用大尺度层析PIV研究平移球体的空气动力学阻力

2018/12/07   下载量： 3 次

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应用领域 其他
检测样本 其他
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参考标准 暂无

采用创新性的大尺度层析测量系统。用三台相机进行记录。得到在一个方形空气风洞中直径0.1m圆球体，在以1.45m/s平动时周围空间的3D3C速度矢量场，并根据这一矢量场结果，分析计算圆球的空气动力学阻力。

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A method is introduced to measure the aerodynamic
drag of moving objects such as ground vehicles
or athletes in speed sports. Experiments are conducted
as proof-of-concept that yield the aerodynamic drag of
a sphere towed through a square duct in stagnant air. The
drag force is evaluated using large-scale tomographic PIV
and invoking the time-average momentum equation within
a control volume in a frame of reference moving with the
object. The sphere with 0.1 m diameter moves at a velocity
of 1.45 m/s, corresponding to a Reynolds number of
10,000. The measurements in the wake of the sphere are
conducted at a rate of 500 Hz within a thin volume of
approximately 3 × 40 × 40 cubic centimeters. Neutrally
buoyant helium-filled soap bubbles are used as flow tracers.
The terms composing the drag are related to the flow
momentum, the pressure and the velocity fluctuations and
they are separately evaluated. The momentum and pressure
terms dominate the momentum budget in the near wake
up to 1.3 diameters downstream of the model. The pressure
term decays rapidly and vanishes within 5 diameters.
The term due to velocity fluctuations contributes up to
10% to the drag. The measurements yield a relatively constant
value of the drag coefficient starting from 2 diameters
downstream of the sphere. At 7 diameters the measurement
interval terminates due to the finite length of the duct. Error
sources that need to be accounted for are the sphere support

wake and blockage effects. The above findings can provide
practical criteria for the drag evaluation of generic bluff
objects with this measurement technique.

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北京欧兰科技发展有限公司
金牌会员 丨 第17年
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