# determine if the flow is laminar or turbulent [closed]

what would be the the type of flow if the water flows through stainless steel channel? would it be a laminar flow or turbulent flow. I assume the adhesive force of water to stainless steel is minimum.

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– Wasabi
Aug 24, 2020 at 22:09

The wall material does not effect the nature of the flow. The only material effect on flow will be roughness; but smooth steel is indistinguishable from smooth glass or anything else smooth making up the channel walls as far as the fluid is concerned. Whatever the material, the molecules next to the wall will always adhere to it, with the flow getting faster and faster as you get further from the wall of the channel. Laminar or turbulent flow in steady state is a function of the Reynolds number, which is a dimensionless number.

Wikipedia (https://en.wikipedia.org/wiki/Reynolds_number#Flow_in_a_pipe) has a pretty comprehensive summary of the Reynolds number. In a pipe or channel its a function of Velocity and channel size and an inverse function of viscosity ('thickness' of the fluid)

• Reynolds number requires fluid velocity and diameter of the channel. what if it's an open channel and the velocity is unknown. Would it be possible to determine type of flow in this case? Aug 24, 2020 at 18:42
• @Physical yes, look up hydraulic diameter. Aug 24, 2020 at 19:38
• @Physical The flow type depends on the velocity (which is one of the quantities used to calculate Reynolds number). It should be fairly obvious that for an open channel say 100mm wide, the flow pattern will not be the same for velocities of say 1mm/s and 100m/s. Aug 24, 2020 at 20:43

Building on the previous answer, you can use the Reynolds number to calculate at what point the flow will transition from laminar to turbulent. Copied from Wikipedia “ For flow in a pipe of diameter D, experimental observations show that for "fully developed" flow, laminar flow occurs when Re < 2300 and turbulent flow occurs when Re > 2900. A lot of other websites and papers support this range though.

1. Laminar flow – R < 2000 2. Critical flow – R > 2000 and R < 4000 3. Turbulent flow – R > 4000

The flow in between will begin to transition from laminar to turbulent and then back to laminar at irregular intervals, called intermittent flow.” Source: Wikipedia. If you know the diameter you can use different velocities to see what range it changes

• I don't know the velocity and diameter of the channel however the pressure is around 90psi and the cross-section of the channel around 15mm×20mm. Aug 25, 2020 at 1:01