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The purpose of this paper is to establish groups of stakeholders who win and lose from changes in natural gas prices and to develop practical recommendations for a state regulator for the optimal setting natural gas prices in the domestic market through an example of Ukraine.

In this study, to identify groups of stakeholders with gains and losses from the pricing of natural gas, the author used traditional methods of correlation and statistical regression analysis, including the ordinary least squares (OLS) method.

The main profit from natural gas remains in the extraction sector. The remaining profit is distributed among the various stakeholders. The consumers during rapidly rising gas prices have to rely on energy efficiency and switching to alternative, less costly resources. The existing system of unified natural gas price for all industrial consumers is inefficient and leads to the losses of the largest industrial sectors in Ukraine – metallurgy and chemical industry. With the help of the developed models, the author determined the critical levels of natural gas prices for these two industries.

The study is limited by data about activity of eight key manufacturing companies, four gas distribution companies, and main state gas companies from two country only.

Defined levels can be used by a state regulatory authority as a boundary, above which these industries will be unprofitable and their fate along with hundred thousands of workers will be questionable.

This is the first paper that set the critical levels of natural gas prices for two manufacturing industries in Ukraine.

The purpose of this paper is to investigate the gas flow characteristics in near wall region and the velocity slip phenomenon on the wall in nano-channels based on the molecular dynamics simulation.

An external gravity force was employed to drive the flow. The density and velocity profiles across the channel, and the velocity slip on the wall were studied, considering different gas temperatures and gas-solid interaction strengths.

The simulation results demonstrate that a single layer of gas molecules is adsorbed on wall surface. The density of adsorption layer increases with the decrease of gas temperature and with increase of interaction strength. The near wall region extents several molecular diameters away from the wall. The density profile is flatter at higher temperature and the velocity profile has the traditional parabolic shape. The velocity slip on the wall increases with the increase of temperature and with decrease of interaction strength linearly. The average velocity decreases with the increase of gas-solid interaction strength.

This research presents gas flow characteristics in near wall region and the velocity slip phenomenon on the wall in nano-channels. Some interesting results in nano-scale channels are obtained.

Face contact has a strong impact on the service life of non-contacting gas face seals; the current research which mainly focuses on the face contact had appeared during the startup or shutdown operation. This paper aims to present a closed-form contact model of a gas face seal during the opened operation.

Referring to the axial rub-impact model of rotor dynamics, a closed-form contact model is developed under a nonparallel plane contact condition that corresponds to the local face contact of sealing rings arising from some disturbances during the opened operation. The closed-form contact model and a direct numerical contact model are performed on Gaussian surfaces to compare the contact behavior.

The closed-form contact model is in a good agreement with the direct numerical contact model. However, the closed-form contact model cannot involve the influence of grooves on the sealing ends. The error is eliminated in some other types of gas face seals such as coned gas face seals. Besides non-contacting face seals, the closed-form model can be applied to the axial rub impact of rotor dynamics.

A closed-form contact model of a gas face seal is established during the opened operation. The closed-form contact model is validated by a direct numerical contact model. The closed-form contact model also suits for axial rub-impact of rotor dynamics.

The objective of this study is to model the influence of free gas, in the form of size‐distributed fine bubbles, on sound attenuation and dispersion in a thin‐walled elastic cylindrical tube filled with viscoelastic polymeric liquid.

Sound wave propagation in the system is described within a three‐phase interaction scheme, based on a quasi‐homogeneous approach to liquid‐gas mixture dynamics in the wave. Coupled equations of tube wall deformations and viscoelastic liquid dynamics in the tube are solved using a long‐wave approximation. The dissipative losses, stemming from flow gradients in the wave, as well as from non‐equilibrium bubble‐liquid interaction, are accounted for. The dispersion equation for the waveguide is obtained and studied numerically.

The results of the study indicate that bubble‐size distribution in viscoelastic liquid has an essential impact on sound propagation in the tube at sufficiently high frequencies. The frequency range in which the mixture heterogeneity influences the acoustic properties of the system is sensitive to both the distribution parameters and the rheological properties of the liquid. As distinct to polydispersity features, the viscoelastic properties of liquid are also relevant in the low‐frequency range, where they lead to an increase of the wave speed and a decrease of its attenuation.

A model of sound wave propagation in a tube filled with a heterogeneous viscoelastic liquid‐bubble mixture is formulated. The study provides a basis for modeling transient processes in tubes filled with polymeric liquids containing free gas, and for acoustic control of certain processes in polymer technologies.

This paper aims to study and assess a new approach for prediction of changes of pressure during gas discharge inside the room protected by fixed gaseous extinguishing system by computational fluid dynamics (CFD) simulations.

The research program consisted of two stages. The first stage was dedicated to the experimental measurements of pressure changes during extinguishing gas discharge into the test chamber in a real scale (70 m³), for two relief openings that differ in their area. The next step was about performing CFD simulations forecasting pressure changes during gas discharge into the numerically represented test chamber. Estimation of the correctness and usefulness of the CFD model was based on a comparison of the CFD results with standard calculations and experimental measurements.

Numerical modelling of pressure changes during the carbon dioxide discharge was very close to the experiment. The obtained results had sufficient accuracy (in most cases relative error <15%), while the standard approach predicted pressure changes with an average relative error over 36% and did not estimate the decrease of pressure at all.

