Dear all,

I’m studying WISDEM/WEIS code for optimizing the platform cost of a FOWT. For my case study, I’m using the example RAFT_studies with only slight modifications (changing only the number of design variables).

The analysis options are the following:

general:

folder_output: outputs/15_RAFT_Rect

fname_output: refturb_outputdesign_variables:

## tower:

## outer_diameter:

## flag: False

## lower_bound: 4.0

## upper_bound: 10.0

## layer_thickness:

## flag: False

## lower_bound: 4.e-3

## upper_bound: 2.e-1

floating:

joints:

flag: True

z_coordinate:

- names: [main_keel, col1_keel, col2_keel, col3_keel]

lower_bound: -40.0

upper_bound: -15.0

r_coordinate:

- names: [col1_keel, col1_freeboard, col2_keel, col2_freeboard, col3_keel, col3_freeboard]

lower_bound: 38.8125

upper_bound: 64.6875

# members:

# flag: True

# groups:

# - names: [column1,column2,column3]

# diameter:

# lower_bound: 9.375

# upper_bound: 15.625

# constant: True

# thickness:

# lower_bound: 0.05

# upper_bound: 0.25

# constant: True

# - names: [Y_pontoon_lower1, Y_pontoon_lower2, Y_pontoon_lower3]

# diameter:

# lower_bound: 7.5

# upper_bound: 12.5constraints:

control:

rotor_overspeed:

flag: False

min: 0.0

max: 0.25

Max_PtfmPitch:

flag: True

max: 5.5

Std_PtfmPitch:

flag: True

max: 2.

Max_Offset:

flag: True

max: 30.

floating:

stress:

flag: True

global_buckling:

flag: True

shell_buckling:

flag: True## merit_figure: LCOE # Merit figure of the optimization problem. The options are ‘AEP’ - ‘LCOE’ - ‘Cp’ - ‘blade_mass’ - ‘blade_tip_deflection’

merit_figure_user:

name: floatingse.platform_costdriver:

optimization:

flag: True # Flag to enable optimization

solver: COBYLA # Optimization solver. Other options are ‘SLSQP’ - ‘CONMIN’

tol: 1.e-2 # Optimality tolerance

max_iter: 100 # Maximum number of iterations (SLSQP)## design_of_experiments:

## flag: True # Flag to enable design of experiments

## run_parallel: False # Flag to run using parallel processing

## generator: LatinHypercube # Type of input generator. (Uniform)

## num_samples: 12 # number of samples for (Uniform only)

recorder:

flag: True # Flag to activate OpenMDAO recorder

file_name: log_opt.sql # Name of OpenMDAO recorder

includes: [‘raft’,‘floating’,‘platform’]

The modeling options are the following:

General:

verbosity: False # When set to True, the code prints to screen many infos

openfast_configuration:

use_exe: True

allow_fails: True

fail_value: 9999WISDEM:

RotorSE:

flag: True

spar_cap_ss: Spar_Cap_SS

spar_cap_ps: Spar_Cap_PS

te_ss: TE_reinforcement_SS

te_ps: TE_reinforcement_PS

TowerSE:

flag: True

DriveSE:

flag: True

FloatingSE:

flag: True

# gamma_f: 1.35 # Safety factor for fatigue loads

# gamma_m: 1.3 # Safety factor for material properties

# gamma_n: 1.0 # Safety factor for …

# gamma_b: 1.1 # Safety factor for …

# gamma_fatigue: 1.755 # Safety factor for fatigue loads

# buckling_length: 30 # Buckling parameter

# soil_springs: True

# gravity_foundation: False

# frame3dd:

# shear: True

# geom: True

# tol: 1e-9

BOS:

flag: TrueLevel3: # Options for WEIS fidelity level 3 = nonlinear time domain

flag: False

simulation:

