,与光滑圆柱表面相比,V形沟槽深度为0.04D的减阻效果最好,阻力系数相对于光滑圆柱表面减小了34.4%.当沟槽深度为0.04D时,升力系数的均方差最小,相对于光滑圆柱表面减小了16%;随着沟槽深的增加,St先增大后减小,当沟槽深为0.04D或0.05D时,漩涡脱落频率发生明显变化;当沟槽深度为0.04D时,圆柱前后速度差最小.随着槽深的增加,尾流漩涡表现出强度减小数量增多的趋势,当槽深为0.05D时,漩涡脱落呈双稳态. 相似文献
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The vortex-induced vibrations (VIV) of two flexible circular cylinders in a tandem configuration were studied numerically for spacing ratios ranging from 6 to 18 and the reduced velocities ranging from 2.35 to 12.59. The VIV response amplitude, response frequency, fluid force, pressure distribution and vortex structure of the tandem cylinders with different spacing ratios under different reduced velocities were compared. The results indicate that there is a great difference between the lift forces on the downstream and upstream cylinders. The lift coefficient of the downstream cylinder undergoing the wake-induced vibrations (WIV) is larger than that of the upstream cylinder, and the dominant frequency curves of the lift coefficients of the upstream and downstream cylinders separate. It can be found that the length and intensity of the wake are quite different under different reduced velocities and spacing ratios, and the reattachment positions between the wake and the downstream cylinder are different, which leads to a great change in the flow around the downstream cylinder and have a great effect on the wake-induced lift force on the downstream cylinder. Considering these factors, an empirical model for the wake-induced lift force on a cylinder with low mass ratio was proposed and verified. 相似文献
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针对串联双圆柱的结构特点,利用IVCBC涡方法适合高雷诺数下数值计算的特点,建立了高雷诺数下串联双圆柱绕流的数值计算模型;采用经典算例验证了IVCBC涡方法的收敛性;探索了雷诺数为2.5×104、间隙比分别为1.1,1.25,2,2.5,3,3.25和4的串联双圆柱绕流的尾流特征;清晰地展示了尾流中较小的漩涡的形成、分裂和融合,详细地阐述了串联双圆柱流体特征发生突变的原因;深刻地揭示了串联双圆在高雷诺数下的绕流机理。研究表明:尾流模式与经典的实验尾流模型吻合较好,两圆柱中间的涡对是串联双圆尾流发生突变的主要原因;间隙之间时,间隙上部小漩涡形成、间隙中间流体的振动与下游圆柱表面上涡的脱落是同步的;该流体模式能清晰地展示尾流中较小漩涡,说明与有网格方法比较,该计算模型具有较大的优越性,为进一步研究高雷诺数下串联双圆柱流体力的特征提供了重要的研究工具。 相似文献
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Multiple side-by-side cylinders are widely employed in many engineering applications. Consequently, flow-induced vibrations (FIV), which have a significant influence on structural reliability, have drawn considerable concern from many investigators. Due to the complicated wake interactions behind the cylinders, the hydrodynamic characteristics of multiple side-by-side cylinders subject to FIV are obviously different from those of a single cylinder. Hydrodynamic force coefficients play an important role in evaluating structural reliability and predicting fatigue damage. However, few relevant investigations have been performed on hydrodynamic force coefficients of multiple side-by-side flexible cylinders, which require further research. In this paper, the hydrodynamic force coefficients of three and four side-by-side flexible cylinders with a spacing ratio of 6.0 are obtained by an inverse analysis method based on the oscillation displacements. In the resonance regions, the hydrodynamic force coefficients of multiple cylinders exhibit variation trends similar to those of a single cylinder, especially at higher reduced velocities. In the mode switch regions, relatively large deviations exist between the coefficients of multiple cylinders and single cylinder. The inner cylinder in the three-cylinder system shows prominently distinctive behaviour compared with the outer two cylinders. For the four-cylinder system in a side-by-side arrangement, the outer two cylinders show relatively slight differences between each other compared with the inner two cylinders. 相似文献
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海上平台是开采海洋资源的关键建筑,而支撑柱在平台中起着至关重要的作用。本文建立在海水作用下支撑柱做单圆柱绕流、串列双圆柱绕流和并列双圆柱绕流的二维流场模型,运用大涡模拟方法,对这3种模型进行数值模拟,得出其瞬时流场速度云图和圆柱受力特性曲线图。模拟计算层流和湍流情况下的圆柱绕流,通过模拟结果分析流场、升力系数和阻力系数的变化规律。 相似文献
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本文通过控制变量法进行工况设计,对多孔管进行数值模拟和试验对比,分别研究多孔管管径、管长、孔径、孔间距、水压五个变量对多孔管孔出流速及流量的影响。使用ANSYS软件中的DesignModeler模块进行几何建模,ICEM中的O-Block技术进行流体计算域网格划分,Fluent软件进行求解。研究发现,多孔管管内径和管长的增加均使孔出流速和出流量减小,管长度的增加会影响孔出流沿程的均匀性;孔径的增大使孔出流速明显减小,且影响孔出流沿程的均匀分布,出流量受孔径的影响较复杂,在孔径不超过2.5mm时可以认为出流量与孔径的平方成正比;孔间距的增大对孔出流速和沿程均匀分布基本无影响,而与出流量成正比。最后将数值模拟结果和试验进行对比,发现试验数据所反映的多孔管出流量与管内径、管长、孔径和孔间距的关系与数值模拟基本吻合,而试验中管的出流量普遍比数值模拟小。 相似文献
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