The Influence of Turbulence Model on Wake Structure of TSTs when
used with a Coupled BEM-CFD Model
Ian Masters, R. Malki, Alison Williams & Nick Croft
Marine Energy Research GroupSwansea University
Modelling Approach
Source: A. Mason-Jones , PhD thesis Cardiff University (2010)
Moving Mesh Approach Time-averaged Approach
Array Modelling
Time-Averaged Influence of Blades
Discretisation of Turbine Blades
Discretisation of Turbine Blades (2)
Impact of Blades on the Flow
Impact of Blades on the Flow (2)
Calculating Resultant Forces
Resolving Forces
Calculating Source Terms (BEMT)
Substituting Source Terms (BEM-CFD)
Substituting Source Terms (BEM-CFD)
Model Domain
0.5m
0.25m
1.4m
0.5m
1.54m
0.84m
0.17m
0.84m
0.17m
Rotor Modelling
Wake Edge Parameters
Wake Edge Characterisation
95% Wake Edges
P∞
PWAKE
P95%
P∞
k-epsilon• Eddy viscosity from single length scale• Turbulent diffusion occurs only at specified scaleRNG k-epsilon• Account for different scales of motionk-omega• Viscous sub-layer flows• Adverse pressure gradients and separating flows
Turbulence Models
Shear Stress Transport (SST)• k-ω near boundary• k-ε in free-stream• Adverse pressure gradients & separating flowsReynolds Stress Model (RSM)• Reynolds Stresses directly computed• Directional effects of Reynolds stress fields• More suitable for anisotropic turbulence
Turbulence Models
Velocity
Velocity
Velocity
Turbulence Intensity
Turbulence Intensity
Turbulence Intensity
Turbulent Viscosity
Lateral Shear
Velocity ProfilesTSR = 4.0
Velocity ProfilesTSR = 4.0 & 6.0
TI ProfilesTSR = 4.0
TI ProfilesTSR = 4.0 & 6.0
Wake Diameter 95% Velocity
TSR = 4.0
Wake Diameter 95% Velocity
TSR = 4.0 & 6.0
Wake Diameter 95% TI
TSR = 4.0
Wake Diameter 95% TI
TSR = 4.0 & 6.0
Wake Diameter 95% dUdz TSR = 4.0
Wake Diameter 95% dUdz
TSR = 4.0 & 6.0
• Turbulence Models affect Hydrodynamics• Lack of Measured Data for Validation• Possibly better represent turbulence
Conclusions
Rotor Source Terms