Von Karman Wind Turbulence Model

Hi,

I have a question regarding the input V of the von Karman/Dryden turbulence model in Simulink. The documentation states that V is the speed of the aircraft. My question is: Shouldnt it be the airspeed/relative speed of the aircraft with respect to the wind field? And second question, in the model V is a scalar and the same for all three velocity components. Shouldnt V also be a vector?

Kind regards,

Sebastian

Answer 1

[Jim Riggs]

V is the true airspeed.

V is a scalar, and is used to calculate the scalar components of the turbulence field.

The documentation for the Von Karman turbulence model is here:

https://www.mathworks.com/help/aeroblks/vonkarmanwindturbulencemodelcontinuous.html

It says that the model is an implementation of the MIL spec 8785c. You can download the MIL spec here:

http://everyspec.com/MIL-SPECS/MIL-SPECS-MIL-F/MIL-F-8785C_5295/

(see section 3.7 Atmospheric disturbances)

This document looks useful too:

http://contrails.iit.edu/files/original/AFWALTR81-3109.pdf

[Sebastian]

Thanks, for clarifying this. However, I still do not understand completely why the same V is used for the calculation of all three components of the turbulence field. Intuitively, I would first transform the airspeed vector into the same coordinate frame as the turbulence field and then use the individual components as an input to the three filters. But maybe I‘m missing an important assumption here...

[Jim Riggs]

You should look at the documentation for the method. You will see that the method calculates individual components.