# Principles of a Hookah

1. Feb 10, 2013

### sydfremmer

Dear Forum Users,

I know that when you suck in on the hose you create a pressure difference which pushes the air from one end, through the water, and into your mouth/lungs finally.

Can anybody help me making a mathematical description for this system?
Or tell me which equations I can use to describe the Hookah.

2. Feb 10, 2013

### Simon Bridge

That would be fluid-flow equations ... a detailed description would be very complicated: what do you need the model to be able to do?

3. Feb 11, 2013

### sydfremmer

I need to describe how hard to suck on the hose, in order to start bubles of smoke flowing through the water.

What are the basic principles behind that mechanism?

4. Feb 11, 2013

### Bobbywhy

The basic principle of operation is the person's lungs apply a suction (low pressure) on the system. The only opening of the system is underneath the combustible material. Air at atmospheric pressure will be drawn towards the lower pressure.

So, you "need to describe how hard to suck on the hose". I can help you. The answer is "Not really hard, but just medium hard." Sorry I cannot put any units of pressure (like pounds per square inch or pascals) onto the answer. It is unknowable from the information you've given in the diagram.

If I wanted to discover the exact answer I would use the scientific method: First propose how hard you think you will need to suck. Then experiment to find the actual suction force. You might, for example, experiment using different depths of liquid and note any differences. From your experimental data you may deduce your answer.

Cheers,
Bobbywhy

5. Feb 11, 2013

### sydfremmer

A very basic question. Can you explain in details why bubles of smoked are sucked through the water?
What are the forces causing this to happen?

6. Feb 11, 2013

### mrspeedybob

As a close approximation, the suction needed to initiate flow will be slightly greater then the depth of the tube in the water.

For example, if the end of the tube is 2 inches below the surface of the water then a vacuum of 2" of H2O will hold the smoke in equalibrium at the lower end of the tube. Any more then 2 inches of water vacuum will cause the smoke to flow.

You can convert inches of water into whatever units you like, that is just a unit conversion problem.

Calculating the amount of vacuum required to achieve a certain rate of flow is much more complicated.

7. Feb 11, 2013

### sydfremmer

Thank you,

But what do you mean by "water vacuum"?

8. Feb 11, 2013

### Simon Bridge

... since that is the volume of water that has to be displaced.

The actual suction needed depends on the dimensions of the hookah.

He's saying that you have to provide enough suction to pull more than 2" of water (in the example) into the pipe. You can work out what the pressure difference has to be to get to the threshold 2".

By cause-and-effect:
You suck on the mouthpiece.
This pulls air up the hose (see diagram),
which lowers the pressure in the water jar,
which raises the level of the water. Since the volume of water is a constant, this means water is drawn out of the body.

If the bowl was sealed off, then you'd be making a vacuum in the body ... but, in normal operation, the bowl has smoldering product in it which is porous, so, instead of a vacuum you get smokey air pulled down the body.

So, you need to suck on the mouthpeice hard enough to pull all the water out of the submerged part of the body (plus a bit). You can figure out how much that is from the dimensions of the hookah.

9. Feb 11, 2013

### Redbelly98

Staff Emeritus
By "2 inches of water vacuum", he means a vacuum that is 2 inches of water. That is to say, the air pressure inside the container must be lower (i.e. it's a partial vacuum) than the outside pressure by an amount equal to 2 inches of water.

The pressure difference in a 2 inch height of water is about 0.5% of atmospheric pressure.

(EDIT: Simon beat me.)

10. Feb 11, 2013

### wesbree

The bubbles are created by the air drawn in through the bowl at the top after it is combined with the heat, shisha, and smoke. As you draw air/smoke in through the mouthpiece, a vacuum is created in the cork/gasket-sealed base (notice the hose(s) connects to a manifold right where the body connects to the base) which draws air in from the top of the hookah via the tube submerged in the water. The vacuum is created by the user's lungs.

Think about if you blow into the mouthpiece rather than inhale. Some hookahs have valves where the base connects to the body that open to blow excess smoke out of the base. If you blow in the mouthpiece of a hookah without this valve, smoke will blow out of the top, and you could end up with water in your bowl