ELECTROMAGNETIC BRAKING OF THE FLOW OF A LIQUID-METAL WITH A FREE-SURFACE

The electromagnetic braking of liquid metal flowing over a moving boun dary is considered. The flow is two dimensional and the upper boundary is a free surface. The main interest of this Bow originates from the application of horizontal belt strip casting. In this process, the liq uid metal is fed onto a single endless horizontal belt that runs betwe en two rollers. The bottom of the belt is cooled by water and the liqu id is fed onto the belt through a slit. This results in a flow that ca n be modelled as a flat free jet impinging onto a horizontally moving boundary. The Bow after the impingement region is analysed using the b oundary layer equations. Here, the flow depends on the Reynolds number R, the Froude number F, the Hartman number M, and the ratio of the be lt velocity to jet velocity, beta. For beta < F-2/3, We have a supercr itical flow which terminates in a hydraulic jump. For beta > F-2/3, th ere is no hydraulic jump and the film thickness grows smoothly into th e final state with constant thickness and uniform velocity. The brakin g length for the case without hydraulic jump is shown to be of order O ((FRa)-Ra-2/3/2) without magnetic field and of order O(M-2Ra/2) with m agnetic field, where a is the jet width. Thus, the magnetic field decr eases the braking distance considerably. This result is favourable for both the stability of the flow and for the solidification process in the horizontal belt strip casting process. (C) 1998 The Japan Society of Fluid Mechanics Incorporated and Elsevier Sciecne B.V. All rights r eserved.