||Select a Boundary Type for the 2D Boundary polyline. Boundary type effects what happens to the flow when it reaches the boundary. Note: If it is not clear what happens at the boundary then Critical Condition type is recommended.
Available types are:
- Vertical Wall – The boundary line is considered to be an impermeable infinitely high barrier. Water cannot flow out of, or into, the 2D Polygon across the boundary line.
- Critical Condition – At the boundary line, if the level in the boundary element of the 2D Polygon is above the boundary face level, flow out of the 2D Polygon will be calculated using a broad crested weir equation without energy loss. If the level in the boundary element is below the boundary face level, the boundary is considered to be a vertical impervious wall. Water cannot flow into the 2D Polygon across the boundary line.
- Supercritical Condition – At the boundary line, if the flow in the boundary element is supercritical (Froude > 1) and directed outside of the 2D Polygon, then the flow at the boundary face will be considered supercritical and calculated using the boundary element depth and velocity, regardless of the boundary face level. If the conditions of the flow are not supercritical, or the flow is going into the 2D Polygon, the boundary face will be considered as a vertical wall. This situation is useful in areas where the user knows that the flow is flowing out of the 2D Polygon without any effects on the 2D Polygon. Water cannot flow into the 2D Polygon across the boundary line.
- Dry – The boundary line is considered to be bordered by a bottomless pit. Water that reaches the edge of the boundary line will flow out of the 2D Simulation polygon and will be lost from the simulation. Water cannot flow into the 2D Polygon across the boundary line.
- Normal Depth – It is assumed that slope balances friction forces (normal flow). Depth and velocity are kept constant when water reaches the boundary, so water can flow out without energy losses.
- Inflow – Inflow / Outflow to the 2D Simulation Polygon at the boundary line is defined by a profile in an Inflow Event. The inflow is distributed evenly by length along the length of the boundary line.
- Level – Depth of water at the boundary line is defined by a profile in a Level Event. If the level of water in the boundary is below the boundary element ground level, the water depth at the boundary is considered zero. Therefore the boundary acts as a weir with crest level at the level of the boundary element.
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