December 13, 2011

Wants to Develop a System

Mr. Seykota, I am looking to develop a trend following system for currencies.

My background, I already have a profitable prop trading track record, and agree with the existence of trends.

Please let me know.

Thanks,

December 20, 2011

Bernoulli

Ed,

I found your web site during a search for the spool and card demonstration. Your radial flow explanation was helpful here.

I looked at the rest of your web site and noticed some comments about others claiming that Bernoulli can be used to explain lift on an air foil. There may be a few web sites making this claim, but actual programs such as XFOIL, use a simplified form of Navier Stokes equations to generate polars (the coefficient of lift and drag versus angle of attack and Reynolds number based on an airfoil shape). This is a complicated process that goes way beyond the simple equations of Bernoulli.

Despite some misleading web-sites about how lift is created, the experts that actually designing airfoils (such as the author of XFOIL, Mark Drela a professor at MIT), understand what's involved.

My interest in this is due to my hobby with radio control gliders. Some of the aerodynamic experts, like Mark Drela and Philip Kolb, design some of the high end contest model gliders, including creation of their own airfoils.

December 20, 2011

Bernoulli

Ed,

I'm a retired programmer, my last jobs involved embedded firmware in computer peripherals, which use simple pre-emptive multi-tasking operating systems (event driven). I specialized in RS ECC (Reed Solomon Error Correction Code), IDE / SATA interfaces, and wrote a few devices drivers (Windows NT and Zenix, a variation of Unix). Going back to the 1980's and before, I specialized in operating systems and device drivers for mini-computers.

As mentioned in my previous email, my interest in aerodynamics is due to my hobby with radio control gliders.

In my previous email, I left out Helmut Quabeck, another professor that designs rc gliders and airfoils (the HQ series). A short list of designers and their primary model glider names:

-Mark Drela - Supra
-Philip Kolb - Pike Perfect
-Helmut Quabeck - Icare / Icarus

There are others, but I don't recall their names at the moment.

This web site has a large list of airfoils: http://tracfoil.free.fr/airfoils/indexE.html

My interest in aerodynamics is due to my hobby, and also my curiosity about aircraft in general. Although I don't fly full scale aircraft, I know a few rc hobbyists that do fly full scale gliders.

Over the years, I've been trying to sort out the various web-sites on aerodynamics. Each seems to offer a different bit of the total picture.

Getting back to the point about Bernoulli principle and lift, it seems that Bernoulli principle as it applies to wings states the obvious fact that air accelerates from higher pressure zones towards lower pressure zones, and the equation shows a relationship between pressure and speed during the transition in a somewhat idealized model.

One issue that many of the web sites don't explain well or at all is how a wing adds energy to the air, resulting in downwash related to lift and some forward velocity of the air related to drag. It would be similar to the exit velocity as explained in the NASA article about propellers, except that for a wing, the pressure jump and exit velocity is smaller, and a wing doesn't operate in it's own induced flow like a propeller or helicopter when hovering.

http://www.grc.nasa.gov/WWW/K-12/airplane/propanl.html

I wonder about things like how closely induced drag times air speed (power consumed to produce lift) translates into power added to the air related to downwash.

Sorry for the short novel, I only meant to ask about the issue you have with Bernoulli and lift, versus my own small knowledge about the actual programs that produce polars for airfoils.

December 20, 2011

Merry Christmas

Hope you have a wonderful Christmas and New Year with family and friends.