Hi All,

I am currently testing the AeroDyn v15 Standalone version. I found something interesting with the results. Any help is greatly appreciated.

I did a series of tests on NREL 5MW blade with 10 rpm initial rotor speed and 10 mps steady uniform wind (zero precone, zero shearExp, zero yaw, and zero pitch). The dT is 0.03 sec with total Tmax 12.00 sec

Case 1: ShftTilt=0, yaw=0, Precone=0

- The azimuth angles DO NOT very with time-step. It is constant at their initial state (Blade 1 at 0 deg, Blade 2 at 120 deg, Blade 3 at -120 deg)
- Therefore, all the Vrel, Phi, Alpha (AoA), Cl and Cd are constants in this 12.0 sec simulation

Why the azimuth angles do not change with time? Does it mean the rotor is not rotating? Please advise.

Case 2: ShftTilt=20, yaw=0, Precone=0

- Blade 1 initial Azimuth angle starts at -90 deg.
- The azimuth angles now VARY with time-step, rotating CW. direction.
- all the Vrel, Phi, Alpha (AoA), Cl and Cd are NOT constant in this 12.0 sec simulation

Case 3: ShftTilt=-20, yaw=0, Precone=0

- Blade 1 initial Azimuth angle starts at 90 deg.
- The azimuth angles now VARY with time-step, rotating CW. direction.
- all the Vrel, Phi, Alpha (AoA), Cl and Cd are NOT constant in this 12.0 sec simulation

Based on the picture below, AoA of each blade should change in both Case 2 and Case 3

However, the AeroDyn results show that B1 AoA are the same for both Case 2 and Case 3 when the B1 is at azimuth angle = 0. The below picture show the B1 AoA at azimuth =0 and after one full rotation. All the line overlay on each other because they have the same value. Notes that the same thing happened for tilt =0, yaw=20 case.

Here are better pictures to understand the issues. The pictures show B1 AoA of a full revolution (azimuth angle starts from 0 to 360).

From my understanding, Case 2 is correct because AoA changes and its symmetrical to the vertical axis. Case 3 should have changes in the bottom area, but the AeroDyn result shows they are the same.

I have change dT, skewMod, and other parameter, but it still provide similar results. I do not understand what is going on here.

Here is the download link of my driver code, primary input code, and outputs of each case. The blade data is the same as NREL 5MW for its example.

Case 1: “T0_Y0.1.out”

Case 2: “T20_Y0.1.out”

Case 3: “T-20_Y0.1.out”

Case 4: “T0_Y20.1.out”

dropbox.com/sh/x474qykko60g … 5Jusa?dl=0

Any input or help is greatly appreciated. Thank you!