modelDynamicPressureOutflow
Extends from Interfaces.SISOFlow.
Information
This outflow boundary is supposed to end an area of the model where dynamic pressure is taken into account. The area is started with DynamicPressureInflows.
Components that take dynamic pressure into account (marked with green symbols) should only be used in areas surrounded by DynamicPressureInflows and DynamicPressureOutflows.
The components output velocity can be set to a fixed value or given by a signal. From the inflow velocity, that is computed by the area of the component, the flow is decelerated to the reference outflow velocity. The sign of the velocity is defined to match the sign of the mass-flow rate at the inlet.
The pressure difference resulting from the velocity difference is based on the total pressure balance, implicitly assuming a nozzle/diffusor of suitable area ratio. When the sign of the velocity does not match the sign of the mass-flow rate, this assumption cannot be upheld. The model then extrapolates the dynamic pressure difference in order to maintain a stable and well-natured behavior but its validity is lost.
The area can be set to a fixed value or given by a signal, representing a variable-area outlet.
By default, the density is assumed to be constant across the component and only the inlet density is used for the calculation of the velocity. This assumption can be reverted by setting assumeConstantDensity = false. This will lead to a non-linear equation system of size 1, as the outlet velocity is calculated based on the outlet density.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Boolean | assumeConstantDensity | true | = true, if incompressibility is assumed (use '= false' for Ma > 0.3) |
| Boolean | displayA | displayParameters and displayInletArea and not areaFromInput | |
| Boolean | dv_out | displayParameters and displayOutletVelocity and not velocityFromInput | |
| String | compressibilityString | if assumeConstantDensity then "incompressible" else "compressible" | |
| String | displayPos1 | if displayCompressibilityApproach then compressibilityString elseif displayA then "A_in = %A_par" elseif displayInertance then "L = %L" else "" | |
| String | displayPos2 | if displayCompressibilityApproach and displayA then "A_in = %A_par" elseif displayInertance and not displayPos1 == "L = %L" then "L = %L" else "" | |
| String | displayPos3 | if displayCompressibilityApproach and displayA and displayInertance then "L = %L" else "" | |
| Nozzle / Diffusor definition | |||
| Boolean | areaFromInput | false | = true, if input connector for inlet cross section area is enabled |
| SI.Area | A_par | 1 | Inlet cross-section area |
| Boolean | velocityFromInput | false | = true, if input connector for outlet velocity is enabled |
| SI.Velocity | v_out_par | 0 | Outlet velocity set value |
| Advanced › Regularization | |||
| Boolean | extrapolateQuadratic | false | = true, if extrapolating negative velocities purely quadratic |
| SI.MassFlowRate | m_flow_reg | dropOfCommons.m_flow_reg | Regularization threshold of mass flow rate |
| Layout › Display parameters | |||
| Boolean | displayCompressibilityApproach | true | = true, if assumeConstantDensity is displayed |
| Boolean | displayInletArea | true | = true, if inlet cross section area A_par is displayed |
| Boolean | displayOutletVelocity | true | = true, if outlet velocity v_out_par is displayed |
| Boolean | displayInertance | false | = true, if inertance L is displayed |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Blocks.Interfaces.RealInput | A_var | Inlet cross section area input connector [m2] | |
| Modelica.Blocks.Interfaces.RealInput | v_out_var | Outlet velocity input connector [m/s] |