Dear all,

I am using OpenFAST to calculate the aeroelastic response of a rigid sail that looks like a rectangular (36m span and 9m chord) wing with a composite glass/carbon fiber structure.

First, I needed to validate the use of the OLAF module. To adapt this tool to my case, I modeled 1 blade without rotation. I have access to the CFD results of the 2D aerodynamic coefficient that I used in the input file of the wing data. Then I ran several 3D aerodynamic force measurements by iterating over the PropagationDir parameter of Steady InflowWind (10 m/s). I compared these results to 3D wind tunnel tests.

Our goal was to match 3D results of OLAF to our Wind-Tunnel results. But our wing profile is not classic, it is composed of two elements (a main body and a flap).

To make them match as well as possible I modified the 2D polar (I shifted the stall point) and I wondered if this tweak could have an impact on unsteady aerodynamics results of the Beddoes-Leishman Model.

before :

and after :

Here is my OLAF configuration (default one proposed by OLAF guidelines)

```
5 IntMethod Integration method {5: Forward Euler 1st order, default: 5} (switch)
0.1 DTfvw Time interval for wake propagation. {default: dtaero} (s)
99999 FreeWakeStart Time when wake is free. (-) value = always free. {default: 0.0} (s)
0.0 FullCircStart Time at which full circulation is reached. {default: 0.0} (s)
--------------------------- CIRCULATION SPECIFICATIONS ----------------------------------------
1 CircSolvingMethod Circulation solving method {1: Cl-Based, 2: No-Flow Through, 3: Prescribed, default: 1 }(switch)
default CircSolvConvCrit Convergence criteria {default: 0.001} [only if CircSolvingMethod=1] (-)
default CircSolvRelaxation Relaxation factor {default: 0.1} [only if CircSolvingMethod=1] (-)
default CircSolvMaxIter Maximum number of iterations for circulation solving {default: 30} (-)
unused PrescribedCircFile File containing prescribed circulation [only if CircSolvingMethod=3] (quoted string)
===============================================================================================
--------------------------- WAKE OPTIONS ------------------------------------------------------
------------------- WAKE EXTENT AND DISCRETIZATION --------------------------------------------
420 nNWPanel Number of near-wake panels [integer] (-)
120 FarWakeLength Total wake distance [integer] (number of time steps)
60 FreeFarWakeLength Wake length that is free [integer] (number of time steps) {default: WakeLength}
False FWShedVorticity Include shed vorticity in the far wake {default: false}
------------------- WAKE REGULARIZATIONS AND DIFFUSION -----------------------------------------
0 DiffusionMethod Diffusion method to account for viscous effects {0: None, 1: Core Spreading, "default": 0}
3 RegDeterMethod Method to determine the regularization parameters {0: Manual, 1: Optimized, 2: Chord, 3: Span, default: 0 }
3 RegFunction Viscous diffusion function {0: None, 1: Rankine, 2: LambOseen, 3: Vatistas, 4: Denominator, "default": 3} (switch)
3 WakeRegMethod Wake regularization method {1: Constant, 2: Stretching, 3: Age, default: 1} (switch)
0.6 WakeRegFactor Wake regularization factor (m)
0.6 WingRegFactor Wing regularization factor (m)
1000 CoreSpreadEddyVisc Eddy viscosity in core spreading methods, typical values 1-1000
```

I tried to make some tweaks to the wake parameters but these seem to be the most stable.

I was wondering what you thought of my OLAF setup and my method of matching the 3D polar to the wind tunnel results.

Thank you very much,

Best regards,

Theo