Flow simulation in the nip of a rigid forward roll coater

This paper shows the development of an efficient solution algorithm for the simulation of a forward roll coating flows with free surfaces. The technique is based on the method of successive approximation combined with a method for rapidly finding a good starting point, i.e. a good initial computational domain. Movement of the free surface from the initial to final positions is demonstrated using both kinematic and normal stress schemes. Adaptive domain decomposition at each pseudo time step is performed with no significant cost penalty. The flow field is computed using a finite element solution of the Navier-Stokes equation. The proposed scheme is shown to be flexible enough to accommodate different scenarios over the practical range of many applications, i.e. capillary numbers in the range of 0.01-300, and a wide range of gap settings and rotational speeds. A close match is found between simulation and experimental meniscus profiles as well as nip pressure profiles. Overall the technique is quite robust and is able to simulate a variety of coating flow situations without resorting to over-simplifications. Copyright (c) 2005 John Wiley & Sons, Ltd.