Forward Energy Research Articles

STRUCTURE STATISTICS OF SCALE TO SCALE ENERGY TRANSFER OF WALL TURBULENCE BASED ON LBM

For the reason that the scale-to-scale energy transfer characteristics of wall bounded turbulence exhibit strong anisotropy in three dimensional physical space, understanding the spatial distribution of energy scale-to-scale transfer is of great importance for the further construction of high-fidelity anisotropic large eddy simulation models. Direct numerical simulation were performed at Reynolds number $Re_{\tau } =180$ by using lattice Boltzmann method (LBM). In comparison with the open source channel flow turbulence database, both the mean velocity and turbulent variables, such as Reynolds stress and velocity fluctuations, agree well with the results of Kim et al. (1987) and Moser et al. (2015). The ability and validity of LBM on simulating turbulent channel flow were verified. The filter-space technique is used to obtain the scale-to-scale transport of kinetic energy, and the statistical results show that the backward scatter and forward scatter contributions to the SGS dissipation were comparable. Combined with the novel structure identification method, the distribution and geometry properties of the energy flux structure is quantitatively investigated by the clustering methodology. The results show that small scale structures account for the majority in number, and the volume probability density distribution presents a -4/5 power law. The structures can further be divided into wall attached structures and wall detached structures according to their minimal distance to the wall. In spite of the relatively small number fraction, the attached structure accounts for most of volume fraction, which shows that most of the attached structures are large scale structures. Further statistics of the attached structures exhibit that the size of the structure has a certain power law relationship, indicating that the scale-to-scale energy transport structure also has the self similarity of the attached eddy hypothesis which proposed by Townsend. The forward and backward energy flux structure pairs tend to be arranged side by side along the span direction.

Renewable energy consumption policy in Turkey: An energy extended input-output analysis

The energy sector with 70% public budget influence in Turkey is unsurprisingly one of the sectors over which most policies have been developed. Although Turkey is rich in terms of renewable energy sources such as solar, water, wind, geothermal; as the speed of the consumption of the energy generated through these resources is higher than the production, the use of other non-renewable energy sources is at stake, and increases the emission amount released into the environment depending on this type of energy used. In this study, Energy Extended Input-Output Analysis has been conducted using the data of emission occurred depending on energy use within the framework of energy economy as an interdisciplinary field of study. And research has been carried out on the mutual interdependency between energy and economy. This paper employs an analysis recently published as an input-output table of the year 2014 of Turkey and energy use emission data of the same year in the World Input-Output Database. The emission occurred as a result of one single unit of energy use in the sector of electricity, gas, steam, and air conditioning supply, which are one of the two sectors including the whole components of the energy sector in Turkey, comes first with 51.4327 TJ/million-dollar coefficient, manufacture of coke and refined petroleum products, which is the other sector, ranks at the ninth row with the coefficient of 4.4556 TJ/million-dollar. As a result of the conducted analysis, while normalized total backward energy use emission linkages coefficients (BLj) equal 10.1074 TJ for Electricity, gas, steam, and air conditioning supply sector, they are 1.1676 TJ for the manufacture of coke and refined petroleum products. Normalized total forward energy use emission linkages coefficients (FLi) are 21.448 TJ for electricity, gas, steam and air conditioning supply, yet they are 1.3941 TJ for manufacture of coke and refined petroleum products. Policies on the sustainable use of energy in Turkey have been developed through the achieved results in the content of the study. Policies by focusing on the economy and prioritizing the role of energy in providing sustainable development, preferring environmentally friendly renewable energy sources, and encouraging less production of emission, have especially been mentioned.

Over 30 000 h Device Lifetime in Deep Blue Organic Light‐Emitting Diodes with y Color Coordinate of 0.086 and Current Efficiency of 37.0 cd A−1

AbstractThe development of highly efficient and long‐life deep blue devices has been an ongoing challenge in the field of organic light‐emitting diodes (OLEDs) because of the short lifetime inherent to highly efficient blue devices. The efficiency and lifetime issues of the deep blue OLEDs are resolved in this work by engineering the device architecture by managing the triplet excitons of the phosphorescence and thermally activated delayed fluorescence (TADF) emitters. The CN‐modified imidazole type Ir emitter and boron‐based TADF emitter with similar emission energy are combined to develop an energy exchanging phosphorescence and TADF (EPHTADF) device. An emission mechanism inducing both forward and backward energy transfer concurrently between the Ir phosphor and TADF emitter shortens the triplet exciton lifetime of the two emitters, which dramatically enhances the device lifetime of the blue devices. Deep blue OLEDs triggering EPHTADF emission ultimately yields device performances including high current efficiency (CE) of 37.0 cd A−1, color‐coordinate corrected CE of 430.9 cd A−1, extrapolated device lifetime of more than 30 000 h, and deep blue color coordinates of (0.122, 0.086). This work demonstrates the potential of EPHTADF devices to serve as the solution to the problematic issues of the blue OLEDs.

