scholarly journals The role of shallow convection in the momentum budget of the trades from large‐eddy‐simulation hindcasts

2021 ◽  
Author(s):  
K. C. Helfer ◽  
L. Nuijens ◽  
V.V. Dixit
Keyword(s):  
Large Eddy Simulation ◽  
Shallow Convection ◽  
Eddy Simulation ◽  
Momentum Budget ◽  
Large Eddy

Using field data–based large eddy simulation to understand role of atmospheric stability on energy production of wind turbines

2019 ◽  
Vol 43 (6) ◽  
pp. 625-638 ◽  
Author(s):  
Jordan Nielson ◽  
Kiran Bhaganagar
Keyword(s):  
Large Eddy Simulation ◽  
Wind Turbines ◽  
Surface Heat Flux ◽  
Energy Production ◽  
Surface Flux ◽  
Surface Heat ◽  
Net Energy ◽  
Eddy Simulation ◽  
Large Eddy

A novel and a robust high-fidelity numerical methodology has been developed to realistically estimate the net energy production of full-scale horizontal axis wind turbines in a convective atmospheric boundary layer, for both isolated and multiple wind turbine arrays by accounting for the wake effects between them. Large eddy simulation has been used to understand the role of atmospheric stability in net energy production (annual energy production) of full-scale horizontal axis wind turbines placed in the convective atmospheric boundary layer. The simulations are performed during the convective conditions corresponding to the National Renewable Energy Laboratory field campaign of July 2015. A mathematical framework was developed to incorporate the field-based measurements as boundary conditions for the large eddy simulation by averaging the surface flux over multiple diurnal cycles. The objective of the study is to quantify the role of surface flux in the calculation of energy production for an isolated, two and three wind turbine configuration. The study compares the mean value, +1 standard deviation, and −1 standard deviation from the measured surface flux to demonstrate the role of surface heat flux. The uniqueness of the study is that power deficits from large eddy simulation were used to determine wake losses and obtain a net energy production that accounts for the wake losses. The frequency of stability events, from field measurements, is input into the calculation of an ensemble energy production prediction with wake losses for different wind turbine arrays. The increased surface heat flux increases the atmospheric turbulence into the wind turbines. Higher turbulence results in faster wake recovery by a factor of two. The faster wake recovery rates result in lowering the power deficits from 46% to 28% for the two-turbine array. The difference in net energy production between the +1 and −1 standard deviation (with respect to surface heat flux) simulations was 10% for the two-turbine array and 8% for the three-turbine array. An ensemble net energy production by accounting for the wake losses indicated the overestimation of annual energy production from current practices could be corrected by accounting for variation of surface flux from the mean value.

scholarly journals Large-eddy simulation of organized precipitating trade wind cumulus clouds

2013 ◽  
Vol 13 (1) ◽  
pp. 1855-1889 ◽  
Author(s):  
A. Seifert ◽  
T. Heus
Keyword(s):  
Large Eddy Simulation ◽  
Trade Wind ◽  
Shallow Convection ◽  
Cumulus Clouds ◽  
Eddy Simulation ◽  
Cold Pools ◽  
Cloud Clusters ◽  
Large Eddy ◽  
Sensitivity Studies ◽  
The Individual

Abstract. Trade wind cumulus clouds often organize in along-wind cloud streets and across-wind mesoscale arcs. We present a benchmark large-eddy simulation which resolves the individual clouds as well as the mesoscale organization on scales of O(10 km). Different methods to quantify organization of cloud fields are applied and discussed. Using perturbed physics large-eddy simulations experiments the processes leading to the formation of cloud clusters and the mesoscale arcs are revealed. We find that both cold pools as well as the sub-cloud layer moisture field are crucial to understand the organization of precipitating shallow convection. Further sensitivity studies show that microphysical assumptions can have a pronounced impact on the onset of cloud organization.

A large eddy simulation study of the inshore nutrient uplift process: The role of topography

2020 ◽  
Author(s):  
Zheye Wang ◽  
Shuang Li
Keyword(s):  
Large Eddy Simulation ◽  
Vertical Plane ◽  
Nutrient Distribution ◽  
Fish Yield ◽  
Near Surface ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Near Shore ◽  
Natural Reefs

<p>Artificial fish reefs are the underwater structures placed on the ocean floor to simulate some characteristics of natural reefs. The onshore current can be transformed into upwelling under the influence of artificial fish reefs, thus the nutrient at the bottom of the near shore can be raised, which increases the prey of plankton and fish yield. In order to investigate this phenomenon, a 3D large eddy simulation (LES) of the ocean boundary layer was combined with four different types of artificial fish reef terrains (square, convex-fan, isosceles right triangle, concave-fan). In the near surface, almost only the square terrain can uplift the nutrient, which brings about the most uniform nutrient distribution. Based on the size of integral values of nutrient concentration in the upper part of the four reefs, they are listed as follows: square terrain, convex-fan terrain, isosceles right triangle terrain, concave-fan terrain decreases (from largest to smallest). What is more, the integral values of the four terrains reduce exponentially. Because the nutrient flow encounters the square terrain’s vertical plane, it has a larger vertical velocity. Nevertheless, for convex-fan terrain and isosceles right triangle terrain, their slopes are smoothly, resulting in poor lifting effect. Meanwhile, compared with the other three types of terrains, the concave-fan terrain can prevent the overflow of nutrients better. Among those four reefs, it can be found the square-shaped artificial fish reef is the best one for uplifting the nutrient.</p>

