Skip to main content
    • Aa
    • Aa

Experimental study of convection in a mushy layer during directional solidification

  • C. F. Chen (a1)

Results of experiments using a number of techniques to study the nature of convection in a mushy layer generated by directional solidification of aqueous ammonium chloride solutions are reported. The techniques include flow visualization using a dye tracing method to study convection within the mushy layer before and after the onset of plume convection, and X-ray tomography to measure the solid fraction of a growing mush. The principal results are as follows. (i) Prior to the onset of chimneys, there is no convective motion in the mush, in spite of the vigorous finger convection at the mush-liquid interface. (ii) When the plume convection is fully developed, the flow of fluid in the mush consists of a nearly uniform downward motion toward the bottom of the tank, horizontal motion along the bottom toward the chimneys, then upward plume motion through the chimneys in the liquid region above the mush. (iii) The solid fraction of a growing mush as determined by X-ray tomography shows a significant decrease toward the bottom of the tank after the chimneys are fully developed. As a result, the concomitant increase in the local permeability can be as much as 50%. Some of the results reported herein confirm theoretical predictions of Worster (1992) and Amberg & Homsey (1993). Others reveal phenomena not observed heretofore.

Hide All
Amberg, G. & Homsy, G. M. 1993 Nonlinear analysis of buoyant convection in binary solidification with application to channel formation. J. Fluid Mech. 252, 7998.
Barrett, H. H. 1981 Radiological Imaging, pp. 334, 376. Academic.
Chen, C. F. 1992 Convection in the mushy zone during directional solidification. In Interactive Dynamics of Convection and Solidification (ed. S. H. Davis, H. E. Huppert, U. Müller & M. G. Worster), pp. 139141. Kluwer.
Chen, C. F. & Chen, F. 1991 Experimental study of directional solidification of aqueous ammonium chloride solution. J. Fluid Mech. 227, 567586.
Chen, F., Lu, J. W. & Yang, T. L. 1994 Convection in directional solidification of aqueous ammonium chloride solutions. J. Fluid Mech. 276, 163188.
Copley, S. M., Giamei, A. F., Johnson, S. M. & Hornbecker, M. F. 1970 The origin of freckles in unidirectionally solidified castings. Metall. Trans. 1, 21932204.
Emms, P. W. & Fowler, A. C. 1994 Compositional convection in the solidification of binary alloys. J. Fluid Mech. 262, 111139.
Hellawell, A. 1987 Local convective flows in partly solidified alloys. In Structure and Dynamics of Partially Solidified Systems (ed. D. E. Loper). NATO Series E, Vol. 125, pp. 322. Martinus Nijhoff.
Hellawell, A., Serazin, J. R. & Steube, R. S. 1993 Channel convection in partially solidified systems. Phil. Trans. Roy. Soc. Lond. A 345, 507544.
McDonald, R. J. & Hunt, J. D. 1970 Convective fluid motion within the interdendritic liquid of a casting. Metall. Trans. 1, 17871788.
Roberts, P. H. & Loper, D. E. 1983 Towards a theory of the structure and evolution of a dendritic layer. In Stellar and Planetary Magnetics (ed. A. M. Soward), pp. 329349. Gordon and Breach.
Sample, A. K. & Hellawell, A. 1984 The mechanisms of formation and prevention of channel segregation during alloy solidification. Metall. Trans. A 15, 21632173.
Sarazin, J. R. & Hellawell, A. 1988 Channel formation in Pb-Sn, Pb-Sb, and Pb-Sn-Sb alloy ingots and comparison with the system NH4Cl-H2O. Metall. Trans. A 19, 18611871.
Tait, S., Jahrling, K. & Jaupart, C. 1992 The planform of compositional convection and chimney formation in a mushy layer. Nature 356, 406408.
Tait, S. & Jaupart, C. 1992a Compositional convection in a reactive crystalline mush and melt differentiation. J. Geophys. Res. 97, 67356756.
Tait, S. & Jaupart, C. 1992 New experiments on compositional convection. In Interactive Dynamics of Convection and Solidification (ed. S. H. Davis, H. E. Huppert, U. Müller & M. G. Worster), pp. 155158. Kluwer.
Worster, M. G. 1991 Natural convection in a mushy layer. J. Fluid Mech. 167, 481501.
Worster, M. G. 1992 Instabilities of the liquid and mushy regions during directional solidification of alloys. J. Fluid Mech. 237, 649669.
Worster, M. G. & Kerr, R. C. 1994 The transient behaviour of alloys solidified from below prior to the formation of chimneys. J. Fluid Mech. 269, 2244.
Recommend this journal

Email your librarian or administrator to recommend adding this journal to your organisation's collection.

Journal of Fluid Mechanics
  • ISSN: 0022-1120
  • EISSN: 1469-7645
  • URL: /core/journals/journal-of-fluid-mechanics
Please enter your name
Please enter a valid email address
Who would you like to send this to? *


Full text views

Total number of HTML views: 0
Total number of PDF views: 18 *
Loading metrics...

Abstract views

Total abstract views: 79 *
Loading metrics...

* Views captured on Cambridge Core between September 2016 - 23rd October 2017. This data will be updated every 24 hours.