Towards Emulating Geophysical Boundary Layers with Variable Density Experiments*

Boundary layer flows in geophysical settings are often modulated by buoyancy. Vertical temperature gradients in the Atmospheric Boundary Layer (ABL) can invigorate or sap the energy of turbulent motions, resulting in a change in mean profile, turbulence intensity, and turbulence structure. These modifications to the ABL have implications for weather/climate forecasting, wind energy, and pollutant dispersion. Replicating geophysical boundary layers in laboratory experiments is challenging as high Reynolds numbers and non-vanishing Richardson numbers are required. This talk will discuss the development of an experimental facility specialized for studying geophysical boundary layers, the Princeton SuperTank.

The SuperTank is a compressed air facility analogous to a closed-return wind tunnel but has an unconventional geometry. The test section and return section are concentric. A 12.4 m long cylindrical pressure vessel with 2 m diameter houses a square test section of 0.88 m width and 7 m length. Air pressurized up to 80 bar flows through the test section with velocities from 0.5-10 m/s. A heated flat plate with controllable surface temperature is installed in the test section. By using compressed air, high Reynolds numbers and order unity Richardson numbers can be achieved simultaneously. We report on the design, manufacture, and construction of the SuperTank as a versatile facility for studying geophysical boundary layers and other high Reynolds number phenomena.