共查询到18条相似文献，搜索用时 93 毫秒
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横向受迫振荡圆柱低雷诺数绕流问题数值模拟 总被引：2，自引：1，他引：1
对雷诺数Re=200的圆柱在均匀来流中横向受迫振荡的问题进行数值模拟分析.通过改变运动圆柱的振荡频率和振幅,分析圆柱所受作用力及圆柱尾流泻涡结构的变化特性,振荡圆柱在非锁定状态和锁定状态下作用力曲线和圆柱尾流泻涡结构的变化情况,以及不同圆柱振荡频率和振幅情况下单个振荡周期内圆柱尾流泻涡结构模式之间的转换特征. 相似文献
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基于Fluent流体计算平台,运用大涡模拟方法对亚临界雷诺数Re=3900下“X”形排列五圆柱体结构群三维绕流特性进行研究,主要分析来流攻角α与间距比L/D两个关键参数对五圆柱体结构群的尾流区三维涡结构演化与流体力系数的影响,并揭示其内在流动互扰机理。研究表明:来流攻角和间距比的变化对五圆柱体结构群流动控制及互扰效应的影响显著。在小间距比工况下,观察到柱体群间隙区域内流体高速流动的现象,导致五圆柱体之间的互扰作用十分强烈。间隙流对中间圆柱体和下游圆柱体有较强的冲击作用,对其表面的流体力分布特性有显著的影响。另外,大间距比工况下,当α=0°与L/D≥5.0工况时,柱体群尾流效应强于其间隙流效应。当α=22.5°与L/D=7.0时,位于下游与中间处的圆柱体流体绕流特性存在较大差异。而当α=45°与L/D≥6.0时,位于上游与中间处的圆柱体尾流区均会产生正负交替的漩涡结构。 相似文献
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采用理论研究和试验研究相结合的方法,对两层流体中内孤立波对不同水深竖直圆柱体水平作用力进行了分析。采用重力塌陷法进行内孤立波造波试验,通过PIV(Particle Image Velocimetry)技术获取内孤立波波剖面的时间序列,利用测力系统对竖直圆柱体在内孤立波作用下的受力进行测量。通过内孤立波波剖面试验分析,选取合适的内孤立波理论并对竖直圆柱体所受内孤立波作用力进行计算,将计算结果与试验结果进行汇总分析。结果表明:上层流体中圆柱体所受内孤立波最大水平作用力明显大于下层流体中各段圆柱体,且方向相反;随着内孤立波振幅的增大,各段圆柱体所受内孤立波最大水平作用力也相应地增大;密度跃层处圆柱体所受水平作用力具有相较于其他位置处更为复杂的变化趋势;选用合适的内孤立波理论进行计算能够较好的模拟竖直圆柱体的实际水平受力。 相似文献
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《中国海洋大学学报(自然科学版)》2015,(6)
在内波以及其他的层结流体的实验中首先需要制备密度层结的流体,传统的双缸法只能制备密度均匀分层的层结流体。本文对传统的制备均匀层结盐水的双缸法进行改进,推导了制备任意密度剖面的层结盐水方法的理论公式以及实用数值计算方法,通过振荡圆柱实验对此方法的可行性进行了验证。 相似文献
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内孤立波对海洋平台的安全运行存在一定的威胁,基于三维数值水槽对内孤立波传播引起的半潜平台受力及其周围流场的分布进行了数值模拟研究.通过与试验对比,分析了入射波幅和分层流体深度比对半潜平台上内孤立波荷载特性的影响规律,验证了数值模拟结果是准确可靠的.研究表明,内孤立波引起的平台荷载会随着内孤立波波幅的增加而增大,随着分层流体深度比的增加而减小.基于对平台周围剖面速度场和三维涡场的演化规律研究,发现在内孤立波传播过程中,平台周围会出现明显的速度减小区,平台周围会有大量的漩涡产生并发生脱落现象. 相似文献
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基于光滑粒子流体动力学(SPH)方法,开发了能够准确描述水流作用下圆柱强迫振动特性的数学模型。通过引入适合于无网格粒子法的开边界算法,来模拟出入流边界条件,建立了具有造流功能的SPH数值水槽。圆柱及计算域的上下边界均采用修正的动力边界条件进行模拟。借助于粒子位移矫正和压力修正算法,避免了圆柱周围流体粒子压力大幅震荡以及结构下游区域出现空腔等非物理性现象。使用典型的圆柱绕流数据,验证了所建SPH模型的计算性能,研究了固定圆柱在低雷诺数情况下的尾涡脱落模式和升阻力变化规律。明确了低雷诺数下强迫振动圆柱在频率锁定以及非锁定区间内的升力变化规律,量化了升力与外界激励频率之间的关系。 相似文献
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基于计算流体力学(CFD)开源代码OpenFOAM开展了不同雷诺数(Re=100、1500和3900)和倾斜角度(-60°≤α≤60°)工况下倾斜圆柱绕流流场的三维数值模拟,研究倾斜圆柱绕流的三维瞬时及时均尾流流场、流线拓扑、升阻力系数与旋涡脱落频率随雷诺数及倾斜角度变化的规律,探讨在顺流向及逆流向情况下独立性原则对倾斜圆柱绕流的适用性。研究结果表明:随着圆柱倾角的增大,倾斜圆柱尾流产生较为明显的轴向流,尾流旋涡脱落受到明显抑制,细碎旋涡逐渐消失,尾流宽度随之减小;随着雷诺数的增大,圆柱尾流涡管发生明显的变形,展向掺混使得大量细碎旋涡产生,呈现出明显的三维特性。在不同雷诺数下,阻力系数均值、升力系数均方根及无量纲涡脱频率在一定倾角范围内符合独立性原则。 相似文献
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利用计算流体力学软件Fluent开展了三维动波浪壁圆柱绕流的数值模拟,建立了三维运动波浪壁圆柱模型,通过C语言自编程序实现波浪壁面的运动控制,并保证壁面变形时网格的高质量。在来流速度u=0.125 m/s、雷诺数Re=12 500的情况下,开展了动波浪壁波动速度w=0、0.062 5、0.125、0.187 5 m/s四个工况的计算分析,并比较了不同波动速度对流场结构、升力、阻力特性的影响。结果表明:动波浪壁圆柱能有效抑制流动的分离,消除交替脱落的尾涡,从而消除周期振荡的升力;在消除卡门涡街的同时,圆柱后驻点处的涡量值随波动速度增加而增加,其原因在于波形移动加大了壁面流体的速度,从而减小了圆柱前后的压力差,减小了阻力;随着波动速度的增大,平均阻力系数呈明显下降趋势,当波动速度为来流速度的1.5倍时,平均阻力系数相对于光滑圆柱下降了53.76%。 相似文献
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A flow past a circular-section cylinder with a perforated conic shroud, in which the perforation is located at the peak of the conic disturbance as the shroud installed on the cylinder and uniformly distributed with several circular holes, is numerically simulated at a Reynolds number of 100. Two factors in the perforation are taken into account, i.e. the attack angle relative to the direction of incoming flow and diameter of holes. The effect of such perforation on the drag, lift and vortex-shedding frequency is mainly investigated. Results have shown that variation of the attack angle has a little effect, especially on the drag and vortex-shedding frequency, except in certain cases due to the varied vortex-shedding patterns in the near wake. The increasing hole diameter still exhibits a little effect on the drag and frequency of vortex shedding, but really reduces the lift, in particular at larger wavelength, such as the lift reduction reaching almost 66%–68% after introducing the perforation. 相似文献
