Mesoscale and macroscale kinetic energy fluxes from granular fabric evolution

2014 ◽  
Vol 89 (3) ◽  
Author(s):  
David M. Walker ◽  
Antoinette Tordesillas ◽  
Gary Froyland
Keyword(s):  
Kinetic Energy ◽  
Energy Fluxes ◽  
Fabric Evolution

scholarly journals Turbulence-driven thermal and kinetic energy fluxes in the atmospheres of hot Jupiters

2018 ◽  
Vol 481 (4) ◽  
pp. 5517-5531 ◽  
Author(s):  
Taeho Ryu ◽  
Michael Zingale ◽  
Rosalba Perna
Keyword(s):  
Kinetic Energy ◽  
Energy Fluxes ◽  
Hot Jupiters

scholarly journals One-year analysis of rain and rain erosivity in a tropical volcanic island from UHF wind profiler measurements

2013 ◽  
Vol 6 (2) ◽  
pp. 3249-3277 ◽  
Author(s):  
A. Réchou ◽  
M. Plu ◽  
B. Campistron ◽  
R. Decoupes
Keyword(s):  
Kinetic Energy ◽  
Rain Rate ◽  
Cold Front ◽  
Deep Convection ◽  
Trade Wind ◽  
Energy Fluxes ◽  
Trade Winds ◽  
Rainfall Events ◽  
The Mean ◽  
One Year

Abstract. La Réunion is a volcanic island in a tropical zone, which soil undergoes intense erosion. The possible contribution of rainfall to erosion is analyzed and quantified using one year of UHF radar profiler data located at sea level. Measurements of reflectivity, vertical and horizontal wind allow, with suitable assumptions, to determine raindrop vertical and horizontal energy fluxes, which are both essential parameters for erosion. After calibration of radar rain rates, one-year statistics between May 2009 to April 2010 allow to identify differences in rain vertical profiles depending on the season. During the cool dry season, the mean rain rate is less than 2.5 mm h−1 as high as 1.25 km and it decreases at higher altitudes due to the trade winds inversion. During the warm moist season, the mean rain rate is nearly uniform from ground up to 4 km, around 5 mm h−1. The dynamical and microphysical properties of rainfall events are investigated on three cases that are representative of meteorological events in La Réunion: summer deep convection, a cold front and a winter depression embedded in trade winds. For intense rainfall events, the rain rate deduced from the gamma function is in agreement with the rain rate deduced from the mere Marshall Palmer exponential relationship. For less intense events, the gamma function is necessary to represent rain distribution. The deep-convection event is associated to strong reflectivity reaching as high as 10 km, and strong negative vertical velocity. Wind shear is responsible for a deficiency of radar rain detection at the lower levels. During a cold front event, strong reflectivities reach the trade wind inversion (around 4 km high). The trade wind depression generates moderate rain only as high as 2 km. For all the altitudes, the horizontal kinetic energy fluxes are one order of magnitude stronger that than the vertical kinetic energy fluxes. A simple relationship between the reflectivity factor and vertical kinetic energy fluxes is found for each case study.

Spectral Energy Fluxes in Geostrophic Turbulence: Implications for Ocean Energetics

2007 ◽  
Vol 37 (3) ◽  
pp. 673-688 ◽  
Author(s):  
Robert B. Scott ◽  
Brian K. Arbic
Keyword(s):  
Kinetic Energy ◽  
Energy Cascade ◽  
Altimeter Data ◽  
Spectral Energy ◽  
Model Parameters ◽  
Baroclinic Mode ◽  
Mean Flow ◽  
Energy Fluxes ◽  
Inverse Cascade ◽  
Geostrophic Turbulence

Abstract The energy pathways in geostrophic turbulence are explored using a two-layer, flat-bottom, f-plane, quasigeostrophic model forced by an imposed, horizontally homogenous, baroclinically unstable mean flow and damped by bottom Ekman friction. A systematic presentation of the spectral energy fluxes, the mean flow forcing, and dissipation terms allows for a comprehensive understanding of the sources and sinks for baroclinic and barotropic energy as a function of length scale. The key new result is a robust inverse cascade of kinetic energy for both the baroclinic mode and the upper layer. This is consistent with recent observations of satellite altimeter data over the South Pacific Ocean. The well-known forward cascade of baroclinic potential and total energy was found to be very robust. Decomposing the spectral fluxes into contributions from different terms provided further insight. The inverse baroclinic kinetic energy cascade is driven mostly by an efficient interaction between the baroclinic velocity and the barotropic vorticity, the latter playing a crucial catalytic role. This cascade can be further enhanced by the baroclinic mode self-interaction, which is only present with nonuniform stratification (unequal layer depths). When model parameters are set such that modeled eddies compare favorably with observations, the inverse baroclinic kinetic energy cascade is actually much stronger than the well-known inverse cascade in the barotropic mode. The upper-layer kinetic energy cascade was found to dominate the lower-layer cascade over a wide range of parameters, suggesting that the surface cascade and time mean density stratification may be sufficient for estimating the depth-integrated cascade from ocean observations. This may find useful application in inferring the kinetic to gravitational potential energy conversion rate from satellite measurements.

