受我校国际合作与交流基金聘请项目的资助，土木工程学院陈文礼教授邀请美国莱特州立大学(Wright State University)的Yang Zifeng副教授于2017年5月20-27日期间访问我校，并进行学术交流。Yang Zifeng教授研究兴趣和方向广泛，分别在先进流体测量技术、生物流体测量、血液动力学、汽轮机叶片液膜冷却、风力机流动测量技术以及微型飞行器等方面领域都开展了研究工作，并取得很好的研究成果。
Yang Zifeng教授的系列学术报告的具体信息如下，欢迎相关专业广大师生参加。
报告一
报告时间和地点：5月22日（星期一），10:00—12:00，土木工程学院502室
报告题目：Hybrid Particle Image Velocimetry with the Combination of Cross-correlation and Optical Flow Method
主要内容：Through a combination of two methods, the cross-correlation and optical flow method, a novel technique can benefit from the strengths of each method while concealing the flaws each individual method contains. The Hybrid Particle Image Velocimetry (PIV) method utilizes the state-of-the-art cross-correlation method suitablefor large displacements, the optical flow method is restricted to images with small displacements. Combining the two methods requires the constraints set forth on the optical flow method to be conserved. Thus techniques such as interpolation, image shifting, and Gaussian filtering are crucial for transitioning cross-correlation results to optical flow analysis. Towards validating the accuracy of the hybrid PIV method, standard PIV images encompassed various parameters were utilized to conduct the validation study. Each set of images were analyzed by the hybrid method and three other widely-used correlation techniques in order to compare the hybrid method’s accuracy with traditional correlation-based methods.
报告二
报告时间和地点：5月23日（星期二），10:00—12:00，土木工程学院502室
报告题目：Experimental Investigations on the Passive Control of Wind Turbine Wakes
主要内容：Wind Turbine dynamics, wake effects and environmental impacts have been identified as the most significant research topics needed for wind power generation. Tip vortices and turbulence generated by the sweeping blade are the substantial source for the turbulent wake flow as well as the aerodynamic noise emission from wind turbine. Experimental studies are conducted to characterize the evolution of the tip vortices downstream a well-designed horizontal axis wind turbine model. The effect of the alteration of tip design were investigated to identify the effective passive control of the generation of tip vortices. On the other hand, owl-wing-like materials were utilized to create a trailing edge fringe to regulate the turbulent wake from the blade. It was found in the experimental study that the existence of the flexible trailing edge fringe can help break the large-scale swirls into small-scale weak swirls for relatively large angle of attack, while the motion of the fringe might induce additional Reynolds stress at lower angle of attack.
报告三
报告时间和地点：5月24日（星期三），10:00—12:00，土木工程学院502室
报告题目：Hemodynamics in the Intracranial Vascular System: Numerical Solution and Experimental Examination
主要内容：Hemodynamics plays a key role in may vascular diseases, such as atherosclerosis, and intracranial aneurysm. Unnormal Wall Shear Stress (WSS) has been identified as the most important trigger for vessel wall degeneration.Detailed blood velocity information in vascular system can be obtained both computationally and experimentally.On one hand, a numerical simulation using a patient-specific vascular model was conducted to present the details of the blood flow inside an aneurysm. On the other hand, an experimental examination was conducted by applying the optical flow method (OFM) in processing fluoroscopic digital subtracted catheter angiographic images, however, there are still challenges with the accuracy of this method. In the present study, a divergence compensatory Optical Flow Method (DC-OFM), in which a non-zero divergence of velocity is assumed due to the finite resolution of the image, was explored and applied to the digital subtraction angiography (DSA) images of blood flow. The objective of this study is to examine the applicability and evaluate the accuracy of DC-OFM in assessing the blood flow velocity in vessels. Validation studies were conducted by using standard particle images and DSA images. In comparison with the traditional OFM, the present method can provide more accurate velocity estimation. The accuracy of the velocity estimation can also be improved by implementing pre-process techniques including image intensification, Gaussian filtering and “image -shift”.
主讲人简介：
Dr. Zifeng Yang is an associate professor in the Department of Mechanical and Materials Engineering at Wright State University since 2011. His research interests include development of advanced fluid diagnostic techniques, biological fluid measurements, hemodynamics, film cooling for gas turbine blade,wind turbine technology and Micro Air Vehicles. Dr. Yang has published 20 peer-reviewed journal papers and 20 conference papers. He is an AIAA Applied Aerodynamics Technical Committee member, member of American Heart Association, member of American Physical Society (APS) and associated editor of Journal of Coastal Life Medicine.
