Abstract
The Navier-Stokes' equation of forward difference schemes with nonlinear terms and variable coefficients was solved numerically, using Runge-Kutta-Gill's method. A simulation was carried out with the model over a flat surface where thermal condition was uniform horizontally and sulface roughness increased abruptly along wind direction.
The result showed upward wind component in accordance with deceleration of horizontal air current and increased diffusivity in the developing internal boundary layer in just leeward area above the surface roughness gap. The ceiling of internal boundary layear reached to a fixed height which had relations with stability and a new stationary wind profile was reformed in the adapted layer in the leeward in internal boundary layer. If a height normalized with ceiling of the internal boundary layer was introduced, peak of diffusion coefficient was found almost in the same height in any stability category, which suggested that adapted wind profiles satisfied a similarity law.
Supposing an emission of air pollutant at a windward point above the roughness gap, transfer and diffusion were estimated in the internal boundary layer. The result revealed that air pollutant floated over the internal layer in unstable condition and invaded in a long tongue shape into the internal boundary layer in stable condition.
A numerical model of internal boundary layer produced by the irrgular thermal condition of the ground surface will further be required as the next task.