scholarly journals Properties of rainfall in a tropical volcanic island deduced from UHF wind profiler measurements

2014 ◽  
Vol 7 (2) ◽  
pp. 409-418 ◽  
Author(s):  
A. Réchou ◽  
T. Narayana Rao ◽  
O. Bousquet ◽  
M. Plu ◽  
R. Decoupes
Keyword(s):  
Kinetic Energy ◽  
Case Studies ◽  
Rain Rate ◽  
Rain Gauge ◽  
Trade Wind ◽  
Wind Profiler ◽  
Simple Relationship ◽  
Energy Fluxes ◽  
Microphysical Properties ◽  
The Impact

Abstract. The microphysical properties of rainfall at the island of Réunion are analysed and quantified according to one year of wind profiler observations collected at Saint-Denis international airport. The statistical analysis clearly shows important differences in rain vertical profiles as a function of the seasons. During the dry season, the vertical structure of precipitation is driven by trade wind and boundary-layer inversions, both of which limit the vertical extension of the clouds. The rain rate is lower than 2.5 mm h−1 throughout the lower part of the troposphere (about 2 km) and decreases in the higher altitudes. During the moist season, the average rain rate is around 5 mm h−1 and nearly uniform from the ground up to 4 km. The dynamical and microphysical properties (including drop size distributions) of four distinct rainfall events are also investigated through the analysis of four case studies representative of the variety of rain events occurring on Réunion: summer deep convection, northerly-to-northeasterly flow atmospheric pattern, cold front and winter depression embedded in trade winds. Radar-derived rain parameters are in good agreement with those obtained from collocated rain gauge observations in all cases, which demonstrates that accurate qualitative and quantitative analysis can be inferred from wind profiler data. Fluxes of kinetic energy are also estimated from wind profiler observations in order to evaluate the impact of rainfall on soil erosion. Results show that horizontal kinetic energy fluxes are systematically one order of magnitude higher than vertical kinetic energy fluxes. A simple relationship between the reflectivity factor and vertical kinetic energy fluxes is proposed based on the results of the four case studies.

Mass momentum and kinetic energy fluxes of saltating particles

2020 ◽  
pp. 35-56
Author(s):  
A. Gillette Dale ◽  
H. Stockton Paul
Keyword(s):  
Kinetic Energy ◽  
Energy Fluxes

scholarly journals Effect of geometry and Reynolds number on the turbulent separated flow behind a bulge in a channel

2017 ◽  
Vol 823 ◽  
pp. 100-133 ◽  
Author(s):  
J.-P. Mollicone ◽  
F. Battista ◽  
P. Gualtieri ◽  
C. M. Casciola
Keyword(s):  
Reynolds Number ◽  
Kinetic Energy ◽  
Turbulent Flow ◽  
Shear Layer ◽  
Separation Bubble ◽  
Recirculation Region ◽  
Planar Channel ◽  
Energy Fluxes ◽  
Recirculation Bubble ◽  
Small Scales

Turbulent flow separation induced by a protuberance on one of the walls of an otherwise planar channel is investigated using direct numerical simulations. Different bulge geometries and Reynolds numbers – with the highest friction Reynolds number simulation reaching a peak of $Re_{\unicode[STIX]{x1D70F}}=900$ – are addressed to understand the effect of the wall curvature and of the Reynolds number on the dynamics of the recirculating bubble behind the bump. Global quantities reveal that most of the drag is due to the form contribution, whilst the friction contribution does not change appreciably with respect to an equivalent planar channel flow. The size and position of the separation bubble strongly depends on the bump shape and the Reynolds number. The most bluff geometry has a larger recirculation region, whilst the Reynolds number increase results in a smaller recirculation bubble and a shear layer more attached to the bump. The position of the reattachment point only depends on the Reynolds number, in agreement with experimental data available in the literature. Both the mean and the turbulent kinetic energy equations are addressed in such non-homogeneous conditions revealing a non-trivial behaviour of the energy fluxes. The energy introduced by the pressure drop follows two routes: part of it is transferred towards the walls to be dissipated and part feeds the turbulent production hence the velocity fluctuations in the separating shear layer. Spatial energy fluxes transfer the kinetic energy into the recirculation bubble and downstream near the wall where it is ultimately dissipated. Consistently, anisotropy concentrates at small scales near the walls irrespective of the value of the Reynolds number. In the bulk flow and in the recirculation bubble, isotropy is restored at small scales and the isotropy recovery rate is controlled by the Reynolds number. Anisotropy invariant maps are presented, showing the difficulty in developing suitable turbulence models to predict separated turbulent flow dynamics. Results shed light on the processes of production, transfer and dissipation of energy in this relatively complex turbulent flow where non-homogeneous effects overwhelm the classical picture of wall-bounded turbulent flows which typically exploits streamwise homogeneity.

