Numerical simulation of blade-over-roll coating forming flows

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Numerical simulation of blade-over-roll coating forming flows

Evan Mitsoulis, George Athanasopoulos

School of Mining Engineering and Metallurgy, National Technical University of Athens, Zografou 157 80, Athens, Greece.

DOI:

https://doi.org/10.7494/cmms.2010.4.0286

Abstract:

Numerical simulations have been carried out via the finite element method (FEM) for the forming flow of coating using a system of blade and roll. The flow domain encompasses both the coating fluid reservoir and the doctor-blade region with free surface and is fully two-dimensional. The materials of this study are Newtonian and shear-thinning polymer solutions used previously in an experimental and theoretical investigation. The pseudoplasticity of the polymeric liquids is modelled by the Carreau model, which fits well experimental data for the shear viscosities. For different roll speeds, the entire flow domain is analyzed, and the extent and shape of recirculating zones are found. Large vortices appear in the reservoir, and their intensity is computed under different operating conditions and blade geometries. The computed free surface profiles and coating thicknesses are in close agreement with the experimental ones. Shear thinning increases the coating thickness for a given geometry, as was also found experimentally, when compared with the Newtonian values. This increase is valid up to power-law index n > 0.3, while extreme shear-thinning (power-law index n < 0.3) reduces the coating thickness. This new finding is in agreement with previous findings in other geometries for highly shear-thinning fluids. The vortex decreases in size and intensity monotonically and linearly with n, in the range 1  n > 0. The simulations also provide a wealth of information regarding stresses and pressures and show that some geometries are better than others in coating operations. The flow geometry provides an interesting case for simulation and design, due to a combination of fluid mechanics and shear-thinning phenomena that take place in this flow field.

Cite as:

Mitsoulis, E., & Athanasopoulos, G. (2010). Numerical simulation of blade-over-roll coating forming flows. Computer Methods in Materials Science, 10(4), 214 – 224. https://doi.org/10.7494/cmms.2010.4.0286

Article (PDF):

Keywords:

Coating flows, Blade-and-roll coating, Carreau constitutive equation, Shear thinning, Vortex development

References:

Barakos, G., Mitsoulis, E., 1995, Numerical simulation of extrusion through orifice dies and prediction of Bagley correction for an IUPAC-LDPE melt, J. Rheol, 39, 193-209.

Davard, F., Dupuis, D., 2000, Flow visualization experiments in a blade coating process, J. Non-Newtonian Fluid Mech., 93, 17-28.

Kistler, S.F., Scriven, L.E., 1984, Coating flow theory by finite element and asymptotic analysis of the Navier-Stokes system, Int. J. Num. Meth. Fluids, 4, 207-229.

Loest, H., Lipp, R., Mitsoulis, E., 1994, Numerical flow simulation of viscoplastic slurries and design criteria for a tape casting unit, J. Amer. Ceram. Soc, 77, 254-262.

Missirlis, K.A., Assimacopoulos, D., Mitsoulis, E., Chhabra, R.P., 2001, Wall effects for motion of spheres in power-law fluids, J. Non-Newtonian Fluid Mech., 96, 459-471.

Mitsoulis, E., 1990, Numerical simulation of viscoelastic fluids, in Encyclopedia of Fluid Mechanics, 9, Polymer Flow Engineering, ed., Cheremisinoff, N.P., Gulf Publ. Co., Dallas, Texas, USA, 649-704.

Mitsoulis, E., Pham, T.V., 1996, Numerical simulation of rheological effects in blade coating flows, Proceedings of Xllth International Congress on Rheology, eds, Ait-Kadi, A., Dealy, J.M., James, D.F., Williams, M.C., Chem. Eng. Dept., Univ. Laval, Quebec City, CANADA, 423-424.

Mitsoulis, E., Triantafillopoulos, N., 1997, Viscoelasticity in blade coating of non-Newtonian fluids, Proceedings of the 1997 TAPPI Advanced Coating Fundamentals Symposium, Philadelphia, PA, USA, 27-41.

Mitsoulis, E., Vlachopoulos, J., Mirza, F.A., 1984, Numerical simulation of entry and exit flows in slit dies, Polym. Eng.Sci.,24, 707-715.

Mitsoulis, E., Wagner, R., Heng, F.L., 1988, Numerical simulation of wire-coating low-density polyethylene: theory and experiments, Polym. Eng. Sci., 28, 291-310.

Sullivan, T., An Experimental and Computational Investigation of Rheological Effects in Blade Coating, PhD Thesis, University of California, San Diego, CA, USA.

Sullivan, T., Middleman, S., 1986, Film thickness in blade coating of viscous and viscoelastic liquids, J. Non-Newtonian Fluid Meek, 21, 13-38.

Sullivan, T., Middleman, S., Keunings, R., 1987, Use of a finite-element method to interpret rheological effects in blade coating, AIChE J., 33, 2047-2056