scholarly journals Properties of Hall-MHD Turbulence at Sub-Ion Scales: Spectral Transfer Analysis

Atmosphere ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1632
Author(s):  
Emanuele Papini ◽  
Petr Hellinger ◽  
Andrea Verdini ◽  
Simone Landi ◽  
Luca Franci ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Transfer Rate ◽  
Space Plasma ◽  
Theoretical Models ◽  
Magnetic Fluctuations ◽  
Energy Transfer Rate ◽  
Mhd Turbulence ◽  
Developed Turbulence ◽  
First Time ◽  
Hall Mhd

We present results of a multiscale study of Hall-magnetohydrodynamic (MHD) turbulence, carried out on a dataset of compressible nonlinear 2D Hall-MHD numerical simulations of decaying Alfvénic turbulence. For the first time, we identify two distinct regimes of fully developed turbulence. In the first one, the power spectrum of the turbulent magnetic fluctuations at sub-ion scales exhibits a power law with a slope of ∼−2.9, typically observed both in solar wind and in magnetosheath turbulence. The second regime, instead, shows a slope of −7/3, in agreement with classical theoretical models of Hall-MHD turbulence. A spectral-transfer analysis reveals that the latter regime occurs when the energy transfer rate at sub-ion scales is dominated by the Hall term, whereas in the former regime, the governing process is the dissipation (and the system exhibits large intermittency). Results of this work are relevant to the space plasma community, as they may potentially reconcile predictions from theoretical models with results from numerical simulations and spacecraft observations.

scholarly journals Impact of Switchbacks on Turbulent Cascade and Energy Transfer Rate in the Inner Heliosphere

2021 ◽  
Vol 922 (1) ◽  
pp. L11
Author(s):  
Carlos S. Hernández ◽  
Luca Sorriso-Valvo ◽  
Riddhi Bandyopadhyay ◽  
Alexandros Chasapis ◽  
Christian L. Vásconez ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Transfer Rate ◽  
Positive Energy ◽  
Magnetic Fluctuations ◽  
Energy Transfer Rate ◽  
Third Order ◽  
Additional Energy ◽  
The Magnetic Field ◽  
Turbulent Cascade ◽  
Inner Heliosphere

Abstract Recent Parker Solar Probe (PSP) observations of inner heliospheric plasma have shown an abundant presence of Alfvénic polarity reversal of the magnetic field, known as “switchbacks.” While their origin is still debated, their role in driving the solar wind turbulence has been suggested through analysis of the spectral properties of magnetic fluctuations. Here, we provide a complementary assessment of their role in the turbulent cascade. The validation of the third-order linear scaling of velocity and magnetic fluctuations in intervals characterized by a high occurrence of switchbacks suggests that, irrespective of their local or remote origin, these structures are actively embedded in the turbulent cascade, at least at the radial distances sampled by PSP during its first perihelion. The stronger positive energy transfer rate observed in periods with a predominance of switchbacks indicates that they act as a mechanism injecting additional energy in the turbulence cascade.

Turbulent cascade in the solar wind on ion scales

2020 ◽  
Author(s):  
Petr Hellinger ◽  
Andrea Verdini ◽  
Simone Landi ◽  
Luca Franci ◽  
Emanuele Papini ◽  
...  
Keyword(s):  
Solar Wind ◽  
Numerical Simulations ◽  
Hall Effect ◽  
Power Spectra ◽  
Two Dimensional ◽  
Mhd Turbulence ◽  
Ion Heating ◽  
Simulation Results ◽  
Hall Mhd ◽  
Turbulent Cascade

<p>Magnetic power spectra in the solar wind typically exhibit a transition, steepening, on characteristic ion scales. This transition is not yet fully understood. Two basic phenomena are usually suspected: Hall physics and dissipation. We investigate properties of this transition using numerical simulations.  We analyze results of two-dimensional hybrid simulations using a compressible version of von Kármán-Howarth equation for statistically homogeneous Hall MHD turbulence and compare these results to the predictions for the incompressible Hall MHD. The simulation results indicate that the transition between large, MHD and sub-ion scales is related to a combination of the Hall effect and ion heating/energization.</p>

Extraction of energy transfer rate constants from the pulsed laser generated thermal lens spectrometer signal

1982 ◽  
Vol 80 ◽  
pp. 433-436 ◽  
Author(s):  
R.T. Bailey ◽  
F.R. Cruickshank ◽  
R. Guthrie ◽  
D. Pugh ◽  
I.J.M. Weir
Keyword(s):  
Energy Transfer ◽  
Thermal Lens ◽  
Rate Constants ◽  
Transfer Rate ◽  
Pulsed Laser ◽  
Energy Transfer Rate

