Events
Department of Mathematics and Statistics
Texas Tech University
Abstract: This talk explores the aerodynamics of complete aircraft geometries at the initial conceptual design stage and the importance of understanding the propulsion-related aerodynamics and performance of ducted fans and open rotors for their integration. A ducted rotor system was used to produce turbulent jets with a Reynolds number up to 5.97x105 and Mach number of 0.222 based on mean streamwise velocity. Three rotors with a diameter of 11.8 cm were manufactured and tested inside a duct with a 1 mm tip clearance at a speed up to 30, 000 revolutions per minute (rpm). three different blade planform shapes were used including a rectangular shape with constant chord, trapezoidal shape with a taper ratio of 0.5, and elliptical shape where the trailing edge of the blade is expressed with an elliptical function. The rotor thrust and electric power were measured, and the thrust coefficient and figure of merit was computed. The flow-field produced by the ducted rotors was measured in the near-field using laser Doppler velocimetry techniques. Time-averaged contours of cross-stream vorticity reveal intense hub and blade tip vortex structures, which are impacted by the shape of the blade, particularly in the blade tip region. Tip vorticity as well as streamwise turbulence intensity and turbulent kinetic energy in this region were mitigated for the rotors with trapezoidal and elliptical blades. In a related study, the blades of a 12 cm diameter ducted rotor system were coated with a sharkskin- inspired surface with diverging tip micropillars. Surfaces containing 40 μm and 70 μm tall micropillars were applied on the rotor blades in order to study their role on fan aerodynamics and downstream jet flow. The effect of the micropillar coatings on the rotor blades marginally increases the mean streamwise velocity and rotor figure of merit due to mitigating boundary layer separation at higher rotor speeds. Moreover, this occurs due to the micropillar’s ability to increase wall-normal turbulence intensity in the boundary layer when the pillar height is scaled appropriately to the boundary layer thickness. The rotor hub and blade tip vortex structures become diffused and undergo breakup into smaller structures accompanied with an acceleration in the decay of absolute mean cross-stream vorticity.
When: 4:00 pm (Lubbock's local time is GMT -6)
Where: room Math 011 (Math Basement)
ZOOM details:
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Direct Link that embeds meeting and ID and passcode.
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* Meeting ID: 949 9288 2213
* Passcode: Applied
abstract noon CST (UTC-6)
Zoom link available from Dr. Brent Lindquist upon request.