Chemical Engineering - Fluid Mechanics - Discussion

2. 

Laminar flow of a Newtonion fluid ceases to exist, when the Reynolds number exceeds

[A]. 4000
[B]. 2100
[C]. 1500
[D]. 3000

Answer: Option B

Explanation:

No answer description available for this question.

Niki said: (Jun 7, 2012)  
For laminar flow, Re should be equal to or less than 2100.

Vishwas said: (Jun 28, 2012)  
Laminar flow is less than or equal to 2100.

Chitta said: (Aug 16, 2012)  
The above question doesn't mention about the system.
we have two type of value for laminar.

1. for circular pipe----- Re<= 2100
2. for flat plate ------- Re<= 5*10^5

B.Nath said: (Dec 8, 2012)  
For flow in a conduit:
Re<2100 Laminar Flow, Sheer Stress depends on viscosity but not on density.
2100<Re<4000 : Transient Flow
Re>4000 Turbulent flow depends on density.

Jyoti said: (Mar 22, 2013)  
This is true only in case of flow through pipes. we cannot generalize this for every case. Re num is different for every case.

Kalaivani said: (Aug 7, 2013)  
For Laminar flow, Reynold's number is less than or equal to 1(Re <= 1).

Dhruvin Virani said: (Sep 17, 2013)  
Laminar flow is less than or equal to 2100. And Re>4000 Turbulent flow.

Jayamsuba said: (Jul 24, 2014)  
For open channel flow,

If Re <500 or 600. laminar
> 2000 or 2100. turbulent.
Here, Re=rho*v*R/mu...R=hydraulic gradient.

For circular pipe flow,

If Re <2000. laminar.
> 4000. turbulent.
Here, Re=rho*v*d/mu...d=dia of pipe.

Here both formulae are important to keep in mind. because sometime this may confuse you.

Khawal said: (Sep 13, 2014)  
Laminar flow is in linear motion and having re less than 2100, after increase the re the turbulence is so that velocity increase.

Rajisha said: (Dec 26, 2014)  
Re below 2100 is laminar flow in case of circular pipes.

Surya Teja said: (Sep 14, 2016)  
Let is assume the question is for circular pipe based on options given. But, the question is when will the Laminar flow cease? I think, once the fully turbulent flow is achieved, which is after crossing Re 4000. Then only we can say there is no laminar flow.

Mahone said: (Apr 19, 2017)  
For circular pipes, the Reynolds number is used to classify flows as follows.

<2000 laminar flow.
2000-4000. Transitional flow.
>4000 turbulent flow.

Sanjeev Gupta said: (Oct 19, 2019)  
Laminar flow equal and less than 2100 Reynolds number.

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