Constant Velocity Research Articles

Algebraic expressions for convective solute transport in a homogeneous soil below a surface barrier

AbstractEngineered surface barriers are expected to be used to cover sites containing buried waste radionuclides after site closure. Understanding the transport of contaminants in the soil below a surface barrier is of importance in order to protect the underlying groundwater. The travel velocity of these contaminants is dependent on numerous factors, such as the thickness, properties, the pre‐barrier hydrologic condition of the vadose zone, and the initial depths and properties of the contaminants. Although solute transport can be modeled with numerical modeling using site‐specific data, by nature a numerical method does not reveal the relationship between inputs and outputs. This work develops algebraic expressions of the velocities of convective solute transport in the vadose zone below a surface barrier, time lag, solute safe depth, zero‐protection depth of a surface barrier, and solute travel time to the groundwater. This development shows that solute convection in the soil with a surface barrier consists of up to three stages: constant high velocity, decreasing velocity, and constant low velocity. Solute transport based on the algebraic expressions was verified against numerical simulations. The algebraic expressions may be used to assess the expected impacts of a surface barrier to the convective transport of contaminants in the vadose zone.

Towards a theory of steady-state solidification process with a quasi-equilibrium two-phase region

AbstractThe process of directional crystallization in the presence of a quasi-equilibrium two-phase region located between the solid material and the liquid phase is studied theoretically. The mathematical model of the process is based on heat and mass transfer equations in the solid, liquid and two-phase regions, as well as boundary conditions at the phase interfaces “solid phase” – “two-phase region” and “two-phase region” – “liquid phase”, which are moving with a constant velocity. The process of directional crystallization is given by fixed temperature gradients in the solid and liquid phases, which determine a constant velocity of melt solidification. An exact analytical solution of the nonlinear problem with two moving boundaries of phase transformation is obtained, which is based on the transition to a new independent variable, the solid phase fraction, when integrating the nonlinear heat and mass transfer equations in the two-phase region. As a result of solving the problem, the distributions of temperature and concentration of dissolved impurity, the solid phase fraction in a two-phase region, the laws and velocities of motion of its interphase boundaries are determined. It is analytically shown that the impurity concentration and temperature in the two-phase region are only the functions of solid phase fraction, which, in turn, depends on the spatial coordinate. Analysis of the obtained solutions shows that the solid phase fraction in a two-phase region can be both a decreasing and increasing function of the spatial coordinate, which is directed from the solid material to the melt. This determines the internal structure of two-phase region, its permeability, average interdendritic spacing, distribution of dissolved impurity, crystallization velocity and laws of two-phase region boundaries.

Environmental and Economic Impact on Scenario-Based Automotive Part Replacement: Case Study of Constant Velocity (CV) Joint Replacement in Korea

The objective of this study is to comprehensively evaluate the environmental and economic impacts of remanufactured constant velocity (CV) joints using a newly proposed framework for automotive parts replacement. This framework utilizes actual vehicle sales data to accurately estimate the demand for CV joint replacements. Specific parameters are established to calculate this demand, enabling a quantitative assessment of both environmental and economic impacts associated with remanufacturing CV joints and other automotive parts. Additionally, sensitivity analyses are conducted to explore the relationship between environmental benefits and economic outcomes, particularly focusing on the preferences for remanufactured parts and their profitability. The results indicate that increasing the proportion of remanufactured CV joints significantly benefits the environment by reducing CO2 emissions, raw material usage, and energy consumption. However, this shift also leads to a decrease in total profits within the CV joint replacement market. To address this trade-off, the study suggests that financial incentives, such as subsidies or tax benefits, are necessary to support the remanufacturing industry and facilitate market expansion. These findings provide valuable insights for policymakers aiming to promote sustainable manufacturing practices through effective subsidy policies.

