Geometric coupling

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Geometric coupling

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The sketch illustrates the general layout of the geometric coupling of two neighboring components in case they are coupled:

Primary / Secondary

In a group of two neighboring components that are coupled, one is primary always, the other one is secondary. The secondary side is aligned to the primary side. Only the secondary side can define an offset to the neighboring component.

If the geometry of the primary component is changing, the component at the secondary side is adjusted automatically. If a component is deactivated (see Active/ Rename/ Delete), no adjustment will be effected - therefore an overlapping of neighboring components is possible, which is illustrated by a warning (see Components). The same applies if neighboring components are not coupled.

Coupling definition

The coupling definition at volute inlet as well as at stator inlet and outlet is made in a uniform manner.




Information about coupling direction

Neighboring component's inlet/ outlet
Inlet/ outlet position at hub and shroud side

Coordinate transfer from neighboring component (if that is primary)

Inlet/ outlet
Geometry definition optionally by
- Points on Hub & Shroud
- Point on Center line, width and angle
Alternatively absolute coordinates or an Offset can be used, which are automatically converted into each other.


Rotor-Stator-Interface (RSI) at impeller outlet can be defined in the CFD-Setup of the impeller, otherwise it's located directly on the impeller outlet.

Flow direction (angle)

Beside the geometrical information the flow direction is an important property. The flow direction at the component inlet is defined by the flow direction at the outlet of the upstream component (predecessor). Outlet flow direction of a component is determined by its blade or by constant swirl for vaneless components.

The first component of the project has no predecessor and gets the flow direction information from pre-swirl definition in the Global setup.

Possible warnings


Possible solutions

Flow inlet does not match previous outlet
Flow outlet does not match next inlet

Inlet and outlet of flow region of two neighboring components are not matching.

Check both sides (components) if the hub and shroud points are identical and no gap between the components exists.

For stators, the "Inlet + Outlet" mode is more suitable to define exact geometry endpoints. For "Center line" specifications, one of the pre-defined angle definitions should be used if possible.

Please note that for volutes the inlet is always axis-parallel. An upstream stator can only match the volute inlet if its outlet is also axis-parallel.

For impellers, an existing gap of the flow region can alternatively be closed by

secondary flow path design in the meridional contour design step

extension (with option "connected") or RSI connection in the CFD setup