2.0 μm Ultra Broadband Emission from Tm3+/Ho3+ Co-Doped Gallium Tellurite Glasses for Broadband Light Sources and Tunable Fiber Lasers

A flat 2.0 μm ultra broadband emission with a full width at half maximum (FWHM) of 329 nm is achieved in 1 mol.% Tm2O3 and 0.05 mol.% Ho2O3 co-doped gallium tellurite glasses upon the excitation of an 808 nm laser diode. The influence of Tm3+ and Ho3+ contents on 2.0 μm spectroscopic properties of gallium tellurite glasses is minutely investigated by absorption spectra, emission spectra, and lifetime measurement. In addition, emission cross section and gain coefficient of Ho3+ ions at 2.0 μm are calculated, and the maximum values reach 8.2 × 10−21 cm2 and 1.54 cm−1, respectively. Moreover, forward and backward energy transfer probability between Tm3+ and Ho3+ ions are qualitatively evaluated by the extended spectral overlap method. Large ratio of the forward energy transfer from Tm3+ to Ho3+ to the backward one (19.7) and high forward energy transfer coefficient (6.22 × 1039 cm6/s) are responsible for effective 2.0 μm emission from Ho3+ ions. These results manifest that Tm3+/Ho3+ co-doped gallium tellurite glass is suitable for potential applications of broadband light sources and tunable fiber lasers operating in eye-safe 2.0 µm spectral region.

Effect of spatial dimension on a model of fluid turbulence

A numerical study of the $d$ -dimensional eddy damped quasi-normal Markovian equations is performed to investigate the dependence on spatial dimension of homogeneous isotropic fluid turbulence. Relationships between structure functions and energy and transfer spectra are derived for the $d$ -dimensional case. Additionally, an equation for the $d$ -dimensional enstrophy analogue is derived and related to the velocity derivative skewness. Comparisons are made to recent four-dimensional direct numerical simulation results. Measured energy spectra show a magnified bottleneck effect which grows with dimension whilst transfer spectra show a varying peak in the nonlinear energy transfer as the dimension is increased. These results are consistent with an increased forward energy transfer at higher dimensions, further evidenced by measurements of a larger asymptotic dissipation rate with growing dimension. The enstrophy production term, related to the velocity derivative skewness, is seen to reach a maximum at around five dimensions and may reach zero in the limit of infinite dimensions, raising interesting questions about the nature of turbulence in this limit.

The very forward CASTOR calorimeter of the CMS experiment

The physics motivation, detector design, triggers, calibration, alignment, simulation, and overall performance of the very forward CASTOR calorimeter of the CMS experiment are reviewed. The CASTOR Cherenkov sampling calorimeter is located very close to the LHC beam line, at a radial distance of about 1cm from the beam pipe, and at 14.4m from the CMS interaction point, covering the pseudorapidity range of −6.6 < η < −5.2. It was designed to withstand high ambient radiation and strong magnetic fields. The performance of the detector in measurements of forward energy density, jets, and processes characterized by rapidity gaps, is reviewed using data collected in proton and nuclear collisions at the LHC.

Production and migration of turbulent kinetic energy in bluff body shear layers

An experimental campaign on a bluff body of rectangular cross section, having a side-length ratio of 5:1 was carried out using both particle image velocimetry and hot wire anemometry at a Reynolds number of 3.04×104. Results show that under a slight angle of attack, the development of unsteadiness in the form of turbulent kinetic energy is significantly amplified on the pressure side of the body. A series of linear corrections fail to fully collapse the behavior of the curved shear onto the growth rates of the canonical planar mixing layer solution as expected. In pursuit of providing a physical mechanism to a non-linear contribution to shear layer transition, inspection of relevant components of the Kármán-Howarth-Monin-Hill equation suggest a re-orientation of energy in scale-space, resulting in a combined forward and reverse energy transfer. It is shown that this reorganization process and energy transfer depend on the orientation of energetic structures within the shear layer.

On the Generalization of the Response Matrix Spectral Nodal Method for Neutral Particle SN Source–Detector Problems in Slab Geometry

A generalization of the Response Matrix spectral nodal method is applied to fixed–source discrete ordinates (SN ) radiative transfer and neutron transport problems in slab geometry. This method is extended to forward and adjoint energy multigroup problems with anisotropic scattering including the upscattering events. We present the numerical methodology which generates SN solutions absolutely free from spatial truncation errors. To discuss the efficiency of the method, we offer a number of numerical results for two typical test problems.

