Fluid Dynamics For Dummies?

[lxskllr]

Got a new coffee carafe from the thrift shop to replace the stock dribble pot that came with my bunn. Works awesomely, and only cost $2.

My question, is there a way to succinctly describe why the old pot dribbled? Bonus for ms paint pictures. When you poured slowly, the pot dribbled down the pot body. When you poured fast, it still dribbled until a sustained flow was created. There was no way of pouring dribble free except for the possibility of turning the pot completely over, but that has its own problems :^P

 

[BoomerD]

I have an old Bunn 8 cup machine with the dribbling carafe. I don't worry about it.

 

[lxskllr]

I have an old Bunn 8 cup machine with the dribbling carafe. I don't worry about it.

I didn't care enough to buy one new, but thrift shop pricing, with 100% post consumer recycled content made it worth the effort.

 

[Red Squirrel]

I guess orbital mechanics might apply here, if you pour it fast enough the liquid reaches escape velocity of the surface it's on. If you pour slowly it just wants to stay on the surface. A sharp surface like a spout vs just a rounded edge will allow liquid to pour better even at slow speeds as it would require too sharp of a turn to stick to it so it takes the path of least resistance which is going into the air and pouring out. No idea of the accuracy of this pseudo science, I only have a theoretical degree in physics.

 

[Cerpin Taxt]

Perhaps there was a small (microscopic, even) irregularity or crack/chip/burr in the pour spout that disrupted the surface tension in the liquid that would otherwise hold the stream together and carry it out into space while pouring.

 

[Imp]

Choose one of, or a combination of:

1. Bernoulli equation
2. Laminar and turbulent flow
3. Total Head
4. Velocity Head
5. Elevation Head
6. Pressure Head
7. Surface Tension

That was like the first course I ever did well in during my university years. Figured out how it all fit together during my final exam...

And it sounds like the pot maker should have used a drip-edge.

 

[SKORPI0]

Maybe this explains it.

http://www.instructables.com/id/Solving-the-Dribbling-Coffee-Pot-Problem/

It is evident that the dribbling is caused by capillary action of the coffee adhering to the pot.
It is a simple mater of breaking the bond between the coffee and the pot.

 

[BoomerD]

Unfortunately, the glass spouts of Bunn carafes won't "file" nearly as easily.

I don't think I've ever had a coffee maker that had a plastic carafe...plastic handle and lid? Sure, but not the actual carafe.

 

[lxskllr]

Maybe this explains it.

http://www.instructables.com/id/Solving-the-Dribbling-Coffee-Pot-Problem/

That generally looks like the cause, but as Boomer said, the spout is formed tempered glass. The coffee doesn't want to leave the glass, even with decent force behind it at first. It's like it needs a stabilized flow for a few milliseconds to encourage the rest to follow suit.