Energy Dynamics Research Articles

A Flow Dynamic Characteristic Analysis of A Single Radial Swirler Combustor

Abstract A diffusion combustor with a single radial swirler in non-reacting condition is investigated via a large eddy simulation (LES). Three dynamic analysis methods – the fast Fourier transform (FFT), proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) – are implemented to investigate the flow dynamic characteristics of the combustor. The kerosene-air combustor analyzed in the study was designed by the German Aerospace Center (DLR). It has a square cross-section and uses kerosene as fuel, which is modeled as a pre-vaporized and surrogated fuel consisting of 242 species. The first tangential(1T) mode in combustor caused by the swirler emerges dominantly in the combustor. This 1T mode exhibits the largest amount energy in the combustor dynamics, as verified by POD, and the DMD analysis determines the frequency of 1876.8 Hz. The fuel injector dynamics is associated with Helmholtz resonator frequency of 816.5 Hz. To analyze the instability, the DMD method is employed to investigate the growth rate of the most dominant dynamic structure.

Seasonal Variations of Titan's Brightness

AbstractThe absolute brightness of astronomical bodies can be represented by the emitted power, which plays important roles in their radiated energy budgets. The Cassini observations include three seasons of Titan, which provides an unprecedented opportunity to examine the seasonal variations of Titan's emitted power. Our analyses show that Titan's emitted power displays different seasonal behaviors between the Northern Hemisphere and the Southern Hemisphere. The global‐average emitted power decreased by 6.8 ± 0.4% during the Cassini period (2004–2017). Such a temporal variation represents the magnitude of the seasonal cycle of Titan's emitted power, which is at least one order of magnitude stronger than the seasonal variation of Earth's emitted power (<0.5%). More importantly, the ~6.8% decrease of the emitted power is much smaller than the ~18.6% decrease of the solar flux from the change of Sun‐Titan distance, implying a significantly dynamical energy budget on Titan.

Looking for interactions in the cosmological dark sector

We study observational signatures of non-gravitational interactions between the dark components of the cosmic fluid, which can be either due to creation of dark particles from the expanding vacuum or an effect of the clustering of a dynamical dark energy. In particular, we analyse a class of interacting models (Λ(t)CDM), characterised by the parameter α, that behaves at background level like cold matter at early times and tends to a cosmological constant in the asymptotic future. Our analysis improves previous works, where only the position of the Cosmic Microwave Background (CMB) first peak and supernova and LSS data where used, considering for the first time both background and primordial perturbations evolutions of the model. We use full spectra of the CMB Planck data together with late time observations, such as the Joint Light-curve Analysis (JLA) supernovae data, the Hubble Space Telescope (HST) measurement of the local value of the Hubble-Lemaȋtre parameter, and primordial deuterium abundance from Lyα systems to test the observational viability of the model and some of its extensions, adapting an Einstein-Boltzmann solver code for our purpose. We found that there is no preference for values of α different from zero (characterising interaction), even if there are some indications for positive values when the minimal Λ(t)CDM model is analysed. When extra degrees of freedom in the relativistic component of the cosmic fluid are considered, the data favour negative values of α, which means an energy flux from dark energy to dark matter.

Reconstruction of dynamical dark energy potentials: Quintessence, tachyon and interacting models

Dynamical models for dark energy are an alternative to the cosmological constant. It is important to investigate properties of perturbations in these models and go beyond the smooth FRLW cosmology. This allows us to distinguish different dark energy models with the same expansion history. For this, one often needs the potential for a particular expansion history. We study how such potentials can be reconstructed obtaining closed formulae for potential or reducing the problem to quadrature. We consider three classes of models here: tachyons, quintessence, and, interacting dark energy. We present results for constant w and the CPL parameterization. The method given here can be generalized to any arbitrary form of w(z).

Testing deviations from GR at cosmological scales including dynamical dark energy, massive neutrinos, functional or binned parametrizations, and spatial curvature

