CXLII. Experiments on magneto-hydrodynamic channel flow

Abstract

Experiments are described in which measurements of pressure gradient were taken during the flow of mercury in a rectangular channel of 15 : 1 aspect ratio, in the presence of a transverse magnetic field. It was possible to suppress turbulence even at the highest obtainable Reynolds Number (R=10⁵). For high values of R, the friction coefficient C _f appears to be a function of M/R and β. It is suggested that when R is large enough C _f might be a function of the single group M/Rβ _1/2 . This is comparable with the simple relationship proposed by Hartmann and Lazarus (1937). Lundquist (1952) has suggested that the transition from laminar to turbulent flow occurs at a fixed value of R/M, and that β does not enter into this criterion. The experiments suggest that the critical condition for the turbulent to laminar transition is R/M ≈ 900, although since only one liquid was used, it was not possible to determine the influence of β.