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#1
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how a sail works, who can help me explain?
"Simple Simon" wrote: That's precisely why I give more credence to Venturi. I like to keep it simple as my name suggests. Why clutter a good physical reality with extra theories that may or may not be applicable? In my opinion the theory: "air tends to follow the sail (also on the leeward), and thus deflects the air, and for that deflection you need a force, and that force is the sailforce" is easier as explaining: "the path on the leeward is longer, so the air has to move faster" continued with "fast moving air has a lower pressure" "just like in a venturi in a pipe" Please note that I do not make air molecules bounce of the sail, I am deflecting a flow of air. To check if that flow has not separated from the sail I also reccomend telltales. Please read www.sailtheory.com/sail.html for more details. What might be confusing: Bernoulli never had a theory for a wing. He had a theory for explaining how high a fountain would spray. Newton never had a theory for a wing, his theory was about bouncing balls and planets etc. Euler, Kutta and Joukofski, and Prandtl all had some theories about flow around a wing. For some strange reasons they are not often mentioned. (I am promoting Ludwigs Prandtl "lifting line theory" if you want to know) I quit this discussion, I think the "longer path gives higher speed, and thus lower pressure" theory really sucks. If you do not need a theory, please do not use a theory. It is better to use no theory as to use a stupid one. Thank you for giving your opinion. Best Regards, Pim -- Posted by news://news.nb.nu |
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#2
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how a sail works, who can help me explain?
"PIM" wrote in message ...
"Simple Simon" wrote: That's precisely why I give more credence to Venturi. I like to keep it simple as my name suggests. Why clutter a good physical reality with extra theories that may or may not be applicable? In my opinion the theory: "air tends to follow the sail (also on the leeward), and thus deflects the air, and for that deflection you need a force, and that force is the sailforce" is easier as explaining: "the path on the leeward is longer, so the air has to move faster" continued with "fast moving air has a lower pressure" "just like in a venturi in a pipe" Please note that I do not make air molecules bounce of the sail, I am deflecting a flow of air. To check if that flow has not separated from the sail I also reccomend telltales. Please read www.sailtheory.com/sail.html for more details. What might be confusing: Bernoulli never had a theory for a wing. He had a theory for explaining how high a fountain would spray. Newton never had a theory for a wing, his theory was about bouncing balls and planets etc. Euler, Kutta and Joukofski, and Prandtl all had some theories about flow around a wing. For some strange reasons they are not often mentioned. (I am promoting Ludwigs Prandtl "lifting line theory" if you want to know) I quit this discussion, I think the "longer path gives higher speed, and thus lower pressure" theory really sucks. If you do not need a theory, please do not use a theory. It is better to use no theory as to use a stupid one. Thank you for giving your opinion. Best Regards, Pim Very good webpage about physical Sail/Lift Theory Pim! The best I have seen so far on the web! Mikko in Finland has a very good page also with airflow computer animations. It´s only Navier-Stokes Lift calculations that comes close to the real physics! Prandtl "Lifting Line Theory" is only useful for a physical non existing "ideal/perfect fluid" created only by mathematical equations! Jan-Olov Newborg |
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#3
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how a sail works, who can help me explain?
Just out of curiosity, Jan-Olov, what boat do you sail?
"Jan-Olov Newborg" wrote in message om... Very good webpage about physical Sail/Lift Theory Pim! The best I have seen so far on the web! Mikko in Finland has a very good page also with airflow computer animations. It´s only Navier-Stokes Lift calculations that comes close to the real physics! Prandtl "Lifting Line Theory" is only useful for a physical non existing "ideal/perfect fluid" created only by mathematical equations! Jan-Olov Newborg |
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#4
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how a sail works, who can help me explain?
"Simple Simon" wrote in message ...