Homogeneity of the Subgrid-Scale Turbulent Mixing in Large-Eddy Simulation of Shallow Convection

2013 ◽  
Vol 70 (9) ◽  
pp. 2751-2767 ◽  
Author(s):  
Dorota Jarecka ◽  
Wojciech W. Grabowski ◽  
Hugh Morrison ◽  
Hanna Pawlowska
Keyword(s):  
Large Eddy Simulation ◽  
Turbulent Mixing ◽  
Droplet Radius ◽  
Subgrid Scale ◽  
Shallow Convection ◽  
Eddy Simulation ◽  
Droplet Concentration ◽  
Large Eddy ◽  
Double Moment ◽  
The Mean

Abstract This paper presents an approach to locally predict homogeneity of the subgrid-scale turbulent mixing in large-eddy simulation of shallow clouds applying double-moment warm-rain microphysics. The homogeneity of subgrid-scale mixing refers to the partitioning of the cloud water evaporation due to parameterized entrainment between changes of the mean droplet radius and changes of the mean droplet concentration. Homogeneous and extremely inhomogeneous mixing represent two limits of possible scenarios, where the droplet concentration and the mean droplet radius remains unchanged during the microphysical adjustment, respectively. To predict the subgrid-scale mixing scenario, the double-moment microphysics scheme is merged with the approach to delay droplet evaporation resulting from entrainment. Details of the new scheme and its application in the Barbados Oceanographic and Meteorological Experiment (BOMEX) shallow convection case are discussed. The simulated homogeneity of mixing varies significantly inside small convective clouds, from close to homogeneous to close to extremely inhomogeneous. The mean mixing characteristics become more homogeneous with height, reflecting increases of the mean droplet size and the mean turbulence intensity, both favoring homogeneous mixing. Model results are consistent with microphysical effects of entrainment and mixing deduced from field observations. Mixing close to homogeneous is predicted in volumes with the highest liquid water content (LWC) and strongest updraft at a given height, whereas mixing in strongly diluted volumes is typically close to extremely inhomogeneous. The simulated homogeneity of mixing has a small impact on mean microphysical characteristics. This result agrees with the previous study applying prescribed mixing scenarios and can be explained by the high humidity of the clear air involved in the subgrid-scale mixing.

scholarly journals The Large-Eddy Simulation (LES) Atmospheric Radiation Measurement (ARM) Symbiotic Simulation and Observation (LASSO) Activity for Continental Shallow Convection

2020 ◽  
Vol 101 (4) ◽  
pp. E462-E479 ◽  
Author(s):  
William I. Gustafson ◽  
Andrew M. Vogelmann ◽  
Zhijin Li ◽  
Xiaoping Cheng ◽  
Kyle K. Dumas ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Large Scale ◽  
Spatial Scales ◽  
Atmospheric Radiation ◽  
Radiation Measurement ◽  
Shallow Convection ◽  
Eddy Simulation ◽  
Skill Scores ◽  
Large Eddy ◽  
Atmospheric Radiation Measurement

Abstract The U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) user facility recently initiated the Large-Eddy Simulation (LES) ARM Symbiotic Simulation and Observation (LASSO) activity focused on shallow convection at ARM’s Southern Great Plains (SGP) atmospheric observatory in Oklahoma. LASSO is designed to overcome an oft-shared difficulty of bridging the gap from point-based measurements to scales relevant for model parameterization development, and it provides an approach to add value to observations through modeling. LASSO is envisioned to be useful to modelers, theoreticians, and observationalists needing information relevant to cloud processes. LASSO does so by combining a suite of observations, LES inputs and outputs, diagnostics, and skill scores into data bundles that are freely available, and by simplifying user access to the data to speed scientific inquiry. The combination of relevant observations with observationally constrained LES output provides detail that gives context to the observations by showing physically consistent connections between processes based on the simulated state. A unique approach for LASSO is the generation of a library of cases for days with shallow convection combined with an ensemble of LES for each case. The library enables researchers to move beyond the single-case-study approach typical of LES research. The ensemble members are produced using a selection of different large-scale forcing sources and spatial scales. Since large-scale forcing is one of the most uncertain aspects of generating the LES, the ensemble informs users about potential uncertainty for each date and increases the probability of having an accurate forcing for each case.

Sign in / Sign up

Export Citation Format

Share Document