arXiv subjects

Kirby S. Heck

Publications and source records attributed to Kirby S. Heck.

5 recordsLinked to original sources

arXiv2026

Influence of wind shear and veer on power, thrust, and induction of an actuator disk

Wind shear and wind veer (gradients of wind speed and direction, respectively) are ubiquitous in the atmospheric boundary layer (ABL), and wind turbines therefore routinely operate in sheared and veered conditions. Previous field campaigns have observed statistically significant variations in power production efficiency (quantified by a power coefficient) upwards of 15% due to shear and veer. However, it is not yet clear how non-uniform inflow conditions alter rotor aerodynamics and drive these efficiency variations. In this study, we perform concurrent-precursor large-eddy simulations (LES) of an actuator disk-modeled wind turbine across stratified ABL conditions to demonstrate that shear and veer can reduce wind power efficiency by more than 20%. To support these ABL simulations, we perform simplified inflow LES where shear and veer are controlled independently. Using these controlled simulations, we demonstrate that shear and veer effects can be decomposed into: (1) geometric effects, due to changes in rotor-equivalent wind speed, and (2) inductive effects, which change the rotor aerodynamics and induced velocities. Inductive effects of wind shear modulate the power coefficient through changes to the local induction, while inductive effects of wind veer reduce the power coefficient by generating an adverse pressure gradient at the rotor scale. The geometric and inductive effects of shear and veer approximately linearly superimpose, with increasing losses as shear and veer magnitudes increase. Inductive effects account for a significant fraction of the observed losses, and the induction of a turbine is affected by shear, veer, and wall proximity through processes that are neglected in existing engineering models. Revealing the mechanisms through which shear and veer affect rotor performance establishes a framework that can enable improved power prediction in realistic ABL conditions.

physics.flu-dyn↗

arXiv2025

Unraveling the effects of atmospheric dynamics on wakes with a controlled synthetic inflow methodology

Winds in the atmospheric boundary layer (ABL) display a wide range of velocity profiles and turbulence properties that affect wind turbine wake dynamics. However, standard concurrent-precursor large eddy simulations (LES) often neglect phenomena such as mesoscale patterns, limiting the range and controllability of inflow parameters that can be studied. Here, we propose a synthetic inflow LES method with high inflow controllability to allow parameters such as shear, turbulence, and Coriolis effects to be varied independently, facilitating the efficient exploration of wake dynamics across the full range of conditions observed in the field. The synthetic inflow method faithfully reconstructs wake dynamics when compared with standard concurrent-precursor LES. We then run a suite of over 600 LES cases to investigate the ABL processes that most affect wake dynamics. We find that wake recovery strongly depends on inflow wind veer, especially at low turbulence intensities, due to the elongation of the skewed wake. Furthermore, we identify a novel scaling relation that collapses wake deflections and dynamics onto the combination of shear and veer. The suite of LES cases elucidates ABL regimes and wake dynamics where current and future wind turbines may operate, building toward improved wake modeling for wind farm design and control.

physics.flu-dyn↗

arXiv2024

Coriolis effects on wind turbine wakes across atmospheric boundary layer regimes

Wind turbines operate in the atmospheric boundary layer (ABL), where Coriolis effects are present. As wind turbines with larger rotor diameters are deployed, the wake structures that they create in the ABL also increase in length. Contemporary utility-scale wind turbines operate at rotor diameter-based Rossby numbers, the nondimensional ratio between inertial and Coriolis forces, of O(100) where Coriolis effects become increasingly relevant. Coriolis forces provide a direct forcing on the wake, but also affect the ABL base flow, which indirectly influences wake evolution. These effects may constructively or destructively interfere because both the magnitude and sign of the direct and indirect Coriolis effects depend on the Rossby number, turbulence, and buoyancy effects in the ABL. Using large eddy simulations, we investigate wake evolution over a wide range of Rossby numbers relevant to offshore wind turbines. Through an analysis of the streamwise and lateral momentum budgets, we show that Coriolis effects have a small impact on the wake recovery rate, but Coriolis effects induce significant wake deflections which can be parsed into two regimes. For high Rossby numbers (weak Coriolis forcing), wakes deflect clockwise in the northern hemisphere. By contrast, for low Rossby numbers (strong Coriolis forcing), wakes deflect anti-clockwise. Decreasing the Rossby number results in increasingly anti-clockwise wake deflections. The transition point between clockwise and anti-clockwise deflection depends on the direct Coriolis forcing, pressure gradients, and turbulent fluxes in the wake. At a Rossby number of 125, Coriolis deflections are comparable to wake deflections induced by 17° of yaw-misalignment.

physics.flu-dyn↗

arXiv2024

Unified Momentum Model for Rotor Aerodynamics Across Operating Regimes

Despite substantial growth in wind energy technology in recent decades, aerodynamic modeling of wind turbines relies on momentum models derived in the late 19th and early 20th centuries, which are well-known to break down under flow regimes in which wind turbines often operate. This gap in theoretical modeling for rotors that are misaligned with the inflow and also for high-thrust rotors has resulted in the development of numerous empirical corrections which are widely applied in textbooks, research articles, and open-source and industry design codes. This work reports a unified momentum model to efficiently predict power production, thrust force, and wake dynamics of rotors under arbitrary inflow angles and thrust coefficients without empirical corrections. This unified momentum model can form a new basis for wind turbine modeling, design, and control tools from first-principles and may enable further development of innovations necessary for increased wind production and reliability to respond to 21st century climate change challenges.

physics.flu-dyn↗

arXiv2022

Modeling the induction, thrust, and power of a yaw misaligned actuator disk

Collective wind farm flow control, where wind turbines are operated in an individually suboptimal strategy to benefit the aggregate farm, has demonstrated potential to reduce wake interactions and increase farm energy production. However, existing wake models used for flow control often estimate the thrust and power of yaw misaligned turbines using simplified empirical expressions which require expensive calibration data and do not accurately extrapolate between turbine models. The thrust, wake velocity deficit, wake deflection, and power of a yawed wind turbine depend on its induced velocity. Here, we extend classical one-dimensional momentum theory to model the induction of a yaw misaligned actuator disk. Analytical expressions for the induction, thrust, initial wake velocities, and power are developed as a function of the yaw angle and thrust coefficient. The analytical model is validated against large eddy simulations of a yawed actuator disk. Because the induction depends on the yaw and thrust coefficient, the power generated by a yawed actuator disk will always be greater than a $\cos^3(γ)$ model suggests, where $γ$ is yaw. The power lost by yaw depends on the thrust coefficient. An analytical expression for the thrust coefficient that maximizes power, depending on the yaw, is developed and validated. Finally, using the developed induction model as an initial condition for a turbulent far-wake model, we demonstrate how combining wake steering and thrust (induction) control can increase array power, compared to either independent steering or induction control, due to the joint dependence of the induction on the thrust coefficient and yaw angle.

physics.flu-dyn↗