Studies on the Redaimed Land Dike from the Standpoint of Agricultural Engineering II. The Experiments on the Turbulent Diffusion Coefficient of the Air-Flow and the Surface Water-Flow through a Long Channel

In order to investigate the turbulent diffusion coefficient (coefficient of turbulent kinematic viscosity or coefficient of turbulence), there are several methods. The author used smoke tubes and ink in these experiments. In both cases, he took the next equation K_z=U/2･dz^^2/dx where Kz : turbulent diffusion coefficient of vertical direction (cm^2/S) U : mean velocity of flow (cm/S) z : width of diffusion (cm) x : distance from the smoke tubes or dropping point of ink to the surveying point (cm) The following results were obtained : (i) K_z = 18.000cm/S in case (A), and K_z = 12,000 cm^2/S in case (B) at a point 6.4m high from the ground surface, and the mean velocity of the air-flow is 7.2m/S. (ii) K_z =5.13cm^2/S at the mean velocity of water-flow is 18.5cm/S, K_z = 1.83cm^2/S at 8.85cm/S, and K_z = 0.47cm^2/S at 4.7cm/S.