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1d
answered Trouble understanding a formula in Turbulence
1d
comment Trouble understanding a formula in Turbulence
Another hint -- production = dissipation.
2d
comment Stokes-Einstein Relationship to find time taken to diffuse $x$ distance?
@lemon I was thinking about gasses, didn't even consider that Navier-Stokes was about liquids too. Obvious in hindsight, but didn't think of it up front.
Apr
27
comment Converting between matrix multiplication and tensor contraction
@Dargscisyhp Just out of curiosity, if you were to define it as a matrix multiplication, how would you do a computation besides to crank through the indexing by hand? Isn't every actual computation of a matrix multiplication where we do the whole "row by column" thing over and over just cranking through the indexes?
Apr
27
comment Can you have a problem with a Dirichlet boundary condition but with waves that reflect off the boundary?
@csss There's a difference between heat equations and wave equations, as well as steady vs unsteady equations. So you have be careful generalizing what BC's do in each equation.
Apr
27
answered Can you have a problem with a Dirichlet boundary condition but with waves that reflect off the boundary?
Apr
26
comment How can an electron fake a jet?
An experimental question ended up on the Hot Network bar! It's a good day.
Apr
23
comment What phase is water at 262C and 15bar?
Okay, so let's break this down. Are you having trouble reading the phase diagram -- like when you pick the conditions you listed, you can't physically find them in the diagram? Or are you having trouble interpreting what it means when a conditions falls on the black line between two or more phases? Can you be maybe more specific about what isn't clear for you when you look at a phase diagram?
Apr
23
comment What phase is water at 262C and 15bar?
Have you even looked anywhere for this? The phase diagram on Wikipedia is pretty clear.
Apr
22
comment Which direction does the air/fluid move in each segment?
So being colorblind, I have no idea what your figure shows.
Apr
1
comment What prevents this magnetic perpetual motion device from working?
If you want it deleted, press the flag button and use the custom flag for the moderator. Tell them you would like it deleted. Do not deface the post.
Apr
1
revised What prevents this magnetic perpetual motion device from working?
rolled back to a previous revision
Apr
1
revised What prevents this magnetic perpetual motion device from working?
rolled back to a previous revision
Apr
1
revised What prevents this magnetic perpetual motion device from working?
rolled back to a previous revision
Mar
31
awarded  Necromancer
Mar
30
comment H2O Fuel of the Future
@CuriousOne I thought it was more about something like a water fuel-cell -- split it into hydrogen and oxygen with a battery or something, burn both and get energy out with only water as the product. Not that it's any less misguided than steam engines of course...
Mar
27
comment Is it possible that viscous flow has a higher lift to drag ratio than inviscid flow?
Also, it's possible however you are computing drag does not include viscous effects and so the drag for the viscous case is lower than it should be. Some advice for working in CFD -- always know what equations and methods are used to produce the numbers you see; you can't physically justify anything without knowing how you are computing it and what is included or not included.
Mar
27
comment Is it possible that viscous flow has a higher lift to drag ratio than inviscid flow?
Without knowing what factors are included in calculating the drag, I can only guess (and this is why I won't post it as an answer). But lift decreased, this is expected. Drag went down also -- most likely, adding viscosity smoothed out the small shock that would form so it is no longer there. Viscous drag increased, but wave drag (the only kind you can get in inviscid flow) decreased by a lot because viscosity killed the only wave that shows up. Or there's a bug somewhere. Or you're computing drag incorrectly.
Mar
27
comment Is it possible that viscous flow has a higher lift to drag ratio than inviscid flow?
That doesn't answer my question... AUSM is used to compute the flow field. How are you computing the drag from the resulting flow?
Mar
26
comment Is it possible that viscous flow has a higher lift to drag ratio than inviscid flow?
How are you computing drag?