Analysis Of Energy Fluxes Research Articles

Wave resource assessment and wave energy exploitation along the Indian coast

The present study investigates the feasibility of wave energy exploitation along the Indian coast using 19-year (2000–2018) hindcasted wave data generated by WAVEWATCH-III with a fine spatial resolution (0.1° × 0.1°) and temporal resolution (6 h). The wave model is validated against 12-month measured wave data collected at multiple buoy sites and compared with 19-year ERA5 data across the study area. The results show good agreement between model data and the other two datasets. The spatio-temporal variability analysis of wave energy flux reveals that southern coast of India has the mean wave energy flux ranging from 6 to 10 kW/m with a minimum monthly (<2.0), seasonal (<1.0) and annual (<0.2) variability which could be a promising area for future wave energy exploitation. A detailed analysis of wave power resource has been discussed for nine hotspot locations which were selected based on the optimum hotspot index, geographical restrictions on bathymetry and distance to the shore. Further, each hotspot has been analysed through combined scatter and energy diagrams. Finally, electrical power output is estimated at each hotspot using five wave energy converters and observed that the annual energy production at most of the locations is above 800 MWh with more than 70% availability.

Energy flux analysis in fruit agroecosystems

Energy flux analysis in fruit agroecosystems

The Climatological Horizontal Pattern of Energy Flux in the Tropical Atlantic as Identified by a Unified Diagnosis for Rossby and Kelvin Waves

AbstractThis study investigates the horizontal distribution of wave energy flux in the tropical Atlantic Ocean using shallow‐water model experiments for three gravest baroclinic modes forced by climatological winds. This is the first attempt to apply a unified diagnostic scheme to the analysis of energy fluxes associated with both Rossby waves (RWs) and Kelvin waves (KWs) in the tropical Atlantic Ocean. Those analyses were difficult in previous studies owing to the difference of equatorial and quasigeostrophic dynamics. The scheme yields the transfer route (i.e., trajectories by group velocity vector) of wave energy originating from both local wind forcing and boundary reflection. The meridional flux of wave energy crossing two zonal sections (at 3°N and at 2°S) is examined for understanding where the equatorial and off‐equatorial regions interconnect. Equatorward energy fluxes into the basin interior are found mainly on the zonal section in the Northern Hemisphere (at 3°N), indicating the radiation of RWs from the Guinea coast. At the equator, seasonal transition in May from eastward wind anomaly to westward anomaly yields a significant energy input at the central basin that radiates both RWs and KWs. The energy flux of these RWs arrives at the western boundary in September, followed by reflection of KWs to yield eastward transbasin energy fluxes in October‐December. The analysis also identifies an unexpected wind input in May at 4°S which induces both RWs and inertial gravity waves.

The Importance of Remote Forcing for Regional Modeling of Internal Waves

AbstractRegional ocean general circulation models are generally forced at the boundaries by mesoscale ocean dynamics and barotropic tides. In this work we provide evidence that remotely forced internal waves can be a significant source of energy for the dynamics. We compare global and regional model solutions within the California Current System. Both models have similar inputs, forcings, and identical grids and numerics. The global model has a steric height power spectrum consistent with mooring observations at superinertial frequencies, while the regional model spectrum is weaker. The regional model also has less sea surface height variance at high wavenumber than the global model. The vertical velocity variance is significantly larger in the global model, except in the sheltered Southern California Bight. While the regional model has roughly equal high‐pass baroclinic and barotropic kinetic energy levels, the global model high‐pass baroclinic kinetic energy is 28% (0.39 PJ) greater than the barotropic energy. An internal wave energy flux analysis reveals that the regional model domain boundaries act as a sink of 183 MW, while in the global model the analysis domain boundaries act as a source of 539 MW. This 722 MW difference can account for the relative increase of 0.39 PJ high‐pass baroclinic energy in the global model, assuming a baroclinic kinetic energy dissipation time in the domain of approximately 6.3 days. The results here imply that most regional ocean models will need to account for internal wave boundary fluxes in order to reproduce the observed internal wave continuum spectrum.

