Research
My research concerns the experimental investigation of fluid flows using advanced imaging and flow sensing techniques. I seek to visualize interesting flow phenomena that have been traditionally under-served for reasons such as difficulty of visualization, lack of imaging techniques, or neglect. An experimental understanding of complex fluid flows and flow turbulence is critical for modeling and engineering design of fluid systems. From naval applications to alternative wind and ocean energy systems, a deeper understanding of fluid physics across a wide range of scales can be obtained through advanced imaging and optical flow measurement techniques. Advancing traditional flow visualization methods such as Laser Induced Fluorescence (LIF), Particle Image Velocimetry (PIV), and holographic imaging, my research delves into state of the art imaging systems and image processing techniques to reveal new and exciting fluid phenomena.
I am also interested in the application of new and interesting phenomena. Whether it is the use of hydrophobic and hydrophilic surfaces to increase the efficiency of steam turbines or biologically inspired locomotion my research lies at the intersection of discovery and application. Typically, and experiment involves the use of advanced imaging technologies (e.g. extremely high speed cameras) and image processing techniques (e.g. masking, PIV, object trajectory and force analysis) to discover the why and how of the observed phenomenon. Then an application is typically discovered and explored in order to demonstrate its application further experimentation is often required.
This part of my thesis focuses on the water entry of spheres entering the water normal to the free surface but with increasing spin rates and differing surface treatments. Although this problem is often thought of as a canonical problem, and a standard drawing of it used in almost all theoretical fluid dynamics textbooks, a few things make this problem unique and difficult to solve theoretically. The free surface imparts forces on the sphere and resulting cavity, which are not well understood. Furthermore, the application of different surface treatments can greatly affect the static wetting angle as well as roughness, which can dramatically affect the cavity formation. A large experimental data set of high-speed images was used to analyze these impacts and determine the forces at play, and the relatively physics governing this beautiful phenomenon. This thesis shows the affect of wetting angle, roughness, and spin rates on the cavity formation and splash curtain growth for impacts of this nature and estimates the forces at play through image processing techniques and particle image velocimetry (PIV).
This study is motivated by the navy’s desire to shoot incoming underwater threats (i.e. supercavitating torpedoes) from the deck of a surface vessel. These bullets must travel at extremely high speeds and enter the water at shallow angles, a feat once believed impossible. Since high-speed flows can change the state of an incompressible fluid so that the fluid becomes a supersaturated gas, underwater bullet travel becomes plausible. Also known as supercavitiation, this phenomenon has been studied for many decades, but only recently was it applied to surface piercing projectiles. Experiments were done to determine better boundary conditions and parameter shapes for use in theoretical models. The experiments were carried out in both a laboratory setting at MIT. These tests revealed that impacts of this type can indeed create a viable medium for water entry if the bullet shape and speed are correctly matched.
