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1. Large-eddy simulation of helical- and straight-bladed vertical-axis wind turbines in boundary layer turbulence

   https://doi.org/10.1063/5.0100169  

   Gharaati, Masoumeh ; Xiao, Shuolin ; Wei, Nathaniel J. ; Martínez-Tossas, Luis A. ; Dabiri, John O. ; Yang, Di ( September 2022 , Journal of Renewable and Sustainable Energy)

   Turbulent wake flows behind helical- and straight-bladed vertical axis wind turbines (VAWTs) in boundary layer turbulence are numerically studied using the large-eddy simulation (LES) method combined with the actuator line model. Based on the LES data, systematic statistical analyses are performed to explore the effects of blade geometry on the characteristics of the turbine wake. The time-averaged velocity fields show that the helical-bladed VAWT generates a mean vertical velocity along the center of the turbine wake, which causes a vertical inclination of the turbine wake and alters the vertical gradient of the mean streamwise velocity. Consequently, the intensities of the turbulent fluctuations and Reynolds shear stresses are also affected by the helical-shaped blades when compared with those in the straight-bladed VAWT case. The LES results also show that reversing the twist direction of the helical-bladed VAWT causes the spatial patterns of the turbulent wake flow statistics to be reversed in the vertical direction. Moreover, the mass and kinetic energy transports in the turbine wakes are directly visualized using the transport tube method, and the comparison between the helical- and straight-bladed VAWT cases show significant differences in the downstream evolution of the transport tubes. 

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2. A joint velocity-intermittency analysis reveals similarity in the vertical structure of atmospheric and hydrospheric canopy turbulence

   https://doi.org/10.1007/s10652-019-09694-w  

   Keylock, Christopher J. ; Ghisalberti, Marco ; Katul, Gabriel G. ; Nepf, Heidi M. ( February 2020 , Environmental Fluid Mechanics)
3. An evaluation of vertical mixing parameterization of ocean boundary layer turbulence for cohesive sediments

   https://doi.org/10.1016/j.dsr2.2022.105168  

   Liu, Jinliang ; Yuan, Jianguo ; Liang, Jun-Hong ( September 2022 , Deep Sea Research Part II: Topical Studies in Oceanography)
4. Isotropic turbulence apparatus with a large vertical extent

   https://doi.org/10.1007/s00348-021-03311-7  

   Hoffman, Davis W. ; Eaton, John K. ( October 2021 , Experiments in Fluids)

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5. Simulation and Scaling of the Turbulent Vertical Heat Transport and Deep-Cycle Turbulence across the Equatorial Pacific Cold Tongue

   https://doi.org/10.1175/JPO-D-21-0153.1  

   Whitt, D. B. ; Cherian, D. A. ; Holmes, R. M. ; Bachman, S. D. ; Lien, R.-C. ; Large, W. G. ; Moum, J. N. ( May 2022 , Journal of Physical Oceanography)

   Abstract Microstructure observations in the Pacific cold tongue reveal that turbulence often penetrates into the thermocline, producing hundreds of watts per square meter of downward heat transport during nighttime and early morning. However, virtually all observations of this deep-cycle turbulence (DCT) are from 0°, 140°W. Here, a hierarchy of ocean process simulations, including submesoscale-permitting regional models and turbulence-permitting large-eddy simulations (LES) embedded in a regional model, provide insight into mixing and DCT at and beyond 0°, 140°W. A regional hindcast quantifies the spatiotemporal variability of subsurface turbulent heat fluxes throughout the cold tongue from 1999 to 2016. Mean subsurface turbulent fluxes are strongest (∼100 W m −2 ) within 2° of the equator, slightly (∼10 W m −2 ) stronger in the northern than Southern Hemisphere throughout the cold tongue, and correlated with surface heat fluxes ( r 2 = 0.7). The seasonal cycle of the subsurface heat flux, which does not covary with the surface heat flux, ranges from 150 W m −2 near the equator to 30 and 10 W m −2 at 4°N and 4°S, respectively. Aseasonal variability of the subsurface heat flux is logarithmically distributed, covaries spatially with the time-mean flux, and is highlighted in 34-day LES of boreal autumn at 0° and 3°N, 140°W. Intense DCT occurs frequently above the undercurrent at 0° and intermittently at 3°N. Daily mean heat fluxes scale with the bulk vertical shear and the wind stress, which together explain ∼90% of the daily variance across both LES. Observational validation of the scaling at 0°, 140°W is encouraging, but observations beyond 0°, 140°W are needed to facilitate refinement of mixing parameterization in ocean models. Significance Statement This work is a fundamental contribution to a broad community effort to improve global long-range weather and climate forecast models used for seasonal to longer-term prediction. Much of the predictability on seasonal time scales is derived from the slow evolution of the upper eastern equatorial Pacific Ocean as it varies between El Niño and La Niña conditions. This study presents state-of-the-art high-resolution regional numerical simulations of ocean turbulence and mixing in the eastern equatorial Pacific. The results inform future planning for field work as well as future efforts to refine the representation of ocean mixing in global forecast models. 

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