Case study · CFD of pumping stations

CFD study of a pump suction manifold: Al Bedai tanks & pumping station

ANSYS Fluent study of the common suction manifold that feeds two pump groups from four storage tanks. It establishes how evenly the flow divides between the pump suction branches, a question one-dimensional network models cannot answer.

Client
Sharjah Electricity, Water & Gas Authority (SEWA)

Location
Al Bedai, UAE

Scope
Flow split between pump suction branches

Tools
ANSYS Fluent, steady-state RANS

Criteria
±10% flow distribution · suction velocity limits

1,579 kg/s

Total flow with six duty pumps

16.53–16.80%

Share per branch, against 16.67% for an even split

< 1%

Maximum departure from the mean

3 meshes

302k to 722k cells, under 0.08 points change

The challenge

Closely spaced branches on a large header

The pump branches come off a large-diameter header at close spacing, and the header is fed from both ends. Losses at each take-off depend on local flow separation, so a 1D network model cannot predict how evenly the flow divides. An uneven split would push some pumps away from their best efficiency point.

Suction manifold geometry from the issued piping arrangement

Our approach

CFD methodology

3D model of the manifold built from the issued piping arrangement
Steady-state simulation for six duty pumps, and for five duty pumps with one branch closed
Mass flow computed at each suction branch and compared with a uniform split
Mesh sensitivity on three meshes from about 302,000 to 722,000 cells
Branch velocities checked against customary suction piping limits

CFD mesh of the suction manifold — Computational mesh at a branch take-off

Results

Key results

Pathlines coloured by velocity through the manifold — Pathlines through the manifold, coloured by velocity

Key findings

With six duty pumps, each branch takes 16.53–16.80% of the flow against 16.67% for an even split, a maximum departure of 0.8%.
With five pumps in service, the maximum departure is 0.85%, so the uniformity does not depend on a symmetric duty.
The branches are small compared with the header, so branch resistance, not position along the header, governs the split.
Results are mesh-independent: shares change by less than 0.08 percentage points across three meshes.
Branch velocities of 1.32–1.67 m/s are within suction limits. No change to the manifold is needed. Stagnant standby legs should be covered in the operating philosophy for water age.

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