The rate of movement of the contact line is believed to be dependent on the angle the contact line makes with the solid boundary, but the mechanism behind this is not yet fully understood. Analysis of a moving contact line with the no slip condition results in infinite stresses that can't be integrated over. Here, the no-slip boundary condition implies that the position of the contact line does not move, which is not observed in reality.
In the present study, for a given density and viscosity of a transformer oil in a horizontal cooling duct of height, d 4 mm, and duct width variation, b 50 to 100 mm, Re number can be estimated to be in the. (duct height, d) and wetted perimeter, P 2(b + d). 102 The Rotating Machinery, Turbulent Flow, Algebraic yPlus Interface. where the characteristic length,, the cross-sectional area, A (duct width, b). The no-slip condition poses a problem in viscous flow theory at contact lines: places where an interface between two fluids meets a solid boundary. CONTENTS 5 Interfaces 102 The Rotating Machinery, Laminar Flow Interface. While the no-slip condition is used almost universally in modeling of viscous flows, it is sometimes neglected in favor of the 'no-penetration condition' (where the fluid velocity normal to the wall is set to the wall velocity in this direction, but the fluid velocity parallel to the wall is unrestricted) in elementary analyses of inviscid flow, where the effect of boundary layers is neglected. Some highly hydrophobic surfaces have also been observed to have a nonzero but nanoscale slip length. COMSOL Multiphysics designed to assist you to solve and model low-frequency electromagnetics.
U − u Wall = β ∂ u ∂ n is the mean free path. b) Run the Comsol module for a number of different velocities. define the jet width as you would a boundary layer, where the x-velocity is 99 of the free stream velocity.
A common approximation for fluid slip is: a) Run the Comsol module for a particular value of velocity and try to verify the above behavior for both the maximum velocity and the jet width.
at high altitude), even when the continuum approximation still holds there may be so few molecules near the surface that they "bounce along" down the surface. The simulator we use is Comsol 5.3, an advanced numerical solver of partial differential equations including the Navier-Stokes equations and the microscopic Energy Balance equations. ( June 2008)Īs with most of the engineering approximations, the no-slip condition does not always hold in reality.