Active vibration control of metal foam reinforced agglomerated graphene nanoplatelets nanocomposite truncated conical shells with piezoelectric layers

This study examines active vibration control (AVC) in a truncated conical shell composed of metal foam reinforced with agglomerated graphene nanoplatelets and integrated with piezoelectric layers functioning as sensors and actuators. Both complete and partial agglomeration states are considered based on the Eshelby–Mori–Tanaka approach, and the mechanical properties of the porous core are characterized using a closed-cell metal foam model. The governing equations of motion are derived using Hamilton’s principle, based on the two-dimensional axisymmetric elasticity theory, and solved through the finite element method coupled with the Newmark method. Vibration mitigation is achieved using a fractional-order fuzzy proportional–integral–derivative (PID) controller. A comprehensive parametric study is conducted, examining the effects of geometric dimensions, various boundary conditions, reinforcement parameters (including weight fraction, distribution patterns, and agglomeration parameters), and porosity parameters (including pore size, and porosity pattern) on the vibration properties of the shell. Numerical simulations are performed to assess the effectiveness of the proposed AVC system in reducing structural vibrations compared to a constant velocity feedback control approach. The velocity feedback controller reduced central deflection from 12.65 to 5.089 μ m , while a fractional-order fuzzy PID controller further improved it to 2.348 μ m , representing a 53.86% enhancement over the velocity feedback controller.

Study on Cavity Filling Defects and Tensile Properties of L-Shaped Profiled Rings

Severe cavity filling defects and poor mechanical properties increase the difficulty in the integrated forming of L-shaped profiled rings due to its asymmetrical section geometry. A novel rolling method of a C-shaped ring was proposed in this study, and two symmetric L-shaped rings were prepared simultaneously. A numerical model of C-shaped ring rolling was established, and the cavity filling defects in different directions and the overall forming defect were defined for a qualitative analysis of the geometry’s accuracy. The effect of the rolling parameters on the forming defects and ring quality was investigated. The forming defects increased with an increase in the groove depth ratio as well as decreases in the groove angle and rolling ratio. The feeding strategy with a constant ring growth velocity led to the best geometric accuracy and strain uniformity of the C-shaped rings. Optimized rolling parameters can be acquired by the Box–Behnken optimization method with multi-objective optimization of the rolling stability and ring quality. An experiment of C-shaped ring rolling was successfully prepared, based on the optimized parameters. The hardness distribution on the cross-section was symmetric and uniform. The C-shaped ring showed obvious anisotropy of the tensile properties of the cast ring’s blank, and heat treatment had little effect on the improvement of the isotropy.

Polyline Morphing for Animated Schematic Maps

AbstractThematic maps allow for the visual analysis of spatial data. When comparing two map states, preserving the mental map of a user facilitates the comparison. One way to achieve this is to use animated transitions between the states. This work presents an algorithm for computing such animations, called morphs, between schematized map objects, a technique particularly pertinent in urban mobility scenarios where schematic maps improve map legibility. In schematic maps, abstraction is used to reduce the visual complexity while still conveying information on a selected phenomenon. Our method ensures that the morph has four favorable properties: (1) it is self-intersection-free, (2) it maintains the schematization of the input features, (3) it is self-contained, and (4) every segment moves at its own constant velocity. We present an efficient algorithm to compute vertex traces and the timing of the morph. We evaluate our approach on isochrones visualizing travel times and on different layouts of schematic transit networks. The results show that the additional constraints we induce on the morphing only have a minor influence on the optimization target while they reduce the complexity of the animation.

MHD flow of chemically reacting Casson fluid through a moving plate in non-Darcian porous medium with second-order slip velocity

The MHD flow of optically thick, incompressible, chemically reacting Casson fluid through a moving vertical plate exposed in a non-Darcian porous medium with second-order slip velocity is studied in this work. The plate is under a constant suction velocity. A consistently strong magnetic field is anticipated to be applied normally to the plate. This study includes the effects of Joule heating, viscous dissipation, Soret number and heat source. The MATLAB-bvp4c method is employed for solving the associated governing equations. The flow velocity rises with the growth of porosity parameter, solutal Grashof number, thermal Grashof number and Soret number but it decreases with the inertia parameter, chemical reaction parameter and magnetic parameter. The effect of Soret number raises the skin friction.

