| The electromagnetic field has been widely used in metallurgy as a effective auxiliary method of improving product quality, which would increase efficency of metal refining. Alternative magnetic filed includes traveling magnetic field and rotating magnetic field. On the basis of advanced fluid mechanics and theory of electromagnetic field, turbulence of molten steel affected by different electromagnetic field has been studied using large eddy simulation (LES). The main works and conclusions are presented as follows.(1)Flow field of molten metal affected by traveling magnetic field in cylindrical reactorThe traveling magnetic field has been widely used in metal refining and solidification. But the knowldgement of transport behivor of molten metal affected by traveling magnetic field is lack, which will hold back the further application of traveling magnetic field. By coupling the traveling magnetic field theory and N-S equation, the three dimensional flow field is produced in cylindrical reactor. The new formulation of electromagnetic force affected by traveling magnetic field is introduced. The simulation result is accord with the experiment result made by Gerbeth, which testifies the self-developed program and model are reliable. The results show that the flow structure of main section in cylindrical reactor affected by traveling magnetic field is made of two symmetrical vortices; when the aspect ratios decreased, the flow structure has no changed, only the shape changed from round to rectangular; when the electromagnetic force increased, the curve of axial direction velocity changes from flat to steeple and the peek and moves close to the bottom wall.(2) Studied on flow structure of molten steel in centrifugal flow tundish with the method of large eddy simulation and physical model experimentCentrifugal flow tundish is used in continuous casting of producing special steel, which has the advantange of effectively removing non-metal inclusion. But the principle operation condition is not clear. For the strength of swirling flow density affected by magnetic field is low, the method of using bend nozzle to increase swirling flow density in rotation chamber is suggested. The water model of centrifugal flow tundish is self-designed. The residence time distribution, dead volume fraction etc have been studied with varying magnetic field density. Results show that the use of rotating magnetic field can increase average residence time and reduce dead volume fraction, which is helpful to exclusion the non-metal inclusion. The optimum condition in the experiment is the oulet area of rotation chamer of 0.75A, and rotating speed of 46 rpm. Through the fitting of the data, the expression of sink depth of fluid level with rotating speed is as follows:H=-3.17×107n3+3.684×10-5n2-0.0001521n, where:H=h/D, H is sink depth of fluid level, D is diameter of rotating chamber; n is rotating speed, rpm.Large eddy simulation (LES) method is developed to resolve the three-dimensional flow structure of centrifugal flow tundish. In the present works, flow field in three cases are simulated and analyzed, i.e. the swirling flow is produced by (a) electromagnetic force with the direct nozzle (b) bending nozzle using height potential energy of molten steel (c) combination of electromagnetic force and bending nozzle. The effect of magnetic field density on flow structure of centrifugal flow tundish is considered. Results show that when the magnetic field density increased from 0.001T to 0.004T, The maximum velocity increased from 0.012m/s to 0.04m/s,the maximum velocity increased linearly when the the magnetic field density increased. The effect of magnetic field density on flow structure is small; the effectiveness of bending nozzle is validated by 15%-19% increment of maximum swirling velocity in rotation chamber which have verified by water experiment.(3) The physical and mathematical research of gas-liquid two phase flow behavior with bottom gas stirring in rotating magnetic fieldArgon gas blowing is the most used tecnology in refining, but the pop problem is that argon gas is very expensive and its efficency is very low. It is suggested that using rotating magnetic field can extend the gas bubble moving distance in reactor. The water model is designed by myself and mixing character of gas-fluid in reactor has been studied. The results show that the rotating magnetic field used in the process of bottom gas stirring can greatly shorten the mixing time in reactor, refine the size of gas bubble, extend the gas bubble moving distance, enlarge the collision area of gas bubble and nonmetal inclusion and is beneficial to removal inclusion. The optimum condition is the position of nozzle at 0.5R, rotating speed at 60 rpm and gas quantity of 0.17m3/h. The three dimensional gas-liquid two phase mathematical model in rotating magnetic field is established. The effect of nozzle position and magnetic field density on flow structure and gas bubble behavior of reactor is considered. The results show that if there is no gas stirring, the flow structure of main section in reactor is made of four symmetrical vortices. If there is only gas stirring, the shape of gas plume is inverted cone, When gas stirring and rotating magnetic field applied together, the flow structure of main section in reactor have changed, which takes more vortices than no gas stirring. The chape of gas plume became spiral and the shape of gas plume simulated is the same with the experiment observation. When the distance between reactor center and nozzle position increased, the distance of gas bubble moving increased in linear form. If the distance between reactor center and nozzle position changed from 0 to 0.75R, the channel length wthich gas bubbles float to free surface is prolonger to 1.54 times at most than without swirling flow. When the magnetic density changed from 0 to 0.012T, the channel length wthich gas bubbles float to free surface is prolonger to 2.21 times at most than without swirling flow.The program is self-developed using FORTRAN language. A finite volume method has been chosen for this calculation of complicated system. The filtered non-linear simultaneous equations are solved by using SIMPLEC algorithm. A combination of Alternating-Direction-semi-Implicit iteration scheme (ADI) and block correction is used to solve the discrete algebraic equations.
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