Multiscale control of active emulsion dynamics

We numerically study the energy transfer in a multi-component $2d$ film, made of an active polar gel and a passive isotropic fluid in presence of surfactant favoring emulsification. We show that by confining the active behavior into the localized component, the typical scale where chemical energy is transformed in mechanical energy can be substantially controlled. Quantitative analysis of kinetic energy spectra and fluxes shows the presence of a multi-scale dynamics due to the existence of a flux induced by the active stress only, without the presence of a turbulent cascade. An increase in the intensity of active doping induces drag reduction due to the competition of elastic and dissipative stresses against active forces. Furthermore we show that a non-homogeneous activity pattern induces localized response, including a modulation of the slip length, opening the way toward the control of active flows by external doping.

Assessing Changes in Airflow and Energy Loss in a Progressive Tracheal Compression Before and After Surgical Correction

The energy needed to drive airflow through the trachea normally constitutes a minor component of the work of breathing. However, with progressive tracheal compression, patient subjective symptoms can include severe breathing difficulties. Many patients suffer multiple respiratory co-morbidities and so it is important to assess compression effects when evaluating the need for surgery. This work describes the use of computational prediction to determine airflow resistance in compressed tracheal geometries reconstructed from a series of CT scans. Using energy flux analysis, the regions that contribute the most to airway resistance during inhalation are identified. The principal such region is where flow emerging from the zone of maximum constriction undergoes breakup and turbulent mixing. Secondary regions are also found below the tongue base and around the glottis, with overall airway resistance scaling nearly quadratically with flow rate. Since the anatomical extent of the imaged airway varied between scans—as commonly occurs with clinical data and when assessing reported differences between research studies—the effect of sub-glottic inflow truncation is considered. Analysis shows truncation alters the location of jet breakup and weakly influences the pattern of pressure recovery. Tests also show that placing a simple artificial glottis in the inflow to a truncated model can replicate patterns of energy loss in more extensive models, suggesting a means to assess sensitivity to domain truncation in tracheal airflow simulations.

Dynamic mechanism for the evolution and rapid intensification of Typhoon Hato (2017)

AbstractThis study investigated the evolution of Typhoon Hato (1713) and analyzed the inner dynamics of its rapid intensification. The moving path of Hato was controlled by the southwestern part of the western Pacific subtropical high which extended westward significantly. Due to a relatively steady leading steering flow, the trajectory of Hato showed a straight ESE to WNW direction, leading to disastrous rainfall in southern Guangdong Province on 23 August before and after the landfall of the typhoon. In addition, Typhoon Hato exhibited a rapid intensification period from 3 to 13 o'clock on 23 August, with central wind speeds increasing from 35 to 48 m/s. This study mainly examined the inner dynamics of the development of Hato, especially its rapid intensification period. The regression analysis results showed that Hato was generated and developed under a TD‐type‐like wave. The coupled convection and vortex provided a favorable environment for the development of Hato. The analysis of the barotropic eddy kinetic energy (EKE) and latent heat flux further demonstrated this scenario. The results showed that the regions with a positive EKE tendency and strong latent heat release were consistent with the reach of and shifted westward with Hato. The EKE conversion was enhanced significantly on 23 August, with a maximum intensity observed over the northern South China Sea and southern Guangdong Province. The mean kinetic energy was largely converted to EKE, which, together with the great latent heat release, led to the rapid intensification of Hato.

Effects of Northern Hemisphere Atmospheric Blocking on Arctic Sea Ice Decline in Winter at Weekly Time Scales

In this study, the effects of the Northern Hemisphere atmospheric blocking circulation on Arctic sea ice decline at weekly time scales are examined by defining four key regions based on observational data analysis. Given the regression analysis, the frequently occurring atmospheric patterns related to the sea ice decline in four key sea regions (Baffin Bay, Barents-Kara Seas, Okhotsk Sea and Bering Sea) are found to be Greenland blocking (GB), Ural blocking (UB), western Pacific blocking (PB-W) and eastern Pacific blocking (PB-E), respectively. The results show that the regional blocking frequency is higher (lower) in lower (higher) sea ice winters for each key region. Moreover, composite analysis indicates that blocking evolution is usually accompanied by significant sea ice decline at weekly time scales during the blocking life cycle for each key region. In addition, the intensified surface downward infrared radiation (IR) anomaly and the precipitable water for the entire atmosphere (PWA) in each key region are found to make significant contributions to the positive surface air temperature (SAT) anomaly, which is beneficial for the reduction in sea ice. The approximate quantitative analysis of different surface energy fluxes induced by blocking is also applied. Further analysis shows that the blocking event and the associated changes in SAT and radiation anomalies for each key region lead the sea ice decline by approximately 3~6 days. This result indicates that regional blocking can contribute to regional sea ice decline at weekly time scales through surface warming associated with enhanced water vapor and associated IR variations. Further quantitative estimates indicate that regional blocking can reduce regional sea ice cover (SIC) by 49.6%, 49.4%, 52.2% and 49.5% for Baffin Bay, Barents-Kara Seas, Okhotsk Sea and Bering Sea, respectively, during the blocking life cycle. Finally, a physical process diagrammatic sketch is given to illustrate how blocking affects SIC decline.

