Flow Measurement · Glossary

What is Laminar Flow?

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Laminar flow is smooth flow in parallel layers with no mixing between them, found at low Reynolds numbers.

Laminar Flow Explained

In laminar flow each layer of fluid slides over the next. The velocity profile is a parabola, with the centre moving at twice the average velocity and the fluid at the wall almost still.

Laminar flow occurs with viscous fluids, small pipes or low velocities. Many meters lose accuracy here because their calibration assumes a turbulent profile. Laminar flow elements use it on purpose: pressure drop is then directly proportional to flow.

Laminar Flow Formula

v_avg = ½ v_max

v_avg	average velocity
v_max	centreline velocity

Example: If the centreline velocity is 0.4 m/s, the average velocity in fully developed laminar flow is 0.2 m/s.

Calculators for Laminar Flow

CalculatorReynolds Number CalculatorFree online calculator with formula and worked example.CalculatorLaminar Flow Element CalculatorFree online calculator with formula and worked example.

Frequently Asked Questions

What is Laminar Flow?

Laminar flow is smooth flow in parallel layers with no mixing between them, found at low Reynolds numbers.

Where does laminar flow occur in plants?

In viscous oils, syrups and polymers, in small sample and capillary lines, and at very low flow rates.

Is laminar flow bad for measurement?

Not always. Coriolis and positive displacement meters work well in laminar flow, and laminar flow elements rely on it. Vortex and some DP meters do not.