Low Inclination Research Articles

Estimation of critical thickness of wax deposits during mechanical removal from high water cut oil well

The formation of wax deposits in oil wells is one of the most costly problems for oil production companies. The most common method of removing deposits is mechanical removal with a scraper. However, there is still no understanding of the critical conditions for wax removal. As part of this work, the authors consider the process of mechanical removal of wax from a high water cut oil well. The work carried out studies to assess the influence of the aqueous phase on the intensity of wax formation and simulated the thickness of wax deposits during the period of their removal under field conditions. It was found that the aqueous phase is actively included in the volume of deposits, increasing the rate of wax formation and their density. Based on the modeling, it was concluded that in wells with a low inclination, the critical thickness of wax deposits is 0.18 mm. The effect of water cut in production on the critical wax thickness has not been found, while with increasing well flow rate the critical thickness decreases. The work performed is extremely useful for understanding the process of mechanical removal of wax deposits from oil production wells producing water-cut oil.

Influence of Traveling Ionospheric Disturbances on the Caustic Structure of Radio Waves during Low Inclination Sounding of the Ionosphere

Influence of Traveling Ionospheric Disturbances on the Caustic Structure of Radio Waves during Low Inclination Sounding of the Ionosphere

Parameter study for critical heat flux under external reactor vessel cooling condition based on a mechanism model

External reactor vessel cooling has been adopted an important method to implement In Vessel Retention severe accident mitigation strategy for many advanced passive pressurized water reactors. Critical heat flux is one of the important criteria to evaluate the success or failure of this strategy. The uncertainty of engineering factors in practical design and operation conditions may make influence on critical heat flux more or less. In this paper, a parameter study for critical heat flux was carried out based on a new critical heat flux mechanism model. This mechanism model is developed based on the mechanism of liquid film dryout, and the predicted results of this model are in good agreement with the experimental results. Five important parameters, namely, coolant subcooling degree, geometry of lower head, system pressure, flow rate and heating power shape are analyzed based on this mechanism model. The results of parameter study show that the decrease of inlet coolant temperature and lower head radius are beneficial to the increase of critical heat flux. And the critical heat flux increases with the increase of system pressure. While the change of flow rate and heating power shape have little effect on critical heat flux. Under the condition of same circumference, the critical heat flux of spherical lower head is higher than that of elliptical lower head in the middle and low inclination angle region, while the trend is opposite in high inclination angle region, but not significant.

A relativistic outflow model of the X-ray polarization in Cyg X-1

ABSTRACT We propose that the polarization of the emission from the X-ray binary Cygnus X-1, measured using the Imaging X-ray Polarimetry Explorer, is imprinted by bulk Comptonization of coronal emission in a mildly relativistic wind or jet with a hollow-cone geometry. Models based on scattering in a static corona overlying a thin accretion disc have difficulty reproducing the relatively high-polarization degree (PD $\sim 4~{{\ \rm per\ cent}}$) concurrently with the low inclination (∼30°) of the binary orbit. We show that bulk outflow with a Lorentz factor ≳1.5 is adequate to reproduce the observed PD, with position angle parallel to the large-scale jet, provided that the scattering occurs in a conical sheath offset from the jet axis and our line of sight aligns roughly with the opening angle of the cone. Physically, this flow geometry could represent the entrainment of dense material near the base of an accelerating jet as it passes through the disc corona, or a slow (but still relativistic) sheath around a fast jet. If similar outflows are present in other X-ray binaries at higher inclination, we might expect to see still higher degrees of linear polarization ${\lesssim} 10~{{\ \rm per\ cent}}$ with an orientation perpendicular to the jet direction.