Assessment of OH femtosecond thermally assisted fluorescence thermometry for hydrogen non-premixed flames

In this work, we further developed the planar temperature measurement method based on thermally assisted laser-induced fluorescence (TALF) with a single femtosecond (fs) laser and investigated the temperature distribution in the nitrogen-diluted oxygen–hydrogen cross-jet non-premixed flames at 1 kHz. Fs-TALF thermometry was firstly calibrated and assessed in a series of unconfined methane/air laminar flames at atmospheric pressure. In the calibration process, although the calibrated energy difference between OH v′ = 0 and 1 energy level was different from the theoretical value, the measured fluorescence ratio accurately reflected the temperature change from 1600 K to 2200 K in different methane flames. By comparing the calculated OH fluorescence spectrum, we believed that the main reason was the overlap of the OH (1-1) and (0-0) fluorescence bands. After the calibration, experiments were conducted with changing hydrogen flow velocity from 60 to 100 m/s and constant oxidizer flow velocity, where the dilution ratio, D varies from 0.46 to 0.7, and the equivalence ratio, ϕ, varies from 0.5 to 0.9. It is found, within the calibration range, fs-TALF thermometry can correctly measure the flame temperature. However, with ϕ further increases, the difference between the measured and theoretical temperatures gradually increases. At the same time, it was noted that the error in the measured temperature rises gradually as D decreases. In conclusion, fs-TALF thermometry can measure turbulent non-premixed hydrogen flames accurately in a range of temperature with acceptable temporal and partial resolution, while the errors within 200 K and spatial resolution is 170μm. The main error source should be the collisional effect due to the different local concentration of N2 and H2O. The results of this work will contribute to the further development the temperature measurement method hydrogen turbulent flames.

Cutting speed and behaviors of ice using Yb-doped fiber laser

The use of a laser to cut or drill ice has been proposed and demonstrated multiple times in previous decades as a novel, but never adopted, machining tool in glaciology and paleoclimate studies. However, with the rapid development of high power fiber-laser technology over the past few decades, it is timely to perform further studies using this new tool. An investigation is made herein on the cutting of ice using a Yb-doped fiber laser emitting at a wavelength of 1070 nm, the most extensively developed and highest power fiber laser technology, in pulsed and continuous-wave operation. Visible-light observations of clear tap water ice samples, moving at a constant velocity relative to a pulsed laser beam, demonstrate a linear relationship between the duration of a millisecond-range laser pulse and the depth of the meltwater-free cut formed in response. Thermal imaging of the irradiated face shows that peripheral heating trends linearly for pulse lengths greater than 5 ms. A comparison of pulse trains with a constant time-averaged power suggests that shorter pulses are advantageous in slot-cutting efficiency and in minimizing visible alterations in the surrounding ice. These results demonstrate the viability of powerful fiber-compatible lasers as a tool for ice sample retrieval and processing.

A variable diameter spiral path planning strategy for large eccentricity variable curvature rotating parts with focus on thickness and performance control in cladding

When laser cladding rotating parts that have large eccentricity and variable curvature, first-order discontinuities in the cladding path and fluctuations in the real-time scanning speed are common problems. These issues cause significant inhomogeneities in the cladding thickness and localized excessive material accumulation. This not only leads to unstable mechanical properties of the cladding layer but also results in a significant waste of cladding materials during subsequent precision machining. In response, this paper introduces a cladding method that employs a variable diameter constant linear velocity spiral path and establishes models for dynamic vector and angle conversion, constant linear velocity optimization, and cladding path data conversion. This approach enables consistent control over the real-time scanning speed and defocus distance during laser cladding of parts with large eccentricity and variable curvature. A comparison of the experimental results from spiral path cladding, variable linear velocity and variable diameter spiral cladding, and constant linear velocity variable diameter spiral cladding revealed that the latter method achieves a more uniform cladding layer thickness, with a maximum deviation of only 0.036 mm. The microstructure primarily consists of cellular structures, demonstrating improved consistency. Samples were taken from three different cladding methods, and hardness tests were performed on the cross-sections of the cladding layers.

Effect of magnetic field on deceleration of ion beam in plasma with ion-acoustic turbulence

The deceleration of a monoenergetic rarefied ion beam in nonisothermal plasma in a constant magnetic field has been studied. It is shown how ion-acoustic turbulence generated by a current along the magnetic field leads to an effective decrease in the velocity of ions moving with a speed higher than the speed of ion sound. When an ion beam is injected into plasma across the magnetic field, the trajectory of the ions has the form of a contracting spiral elongated along the magnetic field. The deceleration occurs due to the Cherenkov interaction of ions with ion-acoustic waves and stops when the ion velocity decreases to the speed of ion sound. The braking lengths and the beam velocity components, which are set at the moment of stopping braking, are found. After the end of deceleration, the ions move with constant velocity in a spiral along the magnetic field.

