Sustained Drag Reduction in Turbulent Taylor-Couette Flows Enabled by Low-Temperature Leidenfrost Effect

A submerged body can be heated past its Leidenfrost temperature to form a thick, continuous film of steam between itself and the water. Here we employ a superhydrophobic surface to drastically reduce the energy input required to create and sustain such a boiling film, and use the resulting slip boundary condition to achieve skin friction drag reduction on the inner rotor of a bespoke Taylor-Couette apparatus. We find that skin friction can be reduced by over 90{\%} relative to an unheated superhydrophobic surface at \textit{Re}$=$ 19,200, and derive a boundary layer and slip theory to fit the data to a model that calculates a slip length of 3.12 $\pm$ 0.4 mm. This indicates that the boiling film has a thickness of 112 $\mu$m, which is consistent with literature.