Analysis of near-surface relative humidity in a wind turbine array boundary layer using an instrumented unmanned aerial system and large-eddy simulation

Wind Energy ◽  
2018 ◽  
Vol 21 (11) ◽  
pp. 1155-1168 ◽  
Author(s):  
Kevin A. Adkins ◽  
Adrian Sescu
Keyword(s):  
Boundary Layer ◽  
Relative Humidity ◽  
Large Eddy Simulation ◽  
Wind Turbine ◽  
Unmanned Aerial System ◽  
Near Surface ◽  
Eddy Simulation ◽  
Large Eddy

scholarly journals Hybrid RANS/LES Turbulence Model Applied to a Transitional Unsteady Boundary Layer on Wind Turbine Airfoil

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 128
Author(s):  
Di Zhang ◽  
Daniel R. Cadel ◽  
Eric G. Paterson ◽  
K. Todd Lowe
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Wind Turbine ◽  
Boundary Layers ◽  
Turbulence Model ◽  
Model Problem ◽  
Local Flow ◽  
Flow Angle ◽  
Eddy Simulation ◽  
Large Eddy

A hybrid Reynolds-averaged Navier Stokes/large-eddy simulation (RANS/LES) turbulence model integrated with a transition formulation is developed and tested on a surrogate model problem through a joint experimental and computational fluid dynamic approach. The model problem consists of a circular cylinder for generating coherent unsteadiness and a downstream airfoil in the cylinder wake. The cylinder flow is subcritical, with a Reynolds number of 64,000 based upon the cylinder diameter. The quantitative dynamics of vortex shedding and Reynolds stresses in the cylinder near wake are well captured, owing to the turbulence-resolving large eddy simulation mode that was activated in the wake. The hybrid model switched between RANS and LES modes outside the boundary layers, as expected. According to the experimental and simulation results, the airfoil encountered local flow angle variations up to ±50°. Further analysis through a phase-averaging technique found phase lags in the airfoil boundary layer along the chordwise locations, and both the phase-averaged and mean velocity profiles collapsed into the Law-of-the-wall in the range of 0 < y + < 50 . The features of high blade-loading fluctuations due to unsteadiness and transitional boundary layers are of interest in the aerodynamic studies of full-scale wind turbine blades, making the current model problem a comprehensive benchmark case for future model development and validation.

A scale-dependent dynamic model for large-eddy simulation: application to a neutral atmospheric boundary layer

2000 ◽  
Vol 415 ◽  
pp. 261-284 ◽  
Author(s):  
FERNANDO PORTÉ-AGEL ◽  
CHARLES MENEVEAU ◽  
MARC B. PARLANGE
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Atmospheric Boundary Layer ◽  
Dynamic Model ◽  
Scale Invariance ◽  
Scale Model ◽  
Near Surface ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Dependent Model

A scale-dependent dynamic subgrid-scale model for large-eddy simulation of turbulent flows is proposed. Unlike the traditional dynamic model, it does not rely on the assumption that the model coefficient is scale invariant. The model is based on a second test-filtering operation which allows us to determine from the simulation how the coefficient varies with scale. The scale-dependent model is tested in simulations of a neutral atmospheric boundary layer. In this application, near the ground the grid scale is by necessity comparable to the local integral scale (of the order of the distance to the wall). With the grid scale and/or the test-filter scale being outside the inertial range, scale invariance is broken. The results are compared with those from (a) the traditional Smagorinsky model that requires specification of the coefficient and of a wall damping function, and (b) the standard dynamic model that assumes scale invariance of the coefficient. In the near-surface region the traditional Smagorinsky and standard dynamic models are too dissipative and not dissipative enough, respectively. Simulations with the scale-dependent dynamic model yield the expected trends of the coefficient as a function of scale and give improved predictions of velocity spectra at different heights from the ground. Consistent with the improved dissipation characteristics, the scale-dependent model also yields improved mean velocity profiles.

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