Direct aeroacoustic computer simulations investigating straight-bladed Darrieus vertical-axis wind turbines show that sound-related pressure radiation reaches its highest intensity during phases of rapid aerodynamic force changes rather than at moments of peak mechanical power. In a scientific preprint currently under review for the journal Wind Energy Science, mechanical engineering researchers Kazuya Kusano from Yokohama National University and Sota Nagatomi from Kyushu University analyzed how blade count influences both aerodynamic power generation and acoustic emissions. By resolving unsteady three-dimensional flow and acoustic fields, the authors demonstrated that the principal acoustic radiation peaks generated by the spinning blades correspond directly to rapid variations in the power coefficient driving the rotor, establishing an important phase-resolved connection between rotor loading dynamics and aerodynamic pressure radiation.
The research addresses an ongoing engineering challenge in renewable wind energy development: enabling wind turbines to generate electrical power efficiently without creating excessive acoustic disturbance for nearby residential communities. Blade number affects both the power performance and aerodynamic noise of vertical-axis wind turbines, but their phase relationships remain insufficiently understood. To explore these mechanisms systematically, the investigators compared one-bladed and two-bladed straight-bladed Darrieus rotor configurations operating at a tip-speed ratio of 4.5.
To resolve both fluid flow dynamics and acoustic wave propagation within a single computational framework, Kusano and Nagatomi employed three-dimensional direct aeroacoustic simulations using a hybrid lattice Boltzmann method equipped with body-fitted overset grids. A hybrid lattice Boltzmann method with body-fitted overset grids resolves flow, sound generation, and propagation.
The researchers assessed the performance of their computational methodology by comparing its aerodynamic wake predictions against physical measurements and conventional numerical approaches. When compared directly with standard lattice Boltzmann simulations, the hybrid lattice Boltzmann method with body-fitted overset grids predicted mean streamwise wake velocities that showed closer agreement with experimental measurement data downstream of the turbine rotor. However, the authors explicitly cautioned that this aerodynamic agreement in mean streamwise wake flow does not serve to validate the simulation’s acoustic predictions.
A key finding of the simulation study is that the principal pressure radiation peaks do not coincide with the rotor operating at its highest power coefficient. Instead, for both the single-bladed and two-bladed configurations, the primary peaks in acoustic radiation occur near the specific rotational phases where the power coefficient undergoes rapid temporal change. For the single-blade Darrieus rotor, the strongest radiation was observed during upstream blade passage. The authors noted that this pronounced radiation during the blade’s upstream sweep is consistent with the physical contribution of rapid aerodynamic load changes that occur when the airfoil moves at a high tip-speed ratio through the upstream sector of its circular path.
Evaluating the effect of blade number revealed that modifying the rotor layout leads to a substantial imbalance between acoustic radiation and energy capture. Adding a second, diametrically opposed blade increased the pressure-based radiation indicator substantially more than it increased the turbine’s mean power coefficient. The authors suggested that mutual reinforcement of acoustic waves emanating from the two opposed blades may contribute to this elevated radiation level. However, the simulation results could not distinguish the extent to which this increase stemmed from acoustic wave reinforcement as opposed to concurrent changes in the aerodynamic blade loading caused by the presence of the second blade.
The authors highlighted several critical scope limitations that temper the direct applicability of these computational findings to operational wind energy installations. The pressure-based radiation indicator utilized in the analysis inherently includes hydrodynamic pressure fluctuations alongside true propagating acoustic waves. Furthermore, the direct aeroacoustic model employed a spanwise-periodic rotor model, limiting generalization to turbine noise. In addition, the simulations were constrained by relatively short and unequal record lengths across the evaluated configurations. Consequently, while connecting blade-count effects on power performance with phase-dependent pressure radiation provides valuable conceptual guidance for quieter vertical-axis turbine designs, Kusano and Nagatomi concluded that further experimental and numerical testing remains necessary.
Subject of Research: Aeroacoustic radiation and aerodynamic power dynamics of vertical-axis wind turbines
Article Title: Aeroacoustic radiation from a vertical-axis wind turbine resolved by lattice Boltzmann simulations with body-fitted overset grids
Article References: Kusano, K., & Nagatomi, S. (2026). Aeroacoustic radiation from a vertical-axis wind turbine resolved by lattice Boltzmann simulations with body-fitted overset grids. https://doi.org/10.5194/wes-2026-207
Image Credits: AI Generated
DOI: 10.5194/wes-2026-207
Keywords: vertical-axis wind turbines, Darrieus rotors, aeroacoustics, lattice Boltzmann method, overset grids, aerodynamic noise, tip-speed ratio, power coefficient, blade loading, wake velocity, direct aeroacoustic simulation, blade count, hydrodynamic pressure fluctuations, acoustic radiation, spanwise-periodic rotor model, wind energy
News Source: Faith Mcneil. (November 12, 2026). Simulated Vertical-Axis Wind Turbine Pressure Radiation Peaks During Rapid Force Changes. Scienmag.
