摘要
流场显示及测量技术是研究流体力学的关键技术手段,目前大多数测量方法需要结合多视角层析的形式来实现三维测量。本文介绍了一种基于数字化重建图像方法的全息聚焦纹影技术,利用数字全息技术记录聚焦纹影成像系统中的波前信息,根据标量衍射理论重建不同光轴位置的聚焦纹影图像,实现三维流场的可视化与测量。基于前期发展的全息聚焦纹影技术,通过不同离焦距离下的平行双射流和单射流成像实验,定量分析了该技术的三维流场成像质量。对分别离焦30和60 mm的平行双射流进行测量,由1张全息图同时获得2个射流的聚焦纹影图像,重建得到的聚焦纹影图像与相应位置同一瞬态流场下的传统聚焦纹影图像效果一致,且不需要移动成像面,验证了全息聚焦纹影技术的三维测量能力。以离焦距离量化该技术的成像能力,在0~120 mm离焦距离范围内对不同离焦位置的单射流进行测量,重建图像中流场轮廓清晰,且与相同瞬态流场下的传统聚焦纹影图像中流场流动细节一致,进一步验证了全息聚焦纹影技术还原三维流场信息的准确性。本文研究的全息聚焦纹影技术具备单视角、单图像下的三维流场测量能力,突破了传统聚焦纹影技术单次单截面成像的限制,具备瞬态三维流场测量能力。
Flow field display and measurement technology is the key technology in the study of fluid mechanics.Now most of the methods need to combine multi-view recording or tomography to realize three-dimensional measurement.This paper introduced the holographic focusing schlieren technique based on digital image reconstruction method.This technique uses digital holographic technology to record the wavefront in the focusing schlieren imaging system,and uses the scalar diffraction theory to reconstruct the focusing schlieren images of different positions in the measurement area.This realizes the display and measurement of the three-dimensional flow field structure.Based on the pre-developed holographic focusing schlieren technique,this paper provides a quantitative analysis of the three-dimensional flow field imaging quality by holographic focusing schlieren.The parallel double jets and single jet imaging experiments with different defocusing degrees were carried out.Firstly,parallel double jets 30 mm and 60 mm out of focus were measured,and a single hologram was used to obtain the focusing schlieren of the two jets at the same time.The reconstruction of focusing schlieren images has the same imaging effect as the conventional focusing schlieren images with the same first class field transient at the corresponding position,and the imaging plane did not need to be moved.The three-dimensional measurement capability of holographic focusing schlieren technique is verified.Secondly,the imaging capability of this technique is quantified by defocusing distance,and single jets at different positions are measured within the range of 0–120 mm defocusing distance.The flow field outline in the reconstruction image was clear,and the details of the flow field were consistent with those in the traditional focusing schlieren image with the same transient field.The result further verifies the accuracy of 3D flow field information restoration by holographic focusing schlieren technique.The holographic focusing schlieren technique has the ability to measure three-dimensional flow field in a single view and single image,breaking through the limitation of the conventional focusing schlieren single section imaging,and has the ability to measure transient three-dimensional flow field.
作者
李奕勤
林志明
刘锴慧
薛志亮
金其文
吴迎春
吴学成
LI Yiqin;LIN Zhiming;LIU Kaihui;XUE Zhiliang;JIN Qiwen;WU Yingchun;WU Xuecheng(State Key Laboratory of Clean Energy Utilization,Zhejiang University,Hangzhou 310027,China;Qingshanhu Energy Research Center,Zhejiang University,Hangzhou 311300,China)
出处
《实验流体力学》
北大核心
2025年第4期9-18,共10页
Journal of Experiments in Fluid Mechanics
基金
国家自然科学基金青年科学基金项目(52406209)
浙江省自然科学基金资助项目(LZ24E06001)。
关键词
全息
聚焦纹影
三维测量
流场结构
holography
focusing schlieren
three-dimensional measurement
the structure of flow field
作者简介
李奕勤(2000-),女,浙江湖州人,硕士研究生。研究方向:数字全息技术,三维流场测量技术。E-mail:22227077@zju.edu.cn;通信作者:吴学成,E-mail:wuxch@zju.edu.cn。
