Application of Computer Vision to Transport Phenomena

Doctor of Philosophy, Graduate Program in Mechanical Engineering
University of California, Riverside, June 2019
Dr. Marko Princevac,, Chairperson

From the large scale atmospheric turbulent motion to blood flow in microvessels, our daily lives are dependent on various scales and modes of transport phenomena. Different techniques exist that helps us to study and understand these complex phenomena experimentally. Flow visualization is one of the most used methods that provide a good qualitative understanding of complex fluid behavior. By definition, flow visualization is the process of making the physics of fluid flows visible. With the development of digital and computational imagery, flow visualization has transitioned from being a qualitative measure to a quantitative measure of transport phenomena. In this research, we have incorporated computational imagery techniques to delineate different scales of transport phenomena such as the flow of convective hot air around a flame and the blood flow inside a mouse’s brain. The visualization was done by generating granular patterns of dark and bright spots and imposing it on the flow field. For the fire experiments, the granular pattern was created by illuminating a printed noise pattern using white non-coherent light. The hot air around the flame caused fluctuations in air density affecting the air’s refractive index; leading to distortion of the background image. By comparing distorted and undistorted images using optical flow algorithms, the flow field was visualized. A similar pipeline can be deployed to visualize the flow inside a mouse’s brain. Instead of using noncoherent light, the granular pattern was generated by using a laser beam. This granular pattern, produced by random interference effects in laser light, is commonly referred to as laser speckle pattern. When the speckle pattern is generated on blood vessels, the flow of blood causes fluctuations in this pattern leading to a blurriness associated with the blood vessel. This blurriness is later processed using computer algorithms which can be correlated to the motion of the red blood cells. This presentation will describe the pipeline for creating flow visualization of these multi scale transport phenomena .