Two-component Flow Research Articles

AstroSat observation of non-resonant type-C QPOs in MAXI J1535-571

Galactic transient black hole candidate (BHC) MAXI J1535-571 was discovered on 2017 September 02 simultaneously by {\it MAXI}/GSC and {\it Swift}/BAT instruments. It has also been observed by India's first multi-wavelength astronomy-mission satellite {\it AstroSat}, during the rising phase of its 2017-18 outburst. We make both the spectral and the temporal analysis of the source during 2017 September 12-17 using data of {\it AstroSat}'s Large Area X-ray Proportional Counter (LAXPC) in the energy range of $3-40$~keV to infer the accretion flow properties of the source. Spectral analysis is done with the physical two-component advective flow (TCAF) solution-based {\it fits} file. From the nature of the variation of the TCAF model fitted physical flow parameters, we conclude and confirm that the source was in the intermediate spectral state during our analysis period. We observe sharp type-C quasi-periodic oscillations (QPOs) in the frequency range of $\sim 1.75-2.81$~Hz. For a better understanding of the nature and evolution of these type-C QPOs, a dynamic study of the power density spectra is done. We also investigate the origin of these QPOs from the shock oscillation model. We find that non-satisfaction of Rankine-Hugoniot conditions for non-dissipative shocks and not their resonance oscillations is the cause of the observed type-C QPOs.

Accretion Flow Properties of GRS 1915+105 During Its θ Class Using AstroSat Data

Abstract The Galactic microquasar GRS 1915+105 shows rich variability that is categorized into different classes. In this paper, we report the temporal and spectral analysis of GRS 1915+105 to study the properties of the accretion flow when the light curve shows θ class variability. For this purpose, we use the Large Area X-ray Proportional Counter data from the Target of Opportunity observations of India’s first multiwavelength astronomy satellite AstroSat. The θ class is marked by the recurrent appearance of U-shaped regions in the light curve, where the photon count rate first decreases rapidly and then increases slowly. For our analysis, we use U-shaped regions of the first two orbits (02345 and 02346) on 2016 March 4. In both cases, the dynamic power-density spectra (PDS) showed significant power at around 4–5 Hz, suggesting the presence of a low-frequency quasi-periodic oscillation (QPO) around that frequency interval. The QPO frequency is found to increase with time when the energy flux is also enhanced. From the evolution of the spectra, we determine the evolution of the accretion flow parameters in these two observations. Fitting the spectra with the transonic flow solution-based two-component advective flow (TCAF) model in the 4–25 keV energy band shows that the Keplerian disk accretion rate increases with the increase in radiation intensity, while the location of the centrifugal pressure-driven shock front decreases. In both these data, a gradual increment of power-law photon index with intensity is observed, suggesting the progressive softening of the source.

Two-Component Flow Measurement In Oil And Gas Pressure Systems

The article discusses a method for measuring the volumetric flow rate of a two-component (oil + air) flow using a cylindrical nozzle. The results of the study of the proposed meter for the flow rate of a two-component flow are presented. Satisfactory agreement was obtained between the calculation results of the two-component flow rate and the experimental data with allowance for air.

Research Of Oil Pipelines On Selling The Maximum Hydraulic Impact Pressure In A Two-Component Flow

The article is devoted to determining the intensity of hydraulic shock in pressure pipelines, taking into account the two-component flow. Based on the processing of the results of experimental studies, a dependence is proposed for calculating the maximum pressure during hydraulic shock. Достоверность полученной взаимосвязи доказана сопоставлением расчетных с опытными данными .

Ion temperature measurements from tomographic reconstruction of Doppler spectra in the presence of multi-component flow in two dimensions.

A new ion Doppler diagnostic has been constructed to measure ion temperature profiles in the presence of multi-component flow during magnetic reconnection experiments. The inversion technique and diagnostic setup are applicable to axisymmetric plasmas with two-component flow across the measurement cross section, which occurs during magnetic reconnection. The particular design discussed here is optimized for operation on the Magnetic Reconnection eXperiment (MRX) at Princeton Plasma Physics Laboratory. To prove the viability of this diagnostic for MRX and the future Facility for Laboratory Reconnection Experiments, measurements have been taken and ion temperature and perpendicular flow profiles have been obtained. The radial velocity on MRX does not contribute to the Doppler shift of the measured spectra but does contribute to the broadening of the spectra, while toroidal flow contributes to both. It is shown that neglecting the radial velocity for vR = 20km/s leads to an error in the ion temperature inversion of 20%. Results from MRX discharges are shown, and the impact of radial velocity on ion temperature inversions is discussed.

