Preliminary numerical study of the dip-coating process: The boundary conditions

SEBASTIÁN UBAL; DIEGO MARTIN CAMPANA; MARIA DELIA GIAVEDONI; FERNANDO A. SAITA

Santa Fe, Argentina

Congreso; X Reunión sobre Recientes Avances en Física de Fluidos y sus Aplicaciones (FLUIDOS 2008); 2008

Grupo de Flujo de Fluidos y Dinámica Interfacial - INTEC-UNL-CONICET

The classic problem of dip coating consist of pulling a solid substrate of a liquid bath which contain the coating fluid (see Fig. 1).  From the pioneer work of Landau and Levich [1], this problem has been studied using theoretical, experimental and numerical approaches ([2], [3], [4]). A very interesting topic in the numerical solution of the problem are the boundary conditions (BC) to apply. In [4] was used the Boundary Element Method and far away of the dynamic meniscus, the exact Moffatt´s solution [5] was imposed as BC to the flow in the bulk. In [2] the authors solved the equations with the Finite Element Method (FEM) and they considered that fluid is contained in a closed recipient, except for a small hole in the bottom wall where enter a flow rate necessary to maintain a constant level in the bath and, therefore, a steady state (we denote this case as BH). Finally, in [3] the problem was solved with the commercial software FIDAP -which also implements the FEM- but here only the bottom boundary was considered as a solid wall, while the domain is open in the lateral side opposite to the substrate (this case is denoted as BW). In this work we solved the dip coating problem using the FEM and an implicit scheme that compute simultaneously all variables. We present preliminary results obtained by imposing some sets of BC, with the purpose to evaluate its influence on the thickness of coating film, the free surface location and numerical performance.