Higher order turbulent flow characteristics of oscillatory flow over a wall-mounted obstacle

The paper presents an experimental study in a laboratory flume to investigate the combined wave–current flow over a wall-mounted cubic obstacle. Detailed velocity data were collected using three-dimensional (3D) micro-acoustic Doppler velocimeter from upstream to downstream of the cube along the centerline of the flume. This study examines the spectra, co-spectra, and turbulence kinetic energy flux analysis under the influence of cube in the turbulent boundary layer. It is observed that stream-wise spectral and co-spectral energy distributions vary with the addition of surface wave. Particular attention is also given to understand the behavior of higher order moments to explicitly account for turbulent momentum transport characteristics over wall-mounted cube under wave–current interactions.

A methodological approach to the air-sea energy fluxes data collection and analysis at the tropical coastal ocean

The southern South China coastal oceans within the South East Asian region are much lacking in the perception of the surface energy budget and evaporation over the ocean waters in response to climatic changes. The eddy covariance method was used to measure the energy fluxes, microclimate variables, and surface water temperature from November 2015 to October 2017 at the Straits of Malacca, South China Sea; Pulau Pinang, Malaysia, situated at latitude 5°28'06?N, and longitude 100°12'01?E. This work focused on the methodological approach to the air-sea energy fluxes data collection and analysis. In this regard, the method applied for the direct measurements and analysis of energy fluxes and other meteorological parameters in the site is considered and reported.•The paper summarizes the analysis of energy fluxes, microclimate variables, and surface water temperature data in a tropical coastal ocean station using the eddy covariance method.•The methodological approach illustrates the method of analysis applied in this study which can be compared and used for similar studies in other places.•The reproducible data analysis technique matches similar comparative methods such as Matlab and Python.

MODEL OF A DIPOLE WITH ATOMIC STRUCTURE

In this paper, we propose a model of a dipole with an atomic structure instead of the standard dipole model with point unlike charges and the Hertzian dipole model, which have significant drawbacks. The equations of the Hertzian dipole and the standard model operate from a distance much larger than size of the dipole, and the quasistatic Coulomb and Biot-Savart fields are the essence of the reactive near field, its own fields with a phase shift ΔφE,H = π/2, which have no restrictions on the distances to a dipole, since they are directly related to charges and their motion – currents. In the framework of the proposed dipole model, we described the physical mechanisms for the formation of near and far fields of an oscillating dipole, which are based on the use of the Coulomb and Biot-Savart fields, the quasistatic lines of force of their electric charge fields Е, and the magnetic fields of the currents Н for the analysis of energy fluxes: reactive Sr at ΔφE,H = π/2 and active Sа at ΔφE,H = 0 alike.

Gravity Waves and Wind-Farm Efficiency in Neutral and Stable Conditions

We use large-eddy simulations (LES) to investigate the impact of stable stratification on gravity-wave excitation and energy extraction in a large wind farm. To this end, the development of an equilibrium conventionally neutral boundary layer into a stable boundary layer over a period of 8 h is considered, using two different cooling rates. We find that turbulence decay has considerable influence on the energy extraction at the beginning of the boundary-layer transition, but afterwards, energy extraction is dominated by geometrical and jet effects induced by an inertial oscillation. It is further shown that the inertial oscillation enhances gravity-wave excitation. By comparing LES results with a simple one-dimensional model, we show that this is related to an interplay between wind-farm drag, variations in the Froude number and the dispersive effects of vertically-propagating gravity waves. We further find that the pressure gradients induced by gravity waves lead to significant upstream flow deceleration, reducing the average turbine output compared to a turbine in isolated operation. This leads us to the definition of a non-local wind-farm efficiency, next to a more standard wind-farm wake efficiency, and we show that both can be of the same order of magnitude. Finally, an energy flux analysis is performed to further elucidate the effect of gravity waves on the flow in the wind farm.

