Small Inclination Angle Research Articles

Heat transfer characteristics of a flat plate pulsating heat pipe with microstructures for unidirectional thermal-to-mechanical energy conversion

The phase change of a liquid into vapor results in a sharp volume expansion, generating a powerful driving force, which is fundamental for the operation of pulsating heat pipes (PHPs). However, the performance of PHPs is hindered by instability arising from the lack of directional control over the expansion process. In this work, we propose a PHP incorporating thermal-to-mechanical energy conversion (TMC) microstructures, which direct the TMC by controlling the expansion in desired directions, thereby more efficiently utilizing the driving force. Two designs for enhancement of TMC, i.e., one featuring a vapor actuator microstructure (VA-PHP) and another with diameter-variant channels (DVC-PHP), were fabricated and experimentally investigated under low inclination angles and horizontal orientations (0°, 1°, 5°, and 9°). The experimental results indicated that the incorporation of the TMC microstructures into the PHPs facilitated more efficient startup, enhanced unidirectional circulation, and reduced the dependence on the inclination angle. Notably, while the conventional PHP failed to operate at small inclination angles, the VA-PHP achieved stable operation at 1°, and the DVC-PHP further maintained stable operation even at 0°. The robust performance of the proposed PHPs at low inclination angles demonstrates the potential of TMC microstructures to overcome orientation-dependent limitations, thereby delivering a practical solution for improving the effectiveness of PHPs.

Accurate Standard Siren Cosmology with Joint Gravitational-Wave and γ-Ray Burst Observations.

Joint gravitational-wave and γ-ray burst (GRB) observations are among the best prospects for standard siren cosmology. However, the strong selection effect for the coincident GRB detection, which is possible only for sources with small inclination angles, induces a systematic uncertainty that is currently not accounted for. We show that this severe source of bias can be removed by inferring the apriori unknown electromagnetic detection probability directly from multimessenger data. This leads at the same time to an unbiased measurement of the Hubble constant, to constrain the properties of GRB emission, and to accurately measure the viewing angle of each source. Our inference scheme is applicable to real data already in the small-statistics regime, a scenario that might become reality in the near future. Additionally, we introduce a novel likelihood approximant for gravitational-wave events which treats the dependence on distance and inclination as exact.

Effect of small inclination angle on heat transfer performance of Ω-grooved bending heat pipe

Grooved bending heat pipe may operate at small inclination angle caused by practical installation errors. Previous researches mainly focused on large inclination angles of straight heat pipes, but fewer experiments were conducted at small inclination angle of bending heat pipe where liquid accumulation and gravity effect on liquid–vapor transport varies along the pipe. This paper experimentally studied the effect of small inclination angle (±3°) on heat transfer of aluminum-ammonia Ω-grooved bending heat pipe with total length of 650 mm, vapor chamber diameter of 4 mm and grooved wick diameter of 1.24 mm. The results showed that small inclination angle significantly affect the heat transfer performance of bending heat pipe with heat transfer limit changed by 9 times from 20 W to 180 W and thermal resistance changed by 8 times from 0.04 K/W to 0.32 K/W. Effect of negative and positive angles in bending heat pipe is complex than that in straight heat pipe. Positive condensation end inclination enhances heat transfer due to gravity-driven liquid reflux. Negative condensation end inclination inhibits heat transfer due to anti-gravity reflux and liquid accumulation suppressing gas condensation. Positive evaporation end inclination weakens heat transfer due to anti-gravity reflux. Negative evaporation end inclination also weakens heat transfer due to thick liquid film, increasing thermal resistance and potentially blocking vapor channels. Attributed to coupling effect of liquid accumulation at bending section and capillary force dominant at tiny incline, maximum heat transfer limit of 180 W is achieved at both end inclination of −0.5°.