Just out of curiosity, Jan-Olov, what boat do you sail? "Jan-Olov Newborg" wrote in message om... Very good webpage about physical Sail/Lift Theory Pim! The best I have seen so far on the web! Mikko in Finland has a very good page also with airflow computer animations. It´s only Navier-Stokes Lift calculations that comes close to the real physics! Prandtl "Lifting Line Theory" is only useful for a physical non existing "ideal/perfect fluid" created only by mathematical equations! Jan-Olov Newborg Today I sail an old English boat called Vivacity, a very slow type! I have been on board Americas Cup/Volvo Ocean Race Cup boat, "Assa Abloy and the catamaran "Nokia" sailing with 265 m2 sailarea. By the way, do you belive in "Bernoulli law" , saying that "High Airflow velocity causing Low Pressure"? That should mean the the jetblast behind an F-16 Fighter running on afterburner should create low pressure! But thats not being the case! The total pressure is very high due to the high dynamic pressure! The Venturi effect you discuss is pure due to "The Coanda effect" and the turning of the airflow along the walls of the divergentpart of the pipe! How local pressure gradients are created by turning the fluidflow you can read he http://www.scienceweb.org/movies/aero.htm Jan-Olov Newborg Here are some links of flow physics (not flow mathematics): A Physical Description of Flight © http://www.aa.washington.edu/faculty/eberhardt/lift.htm Bernoulli Versus Newton http://www.grc.nasa.gov/WWW/K-12/airplane/bernnew.html What is Ground Effect? http://home.mira.net/~radacorp/ground_effect.html Operational use of angle of attack (AOA) on modern commercial jet airplanes http://www.boeing.com/commercial/aer...12/attack.html Weltner Lift http://www.rz.uni-frankfurt.de/~weltner/ http://www.rz.uni-frankfurt.de/~welt...ht/PHYSIC4.htm Weltner Bernoulli http://www.informatik.uni-frankfurt..../MIS/mis6.html Incorrect theory number three http://www.grc.nasa.gov/Other_Groups...ne/wrong3.html Lift from flow turning http://www.lerc.nasa.gov/www/K-12/airplane/right2.html Jef Raskin - Coanda Effect: Understanding Why Wings Work http://www.jefraskin.com/forjef/jefw...da_effect.html F18 Soundbarrier and highspeed pass http://www.algonet.se/~newborg/ Beaty Gif pictures smokepuls plus SAAB 2000 http://www.amasci.com/wing/airgif2.html Prof. Colombinis photogallery http://www.diam.unige.it/~irro/gallery.html Flow around an airfoil http://www.diam.unige.it/~irro/profilo_e.html ScienceWeb - Aerodynamics http://www.scienceweb.org/movies/aero.htm Lift from spinning balls This website gives a lot of references all back to Newton/Robbins! The Magnus Effect http://www.geocities.com/k_achutarao...ew_magnus.html The Science of Swing, maintained by James Foster http://www.soest.hawaii.edu/GG/STUDE...ter/swing.html Normal Swing http://www.soest.hawaii.edu/GG/STUDE...er/normal.html Reversed Magnus effect explained http://www.soest.hawaii.edu/GG/STUDE...r/reverse.html Wrong lift explanations Smithsonian http://www.nasm.edu/galleries/gal109/NEWHTF/HTF510.HTM False Bernoulli explanations How things fly, an interactive gallery. Bernoulli Brain-Teasers. Activities you can do at home http://www.nasm.edu/galleries/gal109...XT/TEASERS.HTM US AirForce Museum http://www.wpafb.af.mil/museum/zone/ff3.htm Dr. John S. Denker online aerodynamic book. Wrong Lift explanation explained by "Circulation flow 'creating' the Velocity Field" http://www.monmouth.com/~jsd/fly/how/htm/ http://www.monmouth.com/~jsd/fly/how/htm/airfoils.html |
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#5
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how a sail works, who can help me explain?