Accretion properties of MAXI J1813-095 during its failed outburst in 2018

We present the results obtained from detailed timing and spectral studies of a black hole candidate MAXI J1813–095 using Swift, NICER, and NuSTAR observations during its 2018 outburst. The timing behavior of the source is mainly studied by examining NICER light curves in the 0.5–10 keV range. We did not find any signature of quasi-periodic oscillations in the power density spectra of the source. We carry out spectral analysis with a combined disk blackbody & power law model, and physical two-component advective flow (TCAF) model. From the combined disk blackbody & power-law model, we extracted thermal and non-thermal fluxes, photon index and inner disk temperature. We also find evidence for weak reflection in the spectra. We have tested the physical TCAF model on a broadband spectrum from NuSTAR and Swift/XRT. The parameters like mass accretion rates, the size of Compton clouds and the shock strength are extracted. Our result affirms that the source remained in the hard state during the entire outburst which indicates a ‘failed’ outburst. We estimate the mass of the black hole as 7.4 ± 1.5 M ⊙ from the spectral study with the TCAF model. We apply the LAOR model for the Fe Kα line emission. From this, the spin parameter of the black hole is ascertained as a* > 0.76$ The inclination angle of the system is estimated to be in the range of 28° – 45° from the reflection model. We find the source distance to be ∼ 6 kpc.

Immiscible Rayleigh-Taylor turbulence using mesoscopic lattice Boltzmann algorithms

We study turbulence induced by the Rayleigh-Taylor (RT) instability for 2D immiscible two-component flows by using a multicomponent lattice Boltzmann method. We compare our results with the extension to the 2D case of the phenomenological theory for immiscible 3D RT studied by Chertkov and collaborators. In the immiscible case, the enstrophy shows a tendency to grow as $\ensuremath{\propto}{t}^{3/2}$, with the highest vorticity values concentrated close to the interface. We also investigate the typical drop size evolution and the behavior of the total length of the interface in the emulsion-like state, showing the existence of a power law behavior compatible with our phenomenological predictions.

Discontinuous-Galerkin finite-element method for approximating a model of non-equilibrium liquid chromatography considering Bi-Langmuir isotherm

In this paper, a discontinuous-Galerkin finite-element method (DG-FEM) is applied for the numerical solution of multi-component, non-equilibrium, lump kinetic model of liquid chromatography under nonlinear conditions. The model is analyzed for standard Bi-Langmuir type adsorption isotherms using Danckwert boundary conditions. Packed bed processes of liquid chromatography are modeled as convection-diffusion partial differential equations (PDE). In these models, the diffusion term is strongly dominated by the convection term. Therefore simulation of packed bed chromatographic processes requires specialized numerical techniques. In this study, the (DG-FEM) is utilized for the space discretization and the resulting semi-discrete system of ordinary differential equations is solved numerically by using a total variation bounded (TVB) Runge–Kutta method. This technique resolves sharp discontinuities and achieves a high order accuracy. To inspect the impact of different parameters, the results of the proposed method are authenticated against the high-resolution finite-volume scheme (HR-FVS). These numerical results include a single-solute flow, two-component mixture flow, and three-component mixture flow. The developed numerical results could be helpful in optimal predictive control, systematic monitoring and efficient operation of chromatographic processes.

Сравнение трех моделей течения и перемешивания модельных рабочих тел в смесительном элементе ЖРДМТ тягой 10…15 Н, основанных на решении осредненных по Рейнольдсу уравнений Навье — Стокса

The paper analyses the possibilities of using the ANSYS CFX hydrocode to simulate the flow and mixing of working bodies in the mixer and combustion chamber of a low-thrust liquid propellant rocket engine in the thrust range of 10 to 15 N. We built our models around solving Reynolds-averaged Navier — Stokes equations stated for three types of multiphase multicomponent incompressible fluid flow: a two-phase two-component two-velocity flow model; a two-phase two-component single-velocity flow model; a three-phase three-velocity flow model. We consider the advantages and disadvantages of each model. We compare our simulation results to the results of measurements conducted during hydraulic testing of mixers.