Flow Mixing Enhancement from Balloon Pulsations in an Intravenous Oxygenator

2004 ◽  
Vol 127 (3) ◽  
pp. 400-415 ◽  
Author(s):  
Amador M. Guzmán ◽  
Rodrigo A. Escobar ◽  
Cristina H. Amon
Keyword(s):  
Numerical Simulations ◽  
Oxygen Transfer ◽  
Fiber Bundle ◽  
Transfer Rate ◽  
Oxygen Transfer Rate ◽  
Three Dimensional ◽  
Time Dependent ◽  
Fiber Placement ◽  
Flow Mixing ◽  
Dependent Flow

Computational investigations of flow mixing and oxygen transfer characteristics in an intravenous membrane oxygenator (IMO) are performed by direct numerical simulations of the conservation of mass, momentum, and species equations. Three-dimensional computational models are developed to investigate flow-mixing and oxygen-transfer characteristics for stationary and pulsating balloons, using the spectral element method. For a stationary balloon, the effect of the fiber placement within the fiber bundle and the number of fiber rings is investigated. In a pulsating balloon, the flow mixing characteristics are determined and the oxygen transfer rate is evaluated. For a stationary balloon, numerical simulations show two well-defined flow patterns that depend on the region of the IMO device. Successive increases of the Reynolds number raise the longitudinal velocity without creating secondary flow. This characteristic is not affected by staggered or non-staggered fiber placement within the fiber bundle. For a pulsating balloon, the flow mixing is enhanced by generating a three-dimensional time-dependent flow characterized by oscillatory radial, pulsatile longitudinal, and both oscillatory and random tangential velocities. This three-dimensional flow increases the flow mixing due to an active time-dependent secondary flow, particularly around the fibers. Analytical models show the fiber bundle placement effect on the pressure gradient and flow pattern. The oxygen transport from the fiber surface to the mean flow is due to a dominant radial diffusion mechanism, for the stationary balloon. The oxygen transfer rate reaches an asymptotic behavior at relatively low Reynolds numbers. For a pulsating balloon, the time-dependent oxygen-concentration field resembles the oscillatory and wavy nature of the time-dependent flow. Sherwood number evaluations demonstrate that balloon pulsations enhance the oxygen transfer rate, even for smaller flow rates.

scholarly journals Research on the design and application of capillary heat exchangers for heat pumps in coastal areas

2021 ◽  
Vol 42 (3) ◽  
pp. 333-348
Author(s):  
Zhenpeng Bai ◽  
Yanfeng Li ◽  
Jin Zhang ◽  
Alan Fewkes ◽  
Hua Zhong
Keyword(s):  
Renewable Energy ◽  
Energy Transfer ◽  
Heat Exchanger ◽  
Heat Pump ◽  
Transfer Rate ◽  
Coastal Areas ◽  
Heat Energy ◽  
Low Carbon ◽  
Energy Transfer Rate ◽  
Pump System

This study investigated the optimal design of a capillary heat exchanger device for the heat pump system and its innovative engineering application in a building. The overall aim was to use a capillary heat exchanger to obtain energy in coastal areas for promoting renewable energy in low-carbon building design. Initially, the main factors affecting the efficiency of the capillary heat exchanger were identified, a mathematical model was then established to analyse the heat transfer process. The analysis showed the flow rate and the capillary length are the key factors affecting the efficiency of the capillary heat exchanger. Secondly, to optimize the structural design of the capillary heat exchanger, the heat energy transfer is calculated with different lengths of the capillary under various flow rates in summer and winter conditions, respectively. Thirdly, a typical building is selected to analyse the application of the capillary heat exchanger for extracting energy in the coastal area. The results show the performance of the selected capillary heat exchanger heat pump system, in winter, the heat energy transfer rate is 60 W/m2 when the seawater temperature is 3.7 °C; in summer, the heat energy transfer rate is 150 W/m2 when the seawater temperature is 24.6 °C. Finally, the above field test results were examined using a numerical simulation model, the test and simulation results agree with each other quite well. This paper is conducive in promoting the development of the capillary heat exchanger heat pump as an innovative sustainable technology for net-zero energy and low carbon buildings using renewable energy in coastal areas. Practical application: A recently proposed capillary heat exchanger is used as an energy extraction and utilisation device to obtain energy in coastal areas for promoting renewable energy in low-carbon building design. This paper explores the application of a capillary heat exchanger as both cold and heat sources for application in typical low-rise buildings. The analysis of the heat energy transfer rate of a typical low-rise building located in a coastal area in summer and winter provides guidance for the application of capillary heat exchangers.

Improvement of Er3+:4I11/2→Ce3+:2F5/2 energy transfer rate in Er3+/Ce3+ co-doped TeO2–ZnO–Na2O–Nb2O5 glasses

2009 ◽  
Vol 129 (1) ◽  
pp. 1-5 ◽  
Author(s):  
Yaxun Zhou ◽  
Jun Wang ◽  
Shixun Dai ◽  
Tiefeng Xu ◽  
Qiuhua Nie ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Transfer Rate ◽  
Energy Transfer Rate ◽  
Co Doped
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