J.C.MacSwell

That's pretty much right although the background is not actually smoother. I was referring to the air for the boundary layers, though of course the water surface and just below is as well.

Hi Luminance. Welcome to the Forum. I guess it would depend on your interests as both are involved in the photo. For physics, while interested in both, I'm more knowledgeable about boundary layers and in this case "reading the water". to determine and attempt to predict wind patterns. The wind speed in the photo is in the range of 3-5 knots in the background and likely 1-3 in the foreground. There is a wind shear between the two where the background air rises up and over the air in the foreground. The "windline" is probably moving at under 0.5 knots and may in fact be fairly fixed. I would have a very high confidence level for these conditions to state all that even based on one photo. In other conditions it can be much more difficult and less certain. What I find pretty interesting is that even in hurricane force conditions you can see related effects. You can read the effect on the water when a gust of upper airflow breaks the surface tension on the water, and fans out pushing against the "relatively" slower surface air that had established a more laminar boundary layer, even at those greater windspeeds and larger wave conditions.

I think it means he has a burden that he knows he cannot prove.

Oscillating lift results from instability in the wake behind a cylinder. It is a well known and common phenomenon in both turbulent and laminar (upstream) flow. To claim lift does not happen in the wake of another cylinder except in very specific and limited circumstances is not credible. It would take an infinite amount of experiments (rule every other possibility out) while getting no lift to support that claim. Did you actually read the statement? It says there can be no lift in a cylinder in the wake (vortex street) of another unless it is identical in diameter and even then only while between 3-6 diameters distance downstream. Do you not think it might be a misquote, typo, translation or transcription error or there is something wrong or missing...? Not convinced? Hold two 1" broomsticks out the window of a car, one behind the other, the second covered loosely with a 1.5" plastic pipe, but secured so that it will not slide off. Accelerate until the pipe flutters. (When did you stop believing creationist theory? Is it fair to assume you accepted it, when you first heard it, on a "provisional basis" until you were convinced otherwise? Or did you, somewhat ironically, doubt it immediately using "creationist logic"?}

Assuming no friction the acceleration would be 2/3. Essentially, using a pulley to redirect part of the force, you are accelerating the whole 450kg with the force of gravity of that on the 300kg. Fall Time: [math] \sqrt{\frac{6*2}{6.53}} = 1.36 s [/math] Velocity: [math] 6.53*1.36 = 8.88 m/s [/math]

I disbelieve anything I know is untrue from experience and basic science principles. The paper may have some merit, but that statement is untrue. If I showed you a paper with an untrue statement that you could understand I doubt you would accept it at face value. At least I would hope not, whether you read further or not. If it stated that a planet of 10,000 miles diameter could stay in orbit, but only if it was between 100 and 200 million miles from a star, would you accept it "provisionally" at face value? Do you really need to read further to find that statement outright wrong or not really what they meant?

In the background where there is more breeze the boundary layer of air is turbulent enough to break the surface tension on the water to some degree. In the foreground the boundary layer is laminar.

I haven't read the paper but...if you choose to believe that the experimental data might support: "These induce a lifting force on a cylinder in the path of these eddies - but only if the two have the same diameter and the second cylinder is three to six diameters away from the first" I'm guessing they don't have enough data to prove that statement. I don't think you should take it at face value, even temporarily. (It may very well be a misquote but you go ahead and believe it "provisionally", so as to avoid any personal incredulity)

No idea on their methods, but I find that particular statement in their conclusion to be incredible...or perhaps something was lost in translation.

Big plane compared to most. Brave bunch of pullers to leap in ahead of the plane and trolley! Is there some way to use some of their potential energy from the vertical fall to further increase the horizontal plane speed? (you don't want them swinging back toward the pier though) It would seem that the most critical thing is that the "take off" speed is above stall speed of the wings, or you would get less lift and high drag. Easier in a headwind than tailwind, though significant headwinds would have higher drag. The advantage of the diving down initially is that you increase velocity while initially requiring less lift. The pullout stage would be critical as most lift would be required at that point, so it should not be too abrupt. As long as you are not close to stall but in efficient gliding range of speed a flatter initial flight as you suggest might be good. This is where pilot skill would make a big difference in getting the glide right. Turbulence would be a factor in trying to achieve an efficient glide and any crosswind would require lots of control for the pilot Maximizing velocity is probably the biggest factor along with efficient aerodynamics. Can the trolley be lengthened and the pilot accelerate forward with respect to the trolley? Run or bike or something that could be jettisoned? maximise the trolley speed and maximse the plane speed wrt the trolley type of idea.

