CFD-Pre format

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CFD-Pre format

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The CFD-Pre format is an XML-based definition that describes the geometry, boundary conditions, and fluid parameters for a turbomachinery CFD simulation. The file is structured in logical blocks. Each is described below with an example.The CFD-Pre XML format allows full definition of the computational domain required for turbomachinery CFD. Each section is designed to support the import into meshing or solver tools and ensure simulation fidelity based on user-defined inputs.

The file contains the following blocks:

ProjectData

Contains global settings for the CFD model, including type of machine and reference flow properties.

ProjectType

Project type. Possible values are:
• Pump: for pumps
• Vent: for fans
• Comp: for compressors
• GasTurb: for gas turbines
• HydTurb: for hydraulic turbines

MassFlow

Mass flow specified in the design point.

RotationAxis

Vector defining the rotation axis.

Periodicity

Indicates if the exported geometry is 360° or a segment.

 

<ProjectData Type="Object">

 <ProjectType Type="Enum">Comp</ProjectType>

 <MassFlow Type="Float">0.198989461073871</MassFlow>

 <RotationAxis Type="Vector3">

         <x Type="Float">0</x>

         <y Type="Float">0</y>

         <z Type="Float">1</z>

 </RotationAxis>

 <Periodicity Type="Enum">Full 360°</Periodicity>

</ProjectData>

FluidData

Defines the fluid’s thermophysical properties and model assumptions in compressible cases.

Incompressible case example:

<FluidData Type="Object">

 <IsCompressible Type="Boolean">False</IsCompressible>

 <IsLiquid Type="Boolean">True</IsLiquid>

 <Density Type="Float">998.2</Density>

 <DynamicViscosity Type="Float">0.0009982</DynamicViscosity>

 <SpecificHeat Type="Float">4182</SpecificHeat>

 <ThermalConductivity Type="Float">0.556</ThermalConductivity>

 <VaporPressure Type="Float">2340</VaporPressure>

 <GasMassFraction Type="Float">1.5E-5</GasMassFraction>

</FluidData>

Compressible case example:

<FluidData Type="Object">

 <IsCompressible Type="Boolean">True</IsCompressible>

 <IsLiquid Type="Boolean">False</IsLiquid>

 <DynamicViscosity Type="Float">0.000118677951603912</DynamicViscosity>

 <MolarMass Type="Float">102.01794601227</MolarMass>

 <SpecificHeat Type="Float">800</SpecificHeat>

 <ThermalConductivity Type="Float">0.01339</ThermalConductivity>

 <GasConstant Type="Float">81.5</GasConstant>

 <GasModel Type="Enum">Perfect</GasModel>

</FluidData>

Please refer to compressible fluids for more information about available fluid models.

FluidZone

This block is written for all CFturbo components.

Caption

Indicates the name used for this solid body within the geometry file.

Geometry

Geometry file name.

Frame

Rotating or static.

Rotation axis

For rotating zones, vector defining the rotation axis.

Origin

For rotating zones, vector defining the origin of the coordinates system.

Component type

Component type in CFturbo. The following values are possible:
• RadialImp: radial impeller
• AxialImp: axial impeller
• Stator: stator
• VoluteIn: inlet volute
• VoluteOut: outlet volute

The example of a rotating component zone for an impeller:

<FluidZone Type="Object">

 <Caption>NS_Impeller</Caption>

 <Geometry>CC pi1.6 (R134a)_Co2.stp</Geometry>

 <Frame Type="Enum">Rotating</Frame>

 <RotationalSpeed Type="Float">-833.333333333333</RotationalSpeed>

 <RotationAxis Type="Vector3">

         <x Type="Float">0</x>

         <y Type="Float">0</y>

         <z Type="Float">1</z>

 </RotationAxis>

 <Origin Type="Vector3">

         <x Type="Float">0</x>

         <y Type="Float">0</y>

         <z Type="Float">0</z>

 </Origin>

 <ComponentType Type="Enum">RadialImp</ComponentType>

 <Inflow>

         <Boundary>

                 <Geometry>NS_Impeller_FlowDomain_Inflow</Geometry>

         </Boundary>

 </Inflow>

 <StaticWalls>

         <Boundary>

                 <Geometry>NS_Impeller_FlowDomain_CasingShroud</Geometry>

         </Boundary>

 </StaticWalls>

 <RotatingWalls>

         <Boundary><Geometry>NS_Impeller_FlowDomain_Hub</Geometry></Boundary>

         <Boundary><Geometry>NS_Impeller_FlowDomain_BladeSS</Geometry></Boundary>

         <Boundary><Geometry>NS_Impeller_FlowDomain_BladePS</Geometry></Boundary>

 </RotatingWalls>

 <Outflow>

         <Boundary>

                 <Geometry>NS_Impeller_FlowDomain_Outflow</Geometry>

         </Boundary>

 </Outflow>

</FluidZone>

Also it contains information of all boundaries available for the component. Four different boundary types are possible:

•Inflow

•Outflow

•StaticWalls

•RotatingWalls

Each boundary block contains a list of boundaries with information about the geometry name used within the geometry file.
For the global inlet and outlet (i.e., the inlet of the first component and the outlet of the last one considering the order of the components in flow direction), boundary conditions such as pressure, temperature, and flow rate are written too.

Example of an outflow boundary condition:

<Outflow Type="Object">

 <Boundary Type="Object">

         <Geometry>NS_VoluteExtension_CFD_FlowDomain_Outflow</Geometry>

         <Conditions Type="Object">

                 <VolumetricFlow Type="Float">0.00957486583497985</VolumetricFlow>

                 <Pressure Type="Float">515867.356357303</Pressure>

                 <TotalPressure Type="Float">518385.444610908</TotalPressure>

                 <Temperature Type="Float">304.567150188904</Temperature>

                 <TotalTemperature Type="Float">304.718274210172</TotalTemperature>

         </Conditions>

 </Boundary>

</Outflow>