Cut-water

Ü Volute | Cut-water

The geometry of the cut-water can be designed in this dialog box.

cutwater_dlg

Generally, the cut-water can be designed in two modes: Simple or Fillet.

Simple

The simple cut-water is a rounding-off between spiral and diffuser.

cutwater_mode_simple

The rounding is defined by the angular position φC,0 (0°=start of volute). Underneath, the minimum necessary angular position is displayed to prevent overlap of the actual volute and the diffuser.

CW_simple_radialOffset

Additionally, the diffuser can be shifted in radial direction by the radial offset ΔrC to reduce the intersection of spiral and diffuser. This radial offset corresponds to the cut-water thickness.

cutwater_simple_SidePos3D

Side position defines the transition position from the central rounding surface to the side surfaces. The created edge can be rounded optionally (Round edges).

cutwater_simple_SidePos

The cut-water itself is designed by a 4th order Bezier spline. The shape can be modified interactively after zooming in (Zoom Cut-water).

Fillet

For fillet cut-water design the spiral and the diffuser are trimmed and rounded at their intersection curve.

cutwater_mode_fillet

The corresponding fillet radius can be specified.

Additionally, the Diffuser base form factor defines the rounded shape of the first diffuser cross section on its base side and is between 0.2 and 1:

0 = cornered base side (like spiral section)

1 = full rounded base side

The factor affects the shape of the intersection curve and therefore the shape of the cut-water.

cutwater_fillet_base cutwater_fillet_auto

Starting from the Spiral start position the intersection of spiral and diffuser is calculated.

This angular position has to be at least 1° and lower than the intersection position of spiral and diffuser. Automatic activates an automatic determination of the optimal angular position.

If a fillet cut-water has been chosen, the 3D-model is set to the model state "Solids only" after every update of the design because only then the spiral and diffuser surface that are trimmed according to the fillet are visible.

CW_fillet

Limitations

Simple	For cornered spiral cross sections the side position is fixed to the corner position and cannot be modified individually.
Simple	Radial offset is available for strictly external volutes with 360° wrap angle only.
Fillet	Fillet cut-water is not available for cornered cross sections, either spiral or diffuser.
	Fillet cut-water is available for symmetric spiral cross sections only.
	Fillet cut-water is usually not possible, if the spiral development is at the beginning very flat and a tangential diffuser with a big end cross-section is chosen.

Cut-water design is not available for internal volutes.

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