Below are recent Summer Undergraduate Research Program (SURP) projects completed by students studying Mechanical Engineering.
Measuring the Temperature Field of an Optical Thermocavitation Bubble Using Planar-Laser Induced Fluorescence
Vicente Robles Jr. ’16; Mentor: Guillermo Aguillar (UC Riverside); Collaborators: Ismael Martinez (UC Riverside), Darren Banks (UC Riverside)
In recent years, cavitation has developed from an undesirable, damaging phenomenon towards one with applications in the biomedical and fluid control fields. Optical thermocavitation is a process in which a laser is focused into an absorptive liquid, causing it to superheat. This leads to the creation, growth and collapse of a vapor bubble. Applications such as Laser-Assisted Surface Cooling Enhancement and Skin Poration by Optical Cavitation are being developed in Dr. Aguilar’s laboratory. The former seeks to achieve cooling through natural convection and induced mixing while the latter is a drug delivery method that works by puncturing the outer layer of skin. To explore the dynamics of bubble formation and its effects on surroundings, a technique is being developed to measure the temperature field around a cavitation bubble. The non-intrusive technique is called Planar Laser-Induced Fluorescence. It uses Rhodamine-B in an aqueous copper nitrate (CuNO4, 24% by mass in water) solution. Rhodamine-B fluoresces when exposed to a 440 nm wavelength laser. We developed a calibration curve relating the measured intensity with temperature. First, the fluorescence intensity was measured against temperature in increments of 10℃ from 25℃ to 75℃, and a linear relationship was found. The fluorescent intensity decreases by approximately 10% for each interval. Second, the optimal concentration of Rhodamine-B in the solution was determined. At room temperature, we found that as the concentration went from 1 droplet of Rhodamine-B to 5 droplets per 10 mL of aqueous CuNO4, the average fluorescence increased from 37.1 (RGB-pixel average) to 86.6. The next step is implementation of a carbon-nanotube solution as the absorption medium and perfecting the image analysis algorithm.
Funding Provided By: UC Riverside Mentoring Summer Research Internship Program