Fractional Height in Input-Files

Dear Community,

in the Input-Files for tower/blades for FAST or MODES, there is a column with the fractional height of the sections. I do not understand why there is the same number of rows and elements. The way i see it, there must be 1 extra row (because 3 elements have 4 nodes; two inner nodes and 2 outer nodes).

An example: I have 3 sections with data, lets say a tower. This results in a 3-row input file with fractional distance from 0 to 1:

Fract. | MassDens. | Stiff.
0.0000 | 1300 | 7000E4 (SEGMENT 1)
0.3000 | 1000 | 5000E4 (SEGMENT 2)
1.0000 | 750 | 2000E4 (SEGMENT 3)

This would be a compatible input file. Now, how do i read it? Does that mean that Segment 1 resembles 0% to 30% of the total length, segment 2 30% to 100%? what does segment 3 stand for in this context?

I hope my problem is understandable. If necessary, I will provide a drawing in order to make myself clear.

Best regards,

M. Müller

Dear Matthias,

I’m not sure why you say,

because this is not true. In FAST, Modes, and BModes, the stations for specifying structural properties are independent of the number of elements used by their internal calculations. So, e.g., specifying 3 input stations does not imply that there are 2 elements or 3 elements. Instead, the structural properties specified at the input stations are interpolated to the nodes/elements where the actual calculations take place. The value of “Fract” is the nondimensional distance along the beam where Fract = 0 corresponds to the blade root or tower base and Fract = 1 corresponds to the blade tip or tower top.

I hope that clarifies things.

Best regards,