Modified method of round Gaussian rings. Application to the two-planetary problem

A scheme of the modified method of round Gaussian rings, designed to study the secular evolution of orbits in systems consisting of a central star and two planets, is presented. The reason for the secular evolution of the nodes and inclinations of the orbits of the planets is their mutual gravitational attraction. The orbits of the planets are modeled by homogeneous round Gaussian rings, to which the masses, sizes and angles of inclination of the orbits, as well as orbital angular momenta of the planets, are transferred. The method takes into account the fact that, in general, the ascending nodes of the orbits may not coincide. The mutual gravitational energy of the rings 𝑊𝑚𝑢𝑡 is represented as a series in the quadratic approximation in powers of small inclination angles. Using this function 𝑊𝑚𝑢𝑡, a closed system of four differential equations describing the secular evolution of the planets’ orbits is composed. The solution to the equations is obtained in finite analytic form, which simplifies the interpretation of the investigated planetary motions. The method was tested on the example of the Sun-Jupiter-Saturn system; for it, in particular, the difference in the longitudes of the nodes of the orbits of Jupiter and Saturn was calculated as a function of time. New approach is also used to study the precession of nodes in the exoplanetary system K2-36; graphs of all unknown quantities are obtained. It has been established that in the course of evolution the mutual inclination angle of the orbits remains constant, and the librations of the orbits in the inclination angle and in the motion of the nodes occur synchronously.

О СПИРАЛЬНОСТИ СКЛОНОВЫХ ТЕЧЕНИЙ

A generalization of the Prandtl’s stationary model of slope flows taking into account the influence of Coriolis accelerations is considered. The helicity of stationary slope flows is calculated analytically. The calculations show that the helicity of such flows, in principle, can be very significant even at very small angles of the lower boundary inclination. This result is especially enhanced for weak background stratifications.

Modeling Ocean Swell and Overtopping Waves: Understanding Wave Shoaling with Varying Seafloor Topographies

One risk posed by hurricanes and typhoons is local inundation as ocean swell and storm surge bring a tremendous amount of energy and water flux to the shore. Numerical wave tanks are developed to understand the dynamics computationally. The three-dimensional equations of motion are solved by the software ‘Open Field Operation And Manipulation’ v2206. The ‘Large Eddy Simulation’ scheme is adopted as the turbulence model. A fifth-order Stokes wave is taken as the inlet condition. Breaking, ‘run-up’, and overtopping waves are studied for concave, convex, and straight-line seafloors for a fixed ocean depth. For small angles of inclination (<10°), a convex seafloor displays wave breaking sooner than a straight-line one and thus actually delivers a smaller volume flux to the shore. Physically, a convex floor exhibits a greater rate of depth reduction (on first encounter with the sloping seafloor) than a straight-line one. Long waves with a speed proportional to the square root of the depth thus experience a larger deceleration. Nonlinear (or ‘piling up’) effects occur earlier than in the straight-line case. All these scenarios and reasoning are reversed for a concave seafloor. For large angles of inclination (>30°), impingement, reflection, and deflection are the relevant processes. Empirical dependence for the setup and swash values for a convex seafloor is established. The reflection coefficient for waves reflected from the seafloor is explored through Fourier analysis, and a set of empirical formulas is developed for various seafloor topographies. Understanding these dynamical factors will help facilitate the more efficient designing and construction of coastal defense mechanisms against severe weather.

Numerical analysis of thermal mechanism in downward flame spread over inverted surfaces of discrete inclined solid fuels

This investigation is propelled by engineering challenges associated with heat transfer during fire incidents on inclined surfaces, such as those observed in pitched roof fires, which hold significant implications for fire safety engineering and energy conservation. Drawing inspiration from real-world fire dynamics, this study delves into the downward flame spread over inverted solid fuel surfaces across a range of inclination angles, bridging the gap between theory and practice. Detailed analysis of temperature distribution, flame characteristics, and gas-phase reactions reveals critical insights into the complex interplay governing heat behavior under these conditions. The observed reduction in flame thickness and standoff distance with increasing inclination underscores the influence of buoyancy-induced plumes. This work developed a dimensionless formula that accounts for both buoyancy-induced plumes and diffusion rates perpendicular to the fuel, successfully capturing the variation in flame thickness with inclination angles. Furthermore, our findings show that the average flame spread rate escalates with higher inclination angles, attributed to enhanced gas-phase reactions near the flame front that lead to intensified heat transfer and a subsequent increase in temperature within the solid phase. The study also uncovers a competitive mechanism between flame “jumps” and heat transfer to the unburned zone, causing an initial increase and then a decrease in flame spread rates with increasing discrete gap size at larger inclination angles. Conversely, at smaller inclination angles, flame progression halts as the discrete gap size increases, due to inadequate heat transfer to the adjacent discrete fuel, resulting in the cessation of flame spread. This study not only advances our understanding of the thermal processes underpinning flame spread in inclined configurations but also offers crucial insights for developing more effective fire protection strategies and thermal protection systems in engineering applications.

