【摘要】 针对水平Ｂｒｉｄｇｍａｎ定向凝固过程，得到了超薄试样（数百微米）中自然对流流场的分析解，Ｖｘ＝ρ０αＧＨ３ｇ［４（ｙ／Ｈ）３－（ｙ／Ｈ）］２４μ，并与实验和数值计算结果进行了比较，为晶体生长及凝固理论研究提供了如速度分布、最大速度、流量及质量传输等重要参数。更多还原

【Abstract】 In a 1995 paper[2](submitted in 1993), we showed throush numerical simulation and experimental confirmation that natural convective- now does exist in the Hale -shaw cell in the horizontal Bridgman solidification process. We now give an analytical expression for calculatins the convective- flow velocity field near the s/L interface, allowing us to give a clear physical interpretation of such phenomenon. This analytical expression is eq. (10), for a very thin layer of fluid contained in Hale-Shaw cell. It allows us to calculate Vx, the natural convective - flow velocity. Figs. 3a through 3d give variations of Vx with distance from S/L interface for given temperature gradients of 110℃/cm, 68. 6℃/cm, 30℃/cm, and for sample thickness of 350 μm. From these figures, it can be seen that points computed with eq.(10), denoted by △, agree well with curves computed numerically, denoted by solid lines.Fig. 4 gives variations of Vx with temperature gradient for two given sample thicknesses: 743μm and 521 μm. Fig. 5 gives variation of V: with sample thickness for two given temperature sradients: 14. 7℃/cm and 8. 4℃/cm. In both figures solid lines are based on test data and dashed lines are computed with eq. (10). Computed curves and test curves show similar tendencies. We think that the discrepancies may be caused by deviation of actual temperature field from theoretically assumed one.更多还原