流动显示中的圆管畸变及其校正

对玻璃圆管内的流场进行显示时,沿管径方向的光线成像存在畸变,使得圆管内流场显示的有效范围减小,必须进行校正才能得到圆管内流场更大的有效视场。通常采用和管壁焦距相反的柱透镜来校正管壁畸变。校正柱透镜的设计是关键,首先采用厚透镜焦距计算方法得到单侧管壁的等效焦距,校正柱透镜焦距与其值相同,符号相反。如果采用传统的平凸柱镜,进行光线追踪时效果并不理想。重新在ZEMAX光学软件中优化校正柱透镜的曲面参数和与圆管的距离,得到的结果为弯月校正柱透镜。按照参数加工圆管和校正柱透镜,采用栅格对其进行静态验证,证明了该方法的有效性,将有效视场增大到了大于80%,相比传统的外加平凸透镜方法,该方法得到的弯月柱透镜校正更加准确,并通过高速聚焦纹影给出了动态结果。该工作对于厚壁圆管内的流场显示等相关工作具有参考意义。

Aberrance and rectification of a round pipe for flow field visualization

When the flow field in a circular-section pipe is visualized,there exists optical aber-ration along the radii of the pipe,which makes the effective range of flow field smaller.The aber-ration must be calibrated in order to get a bigger view.Commonly a cylindrical len with reverse foci to that of the pipe wall is used to calibrate the distortion.Therefore the design of the calibra-tion cylinder lens is the key.Firstly we calculate the foci of the half-wall of the circular-section pipe,and the other side of the pipe is the same as this side.Then the foci of the calibration cylin-der len is obtained.It is found that the calibration effect of a cylinder len with the traditional pla-no-convex cross section can not meet the requirement.So the foci of the len is recalculated in ZE-MAX software by fixing the distance between the pipe and the len,and then adjusting the two curvatures of len until the output rays are almost parallel in 80% range.The result shows that the optimal cross section takes the form of positive meniscus.After that,we manufactured two glass pipes and two pieces of calibration cylinder lens.Then the result of static state demarcation by grid imaging proves the validity of this method.Compared to the traditional method,this method is more accurate and extends the effective flow field range to more than 80%.Dynamic result is given by the high speed focusing schlieren way.This research has reference signification for flow field visualization in round pipes with a thick wall.