Mike Dunlavey
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 8h comment Intuitive explanation for lower pressure above airfoil When you say "Bernoulli does not explain wing lift" are you by any chance confusing Bernoulli with the "equal transit time fallacy"? The Bernoulli principle isn't wrong - what's wrong is the way it is typically used to explain wing lift, assuming air parcels are re-united at the trailing edge. I've found this to be the clearest explanation. 8h comment Intuitive explanation for lower pressure above airfoil @MrYouMath: I'm not sure, but I think you're onto something. 12h comment Intuitive explanation for lower pressure above airfoil @MrYouMath: I agree with this explanation, but I would put it in simpler terms. It's just a consequence of $F=ma$. There is a velocity difference if and only if there is a pressure difference. One implies the other. As far as incompressibility is concerned, all that means is we're dealing with speeds well below the speed of sound. It does not mean the fluid is stiff. Apr 29 comment Physical explanation of Pascal’s Law Google "lever". Apr 28 comment How can I understand $\mathrm ds^2 = -c\,\mathrm dt^2 + [\mathrm dx-v_s(t)f(r_s)\mathrm dt]^2 +\mathrm dy^2 +\mathrm dz^2$ in the simplest way? @Nihal: Why not start now? It's fun. Apr 28 comment How can I understand $\mathrm ds^2 = -c\,\mathrm dt^2 + [\mathrm dx-v_s(t)f(r_s)\mathrm dt]^2 +\mathrm dy^2 +\mathrm dz^2$ in the simplest way? @Nihal: Yes, but not difficult. $d something$ just means "an amount of something that is small enough that you don't have to worry about curviness". Like suppose you have two points on a curvy line close together but not the same point. If the horizontal distance between them is $dx$ and the vertical distance is $dy$, what is the distance on the line between them, $ds$? It's just the square root of the other two distances squared and added together, right? Apr 27 comment Centripetal force: if radius decreases, does ANGULAR or TANGENTIAL velocity change? @Al: I doubt your first point. On the second point, I've been wondering that myself. I'm supposing some kind of infinitessimal argument would clear it up, but I haven't been able to give it enough thought. Apr 26 revised Centripetal force: if radius decreases, does ANGULAR or TANGENTIAL velocity change? I think that this addition adds to quality of the answer. Apr 26 reviewed Edit Centripetal force: if radius decreases, does ANGULAR or TANGENTIAL velocity change? Apr 26 revised Centripetal force: if radius decreases, does ANGULAR or TANGENTIAL velocity change? I think that this addition adds to quality of the answer. Apr 26 revised Centripetal force: if radius decreases, does ANGULAR or TANGENTIAL velocity change? added 82 characters in body Apr 26 revised Centripetal force: if radius decreases, does ANGULAR or TANGENTIAL velocity change? deleted 5 characters in body Apr 26 revised Centripetal force: if radius decreases, does ANGULAR or TANGENTIAL velocity change? added 305 characters in body Apr 26 answered Centripetal force: if radius decreases, does ANGULAR or TANGENTIAL velocity change? Apr 21 comment What amount of force could be created by a person “swimming” in air? Two points: 1) birds do it. You're not much of a bird, but the idea should still work. 2) Force is not just momentum, it is momentum per time. Apr 20 comment flow rate measurement of a fluid It's just a wedge. It travels in a circle, but it's still a wedge. Apr 18 comment Does physics claim that every possible world has or will exist? @user3293056: These interpretations can be useful. When I dabbled in quantum computation some years ago,the many-worlds interpretation was a really nice way to think about what was going on. Apr 16 comment When does the shock occurred? 3-when the speed of the local flow over the airfoil exceeds Mach 1. This first occurs on the upper surface of the airfoil when the speed of the aircraft is still less than Mach 1. Apr 12 comment Why do water waves with longer wavelengths travel faster? @veronika: I think you might have it backward. For sailboats with displacement hulls, the length of the waterline determines the wavelength of the wave it generates, and that affects the maximum speed the boat can go. Apr 9 comment Plane landing into a tunnel If you could see the air around an airplane, like if it flies through smoke, you would see that the weight of the airplane causes the air to be pushed/sucked downward. This forms two large rotary circulation patterns, one from the end of each wing. This persists behind the airplane in the form of a wake, just like a speedboat. Nothing about flying in a tunnel prevents this. Of course, if there is a second plane flying behind the first, the wake is a problem to be avoided, but that's true, tunnel or not.