Scale-by-scale kinetic energy budget near the turbulent/nonturbulent interface

A scale-by-scale energy budget is investigated near the turbulent--nonturbulent interfacial layer with direct numerical simulations of a local turbulent front evolving without mean shear. The forward interscale energy transfer is caused by the velocity gradient in the interface normal direction. The pressure diffusion removes the energy at small scales within the interfacial layer.

CO2 capture performance and mechanism of blended amine solvents regulated by N-methylcyclohexyamine

Blended amine solvents are considered potential alternatives to monoethanolamine for CO2 capture, for the fast absorption kinetics of primary/secondary amine and low regeneration penalty of tertiary amine. In this research, blended amine solvents comprising N,N-dimethylcyclohexylamine (DMCA) and N-methylcyclohexyamine (MCA) were proposed. CO2 absorption increased the polarity of the products and ensured the absorbent remained homogenous throughout the absorption/desorption cycles. Through quantum chemical calculation, the low stability of MCA-carbamate was confirmed by a ΔΔG3 value of −6.41 kcal/mol, and a possible reaction route from carbamate to bicarbonate was revealed. Thus, the CO2 capacity of DMCA-MCA reached 0.875–0.985 mol CO2/mol amine. Moreover, MCA exhibited considerably low forward energy barrier for zwitterion formation (2.7 kcal/mol), and the CO2 absorption of DMCA could be accelerated through the proton transfer reaction with the MCA-zwitterion. Accordingly, the total mass transfer coefficient of CO2 in DMCA-MCA approached 2.02 × 10−10 mol/cm2 s Pa, which was 1.2-fold higher than that of 5 M MEA. The total regeneration energy of DMCA-MCA blend was estimated at 2.20 GJ/t CO2, which was 44.9% lower than 5 M MEA. This study developed a novel DMCA-MCA blended solvent with rapid absorption rate, huge CO2 capacity and efficient regeneration for CO2 capture.

Fluctuation theorem and extended thermodynamics of turbulence.

Turbulent flows are out-of-equilibrium because the energy supply at large scales and its dissipation by viscosity at small scales create a net transfer of energy among all scales. This energy cascade is modelled by approximating the spectral energy balance with a nonlinear Fokker-Planck equation consistent with accepted phenomenological theories of turbulence. The steady-state contributions of the drift and diffusion in the corresponding Langevin equation, combined with the killing term associated with the dissipation, induce a stochastic energy transfer across wavenumbers. The fluctuation theorem is shown to describe the scale-wise statistics of forward and backward energy transfer and their connection to irreversibility and entropy production. The ensuing turbulence entropy is used to formulate an extended turbulence thermodynamics.

Double-cone ignition scheme for inertial confinement fusion.

While major progress has been made in the research of inertial confinement fusion, significant challenges remain in the pursuit of ignition. To tackle the challenges, we propose a double-cone ignition (DCI) scheme, in which two head-on gold cones are used to confine deuterium–tritium (DT) shells imploded by high-power laser pulses. The scheme is composed of four progressive controllable processes: quasi-isentropic compression, acceleration, head-on collision and fast heating of the compressed fuel. The quasi-isentropic compression is performed inside two head-on cones. At the later stage of the compression, the DT shells in the cones are accelerated to forward velocities of hundreds of km s–1. The head-on collision of the compressed and accelerated fuels from the cone tips transfer the forward kinetic energy to the thermal energy of the colliding fuel with an increased density. The preheated high-density fuel can keep its status for a period of approximately 200 ps. Within this period, MeV electrons generated by ps heating laser pulses, guided by a ns laser-produced strong magnetic field further heat the fuel efficiently. Our simulations show that the implosion inside the head-on cones can greatly mitigate the energy requirement for compression; the collision can preheat the compressed fuel of approximately 300 g cm−3 to a temperature above keV. The fuel can then reach an ignition temperature of greater than 5 keV with magnetically assisted heating of MeV electrons generated by the heating laser pulses. Experimental campaigns to demonstrate the scheme have already begun.This article is part of a discussion meeting issue ‘Prospects for high gain inertial fusion energy (part 1)’.