Forced-motion simulations of vortex-induced vibrations of wind turbine blades – a study of sensitivities

Abstract. Vortex-induced vibrations on wind turbine blades are a complex phenomenon not predictable by standard engineering models. For this reason, higher-fidelity computational fluid dynamics (CFD) methods are needed. However, the term CFD covers a broad range of fidelities, and this study investigates which choices have to be made when wanting to capture the vortex-induced vibration (VIV) phenomenon to a satisfying degree. The method studied is the so-called forced-motion (FM) approach, where the structural motion is imposed on the CFD blade surface through mode shape assumptions rather than fully coupled two-way fluid–structure interaction. In the study, two independent CFD solvers, EllipSys3D and Ansys CFX, are used and five different turbulence models of varying fidelities are tested. Varying flow scenarios are studied with low to high inclination angles, which determine the component of the flow in the spanwise direction. In all scenarios, the cross-sectional component of the flow is close to perpendicular to the chord of the blade. It is found that the low-inclination-angle and high-inclination-angle scenarios, despite having a difference equivalent to up to only a 30∘ azimuth, have quite different requirements of both grid resolution and turbulence models. For high inclination angles, where the flow has a large spanwise component from the tip towards the root, satisfying results are found from quite affordable grid sizes, and even with unsteady Reynolds-averaged Navier–Stokes (URANS) k–ω turbulence, the result is quite consistent with models resolving more of the turbulent scales. For low inclination, which has a high degree of natural vortex shedding, the picture is the opposite. Here, even for scale-resolving turbulence models, a much finer grid resolution is needed. This allows us to capture the many incoherent vortices, which have a large impact on the coherent vortices, which in turn inject power into the blade or extract power. It is found that a good consistency is seen using different variations of the higher-fidelity hybrid RANS–large eddy simulation (LES) turbulence models, like improved delayed detached eddy simulation (IDDES), stress-blended eddy simulation (SBES) and k–ω scale-adaptive simulation (SAS) models, which agree well for various flow conditions and imposed amplitudes. This study shows that extensive care and consideration are needed when modeling 3D VIVs using CFD, as the flow phenomena, and thereby solver requirements, rapidly change for different scenarios.

Oort cloud perturbations as a source of hyperbolic Earth impactors

The observation of interstellar objects 1I/’Oumuamua and 2I/Borisov suggests the existence of a larger population of smaller projectiles that impact our planet with unbound orbits. We analyze an asteroidal grazing meteor (FH1) recorded by the Finnish Fireball Network on October 23, 2022. FH1 displayed a likely hyperbolic orbit lying on the ecliptic plane with an estimated velocity excess of ∼0.7 kms−1 at impact. FH1 may either be an interstellar object, indicating a high-strength bias in this population, or an Oort cloud object, which would reinforce migration-based solar system models. Furthermore, under the calculated uncertainties, FH1 could potentially be associated with the passage of Scholz’s binary star system. Statistical evaluation of uncertainties in the CNEOS database and study of its hyperbolic fireballs reveals an anisotropic geocentric radiant distribution and low orbital inclinations, challenging the assumption of a randomly incoming interstellar population. Orbital integrations suggest that the event on March 9, 2017 (IM2) from CNEOS may have experienced gravitational perturbation during the Scholz fly-by, contingent upon velocity overestimation within the expected range. These findings suggest that apparent interstellar meteors may, in fact, be the result of accelerated meteoroid impacts caused by close encounters with massive objects within or passing through our solar system.

The orbital period of the recurrent nova V2487 Oph revealed

ABSTRACT We present the first reliable determination of the orbital period of the recurrent nova V2487 Oph (Nova Oph 1998). We derived a value of 0.753 ± 0.016 d (18.1 ± 0.4 h) from the radial velocity curve of the intense He ii λ4686 emission line as detected in time-series X-shooter spectra. The orbital period is significantly shorter than earlier claims, but it makes V2487 Oph one of the longest period cataclysmic variables known. The spectrum of V2487 Oph is prolific in broad Balmer absorptions that resemble a white dwarf spectrum. However, we show that they come from the accretion disc viewed at low inclination. Although highly speculative, the analysis of the radial velocity curves provides a binary mass ratio q ≈ 0.16 and a donor star mass M2 ≈ 0.21 M⊙, assuming the reported white dwarf mass M1 = 1.35 M⊙. A subgiant M-type star is tentatively suggested as the donor star. We were lucky to inadvertently take some of the spectra when V2487 Oph was in a flare state. During the flare, we detected high-velocity emission in the Balmer and He ii λ4686 lines exceeding −2000 km s−1 at close to orbital phase 0.4. Receding emission up to 1200 km s−1 at about phase 0.3 is also observed. The similarities with the magnetic cataclysmic variables may point to magnetic accretion on to the white dwarf during the repeating flares.

