This study explores the magnetohydrodynamic (MHD) pulsatile flow of Jeffrey liquid layers separated by a micropolar liquid layer, confined between two permeable beds. The flow domain is divided into three distinct regions: Regions A and C, which contain Jeffrey fluid, and Region B, which contains a micropolar fluid. The liquid-permeable bed interfaces are governed by the Beavers-Joseph slip boundary condition. The governing equations are solved numerically using the NDSolve function in Mathematica. The effects of various physical parameters on velocity profiles, mass flux, and microrotation velocity are illustrated graphically. Additionally, stress distributions are analyzed and presented in tabular form. The results reveal that the applied magnetic field has a pronounced influence on the flow characteristics compared to the purely hydrodynamic case. Our analysis indicates that the stress distribution at the permeable boundaries increases with Reynolds number, slip coefficient, porosity, and Jeffrey fluid parameters. Furthermore, mass flux is found to increase with the Reynolds number, Jeffrey parameter, and micropolar material parameter, while it decreases with an increase in the Hartmann number. A comparative analysis of our results with other researchers shows good agreement.
This study examines the influence of Propeller Boss Cap Fins (PBCFs) on the hydrodynamic performance of B-series propellers by introducing variations in installation angles. While PBCFs are widely recognized for their potential to reduce rotational losses and enhance propulsion efficiency, the specific impact of installation angle variation-particularly in the context of electric-powered vessels- has remained underexplored. To address this gap, the present work focuses on the aerodynamic optimization of PBCFs, varying the installation angle between-5 degrees and 5 degrees, using a NACA4412 airfoil profile within a Computational Fluid Dynamics (CFD) framework. The analysis is conducted using the Reynolds-Averaged Navier-Stokes (RANS) approach with a Grid Independence Test (GIT) performed to ensure numerical accuracy. Validation of the simulation results against available experimental data confirms the reliability of the model. The configuration featuring a 2 degrees PBCF installation angle demonstrates the most favorable performance, yielding an increase in the thrust coefficient (KT) from 0.3719 to 0.3797 and an improvement in open water efficiency (eta) by 4.3% relative to the baseline CFD model. Additionally, a maximum efficiency enhancement of 24% is observed when compared to experimental data at an advance coefficient of J = 0.415. The validation results exhibit a maximum deviation of 9.934% at lower rotational speeds, which is within an acceptable range for engineering applications, particularly given the challenges of modeling complex flow phenomena at low Reynolds numbers. The principal contribution of this study lies in its systematic evaluation of PBCF installation angle as a design variable-an area that has received limited attention in existing literature. The findings demonstrate that even minor angular modifications can significantly influence propeller performance. More broadly, this research contributes to the advancement of energy-efficient marine propulsion technologies by offering a validated, CFD-based design methodology. The implications are particularly relevant for the development of sustainable propulsion systems in electric and low-emission vessels, supporting broader efforts to reduce fuel consumption and minimize environmental impact in maritime operations.
Accurate numerical simulation of flow over bodies, when there is an angle of attack, is challenging even when the body is slender and axisymmetric. Two methods are widely used in such simulations, but no study clearly compares the accuracies and the advantages and disadvantages of the methods. In the body rotation method (BRM), the flow is along the axis of the domain, and the body is rotated such that the angle between the main axis of the body and the flow direction is the angle of attack. In the flow rotation method (FRM), the axis of the body is along the axis of the domain, and the direction of the flow is changedto simulate the angle of attack. In the present study, both methods are usedat a Reynolds number of 12 x 10(6). The Computational Fluid Dynamics (CFD) package is used to simulate flow over an axisymmetric three-dimensional (3D) bare hull submarine model, and the angle of attack is varied from 0 degrees to 18 degrees. In both BRM and FRM approaches, steady Reynolds Average Navier Stokes (RANS) equations are solved using the k - omega Shear Stress Transport (SST) turbulence model, with non-dimensional wall adjacent cell thickness (Y-omega(+)) kept below1. The same domain and mesh commands are used in both methods. The hydrodynamic forces, moments, coefficients of wall shear stress, and pressure computed using the two methods differ by less than two percent. The distribution of the sizes of cells and the number of cells of various shapes are also presented. When meshed with cells in the wall-adjacent region having the same size, the number of cells and computation time are much less in the body rotation method, and it is therefore preferred.
In the present study, a comprehensive experimental and numerical investigation has conducted to simulate and predict the thermal profile in weld joints of modified 9Cr-1Mo (P91) steel plates, with a particular focus on the influence of varying welding heat input. This study primarily investigates the thermal characteristics of the Submerged Arc Welding (SAW) process using a moving heat source model based on a Gaussian distribution. A methodology based on the Finite Difference Method (FDM) is developed and implemented using MATLAB to accurately estimate the thermal profile. The results show good agreement between the numerical and experimental data, with an overall error ranging between 6% to 9%, thereby confirming the accuracy and reliability of the proposed numerical model. Finally, the results emphasize the critical role of welding parameters in shaping the thermal profile. It has observed that increasing the welding current, while maintaining a constant welding speed, has resulted in higher heat input and elevated weldment temperatures. The peak temperatures have recorded as 155 degrees C, 198 degrees C, and 210 degrees C at welding speeds of 0.60 m/min, 0.75 m/min, and 0.90 m/min, respectively. A maximum percentage difference of 7% has found between the experimental and numerical results, further validating the accuracy of the proposed model.
This study aims to design, optimize, and validate an all-electric propulsion system for a 25 m x 7 m aluminum catamaran ferry operating on a 25 km urban river route, focusing on power requirement prediction, battery sizing, energy-management strategies, and shore-charging integration. A slender-body resistance model, validated by cubic speed-power scaling, predicts calm-water resistance rising from 18.5 kN at 12 knot to 43.8 kN at the contractual speed 19 knot. Accounting for hull and drivetrain efficiencies yields a continuous shaft power requirement of 707 kW. Two 360 degrees Hydromaster D-series azimuth thrusters driven by 375 kW permanent-magnet motors are selected, providing 6 % continuous head-room and full redundancy while avoiding the mass penalty of a single 1 MW unit. Daily energy demand is quantified via a mode-based load matrix distinguishing propulsion, hotel, and intermittent peaks. Twelve round trips within a 17 h duty window consume 16.1 MWh for propulsion and 0.09 MWh for auxiliaries (16.2 MWh total). Limiting depth-of-discharge to 80% and reserving 20% state-of-charge for emergencies yields a 20.3 MWh lithium-iron-phosphate battery bank (204x100 kWh modules; 127 t, 68 m(3)) fitted amidships. Opportunity charging during each 25 min turnaround with a 6 MW liquid-cooled DC connector restores 1.7 MWh per call, maintaining the pack between 40% and 80% SOC and eliminating the need for 20-48 MW fast-charge infrastructure. This paper applies a Genetic Algorithm (GA) to optimize the decision vector P-thr, C-bat, P-chg, yielding a 12 % reduction in daily energy consumption compared to the baseline design. Convergence behaviour, optimal parameter values, and trade-offs between energy and capital cost are presented. Load-levelling strategies-radar standby, demand-controlled ventilation, and regenerative braking-trim hotel consumption by up to 15 % and reduce peak inverter currents. Sensitivity analysis shows that lowering service speed to 17 knot cuts daily energy by 23%, highlighting the trade-off between timetable and shore-power investment. By integrating resistance prediction, thruster selection, battery sizing, and charging strategy into a single framework, this research demonstrates the technical and operational feasibility of zero-emission river ferries and provides a repeatable methodology for future deployments in similarly constrained waterways.