Bayesian experimental design for CO2 sequestration with leakage risk assessment

PurposeThe author examine the sequestration of CO2 in abandoned geological formations where leakages are permitted up to only a certain threshold to meet the international CO2 emissions standards. Technically, the author address a Bayesian experimental design problem to optimally mitigate uncertainties and to perform risk assessment on a CO2 sequestration model, where the parameters to be inferred are random subsurface properties while the quantity of interest is desired to be kept within safety margins.Design/methodology/approachThe author start with a probabilistic formulation of learning the leak-age rate, and the author later relax it to a Bayesian experimental design of learning the formations geo-physical properties. The injection rate is the design parameter, and the learned properties are used to estimate the leakage rate by means of a nonlinear operator. The forward model governs a two-phase two-component flow in a porous medium with no solubility of CO2 in water. The Laplace approximation is combined with Monte Carlo sampling to estimate the expectation of the Kullback–Leibler divergence that stands for the objective function.FindingsDifferent scenarios, of confining CO2 while measuring the risk of harmful leakages, are analyzed numerically. The efficiency of the inversion of the CO2 leakage rate improves with the injection rate as great improvements, in terms of the accuracy of the estimation of the formation properties, are noticed. However, this study shows that those results do not imply in any way that the learned value of the CO2 leakage should exhibit the same behavior. Also this study enhances the implementation of CO2 sequestrations by extending the duration given by the reservoir capacity, controlling the injection while the emissions remain in agreement with the international standards.Originality/valueUncertainty quantification of the reservoir properties is addressed. Nonlinear goal-oriented inverse problem, for the estimation of the leakage rate, is known to be very challenging. This study presents a relaxation of the probabilistic design of learning the leakage rate to the Bayesian experimental design of learning the reservoir geophysical properties.

Coefficient of local loss of mechanical energy of the flow for a ­mixture of charge materials

Purpose. To determine the dependence of the coefficient of local losses of mechanical energy of flow of a two-component mixture of charge material on its depth, content of components, and average equivalent diameter of particles in the case of their free-dispersed motion. Methodology. The value of the coefficient of local losses of mechanical energy was determined by the value of the hydraulic resistance of the fluid during its movement in open channels and pipes. In this paper, methods were used of comparative analysis, mathematical modeling and forecasting of dynamic processes in the flow of granular material. Findings. Based on the results of theoretical studies, a mathematical model was obtained, the use of which allows calculating the coefficient of local losses of mechanical energy for the flow of a two-component mixture of charge materials with agglomerate particle sizes from 15 to 50 mm, pellets from 6 to 12 mm, coke from 10 to 60 mm. The developed model with satisfactory accuracy makes it possible to evaluate the movement of the charge from the indicated materials along the paths of the charging devices of blast furnaces at a speed in the range from 1.5 to 20 m/s and to determine the trajectories of the mixture of charge materials on the top with an accuracy of 0.2 m. It is noted that the calculation of the above coefficient by the known techniques is not accurate enough, which is associated with the uncertainty in the choice of a single average equivalent diameter of the particles of the two-component charge. Comparative analysis of the developed model with the known models and experimental data indicates that the accuracy of calculating the dynamic parameters of a two-component flow of charge materials using the developed model increases by 510% in comparison with calculations using the previously known models. Originality. For the first time, regularities of changes in the coefficient of internal mechanical losses of a two-component flow of charge materials from its depth, content of components, average equivalent particle diameters when moving along the paths of charging devices of blast furnaces have been established. Practical value. Mathematical dependencies have been developed and can be used to determine the technological parameters of the charge of a modern blast furnace with different characteristics of the granulometry of the charge and the ratios of its components. This will increase the accuracy of predicting the course of the process under consideration, the degree of automation of the control systems for the technological process of the charge supply of blast furnaces, will make it possible to use expensive charge materials more efficiently, reduce energy consumption and reduce the harmful impact on the environment.

Study of heat transfer during cooling of highly loaded structural elements with a two-component heat carrier flow

One of the promising directions for the development of energy in the 21st century is thermonuclear energy. To implement this method of generating energy, experimental thermonuclear reactors have been operating for decades, the largest of which is currently being built in Cadarache (France). At the moment, one of the unsolved problems of such reactors is the creation of systems that provide reliable heat removal of heat fluxes from intracameral objects, such as a limiter, blanket, and divertor. In addition to high energy density, these objects have quite significant dimensions. Today, cooling of such objects is carried out mainly by water under pressure. This paper considers the possibility of using a dispersed two-component coolant flow as an alternative method of cooling such objects. A description is given of an experimental bench simulating uniform heating along the perimeter of the test section and it’s main systems. The paper presents the design of a spray device for forming a two-component dispersed coolant flow with its technical characteristics and a working area for conducting research. Experimental data were obtained on the temperature of the wall of the working area at various operating parameters of the coolant and power input.