Detachment of a particle from the surface of a bubble colliding with a solid surface

The flotation of coarse mineral particles has attracted increased attentions for its advantages in early gangue rejection, reduced production of ultrafine particles, and significant energy savings during the grinding process. However, the detachment of coarse particles from the surface of bubbles could be problematic when the particle-bubble aggregates collide with the pulp-froth interface. This paper investigated the detachment of a particle from the surface of a bubble colliding with a solid surface. The rising characteristics of a particle-bubble aggregate was studied and it was found that the zigzag movement resulted in different orientations of the particle-bubble aggregates colliding with the surface. The orientation of the bubble in respective to the flat surface, characterized by the inclination angle between the bubble long axis and the flat surface, played a pronounced role in the particle detachment process. Particles were more likely to detach at low or high inclination angles. The rationale is that bubble oscillating at low inclination angle or particle sliding on the bubble surface at high inclination angle resulted in particle detachment. A neck was formed between a particle and a bubble during the detachment process, which is consistent with previous studies. The findings provide valuable insight into the phenomena of a particle detachment during the collision process of a bubble with a solid surface, which is essential to the modelling of coarse particle flotation processes and eventually contributes to the process optimization.

PSR J1953+1844 Probably Being the Descendant of an Ultracompact X-Ray Binary

PSR J1953+1844 (i.e., M71E) is a millisecond pulsar in a 53 minute binary orbit discovered by the Five-hundred-meter Aperture Spherical radio Telescope. The mass function from pulsar timing is 2.3 × 10−7 M ⊙. The possible redback origin of this system has been discussed by Pan et al. We discuss here an alternative evolution track for this binary system, namely that PSR J1953+1844 is a descendant of an ultracompact X-ray binary (UCXB), which has a hydrogen-poor donor accreting onto a neutron star (NS) with an orbital period of ≤1 hr. We noticed that some UCXB systems hold an accreting millisecond X-ray pulsar (AMXP) and a donor with a mass of about 0.01 M ⊙. M71E has a very similar orbit to those of AMXPs, indicating that it might be evolved from a UCXB similar to PSR J1653–0158. The companion star of M71E should be significantly bloated and it most probably has a carbon and oxygen composition, otherwise a low inclination angle of the orbit is required for a helium companion. The discovery of this M71E binary system may shed light on when and how an NS in a UCXB turns into a radio pulsar.

A disc wind model for blueshifts in quasar broad emission lines

ABSTRACT Blueshifts – or, more accurately, blue asymmetries – in broad emission lines such as C iv λ1550 are common in luminous quasars and correlate with fundamental properties such as Eddington ratio and broad absorption line (BAL) characteristics. However, the formation of these blueshifts is still not understood, and neither is their physical connection to the BAL phenomenon or accretion disc. In this work, we present Monte Carlo radiative transfer and photoionization simulations using parametrized biconical disc-wind models. We take advantage of the azimuthal symmetry of a quasar and show that we can reproduce C iv blueshifts provided that (i) the disc-mid-plane is optically thick out to radii beyond the line formation region, so that the receding wind bicone is obscured; and (ii) the system is viewed from relatively low (that is, more face-on) inclinations (≲40°). We show that C iv emission-line blueshifts and BALs can form in the same wind structure. The velocity profile of the wind has a significant impact on the location of the line formation region and the resulting line profile, suggesting that the shape of the emission lines can be used as a probe of wind-driving physics. While we are successful at producing blueshifts/blue asymmetries in outflows, we struggle to match the detailed shape or skew of the observed emission-line profiles. In addition, our models produce redshifted emission-line asymmetries for certain viewing angles. We discuss our work in the context of the C iv λ1550 emission blueshift versus equivalent-width space and explore the implications for quasar disc wind physics.

Image-Based Lunar Hazard Detection in Low Illumination Simulated Conditions via Vision Transformers.