We introduce a new version of the Integrated Software in Testing General Relativity (ISiTGR) which is a patch to the software CAMB and CosmoMC. ISiTGR is intended to test deviations from GR at cosmological scales using cosmological data sets. While doing so, it allows for various extensions to the standard flat $\Lambda$CDM model. In this new release, we have support for the following: 1) dynamical dark energy parametrizations with a constant or time-dependent equation of state; 2) a consistent implementation of anisotropic shear to model massive neutrinos throughout the full formalism; 3) multiple commonly-used parametrizations of modified growth (MG) parameters; 4) functional, binned and hybrid time- and scale-dependencies for all MG parameters; 5) spatially flat or curved backgrounds. ISiTGR is designed to allow cosmological analyses to take full advantage of ongoing and future surveys to test simultaneously or separately various extensions to the standard model. We describe here the formalism and its implementation in the CMB code, the Integrated Sachs-Wolfe (ISW) effect, and the 3x2 point statistics. Next, we apply ISiTGR to current data sets from Planck-2018, Planck-2015, Dark Energy Survey YR1 release, Baryonic Acoustic Oscillations (BAO), Redshift Space Distortions (BAO/RSD) from the BOSS Data Release 12, the 6DF Galaxy Survey and the SDSS Data Release 7 Main Galaxy Sample, and Supernova from the Pantheon compilation, joint SNLS/SDSS data analysis and the Hubble Space Telescope. We derive constraints on MG parameters for various combinations of the five features above and find that GR is consistent with current data sets in all cases. The code is made publicly available at \url{https://github.com/mishakb/ISiTGR}.

Dark Sector in Cosmology: Dark Energy on Cosmological and Astrophysical Scales

The properties and observational manifestations of the dynamical dark energy on the cosmological and astrophysical scales are discussed. We consider the dynamical dark energy in the form of quintessential and phantom scalar fields with different parameters of the equation of state and the effective sound speed. The evolution of the dynamical dark energy and its impact on the dynamics of expansion of the Universe, halos, and voids, and its behavior in the static gravitational fields of astrophysical objects are analyzed. The current state and possible tests designed to establish the nature of dark energy are highlighted.

Bending of light in a universe filled with quintessential dark energy

As a local effect of dynamical dark energy, bending of light in the presence of a spherically symmetric and static black hole surrounded by quintessence has been studied. Having in mind recent observational data, we have treated the problem as a deviation from Kottler space-time. This deviation is measured by a perturbation parameter $\varepsilon$ included in the equation of state parameter of quintessence as $\omega_q=-1+\frac{1}{3}\varepsilon$. Here, the deflection angle is calculated and then the result is compared with \cite{Arakida:2011th} in the limit $\varepsilon\rightarrow 0$ where the quintessence behaves like the cosmological constant. It is shown that unlike the cosmological constant, the effect of quintessence on the photon energy equation can not be absorbed into the definition of impact parameter. Moreover in this paper, we generalize the Kiselev black hole to the case that there is a modified Chaplygin gas as the dark energy component of the universe and show that the resulted metric can be reduced to the Kiselev metric by adjusting some arbitrary parameters.

Observational Constraints on Dynamical Dark Energy with Pivoting Redshift

We investigate the generalized Chevallier–Polarski–Linder (CPL) parametrization, which contains the pivoting redshift z p as an extra free parameter, in order to examine whether the evolution of the dark energy equation of state can be better described by a different parametrization. We use various data combinations from cosmic microwave background (CMB), baryon acoustic oscillations (BAO), redshift space distortion (RSD), weak lensing (WL), joint light curve analysis (JLA), and cosmic chronometers (CC), and we include a Gaussian prior on the Hubble constant value, in order to extract the observational constraints on various quantities. For the case of free z p we find that for all data combinations it always remains unconstrained, and there is a degeneracy with the value of the dark energy equation of state w 0 p at z p . For the case where z p is fixed to specific values, and for the full data combination, we find that with increasing z p the mean value of w 0 p slowly moves into the phantom regime, however the cosmological constant is always allowed within 1 σ confidence-level. In fact, the significant effect is that with increasing z p , the correlations between w 0 p and w a (the free parameter of the dark energy equation of state quantifying its evolution with redshift), change from negative to positive, with the case z p = 0 . 35 corresponding to no correlation. The fact that the two parameters describing the dark energy equation of state are uncorrelated for z p = 0 . 35 justifies why a non-zero pivoting redshift needs to be taken into account.

Interacting scenarios with dynamical dark energy: Observational constraints and alleviation of the H0 tension

We investigate interacting scenarios which belong to a wider class, since they include a dynamical dark energy component whose equation of state follows various one-parameter parametrizations. We confront them with the latest observational data from Cosmic Microwave Background (CMB), Joint light-curve (JLA) sample from Supernovae Type Ia, Baryon Acoustic Oscillations (BAO), Hubble parameter measurements from Cosmic Chronometers (CC) and a gaussian prior on the Hubble parameter $H_0$. In all examined scenarios we find a non-zero interaction, nevertheless the non-interacting case is allowed within 2$\sigma$. Concerning the current value of the dark energy equation of state for all combination of datasets it always lies in the phantom regime at more than two/three standard deviations. Finally, for all interacting models, independently of the combination of datasets considered, the estimated values of the present Hubble parameter $H_0$ are greater compared to the $\Lambda$CDM-based Planck's estimation and close to the local measurements, thus alleviating the $H_0$ tension.