Eccentricity and inclination of massive planets inside low-density cavities: results of 3D simulations

ABSTRACT We study the evolution of eccentricity and inclination of massive planets in low-density cavities of protoplanetary discs using three-dimensional (3D) simulations. When the planet’s orbit is aligned with the equatorial plane of the disc, the eccentricity increases to high values of 0.7–0.9 due to the resonant interaction with the inner parts of the disc. For planets on inclined orbits, the eccentricity increases due to the Kozai–Lidov mechanism, where the disc acts as an external massive body, which perturbs the planet’s orbit. At small inclination angles, ${\lesssim}30^\circ$, the resonant interaction with the inner disc strongly contributes to the eccentricity growth, while at larger angles, eccentricity growth is mainly due to the Kozai–Lidov mechanism. We conclude that planets inside low-density cavities tend to acquire high eccentricity if favourable conditions give sufficient time for growth. The final value of the planet’s eccentricity after the disc dispersal depends on the planet’s mass and the properties of the cavity and protoplanetary disc.

Instability of a weakly viscoelastic film flow on an oscillating inclined plane

The long- and finite-wavelength instabilities of weakly viscoelastic film on an oscillating inclined plane are investigated. By using the Chebyshev series solution with the Floquet theory, the combined effects of viscoelasticity and forcing amplitude on instability are described when the inclined plane oscillates in streamwise and wall-normal directions. For long-wavelength instability, the solution to the eigenvalue problem is obtained analytically by the asymptotic expansion method. Results show that the Floquet exponent is independent of the wall-normal oscillation amplitude. The effects of inclined angle, gravity and surface tension on the stability of viscoelastic liquid film are also discussed. For finite-wavelength instability, numerical results corresponding to the wall-normal oscillation disclose that with the increase of viscoelasticity, the unstable gravitational boundary moves to a higher wavenumber, and the critical amplitudes of subharmonic and harmonic instabilities are reduced. The neutral curve of gravity instability for streamwise oscillatory flow is divided into two parts, and a stable bandwidth is formed for a large value of the viscoelastic parameter. Besides, a new oscillatory mode is identified at small angles of inclination, which will be enhanced if the effect of viscoelasticity is incorporated.

Investigation of the Shear Mechanism at Sand-Concrete Interface under the Influence of the Concave Groove Angle of the Contact Surface

A “random-type” sand–concrete interface shear test was developed based on the sand cone method, with a focus on the most commonly encountered triangular contact surface morphology. A “regular-type” triangular interface, matched in roughness to the “random-type”, was meticulously designed. This “regular-type” interface features five distinct triangular groove inclinations: 18°, 33°, 50°, 70°, and 90°. A series of sand–concrete interface direct shear tests were conducted under consistent compaction conditions to investigate the impact of varying compaction densities and triangular groove inclinations on the shear strength at the interface. Particle flow simulations were utilized to examine the morphology of the shear band and the characteristics of particle migration influenced by the triangular contact surface. This analysis is aimed at elucidating the influence of the inclination of the triangular groove on the shear failure mechanism at the sand–concrete interface. The findings indicate that: (1) The morphology of the interface significantly impacts the shear strength of the sand–concrete interface, while the shape of the stress-displacement curve experiences minimal alteration. (2) At smaller inclination angles, particle contact forces are arranged in a wave-like configuration around the sawtooth tip, resulting in a non-uniform stress distribution along the sawtooth slope. However, as the inclination angle grows, the stress concentration at the sawtooth tip diminishes, and the stress distribution across the sawtooth slope becomes more consistent. (3) Particle migration is significantly influenced by the sawtooth’s inclination angle. At lower angles, particles climb the structure’s tip through sliding and rolling. As the angle increases, particle motion shifts to shear, accompanied by a transition in friction from surface friction to internal shear friction. This leads to the formation of a wider shear band and an increase in shear strength.

