Introduction to COMSOL Rowan University（介绍COMSOL罗文大学）.pdfVIP

Flow Between Parallel Plates – Modified from the COMSOL ChE Library module rev 10/13/08 Modified by Robert P. Hesketh, Chemical Engineering, Rowan University Fall 2008 Introduction to COMSOL The following flowchart gives the overall procedure for setting up a problem into COMSOL Multiphysics, solving the problem and then analyzing the information. 1. Read the problem statement 2. Select Equation(s) and coordinate system that you will be using. (e.g. momentum balance, energy balance etc.) 3. Enter constants 4. Draw Geometry 5. Specify Boundary Conditions – for all boundaries 6. Create a mesh or grid by dividing the geometry into smaller elements. 7. Solve equations 8. Graph numerical results The Navier-Stokes Equations The Navier-Stokes are a special form of the momentum balance and are discussed in section 15.4 of de Nevers. The following assumptions are employed in their use: 1. The fluid has constant density 2. The flow is laminar throughout 3. The fluid is Newtonian 4. The 3-dimensional stresses in a flowing, constant-density Newtonian fljid have the same form as the 3-demensinoal stress in a solid body that obeys Hooke’s law (perfectly elastic, isotropic solid) The Incompressible Navier-Stokes application mode in COMSOL is somewhat more general than this and is able to account for arbitrary variations in viscosity and small variations in density; say through the Boussinesq approximation. This section provides a summary of the participating equations and boundary conditions for one of the most commonly used physical descriptions used in mathematical modeling. EQUATIONS The equations in the Navier-Stokes application mode are defined by Equation 4-1 for a variable viscosity and constant density. The momentum balances and continuity equation form a nonlinear system of equations with three and four coupled equations in 2D a