The laminar flow in a duct can be found by the exact solution of the Navier-
Stokes equation. An experimental apparatus that changes the flow using a detachable
channel side plate can be used to measure the velocity profile or pressure drop in order
to find the dominant determiner of the wall’s characteristics. In this section, the
mechanism of the apparent fluid slip is discussed by comparing the experimental test
results from two ducts having hydrophobic walls with different structural characteristic
but almost the same water-repellency characteristics. Different kinds of hydrophobic
walls were produced for duct wall, and the laminar drag reduction was examined by
measuring the pressure drop.
Keywords: Drag reduction, laminar flow, duct flow, exact solution, friction
factor, velocity profile, highly water-repellent wall, slip velocity, fractal surface,
prototype surface, flow visualization, gas-liquid interface.
