Drag Reduction: SLIPS

  • Project

    Graduate Student: Matthew Fu

    Matt Fu is conducting research into the role of the wall boundary conditions in governing transport from the wall to the free stream. Specifically this research seeks to establish how momentum transport is affected when the "no-slip" boundary condition is replaced with various "slip" boundary conditions. These results hopefully further our understanding of wall-turbulence interaction to better develop passive flow control surfaces to control drag or mixing. The current work utilizes Liquid Infused Surface [LIS], Superhydrophobic Surfaces [SHS] and Slippery Liquid Infused Porous Surfaces [SLIPS], which have been shown to reduce drag through this slip effect, and seeks to model how their surface morphology and lubricant properties affect the magnitude of their effective slip. The resulting models can be validated in a table-top, high shear, channel flow facility outfitted for interchangeable surface slides.

Sensor Development

  • Project

    Graduate Student: Yuyang Fan

    This research focuses on designing and manufacturing MEMS devices for turbulence measurements (both scalars and vectors). Conventional sensors suffer from limited spacial and temporal resolutions in high Reynolds number flows or in the near-wall regions of wall-bounded flows. Development of MEMS technology enables mass-production of smaller sensors that can improve sensing resolutions as well as to probe regions of interest that conventional technology could not reach. Yuyang is currently developing MEMS hot- and cold-wires for more accurate turbulence velocity and temperature measurements, as well as sensors to measure humidity in gaseous environment.

Turbulent Heat Transfer

  • Project

    Graduate Student: Clayton Byers

    Clay is performing research in turbulent boundary layers with temperature as a passive scalar. The investigation utilizes mathematical techniques previously developed for the velocity field, but applied to the temperature field to understand the possible functional forms of the temperature distribution. Analysis also includes the temperature variance, with future work to include the turbulent heat flux parameters. The theory is then applied to experimental results obtained in the Princeton water channel located at the Forrestal campus. The data is collected using the novel nano-scale sensors developed within this lab. In addition, investigation into the nano-scale sensors and their design and characteristics is being conducted, with the goal of maximizing their use and fine tuning their design.

Compressible Flows

  • Project

    Graduate Student: Katherine Kokmanian

    Katherine's interest in compressible flows combined with her interest in boundary layers has led her to investigate turbulent boundary layer theory in compressible flows. Her objectives include developing a nanoscale silicon-based sensor which can accurately measure both velocity and temperature fluctuations and later testing this new design in the Mach 3 wind tunnel. She hopes to develop a sensor which can resolve turbulent statistics in both supersonic and hypersonic flows.

Wind Turbine Aerodynamics

  • Project

    Graduate Student: Mark Miller
    Research Assistant: Janik Kiefer

    With the newest wind turbines reaching nearly 200 meters in diameter, it becomes increasingly difficult to perform computer simulations or laboratory experiments which match all of the governing parameters simultaneously. Prior work has been limited by the interplay of the three important non-dimensional numbers, namely the Reynolds number, Tip Speed Ratio, and the Mach number. In traditional, small-scale wind tunnels these three parameters are impossible to match with the full-scale values.
    The novel aspect of Mark and Janik's work in the Hultmark lab involves using a high-pressure wind tunnel in which the density can be varied, and thus the Reynolds number can be adjusted independently of the Tip Speed Ratio. With this facility Mark and Janik are able to completely match the flow of full-scale wind turbines in a small, laboratory environment. Future work will investigate the Reynolds number dependence of the power and thrust loading on the turbine. In addition, this facility is instrumented with a hot-wire traverse which allows detailed studies of the turbine wake. Such aspects as wake expansion, stability, and turbulence levels under controlled conditions can all be studied. The results of these experiments aim to improve numerical simulations and engineering design codes used for wind turbines.