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Sep
9
answered What are these rays that appear in photograph of sun?
Jul
18
awarded  Benefactor
Jul
18
accepted Frequency of Vortex Shedding
Jul
15
comment Frequency of Vortex Shedding
Thank you, things are clearer to me now. But I need to think about it for a while..
Jul
14
comment Glass - paper: Stevin's Law
They should work together. The surface tension force itself is extremely weak, it loses against water's total weight even for small radius cases. You can see how little amount of water an open straw can hold (even if it is made of glass). The air pressure difference holds most of the water's weight, and the surface tension takes care of the rest which is very small. So in terms of supporting the water's weight, the surface tension is negligible. But it does an important job to prevents water leaking from sideways and it also prevents water to penetrate through little holes in the paper
Jul
14
comment Glass - paper: Stevin's Law
I agree with Carl, I did an experiment to test it. If I let some water out, the paper bents slightly upward. I just need to slightly tilt the glass with a paper attached below it. It makes the water pressure more concentrated in a smaller region, thus in this region the surface tension must retain a very strong pressure. Eventually it won't be able to hold and it breaks. If I let more out, again the paper bents upward more.
Jul
14
comment Glass - paper: Stevin's Law
@usumdelphini Surface tension keeps the water from leaking sideways. It also holds against the remaining water weight since the air pressure difference doesn't fully support the water. If we have a longer water column, the water pressure will be higher. It would be more difficult to retain and the air gap also needs to expand more. We know that the water pressure force is proportional to $r^2$ and the surface tension force to $r$. Thus if we increase the circumference of the glass, the pressure force will increases faster and win the battle more easily. That's why it's difficult for big tank.
Jul
13
comment Frequency of Vortex Shedding
There is a leap in logic here "The faster the flow the faster the higher the frequencies which the eddies are being shed". Suppose at a moment, the flow is building a vortex in one direction and then after a while it starts creating another vortex in the opposite direction. You are just talking about how fast one vortex is getting bigger. What matters here is how long does it takes to change the direction of the wake, am I right?
Jul
13
comment Frequency of Vortex Shedding
I don't say that I would neglect the Strouhal number. The fact that Strouhal number is almost constant in this region is part of the question, it is one of the reason why the formula is so simple. Wait a second, what do you mean be the flow crossing time? Can you explain more clearly how does it related to how fast the wake switch from one side to the other?
Jul
13
comment Frequency of Vortex Shedding
Thanks for answering, but I don't think it's that simple. The frequency in the formula corresponds to how fast the wake "moves" back and forth. It doesn't directly related to how fast the fluid passes through the cylinder right? It's much more complicated. Take a look at this youtube.com/watch?v=IPBKR9cSce0
Jul
12
awarded  Promoter
Jul
12
revised Frequency of Vortex Shedding
deleted 21 characters in body
Jul
11
revised Frequency of Vortex Shedding
deleted 403 characters in body
Jul
10
revised Frequency of Vortex Shedding
added 5 characters in body
Jul
10
asked Frequency of Vortex Shedding
Jul
2
awarded  Yearling
Mar
21
revised Direction of rotation of proton in magnetic field--opposite to a dipole
I've included the important arguments that I made in the deleted comments so that everyone can read.
Mar
21
revised Direction of rotation of proton in magnetic field--opposite to a dipole
I included the important arguments that I made in the deleted comments so that everyone can read.
Mar
19
comment Direction of rotation of proton in magnetic field--opposite to a dipole
Sure, let's continue there
Mar
18
accepted What really cause light/photons to appear slower in media?