Two-Step AE Source location for Detecting Tendon Rupture inside PC Box-Girder in-Service

In order to identify tendon rupture inside a prestressed concrete (PC) girder, new acoustic emission (AE) location system is necessary to be practically applied. In PC girder of an in-service highway, PZT sensors are installed at a web and a deck of the PC girder, and elastic waves generated by tendon rupture is simulated by steel ball impact. AE source location assuming the homogeneous velocity distribution is applied in a development view of the box-girder. Then to verify the accuracy of the location results, the effect of elastic-wave propagation at a joined corner between the web and the deck is simulated by FDM. As a result, the attenuation of first-arrival P waves was observed at the joined corner. It implies that wave energy is so attenuated that apparent velocity decreases. Finally, AE locations lead to erroneous solutions in the development view solved with a constant velocity. To solve the problem, a twostep location system is developed. In the first step, two-dimensional plane, where the tendon rupture is to be identified, is selected from the 1st and 2nd arrivals of AE Hits. Then, in the 2nd step, AE locations are determined from remaining AE sensors located on this plane. By applying this system, the location errors are within 5 % at the both web and deck in a 15 m long PC box-girder.

On the transport of a millimeter-sized compound droplet in a Poiseuille flow

The compound droplet consists of the inner and outer droplets. The outer droplet's ability to isolate the inner contents from its surroundings makes applications such as drug delivery, cell encapsulation, and cell sorting possible. Here, we experimentally explore the transport of the compound droplet at different Reynolds numbers, viscosity ratios, and volume ratios. Compound droplets have a longer dimensionless transport distance along the X-axis than single-phase droplets at Reynolds numbers from 44 to 366. When the Reynolds number is increased from 81.2 to 243.7, the dimensionless maximum transport distance of the compound droplet along the X-axis becomes 2.04 times. As the Re increases, the compound droplet deflection rate decreases continuously. For a constant initial velocity of the compound droplet, an increase in the viscosity ratio leads to an increase in the dimensionless velocity along the x axis with the compound droplet during transport. The maximum transport distance along the x-axis increases, and the deflection rate decreases as the inertial and viscous forces increase with increasing viscosity and dimension ratios. The chemical droplets become more stable as a result.

A Formalism for Scalable Maritime Traffic Monitoring and Explainable Anomaly Detection and Resolution at Vessel Traffic Services

Abstract Vessel traffic service (VTS) centres around the globe monitor and manage the ship traffic in their areas of responsibility and respond to arising unsafe or inefficient situations. Decision support tools (DST) help vessel traffic service operators (VTSO) to enhance their situational awareness and decision-making process, thus to recognise and assess dangerous situations. However, current DST have unsophisticated features and require manual configuration by the operator. Firstly, triggers for alerts are mostly based on the creation of geographical polygons for spatial-dependent assignment of rules, thresholds, ranges and limits for specific features. Secondly, calculations for the detection of safety-critical situations rely on measurements based on the closest point of approach (CPA) without taking contextual information into account. Thirdly, trajectory predictions are performed considering a constant velocity model (CVM) which does not depict reality. Due to these and other peculiarities, current DST are prone to false alerts. This results into a high workload where unsafe situations may be overlooked. In this paper, we propose a hierarchical formalism as foundation for an anomaly detection and resolution which generates less false alerts. The formalism consists of three hierarchical layers which represent, objects, measurements and situations. The formalism ensures adaptability and extensibility to various VTS areas and traffic patterns. Moreover, due to the given structure, the presented formalism is easily implementable, adaptable and scalable taking the currently available technological capabilities at VTS centres into account. We demonstrate the feasibility of this formalism by implementing a proof-of-concept and assessing it with realistic scenarios. Our implementation utilizes a rule-based system as central framework and it is configured through statistical methods, e.g. machine learning. Given this hybrid approach, the implementation provides reasonable and explainable results. This enables comprehensibility and verifiability by authorities and operators which is crucial for acceptance.

