Pressure Inlet-Outlet Velocity - Boundary Condition Description
Pressure Inlet-Outlet Velocity is designed to provide a velocity boundary condition to boundaries where only the pressure is specified. It can be used for both inlet and outlet conditions. Depending on local flow condition velocity is either estimated and enforced to maintain mass balance (inflow) or value is copied from interior results (outflow) by applying a Zero Gradient condition.
Pressure Inlet-Outlet Velocity - Boundary Condition Understanding Pressure Inlet-Outlet Velocity
When used at the inlet the Pressure Inlet-Outlet Velocity boundary condition determines the velocity at a boundary cell face based on the mass flux of neighboring cells estimated in previous iteration and pressure equation. The velocity is calculated based on the flux through the boundary according to equation:
\(\vec U_{p} = \vec n \frac{\phi}{A}\)
where:
\(\vec U_{p}\) - velocity vector at the boundary
\(\vec n\) - face normal vector
\(\phi\) - face flux
\(A\) - local cell face area
For the outlet boundary, the condition is extended by assuming Zero Gradient. This condition effectively transfers results from interior to the boundary, ensuring smooth velocity continuity.
Pressure Inlet-Outlet Velocity is designed to handle both inlet and outlet flow conditions based on pressure. In real-world scenarios, there are situations where you don’t have a fixed velocity inlet or a pressure outlet, but rather a boundary where flow can either come in or go out based on the pressure conditions in the domain. For instance, consider a room with a door. If the pressure outside the room is higher, air will flow into the room.
Pressure Inlet-Outlet Velocity - Boundary Condition Application & Physical Interpretation
Pressure Inlet-Outlet Velocity is tailored for boundaries where the flow direction and speed are uncertain and are regulated by the pressure difference across the boundary.
Pressure Inlet-Outlet Velocity in Heat Transfer
Example applications: HVAC, room temperature distribution
This problem can be addressed using the buoyantSimpleFoam solver. In ventilation-related problems, understanding the temperature distribution is often crucial. The flow is driven either by setting a constant velocity at the inlet (or specifying a mass/volumetric flow rate) or by the pressure difference (Total Pressure). In such cases, Pressure Inlet-Outlet Velocity is applied at the outlet to adjust the flow according to the main driving factor and to stabilize the calculations.
| Physics | Pressure | Velocity | Temperature |
|---|---|---|---|
Inlet | Fixed Flux Pressure | Fixed Value | Fixed Value |
Outlet (wind tunnel) | prghPressure | Pressure Inlet-Outlet Velocity | Zero Gradient |
Pressure Inlet-Outlet Velocity in channel flow applications
Example applications: channel flows, T-junction flows
This problem can be tackled using the pimpleFoam solver. In channel flows, the flow is generally driven by a pressure difference. The Total Pressure is specified at the inlet, requiring the velocity to adjust accordingly.
| Physics | Pressure | Velocity |
|---|---|---|
Inlet | Total Pressure | Pressure Inlet-Outlet Velocity |
Outlet | Fixed Value | Inlet-Outlet |
Pressure Inlet-Outlet Velocity in open-boundary flows (multiphase) applications
Example applications: dam break, river flows
Pressure Inlet-Outlet Velocity is often used as a so-called open boundary. Because of its unique properties to adjust and work both as the velocity inlet or Zero Gradient.
| Physics | Pressure | Velocity |
|---|---|---|
Atmosphere (open boundary) | Calculated | Pressure Inlet-Outlet Velocity |
Pressure Inlet-Outlet Velocity - Boundary Condition Pressure Inlet-Outlet Velocity in SimFlow
To define Pressure Inlet-Outlet Velocity condition on the patch, the proper option must be selected from the drop-down menu in Boundary Conditions tab - Figure 1
Pressure Inlet-Outlet Velocity - Boundary Condition Pressure Inlet-Outlet Velocity - Alternatives
In this section, we propose boundary conditions that are alternative to Pressure Inlet-Outlet Velocity. While they may fulfill similar purposes, they might be better suited for a specific application and provide a better approximation of physical world conditions.
| Boundary Condition | Description |
|---|---|
Pressure Directed Inlet-Outlet Velocity | works similarily to Pressure Inlet-Outlet Velocity, but allows defining a direction other than normal to the patch |
Pressure Normal Inlet-Outlet Velocity | similar definition to Pressure Inlet-Outlet Velocity, but the flow occurs in the direction normal to the boundary face |