Research Areas

External Flow and Wind Engineering

Flow control and Aerodynamics

Drag reduction of heavy vehicles using smart flow-control techniques

Cab-roof fairing (CRF)
Gap fairing
Side skirts

Drag reduction of heavy vehicles using flow control devices

Cab-roof fairing (CRF)
Schematic and perspective of (a) 2D cab-roof fairing (CRF) based on the streamlined curvature, (b) 2D CRF with rounded edges (3D CRF), and (c) the modified CRF.
Snapshots of vortical structures represented by iso-surfaces at pressure coefficient (Cp) of -0.2 colored by the streamwise velocity for the (a) vehicle without a CRF, (b) vehicle with a 3D CRF, and (c) vehicle with modified CRF from the results of large-eddy simulation (LES)

The flow over the vehicle with a modified CRF demonstrates better performance in transporting high flow momentum toward the downstream, especially on the side-edges, compared with the flow over the vehicle with a 3D CRF.

Side skirts
(a) Photograph of the 1/15 scale-downed 15-ton truck model (b) The straight-type side skirt. (c) The schematic of the flap-type side skirt with flap angles (δ1 = 0°, δ2 = 0°, δ3 = 30°).
Contour plots of mean streamwise velocity (U/U0) in the x-y plane at z/H = 0.1 behind the rear wheels of the vehicle (a) without and (b) with straight-type side skirt.

The separated region behind the rear wheel is significantly reduced with attaching the side skirt to the vehicle model.

Boat tail
Velocity field and streamlines
Vorticity contours

LIAD (lower inclined air deflector) reduces recirculation region and vorticity behind the rearbody

Aerodynamic characteristics of auto-rotating maple seed and biomimetics

Free-fall test
Superimposed image of an auto-rotating maple seed
3D configuration of maple samaras
Tomographic 3D image and cross-sectional shapes of a typical sample.
PIV measurement of flow around an autorotating maple samaras
Velocity and vorticity contours of flow around an autorotating maple samara at y/R = 0.25, 0.5, 0.75.
Development of a new wind-energy harvesting device
Turbine blade bio-mimicking maple seeds and device of control the pitch and coning angle
Performance was evaluated test results

Superhydrophobic surface for anti-icing & de-icing

Dry-etching process using Ar & O2
Particle bombardment; Ion species are accelerated toward each electrode. Strike the substrate surface and remove the material to be etched. → Generated ‘leaf-like’ micro-scale roughness by only physical modification of the surface

double_arrow Simple and easy fabrication of SHP surface
double_arrow Long-lasting durability in open air
Fabricated superhydrophobic surface
Optimization of surface modification
  • Gas concentration: [Ar], [O2]
  • RF power
  • Plasma exposure time
  • Distance between electrode and sample
Characteristics of fabricated surface
  • High contact angle ( ~ 180°)
  • Low sliding angle ( ~ 1°)
  • No air aging effect
  • Good droplet repellency
Surface characteristics
Bare PTFE sheet; smooth surface
3h treated PTFE sheet; increase of surface roughness