Energetic Approach Research Articles

Dynamical response of a perfectly premixed flame and limit behavior for high power density systems

The interaction between a perfectly premixed flame and an acoustic wave is studied in a 1D configuration. The mathematical framework to represent the flame dynamics is based on a recent work by Chen et al. that accounts for flame displacement in an acoustic field (Chen et al., 2016). An energetic approach is developed to estimate the source terms associated to flame/acoustic interactions. Three main contributions are identified: the flame velocity response, which corresponds to the flame response to upstream velocity perturbations (often modeled by an n−τ model), the flame pressure response, related to the link between the reactant consumption rate and the local density, and the flame motion contribution, related to the displacement of the heat release rate in an acoustic pressure field. The energetic contributions are evaluated theoretically using different formalisms to make connections with previous work. A focus is made on the limit case corresponding to high frequency/high power density (HF/HPD) configurations. This asymptotic condition is of interest in some practical applications, and a remarkable expression is obtained for the flame contribution in that case. The acoustic source term is expressed simply by the integral of the product between the mean heat release rate and the acoustic energy. A parametric study is carried out on a 1D duct of constant section incorporating a perfectly premixed flame. The spatial structure and frequency of the first mode (which is studied exclusively here) are obtained using a classical decomposition of pressure, velocity and entropy in plane waves and expressing jump and boundary conditions on the amplitudes. The flame energetic contributions are compared to one another and to the growth rate obtained using the classical wave method. The different methods are validated on a wide range of parameters. The particular behavior of systems featuring a high power density is presented.

Structural damage localization from energy density measurements using an energetic approach

This paper presents a new damage detection strategy for structures, capable of identifying the defects from a set of energy density measurements, at medium and high frequencies. An inverse energetic approach, also called the inverse simplified energy method (IMES), is used for this purpose. It was first developed for the localization and the quantification of vibro-acoustic sources. The main novelty of this paper is to extend this inverse approach to the field of defects detection, to localize the flaw through the knowledge of the energy density field within the structure. A new numerical methodology is proposed in this paper for this purpose. Numerical simulations with different defect cases were performed to validate the presented method. Results show that IMES is an effective predictive tool in structural damage detection.

On mooring line tension and fatigue prediction for offshore vertical axis wind turbines: A comparison of lumped mass and quasi-static approaches

Despite several potential advantages, relatively few studies and design support tools have been developed for floating vertical axis wind turbines. Due to the substantial aerodynamics differences, the analyses of vertical axis wind turbine on floating structures cannot be easily extended from what have been already done for horizontal axis wind turbines. Therefore, the main aim of the present work is to compare the dynamic response of the floating offshore wind turbine system adopting two different mooring dynamics approaches. Two versions of the in-house aero-hydro-mooring coupled model of dynamics for floating vertical axis wind turbine (FloVAWT) have been used, employing a mooring quasi-static model, which solves the equations using an energetic approach, and a modified version of floating vertical axis wind turbine, which instead couples with the lumped mass mooring line model MoorDyn. The results, in terms of mooring line tension, fatigue and response in frequency have been obtained and analysed, based on a 5 MW Darrieus type rotor supported by the OC4-DeepCwind semisubmersible.

An Energetic Approach to Predict the Effect of Shot Peening-Based Surface Treatments

Almen intensity and surface coverage are well-known to be the defining parameters of shot peening-based surface treatments. These parameters are directly affected by material properties, the extension of the contact zone, the geometry of the impact pair, as well as the impact rate and velocity. Such intricate relationships have resulted in often dissimilar predictions of shot peening effects even while using an identical combination of Almen intensity and surface coverage. With the fast pace introduction of new generation impact-based surface treatments, there is a need to find a more widespread parameter that would facilitate the direct comparison of all different treatments and relate the main process parameters to the resultant mechanical characteristics. Herein, we propose to use an energy-based parameter to describe the peening process in a more widespread approach, which collectively incorporates the effects of the Almen intensity and surface coverage, as well as the diameter, material, and velocity of the impact media. A set of finite element analyses was developed to demonstrate the correlation of the peening process effects with this energetic approach. Comparisons with the experimental data served as proof of concept, confirming that the proposed method could provide a quite good estimation of the effect of peening parameters on the treated material.

