Definitions

This nomenclature is used at Post Mixing to describe flow patterns under turbulent conditions.

• U = axial up flow or up-pumping or up draft.  This is up the shaft and down the walls.
• D = axial down flow or down-pumping or down draft.  This is down the shaft and up the walls.
• R = radial flow.  This is a cylindrical jet spreading out from the impeller.  Some of it goes up the wall and some of it goes down the walls.
• 1 = extreme radial.  The flow is perpendicular to the shaft (tank axis)
• 3 = extreme axial.  The flow is generated by a hydrofoil of fluidfoil and is very axial
• 2 = mixed flow direction.  The flow has components of both axial and radial flows.

The determination of Proximity Factors requires knowledge of the flow or pumping direction of the impellers.

Examples

• D2:  Predominately axial down flow but has radial components.  The flow pattern spreads out below the impeller.  Pitched bladed turbine: 
  • PBT, P4, A200
• D3:  Highly axial flow pattern.  Hydrofoils, fluidfoils, and propellers: 
  • PR-D, AP-3, , HE-3, A100, A110, A310, A312, A320, A315, A6000
• R1:  Highly radial flow pattern. Turbines with disks:
  • RT, D-6, R100, RD, Holmes & Narver, R300, R320, RS6, CD-6, R130, Smith Turbine, RDC, BT-6, Bar Turbine, R510, Sawtooth, Disperser, R500
• R2:  Predominately radial flow pattern but has axial components.  Turbines and paddles without a disk.
  • RP, R200
• U2:  Predominately axial up flow but has radial components.
  • PBT-U
• U3:  Highly axial up-flow pattern. Up-pumpers:
  • PR-U, A340, A345