# Chemical Engineering - Fluid Mechanics - Discussion

Discussion Forum : Fluid Mechanics - Section 1 (Q.No. 2)

2.

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

Discussion:

14 comments Page 1 of 2.
JayaMsuba said:
10 years ago

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.

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.

Surya Teja said:
8 years ago

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.

B.Nath said:
1 decade ago

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.

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.

Chitta said:
1 decade ago

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

we have two type of value for laminar.

1. for circular pipe----- Re<= 2100

2. for flat plate ------- Re<= 5*10^5

Mahone said:
7 years ago

For circular pipes, the Reynolds number is used to classify flows as follows.

<2000 laminar flow.

2000-4000. Transitional flow.

>4000 turbulent flow.

<2000 laminar flow.

2000-4000. Transitional flow.

>4000 turbulent flow.

(4)

Khawal said:
10 years ago

Laminar flow is in linear motion and having re less than 2100, after increase the re the turbulence is so that velocity increase.

Jyoti said:
1 decade ago

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:
1 decade ago

For Laminar flow, Reynold's number is less than or equal to 1(Re <= 1).

Dhruvin virani said:
1 decade ago

Laminar flow is less than or equal to 2100. And Re>4000 Turbulent flow.

Mishree lal said:
4 years ago

For laminor flow Reynolds number is equal or less than 2100.

(1)

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