Bill,
If I'm reading Jim's explanation correctly, he's stating that the natural
airfoil shape of the boat generates even lower pressure across the top of
the boat then in the tunnel, creating lift. And that lift is more than
counteracting the low pressure venturi effect of the tunnel that you are
describing.
How such an inefficient airfoil shape as a catamaran boat, moving at maybe
20 kts, will generate enough lift to noticeably change the ride of a boat
weighing 10,000 or 20,000 lbs... Shucks, forget the propeller hanging off
the stern, I'm mounting a propeller up on the anchor pulpit!
Bob Deering
Juneau, Alaska
On 3/6/09 6:46 PM, "Bill Fleenor" wefleenor@ucdavis.edu wrote:
Jim,
When air passes through the tunnel it is going through a constriction. That
will increase the velocity (continuity equation). Consequently,
conservation of energy requires that increased velocity results in reduced
pressure. Reduced pressure in the tunnel will tend to pull the hull down
toward the water, although it would be small at these speeds.
Now I haven't had a compressed fluid flow class for 40 years, but the only
limit to this Venturi effect is 'choked flow' which will only occur as the
air flow approaches the speed of sound.
Can you explain how your concept of lift occurs in violation of the laws of
physics? Thanks.
Bill Fleenor
Double-Wide
Power-Catamaran Mailing List
Bill,
If I'm reading Jim's explanation correctly, he's stating that the natural
airfoil shape of the boat generates even lower pressure across the top of
the boat then in the tunnel, creating lift. And that lift is more than
counteracting the low pressure venturi effect of the tunnel that you are
describing.
How such an inefficient airfoil shape as a catamaran boat, moving at maybe
20 kts, will generate enough lift to noticeably change the ride of a boat
weighing 10,000 or 20,000 lbs... Shucks, forget the propeller hanging off
the stern, I'm mounting a propeller up on the anchor pulpit!
Bob Deering
Juneau, Alaska
On 3/6/09 6:46 PM, "Bill Fleenor" <wefleenor@ucdavis.edu> wrote:
> Jim,
>
> When air passes through the tunnel it is going through a constriction. That
> will increase the velocity (continuity equation). Consequently,
> conservation of energy requires that increased velocity results in reduced
> pressure. Reduced pressure in the tunnel will tend to pull the hull down
> toward the water, although it would be small at these speeds.
>
> Now I haven't had a compressed fluid flow class for 40 years, but the only
> limit to this Venturi effect is 'choked flow' which will only occur as the
> air flow approaches the speed of sound.
>
> Can you explain how your concept of lift occurs in violation of the laws of
> physics? Thanks.
>
> Bill Fleenor
> Double-Wide
> _______________________________________________
> Power-Catamaran Mailing List