Development of a new simple energy method for life prediction in multiaxial fatigue

In this paper, a new, simple Damage Energy Criterium for life prediction in multiaxial fatigue, developed in the frequency domain, is described and verified. The first aim of this paper is to demonstrate that through a correct use of the energetic approach, developed in the frequency domain, it is possible to achieve an accurate result. The proposed theoretical procedure finds its conceptual foundation in the fact that the energy criterion cannot be directly applied to usual stress state in the time domain; however, with a simple passage it is possible to accurately reduce a multiaxial stress state to an equivalent uniaxial one. For this reason, this work will be characterized by analytical content and by substantial mathematical demonstrations. At the end, in order to verify the method and consolidate the general procedure, some experimental tests are used to corroborate the validity of this criterion. This proposal shows drastically simpler technique than any other proposed in current literature.

Fracture Loads Prediction on Notched Short Glass Fibre Reinforced Polyamide 6 Using the Strain Energy Density

This paper provides an energetic approach useful for the prediction of critical loads on U-notched components without an ideally linear elastic behaviour. The methodology has been applied to 100 fracture specimens of short glass fibre reinforced polyamide 6 (SGFR-PA6), combining four different fibre contents (5, 10, 30 and 50 wt %) and five different notch radii (0.00, 0.25, 0.50, 1.00 and 2.00 mm). The proposal combines the application of the strain energy density criterion with the use of the whole absorbed energy in the tensile test (elastic-plastic area under the stress-strain curve). With all of this, the fracture loads have been well estimated in this type of material.

Isomers of the C84 fullerene: A theoretical consideration within energetic, structural, and topological approaches

ABSTRACTCurrently, there is no common conception on the stability and achievability of fullerene isomers under the arc-discharge synthesis conditions. Different approaches operate with energetic, structural, and topological parameters of the fullerene molecules to explain why some fullerene isomers are more preferable than the others. In the present work, we have selected the most appropriate approaches based on topological roundness, information entropy, nuclear volumes, and sphericities and compared their predictions with the relevant experimental data on the C84 fullerene isomers (obeying the isolated pentagon rule) and density functional theory estimates of their stability. We have found that the molecules of most stable (and most abundant) C84 isomers have the minimal extremal roundness, maximal sphericity, and largest volume and vice versa. In the case of the information entropy, no correlation is observed. Interestingly, the found correlation between the volume and the stability of the C84 isomers is unexpectedly inverse, i.e. more stable C84 isomers have larger inner cavities inside, though traditionally large volume is associated with instability of hollow framework molecules. We assume that the large volumes allows enhancing the sphericity of the fullerene cages as we found the last one favoring the stability and the unstable C84 fullerene cages having low volumes are far from the spherical shape. We think that the results obtained may be extrapolated to other fullerene isomeric sets and contribute to the understanding the grounds of the interconnection in the triad “topology – structure – energy” underlying structural chemistry.

Non-isothermal electrokinetics: energetic variational approach

Fluid dynamics accompanies with the entropy production thus increases the local temperature, which plays an important role in charged systems such as the ion channel in biological environment and electrodiffusion in capacitors/batteries. In this article, we propose a general framework to derive the transport equations with heat flow through the Energetic Variational Approach. According to thermodynamic first law, the total energy is conserved and we can then use the Least Action Principle to derive the conservative forces. From thermodynamic second law, the entropy increases and the dissipative forces can be computed with the Maximum Dissipation Principle. Combining these two laws, we then conclude with the force balance equations and a temperature equation. To emphasis, our method provide a self consistent procedure to obtain dynamical equations satisfying proper energy laws and it not only works for the charge systems but also for general systems.