By the way, do you belive in "Bernoulli law" , saying that "High
Airflow velocity causing Low Pressure"? I believe in the phenomena of decreased internal pressure with increased stream velocity. That should mean the the jetblast behind an F-16 Fighter running on afterburner should create low pressure! If that were true it should mean that you could put jet fuel in a container and ignite it and then low pressure will suck the container into a ball. But thats not being the case! The total pressure is very high due to the high dynamic pressure! And that would be due to the expansion of gases among other things associated with the combustion of jet fuel. The Venturi effect you discuss is pure due to "The Coanda effect" and the turning of the airflow along the walls of the divergentpart of the pipe! How local pressure gradients are created by turning the fluidflow you can read he Local pressure gradients are created by a solid object and a relative airflow pushing and pulling on each other. This pushing and pulling is what turns the relative airflow. Local pressure gradients are a characteristic of this pushing and pulling not the cause. You got the horse before the cart. Its like saying cars go fast because of miles per hour. |
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#6
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how a sail works, who can help me explain?
Spock,
I suggest you consider the names of the fuel and the engnes , Jet fuel, Jet after brners, jet fighters and try to imagine the operations that created those names OT |
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#7
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how a sail works, who can help me explain?
Why don't you read them yourself? WE already know how a sailboat works.
Cheers MC Jan-Olov Newborg wrote: "Simple Simon" wrote in message ... Just out of curiosity, Jan-Olov, what boat do you sail? "Jan-Olov Newborg" wrote in message om... Very good webpage about physical Sail/Lift Theory Pim! The best I have seen so far on the web! Mikko in Finland has a very good page also with airflow computer animations. It´s only Navier-Stokes Lift calculations that comes close to the real physics! Prandtl "Lifting Line Theory" is only useful for a physical non existing "ideal/perfect fluid" created only by mathematical equations! Jan-Olov Newborg Today I sail an old English boat called Vivacity, a very slow type! I have been on board Americas Cup/Volvo Ocean Race Cup boat, "Assa Abloy and the catamaran "Nokia" sailing with 265 m2 sailarea. By the way, do you belive in "Bernoulli law" , saying that "High Airflow velocity causing Low Pressure"? That should mean the the jetblast behind an F-16 Fighter running on afterburner should create low pressure! But thats not being the case! The total pressure is very high due to the high dynamic pressure! The Venturi effect you discuss is pure due to "The Coanda effect" and the turning of the airflow along the walls of the divergentpart of the pipe! How local pressure gradients are created by turning the fluidflow you can read he http://www.scienceweb.org/movies/aero.htm Jan-Olov Newborg Here are some links of flow physics (not flow mathematics): A Physical Description of Flight © http://www.aa.washington.edu/faculty/eberhardt/lift.htm Bernoulli Versus Newton http://www.grc.nasa.gov/WWW/K-12/airplane/bernnew.html What is Ground Effect? http://home.mira.net/~radacorp/ground_effect.html Operational use of angle of attack (AOA) on modern commercial jet airplanes http://www.boeing.com/commercial/aer...12/attack.html Weltner Lift http://www.rz.uni-frankfurt.de/~weltner/ http://www.rz.uni-frankfurt.de/~welt...ht/PHYSIC4.htm Weltner Bernoulli http://www.informatik.uni-frankfurt..../MIS/mis6.html Incorrect theory number three http://www.grc.nasa.gov/Other_Groups...ne/wrong3.html Lift from flow turning http://www.lerc.nasa.gov/www/K-12/airplane/right2.html Jef Raskin - Coanda Effect: Understanding Why Wings Work http://www.jefraskin.com/forjef/jefw...da_effect.html F18 Soundbarrier and highspeed pass http://www.algonet.se/~newborg/ Beaty Gif pictures smokepuls plus SAAB 2000 http://www.amasci.com/wing/airgif2.html Prof. Colombinis photogallery http://www.diam.unige.it/~irro/gallery.html Flow around an airfoil http://www.diam.unige.it/~irro/profilo_e.html ScienceWeb - Aerodynamics http://www.scienceweb.org/movies/aero.htm Lift from spinning balls This website gives a lot of references all back to Newton/Robbins! The Magnus Effect http://www.geocities.com/k_achutarao...ew_magnus.html The Science of Swing, maintained by James Foster http://www.soest.hawaii.edu/GG/STUDE...ter/swing.html Normal Swing http://www.soest.hawaii.edu/GG/STUDE...er/normal.html Reversed Magnus effect explained http://www.soest.hawaii.edu/GG/STUDE...r/reverse.html Wrong lift explanations Smithsonian http://www.nasm.edu/galleries/gal109/NEWHTF/HTF510.HTM False Bernoulli explanations How things fly, an interactive gallery. Bernoulli Brain-Teasers. Activities you can do at home http://www.nasm.edu/galleries/gal109...XT/TEASERS.HTM US AirForce Museum http://www.wpafb.af.mil/museum/zone/ff3.htm Dr. John S. Denker online aerodynamic book. Wrong Lift explanation explained by "Circulation flow 'creating' the Velocity Field" http://www.monmouth.com/~jsd/fly/how/htm/ http://www.monmouth.com/~jsd/fly/how/htm/airfoils.html |
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#8
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how a sail works, who can help me explain?
