# Possible to create laminar flow in fast moving air?

• Swamp Thing
In summary, the conversation is discussing the possibility of creating laminar flow in a tube with a rectangular cross section of 1 cm by 5 cm, with air moving at a speed of 100 to 150 m/sec. There is a concern that turbulence may set in, but the main question is if the laminar flow can be sustained for a distance of 20 cm. The initial Reynolds number was calculated to be around 7000, but it was later discovered that the actual number is closer to 260,000, making it unlikely for the laminar flow to be achieved. Both parties agree that it may still be possible for a small distance near the entrance of the tube.

#### Swamp Thing

Is it possible to create (nearly?) laminar flow in a tube with rectangular C.S. , around 1 cm X 5 cm , with air moving at around 100 to 150 m/sec?

Turbulence will likely set in sooner or later, but can the laminar flow be made to last over say 20 cm?

Swamp Thing said:
Is it possible to create (nearly?) laminar flow in a tube with rectangular C.S. , around 1 cm X 5 cm , with air moving at around 100 to 150 m/sec?

Turbulence will likely set in sooner or later, but can the laminar flow be made to last over say 20 cm?
What is your assessment of this so far?

When I posted, I had got a Reynolds number around 7000. So I was wondering if it would work if we used a sheaf of soda straws or something to laminarize the flow.

But I have since found errors in my calculation -- the RN is actually like 260,000. So it's probably not doable, I'm thinking.

Swamp Thing said:
When I posted, I had got a Reynolds number around 7000. So I was wondering if it would work if we used a sheaf of soda straws or something to laminarize the flow.

But I have since found errors in my calculation -- the RN is actually like 260,000. So it's probably not doable, I'm thinking.
I agree.

It will still be laminar over some small distance near the entrance. The question is how small.

Swamp Thing and Chestermiller