Application of physical and energetic approach to estimation and selection of atmospheric protection systems for energetic devices

The air basin of cities is subjected to considerable pollution, including waste gases generated during the production of thermal and electric energy by power plants. However, power plants are an indispensable element of the life support system on urban areas and they can not be taken out of the city, that means minimizing losses, both material and energy. Therefore, the problem of the correct choice of structural elements and operating characteristics of the process and a system for reducing air pollution is becoming very important. The paper analyzes the most well-known and practical scientific approaches to the selection of optimal measures to reduce air pollution, their advantages and disadvantages are revealed. The authors have singled out the physical and energetic approach as the most acceptable one. The approach is based on the theory of dispersed systems stability, the analysis of the main provisions which allowed us to systematize the parameters of properties, energy parameters and stability of gaseous pollutants formed during the operation of power plants and to construct a scheme for the transformation of gaseous pollutants for the process of reducing air pollution has been performed. At the same time, stability is the resultant criterion characterizing the gaseous pollutants behavior.

A Simplified Waveform Energetics Approach to Interpreting Arterial and Venous Pressure

Abstract This paper develops a novel methodology for extracting simple, beat-to-beat, lumped metrics of systemic circulation performance by comparing the catheter pressure waveforms from the femoral artery and vena cava. Their diagnostic potential is compared to the similar, clinically used metric ΔMP, the drop in mean blood pressure between the aorta and vena cava, across an experimental cohort encompassing the progression of sepsis and several clinical interventions known to alter circulatory state. Both Ofe→vc, the model derived pressure attenuation between the femoral artery and vena cava, and the clinical metric, ΔMP, performed well. However, Ofe→vc reduced the optimal average time to sepsis detection from endotoxin infusion from 46.2 minutes for ΔMP to 11.6 minutes, for a slight increase in false positive rate from 1.8% to 6.2%. Thus, the potential diagnostic benefits of this novel approach are demonstrated, and a case is made for further investigation.

The technology of combined processing of extruded materials

The paper considers the peculiarities of combined processing of parts, made from extruded metal blanks with anisotropic electrotechnical properties. It involves the application of an electric field and seeks to achieve the required profile accuracy in any processing direction with precision within the specified tolerance for finishing operations. The study describes the specific nature of the development of current leads and the ways of achieving the required accuracy when combining electro-erosion and electrochemical components of the process in real time, taking account of the position of the pressing force vector relative to the direction of current flow in the zone of combined processing. This gives the opportunity to ensure the process stability and accuracy of processing advanced materials with a wide range of current conductivity variation in components, used when extruding blanks for precision parts. The study employs the methodology of calculating and assigning technological modes of combined processing, formed on the basis of the energetic approach and using the principle of similarity in technological systems. It also involves the adapted process management which allowed for elimination of unstable impacts affecting the accuracy of shape formation and surface layer quality, and expands the area of using combined processing for manufacturing extruded parts with anisotropic properties of components. The article presents the feasibility study of the ways of extending the work results to various types of products, particularly, to processing of welded and soldered joints of metallic materials and coated details where the replacement of traditional processing methods with combined ones significantly increases the opportunities for obtaining high-precision parts with required performance characteristics.

Fatigue investigation of complex weldments by the means of the local strain energy density approach

The paper investigates the use of an energetic approach based on the strain energy density failure criteria to predict the fatigue life of welded joints in aluminum alloy. The cited criterion has already been proved valid to assess the failure of components in presence of sharp and blunt notches, and several results are present in the literature for different materials. The geometry tested in the present work is a double V-grooved full penetration butt weld, subsequently heat treated, and loaded orthogonally to the welding direction with load ratio R=0. This configuration makes the weld toe a notch of great opening angle. The aim of the paper is to verify the soundness of the energetic criteria for this class of welded joints, comparing the tests results with the numerical predictions. In the computational part, the energy in a given volume can be computed directly from the nodal displacements, thus not needing the stress values. Differently from the stress intensity factor approach, this property allows to a fast computation of the strain energy density by the means of a coarse mesh. The results of different configurations of geometry and meshing are compared to find the simplest modeling scheme capable of providing an accurate estimate of the fatigue life of the joint.