A novel technique to resolve directional ambiguity for Particle Streak Velocimetry

In this study, a novel streak direction-resolving algorithm is introduced to determine the direction of the flow field for a single image frame with multiple streaks. The streak direction was resolved by varying its intensity from 100% to 50% of the total intensity of the streak image. This technique was applied to two main types of flows parallel and Hill’s vortex flows, parallel flows were divided into further two types constant velocity parallel flow and accelerating parallel flow. The purpose of using different types of flows was to test the robustness of the algorithm with easy and complex flows. The performance of the algorithm was checked by the angular deviation between the true and least-square fitted velocity vectors. The number of correct synthetic streak directions was measured with the success rate in percentage. A high success rate means low angular deviation and a high number of velocity vectors with correct direction was obtained. In this research, four different types of image formats were considered DP (double precision), 16-bit (without noise), 16-bit (1.0% noise), 16-bit (5.0% noise), and 8-bit (without noise) and the best results were obtained for DP and 16-bit image formats. The results of the parallel flows indicated a 100% streak direction success rate, Hill’s vortex was a type of complex flow therefore, the algorithm hard to resolve some streak directions due to very low velocities (less than 0.1 px (pixel)/interval) and very high-velocity gradients (greater than 52 px/interval). The observation shows that Hill’s vortex synthetic streak images were resolved with a success rate of 92.76% which means that the majority of the synthetic streaks were resolved. Experimental analysis was also done by using the PDMS microchannel setup. Intensity variation streaks were recorded with long camera exposure time and for maintaining the intensity variation, as the LED switched on maximum illumination was started, and continuous decrement in illumination was set by switching off at 50% of the total illumination intensity. The best results were achieved with a 94% success rate. Therefore, the proposed novel approach can be used with less expensive hardware for image processing with a single image frame and is useful for multiple applications.

Achieving solar sail orbital maintenance with adjustable ballast masses in the ERTBP

An innovative method for orbital maintenance in the Sun-Earth Elliptic Restricted Three-Body Problem (ERTBP) is introduced. The concept arose from observing that Natural Periodic (NP) orbits in the ERTBP exhibit deviations from their periodic behavior over time. These NP orbits are derived solely from accurately specified initial orbital conditions. Hence, a strategy for orbital maintenance becomes essential for these missions. This approach utilizes NP orbits as the designated reference trajectory to be tracked by the spacecraft. It assumes a solar sail equipped with two ballast masses and suggests a Fully Coupled Orbit-Attitude (FCOA) model. In this comprehensive model, both orbital and attitude states mutually influence each other, enabling orbital adjustments through attitude control. Therefore, the first step involves developing the governing equations for this FCOA model incorporating two ballast masses within the ERTBP. The strategy includes dividing the NP orbit period into τ equal time intervals. During each interval, adjusting the velocity of the ballast mass using a 7-mode electrical motor facilitates precise attitude control, establishing a framework for orbital maintenance. Maintaining constant velocity within each interval simplifies achieving the desired ballast mass positions. The adjustment of ballast mass velocity is proposed to be conducted using a hybrid meta-heuristic Invasive Weed Optimization/Particle Swarm Optimization (IWO/PSO). The analysis examines how increasing the mass of the ballast masses enhances tracking performance, underscoring the critical role of mass in optimizing tracking capabilities. This highlights the significance of meticulous structural design in achieving superior outcomes for orbital maintenance missions.

Investigating Dual Inlet Cyclone Separator Performance: Effects of Vortex Finder Diameter, Shape, and Particle Diameter on Separation Efficiency and Pressure Drop

The diameter and shape of the vortex finder of cyclone separator plays a significant role in separation efficiency and pressure drop. Currently, there have been many studies conducted on the shape and ratio of vortex finder of cyclone separator. This paper aims to compare numerical results of Raynold stress turbulence model RSM with K-ε RNG numerical analysis results and analyse the effect of further variation of the vortex finder diameter and shape of dual inlet cyclone separators. Five variation of vortex finder diameters namely 291mm, 310mm, 330mm, 348mm, and 366mm, four types of vortex finder shapes namely normal (cylindrical), spiral, divergent and spiral-divergent have been studied with different particle diameter and constant inlet velocity. The result obtained from this study suggests that increasing the vortex finder diameter have negative effect on separation efficiency. It also shows that increasing the vortex finder diameter consistently decrease the pressure drop. From the result, it is been found that the 291mm vortex finder has higher separation efficiency than the rest. Analysis with different vortex shapes, the spiral-divergent shape proved to be best in terms of separation efficiency.