Improving the quality of mustard seeds during pre-sowing preparation

Improving the quality of mustard seeds during pre-sowing preparation

Numerical parametric study of turbulent counterflowing jets

In order to study the sensitivity to flow and geometrical conditions, a turbulent round jet in counterflow is numerically investigated for different Reynolds numbers and slight inclination angles at various jet-to-counterflow velocity ratios. Numerical simulations are executed with the second order Reynolds Stress Model (RSM) using the CFD code Ansys Fluent. It is found that the linearity between the penetration length and the velocity ratio remains valid as long as the jet-to-counterflow momentum flux ratio is up to 0.06. It is shown that no influence of the Reynolds number of either the main flow (Re0) or the jet flow (Rej) is found as long as Re0 > 10,000 and Rej > 3000, respectively. Also, even a small inclination angle seems to result in an asymmetric flow field with appreciable reduction in jet penetration length.

Synchro-curvature description of γ-ray light curves and spectra of pulsars: global properties

Abstract This work presents a methodological approach to generate realistic γ-ray light curves of pulsars, resembling reasonably well the observational ones observed by the Fermi-Large Area Telescope instrument, fitting at the same time their high-energy spectra. The theoretical light curves are obtained from a spectral and geometrical model of the synchro-curvature emission. Despite our model relies on a few effective physical parameters, the synthetic light curves present the same main features observed in the observational γ-ray light curve zoo, such as the different shapes, variety in the number of peaks, and a diversity of peak widths. The morphological features of the light curves allows us to statistically compare the observed properties. In particular, we find that the proportion on the number of peaks found in our synthetic light curves is in agreement with the observational one provided by the third Fermi-LAT pulsar catalog. We also found that the detection probability due to beaming is much higher for orthogonal rotators (approaching 100%) than for small inclination angles (less than 20 %). The small variation on the synthetic skymaps generated for different pulsars indicates that the geometry dominates over timing and spectral properties in shaping the gamma-ray light curves. This means that geometrical parameters like the inclination angle can be in principle constrained by gamma-ray data alone independently on the specific properties of a pulsar. At the same time, we find that γ-ray spectra seen by different observers can slightly differ, opening the door to constraining the viewing angle of a particular pulsar.

A new pressure control scheme on steam‐assisted gravity drainage for heavy oil production

AbstractAs one the most important recovery mechanisms of steam‐assisted gravity drainage (SAGD), gravity drainage is largely dependent on the inclination angle of the steam chamber edge. The existence of solution‐gas causes an ellipsoid‐shaped chamber that has small inclination angle at the bottom, which leads to inefficient gravity drainage and slows down oil production. To address this problem, this study proposes a new scheme, variable‐pressure SAGD (VP‐SAGD). It is basically a SAGD process, at certain stages of which pressure surge is induced by controlling the operating conditions so that the shape of steam chamber can be altered. This leads to a larger slip angle in the steam chamber at the bottom and more efficient heat transport between hot steam and crude oil. Results show that VP‐SAGD is able to increase oil recovery by up to 20% and decrease cumulative steam–oil ratio (cSOR) by up to 7%. Its special oil extraction mechanisms include swabbing effect, enlarged inclination angle of steam chamber boundary at the bottom, and enhanced heat transfer. Particularly, the inclination angle is increased by up to 40%. In addition, a lower producer bottom‐hole pressure (BHP) during pressure drawdown leads to a better production incremental in later stages. The optimal timing for pressure surge is the middle stage of steam chamber growth. The lower the producer BHP decrease, the better the yield increase. Moreover, The VP‐SAGD strategy works better in heavy oil reservoirs with a permeability of k = 0.5–10 Darcy or solution gas content of greater than 2%.

