Suction Vortex Suppression 1

[PuffJr]

I have seen some equations and tables to determine minimum static head for vortex suppression, but I think that they apply specifically to water. I am working with more viscous fluids. Is there a method to evaluate the effect of viscosity?

 

[chief]

To assist in preventing vortexing, place the suction away from the tank sidewalls and fit a x- piece at the suction opening.
Better practical elimination than theoretical calculations.

Offshore Engineering&Design

 

[ccfowler]

Vortex formation is most effectively supressed by gradual acceleration of the flow from the reservoir and having the greatest height of the fluid surface above the suction bell inlet. Assuming a clean fluid, the suction bell should be sufficiently large and symmetrically located so that there is minimal risk of any localized higher velocity regions in the flow at the entry into the suction bell.

A good arrangement for a practical suction bell is a relatively large flange (without any bolt holes) aligned parallel to and suitably close to the flat bottom of the reservoir. The flow accelerates gently as it flows radially inward toward the suction pipe. It is best for the flange to be very well and smoothly rounded at the outside diameter and for the pipe end to be well and smoothly rounded at the flange face. If possible, the suction pipe at the flange should be larger than the main suction line and then be stepped down using reducer fittings rather than bushings. Stacking concentric reducers vertically at the flange may be practical for gently accelerating the flow into the suction line.

It is also important to supress turbulence in the flow entering the reservoir. Any pipes feeding the reservoir should discharge well below the liquid surface and at minimum practical velocities. If necessary, baffles may help to keep turbulence away from the suction bell.

Obviously, you will have to make the best of the configuration constraints of your application.

My experience is mainly with water and similarly low viscosity fluids. Greater viscosity would tend to supress the persistence of vortices induced by the flow entering the reservoir.

 

[rcooper]

When I have been involved with scale models of pump intakes, we have scaled everything to maintain a Froude number identical to the full scale sump. This was to make the vortices act in a similar manner in the model as in the full scale sump.

So I would guess, you would re-scale the designs used for water to maintain an identical Froude nunber for the fluid of your choice.