# NREL 5MW Rotor in Atmospheric Boundary Layer With OpenFAST/BeamDyn Fluid Structure Interaction This benchmark contains a geometry and boundary-layer resolved model of the NREL 5MW reference turbine [1] in a developed near-neutral convective atmospheric boundary layer with a mean hub-height streamwise velocity of 11.4m/s. - Hub-height: 90m - Blade Radius: 63m - Rated Power: 5 MW - Type: Upwind 3 Blade - Simulation dt: 0.003443526170799 s - OpenFAST dt: 0.0008608815426997245 s *Note on run-time: Current results are for approximately 180s simulation time, but a minimum of 300s will be posted as results become available.* *Note on turbine controller: This case will be re-run in Q3 as a result of a small bug in the controller. If interested in running this benchmark, please contact the authors for up-to-date scheduling* ## Simulation Setup - ExaWind driver SHA: [cba5259fc43ddeca67329630d3c84faad90e91bb](https://github.com/Exawind/exawind-driver/commit/cba5259fc43ddeca67329630d3c84faad90e91bb) - Nalu-Wind SHA: [b9e4ae654b646ecd0501dd6391dc7537239c82db](https://github.com/Exawind/nalu-wind/commit/b9e4ae654b646ecd0501dd6391dc7537239c82db) - AMR-Wind SHA: [091b07fa3840af98925792290fb8788696290a5e](https://github.com/Exawind/amr-wind/commit/091b07fa3840af98925792290fb8788696290a5e) - OpenFAST 4.0.2 SHA: [fc1110183bcc87b16d93129edabdce6d30e3a497](https://github.com/OpenFAST/openfast/commit/fc1110183bcc87b16d93129edabdce6d30e3a497) ## Freestream Conditions A near-neutral convective boundary layer precursor was run to feed the domain for this case. Full details are posted here: [Convective ABL for NREL5MW](../../../amr-wind/atmospheric_boundary_layer/convective_abl_nrel5mw/README.md) 10 minute flow statistics: - Hub-height streamwise velocity: 11.4 m/s - Hub-height flow direction: ~240.0 degrees  ## CFD Mesh  **Total number of cells: 155,363,046** The near-body (Nalu-Wind) mesh was created using a proprietary surface mesher, pyHyp, and Pointwise. Three blades are split at the hub, and an unconnected tower is included. - Hexahedral cells - Cell count: 13,436,646 Off-body (AMR-Wind) mesh was generated using the built-in capability of AMR-Wind. Off-body mesh information is summarized below - Mesh topology: structured hex with nested refinements - Domain in x= 0 to 5000m, y=0m to 5000m, z=0m to 1000m - Initial grid size: 10m - Finest cell size: 0.625m with 4 AMR levels - Cell count: 141,926,400 ## Results ### Timeseries results from OpenFAST The plots below show timeseries of some key quantities as reported by OpenFAST (which in this simulation is acting as the structural and controller model).  ### Mean values over time period: 60s to 180s | variable | value | | -------- | ------- | |Generator Power|4165.49 kW| |Rotor Aero Torque|3509.12 kN-m| |Rotor Speed|12.0 rpm| |Rotor Thrust|643.58 kN| |B1 Root Flap Moment (x)|8.300869e+05 N-m| |B1 Root Edge Moment (y)|7.869930e+06 N-m| |B1 Tip Deflection x-direction|4.24 m| |B1 Pitch|2.07 degrees| ## Simulation Timings This benchmark was run at Sandia National Laboratories on a machine comprised of 112 Intel(R) Xeon(R) Platinum 8480+ CPU cores per node. ### Processor Decomposition: - Nalu-Wind: 672 ranks - AMR-Wind: 4928 ranks ### Timings: - Mean wall-clock time per timestep for entire simulation: 17.75s - Mean wall-clock time per timestep per cell 1.142e-07s ## Quick Exawind Simulation Guide ### Step 0: Run the ABL precursor in AMR-Wind This simulation is driven by an ABL precursor, run in AMR-Wind, with recorded boundary planes, initial conditions, and average temperature. (See case linked above) ### Step 1: Develop and decompose overset mesh It is necessary to develop a near-body mesh surrounding the blade surface in Nalu-Wind using external tools. This mesh should be in the Exodus II format and decomposed to approximately 20K cells per core available to Nalu-Wind. (Current mesh provided via dvc/github assets) ### Step 2: Run the OpenFAST precursor for 5760 OpenFAST timesteps (approximately 1 rotation) ``srun -n 1 openfastcpp inp.yaml`` ### Step 3: Run the full Exawind suite ``srun -N 50 -n 5600 exawind --nwind 672 --awind 4928 nrel5mw.yaml &> log`` ### Step 4: Setup and Run the full Exawind suite restart(s) ``srun -N 50 -n 5600 exawind --nwind 672 --awind 4928 nrel5mw_r1.yaml &> log_1`` ## References [1]: Jonkman, J. et al, "Definition of a 5-MW Reference Wind Turbine for Offshore System Development" NREL/TP-500-38060, 2009. https://www.nrel.gov/docs/fy09osti/38060.pdf