Transition to turbulence in ducts and in a wind tunnel

The laminar-turbulent transition of flow of a conducting fluid in a longitudinal magnetic field in ducts of circular, rectangular, and triangular cross-sections and over a sphere in a wind tunnel is examined from a unified standpoint. In the approach used here, the macroscopic random diffusion of liquid particles due to the presence of an initial turbulent front is considered along with viscous (molecular) diffusion. In all the cases studied, the results obtained are found to be in good agreement with experimental data.