The value of represents the saturated state, with being the supersaturated condition at the temperature of the solution in the growth chamber. The maximum crystal size grown in each experiment has been used to non-dimensionalize the coordinates. In the following sections, the normalized concentration gradient is based on the ratio of the maximum concentration difference and maximum crystal size. The contours in Figure 5.21(a), corresponding to zero rotation, indicate an almost uniform and symmetric distribution of solute in the growth chamber, both near the crystal and in the bulk of the solution for . The contours shown in Figure 5.21(b) also reflect a similar trend over the comparable time period . Initially the contours are localized in the vicinity of the crystal surfaces, with the bulk of the solution being at the supersaturated state . This phase of the experiment corresponds to the growth process with transport across a diffusion layer, and correlates well with the schlieren images shown in Figure 5.19 where there is no well-defined upward movement of the buoyant plume. The effect of rotation of the growing crystal can be clearly seen in the contours shown for hours, for locations below the crystal . While those shown in Figure 5.21(a) (purely buoyancy-driven) depict a larger spread in the upward direction along the seed holder, contours corresponding to 15 rpm are relatively flat. Thus, a uniform distribution of solute is indicated in the solution in the presence of rotation, owing primarily to a mixing action. The vertically rising plume is narrower in the presence of rotation, but broadens with time. At t=45 and 90 hours, Figure 5.21(a) shows a slight breakdown in symmetry of the concentration contours below the crystal, with respect to the seed holder, though the plume maintains symmetry. Rotation, on the other hand, enforces a better symmetry to the concentration distribution around the crystal. This is clearly visible at 55 hours in Figure 5.21(b). At 100 hours, the plume is strongly influenced by buoyancy and is as broad as in the case of no rotation. The swirl flow pattern superimposed on buoyant flow by crystal rotation imparts anti-symmetry to the iso-concentration contours. This pattern continues to represent a new form of symmetry for the growth of good quality crystals.

At t=20 hours, an asymmetric set of contours is seen in the region below the growing crystal. This temporary asymmetry in the concentration contours is in agreement with the corresponding schlieren image shown in Figure 5.20(iii). It is related to the joint influence of buoyancy and rotation. At other times, either rotation or buoyancy predominates, and symmetry in the concentration distribution is restored.