Actuator Line Wind Turbine Simulations in Atmospheric Turbulent Flows using Spectral Element Method

2018

Wind Energy

Self Cite

Wind farms are known to modulate large scale structures in and around the wake regions of the turbines. The potential benefits of placing small hub height, small rotor turbines in between the large turbines in a wind farm to take advantage of such modulated large‐scale eddies are explored using large eddy simulation (LES). The study has been carried out in an infinite wind farm framework invoking an asymptotic limit, and the wind turbines are modeled using an actuator line model. The vertically staggered wind turbine arrangements that are studied in the present work consist of rows of large wind turbines, with rows of smaller wind turbines (ie, smaller rotor size and shorter hub height) placed in between the rows of large turbines. The influence of the hub height of the small turbines, in particular, how it affects the interactions between the large and small turbines and consequently their power, along with the multiscale dynamics involved, has been assessed in the current study. It was found that, in the multiscale layouts, the small turbines at lower hub heights operate more efficiently than their homogeneous single‐scale counterparts. In contrast, the small turbines with higher hub heights incur a loss of power compared with the corresponding single‐scale arrangements.

Section: Computational Setupmentioning

confidence: 99%

Section: Computational Setupmentioning

confidence: 99%

Exploring the benefits of vertically staggered wind farms: Understanding the power generation mechanisms of turbines operating at different scales

2018

Wind Energy

Self Cite

“…For best results in our SEM model (see [14] for details), the adhoc blending function parameters C 0 = 0.19, n = 0.5 are used.…”

Section: Governing Equations and Large Eddy Simula-tionmentioning

confidence: 99%

“…are unit vectors in the x, y direction). The "hat" represents additional explicit filtering carried out in the modal space by attenuating k c = 4, highest Legendre polynomial modes of the spectral element model [14]. For collocated spectral element methods u ∆z…”

Section: Model Assumptions: Boundary Conditions and Near Wall Modellingmentioning

confidence: 99%

“…The summation in the forces is over all N blade elements, and ε = 2 w d is used in the current study for optimum results. The AL model is more advanced than the actuator-disc model [2] commonly used in numerical computations of WTABL, in its capability to capture the tip-vortices being shed in the near-wake quite accurately [14,16].…”

Section: Actuator Line Modelmentioning

confidence: 99%

See 1 more Smart Citation

Spectra and Large Eddy Structures in the Double Log-Layer of a High Re Wind Turbine Array Boundary Layer

Volume 9: Oil and Gas Applications; Supercritical CO2 Power Cycles; Wind Energy

2016

Self Cite

Wind Turbine Array Boundary Layer (WTABL) is a relatively simple, yet useful theoretical conceptualization to study very large wind farms in atmospheric boundary layer (ABL). In the current paper, we perform a high-fidelity LES investigation of a 3 × 3 wind turbine array in a WTABL framework, with a main focus on extending the work beyond the simple analytical model and providing a rigorous fundamental understanding of the dynamic behaviour of length scales, their scaling laws and the anisotropic structure of the energy containing eddies responsible for power generation from the wind turbines. This is accomplished by studying the components of energy and shear-stress spectra in the flow. This knowledge can potentially provide an efficient way to control the wind farm power output as well as serve as a stepping stone to design efficient low order numerical models for predicting farm power and dynamics at reduced computational expense.

Effect of artificial length scales in large eddy simulation of a neutral atmospheric boundary layer flow: A simple solution to log-layer mismatch

2017

Physics of Fluids

A large eddy simulation (LES) methodology coupled with near-wall modeling has been implemented in the current study for high Re neutral atmospheric boundary layer flows using an exponentially accurate spectral element method in an open-source research code Nek5000. The effect of artificial length scales due to subgrid scale (SGS) and near wall modeling (NWM) on the scaling laws and structure of the inner and outer layer eddies is studied using varying SGS and NWM parameters in the spectral element framework. The study provides an understanding of the various length scales and dynamics of the eddies affected by the LES model and also the fundamental physics behind the inner and outer layer eddies which are responsible for the correct behavior of the mean statistics in accordance with the definition of equilibrium layers by Townsend. An economical and accurate LES model based on capturing the near wall coherent eddies has been designed, which is successful in eliminating the artificial length scale effects like the log-layer mismatch or the secondary peak generation in the streamwise variance.