# Drag coefficients/Moments along Pitch, Yaw and Roll

Hello,

I am simulating the drag forces/coefficients for a underwater vehicle that is cylindrical in shape. While the linear drag terms/Forces along X, Y and Z were straightforward to simulate and find out using tutorials, I have no clue how to find the same for the three orientations axes namely Roll, Pitch and Yaw. I did see Moment coefficients and How To Analyze the Pitch, Lift, and Drag Coefficients | SimScale pages but what is mentioned in them doesnt seem to match what i want.

Hello! What you can do is to obtain the total moments around all three axes by creating Forces and Moments result control, then you can convert them into related non-dimensional coefficients by using the relations given here.

Best regards!

Hi Kaany,
Thanks for the reply. A few things if you could clarify. The menu in the result control force and moment coefficient does not have any section for pitch axis. Also I have setup my model as per the figure attached. Is my notion of reference length correct? or am i supposed to take the radii?

My sim is here: https://www.simscale.com/workbench/?pid=4379222742327109494

Thanks again,
Milind

Hello!

In a general sense, it is a good idea to check articles/papers involving the same application to see what the common choices for reference area/reference length are.

From looking at the geometry, the values that you are using look ok to me, but it’s still a good idea to check published material.

PS: when it comes to reference area: usually it will be a projection of the frontal area if drag is the most important parameter (e.g. for a car) and a projection of the top area if lift is the most important parameter (e.g. for an airplane wing profile).