Double-averaging analysis of turbulent kinetic energy fluxes and budget based on large-eddy simulation

The turbulent flow over a channel bed roughened by three layers of closely packed spheres with a Reynolds number of Re = 15000 is investigated using the large eddy simulation (LES) and the double-averaging (DA) method. The DA velocity is compared with the results of the corresponding laboratory experiments to validate the LES results. The existence of the types of vortex structures is demonstrated by the Q - criterion above the permeable bed. The turbulent kinetic energy (TKE) fluxes and budget are quantified and discussed. The results show that the TKE fluxes are directed downward and downstream near the virtual bed level. In the TKE budget, the form-induced diffusion rate is significant in the vicinity of the crest bed level, and the TKE production rate and the dissipation rate attain their peaks at the crest bed level and decrease sharply below it.

Mass, Energy, and Momentum Flux Analysis of a Bendway Weir

AbstractBendway weirs are hydraulic control structures found in watercourses that range in scale from small streams to large rivers. They are designed to be submerged, broad-crested weirs, typicall...

Experiments with a ‘psychrometric’ roof pond system for passive cooling in hot-arid regions

Roof pond systems for passive cooling of buildings are often limited in their efficiency because of solar heating loads or insufficient ventilation. Here we test the performance of a roof cooling configuration that resembles a naturally-ventilated psychrometer – designed to maintain a temperature close to that of the ambient wet-bulb by employing an elevated shading structure which allows for a free flow of air and maximizes evaporation. Comparing the performance of this ‘psychrometric’ roof pond (PRP) with a control roof under hot-dry conditions, it was found that the internal surface temperature of the PRP was up to 15°C lower and that cooling was equally effective whether the roof pond was fully or partially exposed to the night sky. Throughout the hours of a summer day, air temperature in the cell was maintained within accepted comfort limits while the reference cell was continuously overheated. An analysis of energy fluxes above the roof showed that both the modified radiation balance and the conversion of sensible to latent heat through evaporation were significant contributors to the dramatically reduced heat gain and cooling effectiveness. Due to its low water requirement and simplicity, the tested configuration could have a significant potential for resource-efficient cooling.

Six Years Observations and Analysis of Radiation Parameters and Surface Energy Fluxes on Ice Sheet near 'Maitri' Research Station, East Antarctica

In the present study, radiation parameters incoming shortwave radiation flux, reflected shortwave radiation flux, albedo have been observed on ice sheet near ‘Maitri’ research station, East Antarctica. Surface energy fluxes have been estimated using snow-meteorological parameters. Air temperature, surface temperature, relative humidity, wind speed, atmospheric pressure, incoming shortwave radiation flux, reflected shortwave radiation flux, albedo were recorded using automatic weather station installed on ice sheet about 1 km from ‘Maitri’ research station. Radiation parameters and energy fluxes were obtained for six years from March 2007 to January 2013. Mean incoming shortwave radiation flux, reflected shortwave radiation flux and albedo were observed to be 124 Wm–2, 80 Wm–2 and 0.64, respectively, during six years. Daily average air temperature at the observation site varies from 4.6°C to –28.6°C with six years mean of –10.2°C. High katabatic winds are observed at the site with six years mean wind speed of 8.4 ms–1. Net shortwave radiation flux and sensible heat flux were observed to be heat source for the ice sheet with mean values of 44 Wm–2 and 28 Wm–2, respectively, while net long wave radiation flux and latent heat flux were observed as heat sink with mean values of –49 Wm–2 and –62 Wm–2, respectively. Sublimation of the ice sheet at the rate of 0.017 cm/day has been observed. Results of the present study were also compared with other studies in Antarctica. It has been observed that present study site near ‘Maitri’ research station has comparatively warmer temperatures, low relative humidity, high wind speed and low albedo compared to other coastal stations in Antarctica. High sublimation rate of the ice sheet at the present study location may attribute to high katabatic winds and warmer temperatures.

Solvation Dynamics in Liquid Water. III. Energy Fluxes and Structural Changes.