Condensed matter physics, hybrid energy and entropy principles, and the hybrid first and second laws of thermodynamics

In this paper, we develop an energy-based, large-scale hybrid dynamical system model to present a generic framework for hybrid thermodynamics involving hybrid energy and entropy conservation and nonconservation principles. Specifically, using a hybrid compartmental dynamical system energy flow model we develop a hybrid state-space dynamical system formalism for addressing critical phenomena and discontinuous phase transitions in thermodynamics and provide hybrid extensions to the first and second laws of thermodynamics. In addition, using Lyapunov stability theory for impulsive differential equations, we show that our hybrid large-scale thermodynamic energy flow model has convergent trajectories to Lyapunov stable equilibria determined by the system initial subsystem energies. Moreover, we show that the steady-state distribution of the hybrid large-scale system energies is uniformly distributed over all of the subsystems, leading to system energy equipartitioning corresponding to a maximum entropy equilibrium state.

Dynamical cosmologies in Eddington-inspired-Born–Infeld theory

In this paper, we study the cosmological evolution of the universe filled with a perfect fluid in the Eddington-inspired-Born–Infeld gravity. Applying an alternative method in which the evolution of the scale factor for this theory is linked to the cosmographic parameters, we obtain a dynamical dark energy solution where the singularity (through a regular bounce or a loitering phase) still can be avoided for [Formula: see text] with [Formula: see text]. For the range [Formula: see text], the results lead us to universes that experience an unlimited rate of expansion with finite density. Also, we obtain a possible maximum value of [Formula: see text] at the cosmic bounce point.

Cosmological instabilities and the role of matter interactions in dynamical dark energy models

We consider cosmological models with a dynamical dark energy field, and study the presence of three types of commonly found instabilities, namely ghost (when fields have negative kinetic energy), gradient (negative momentum squared) and tachyon (negative mass squared). In particular, we study the linear scalar perturbations of theories with two interacting scalar fields as a proxy for a dark energy and matter fields, and explicitly show how canonical transformations relate these three types of instabilities with each other. We generically show that low-energy ghosts are equivalent to tachyonic instabilities, and that high-energy ghosts are equivalent to gradient instabilities. Via examples we make evident the fact that whenever one of these fields exhibits an instability then the entire physical system becomes unstable, with an unbounded Hamiltonian. Finally, we discuss the role of interactions between the two fields, and show that whereas most of the time interactions will not determine whether an instability is present or not, they may affect the timescale of the instability. We also find exceptional cases in which the two fields are ghosts and hence the physical system is seemingly unstable, but the presence of interactions actually lead to stable solutions. These results are very important for assessing the viability of dark energy models that may exhibit ghost, gradient or tachyonic modes.

Planck 2015 constraints on spatially-flat dynamical dark energy models

We determine constraints on spatially-flat tilted dynamical dark energy XCDM and $\phi $CDM inflation models by analyzing Planck 2015 cosmic microwave background (CMB) anisotropy data and baryon acoustic oscillation (BAO) distance measurements. XCDM is a simple and widely used but physically inconsistent parameterization of dynamical dark energy, while the $\phi $CDM model is a physically consistent one in which a scalar field $\phi $ with an inverse power-law potential energy density powers the currently accelerating cosmological expansion. Both these models have one additional parameter compared to standard $\varLambda $CDM and both better fit the TT + lowP + lensing + BAO data than does the standard tilted flat-$\varLambda $CDM model, with $\Delta \chi ^{2} = -1.26\ (-1.60)$ for the XCDM ($\phi $CDM) model relative to the $\varLambda $CDM model. While this is a 1.1$\sigma $ (1.3$\sigma $) improvement over standard $\varLambda $CDM and so not significant, dynamical dark energy models cannot be ruled out. In addition, both dynamical dark energy models reduce the tension between the Planck 2015 CMB anisotropy and the weak lensing $\sigma _{8}$ constraints.

