Several fluid mechanical instabilities originate due to buoyancy, surface tension and rotational forces in a Czochralski (Cz) crystal growth process. The origin of the flow instabilities is briefly summarized in this paper. In order to contribute further to the understanding of the flow instabilities in Cz crucibles with silicon melts, the three-dimensional fluid flow in the melt was investigated numerically in the presence of Marangoni convection. The turbulent nature of the flow was captured by a "quasi-direct numerical simulation" methodology. A multigrid method was adopted to accelerate the numerical simulations with a grid of one million nodes. The Marangoni convection was found to play a significant role in the overall properties of the temporal thermal and flow fields including its associated instabilities. In the presence of Marangoni convection, single-folded thermal waves were noticed at the surface of the melt, as also reported in experiments (J. Crystal Growth 233 (2001) 687); three-folded waves were present in the results obtained when the Marangoni effect was neglected. (C) 2003 Elsevier Science B.V. All rights reserved.