scholarly journals Tidal and near-inertial internal waves over the Reykjanes Ridge

2020 ◽  
Author(s):  
Clément Vic ◽  
Bruno Ferron ◽  
Virginie Thierry ◽  
Herlé Mercier ◽  
Pascale Lherminier
Keyword(s):  
Energy Density ◽  
Kinetic Energy ◽  
Time Scales ◽  
Internal Waves ◽  
Phase Locking ◽  
Tidal Energy ◽  
Kinetic Energy Density ◽  
Energy Fluxes ◽  
Reykjanes Ridge ◽  
Inertial Energy

AbstractInternal waves in the semi-diurnal and near-inertial bands are investigated using an array of seven moorings located over the Reykjanes Ridge in a cross-ridge direction (57.6-59.1°N, 28.5-33.3°W). Continuous measurements of horizontal velocity and temperature for more than two years allow us to estimate the kinetic energy density and the energy fluxes of the waves. We found that there is a remarkable phase locking and linear relationship between the semi-diurnal energy density and the tidal energy conversion at the spring-neap cycle. The energy-to-conversion ratio gives replenishment time scales of 4-5 days on the ridge top vs 7-9 days on the flanks. Altogether, these results demonstrate that the bulk of the tidal energy on the ridge comes from near local sources, with a redistribution of energy from the top to the flanks, which is endorsed by the energy fluxes oriented in the cross-ridge direction. Implications for tidally-driven energy dissipation are discussed. The time-averaged near-inertial kinetic energy is smaller than the semi-diurnal kinetic energy by a factor 2-3, but is much more variable in time. It features a strong seasonal cycle with a winter intensification and sub-seasonal peaks associated with local wind bursts. The ratio of energy to wind work gives replenishment time scales of 13-15 days, which is consistent with the short time scales of observed variability of near-inertial energy. Finally, in the upper ocean (1 km), the highest levels of near-inertial energy are preferentially found in anticyclonic structures, with a twofold increase compared to cyclonic structures, illustrating the funneling effect of anticyclones.

scholarly journals Hortonian Overland Flow, Hillslope Morphology and Stream Power I: Spatial Energy Distributions and Steady-state Power Maxima

2021 ◽  
Author(s):  
Samuel Schroers ◽  
Olivier Eiff ◽  
Axel Kleidon ◽  
Jan Wienhöfer ◽  
Erwin Zehe
Keyword(s):  
Free Energy ◽  
Steady State ◽  
Energy Dissipation ◽  
Kinetic Energy ◽  
Potential Energy ◽  
Overland Flow ◽  
Slope Angle ◽  
Order Estimate ◽  
Energy Fluxes ◽  
Stream Power

Abstract. Recent developments in hydrology have led to a new perspective on runoff processes, extending beyond the classical mass dynamics of water in a catchment. For instance, stream flow has been analyzed in a thermodynamic framework, which allows the incorporation of two additional physical laws and enhances our understanding of catchments as open environmental systems. Related investigations suggested that energetic extremal principles might constrain hydrological processes, because the latter are associated with conversions and dissipation of free energy. Here we expand this thermodynamic perspective by exploring how macro and micro hillslope structures control the free energy balance of Hortonian overland flow. This may ultimately help understanding why these structures have evolved to their present shape. To this end, we develop a general theory of surface runoff and of the related conversion of geopotential energy gradients into other forms of energy, particularly kinetic energy as driver of erosion and sediment transport. We then use this framework to analyze how combinations of typical hillslopes profiles and width distributions control the spatial patterns of steady state stream power and energy dissipation along the flow path. Additionally, we provide a first order estimate whether and when rills reduce the overall energy dissipation compared to sheet flow. Finally, we relate accumulated stream power of linear hillslopes to slope angles, closing the loop to Horton's original formulation of erosion force. The analytical analysis of stream power reveals that the common formulation, a function of the depth-discharge product is a reduced version of the more general equations if we neglect changes in velocity and discharge in space. The full equations of stream power result in maximum energy fluxes in space for sinusoidal and exponential hillslope profiles, while linear and negative exponential forms unlimitedly increase these fluxes in the downstream direction. Depending on geometry, rill flow increases or decreases kinetic energy fluxes downslope, effectively counteracting or increasing the dissipation of potential energy. For accumulated power in space for steady state runoff, we find that on linear hillslopes a slope angle of 45° maximizes the conversion of potential energy into dissipation and an angle of 35° maximizes the conversion of potential energy into kinetic energy.

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