Influence of the correlation prior on reconstruction of the dark energy equation of state

Non-parametric reconstruction of the dark energy equation of state (EoS) aims to determine the EoS as a function of redshift without invoking any particular dark energy model, so that the resulting EoS can be free of model-induced biases or artifacts. Without proper regularization, however, such reconstruction is often overwhelmed by the noise of poorly constrained modes. An intuitive regularization scheme is to assume a priori the dark energy EoS to evolve at most slowly with time, which may be enforced by a correlation between the EoS at different epochs. Indeed, studies that impose the correlation prior are able to significantly reduce the uncertainties of the reconstructed EoS and even show hints for dynamical dark energy. In this work, we examine the correlation prior using mock datasets of type Ia supernovae (SNe Ia), baryonic acoustic oscillations (BAOs), age-derived Hubble parameter, Hubble constant, and cosmic microwave background. We find that even though the prior is designed to disfavor evolving equations of state, it can still accommodate spurious oscillating features at high significance. Within the 1000 mock datasets of existing observations that are generated for the concordance cosmological model, i.e., the input dark energy EoS w=−1, there are 688 (69) cases recovering an EoS that departs from −1 by more than 1σ (2σ) in one or more redshift bins. The reconstructed EoS turns up and down markedly in many cases. Moreover, inverting the signs of the randomly assigned errors of the mock data more or less reverses the behavior of the EoS. Spurious results occur even more frequently when idealized SN Ia and BAO data from future surveys are included. Our tests suggest that further studies are needed to ensure accurate reconstruction of the EoS with the correlation prior.

Screening Lambda in a new modified gravity model

We study a new model of Energy-Momentum Squared Gravity (EMSG), called Energy-Momentum Log Gravity (EMLG), constructed by the addition of the term f(T_{mu nu }T^{mu nu })=alpha ln (lambda ,T_{mu nu }T^{mu nu }), envisaged as a correction, to the Einstein–Hilbert action with cosmological constant Lambda . The choice of this modification is made as a specific way of including new terms in the right-hand side of the Einstein field equations, resulting in constant effective inertial mass density and, importantly, leading to an explicit exact solution of the matter energy density in terms of redshift. We look for viable cosmologies, in particular, an extension of the standard Lambda CDM model. EMLG provides an effective dynamical dark energy passing below zero at large redshifts, accommodating a mechanism for screening Lambda in this region, in line with suggestions for alleviating some of the tensions that arise between observational data sets within the standard Lambda CDM model. We present a detailed theoretical investigation of the model and then constrain the free parameter alpha ', a normalisation of alpha , using the latest observational data. The data does not rule out the Lambda CDM limit of our model (alpha '= 0), but prefers slightly negative values of the EMLG model parameter (alpha '= -0.032pm 0.043), which leads to the screening of Lambda . We also discuss how EMLG relaxes the persistent tension that appears in the measurements of H_0 within the standard Lambda CDM model.

Dynamical energy analysis applied to real-world structures—New developments

Dynamical Energy Analysis (DEA) has been established as a mesh-based ray tracing method working at mid-to-high excitation frequencies for structure-borne sound on complex vehicle structures. Unless standard ray-tracing used, for example, in room acoustics and following long rays through a series of specular reflections, DEA is based on an integral representation by (a) reformulating the energy transport problem in terms of ray densities and linear matrix equations and by (b) applying the ray tracing directly on preexisting meshes used also in, for example, FEM calculations. The advantage is that DEA can be used as a drop-in replacement for FEM tool working on the same meshes but determining results at very high frequencies. In order to achieve this, a so-called transfer matrix has to be created and later solved for the energy equilibrium distribution. In this presentation, we address recent developments in making DEA an efficient black-box tool for mid- to high-frequency vibrations including convergence issues and suitable preprocessor applications, sound radiation from DEA calculations as well as verification and validation studies.Dynamical Energy Analysis (DEA) has been established as a mesh-based ray tracing method working at mid-to-high excitation frequencies for structure-borne sound on complex vehicle structures. Unless standard ray-tracing used, for example, in room acoustics and following long rays through a series of specular reflections, DEA is based on an integral representation by (a) reformulating the energy transport problem in terms of ray densities and linear matrix equations and by (b) applying the ray tracing directly on preexisting meshes used also in, for example, FEM calculations. The advantage is that DEA can be used as a drop-in replacement for FEM tool working on the same meshes but determining results at very high frequencies. In order to achieve this, a so-called transfer matrix has to be created and later solved for the energy equilibrium distribution. In this presentation, we address recent developments in making DEA an efficient black-box tool for mid- to high-frequency vibrations including convergence i...

