Superhydrophobic (SHPo) Surfaces
Superhydrophobic (SHPo) surfaces which can be realized when the roughened surfaces are chemically treated to have a hydrophobicity, is known to trap the air pockets between the surface topologies when immersed underwater, thereby creating an effective slip on the surface. This phenomena has a wide range of potential applications and we are trying to apply SHPo surfaces for turbulent flow control. Our main activities are as follows.

1. Separation control for the flow around a bluff body
Water tunnel experiment setup for the velocity measurement in the flow around a SHPo cylinder.
A water droplet on a superhydrophobic surfaces (left), roughened Teflon (middle) and untreated Teflon (right).
SEM image of spraycoated superhydrophobic surfaces (left) and picture of the superhydrophobic circular cylinder (right).
Instantaneous spanwise vorticity contour of acrylic cylinder (left) and superhydrophobic cylinder (right) at ReD = 7000.
Mean flow and normalized urms contour of acrylic cylinder and superhydrophobic cylinder at ReD = 7000.
2. Theoretical modeling of the airwater interface dynamics
Effects of the micrograte geometry on the critical hydrostatic pressure.
Modeling of the plastron on superhydrophobic surfaces (fluctuating pressure in a harmonic function).
Collapse transition on surface geometry and sidewalls in dynamic state.
Effects of surface geometry (left) and sidewalls property (right) on plastron.
3. Turbulent flow control around a hydrofoil with SHPo surface
PIV experiment setup for the velocity measurement of the wake around a hydrofoil.
Pictures of hydrofoil with smooth surface(a,b) and that with SHPo surface(c,d) in the water tunnel.
(AOA = 5 deg, Rec = 5,000)
(AOA = 5 deg, Rec = 5,000)
Instantaneous spanwise vorticity contour of smooth hydrofoil and SHPo hydrofoil at Rec = 10,000
Normalized mean streamwise velocity and Reynolds stress contour of smooth hydrofoil and SHPo hydrofoil
; white solid line – wake bubble (AOA = 5 deg, Rec = 10,000)
; white solid line – wake bubble (AOA = 5 deg, Rec = 10,000)
Normalized mean streamwise velocity and Reynolds stress contour of smooth hydrofoil and SHPo hydrofoil
; white solid line – wake bubble (AOA = 10 deg, Rec = 10,000)
; white solid line – wake bubble (AOA = 10 deg, Rec = 10,000)
4. Experimental measurement of gasliquid interface using RICM(Reflection Interference Contrast Microscopy)
Setup for RICM and its schematic.
Representative results for hole and grate structure.