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非淹没丁坝绕流的三维大涡模拟研究

STUDY OF NON-SUBMERGED GROIN TURBULENCE FLOW IN A SHALLOW OPEN CHANNEL BYLES

  • 摘要: 采用动态亚格子模式和浸没边界法,对宽浅槽道中的丁坝群绕流的水动力学特性进行了三维大涡模拟研究. 利用丁坝绕流,试验中采用粒子图像测速仪(particle image velocimetry, PIV)测量的试验中自由水面处的时间平均流速和湍动强度数据对模型进行率定,结果表明计算结果与试验数据吻合良好. 丁坝长度与丁坝之间距离的比值L/D对丁坝周围的水流流动形式、湍流强度、涡量分布有显著影响. 在L保持不变并且L/D较大时,丁坝之间的距离D较小,这限制了混合层的发展,因此混合层中的湍动强度和涡量都较小;同时丁坝之间的回流区的流线形式也发生明显变化. 此外,还给出了涡体在丁坝坝头附近产生,发展并向下游输运的动态过程.

     

    Abstract: Turbulent flow past series of groins in a shallow open channel is studied by large eddy simulation (LES) in this paper. A direct-forcing immersed boundary method is proposed to approximate complex boundaries around groins with round heads. Time-averaged velocity and turbulence intensities at the water surface obtained by a PIV experiment are used to validate the LES model, and the numerical results from LES agree well with the PIV measurements. Moreover a comparing case for groin flow is set up to investigate the effect of the groin aspect ratio L/D on flow characteristics, involving flow patterns, turbulent intensities, vorticity distribution and vortex dynamics. The distance D between two groins is smaller when the groin aspect ratio L/D is bigger and L is constsant. And this a ects the strength of turbulence intensities and vorticity in the mixing layer and flow patterns in the groin field. After producing around the groin heads, the shape of the vortex group varies as the vortices being transported downstream by the flow.

     

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