Experimental investigation of velocity disturbance features in turbulent MHD duct flows

Abstract

The results are described of a number of recent experiments carried out for obtaining additional data on the nature of turbulence suppression in electrically conducting liquids by a magnetic field and on the nature of velocity disturbances which remain after flow laminarization. This problem was investigated previously by this author and his coworkers [1,2]. The present experiments were carried out by means of hot-film anemometry, which was used both for measuring the intensity of velocity disturbances and for measuring two-point correlations of the disturbances. In addition, the pressure drop along the duct was measured. All the measurements were carried out in a rectangular duct in a transverse magnetic field which can be regarded as azimuthal. Situations with different entrance conditions of the flow into the magnetic field were compared. The measurements were intended not so much for accumulating quantitative data, as for comparing qualitative features of the phenomena under study at a variety of experimental conditions. The results which were obtained serve as a further confirmation of a previously suggested hypothesis to the effect that although the magnetic fields tend to convert turbulence to the two-dimensional form, the close to two-dimensional velocity disturbances observed in flows laminarized by magnetic fields are most likely generated in the region where the flow enters the magnetic field and not, as is sometimes assumed, “residues” of turbulence forced to decay by the magnetic field.