The_navigator_© wrote in message ...
Why don't you read them yourself? WE already know how a sailboat works. Cheers MC Since you try to explain the sailforces using false "longer airflow path behind the sail and sail beeing a "half venturi pipe", you seems to need more correct physical flow information! Jan-Olov Newborg How local pressure gradients are created by turning the fluidflow you can read he http://www.scienceweb.org/movies/aero.htm Here are some links of flow physics (not flow mathematics): A Physical Description of Flight © http://www.aa.washington.edu/faculty/eberhardt/lift.htm Bernoulli Versus Newton http://www.grc.nasa.gov/WWW/K-12/airplane/bernnew.html What is Ground Effect? http://home.mira.net/~radacorp/ground_effect.html Operational use of angle of attack (AOA) on modern commercial jet airplanes http://www.boeing.com/commercial/aer...12/attack.html Weltner Lift http://www.rz.uni-frankfurt.de/~weltner/ http://www.rz.uni-frankfurt.de/~welt...ht/PHYSIC4.htm Weltner Bernoulli http://www.informatik.uni-frankfurt..../MIS/mis6.html Incorrect theory number three http://www.grc.nasa.gov/Other_Groups...ne/wrong3.html Lift from flow turning http://www.lerc.nasa.gov/www/K-12/airplane/right2.html Jef Raskin - Coanda Effect: Understanding Why Wings Work http://www.jefraskin.com/forjef/jefw...da_effect.html F18 Soundbarrier and highspeed pass http://www.algonet.se/~newborg/ Beaty Gif pictures smokepuls plus SAAB 2000 http://www.amasci.com/wing/airgif2.html Prof. Colombinis photogallery http://www.diam.unige.it/~irro/gallery.html Flow around an airfoil http://www.diam.unige.it/~irro/profilo_e.html ScienceWeb - Aerodynamics http://www.scienceweb.org/movies/aero.htm Lift from spinning balls This website gives a lot of references all back to Newton/Robbins! The Magnus Effect http://www.geocities.com/k_achutarao...ew_magnus.html The Science of Swing, maintained by James Foster http://www.soest.hawaii.edu/GG/STUDE...ter/swing.html Normal Swing http://www.soest.hawaii.edu/GG/STUDE...er/normal.html Reversed Magnus effect explained http://www.soest.hawaii.edu/GG/STUDE...r/reverse.html Wrong lift explanations Smithsonian http://www.nasm.edu/galleries/gal109/NEWHTF/HTF510.HTM False Bernoulli explanations How things fly, an interactive gallery. Bernoulli Brain-Teasers. Activities you can do at home http://www.nasm.edu/galleries/gal109...XT/TEASERS.HTM US AirForce Museum http://www.wpafb.af.mil/museum/zone/ff3.htm Dr. John S. Denker online aerodynamic book. Wrong Lift explanation explained by "Circulation flow 'creating' the Velocity Field" http://www.monmouth.com/~jsd/fly/how/htm/ http://www.monmouth.com/~jsd/fly/how/htm/airfoils.html -- |
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