多孔跳跃边界条件.docx

Porous Jump Boundary ConditionsPorous jump conditions are used to model a thin membrane that has known velocity (pressure-drop) characteristics. It is essentially a 1D simplification of the porous media model available for cell zones. Examples of uses for the porous jump condition include modeling pressure drops through screens and filters, and modeling radiators when you are not concerned with heat transfer. This simpler model should be used whenever possible (instead of the full porous media model) because it is more robust and yields better convergence.The thin porous medium has a finite thickness over which the pressure change is defined as a combination of Darcys Law and an additional inertial loss term:(7.22-1)whereis the laminar fluid viscosity,is the permeability of the medium,is the pressure-jump coefficient,is the velocity normal to the porous face, andis the thickness of the medium. Appropriate values forandcan be calculated using the techniques described in Section7.19.6.User Inputs for the Porous Jump ModelOnce the porous jump zone has been identified (in theBoundary Conditionspanel), you will set all modeling inputs for the porous jump in thePorous Jumppanel(Figure7.22.1), which is opened from theBoundary Conditionspanel(as described in Section7.1.4).Figure 7.22.1:ThePorous JumpPanelThe inputs required for the porous jump model are as follows:1. Identify the porous-jump zone.2. Set theFace Permeabilityof the medium (in Equation7.22-1).3. Set thePorous Medium Thickness().4. Set thePressure-Jump Coefficient().5. Define the discrete phase boundary condition for the porous jump (for discrete phase calculations).Identifying the Porous Jump ZoneSince the porous jump model is a 1D simplification of the porous media model, the porous-jump zone must be modeled as the interface between cells, rather than a cell zone. Thus the porous-jump zone is a type of internal face zone (where the faces are line segments in 2D or triangles/quadrilaterals in 3D). If the porous-jump zone is not identified as such by default when you read in the grid (i.e., if it is identified as another type of internal face zone), you can use theBoundary Conditionspanelto change the appropriate face zone to aporous-jumpzone.DefineBoundary Conditions.The procedure for changing a zones type is described in Section7.1.3. Once the zone has been changed to a porous jump, you can open thePorous Jumppanel(as described in Section7.1.4) and specify the porous jump parameters listed above.Defining Discrete Phase Boundary Conditions for the Porous JumpIf you are modeling a discrete phase of particles, you can set the fate of particle trajectories at the porous jump. See Section22.13for details.Postprocessing for th