Wow, what an ingenious idea! I've learned all about Bernouilli's Law and the venturi effect, but I'd never thought of using it to suck air into wort! Definitely going to have to try this.
One question: There is an obvious trade off where the venturi tube is placed.
1. Immediately after leaving the BK. This allows the longest amount of contact time between the wort and the air bubbles
2. Mid way down/near the bottom. Wort is traveling faster, creating a greater vacuum and pulling more oxygen in.
Can anyone confirm which has produced better results?
I'd also like to point out something that was mentioned much earlier in this thread (sorry I don't know the name of who mentioned it, but you take the credit for this one). Some sort of perforated plate should be placed immediately downstream of the venturi tube. This would serve to produce more turbulence and to break the bubbles into smaller bubbles, increase surface area and the rate of diffusion of oxygen into the wort. However, this is quite a restriction, and I'm not sure what effect this pressure loss effect would have on the rate of oxygen intake is.
Thanks again for this! Now no more lifting 50lb carboys!