How can I make a vacuum pump to move rocks from one place to another?

Question

I am trying to build a vacuum pump by myself and move rocks from one place to another. After some online search, I came across this video on Youtube. I am trying to build something like this. Can anyone explain the science behind it and tell me how I can make this by myself?

Answer 1

What you are seeing in the video is a vacuum generator/vacuum ejector/aspirator.

Figure 1: Venturi effect (source: wikipedia)

It uses the principle of the Venturi effect. I.e. that for steady, incompressible, inviscid when there is an increase of speed there is a drop in static pressure. This is mathematically expressed as:

$$p_1-p_2 =\frac{\rho}{2} (v_2^2- v_1^2) $$

Application in vacuum generators.

This is used in vacuum generators, in the following way:

Figure 2: Application on Vacuum generators (source: COVAL)

Initially, Compressed air is driven through a nozzle. This increases the velocity (and the kinetic pressure) and drops the static pressure. At the exit of the orifice there is pressure drop which creates a negative pressure which sucks in air (and other small materials).