I have added pieces of 24 carat gold to a bottle of water and they stay at the top rather than sink to the bottom which makes the water unpresentable. How I can make edible gold leaves sink in spring water? I need it to still be safe for drinking, so I can’t include any additives.
[Physics] How to make edible gold sink in water without affecting the drinking-water quality
fluid dynamicsforcessurface-tensionwater
Related Solutions
I was told by an engineer to use Manning's equation for open channel flow rate, as described here http://en.wikipedia.org/wiki/Manning_formula
Manning coefficient for some common materials: http://www.engineeringtoolbox.com/mannings-roughness-d_799.html - in my case it was acrylic sheet so 0.009 worked fine
Combining with discharge as stated in the wikipedia article means you can avoid calculating the velocity if you don't need it.
Q = cubic meters per second
A = .2 * .5 (cross sectional area in meters squared)
Rh = A / P, P is the wetted perimeter in this case .2 + .2 + .5
S = 0.09 (tan(5 degrees))
k = m^1/3/s
n = 0.009
So 0.08m^3/s, or in liters, 80 liters/second
Hmm, not sure if that is actually correct, but it's the right approach, and if correct, tells me I need to decrease the angle and decrease the depth in order to achieve a flow rate that I can find a cheap pump for!
A very nice observation. I think your thought is correct. I would add to that the fact that when light hits the leaves it bounces back also as IR. Then IR might have a good chance to be trapped in the droplet. On the other hand when light goes into a sphere droplet (like the ones on spider web) it has a good chance to get out soon enough so that it is not absorbed by water.
There is also the differences of the exposed surface areas. You have to compare the droplets on the leaves with ones on the spider web in which has the larger ratio of exposed area to volume. Since water evaporates from the surface, that can be an important factor in how long it takes for all the volume of the water to evaporate. For example, if we approximate the droplets on leaves with a cylinder with radius $r_c$ and and small height $h$ and droplets of the spider web with a sphere with radius $r_s$, then the ratio of surface areas of these to their volumes are compared with each other as, $$ \frac{\pi r_c^2}{h \pi r_c^2} =\frac{1}{h} \quad \mbox{compared to} \quad \frac{4\pi r_s^2}{\frac{4}{3}\pi r_s^3}=\frac{3}{r_s} $$ Now we should see if it is typical of $h$ to be smaller than $\frac{r_s}{3}$. If it is so then droplets on leaves probably evaporate faster.
Best Answer
It's floating because of surface tension, so your options are: reduce the surface tension with an edible surfactant (frequently used surfactants in cooking include: egg yolk, soy lecithin, and mustard), or add water on top of the gold leaf to get it below the surface (eg: spray them with a spray bottle until they sink).