Numerical Investigation of Flow Characteristics in Internally Flowing Pipes with Varying Roughness and Helical Angles of Vortex Generators

In this study, the turbulent behavior inside a pipe containing an aluminum helical vortex generator plate was investigated using computational fluid dynamics (CFD) methods, considering different plate roughness and helical angle values. Accordingly, numerical analyses of velocity and pressure distributions for a liquid flow with a constant inlet velocity of 0.5 m/s and four different helical angles were performed and compared in a computer software. To observe the effects of the roughness values of the metal plate on flow behavior, analyses were conducted for three different roughness values for each helical angle and the results were compared and interpreted. As a result of the study, the combination of a roughness value of 0.04 and a helical angle of 0° led to the highest pressure and velocity values, while the same roughness value combined with a 270° helical angle resulted in the lowest pressure and velocity values. Detailed analysis showed that helical angles (90° and 180°) presented moderate pressure and velocity values, indicating a non-linear relationship between helical angle and flow characteristics. The results demonstrate that optimizing the helical angle and roughness is crucial for enhancing the efficiency of vortex generators. This way, a design will be developed to prevent performance degradation in industrial applications that require flow efficiency and pressure management.

Numerical study of dynamic stall effects on VR‐12 airfoil with pitch oscillation and accelerated inflow

AbstractThis study investigates the effects of positive horizontal acceleration of the freestream velocity on a pitch‐oscillating VR‐12 airfoil using computational fluid dynamics. The shear stress transport k–ω model, coupled with a low‐Reynolds number correction, was employed for Re <105 during dynamic stall. The flow equations were solved in two‐dimensional, incompressible form using the finite volume method. The study examined various parameters, including positive acceleration values of the inflow and the angle of attack of the airfoil, to determine their impact on lift and drag coefficients, as well as the ratio. Additionally, the maximum lift coefficient was analyzed under different inflow and airfoil motion conditions. The results indicate that aerodynamic force coefficients and the ratio are influenced by both the attack angle and the acceleration of the inflow. Furthermore, inflow acceleration affects the onset of dynamic stall conditions. Generally, inflow acceleration modifies the lift coefficient of the airfoil during the upstroke, while having minimal effect on the drag coefficient, except near dynamic stall points. The findings also suggest that, for a specific airfoil, the sequence of factors with the greatest influence on lift force generation before static stall occurs is as follows: asymmetric airfoil oscillation, symmetrical airfoil oscillation, accelerated inflow, constant velocity inflow, and static airfoil.

Experimental and Numerical Investigation for Optimization of a Hybrid Battery Thermal Management System based on PCM and Air Convection

Abstract This work presents the design and optimization of a phase change material (PCM) based hybrid battery thermal management system (HBTMS). In the first stage, experiments are performed to measure the battery cell temperatures under various charge rates with and without the usage of PCM. Thereafter, a numerical model is developed to conduct a parametric study on the effect of thickness of PCM layer around the battery cell. The maximum cell temperature (36.35°) and thermal nonuniformity are within the safe range for the PCM thicknesses of 6 to 12 mm. In the second stage, a parametric study is conducted in the 6S1P battery module to optimize the spacing between the cells at constant inlet velocity. The maximum temperature is within the optimal range when the cell spacing is 10 mm. At the constant cell spacing of 10 mm, increase in inlet velocities from 0.25 m/s to 2.5 m/s gradually improves the thermal non-uniformity. The maximum temperature and thermal non-uniformity for 6S1P battery module is found to be 42.07° and 1.17° respectively. In the third stage, 6S1P battery module is optimized for PCM thickness, cell spacing and inlet air velocity. It is found that effective thermal management is possible with PCM based HBTMS at low airflow rate of up to 1.5 m/s. The optimized PCM based HBTMS shows 46.59% and 40% reductions in PCM mass and air flow rate respectively.