Scale-by-scale energy transfer in a dual-plane jet flow

We numerically investigate the scale-by-scale energy transfer along all three directions (i.e., streamwise, vertical, and spanwise directions) at three specifically selected centerline locations (i.e., X/L0 = 7, 12, and 20) in a dual-plane jet flow by using the Karman–Howarth–Monin–Hill (KHMH) equation, where X and L0 are the streamwise distance from the inlet and the initial jet width, respectively. Unlike the well-known Karman–Howarth equation, the fully generalized KHMH equation allows us to study the scale-by-scale energy balance without any assumptions (i.e., homogeneity and isotropy). We calculate each term in the KHMH equation by using the data from a direct numerical simulation [Zhou et al., “Dual-plane turbulent jets and their non-Gaussian velocity fluctuations,” Phys. Rev. Fluids 3, 124604 (2018)]. At X/L0 = 7, where the flow is inhomogeneous and anisotropic, the scale-by-scale energy transfer is quite different in the streamwise, vertical, and spanwise directions. One interesting finding is that a negative production term in the vertical direction can be found in the reversal flow region. Unlike most flows previously investigated, the linear energy cascade plays an important role in the energy cascade. The linear energy transfer is heavily dependent on the direction: in the streamwise direction, it is forward (from the large scale to the small scale), but in the vertical direction, it is backward (from the small scale to the large scale). A physical model is proposed and also verified, which suggests that the forward linear energy cascade corresponds to fluid compression, and the backward linear energy cascade corresponds to the fluid stretching. At X/L0 = 12, where the energy spectrum exhibits a well-defined −5/3 scaling, there is no equilibrium energy cascade. The linear energy cascade is still dominant and shows a backward cascade in the streamwise direction and a forward cascade in the vertical direction, while the non-linear energy cascade remains forward. At X/L0 = 20, where the flow becomes much more homogeneous and isotropic, within a short scale-range around the Taylor microscale, the dissipation term can be balanced by the combination of the non-linear energy transfer term and advection term. This observation to some extent echoes Kolmogorov’s hypothesis, but limited only to length scales around the Taylor microscale, and the persistence of the advection term can find its root in the low local Reynolds number at that length scale.

Age, sex, and the vascular contributors to cerebral pulsatility and pulsatile damping.

Cerebral pulsatility reflects a balance between the transmission and damping of pulsatility in the cerebrovasculature. Females experience greater cerebral pulsatility with aging, which may have implications for sex differences in stroke risk and cognitive decline. This study sought to explore vascular contributors to cerebral pulsatility and pulsatile damping in men and women. Adults (n = 282, 53% female) underwent measurements of cerebral (middle cerebral artery) pulsatility, pulsatile damping (ratio of cerebral to carotid pulsatility), large artery stiffening (ratio of aortic to carotid pulse wave velocity), and carotid wave transmission/reflection dynamics using wave intensity analysis. Multiple regression revealed that older age, female sex, greater large artery stiffening, higher carotid pulse pressure, and greater forward wave energy was associated with increased cerebral pulsatility (adjusted R2 = 0.44, P < 0.05). Contributors to decreased cerebral pulsatile damping included older age, female sex, and lower wave reflection index (adjusted R2 = 0.51, P < 0.05). Our data link greater large artery stiffening, carotid pulse pressure, and forward wave energy to greater cerebral pulsatility, while greater carotid wave reflection may enhance cerebral pulsatile damping. Lower cerebral pulsatile damping among females may contribute to greater age-associated cerebral pulsatile burden compared with males.NEW & NOTEWORTHY Cerebral pulsatility contributes to brain health and depends on a balance between transmission and damping of pulsatile hemodynamics into the cerebrovasculature. Our data indicate that cerebral pulsatility increases with age, female sex, extracranial artery stiffening, forward wave energy, and pulse pressure, whereas pulsatile damping decreases with age and female sex and increases with greater carotid wave reflections. These novel data identify pulsatile damping as a potential contributor to sex differences in cerebral pulsatile burden.

Energy and congestion aware routing based on hybrid gradient fields for wireless sensor networks

The principles of physics and system sciences are increasingly used in the field of network engineering to design network protocols. This work proposes an energy and congestion aware routing (ECAR) algorithm inheriting the concepts of the potential field. It uses depth and time-variant network parameters to forward the data packets through low congestion and an energy-balanced path. We define a novel forward aware energy density as a decision metric along with residual energy and queue-length for forwarding data packets. It results in network-wide balanced residual energy and enhanced network lifetime. The proposed ECAR algorithm is evaluated for the transmission rounds before the first dead node (FDN) is detected. It is found that in typical traffic conditions, there was an average increment of 45% transmission rounds till the FDN appeared. Moreover, the simulated and theoretical findings are compared using statistical measures that justify its energy and congestion awareness.