Dynamical energy analysis—An efficient mesh based simulation tool for mid-to-high frequency structure-borne sound calculations

Modelling the vibro-acoustic response of mechanical built-up structures is a challenging task—especially in the mid to high frequency regime—even with the computing powers available today. Standard modelling tools such as Finite Element Methods (FEM) are not scalable to high frequencies due to the prohibitive increase in model size. Typical high frequency methods such as the Statistical Energy Analysis (SEA) on the other hand, often lack details of the structure and require care in the setting up the model. In this talk, I will review the Dynamical Energy Analysis (DEA)—a method bridging the gap between the low and very high frequency range. DEA describes the energy flow in a complex structure keeping the directional information of energy propagation. It can be set up directly on meshed structures thus providing detailed spatial information about the vibrational energy of a built-up structure of high complexity. The response of coupling coefficients between sub-components are obtained through local wave models integrated into the global DEA treatment. The computational cost of DEA is frequency independent making it possible to get results from the mid-to-high frequency regime. The method can be extended to include sound radiation calculations in a post-processing step. The new method has been validated both using FEM computations and experiments in collaboration with Yanmar Co., Ltd., a Japanese tractor manufacturer. Further applications in the car, aerospace and ship building industry will be presented.Modelling the vibro-acoustic response of mechanical built-up structures is a challenging task—especially in the mid to high frequency regime—even with the computing powers available today. Standard modelling tools such as Finite Element Methods (FEM) are not scalable to high frequencies due to the prohibitive increase in model size. Typical high frequency methods such as the Statistical Energy Analysis (SEA) on the other hand, often lack details of the structure and require care in the setting up the model. In this talk, I will review the Dynamical Energy Analysis (DEA)—a method bridging the gap between the low and very high frequency range. DEA describes the energy flow in a complex structure keeping the directional information of energy propagation. It can be set up directly on meshed structures thus providing detailed spatial information about the vibrational energy of a built-up structure of high complexity. The response of coupling coefficients between sub-components are obtained through local wave m...

Physicochemical Properties of analogs α-Aminophosphonates Drugs Determined via Molecular Dynamics Simulation

Objective: Cyclin-dependent kinases (CDKs, play important roles in cell cycle regulation. Since deregulation of cyclins and/or alteration or absence of inhibitors has been associated with many cancers, there is strong interest in CDKs inhibitors that could play an necessary role in the discovery of a new family of antitumor agents. Material and Methods: Molecular modeling is used to design new materials, which the correct prediction of physical properties of realistic systems is required. Gromacs is an tool to perform molecular dynamics simulations and energy minimization of bimolecular systems which commonly consists of several tens to thousands of amino acid residues. From the simulations the first 100 ps were regarded as equilibration, leaving 900 ps for analysis purposes. Results: Thermodynamic properties density, potential energy, temperature, and pressure are given. In this results tetramethyl ((1,4-phenylenebis (azanediyl)) bis ((4-chlorophenyl) methylene)) bis (phosphonate) was found to be the better selective known inhibitor for cyclin-dependent kinase2 because it shown lowest energy.Conclusion: The phosphoric acid moiety is considered to bind to the affected protein more actively than the corresponding carboxylic acid because of its di anionic character.

Tantalizing new physics from the cosmic purview

The emergence of a highly improbable coincidence in cosmological observations speaks of a remarkably simple cosmic expansion. Compelling evidence now suggests that the Universe’s gravitational horizon, coincident with the better known Hubble sphere, has a radius improbably equal to the distance light could have traveled since the Big Bang. The confirmation of this unexpected result would undoubtedly herald the influence of new physics, yet appears to be unavoidable after a recent demonstration that the Friedmann–Lemaître–Robertson–Walker metric is valid only for the so-called zero active mass equation of state. As it turns out, a cosmic fluid with this property automatically produces the aforementioned equality, leaving little room for a cosmological constant. The alternative — a dynamical dark energy — would suggest an extension to the Standard Model of particle physics and a serious re-evaluation of the Universe’s early history.

Future constraints on dynamical dark-energy using gravitational-wave standard sirens

The detection of gravitational waves (GW) by the LIGO and Virgo collaborations offers a whole new range of possible tests and opens up a new window which may shed light on the nature of dark energy and dark matter. In the present work we investigate how future gravitational waves data could help to constrain different dynamical dark energy models. In particular, we perform cosmological forecastings of a class of well known and most used dynamical dark energy models using the third-generation gravitational wave detector, the Einstein Telescope. We have considered 1000 simulated GW events in order to constrain the parameter space of the dynamical dark energy models. Our analyses show that the inclusion of the GW data from the Einstein Telescope, significantly improves the parameter space of the dynamical dark energy models compared to their constraints extracted from the standard cosmological probes, namely, the cosmic microwave observations, baryon acoustic oscillations distance measurements, Supernove type Ia, and the Hubble parameter measurements.