The potential of Using Superhydrophobic Airfoils in Laminar Regime: a Numerical Approach

Fluids at their interface with ordinary solids are motionless. This condition is referred to as no-slip condition. On superhydrophobic surfaces, fluids have slip velocity which is quantified using Navier’s slip length definition. On a superhydrophobic, slip velocity can be as large as %05 of the free-stream’s velocity. We have studied the potential of using superhydrophobic airfoils to improve the performance of airfoils. For that, NACA 1112, 1114, and 1121 were studied numerically. The chord-based Reynolds number was approximately %000. We found that increasing the slip from 0 to %05 results in up to 66% increase in the lift, and 1%5 decrease in the drag force when angle of attack is small (i.e. <%o). For larger angle of attack values (i.e. >%o), using superhydrophobic airfoil is still worthy, but its effectiveness becomes smaller. The less efficacy of superhydrophobic airfoils is explained by the laminar separation bubble phenomenon which can have an adverse effect on lift and drag. For small angle of attack values, by increasing the slip from 0 to %05, the bubble’s length becomes smaller which is favorable and explains the well-behaviour of superhydrophobic airfoils at small angle of attacks. However, for larger angle of attack values, by increasing the slip, bubble’s length grows which results in less efficacy of superhydrophobic airfoils at larger angle of attack values.

Keywords:

Airfoil , Superhydrophobic , Lift , Drag , Laminar Separation Bubble