Some results of the study of heat transfer during the cooling of the high-temperature surface of the working section by the dispersed flow of the coolant

In this paper investigates the heat exchange of the high-temperature surface of the working area during cooling by a dispersed two-component flow. A brief description of the experimental stand, the working section of the spraying device for creating a dispersed flow is given. The results of experimental modeling of the cooling of the working section at different regime parameters of the flow and supplied electric powers are presented. Data on the distribution of the wall temperature along the length of the heated working section are obtained. The thermal flux density on the side surface of the working area was estimated based on the readings of thermocouples in the work area. The operating parameters of the coolant at which the sample is cooled most effectively are determined.

Characteristics and linear stability analysis of RELAP5 two-fluid model for two-component, two-phase flow

The scope of this work comprises the study of the mathematical nature of the RELAP5 two-fluid model (TFM) for two-component (water and non-condensable gas (helium)) and two phases (liquid and vapor) mixture flows, and to predict the accuracy of the model under these flow conditions. The method of characteristics is applied to check the non-hyperbolic nature of conservation equations of RELAP5 for some sample fluid conditions. The sample problem selected here is a small break in helium-water heat exchanger primary tubes (containing high pressure and high-temperature helium gas) into the secondary shell (water) side high-temperature gas-cooled reactor, that causes mixing of helium-steam and liquid water and results in two-component two-phase flow. This sample problem is selected to address the RELAP5 model behavior and its sensitive nature under multi-component two-phase analysis. Linear stability analysis is also performed to check the error growth rates for the sample fluid conditions.

Waves in Liquid Film Regimes of Adiabatic Two-Phase Flow in a Slit Microchannel

Two-phase and two-component flows in microchannels being very promising for applications in areas such as microfluidics, microelectronic cooling, and heat exchange systems, there is a need to study characteristics of these flows and new effects associated with microchannel flows. This work presents an experimental and theoretical study of waves in stratified and annular flow regimes for a flat slit microchannel 104 $$\mu$$ m high and 10 mm wide, with isopropanol used as a working liquid and nitrogen used as a gas. The lengths of waves appearing on the film on the lower wall of the microchannel were measured experimentally. Quantitative dependences of the wavelengths on the liquid and gas flow rates were obtained. A numerical calculation was performed using analysis of linear stability. The experimental data on the wavelengths were compared with the results of numerical calculations for wavelengths of maximum growth. Dependences of the averaged distances of transitions from 2D to 3D waves on the Reynolds numbers of the liquid and gas were obtained experimentally. Dependences of the maximum spatial rate of perturbation growth on the Reynolds numbers of the liquid and gas were found numerically and experimentally.

Direct fluid flow simulation at pore scale with regularized hydrodynamic equations

Laboratory analysis of rock samples (core material) is one of the main tools used in an analysis of oil and gas field development and methods to enhance oil recovery. A number of drawbacks are intrinsic to the laboratory techniques, among which we note the practical impossibility of carrying out parametric studies on one sample, the impossibility (and / or high cost) of taking into account reservoir conditions, and the impossibility of analyzing non-cemented rocks (sludge). With the development of computational capabilities and computed tomography methods, the “digital rock physics” technology, which consists in direct simulation of physical processes in a rock sample with resolved pore space geometry, is gaining popularity today. This technology complements the traditional laboratory studies and compensates for a number of their shortcomings. The presented work is devoted to the direct simulation of fluid flow within the scope of the digital rock physics. For simulation regularized (according to quasi-hydrodynamic technique) hydrodynamic equations are used. Both single-phase single-component flows and two-phase two-component flows, taking into account interfacial tension, are discussed. The results of simulations of fluid flows both in model domains and in domains corresponding to the pore space of real rocks are presented.