Fair enough, but I highly doubt the accuracy of this statement at face value (bolded by me) "These induce a lifting force on a cylinder in the path of these eddies - but only if the two have the same diameter and the second cylinder is three to six diameters away from the first"

Hopefully we will offer googleresistant comments, questions and answers. Green Cow flax, or something similar, can easily be googled as can any specific competition rules or references to the event (I copied your r e d b ... etc... pasted in Google and it comes up, so if you are serious you may want to delete that) I looked at some youtubes of past events. Is the 6m the total starting height of the object above the surface of the water? It looked higher, plus additional height seemed to be gained by a moving platform on the most successful entry which then seemed to trip, sending the object ahead and downward before release. As maximum kinetic energy was gained approaching the water surface it then pulled out of the dive aerodynamically getting lift from the wings. It should have stayed parallel to the water but over corrected or it would have gone further than the 200 meters it flew. Getting low fast and staying there would help as you get additional lift from a ground effect closer to the ground or in this case water. Is your goal to beat the 200 + 7 meters? Or just want a decent showing? You want to convert that potential energy to kinetic energy as efficiently as possible and can add further kinetic energy by pushing or pulling. Any other sources of energy available or allowed? (elastic bungy etc) Since the driver (is he a lightweight athletic and skilled pilot or hang glider?) is a good portion of the weight of the object, can he run or perhaps bike to top speed and not just be pushed or pulled by others? Can he drive a propellor? (that would be tricky and not nearly as efficient on the platform vs biking against the platform but may or may not be effective in the air) How long is the platform/runway/pier? Can you use a slingshot effect? pulleys?

Like this? http://www.tecaeromex.com/ingles/RB-i.htm

The steady state theory could not account well for the CMBR, but it was not inconsistent with expansion after hypothesizing matter production. The Big Bang seems to have less problems though I would not rule some form of either (or neither) in or out. A lot of assumptions are made for each, and the Big Bang's seem the most reasonable but even expansion is a stretch (pun intended) as we only get data from our one little point on an unknown Cosmos/Metric/Manifold/Whateveritis.

This is clearly wrong (unless I have the context wrong) . Any cable diameter (at the right windspeed) will shed vortexes in oscillatory fashion giving rise to lift in one direction, at right angles to the cable and flow, and then the other.

Expansion of space is not the same as movement in space. Given that: For a certain spatial separation of points and beyond are we (universe "now" wrt cmbr) not expanding such that those points are increasing their separation at a rate faster than light speed?

Basically yes. In fact if you had a "containment shell" around it that would not allow any energy (say photons) to escape, it would be indistinguishable from mass with the same containment. That would effectively still be it's mass.

As long as you are not designing anything I might use or come across, I'm fine with that.

What is considered frictional resistance or drag is somewhat arbitrarily defined, but the force of friction is a dissipating force brought about by movement in shear. So if you drag something along the ground that is friction. If you look at it on a different scale their are impacts involved that you may not consider completely friction in isolation, but it all gets lumped in as friction. In hydrodynamics of ships, skin friction is the shear force effect on the surface of the ship. Pressure on the front of the ship that displaces the water upwards creates a wave. This energy generally gets dissipated and lost but is not considered friction (no shear losss or viscous effects, at least not immediately). The pressure also displaces water down and to the sides. Some of that energy gets returned to the ship. The portion that is lost is form drag. Friction can be involved in the dissipation of some of that energy but to the ship that is not considered frictional drag. If you drive into the back of a bus and metal crumples on impact internal friction in the metal is involved (the metal heats up), but for you that is not friction, but if you drive and scrape along the side of the bus thats friction to you even while you are transferring some of your momentum and kinetic energy to the bus. So it is not always clearly defined but it is clearly not everything that is a resisting force to motion.

Form (pressure) drag is not friction. Wave resistance is not friction. Both resist the objects motion.

Pressure wave losses are not the same as friction losses. In the example I used in post 5 for a rounded body moving through a idealized frictionless fluid there are no surface effects or gravitational waves (think ideal submarine at depth). If there was (same submarine at surface) there would be drag even for a frictionless fluid. I do not know how that would work a superfluid. I suspect at the boundaries (including the surface of an object moving through it) of the fluid the collision rules described could not apply. (I don't understand that part, or how these collisions can work...I'm better with billiard balls!)

I'm grasping, but... Think of a closed container of water sitting at ambient temperature...essentially nothing happening. It is at some pressure and thereby exerting forces on the container. Where is the friction? Now open it up and drag your hand through the water...friction! I know this is obvious to you, but just trying to understand what you are thinking... ...my only thought is that if you invoke the second law of thermodynamics, the "you can't break even" part of "you can't win, you can't break even, and you can't get out of the game..." then you may be claiming that a "perfectly frictionless" process is impossible. Outside of that I don't see where you are coming from though you seem to be repeating the same claim.

Why would it mean that? Unless I'm getting it wrong, a very restricted form of acceleration/displacement of the particles is being described...but not no acceleration or displacement.

There also is some threshold before any damage occurs and this would depend upon the weapon and any protection/armour where it makes contact. There is a reason some weapons are sharp and others blunt.

...and this is all that happens in a superfluid?...every collision is not just elastic, but there is no net energy transfer in each collision? (this seems statistically unlikely, does it not? or is there some mechanism that makes it happen?) Assuming I have this right, that could only be with respect to one inertial frame only, correct? The magnitude of the momentum must have changed when measured in others.