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Title:High gravity convection in mushy layer during alloy solidification
Author(s):Riahi, Daniel N.
Subject(s):Gravity Convection
Alloy Solidification
Abstract:Nonlinear natural convection, driven by compositional buoyancy, in the melt and in cylindrical chimneys within a mushy layer during solidification of binary alloys is investigated under a high gravity environment. In the final form of the solidified material. the chimneys produce freckles, which are imperfections that reduce the quality of the solidified material. Asymptotic and scaling analyses are applied to a non-axisymmetric convection in the melt and in the chimneys. Important parameters in this study are the solutal Rayleigh number R, the centrifugal accelerntion parameter A, the Coriolis parameter T, the Prandtl number Pr, angle ϒ between the rotation axis and the high gravity vector, and ratio H of R in the chimney's liquid zone to that outside in the mushy zone. It is found that there exist Pr, A and T dependent ranges for the radius of the chimney where the wall of chimney may or may not be vertical. For some particular ranges of the rotation rate and sin ≠ 0, convection in the chimneys can increase or decrease with increasing about or below some azimuthally dependent axial level. This level can also depend on Pr, ϒ and T. and on the radii of the chimneys. The chimney convection can also increase or decrease with increasing T in certain P,. y. T and R dependent ranges. Some particular moderate rates of inclined rotation can become so effective. by either centrifugal or Coriolis force. that they lead to vanishingly small radii of the chimneys and suppression of the chimneys' convection. A bound on number density of chimneys is also determined.
Issue Date:1997-07
Publisher:Department of Theoretical and Applied Mechanics. College of Engineering. University of Illinois at Urbana-Champaign
Series/Report:TAM R 859
Genre:Technical Report
Rights Information:Copyright 1997 Board of Trustees of the University of Illinois
Date Available in IDEALS:2021-11-04

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  • Technical Reports - Theoretical and Applied Mechanics (TAM)
    TAM technical reports include manuscripts intended for publication, theses judged to have general interest, notes prepared for short courses, symposia compiled from outstanding undergraduate projects, and reports prepared for research-sponsoring agencies.

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