Define what a Surface-Piercing propeller is

Just ask any thruster manufacturer what the current inflow degradation is.
I was looking at a spec the other day on a 8000kw azi and the manufacturer says its 6%/kt
Showing that if water is forced to the prop the thrust decreases proving a significant part of the thrust comes from the low pressure side.
Its a given in the world of Dynamic positioned vessels even anyone that works on a AHTS knows they cant tow at a force as big as the static bollard pull, why because there is current inflow the the props.
PS what pressure difference can you create underwater???

 

An F in the course of a self styled "professor" operating in his own world of ignorance is an "A" in the life I care to live.

I care not to agree with you, you obviously care not to have a logical debate.

As far as claiming to be a professor of physics, I went to your McCauley and Sons website as per your profile. Your alleged degree from Yale, that you so proudly posted, is conspicuously missing the seal of the school. 12 years of Latin schools allows me to discern that is a degree in "Philosophy" not "Physics". But they both start with "Ph" so it is close enough I guess.

I do not care how long in the tooth you are and how important it is in your life to be an expert at something. You are creating a universe with your obvious limitations as a governing force. In this world you are a god of your own rules. Good luck.

 

When I stated pressure difference on the blade , I mean force. You are correct that there is only one pressure.

My whole point in this discussion gone awry is that the pressure reduction on the forward side of the blade, created by the foil of a submerged propeller, generates the majority of the propulsive force.

Somehow we got into discussions of someone being a Physics instructor, and vacuums being measured in pressure.

I do not want to be snobby,.

I guess if someone wants to brand themselves and expert and spew ignorance into a conversation, without principals of logical debate as the basis for resolution, there is no hope in learning anything by either side.

 

The reason a foil shape is on a prop blade or wing is that extra strength is needed it makes sense to streamline it.
A flat plane as in a paper dart works just as well given an angle of attack.

 

An absolute vacuum is equal to two atmospheres of 14.7 psi you can get no more however hard you try on earth.
I will take Galileo and Torricelli`s findings.

 

Mr Kane, I have to say it - each post from you is a brand new surprise.

 

I agree in the air how about underwater?
We are talking pressure difference here

 

14.7 psi is 1 atmosphere. It doesn't matter if it's air or water.

 

So at 33', 1 extra atmosphere underwater how much pressure difference can I generate buy creating a low pressure?

 

You provide the readership with comedy.

 

It will depend on the foil shape, speed and the water temperature.
In terms of absolutes, the suction side will not get less than the water vapor pressure (full cavitation), which is around 2350 Pa at 20 deg Centigrades.
The pressure side cannot get more than the total freestream pressure (ambient + dynamic) which, for a given depth, depends on the speed.
The difference between the two is the maximum pressure difference a foil can give.

 

No it doesn't. Build a blade without camber and you have a very poor performance. What matters is concave on the high pressure side, convex on the low pressure side. When you ignore camber and try to do everything with the attack angle then the attack angle must be too large and a large drag results.

 

Not correct. The thrust/lift is due to the pressure difference across the foil, which is due to the circulation around the foil/blade. A thin wake can be seen to lowest order as a velocity sheet, the circulation can be calculated from the velocity discontinuity.

(Actually, I didn't graduate from Yale with a Ph.D. in theoretical physics, I drive a garbage truck ...). But for the sake of argument, are you willing to post a bet, held by Powerabout, and allow him to 'verify' my Yale physics Ph.D.? Will be glad to accommodate you if you make it worth my while.

 

dont need to check anything thrust from the suction side is a known phenomenon.
How you would measure the ratio from suction pressure side, i'm not sure.
Manufacturers just give you current inflow degradation data, dont know how they get it?

 

You behave as if ignorance were a virtue. If you need money, work.

How is it you continue to add more to a conversation without addressing the simple question addressed to you for clarification? Is that the hallmark of a man of education? Your lack of ability to have a simple discussion is astonishing.

You introduce more tangent subject matter without clarifying anything...just talking.

I may be talking nonsense but you are talking only to be heard. You never answer any questions, just spewing material irrelevant to the initial query.

I withdraw from any further "discussion" with you as you are a master of your domain and insist to remain unchallenged by changing subject matter by swinging subjects and never engaging in a discussion.