Enhancing the lubrication performance of the oil films in piston/cylinder pairs by textures

The long-term wear of the piston/cylinder pair is the main failure reason for axial piston pumps. In this paper, the dynamics of textured films to enhance the lubrication performance of piston/cylinder pairs is investigated systematically. The oil film is divided into three regions: the head region, the texture region, and the tail region. The Reynolds equation is used to predict the dynamics, which includes the carrying capacity and the friction. Influences of the texture geometries and the working conditions are presented in sequence. The results show that the texture enhances the lubrication performance by the collective effect. A shorter head length and a larger area ratio always benefit the lubrication performance, while increasing the texture region length does not always lead to positive effects, and the cell length is found to have negligible influences. The texture effect is found to be enhanced with larger shearing velocities and to be restrained with higher inlet pressures. It is also shown that the texture is effective for small inclination angles. Furthermore, a one-dimensional model is performed to unravel the mathematical mechanism, and an explicit expression is given for the texture region length.

Study of the Stability of the Mathematical Model of the Bound Pendulums Motion

The article presents a study of the dynamics of an oscillatory dissipative system of two elastically coupled pendulums in a magnetic field. Nonlinear normal modes of oscillation of a pendulum system have been studied, taking into account the resistance to the medium and the damping moment created by the elastic element. A system with two degrees of freedom is considered, in which the masses of the pendulums differ significantly, which leads to the possibility of localization of oscillations. In the following study, the mass ratio is chosen as a small parameter. For approximate calculations of magnetic forces, the Padé approximation is used, which best satisfies the experimental data. This approximation provides a very accurate description of the magnetic excitation. The presence of external influences in the form of magnetic forces and various types of loads that exist in many engineering systems significantly complicates the analysis of vibration modes of nonlinear systems. Studies have been carried out of nonlinear normal modes of oscillations in this system, one of the modes being a coupled mode, and the second being a localized mode. The oscillation modes are constructed using the multiscale method. Both regular and complex behavior when changing system parameters have been studied. The influence of these parameters was studied for small and large initial angles of inclination of the pendulum. Analytical solution based on the fourth order Runge-Kutta method compared with numerical simulation results. The initial conditions for calculating the vibration modes were determined by the analytical solution. Numerical modeling, consisting of constructing phase diagrams, trajectories in configuration space, and amplitude-frequency characteristics, allows one to evaluate the dynamics of a system, which can be either regular or complex. The stability of oscillation modes was studied using numerical analysis tests, which are implementations of the Lyapunov stability criterion. In this case, the stability of the oscillation modes is determined by assessing the orthogonal deviations of the corresponding trajectories of the oscillation modes in the configuration space.

Design and development of a continuous water quality monitoring buoy for health monitoring of river Ganga

Real-time monitoring of water quality in the river Ganga and other Indian rivers is crucial to determining its suitability for drinking and other usages across the seasons and round the clock. For this, a structurally strong and hydrostatically stable floating observation center is required to house all the sensors and related equipment. This paper explains the design process for such a buoy platform that can house an array of water quality sensors powered by hybrid energy harvesting systems. Sensors are connected to a wireless sensor network (WSN) system that transfers data to a web-based platform, where we can monitor and analyze our data for the purpose of hazard prediction. Computational analysis has been carried out for the observatory body to ascertain its structural integrity and hydrostatic stability at small and large angles of inclination. The buoy design is based on various requirements specific to Indian rivers at different locations from the mid-course to the confluence. It is important that the system be modular and portable for use in a constantly changing river/water environment. A full-scale functional prototype has been developed, and field testing has been carried out to bring out the efficacy of the proposed system. Also, the WSN system collected real-time water quality data that have been validated with laboratory-based experiments. The establishment of a network of low-cost river/water health monitoring system will further initiate the large-scale data collection and help create digital twins of the Indian rivers.

