模口膨胀是聚合物加工中的重要现象,通常用流变效应来解释。射流自由面上温度分布不均匀,必然会产生表面张力梯度驱动的热毛细对流。采用二维非定常有限元方法,数值模拟喷涂于运动固壁上的流变流体的模口膨胀问题。计算中考虑了流变效应和热毛细效应的耦合作用。结果表明,流变效应和热毛细效应两者均使射流截面增大,非Newton流体的流变效应是模口膨胀的主要原因。 Die swell is an important phenomenon in polymer processing and is usually explained by rheology. The non-uniform temperature distribution on the free surface of the jet will inevitably result in the thermal capillary convection driven by the surface tension gradient. A two-dimensional unsteady finite element method was used to simulate the die swell of the rheological fluid sprayed on the moving solid wall. The coupling of rheological effects with thermal capillary effects is taken into account in the calculations. The results show that both the rheological effect and the thermal capillary effect increase the cross section of the jet, and the rheological effect of non-Newton fluid is the main reason for the expansion of the die.