Hazard detection is fundamental for a safe lunar landing. State-of-the-art autonomous lunar hazard detection relies on 2D image-based and 3D Lidar systems. The lunar south pole is challenging for vision-based methods. The low sun inclination and the terrain rich in topographic features create large areas in shadow, hiding the terrain features. The proposed method utilizes a vision transformer (ViT) model, which is a deep learning architecture based on the transformer blocks used in natural language processing, to solve this problem. Our goal is to train the ViT model to extract terrain features information from low-light RGB images. The results show good performances, especially at high altitudes, beating the UNet, one of the most popular convolutional neural networks, in every scenario.

Flares from stars crossing active galactic nucleus discs on low-inclination orbits

ABSTRACT The origin of the recently discovered new class of transients, X-ray quasi-periodic eruptions (QPEs), remains a puzzle. Due to their periodicity and association with active galactic nuclei (AGNs), it is natural to relate these eruptions to stars or compact objects in tight orbits around supermassive black holes (SMBHs). In this paper, we predict the properties of emission from bow shocks produced by stars crossing AGN discs, and compare them to the observed properties of QPEs. We find that when a star’s orbit is retrograde and has a low inclination (≲40°) with respect to the AGN disc and the star is massive (≳10 M⊙), the breakout emission from the bow shock can explain the observed duration (∼hours) and X-ray luminosity (∼few × 1042 erg s−1) of QPEs. This model can further explain various observed features of QPEs, such as their complex luminosity evolution, the gradual decline of luminosity of the flares over several years, the evolution of the hardness ratio, the modulation of the luminosity during quiescent phases, and the preference of the central SMBHs to have low masses.

Evaluation of the influence of surface structure on tribological properties of the solid–liquid interface: Analytical and experimental assessment

Nowadays, multiple strategies have been suggested to improve product efficiency on the basis of risk free techniques. Owing to the vast applications of the structured surface in many industrial sectors, considerable attention has been paid by many scholars to improve the surface performance aspects by studying their solid–liquid interface characterizations. In the current study, a new technique is introduced to manufacture a functional surface with water repellency feature through grinding process. Based on the solid–liquid interface evaluations of the modified surface, by structuring the surface, the contact angle increases from 35° (untreated surface) to 127° for structured surface. Therefore, the reinforced surface showed hydrophobicity with a 263% improvement for a scratch area fraction more than 75%. Formation of air pads trapped in the vacant space of the scratches was the main cause to enhance contact angle for structured surface. Since air molecules have very low inclination to chemical bonding with water molecules, the water droplet did not penetrate the scratches space and contact angle enhanced. A new analytical model for predicting the solid–liquid surface property was simultaneously developed by interaction of the kinematics of the grinding technique with single diamond and the basic wettability theory of the Cassie-Baxter. Therefore, the effect of all input parameters on the output results was studied in terms of achieving the best solid–liquid interaction performance through expanded model. The optimal values were calculated and the proposed structured surface was manufactured during the grinding process. According to the value of the static contact angle measured during experimental tests (127°) and its analytical value (123°), less than 4% error was observed between the results, which showed the high accuracy of the equation expanded on the present work.

Study on the Significance of Reduction to the Equator (RTE), Reduction to the Pole (RTP), and Pseudogravity in Magnetic Data Interpretation

Interpretation of geomagnetic anomaly data is challenging, due to the influence of the Earth's dipole magnetic field. In this study, we investigate the significance of employing methods to transform dipole anomalies into monopoles, aiming to enhance the interpretability of the data. Four methods were examined: Reduce to Pole (RTP), Reduce to Equator (RTE), and Pseudo-Gravity. The RTP method was implemented using general equations for RTP, Pseudo-inclination (PI), and Nonlinear thresholding (NTRTP). The computation programs for RTP and RTE were developed using the Matlab programming language. Synthetic models were constructed to investigate the effects of inclination values, object dimensions, and positions on the resulting magnetic anomaly response. The result shows that NTRTP methods give the best result with coefficient correlation >0.9. It can be used in every condition (low or high inclination). The implementation was conducted utilizing magnetic data in the Gunung Pandan geothermal area. The application of the reduced to the pole (RTP) technique on the field data successfully remove the dipole effects, and make interpretation process easier. Based on RTP map, the range of anomaly values spanning from -800 nT to 1000 nT. High anomalies were observed at the Gunung Pandan site, indicative of a probable intrusion of andesitic igneous rock.

