平板表面薄圆柱绕流摩擦力矢量场全局测量

针对壁面摩擦力矢量场测量问题,基于剪切敏感液晶(SSLC)涂层技术建立了一种测量平板表面摩擦力矢量场的方法。该方法基于多视角测量原理,采用六台同步相机从不同方向同时采集SSLC涂层在摩擦力作用下的颜色变化,与采用单台相机相比能够降低测量噪声,并且具有测量非定常流动的摩擦力场的潜力。应用该方法测量了平板表面薄圆柱绕流的摩擦力矢量场,结果表明:(1)SSLC涂层能够以彩色方式定性显示壁面摩擦力信息;(2)通过对不同方向观测的SSLC涂层颜色进行分析处理,该方法能够高分辨率测量薄圆柱绕流的摩擦力矢量场,详细地捕获了流动特征;(3)同一份SSLC涂层可以重复使用并且可用于测量不同的摩擦力矢量场。

Global measurement of wall shear stress vector field over flat plate around thin cylinder

A method is developed for the measurement of wall shear stress vector fields over planar surface using the shear-sensitive liquid crystal(SSLC)coating technique.The method is based on a multiple-view method and uses six synchronized digital cameras to record the color change in the SSLC coating from different circumferential view angles,which therefore can reduce the noises when compared to the use of only a single camera and has the potential to measure instantaneous wall shear stress distribution in unsteady flow.The method is applied to the measurement of wall shear stress vector fields over flat plate around a thin cylinder to demonstrate its effectiveness.Experimental results show that:(1)The SSLC coating can qualitatively visualize wall shear stresses via color changes;(2)Wall shear vector field around the thin cylinder can be obtained in high resolution by analysing the coating color changes that are recorded from different circumferential view angles,and the flow structures around the thin cylinder are captured in detail;(3)A single SSLC coating can be used to measure wall shear stress vector fields under different flow conditions.