In previous installments it has been shown how a detailed analysis of energy fluxes induced by electronic excitation of a solute can provide a quantitative understanding of the dominant molecular energy flow channels characterizing solvation-and in particular, hydration- relaxation dynamics. Here this work and power approach is complemented with a detailed characterization of the changes induced by such energy fluxes. We first examine the water solvent's spatial and orientational distributions and the assorted energy fluxes in the various hydration shells of the solute to provide a molecular picture of the relaxation. The latter analysis is also used to address the issue of a possible "inverse snowball" effect, an ansatz concerning the time scales of the different hydration shells to reach equilibrium. We then establish a link between the instantaneous torque, exerted on the water solvent neighbors' principal rotational axes immediately after excitation and the final energy transferred into those librational motions, which are the dominant short-time energy receptor.

Internal waves over the shelf in the western Bay of Bengal: a case study

Generation and propagation of internal waves (IWs) in the coastal waters of the extended shelf of the western Bay of Bengal are investigated for late winter by using the Massachusetts Institute of Technology General Circulation Model (MITgcm). The model is forced with astronomical tides and daily winds. Monthly climatological temperature and salinity fields are used as initial conditions. The simulations are compared with time series observations of temperature and currents from acoustic Doppler current profiler (ADCP) and conductivity-temperature-depth (CTD) moored at three locations south of Gopalpur: two at a local depth of 100 m and another at 400-m depth during 19–21 February 2012. The comparison of the spectral estimates for the time series of temperature from the model and observations are in reasonable agreement for the near-tidal frequency waves. The peak of temperature spectra is always found near the shelf break region which steadily lost its intensity over the continental shelf. The calculation of Richardson number reflected the presence of local mixing due to density overturning in the shelf region. To understand further the generation and propagation of internal tides in the region, energy flux and conversion of barotropic-to-baroclinic M2 tidal energy are examined. The model simulations suggest that the internal tide is generated all along the shelf slope. The energy flux analysis shows that the internal tides propagate to either side of the generation sites.

Spatio‐temporal variability of water and energy fluxes – a case study for a mesoscale catchment in pre‐alpine environment

AbstractWater and energy fluxes at and between the land surface, the subsurface and the atmosphere are inextricably linked over all spatio‐temporal scales. Our research focuses on the joint analysis of both water and energy fluxes in a pre‐alpine catchment (55 km2) in southern Germany, which is part of the Terrestrial Environmental Observatories (TERENO). We use a novel three‐dimensional, physically based and distributed modelling approach to reproduce both observed streamflow as an integral measure for water fluxes and heat flux and soil temperature measurements at an observation location over a period of 2 years. While heat fluxes are often used for comparison of the simulations of one‐dimensional land surface models, they are rarely used for additional validation of physically based and distributed hydrological modelling approaches. The spatio‐temporal variability of the water and energy balance components and their partitioning for dominant land use types of the study region are investigated. The model shows good performance for simulating daily streamflow (Nash–Sutcliffe efficiency &gt; 0.75). Albeit only streamflow measurements are used for calibration, the simulations of hourly heat fluxes and soil temperatures at the observation site also show a good performance, particularly during summer. A limitation of the model is the simulation of temperature‐driven heat fluxes during winter, when the soil is covered by snow. An analysis of the simulated spatial fields reveals heat flux patterns that reflect the distribution of the land use and soil types of the catchment. The water and energy partitioning is characterized by a strong seasonal cycle and shows clear differences between the selected land use types. Copyright © 2016 The Authors Hydrological Processes Published by John Wiley &amp; Sons Ltd.

Analysis of turbulent flow properties and energy fluxes in optimally controlled wind-farm boundary layers

In the present work our focus is to improve the performance of a wind farm by coordinated control of all turbines with the aim to increase the overall energy extraction by the farm. To this end, we couple flow simulations performed using Large Eddy Simulations (LES) with gradient based optimization to control individual turbines in a farm. The control parameters are the disk-based thrust coefficient of individual turbines as a function of time. They indirectly represent the effect of control actions that would correspond to blade-pitching of the turbines. We employ a receding-horizon predictive control setting and solve the optimization problem iteratively at each time horizon based on the gradient information obtained from the evolution of the flow field and the adjoint computation. We find that the extracted farm power increases by approximately 16% for a cost functional that is based on total energy extraction. However, this energy is gained from a slow deceleration of the boundary layer which is sustained for approximately 1 hour. We further analyze the turbulent stresses and compare to wind farms without optimal control.