RESEARCH INITIATION AWARD: TAILORING JET INSTABILITIES USING ULTRASONIC MICROACTUATORS

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Research Initiation Awards provide support for junior and mid-career faculty at Historically Black Colleges and Universities who are building new research programs or redirecting and rebuilding existing research programs. It is expected that the award helps to further the faculty member's research capability and effectiveness, improves research and teaching at his home institution, and involves undergraduate students in research experiences. The award to Tuskegee University has potential broader impact in a number of areas. The goal of the project is to study fundamental characteristics of jet instability and its potential alteration using an ultra-frequency micro-fluidic actuation technique called resonance enhanced microjets (REM). Instability modification, using REM, has potential applications in augmentation of air-fuel mixing in supersonic flow and control of jet noise. Undergraduate students will gain research experience in experimental fluid mechanics. A course in experimental fluid mechanics that includes topics such as digital data acquisition, random data analysis and gas dynamics will be developed.This project includes the design and fabrication of REM in the ultra-frequency range (above 20 kHz) and the study of their interaction and impact on shear layer dynamics of an air jet in free and cross-flow configuration. The jet properties will be studied using unsteady intrusive probes as well as non-intrusive techniques such as laser based microschlieren and planar scattering imaging. The proposed micro-actuation scheme is expected to modify inherent instabilities of a jet, exciting the most unstable modes and generating high frequency three dimensional vorticities for enhanced entrainment and diffusion. The actuators proposed here can produce high momentum pulsed disturbances up to 50 kHz generating instabilities every 20 microseconds in the cross-flow jet. Since such a time scale is very close to the mixing time of a high-speed combustor, this approach is expected to potentially enhance air-fuel mixing in supersonic flows. Fundamental studies on such a tailored jet flowfield will be useful for designing high-speed combustors with improved air-fuel mixing and flame stability.