Experimental investigation of magnetohydrodynamic turbulent pipe flow of aqueous electrolyte solution.

摘要

An experimental study on a turbulent pipe flow of an aqueous electrolyte solution under a transverse magnetic field has been carried out. The main objective of the study is to enhance understandings of physical phenomena and engineering prediction capability in the design activities of the liquid breeder blanket for nuclear fusion reactor utilizing Flibe ((LiF)2BeF 4) coolant.;Flow field measurements were performed using PIV technique, which gives significantly higher spatial resolution compared to the previous data and enables us to infer in-depth physical insights for MHD turbulent flows as well as to provide a detailed experimental database for validating the numerical simulations and models. The dominant non-dimensional parameters that characterize the MHD effect were found to be different in the near-wall and core regions. Turbulence suppression is characterized by the interaction parameter on the pipe centerline whereas Ha/Re seems to be adequate for near-wall turbulence. The experimental data for the flow under the fringing magnetic field suggests that the flow modification starts in the near-wall region and propagates into the core region as the flow develops. The suppression of turbulence can be explained as a consequence of the reduction in turbulence production due to the interaction of the Hartmann flattening and Reynolds shear stress. Moreover, the turbulence suppression is a gradual process of the interaction between turbulence production and fluctuation rather than a sudden stop of the production or a damping of the fluctuation. Comparison with the DNS database shows good agreement for the mean velocity profiles. As for the turbulence intensities, there was a consistent tendency that DNS underestimate the turbulence intensities.;Heat transfer experiments were performed using two different diameter pipes with electrically conducting wall. The local and average Nusselt number was determined by temperature measurement, and the mean and fluctuating fluid temperature profiles were also measured. The average Nusselt number decreases as the applied magnetic field increases. The existing empirical correlation is confirmed to be valid for limited parameter range. For low Reynolds number cases, buoyancy effect is also significant, and buoyancy effect is promoted as the turbulence is suppressed by MHD effect.