Convection is the main reason for surface roughness in both polymeric and non-polymeric films obtained by the drying process (solvent evaporation). It is important to find the origin to control this phenomenon which leads to the creation of a variety of surface patterns that are formed on the polystyrene/methyl ethyl ketone solution in various thicknesses and concentrations. In this research, the convection flow was observed and analyzed at the surface and depth of the polymeric fluids using Particle Image Velocimetry method. Counter-rotational flow was observed in the cross section of each cell and the flow direction was found to be ascending in the cell center and descending around it. The non-dimensional Rayleigh number (based on buoyancy) and Marangoni number (based on surface tension) were calculated to determine the convection dominant mechanism. The critical value of each number is the threshold for starting instabilities. According to the calculations based on initial assumptions and solving the one-dimensional mass transfer equation in a layer of the solution as well as controlling the effective parameters such as concentration, thickness and viscosity. Rayleigh convection was observed in a certain thickness and concentration of the samples, while concentration Marangoni convection was only observed in some of them. However, both concentration and thermal Marangoni were found in most samples.

对流是通过干燥工艺（溶剂蒸发）获得的聚合物膜和非聚合物膜的表面粗糙度的主要原因。重要的是找到控制这种现象的根源，这种现象导致形成各种厚度和浓度的聚苯乙烯/甲基乙基酮溶液上形成的各种表面图案。在这项研究中，使用粒子图像测速法在聚合物流体的表面和深度观察并分析了对流。在每个单元格的横截面中观察到反向旋转流动，并且发现流动方向在单元格中心上升并在其周围下降。计算了无量纲的瑞利数（基于浮力）和Marangoni数（基于表面张力）以确定对流主导机制。每个数字的临界值是启动不稳定的阈值。根据基于初始假设的计算并求解溶液层中的一维传质方程，并控制有效参数，例如浓度，厚度和粘度。在一定厚度和样品浓度下观察到瑞利对流，而仅在其中一些样品中观察到浓度马兰戈尼对流。但是，在大多数样品中都发现了浓度和热Marangoni。根据基于初始假设的计算并求解溶液层中的一维传质方程，并控制有效参数，例如浓度，厚度和粘度。在一定厚度和样品浓度下观察到瑞利对流，而仅在其中一些样品中观察到浓度马兰戈尼对流。但是，在大多数样品中都发现了浓度和热Marangoni。根据基于初始假设的计算并求解溶液层中的一维传质方程，并控制有效参数，例如浓度，厚度和粘度。在一定厚度和样品浓度下观察到瑞利对流，而仅在其中一些样品中观察到浓度马兰戈尼对流。但是，在大多数样品中都发现了浓度和热Marangoni。