Effect of non-condensable gas on a collapsing cavitation bubble near solid wall investigated by multicomponent thermal MRT-LBM* *Project supported by the National Natural Science Foundation of China (Grant Nos. 11874140 and 11574072), the State Key Laboratory of Acoustics, Chinese Academy of Sciences (Grant No. SKLA201913), the National Key Research and Development Program of China (Grant No. 2016YFC0401600), the Primary Research

A multicomponent thermal multi-relaxation-time (MRT) lattice Boltzmann method (LBM) is presented to study collapsing cavitation bubble. The simulation results satisfy Laplace law and the adiabatic law, and are consistent with the numerical solution of the Rayleigh–Plesset equation. To study the effects of the non-condensable gas inside bubble on collapsing cavitation bubble, a numerical model of single spherical bubble near a solid wall is established. The temperature and pressure evolution of the two-component two-phase flow are well captured. In addition, the collapse process of the cavitation bubble is discussed elaborately by setting the volume fractions of the gas and vapor to be the only variables. The results show that the non-condensable gas in the bubble significantly affects the pressure field, temperature field evolution, collapse velocity, and profile of the bubble. The distinction of the pressure and temperature on the wall after the second collapse becomes more obvious as the non-condensable gas concentration increases.

AstroSat and MAXI view of the black hole binary 4U 1630−472 during 2016 and 2018 outbursts

ABSTRACT We present an in-depth spectral and timing analysis of the black hole binary 4U 1630−472 during 2016 and 2018 outbursts as observed by AstroSat and MAXI. The extensive coverage of the outbursts with MAXI is used to obtain the hardness intensity diagram (HID). The source follows a ‘c’-shaped profile in agreement with earlier findings. Based on the HIDs of previous outbursts, we attempt to track the evolution of the source during a ‘super’-outburst and ‘mini’-outbursts. We model the broad-band energy spectra (0.7–20.0 keV) of AstroSat observations of both outbursts using phenomenological and physical models. No Keplerian disc signature is observed at the beginning of 2016 outburst. However, the disc appears within a few hours after which it remains prominent with temperature (Tin) ∼ 1.3 keV and increase in photon index (Γ) from 1.8 to 2.0, whereas the source was at a disc dominant state throughout the AstroSat campaign of 2018 outburst. Based on the HIDs and spectral properties, we classify the outbursts into three different states – the ‘canonical’ hard and soft states along with an intermediate state. Evolution of rms along different states is seen although no quasi-periodic oscillations are detected. We fit the observed spectra using a dynamical accretion model and estimate the accretion parameters. Mass of the black hole is estimated using inner disc radius, bolometric luminosity, and two-component flow model to be 3–9 M⊙. Finally, we discuss the possible implications of our findings.

Accretion Flow Evolution of a New Black Hole Candidate MAXI J1348–630 during the 2019 Outburst

Abstract Galactic black hole (BH) candidate MAXI J1348–630 was recently discovered by MAXI and Swift/BAT satellites during its first outburst in 2019 January, which continued for ∼4 months. We study the spectral and timing properties of the source in detail. The combined 1–150 keV Swift/XRT, Swift/BAT, and MAXI/GSC spectra are investigated with the two-component advective flow (TCAF) solution. Physical flow parameters of TCAF, such as the Keplerian disk accretion rate, the sub-Keplerian halo accretion rate, the shock location, and the shock compression ratio, are estimated from our spectral fits. Based on the variation of flux in soft and hard X-ray ranges, the hardness ratio, TCAF model fitted accretion rates, and the accretion rate ratio, we show how the source evolved through four spectral states, viz., hard, hard-intermediate, soft-intermediate, and soft, in rising and declining states. Low-frequency quasi-periodic oscillations are observed in two observations during the rising phase of the outburst. From the spectral analysis, we estimate the mass of the BH to be M ⊙. We also find that the viscous timescale in this outburst is ∼3.5 days. The distance of the source is also estimated as 5–10 kpc from state transition luminosity.

Transition from non-swirling to swirling axisymmetric turbulence

Strictly axisymmetric turbulence, i.e., turbulence governed by the Navier-Stokes equations modified such that the flow is invariant in the azimuthal direction, is a system intermediate between two-and three-dimensional turbulence. We investigate statistically steady states of this system by direct numerical simulation using a forcing protocol, which allows the injected energy in the toroidal and in the poloidal directions to be tuned independently. A sharp transition between a two-dimensional two-component (2D2C, non-swirling) flow and a two-dimensional three-component (2D3C, swirling) flow is observed. We derive a statistical model which reproduces this transition.