Example Flow in a Serpentine Mixer

FEMLAB has many options for boundary conditions. The finite element method is based on integrating the equations by parts and applying the divergence theorem. Thus, the allowable boundary conditions are really determined by the equations. The basic conditions of fluid mechanics are that either the velocity or forces must be specified. In a three-dimensional problem, you would need to specify three velocities, for example, at each boundary point, or some combination of velocities and forces. The finite element method provides the following boundary conditions (Finlayson, 1992)  

Equation (10.32) is for the normal velocity or normal force, and Eq. (10.33) is for the tangential velocity or tangential force. The normal and tangent to the surface are determined by the geometry. The quantities u , f , u, and ft must be specified, but can be zero. These quantities represent the interaction between the system and its suiToundings. The boundary conditions available in EEMLAB are listed in Table 10.3. At any given boundary, one 

TABLE 10.3. Boundary Conditions for the Navier-Stokes Equation 

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