Physical and energetic approach to providing solid wastes handling system with environmental safety

Implementation features of the principal directions of municipal solid wastes handling system activity (territorial, climatic, economical and others) have stipulated the development of different concepts regarding to urban territories wastes handling, the most known of which are: Complex Waste Management, European Waste Management system (German dual system); «Zero Waste» concept. Each of the above mentioned concepts have got both advantages and disadvantages from ecological, economical, social, technological and organizational and legal points of view. From a perspective of the urban infrastructure environmental safety, an ecological aspect is the most interesting. That is why a new approach is being studied based on the principal points of the Theory of disperse systems sustainability which is called Physical and Energetic Description Concept of the Processes of Environmental Pollution and Restriction of Environmental Pollution with Municipal Solid Wastes. On the basis of the analysis of the municipal solid wastes handling concepts applied in the world and using the principal points of the theory of dispersed system sustainability, the results of the initial stage of the research regarding to studying and classifying municipal solid wastes properties parameters, their energetic parameters and sustainability have been represented by the authors. Herewith, the municipal solid wastes sustainability is considered as a resulting criterion characterizing municipal solid wastes behavior in the environment and allowing to control their behavior with the purpose of sustainability restriction and as a result decreasing the environmental pollution.

Ultrafast stimulated emission of nitrophenolates in organic and aqueous solutions.

Early-time dynamics of nitroaromatics and its coressponding bases can give valuable insights into photo-induced reactions relevant to atmospheric and environmental processes. In this work, femtosecond broadband absorption spectroscopy between 350 and 700 nm has been applied to explore the ultrafast dynamics of o-, p- and m-nitrophenol anions (NP-) in basic organic and aqueous solution. Excitation at 400 nm promotes these compounds into the first bright electronic singlet state, which is a charge-transfer state. A surprising finding for all nitrophenolates was a characteristic, spectrally broad stimulated emission (SE) from the electronically excited state into the ground state. The corresponding lifetime was on the order of a few hundred femtoseconds for o- and p-NP- while it was roughly ten times larger for m-NP-. In line with earlier observations, the SE is governed by an out-of-plane torsional motion of the nitro group, leading to a close energetic approach of the relevant electronically excited singlet and ground states. Subsequent dynamics can be assigned to excited state absorption and ground state relaxation due to energy dissipation of the vibrational modes to the solvent that occur for up to several tens of picoseconds. No longer-lasting transient absorption (TA) was found; instead, a complete recovery of the ground state bleaching was observed indicating that triplet state relaxation is either not significantly involved in this spectral part or shifted to other regions. In the aqueous system, time constants for all processes are much smaller than in organic solution, a fact that can be explained by the larger dipole moment of the solvent and the correspondingly stronger intermolecular coupling between NP- and the aqueous solvent.

Local strain energy based fatigue assessment of cruciform welded joints: experimental data analysis and influence of hot-dip galvanization

Performing the fatigue assessment of a welded joint using the Notch Stress Intensity Factors [1] presents two major challenges. The first is the necessity of a precise reconstruction of the stress field around the notch tip, thus needing an extremely refined discretization with an evident computational cost. The other, is that the dimensions of the N-SIFs and so their critical values, vary accordingly to the William’s solution [2] depending on the notch-opening angle. Consequence of this is that the mechanical properties necessary for the assessment vary as a function of the geometry treated. The research to overcome this issue has led to the use of the local Strain Energy Density [3]. The power of this parameter, used as a tool to perform fatigue assessment, consists of having a very low mesh refinement sensitivity [4], being the energy computed directly from nodal displacements and stiffness matrix [5], and having constant dimensions, so constant critical value for a given class of materials. In this paper, the local energetic method is applied to the analysis of the results of a series of tests performed on cruciform load carrying and non-load carrying specimens realized by S235 JRG2 structural steel plates. If load carrying, the fillet welded joints are made of S355 J2+N structural steel. The fatigue testing has been performed in atmosphere at room temperature in as welded condition both with and without the corrosion protective zinc layer. Particularly, the interest is focused on the influence of the zinc layer of the fatigue properties of the joint and on the capability of the local energetic approach, confronted with the classic nominal stress approach, to accurately predict the fatigue failure. To conclude, the investigation of the tests executed reveals no significant difference in the fatigue life for the coated samples, compared with the uncoated specimens and the predictions according to the IIW recommendations [6].

