Inlet passage shapes (water and air)

Before we begin, what is the major differences between water and air propellers and the mediums they operate in?
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I see slotted/grated waterjet intakes which look a lot like NACA air intakes, so I'm guess there are many similarities between how water and air acts.

Questions (see figure):

1. Passive air intake (no fan) body moving under 100 mph (if in air), which air intake is most efficient? Is water any different, why?

2. Active powered fan situation, body moving under 100 mph (if in air), which air intake system is most efficient? Is water any different, why?

3. Please direct me to an on-line source of information which explains when, where and why.



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Imagine these images turned upside down and in water, what would the answers be?

NOTE: Figure "C" exist in an air-cooled Porsche 911 for the cooling fan in an abstract way. Is there an equal situation in the water world?

 

Come on, are the sketches that bad?

 

Can this be applied to watercraft to reduce wake and drag?

Boeing makes 'quiet' advances
Noise-reduction efforts pay off at remote airfield in Montana

By JAMES WALLACE
SEATTLE POST-INTELLIGENCER AEROSPACE REPORTER
http://seattlepi.nwsource.com/business/236095_quietjet11.html

Photo Caption:

 

Hi, George, I just found this thread.

OK, The first and most obvious difference is that, while both air and water are fluids, "standard" water is 773.45 times more dense than "standard" air.

Another is that the density of air changes much more readily than the density of water. So relatively minor changes in air temperature and humidity will affect air propulsion systems significantly. Temperature changes in water have much less impact.

A third is that, under all "normal" circumstances, air is compressible, water is not. Compressing air increases its density, with lots of fun effects on power calculations.

Water propellors are smaller in diameter and stronger (requirement of operating in a denser fluid).

OK, got to get back to work. I'll review your questions and sketches later.

 

Cool, when ever........no rush.

I was looking up the term inlet flow distortion when I found an interesting image.

http://caltechbook.library.caltech.edu/22/01/chap4.htm

It's a start.

 

Looks like I have the right phrase to Google search with for sure.

http://www.techsburg.com/

http://www.techsburg.com/Case_Studies/PropAirframeInt.html

Note: serpentine inlet is another search term I'm trying.

 

wadda you do when your at work george?

 

I'm a self employed architect in Michigan, things are real slow right now. I took up to Calculas 4 in college, but nothing stuck - my right side of my brain is far too dominant.

Hey, this looks a little like figure "C".

http://emeraldinsight.com/Insight/v...Action=lnkhtml&contentId=876497&history=false

 

In an open air prop configuration, tip speed is very important.
See: http://www.pponk.com/
http://www.hoverhawk.com/propspd.html

All props (water/air) are more efficient when enclosed. As you know, a water jet has an impeller vs. a propeller. Wikipedia has a good description:
Since impellers have no large blades to turn, they can spin at much higher speeds than propellers. The water forced through the impeller is channelled by the housing, creating a water jet that propels the vessel forward. The housing is normally tapered into a nozzle to increase the speed of the water, which also creates a Venturi effect in which low pressure behind the impeller pulls more water towards the blades, tending to increase the speed.

To work efficiently, there must be a close fit between the impeller and the housing. The housing is normally fitted with a replaceable wear ring which tends to wear as sand or other particles are thrown against the housing side by the impeller.

Vessels using impellers are normally steered by changing the direction of the water jet.

 

Most water jets are axial flow. There also was some centrifgal pumps that monted on the bottom of outboard motors. In that the water had to change direction, they weren't very efficient and they came up with ways to make and attach axial flow oumps.

 

More or less that is true, I have to admit and as you can see from the sketches "ducted" is where my mind is at.

Mass Flow.......another good term
http://www.adl.gatech.edu/classes/propulsion/prop9.html


1. Inlet flow distortion

2. Serpentine inlet

3. Mass Flow

Any other search terms which will help out my quest?

Google search:
Inlet flow distortion Serpentine inlet Mass Flow
http://scitation.aip.org/getabs/ser...00126000002000266000001&idtype=cvips&gifs=yes

Sounds like an old Williams Internations cruise jet missile.

 

Some performance is lost using a water jet on a boat vs. a propeller. Case in point: I had a 21' boat with a 320Hp Ford 460 and Berkely water jet. Top speed was 50 mph. The same engine and boat hooked to an outdrive w/prop would have a top speed of 60-65 mph. The jet was way quicker out of the hole, however, because the impeller let the engine rev up instantly into it's high power range. A jet has only one moving part vs. several gears, thus far less expensive maintenance required.

 

Have you seen the snowmobile verses jetski race? The surface area of the track allowed the snowmobile to beat the jet ski even on a course with many turns.

Just an interesting weird thing.

STRICT inlet by Lockeed Martin:
http://scholar.lib.vt.edu/theses/available/etd-08142003-225036/unrestricted/Thesis_rabe_final.pdf

More STRICT from an Air Force site:
http://www.afrlhorizons.com/Briefs/Aug04/VA0309.html

 

I guess what I am trying to say, is that when a prop is changed into an impeller, when ducted, the output force is changed. When actual props are ducted, they become more efficient. Many of the tugboats now have ducted props. I saw an experimental plane a while back, that had ducted props and it could take off in a lot less distance. The impellers seem to require more rpm's, which with a smaller diameter is possible.

 

Have you seen the Jet model airplanes? They have a ducted prop that looks like the impeller on a marine bilge blower.