What is the Formula for Calculating Gravity Flow Rate of Water in a Can?

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Discussion Overview

The discussion revolves around calculating the gravity flow rate of water from a can, specifically focusing on the speed of water as it exits the can and the factors influencing this speed. Participants explore theoretical and practical aspects of fluid dynamics, including the application of Bernoulli's principle and the effects of gravity and air resistance.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • Doug seeks to calculate the flow rate of water from a can, asking about the speed of water drops and the factors affecting it.
  • Some participants suggest using calculus to determine the speed based on the height from which the water falls.
  • Factors mentioned that could affect the speed include the acceleration due to gravity (9.8 m/s²) and air resistance.
  • One participant proposes that the speed of the outflow is proportional to the square root of the height of the liquid in the can, referencing Bernoulli's equation: v_{out} = √(2gh).
  • Another participant provides a rough estimate of the time it takes for a drop to reach the ground and calculates an average speed based on distance and time, though expresses uncertainty about the accuracy of this calculation.
  • A later post introduces a different scenario involving a larger adhesive tank and asks how to calculate the gravity flow rate and pipe angle, indicating a broader interest in fluid dynamics beyond the initial can scenario.

Areas of Agreement / Disagreement

Participants express various viewpoints on the factors affecting flow rate and speed, with no clear consensus on the best approach or formula to use. Some calculations and principles are proposed, but uncertainty remains regarding their accuracy and applicability.

Contextual Notes

Some assumptions are not explicitly stated, such as the effects of pipe diameter and fluid viscosity, which may influence the flow rate. The discussion also does not resolve how to account for these factors in the calculations.

Who May Find This Useful

This discussion may be useful for individuals interested in fluid dynamics, engineering applications involving gravity flow, or those seeking to understand the principles behind calculating flow rates in practical scenarios.

dug_rose
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Hi !

I need to find the rate of flow of water coming out of the bottom of a can, under gravity to put in the equation:

r. of f. = speed x area

How do I calculate the speed of which the water drops, taking into account height etc.

Many thanks,

Doug :smile:
 
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dug_rose said:
How do I calculate the speed of which the water drops, taking into account height etc.

Many thanks,

Doug :smile:

For that part you would need to use calculus i think. Give me the height of where the water drop starts to fall and i'll reply back.
 
hover said:
For that part you would need to use calculus i think. Give me the height of where the water drop starts to fall and i'll reply back.

Hi,

To give you a bit of background we need to drain a can of beer from the bottom of a can into a glass , 25 cm below. What factors effect the speed in which the liquid will drop so I can find the speed and use it to find the flow rate? The can will be on the edge of a table, so 125 cm high say. We are using a 440ml can if that makes any difference, through a machined mild steel pipe. I assuming 9.81 will be a mulitplier somewhere in there?

Thanks for any help you can give me, Doug
 
dug_rose said:
Hi,

To give you a bit of background we need to drain a can of beer from the bottom of a can into a glass , 25 cm below. What factors effect the speed in which the liquid will drop so I can find the speed and use it to find the flow rate? The can will be on the edge of a table, so 125 cm high say. We are using a 440ml can if that makes any difference, through a machined mild steel pipe. I assuming 9.81 will be a mulitplier somewhere in there?

Thanks for any help you can give me, Doug


The factors that will affect the speed the drop falls is the acceleration of gravity (9.8m/s) and air resistance.
 
Thanks a lot for your help hover
 
It will take about half a second for a drop to reach the ground. Using distance/time you will get the average speed of the fall. So 125/.5= 250cm/sec if i am correct. Although i got a answer i don't know if it is totally correct.

hope this helps
 
dug: the speed with which the beer starts to flow out the opening in the bottom is proportional to the square root of the level of beer in the can. So, it flows out fastest when the can is full, and the flow rate falls to zero, as the can empties.

A reasonable approximation to the mean outflow speed is given by an application of Bernoulli:

[tex]v_{out} = \sqrt{2gh}[/tex]
g : acceleration due to gravity = 9.8m/s2
h : beer level in can, in meters (some number from 0 to about 0.15m, for a typical can)

It's just one step further to calculate the time it takes to drain the can, for a given hole size.
 
Hi, how are you?

Actually i have something to ask also.

I have a adhesive tank 1250kg ( dimension: 1400mm x 1100mm x 900mm) connect to a 11/2"

stainless steel pipe flow to another tank. So, may i know how to calculate the gravity flow

rate at maximum & minimum fluid level and also what is the pipe angle?

Thank you
 

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