Air entrainment on a moving continuous web

The air boundary layer on a moving continuous web was experimentally investigated in a laboratory coating equipment. The boundary layer thickness was obtained by smoke visualization and measured by image analysis in the range 2.4×10⁴<Re<3×10⁵. According to the web speed, three laminar flow mechanisms were observed, for which the air boundary layer thickness was found to vary from 0.74 to . A survey of the published boundary layer solutions for a moving flat surface was also carried out and their applicability to the present boundary layer problem was studied. It was shown that the Blasius solution is the most suitable to represent the air flow in the case of a moving web.