Conducted research confirms the viability of the new approach in modelling the pressure changes and indicates additional benefits of the numerical analyses in the determination of the fire safety of protected premises.

The purpose of this paper is to investigate the continuing justification for linking the prices of European gas to those oil products.

The paper uses an analytic‐deductive approach supported by relevant analysis of data over a period of two decades.

Statistical analysis of the end‐uses of gas and oil products over the past two decades reveal that, with few exceptions, use of oil is increasing confined to transportation while gas is a utility fuel used to generate heat and power. The ability of end‐users to substitute oil products for gas – the principal justification for price linkage – has substantially diminished over the past two decades, and this trend is continuing. The implication of these findings is that nearly 20 percent of Europe's energy supplies are priced inappropriately with reference to a fuel which has little relevance to the supply/demand dynamics of natural gas. At levels of oil prices seen since 2003, this has significantly negative consequences for consumers. An important qualification to these findings is that in markets where prices have been set by gas to gas competition for many years – the UK and North America – a long‐term “natural correlation” between gas and oil prices has been observed.

The paper raises the important question facing European gas stakeholders and asks whether to remain with oil‐linked prices or move to spot market prices created at hubs in North West Europe.

The purpose of this paper is to ascertain the harm to personnel and equipment caused by an external explosion during natural gas explosion venting. The external explosion characteristics induced by the indoor natural gas explosion are the focal points of the investigation.

Computational fluid dynamics technology was used to investigate the large-scale explosion venting process of natural gas in a 6 × 3 × 2.5 m room, and the characteristics of external explosion under different scaled vent size (K_v = A_v/V2/3, 0.05, 0.08, 0.13, 0.18) were numerically analyzed.

When K_v = 0.08, the length and duration of the explosion fireball are 13.39 and 450 ms, respectively, which significantly expands the degree and range of high-temperature hazards. The suitable flow-field structure causes the external explosion overpressure to be more than twice that indoors, i.e. the natural gas explosion venting overpressure may be considerably more hazardous in an outdoor environment than inside a room. A specific range for the K_v can promote the superposition of outdoor rupture waves and explosion shock waves, thereby creating a new overpressure hazard.

Little attention has been devoted to investigating systematically the external explosion hazards. Based on the numerical simulation and the analysis, the external explosion characteristics induced by the indoor large-scale gas explosion were obtained. The research results are theoretically significant for mitigating the effects of external gas explosions on personnel and equipment.

This paper's aim is to propose a quasi‐steady numerical model of a solid rocket motor that includes the coupling of motor chamber gas dynamics with the composite solid propellant combustion.

The paper considers a model problem of steady‐state burning of a pure monopropellant coupled with a quasi‐steady gas dynamic model of the combustion chamber. In order to simulate the time evolution as the propellant burns back with time, the flow‐field in the chamber, the burning rate and the linear response function parameters are calculated for three port diameters of a simple cylindrical geometry.

It is shown that the pressure‐coupled linear response function remains approximately constant along the propellant surface but can change very strongly as the chamber pressure rises due to increase in the burn surface.

Only simplified motor geometry is considered but more realistic geometries can also be analyzed using a similar approach.

This study is the first step in building a comprehensive fully coupled model for numerical simulation of the internal flow‐fields of solid rocket motors. In addition, it demonstrates how to use the steady‐state results to calculate linearized pressure‐coupled response of the propellant.

This paper attempts to investigate the impact of the Russia–Ukraine war on the returns and volatility of the United States (US) natural gas futures market.

The study uses secondary data of 996 trading day provided by the US Department of Energy and investing.com websites and applies the event study methodology in addition to the generalized autoregressive conditional heteroscedastic (GARCH) family models.

The findings from the exponential EGARCH (1,1) estimate are the best indication of a significant positive effects of the Ukraine–Russia war on the returns and volatility of the US natural gas futures prices. The cumulative abnormal returns (CARs) of the event study show that the natural gas futures prices reacted negatively but not significantly to the Russian–Ukraine war at the event date window [−1,1] and the [−15, −4] event window. CARs for the longer pre and post-event window display significant positive values and coincides with the standard finance theory for the case of the US natural gas futures over the Russia–Ukraine conflict.

This is the first study to examine the impact of the Russia–Ukraine war on natural gas futures prices in the United States. Thus, it provides indications on the behavior of investors in this market and proposes new empirical evidence that help in investment analyses and decisions.

A numerical simulation of a two‐phase dilute flow (droplet‐gas mixture) is carried out by using a finite volume method based on Riemann solvers. The computational domain represents a one‐ended pipe with holes at its upper wall which lead into an enclosure. The aim of this study is to determine the parameters of such a flow. More specially, an analytical solution is compared with numerical results to assess the mass flow rates through the vents in the pipe. Inertia effects dominate the dynamic behaviour of droplets, which causes a non‐homogeneous flow in the cavity. The unsteady effects are also important, which makes isentropical calculation irrelevant and shows the necessity of the use of CFD tools to predict such flows. No relation can be extracted from the numerical results between the gas and the dispersed mass flow rates across the holes. But a linear variation law for the droplet mass flow versus the position of the holes is pointed out, which is independent of the incoming flow when the evaporating effects are quite low.