Creating a Computer Flight Model: Best Starting Place for Aerodynamic Theory

[metiscus]

Lately I've been playing around with the idea of creating a very simple flight simulator as a hobby, just to learn the mathematics behind subsonic (think cessna) aerodynamics. I'm a computer engineer by training, so I am not afraid of mathematics but my current exposure to the dynamics portions of this topic is limited. I have archived and read a large number of the NACA reports from the 1940s and I have a book that contains dozens of the NACA airfoils along with the tabulated curve information. I've got a pdf copy of the DATCOM as well as Andersons book on aerodynamics. I have a very good understanding of 3d mathematics, at least as it applies to computer graphics.

So my question is, what is the best starting place to create such a toy program as far as the aerodynamic theory goes?

I would like to make utilization of actual airfoil data, and have my simulation be semi-realistic. I've started reading up on thin-airfoil theory but there is also the method of using panels. Effectively, if someone could take a few minutes of their time to direct my efforts to a theory of flight that suits my mathematical / physical capabilities, I would be thankful. Please note that I want to model all 6 degrees of freedom, a simple 2d lift-drag wing model is not really what I am looking for. I know that body aero forces are important too, so bonus points if you can give me ideas on how to deal with those as well..

 

[mgb_phys]

http://www.flightgear.org/ is an open source flight simulator, IIRC you can write plugins to model the aerodynamics of particular aircraft, a lot of the users are heavily into extremely detailed performance modeling rather than the pretty pictures

 

[James98765]

I'm not sure if this program is too elementary for what you are trying to do but basically its a calculator for aerodynamics. This program is a java application and it allows you to select from a variety of airfoils and you can change the angle of attack and airspeed to determine the net force of lift. You might consider checking it out:

http://www.grc.nasa.gov/WWW/K-12/airplane/foil2.html"

-James

 

[rcgldr]

Source code is included for this air foil program:

http://web.mit.edu/drela/Public/web/xfoil/

 

[Cyrus]

Lately I've been playing around with the idea of creating a very simple flight simulator as a hobby, just to learn the mathematics behind subsonic (think cessna) aerodynamics. I'm a computer engineer by training, so I am not afraid of mathematics but my current exposure to the dynamics portions of this topic is limited. I have archived and read a large number of the NACA reports from the 1940s and I have a book that contains dozens of the NACA airfoils along with the tabulated curve information. I've got a pdf copy of the DATCOM as well as Andersons book on aerodynamics. I have a very good understanding of 3d mathematics, at least as it applies to computer graphics.

So my question is, what is the best starting place to create such a toy program as far as the aerodynamic theory goes?

I would like to make utilization of actual airfoil data, and have my simulation be semi-realistic. I've started reading up on thin-airfoil theory but there is also the method of using panels. Effectively, if someone could take a few minutes of their time to direct my efforts to a theory of flight that suits my mathematical / physical capabilities, I would be thankful. Please note that I want to model all 6 degrees of freedom, a simple 2d lift-drag wing model is not really what I am looking for. I know that body aero forces are important too, so bonus points if you can give me ideas on how to deal with those as well..

I just recently made a 6DOF on a cessna 172 for NASA. I'll just say you are in for more than you think, and that you cannot use airfoil data for an entire airplane.

If all you want to do is have basic fun, buy Microsoft Flight Simulator or download Flightgear. If you want a realistic simulator, look elsewhere (i.e. design your own).

To do a full 6DOF requires a substantial amount of work. (People have PhD's in doing 6DOF)

What you need are the stability & control derivatives from wind tunnel and/or flight test data for anything remotely serious. Most simulators like Flight Gear or Microsoft use linearized models about a single trim condition (which is crap).

 

[LeonStanley]

Hi Metiscus
Please remember all the other variables if you are going to develop a flight sim. You'll need a decent weather and wind modeller. Understand the relationships between altitude, temperature, pressure, true airspeed, indicated airspeed, ground speed, and performance of engines etc.
If you were in the tropics, and the temperature on the ground was 100 F, what do you expect the temperature would be at 10000 feet? And what would be the dew point?

Answer: around 50 F @ 10000 ft, dewpoint around 26 F in fine weather, ratio between IAS and TAS roughly around 1.2 for a cessna

If you are flying in freezing conditions, how long would it take for the "boot" to freeze up if you forgot to hit the anti freeze switch?

You'll need to program all that in.

 

[Cyrus]

Hi Metiscus
Please remember all the other variables if you are going to develop a flight sim. You'll need a decent weather and wind modeller. Understand the relationships between altitude, temperature, pressure, true airspeed, indicated airspeed, ground speed, and performance of engines etc.
If you were in the tropics, and the temperature on the ground was 100 F, what do you expect the temperature would be at 10000 feet? And what would be the dew point?

Answer: around 50 F @ 10000 ft, dewpoint around 26 F in fine weather, ratio between IAS and TAS roughly around 1.2 for a cessna

If you are flying in freezing conditions, how long would it take for the "boot" to freeze up if you forgot to hit the anti freeze switch?

You'll need to program all that in.

All that is just fancy garnish. The heart of what you want is the aerodynamic stability and control parameters along with a good engine model. That is where MSFS and flightgear fail miserably.