Numerical Analysis of Interbedded Anti-Dip Rock Slopes Based on Discrete Element Modeling: A Case Study

Varying geological conditions and different rock types lead to complex failure modes and instability of interbedded anti-dip rock slopes. To study the characteristics of failure evolution of interbedded anti-dip slopes, a two-dimensional particle flow code (PFC2D) based on the discrete element method (DEM) was utilized to establish an interbedded anti-dip rock slope numerical model for the Fushun West Open-pit Mine based on the true geological conditions and field investigations. The slope model with an irregular surface consists of interbedded mudstone and brown shale as two different rock layers, and a number of small-scale rock joints are randomly distributed in the rock layers. The influence of different inclination angles (20° and 70°) of the rock layer and slope angles (60° and 80°) on the stability of interbedded anti-dip rock slopes was considered. The evolution of the failure progress was monitored by the displacement field and force field. The simulation results showed that the rock joints in the rock stratum promoted crack initiation and increased the crack density but did not change its shear-slip failure mode. A large inclination angle of the rock layers and slope angle can lead to topping slip failure along the slip zone. However, shear-slip instability generally occurs in interbedded anti-dip rock slopes with small inclination angles of the rock layer and small slope angles. These results can contribute to a better understanding of the failure mechanism of interbedded anti-dip rock slopes under different geological conditions and provide a reference for disaster prevention.

Topical Issues of Forensic Research of Firearms with Oval-Screw Drilling of the Bore “Lancaster” and Its Traces on the Bullets

The article discusses the issues of developing the legal, scientific, and methodological foundations of the forensic investigation of firearms with oval-screw drilling of the Lancaster barrel bore. The author makes some proposals on how to bring the norms of the regulatory and technical regulations in the field of arms and ammunition trafficking in line with the modern concepts of rifled firearms. The mechanism of formation of traces of the barrel bore on the fired bullets is revealed. The author notes that the drilling of the Lancaster barrel bore determines the appearance of traces from its oval-screw profile in the form of two areas of abrasion along the small axis of the oval (traces of rifling lands) and two areas of less intense abrasion along the large axis of the oval (traces of rifling) on the bullets. The traces of the rifling lands and the traces of the rifling are fused with each other, and have a small angle of inclination (about 3° ).The dependence of the display of traces of the barrel bore with the Lancaster drill on the fired bullets on the design of the bullets of the cal cartridges has been established. .366 TCM, 9.6x53 Lancaster. When using cartridges with FMJ shell bullets and SP “KION” semi-shell bullets, the traces of the barrel bore are displayed sufficiently well, which, in general, makes it possible to identify the weapon. Firing cartridges with an all-metal bullet made of zinc alloy “ECO” dramatically reduces the display of traces of the barrel bore on the fired bullets and complicates the firearms identification. The author proposes to ban shooting cartridges with lead bullets with a polymer antifriction shell “DERI” in firearms with a Lancaster channel drill, since when firing, the traces of the barrel bore on the fired bullet are not displayed. This contradicts the legislator’s requirement for civilian models of firearms on mandatory formation of traces suitable for identifying weapons on fired bullets.

Failure and acoustic behavior of combinational flaws sandstone subjected to dynamic compression loads

This paper described work initiated with two objectives in mind. First was to explore the influence of strain rate effects on the strength law and deformation characteristics of plate sandstone with combined flaws. Second objective was to analyze the breaking response law and acoustic behavior of flawed sandstone under the influence of disturbance frequency and prefabricated dip angle. Thus, a self-developed physical simulation test system combined with the real-time AE monitoring system, were conducted a series of dynamic cyclic loading tests on the flawed plate sandstone. The results indicated that the dynamic frequencies and dip angles had significant effects on the deformation, strength and failure mode of specimens. Additionally, the degree of specimen failure decreased with the increase of disturbance frequency under the same inclination angle; along with, the most severe failure occurred when the inclination angle was 45 ° under the same disturbance frequency. The main failure mode of specimens was shear failure from the distribution of AF-RA. Meanwhile, for specimens with small angles (30 °, 45 °) and low frequencies (0.1, 0.3 Hz), the failure types were more complex (tensile-shear mixed failure). On the other hand, the AE characteristics mainly included three stages: I-initial cycle, II-stable development, and III-damage & failure. The CNT and ENE were greatly influenced by the disturbance frequency and inclination angle. In addition, the b-value decreased and fluctuates violently, and the strength of the samples was reduced as the loading frequency decreased. The specimens with smaller inclination angles had larger internal activity scales and more frequent damage activities with smaller b-value. Furthermore, Correlation dimension Dm was positively correlated with the change of disturbance frequency, and it was smaller when the inclination angle was 45 °.