tag:blogger.com,1999:blog-19936712.post2799126818064442700..comments2024-02-14T23:28:11.026-08:00Comments on FORGOTTEN PROPHETS: ReframingJack Hhttp://www.blogger.com/profile/04599425185005999225noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-19936712.post-32127743781807893112008-12-05T18:30:00.000-08:002008-12-05T18:30:00.000-08:00Re birds, that was my supposition -- I was thinkin...Re birds, that was my supposition -- I was thinking that given an open container the displaced air would redistribute the downward force outward -- wind is force, after all. Seems like an averages thing -- if you jump on a scale, first it's heavier, then lighter, then it bears your weight again.<BR/><BR/>As for all that jibberjabber about slip flows and balsawood toys, I just can't follow it. Weren't we talking about PLANES???<BR/><BR/>Anyways, I resigned in righteous dismay and deepest disgust from the corrupt Will C klepocracy long, long ago. Started my own breakaway republic, governed with benignant authority by a certain here-unnamed genius of untold brilliance and beauty. Can you guess?Jack Hhttps://www.blogger.com/profile/04599425185005999225noreply@blogger.comtag:blogger.com,1999:blog-19936712.post-27082012682494536142008-12-05T16:16:00.000-08:002008-12-05T16:16:00.000-08:00Read up on the no-slip condition. If the flow can...Read up on the no-slip condition. If the flow can be made laminar (low Re number) fields of flow lines will eminate from the fast moving belt surface essentially causing moving air above the surface of the belt. You never said how large the plane had to be (I'm thinking of something on the order if the little basla models that had a metal clip for ballast) and you never said how fast the belt could move nor the surface composition. All could be optimized to create greater flow. This <B>in addition</B> to "ground effect" (a benefit caused by flying low wherein the displaced under-wing air has less room to evacuate resulting in increased lift) should be sufficent to cause lift on the inverted NACA profile. <BR/>Any <B>further</B> doubts in my assessment will result in your demotion in the Will C. administration from Cabinet Level to something sucky-er...say, Secretary of State. <BR/><BR/>"I'm still puzzling over whether or not birds flying inside an enclosed container make it weigh more." <BR/><BR/>I would estimate that it weighs more. The downward forced air is in equilibrium to the lift the bird is maintaining. This force would be equivalent to the bird's weight and would contribute to the total weight (or downward force F=ma where m = total mass of bird + jar and a = 32.2ft/s^2).Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-19936712.post-12711558610063123382008-12-04T12:21:00.000-08:002008-12-04T12:21:00.000-08:00You're supposing that the virtually flat surface o...You're supposing that the virtually flat surface of a treadmill could generate enough wind via surface friction to lift the mass of a plane? Although my background is more in the humanities, I suggest the belt speed required, if your premise is even correct, would surpass the material specs. Wind generated by a rotating flat surface seems negligible. Blades have an angle, after all. Also, would there be an eddy effect from the lower belt, with wind convecting up and confusing any lift effect? And what about the spinning of the plane wheels? Does any wind generated by them cancel out? Presumably. <BR/><BR/>I'm still puzzling over whether or not birds flying inside an enclosed container make it weigh more.Jack Hhttps://www.blogger.com/profile/04599425185005999225noreply@blogger.comtag:blogger.com,1999:blog-19936712.post-11104767798695121422008-12-04T10:29:00.000-08:002008-12-04T10:29:00.000-08:00Wind.Tunnel.Wind.<BR/><BR/>Tunnel.Jack Hhttps://www.blogger.com/profile/04599425185005999225noreply@blogger.comtag:blogger.com,1999:blog-19936712.post-54532727933735839912008-12-04T07:29:00.000-08:002008-12-04T07:29:00.000-08:00"Except that it's not the wheels that make a plane..."Except that it's not the wheels that make a plane fly, nor its relative position to the surface of the earth. It's wind velocity, whatever the technical term, and thrust. It's not speed relative to the ground, but relative to the air."<BR/><BR/>If the belt is moving fast enough it could cause airflow through the body of the plane and over the wings (perhaps enough for lift) due to the "no-slip condition" between the moving belt and the air above it as defined in fluid mechanics. But then the higher velocity air would be moving moreso along the lower surface of the wing thus causing downforce...so I've disproved my assertion.<BR/><BR/>But wait if you inverted the wing and its say...a nice NACA 2412 profile and ran the belt fast enough you could generate lift. One caveat is that the nose (or front) of the plane would have to be tethered to some distant point over come the friction of the rolling landing gear. But, if the plane is simply dropped into the flow field then you would eliminate the need for the tether.<BR/><BR/>See what you've gone and done making me think and stuff.Anonymousnoreply@blogger.com