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The fluid force coefficients on a transversely oscillating cylinder are calculated by applying two-dimensional large eddy simulation method. Considering the “jump” phenomenon of the amplitude of lift coefficient is harmful to the security of the submarine slender structures, the characteristics of this “jump” are dissertated concretely. By comparing with experiment results, we establish a numerical model for predicting the jump of lift force on an oscillating cylinder, providing consultation for revising the hydrodynamic parameters and checking the fatigue life scale design of submarine slender cylindrical structures. 相似文献
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W. Koterayama 《Ocean Engineering》1980,7(3):399-412
This paper presents a method of estimating wave forces acting on a submerged horizontal circular cylinder fixed in oblique waves.The experiments show that drag and inertia coefficients in beam sea are available for calculating the wave forces in oblique waves.Wave forces exerted on a vertical circular cylinder in deep waves are also investigated.The experimental results show that wave forces acting on the vertical cylinder coincide approximately with hydrodynamic forces acting on a submerged circular cylinder in an oscillating fluid. 相似文献
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A flow past a circular-section cylinder with a perforated conic shroud, in which the perforation is located at the peak of the conic disturbance as the shroud installed on the cylinder and uniformly distributed with several circular holes, is numerically simulated at a Reynolds number of 100. Two factors in the perforation are taken into account, i.e. the attack angle relative to the direction of incoming flow and diameter of holes. The effect of such perforation on the drag, lift and vortex-shedding frequency is mainly investigated. Results have shown that variation of the attack angle has a little effect, especially on the drag and vortex-shedding frequency, except in certain cases due to the varied vortex-shedding patterns in the near wake. The increasing hole diameter still exhibits a little effect on the drag and frequency of vortex shedding, but really reduces the lift, in particular at larger wavelength, such as the lift reduction reaching almost 66%–68% after introducing the perforation. 相似文献
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The unsteady flow past a circular cylinder which starts translating and transversely oscillating from rest in a viscous fluid is investigated at a Reynolds numbers of R=103 and at a Strouhal number of π/4 and for the maximum oscillatory to translational velocity ratios between 0.1 and 1.0. This study is based on numerical solutions of the two-dimensional unsteady Navier–Stokes equations. The object of the study is to examine the effect of increase of velocity ratio on the near-wake structure as well as the hydrodynamic forces acting on the cylinder. For all velocity rates a periodic structure of vortex evaluation and shedding develops which is repeated exactly as time advances. Vortex dynamics close behind the body are affected by changing acceleration of the cylinder and a changeover from one mode to a different mode of vortex formation is observed with increase in velocity ratio. A comparison of the present results with the impulsively started translating case has been included to illustrate the effect of velocity ratio on drag at small values of velocity ratio. 相似文献