Refining the Stellar Parameters of τ Ceti: a Pole-on Solar Analog

To accurately characterize the planets a star may be hosting, stellar parameters must first be well determined. τ Ceti is a nearby solar analog and often a target for exoplanet searches. Uncertainties in the observed rotational velocities have made constraining τ Ceti’s inclination difficult. For planet candidates from radial velocity (RV) observations, this leads to substantial uncertainties in the planetary masses, as only the minimum mass () can be constrained with RV. In this paper, we used new long-baseline optical interferometric data from the CHARA Array with the MIRC-X beam combiner and extreme precision spectroscopic data from the Lowell Discovery Telescope with EXPRES to improve constraints on the stellar parameters of τ Ceti. Additional archival data were obtained from a Tennessee State University Automatic Photometric Telescope and the Mount Wilson Observatory HK project. These new and archival data sets led to improved stellar parameter determinations, including a limb-darkened angular diameter of 2.019 ± 0.012 mas and rotation period of 46 ± 4 days. By combining parameters from our data sets, we obtained an estimate for the stellar inclination of 7° ± 7°. This nearly pole-on orientation has implications for the previously reported exoplanets. An analysis of the system dynamics suggests that the planetary architecture described by Feng et al. may not retain long-term stability for low orbital inclinations. Additionally, the inclination of τ Ceti reveals a misalignment between the inclinations of the stellar rotation axis and the previously measured debris disk rotation axis (i disk = 35° ± 10°).

Close encounters of the interstellar kind: exploring the capture of interstellar objects in near-Earth orbit

ABSTRACT Recent observations and detections of interstellar objects (ISOs) passing through the Solar system have sparked a wave of interest into these objects. Although rare, these ISOs can be captured into bound orbits around the Sun. In this study, we investigate the novel idea of capture of ISOs into near-Earth orbits and find that a steady population of ISOs exists among the current population of near-Earth objects (NEOs). Using numerical simulations, we find that the capture of ISOs into near-Earth orbits is dominated by Jupiter that is 104 times more efficient in capturing ISOs compared to Earth. Captured ISOs are more likely to be in orbits with high eccentricities and low inclinations. We also investigate the stability of captured ISOs and find that they are generally unstable and have an average survival lifetime of ∼1 Myr, consistent with lifetime of NEOs originating from outer asteroid belt, and are ejected from the Solar system due to interactions with other planets or the Sun. Our results have important implications for understanding the population of ISOs in the Solar system and possible future detection. We find that about one to a few 50–70 m sized captured ISOs among NEOs would be detectable by Vera Rubin Observatory over its lifetime. By detecting and studying captured ISOs, we can learn about the properties and origins of such objects, and the formation and evolution of exoplanetary systems and even our Solar system.

PSLV: The Versatile Workhorse Launch Vehicle of India

Polar Satellite Launch Vehicle (PSLV), the maiden operational launch vehicle of India, has emerged as a very reliable and versatile launch vehicle by successfully launching satellites, both Indian and foreign, into a variety of orbits around the earth. Though India has subsequently developed two succeeding generation of launch vehicles - GSLV Mark II and GSLV Mark III - of higher capability, complexity and efficiency, nevertheless they have not acquired the conspicuous attention of the country as well as the outside world as PSLV has, through its numerous multifarious achievements. Despite its uncommon design of alternating solid and liquid stages, the robustness of the four stage PSLV design has been repeatedly proved by its successes as well as the resilience of the vehicle to quickly recover from rare failures. Besides launching a record number of 104 satellites in a single mission, PSLV has many other achievements to its credit including the launch of satellites into polar Sun Synchronous, Geosynchronous Transfer and sub-Geosynchronous Transfer Orbits as well as Low Earth Orbits of moderate and very low inclinations. This paper discusses several important aspects of PSLV including its lineage, development, configuration and improvements as well as its heritage, past contribution and future prospects on the occasion of its recent success in launching 31 satellites from India and eight other countries into two different orbits on November 29, 2018.

