Reynolds Number and Weight

[doug.hunsaker]

Question from user:

I am just beginning to explore the software you and your team have created.

I should start by stating that I am a Xfoil & AVL user.

Your software certainly makes the geometrical mock up of the craft easier to both perform and visualize, but I am left wondering the following:

How does the user define the Reynolds number?

How is the total weight of the craft and its distribution taken into account?

Thank you have any insight you may offer.

[doug.hunsaker]

The Reynolds number is accounted for through the use of the airfoil coefficients. The web version of MachUp assumes linear aerodynamics (i.e. You specify lift slope, moment slope, etc.). The downloadable version of MachUp is command-line, and allows you to use nonlinear airfoil data sets to specify your airfoil aerodynamics. These methods of setting airfoil properties allow you to change the Reynolds number by changing the airfoil coefficients. Make sense?

The weight distribution is not accounted for, but the location of the center of gravity can be specified. This allows you to determine aerodynamic stability, control, and damping derivatives.

Best,

-DH

[doug.hunsaker]

User:

Okay thank you for clarifying.

Reynolds number, and therefore velocity, is set through coefficient specification.

What if I instead wanted these coefficients to be my outputs instead of my inputs? 

[doug.hunsaker]

MachUp is not set up to have these as outputs instead of inputs. I would suggest writing a spreadsheet to calculate Reynolds number, or using the atmospheric properties calculator available here: http://www.aerospaceweb.org/design/scripts/atmosphere/