在泰勒-库埃特湍流中，使用疏水内筒实现气泡减阻

2019/12/31   下载量： 0 次

方案摘要

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应用领域 航空航天
检测样本 航天
检测项目
参考标准 暂无

采用LaVision公司由科研型CMOS相机和DaVis软件平台构成的粒子成像测速系统，对在泰勒-库埃特湍流中，使用疏水内筒实现气泡减阻的方法进行了实验测量研究。

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In this study we experimentally investigate bubbly drag reduction in a highly turbulent flow of water with dispersed air at 5:0  105 6 Re 6 1:7  106 over a non-wetting surface containing micro-scale roughness. To do so, the Taylor–Couette geometry is used, allowing for both accurate global drag and local flow measurements. The inner cylinder – coated with a rough, hydrophobic material – is rotating, whereas the smooth outer cylinder is kept stationary. The crucial control parameter is the air volume fraction present in the working fluid. For small volume fractions ( <4 %), we observe that the surface roughness from the coating increases the drag. For large volume fractions of air ( >4 %), the drag decreases compared to the case with both the inner and outer cylinders uncoated, i.e. smooth and hydrophilic, using the same volume fraction of air. This suggests that two competing mechanisms are at play: on
the one hand, the roughness invokes an extension of the log layer – resulting in an increase in drag – and, on the other hand, there is a drag-reducing mechanism of the hydrophobic surface interacting with the bubbly liquid. The balance between these two effects determines whether there is overall drag reduction or drag enhancement. For further increased bubble concentration D 6% we find a saturation of the drag reduction effect. Our study gives guidelines for industrial applications of bubbly drag reduction in hydrophobic wall-bounded turbulent flows.

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北京欧兰科技发展有限公司
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