3 replies to this topic

[ayan_dg]

What is the significance of Froude number. what does it physically signify ? If it increases what happens and if it decreases what happens

For example Reynolds number is a measure of how strong the inertial forces are in respect to the viscous forces. A very high reynolds number means that inertial forces are actually governing the flow rather than viscous forces. I want the answer of my question in this line , please help.

[ankur2061]

Ayan,

I had prepared a standard titled 'Process Design Criteria' for a middle-east offshore O&G company where I have mentioned and elaborated on gravity line sizing. Froude number has been used in the context of gravity line sizing and specifically addressing vertical gravity lines. The section relates to dump caissons used for drain from off-shore O&G platforms. I am reproducing the section for the benefit of alll readers:

Vertical Lines
Vertical gravity lines with or without submerged outlets (e.g. so-called “dump caissons”) shall be designed such that the Froude number is less than 0.3 to avoid air entrainment and ensure undisturbed flow without pulsations.
Froude number = V / (D*g)^0.5
Where :
V is the velocity assuming full pipe in m/s
D is the pipe inner diameter in m
g is the gravity constant in m/s²

A vent line shall be included from top of the vertical gravity line to prevent vacuum, flashing or pulsations. The vent line should be designed for an air/vapor volumetric flow-rate equal to the liquid volumetric flow through the vertical line and a pressure loss of maximum 0.005 bar. The vent line for vertical lines/caissons to sea shall also be designed for the wave motion inside lines/caisson.

The liquid to the dump “caissons” should be tangential and sloped downwards.

Drainage of deluge water from drain boxes through vertical lines should be sized on basis of 50 % of the available head (assuming the pipe running full of liquid) and not Froude number.

Hope this helps you to understand the concept of Froude number better.

Regards,
Ankur.

[siretb]

THe froude number can be seen as a ratio between inertial forces and gravitational forces.

[ankur2061]

Ayan,

Check out the following links:

http://www.engineeri...mber-d_578.html

http://en.wikipedia....i/Froude_number

Should help you.

Regards,
Ankur.