7,200 reputation
1625
bio website en.wikipedia.org/wiki/…
location United States
age 70
visits member for 3 years
seen 10 hours ago

BS Mechanical Engr.
PhD CS(AI)
CS Prof (4yr)
Numerous consulting jobs.
15 yr at http://www.pharsight.com
Published book on CS & several articles
4 kids, 2 grand
Pilot(student)

P.S. The picture is a Beta-prime distribution. It shows the program speedup factors you can get if you see a problem twice in 2, 3, 4, and 5 samples.


May
11
comment What is the exact cause of flow separation in a viscous fluid?
Are you asking about the Kutta condition?
May
9
comment Why doesn't this model plane fly?
@Pranav: Good point.
May
9
comment Why doesn't this model plane fly?
@Pranav: This video shows what happens when the loading shifts aft.
May
9
comment Why doesn't this model plane fly?
@Pranav: yes, and the correct situation is - the CoG needs to be forward of the CoL. Moving the wing back, or putting a small weight on the nose, should enable it to glide stably. The reason is - the tail lifts down, so lower speed drops the nose, which increases speed. Higher speed raises the nose, which reduces speed. If the CoG and CoL are at the same place, it will have no stability in speed, and will fly a choppy up and down motion. If the CoG is behind the CoL, it could very well back-slide.
May
9
comment If we connect a source of electricity in a large water body ,will it be dangerous?
+1 This is one of the most useful answers I've seen here.
May
9
comment Why doesn't this model plane fly?
First try it as a glider. The shape of the wing doesn't matter that much. What matters is the balance. The main wing has to be far enough back so it is nose-heavy, and of course it needs a tail. Then if you throw it fast enough, it will glide. Then if you give it a propeller it will go farther.
May
9
comment Why doesn't this model plane fly?
@John: Right. In a back-slide. Planes normally have the center of gravity forward of the center of lift. Then the tail pushes down to keep the nose from dropping. It's called decalage.
May
6
comment When rotating a liquid-filled jar what determines how much force goes to spinning the specimen floating inside?
I see two cases. 1) spinning the cylindrical container about its central axis. In that case viscosity is the only effect. 2) If the container has some air above the liquid, and the container is not being rotated but is being cycled around an off-center axis (like swishing the coffee in a cup without turning the cup), that is different, and causes much more powerful rotation of the liquid.
May
3
comment Could you blow up a barrel (closed container) using a straw and water?
@harogaston: I'll vote it up for you. There's hardly any math involved. It's just a matter of pressure. At what pressure (psi) does the barrel fail? It might not take much, and it might be less than what the straw can hold.
May
2
comment Snowmaking in the tropics - an estimate of water evaporation
It's common in outdoor spaces in Texas, Arizona, and other warm locales to put misters outdoors. As soon as it hits you it evaporates and cools you off. Of course, if the weather is really humid it doesn't work so well.
Apr
30
comment Stop Motion 3D model of airflow over an airfoil
See if this is helpful.
Apr
22
comment Can one pump water without providing an external source of energy?
Is there enough flow in the canal that you could build an undershot water wheel? or maybe a windmill water pump?
Apr
22
comment Why do clouds fly?
All I know is what I learned in pilot training (plus undergrad thermo).
Apr
21
comment Why do clouds fly?
You're on the right track. The flat bottom is where the temperature falls below the dew point. However, air is not always rising in thermals - that's called unstable air, as opposed to stable air. When the environmental lapse rate exceeds the adiabatic lapse rate, the air is unstable. See Convective instability.
Apr
14
comment What is a linear probability density function?
@gj255: What you would do is take your sample of n velocities and sort them to get an empirical distribution. Then see which $av+b$ line fits it best.
Apr
13
comment Duration of Satellite orbit in the shadow of the Earth
In the past, I've been guilty of giving complete answers to homework questions, rather than nudging the OP in the direction of figuring it out.
Apr
12
comment Why Don't Birds Stall?
Stalling is an effective way to dissipate excess energy. (That's why cars have brakes.) Small airplanes stall when they land. I suppose birds do too.
Apr
11
comment How much weight is lifted from each side?
None of the heights matter. What does matter is how the weight is distributed. Is the weight more toward the front, or more toward the back? Is it concentrated in the middle, or is a lot of it in the very ends? Are you lifting both ends at the same time, or one end at a time?
Apr
10
comment On the Existence of Interstellar Meteoroids
Maybe you could provide a link to the video, and what is 36:45? Thanks.
Apr
10
comment Why is there this asymmetry between the two foci of an orbital ellipse?
@EmilioPisanty: Thanks. You're right - except that the center of the cone is not the center of the ellipse, except for a circle. Easiest way to see that is to cut the cone on a plane almost, but not quite, parallel to the edge, so as to create an ellipse of very high eccentricity.