Ekman Spiral

The viscosity of the working fluid

The thickness of the Ekman layer is roughly (2 v/f)^1/2 (where v is the viscosity coefficient, f is the Corioli parameter). When you are using normal water (v=0.01cm²/s) as a working fluid, and the revolution speed is 10 times per minute (f=2), the thickness of the Ekman layer is only 1mm. In order to make the spiral visible, you need to use a fluid with a viscosity 2 factors higher than water.

 

Ink

If you use ink as coloration to make the current visible, after a couple of attempts at the experiment, color spreads throughout the fluid and it becomes unusable. If, however, you use a mix of dissolved sodium hydroxide and phenolphthalein and mix the water thoroughly after the experiment, the color disappears.
In this experiment, the colored water's specific gravity is adjusted to be just a little heavier than the water with table salt. This is to ensure that the heads of the colored water (the tip which resembles a mushroom cloud) do not float up to the surface.

 

Spouting ink on a rotating table.

You can't push a syringe on a rotating table by yourself. In this experiment, it was done by power of springs which were stretched using an electromagnet in advance.

 

Glycerin's hygroscopia

Glycerin has extremely high hygroscopic properties (it absorbs humidity well). As a result, if you leave a solution of glycerin out, it absorbs the water in the air, and its viscosity changes, meaning that before you start your experiment each time you have to use tissue paper to absorb and throw out the surface of the working fluid, and carry out the experiment as quickly as possible.