Flow visualisation experiments in a blade coating process

Flow visualisation experiments have been carried out with a simple geometry of blade coating. The velocity of substrate and the height of the blade remain constant while the angle of the blade varies. Fluids with different rheological properties have been tested: Newtonian, shear thinning weakly elastic, elastic with constant viscosity. One observes the existence of a stagnation point under the blade. Its location depends on both the rheology of the fluid and the angle of the blade. As the elasticity of the fluid increases, a swelling of the streamlines at the entrance of the device and instabilities appear. These are related to elongational effects. (C) 2000 Elsevier Science B.V. All rights reserved.