DT: 0.01

CompElast: 1

CompInflow: 1

CompAero: 2

CompServo: 1

CompHydro: 1

CompSub: 0

CompMooring: 3

CompIce: 0

OutFileFmt: 3

linearization:

Linearize: False

ElastoDyn:

FlapDOF1: True

FlapDOF2: True

EdgeDOF: True

TeetDOF: False

DrTrDOF: False

GenDOF: True

YawDOF: False

TwFADOF1 : True

TwFADOF2 : True

TwSSDOF1 : True

TwSSDOF2 : True

PtfmSgDOF: True

PtfmSwDOF: True

PtfmHvDOF: True

PtfmRDOF : True

PtfmPDOF : True

PtfmYDOF : True

HydroDyn:

WvLowCOff: 0.15708

WvHiCOff: 3.2

WaveSeed1: 123456789

AddBQuad1: [9.23e5, 0.0, 0.0, 0.0, -8.92e6, 0.0]

AddBQuad2: [0.0, 9.23e5, 0.0, 8.92e6, 0.0, 0.0]

AddBQuad3: [0.0, 0.0, 2.3e6, 0.0, 0.0, 0.0]

AddBQuad4: [0.0, 8.92e6, 0.0, 1.68e10, 0.0, 0.0]

AddBQuad5: [-8.92e6, 0.0, 0.0, 0.0, 1.68e10, 0.0]

AddBQuad6: [0.0, 0.0, 0.0, 0.0, 0.0, 4.8e10]

PotMod: 1

# WaveMod: 0Level1:

flag: True

potential_model_override: 0

trim_ballast: 0

heave_tol: 1

save_designs: TrueROSCO:

flag: True

SD_Mode: 0

PS_Mode: 1

ps_percent: 0.85

F_LPFType: 2

F_NotchType: 2

Fl_Mode: 2

tuning_yaml: …/…/examples/01_aeroelasticse/OpenFAST_models/IEA-15-240-RWT/IEA-15-240-RWT-UMaineSemi/IEA15MW-UMaineSemi.yaml

zeta_pc: [1]

omega_pc: [0.2]

U_pc: [12]

zeta_vs: 0.85 # Torque controller desired damping ratio [-]

omega_vs: 0.12

twr_freq: 3.2

ptfm_freq: 0.2

Kp_float: -10DLC_driver:

metocean_conditions:

wind_speed: [4., 6., 8., 10., 12., 14., 16., 18., 20., 22., 24.]

wave_height_NSS: [0.83, 0.88, 0.94, 1.03, 1.16, 1.34, 1.57, 1.86, 2.22, 2.62, 3.07]

wave_period_NSS: [6.9, 6.96, 7.02, 7.12, 7.25, 7.43, 7.66, 7.94, 8.27, 8.63, 9.01]

wave_height_SSS: [6.3, 8, 8, 8.1, 8.5, 8.5, 9.8, 9.8, 9.8, 9.8, 9.9]

wave_period_SSS: [11.5, 12.7, 12.7, 12.8, 13.1, 13.1, 14.1, 14.1, 14.1, 14.1, 14.1]

wave_height1: 6.98

wave_period1: 11.7

wave_height50: 10.68

wave_period50: 14.2

DLCs:

- DLC: “1.1”

n_seeds: 1

- DLC: “1.3”

n_seeds: 6

# - DLC: “1.4”

# - DLC: “1.5”

# - DLC: “1.6”

# n_seeds: 1

- DLC: “6.1”

n_seeds: 1

# - DLC: “6.3”

# n_seeds: 6

Trim_ballast is set to 0, leaving ballast density unchanged.

I notice that there are two different sets of substructure mass:

1)the first set is related to floatingse module output

```
2)the second one is related to raft outputs
```

I was wondering why there is a difference between them. Could you give me any advises to interpret the results?

Moreover, I would like to ask how substructure mass is related to the cost reported in the variable “*floatingse.platform_cost*”.

Thanks in advance for your support.

Best regards,