Homogeneous isotropic turbulence in four spatial dimensions

Direct numerical simulation is performed for the forced Navier–Stokes equation in four spatial dimensions. Well equilibrated, long time runs at sufficient resolution were obtained to reliably measure spectral quantities, the velocity derivative skewness, and the dimensionless dissipation rate. Comparisons to corresponding two- and three-dimensional results are made. Energy fluctuations are measured, and the results show a clear reduction moving from three to four dimensions. The dynamics show simplifications in four dimensions with a picture of increased forward energy transfer resulting in an extended inertial range with a smaller Kolmogorov scale. This enhanced forward transfer is linked to our finding of increased dissipative anomaly and velocity derivative skewness.

Transition from Geostrophic Flows to Inertia–Gravity Waves in the Spectrum of a Differentially Heated Rotating Annulus Experiment

Abstract Inertia–gravity waves (IGWs) play an essential role in the terrestrial atmospheric dynamics as they can lead to energy and momentum flux when propagating upward. An open question is to what extent IGWs contribute to the total energy and to the flattening of the energy spectrum observed at the mesoscale. In this work, we present an experimental investigation of the energy distribution between the large-scale balanced flow and the small-scale imbalanced flow. Weakly nonlinear IGWs emitted from baroclinic jets are observed in the differentially heated rotating annulus experiment. Similar to the atmospheric spectra, the experimental kinetic energy spectra reveal the typical subdivision into two distinct regimes with slopes k−3 for the large scales and k−5/3 for the small scales. By separating the spectra into the vortex and wave components, it emerges that at the large-scale end of the mesoscale the gravity waves observed in the experiment cause a flattening of the spectra and provide most of the energy. At smaller scales, our data analysis suggests a transition toward a turbulent regime with a forward energy cascade up to where dissipation by diffusive processes occurs.

Secrecy Performance Analysis of UAV Assisted Relay Transmission for Cognitive Network With Energy Harvesting

The unmanned aerial vehicle (UAV) assisted transmission can significantly improve the spectrum efficiency and coverage of the wireless communication network. The paper proposed a cooperative secrecy transmission mechanism, which can take advantage of transmitter signal of primary user (PU) as a dedicated radio frequency (RF) source with decode and forward (DF) UAV selection and energy harvesting (EH) under cognitive network. Specifically, the transmitting signal of PU in the cognitive network can be viewed and used as energy to drive secondary user (SU) nodes and multi-relay nodes to send signals. It was worth noting that the DF UAV relay may bring about the unexpected noise and decrease the received signal to noise ratio (SNR), therefore, the multiple UAV assisted relays selected with secrecy capacity maximization criteria under cognitive network was proposed and investigated in detail, where the destination node equipped with multiple antennas and adopted the optimal antenna selection receiver. Moreover, By using the function analysis method, the closed expressions of the system secrecy outage probability (SOP) and the probability of non-zero secrecy capacity were calculated and derived accurately. Furthermore, the asymptotic expressions of the UAV assisted relay system under the large SNR cases were analyzed in detail, where the expressions of secrecy diversity order and secrecy diversity gain of the UAV assisted relay cognitive system were obtained thoroughly. Simulation results verified the effectiveness of the proposed mechanism and the correctness of the calculation.

Forward neutron energy spectra at s = 7TeV

Different event generators are used to simulate proton–proton collisions at the center-of-mass energy [Formula: see text] TeV to predict the forward neutron energy spectra. The predictions from different models — DPMJETIII, Sibyll2.3c, QGSJETII-04 and EPOS-LHC — are compared with experimental data from the LHCf detector in three different regions of pseudorapidity — [Formula: see text], [Formula: see text] and [Formula: see text]. Although, the models follow tracks of the experimental data, there is a clear mismatch between the models and experimental data, and among the models as well.

Research on novel spatial structure of power generation of spherical robot

Continuous energy supply is essential to spherical mobile robot in the Antarctic investigation. This paper puts forward energy harvesters that can generate electricity from the wind to achieve the long time and the long range exploration. The major contribution is to present the preliminary models of the energy harvester which uses the law of electromagnetic induction, and meanwhile the spatial structures about generating electricity are analyzed, and the influence of different structures on the power generation and efficiency will be obtained. In order to get the characteristics of power generation efficiency, this paper designs one element pipeline model and two element pipeline model, and then the motion of magnet in harvester will be simulated in different installed structures and wind speed. The varying rules of induced voltage are concluded at last. Finally, experiments are implemented based on the simulated model. The experimental results verify the dependability of different structural schemes of the robot and the validity of induced voltages’ varying rules. The results show that the induced electromotive force value obtained by the one element pipeline structure model is larger than the two element pipeline model, but the stability of the latter is better. Through the research in this paper, it can provide a basis for selecting a suitable spherical robot space structure according to the environmental conditions to improve the endurance.