Энергийный подход к взаимосвязи этики и метафизики как путь к философии свободы

Энергийный подход к взаимосвязи этики и метафизики как путь к философии свободы

Protein adsorption onto monoliths: A surface energetics study.

This part of work was done to explore the basic understanding of the adsorption chromatography by determining the interaction of selected model proteins (n = 5) to monolithic chromatographic materials, with varying densities of butyl and phenyl ligands. Surface energetics approach was applied to study the interaction behavior. The physicochemical properties of the proteins and monolithic chromatographic materials were explored by contact angle and zeta potential values. These values were used to study protein to monolith interaction under various operating conditions. Surface energetics approach allowed the calculation of interaction energy as a function of distance, i.e. energy minimum values. Calculations were performed at various conditions to analyze the effect of major operating parameters on the interaction strength. The interaction strength exposed the hydrophobic nature of the monoliths which increases with increasing ligand density. Further, interaction energy of proteins were higher with monolith with butyl ligand compared to monolith with phenyl ligand. For instance, lactoferrin interaction to monoliths with butyl represents more interaction, i.e. 24.38 kT as compared to monoliths with phenyl i.e. 23.28 kT, keeping lambda as 0.2 nm and salt concentration as 100mM of ammonium sulphate. Hence, more energy and time will be consumed for elution of proteins immobilized to monoliths with butyl. Similarly, the effect of solid surface for proteins immobilization, effect of ligand density and effect of lambda showed some interesting insights on the interaction behavior. The knowledge generated from the present work will help in the basic understanding as well as development of an efficient, low cost downstream processing design and may mimic the real chromatographic experiments.

The First and Second Law Analyses of Thermodynamics of Potato Slices Drying Process

The objective of the work being presented is to investigate thethermal performance of indirect, multi-tray solar drying system. Ex -pressions for exergy in, exergy out and exergy loss for flat plate solarcollector, drying chamber and trays kept in drying chamber were writ -ten under steady state conditions. Experiments were performed for 6to 8 hours on two days namely 14/03/2014 and 24/03/2014 and theobservations taken on 24/03/14 has been analyzed using Energetic andExegetic approach. The value of first law efficiency for flat plate solarcollector and solar dryer varied between 10% to 30.49% and 4.009% to9.45% respectively. Second law efficiency of solar collector and solardryer have been found varying from 0.7126% to 1.829%.and 49.85% to67.75% respectively. The Exergetic efficiency for tray 1, tray 2 and tray3 has been computed and these values varied from 90.43% to 93.412%,72.684% to 92.352% and 78.179% to 94.61% for each trays respectively.Considering heavy energy and exergy losses from flat plate solar collec -tor and drying chamber, the results of first Law and second Law efficien -cies are in fair agreement with each other.

On derivation of compressible fluid systems on an evolving surface

We consider the governing equations for the motion of compressible fluid on an evolving surface from both energetic and thermodynamic points of view. We employ our energetic variational approaches to derive the momentum equation of our compressible fluid systems on the evolving surface. Applying the first law of thermodynamics and the Gibbs equation, we investigate the internal energy, enthalpy, entropy, and free energy of the fluid on the evolving surface. We also study conservative forms and conservation laws of our compressible fluid systems on the evolving surface. Moreover, we derive the generalized heat and diffusion systems on an evolving surface from an energetic point of view. This paper gives a mathematical validity of the surface stress tensor determined by the Boussinesq-Scriven law. Using a flow map on an evolving surface and applying the Riemannian metric induced by the flow map are key ideas to analyze fluid flow on the evolving surface.

Errata to “Energetic variational approaches for incompressible fluid systems on an evolving surface”

Errata to “Energetic variational approaches for incompressible fluid systems on an evolving surface”