When liquid is poured from a container (e.g. tea poured from one teacup to another), the liquid often slides along the side of the container, making a real mess.
What can be done to prevent this?
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That's very resonable but I don't know why my experience of pouring does not say the same.
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I've had a similar experience when I actually played with some glasses above the sink, but eventually googled the answer 'cause I've had enough incorrect answers on easy level: https://phys.org/news/2009-11-teapot-effect.html
It has been my experience with narrow-spouted jugs (as in the diagram) that the liquid simply overwhelms the spout and runs over the sides of the spout, making a huge mess. Milk jugs are notorious for this. Despite the mathematical reasoning, a wider spout prevents this in the real world.
The problem was over simplified. The fact is that any "spout" designed for dispensing liquids has a minimum and maximum flow rate. Even if the spout is not overwhelmed, as velocity increases it will reach a point where the liquid breaks into turbulent flow. At this point, wide or narrow, all else being equal you will make a mess.
If the receiving container is secured sufficiently, hold a long spoon or table knife across the top of vessel from which the liquid is being poured with the distal end across and beyond the spout extending to the inside the vessel into which the liquid is being poured, Gravity and the cohesive force of the liquid being poured will insure that all the liquid will be going into the receiving vessel.
Get a saucer seems a good idea?
If there is anything that determines the amount of adhesive force between the fluid particles and the container wall, wouldn't it affect the phenomenon too?
"When water is travelling at a particular average velocity in a pipe, when the radius is decreased over a distance, the average speed increases." Why is this? Is there a quantitative expression for it?
I thought it common knowledge😂
Yeah, the fact that it occurs on containers with no spout at all, means that it occurs on ones with the widest spouts. Hence using a narrower one is obviously the better option.
Everything life stuff!
Wait... so it doesn't matter how fast you're pouring?
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What you are asking is whether speed of water flow depends on angle between walls of container and vessel. The angle just decides how much water will flow not how fast, the speed will remain same = 2 g h regardless of the angle.
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Fast over here refers to the rate of the water pouring not the speed
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@Jared Wong – Then for that you need to consider Poiseulli's Equation,
Rate of flow of water = 8 n l π P r 4
n is viscosity of fluid.
I still spill every time I pour from my mr coffee pot. Only when I pour over the sink it does not spill. Perhaps I am pouring slower....
I thought this problem doesn't have solution.
Using Equation of Continuity, A 1 v 1 = A 2 v 2 , we can say that velocity of water at wider spout is less than that at narrower spout. This implies that in case of narrow spout the water is not in much contact with the spout or container and hence, doesnt climb onto the container due to adhesive forces as said by @Cubexyz 1 and doesnt spill off the container. The adhesive force between container and water is too low that the momentum or impulse gained by water at narrower spout is sufficient to overcome that adhesive force.
I hope my explanation is right.
I have been pouring liquids for over 50 years, I always used a smaller cup/glass or whatever to pour into a larger container. Never had spills! Whether it had a spot or not. Don't need science to figure that out. Maybe steady hands and don't pour at the edge of the container.
Cohesion, Adhesion and wetting or wettability as measured by contact angle. The Contact angle maybe zero, strong adhesion between the solid surface and a liquid, or may range 0 to 90 degrees for beads of fluid on a surface, or can be greater than 90 degrees and shrink away from the wetting surface, like a bead of mercury on glass. If you minimize the solid liquid interface then cohesive intramolecular forces can more readily hold the stream of flow together. I worked in research developing aircraft de-icing fluids for nine years. We made glycol fluids adhere to the surfaces of commercial jet airliners to prevent the formation of ice in Winter, but our fluid had to shear thin and leave the aircraft before the pilot rotates the aircraft and leaves the ground. Why? Any contamination on the wings of an aircraft can disturb the boundary layer flow and degrade the wings ability to lift the aircraft so we had to build often contradictory properties into our structured fluids. I learned a lot from Allan Barton’s book “States of Matter, States of Mind” (A good descriptive book on the subject of “matter”)
It's the sharpness of the edge also. Coanda effect.
Hahahaha. I can't wait to see the math this will generate. Pour from a container w a narrow spout or a v in its lip.
Or ask your Mommy to do it so you don't screw it up.
Narrow spout means less surface area for the water surface to adhere to. Therefore, the force due to pressure and gravity on the water is greater
The smaller spout is equivalent to a smaller water channel. There is a ratio which is similar to the Reynolds number for flows in channels, or around submerged objects. This ratio is the ratio of the fluid velocity (V) to the square root of the product of gravity and a characteristic length ... in this case the length of the channel or spout. This number is known as the Froude number: Froude number = V / SQRT(g * L)
There are three regimes for the Froude number: 1. Subcritical, (F < 1) 2. Critical (F = 1) 3 SuperCritical (F > 1)
Here is a very good website which describes this number, and what it means with respect to flow in channels. http://www.fsl.orst.edu/geowater/FX3/help/8 Hydraulic Reference/Froude Number and Flow States.htm
Narrow for speed is better, and also i would say that wider spout allows turbulence instead of laminar flow
I just compared the sizes of spouts I’ve experienced this from and determined an answer from that
The way I see it, is a container with no spout is like a container woth the widest spot possible, which is the worst option. Since you can't get any wider, wider can't be better, so narrower must be better. That's how I solved it at least.
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on considering the point where the water leaves the contact with the teapot with a spout, the velocity of the water molecules mist be great enough to overcome the adhesive nature of the teapot. When water is travelling at a particular average velocity in a pipe, when the radius is decreased over a distance, the average speed increases. This means, in the narrow spout, more molecules of water posses the energy to overcome the adhesive nature of the teapot. Thus the narrow spout has less spillage.