K2 and TESS observations of symbiotic X-ray binaries: GX 1+4 and IGR J16194−2810

I analyze the K2 and TESS data taken in 2016, 2019, and 2021 of the symbiotic X-ray binaries GX 1+4 and IGR J16194−2810. GX 1+4 consists of a pulsar accreting from a red giant companion in a 1160-day orbit. Since 1984, the pulsar has shown a continuous spin-down rate of Ṗ = −0.1177(3) mHZ yr−1. I report the detection of the spin period at an average value of 180.426(1) seconds as observed with the K2 mission and confirm that the spin period continues to increase at a rate of ∼1.61×10−7 s s−1. The K2 and hard X-rays, as observed with Swift/BAT, varied in tandem, in agreement with proposals from other authors that the optical light arises from reprocessed X-ray emission. In the case of IGR J16194−2810, the X-ray and optical spectroscopy have been interpreted as arising from a neutron star accreting from an M2 III red giant companion. Its orbital period is unknown, though I report here the detection of a modulation with a period of 242.837 min and interpret it as the neutron star spin period. IGR J16194−2810 is thus the second symbiotic X-ray binary whose spin period has been detected in optical wavelengths. This period, however, was only detected during the TESS observations of Sector 12 in 2019. The non-detection of this modulation during the observations of Sector 39 in 2021 is perhaps related to a low inclination of the orbit.

Misaligned Jets from Sgr A* and the Origin of Fermi/eROSITA Bubbles

One of the leading explanations for the origin of Fermi Bubbles is past jet activity in the Galactic center supermassive black hole Sgr A*. The claimed jets are often assumed to be perpendicular to the Galactic plane. Motivated by the orientation of pc-scale nuclear stellar disk and gas streams, as well as a low inclination of the accretion disk around Sgr A* inferred by the Event Horizon Telescope, we perform hydrodynamical simulations of nuclear jets significantly tilted relative to the Galactic rotation axis. The observed axisymmetry and hemisymmetry (north–south symmetry) of Fermi/eROSITA bubbles (FEBs) due to quasi-steady jets in Sgr A* could be produced if the jet had a super-Eddington power (≳5 × 1044 erg s−1) for a short time (jet active period ≲6 kyr) for a reasonable jet opening angle (≲10°). Such powerful explosions are, however, incompatible with the observed O viii/O vii line ratio toward the bubbles, even after considering electron–proton temperature nonequilibrium. We argue that the only remaining options for producing FEBs are (i) a low-luminosity (≈1040.5−41 erg s−1) magnetically dominated jet or accretion wind from the Sgr A*, or (ii) a supernovae or tidal disruption event driven wind of a similar luminosity from the Galactic center.

Black hole photon rings beyond general relativity

We investigate whether photon ring observations in black hole imaging are able to distinguish between the Kerr black hole in general relativity and alternative black holes that deviate from Kerr. Certain aspects of photon rings have been argued to be robust observables in very-long-baseline interferometry black hole observations which carry imprints of the underlying spacetime. The photon ring shape, as well as its Lyapunov exponent (which encodes the narrowing of successive photon subrings), are detailed probes of the underlying geometry; measurements thereof have been argued to provide a strong null test of general relativity and the Kerr metric. However, a more complicated question is whether such observations of the photon ring properties can distinguish between Kerr and alternative black holes. We provide a first answer to this question by calculating photon rings of the Johannsen, Rasheed-Larsen, and Manko-Novikov black holes. We find that large deviations from Kerr and large observer inclinations are needed to obtain measurable differences in the photon ring shape. In other words, the Kerr photon ring shape appears to be the universal shape even for deviating black holes at low inclinations. On the other hand, the Lyapunov exponent shows more marked variations for deviations from the Kerr metric. Our analysis lays out the groundwork to determine deviations from the Kerr spacetime in photon rings that are potentially detectable by future observing missions.