Turbulence Parameter for a tidal turbine

Turbulence Parameters

Field Data

Novo P Kyozuka Y 2017   Field measurement and numerical study of tidal current turbulence intensity in the Kobe Strait of the Goto Islands, Nagasaki Prefecture

Turbulence Parameters   Turbulence_intensity

keywords: turbulence intensity, turbulence length scale, tidal turbine, flume

1 Turbulence Intensity:

• 1-3% ¹

1.75 % ²

• 10-20% (James Mcnaughton, 2013)

Field Data: 10%-25.5%³

2 Turbulent Length scale:

• 5% of tunnel diameter¹
• 1/3 channel depth ⁴
• 0.5m in water flume (turbine D=0.5m) ²

numerical DES modelling of the effect on turbulence length scale on wake recovery rate of a 1/20th scale model (0.5m) of HWTT ² comparing ℓ =0.5m and 1m, the results shows that

3 Turbulence Parameters for e387 turbine

U=0.6m/s, Turbulent length scale:

• based on BL thickness (user guide, fluent)
  • in a turbulent BL, ℓ is the order of δ₉₉, ℓ~δ₉₉

ℓ = 0.4 δ₉₉ =0.4 * 0.35mm=1.4e-4m where BL thickness is based on post -processing of RANS

• based on channel depth ⁴

ℓ= 1/3 channel depth = 1/3*1.6=0.53m

• Based on Turbulent viscosity ratio, (user guide, fluent)

for external flow, 1< μ_t/μ <10 if I=1%, and μ_t /μ =5, then ℓ = 1.25e-2m
ℓ= μ_t /(ρ C_μ^1/4 k^1/2)

4 Turbulence Parameter in Numerical Modelling

Footnotes:

¹

Luis Eca 2009 Report, Best Practice Guidelines for the application of Computational Fluid Dynamics in Marine Hydrodynamics

²

Ebdon, T., et al. "Modelling the Effect of Turbulence Length Scale on Tidal Turbine Wakes using Advanced Turbulence Models."

³

Novo P Kyozuka Y 2017 Field measurement and numerical study of tidal current turbulence intensity in the Kobe Strait of the Goto Islands, Nagasaki Prefecture

⁴

Blackmore, T., et al. "The sensitivity of actuator-disc rans simulations to turbulence length scale assumptions." (2011).

Created: 2018-07-22 Sun 21:11

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