Possible to create laminar flow in fast moving air?

AI Thread Summary
Creating nearly laminar flow in a tube with a rectangular cross-section at air speeds of 100 to 150 m/sec is challenging due to high turbulence potential. Initial calculations suggested a Reynolds number of 7000, indicating possible laminar flow, but later corrections revealed a much higher Reynolds number of 260,000, making sustained laminar flow unlikely. While laminar flow may occur briefly near the entrance of the tube, the distance it can be maintained is limited. The discussion highlights the difficulty of achieving laminar flow in such conditions and suggests exploring methods like using a sheaf of soda straws to potentially stabilize it. Ultimately, sustained laminar flow in this scenario is considered improbable.
Swamp Thing
Insights Author
Messages
1,028
Reaction score
763
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?
 
Engineering news on Phys.org
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.
 
Reply
  • Like
Likes Swamp Thing and Chestermiller

Thread 'Query on Isentropic relationships (such as PV^gamma = constant)'

Hi all, I have a question. So from the derivation of the Isentropic process relationship PV^gamma = constant, there is a step dW = PdV, which can only be said for quasi-equilibrium (or reversible) processes. As such I believe PV^gamma = constant (and the family of equations) should not be applicable to just adiabatic processes? Ie, it should be applicable only for adiabatic + reversible = isentropic processes? However, I've seen couple of online notes/books, and...
View full post »
Thread 'How can I find the cleanout for my building drain?'

Thread 'How can I find the cleanout for my building drain?'

I am a long distance truck driver, but I recently completed a plumbing program with Stratford Career Institute. In the chapter of my textbook Repairing DWV Systems, the author says that if there is a clog in the building drain, one can clear out the clog by using a snake augur or maybe some other type of tool into the cleanout for the building drain. The author said that the cleanout for the building drain is usually near the stack. I live in a duplex townhouse. Just out of curiosity, I...
View full post »

Thread 'Dry sump pump issue'

I have an engine that uses a dry sump oiling system. The oil collection pan has three AN fittings to use for scavenging. Two of the fittings are approximately on the same level, the third is about 1/2 to 3/4 inch higher than the other two. The system ran for years with no problem using a three stage pump (one pressure and two scavenge stages). The two scavenge stages were connected at times to any two of the three AN fittings on the tank. Recently I tried an upgrade to a four stage pump...
View full post »

Similar threads

B Beam of air: Extending the range of a fan
Replies
17
Views
3K
A fun, engaging and visual way of showing laminar flow for young kids
Replies
1
Views
2K
Two-Phase Pressure Drop (I need an expert)
Replies
0
Views
1K
I Centrifugal separation into hot & cold air streams?
Replies
1
Views
2K
Laminar to turbulent flow transition?
Replies
5
Views
3K
I Laminar-turbulent transition and Reynolds number
Replies
5
Views
2K
How Do You Calculate Pressure and Flow for an Air Float Conveyor?
Replies
3
Views
1K
Modelling Heat Transfer for Pulsating Laminar Duct Flow
Replies
20
Views
2K
I Graduation of air flow inside a vacuum chamber
Replies
4
Views
2K
Bernoulli vs Newton - air flow characteristics
Replies
7
Views
5K

Hot Threads

Recent Insights

Back
Top