As far as I understand one can see objects that are not, in principle, visible with naked eyes (eg Jupiter at noon). It is a known fact that telescope does not amplify surface brightness. So I can understand why one can see stars in telescope at the noon, (angular size of a star is practically...
Why are planets visible in telescope in daylight?
As far as I understand both 1) total light flux from the planet 2) and that from the atmosphere receved by scope are proportional to the aperture area. So why then we can see the planets?
And I have realted question. I am my city humidity and...
Seems that was a silly question?
The answer is indeed elementary: Take any divergence free function of (x, t) that ends as initial data at some t_0 and is zero at t=0. Then substitute it into the NS equation and get f(x,t) and p(x,t).
The problem is choosing the divergence free function, but...
Hello,
Recently it has been announced on the web that a progessor from Kazakstan has solved the Clay institute millenium problem showing existence of strong solution of Navier-Stokes (see eg https://github.com/myw/navier_stokes_translate).
I do not know if it is true or not, but reading...
I am already using X-foil or XFLR5 (latter implements VLM and 3D panel in conjunction with x-foil polars). This was XFLR5 which gave efiiciency>1 for one of the planforms.
An hour ago I found interesting thread in rcgroups modelling science forum which confirms shat rectangular planform could...
This is exactly the reason for which I was studying this wing optimization. I designed and constructed several rc gliders and was trying to improve min. sink rate for the next one choosing optimal planform and sections along the span. It seems that for slow floaters with small to moderate aspect...
Do not think about embedding, the tangent bundle just a way to parametize positions and velocities In case of a circle these are just two numbers, one of which is a periodic coordinate.
Just take this formally: Consider the pair (coordinate, velocity). In case of a particle on a circle your configuration space is one dimensional circle with angular coordinate phi. Let the particle velocity be omega. In this case you just have a pair of numbers (phi, omega) where pair (phi+2pi...
Indeed, notion of circulation distribution along the span implies that the wing itself is a line, so for a wing with finite aspect ratio all these notions are just asymptotic approximations. Within the lifting-line theory the proof is an easy excercise. However, for a wing with the finite chord...
I am well aware of all that, but this does not give answer to my question.
These wiki articles do not go beyound lifting-line theory except one of them says: "the pure elliptical shape as a superior planform may be a myth.[citation needed]" with no citation or proof.
Let me reformulate the...
Use XFLR5 program, it is free and has user-friendly interface, the neutral point will be found with few percent precision. You will also get drag polars and even stability analysys if you want.
I have designed and constructed several gliders using Xfoil and XFLR5.
You can also get preliminary...
Hello Everybody,
Span efficiency factor appears in the lifting-line theory of Prandtl describing Lift and vortex drag of a finite wing. According to this theory, the most efficient wing is an elliptical one and, roughly speaking, the span efficiency factor defines an efficiency of a given wing...