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- Performance characteristics of humpback whale tubercles at low Reynolds
numbers
Authors: H. Ladha, M. A. Gandhi, K. Singh, S. M. Dakka
Pages: 1 - 19
Abstract: Many marine vessels and small unmanned air vehicles operate at low Re flow regimes. Due to their small size and low operational velocities, they face increased stall severity, which is a crucial challenge to overcome. Tubercle Leading Edge (TLE) aerofoils can be exploited to solve this issue. Akin to passive flow control devices, tubercles generate counter-rotating vortex pairs on aerofoils, with vorticity being proportional to amplitude to wavelength ratio thus augmenting lift, and delaying flow separation. Performance improvements such as reduced drag, reduced stall severity, and improved post-stall characteristics are achieved using TLE designs. This investigation experimentally and numerically is focused on the performance characteristics of three designed TLE aerofoils at a relatively low Re value of 1x105. Limited studies are available on this low Re flow regime, hence the novelty of this investigation. The aims were to build upon the literature and to determine the best TLE aerofoil variant for further investigation, development, and eventual system-level implementation in a small naval or air vehicle design. The TLE aerofoil models investigates, ‘A4λ25’, ‘A8λ25’, and ‘A12λ25’ which specify the tubercle amplitude and wavelength in mm delivered weaker and delayed stall, reduced pre-stall drag, and improved post-stall lift. The ‘A4λ25’ model offered the best combination of increased pre-stall lift, reduced pre-stall drag, and post-stall lift. Further investigation on the ‘A4λ25’ variant’s performance within the context of an engineered system is worthwhile for realizing its application in low Re flight. Journal of Naval Architecture and Marine Engineering, 22(1), 2025, PP. 1-19
PubDate: 2025-01-28
DOI: 10.3329/jname.v22i1.72607
Issue No: Vol. 22, No. 1 (2025)
- Augmenting thermal-material transport in boundary-layer flow over an
upright sheet: an explicit finite difference approach
Authors: Mohammad Jahir Uddin, Rehena Nasrin, Eid S. Alatawi
Pages: 21 - 40
Abstract: The thermal-material transport in boundary-layer flows has significant implications for industries such as petroleum and agricultural engineering, gas turbines, nuclear power facilities, heat exchangers, cooling systems, and chemical processing. This particular investigation seeks to understand how thermal and solute buoyancy forces impact the fluctuating flow of a boundary layer over an upright permeable flat sheet with heat generation. It is crucial across various fields, advancing scientific understanding and practical engineering applications. This analysis requires modifying the nonlinear and time-varying partial differential equations (PDEs) to address the continuity, momentum, energy, and concentration balance equations. After developing a mathematical model, the explicit finite difference method (EFDM) is utilized to solve a set of nonlinear dimensionless partial differential equations along with the suitable boundary conditions (BCs). The EFDM technique is thoroughly described in a step-by-step manner, tailored to the specific model being analyzed. The stability, convergence, finding a suitable uniform meshing, steady-state condition, and code validation are conducted. This study focuses on velocity, temperature, and concentration distributions that are affected by incoming physical forces, such as buoyancy force and heat production. It analyzes the mean and local rates of skin friction coefficient and heat-material transports. The findings demonstrate that as buoyancy increases, fluid velocity rises, and that increasing heat generation increases heat-mass heat transmission rates. The practical behavior is a result of the pressure gradient caused by thermal buoyancy force. Two novel linear regression equations with multiple variables are derived from the outputs. By combining advanced modeling techniques, incorporating variable properties, applying unsteady analysis, considering surface porosity, and examining heat generation, and thermal-solutal buoyancy force effects, this study provides a comprehensive and versatile framework for enhancing understanding and optimizing boundary-layer flows in numerous practical applications. Journal of Naval Architecture and Marine Engineering, 22(1), 2025, pp. 21-40
PubDate: 2025-01-28
DOI: 10.3329/jname.v22i1.77636
Issue No: Vol. 22, No. 1 (2025)
- Numerical exploration of MHD non-Newtonian nanofluid flow past a
bidirectional surface with radiation and Joule’s heat
Authors: T. Jayachandra Reddy, B. Ramoorthy Reddy, A. Mohanarami Reddy
Pages: 41 - 47
Abstract: The present study investigates the influence of a magnetic field on the three-dimensional movement of Casson nanofluid over a rotating, stretchable surface embedded in a porous medium. The effects of various parameters on the fluid dynamics are also analyzed. The governing nonlinear partial differential equations (PDEs) representing the fluid flow problem are converted into dimensionless ordinary differential equations (ODEs) using similarity transformations. These resulting ODEs are then solved numerically using the R. K. based Shooting method. The impact of various parameters on the flow profiles is illustrated through graphical representations. It is observed that the velocity profile decreases with an increase in the magnetic field number. Moreover, higher non-Newtonian parameter values lead to an increase in the primary velocity while showing a decreasing trend in the secondary velocity. Journal of Naval Architecture and Marine Engineering, 22(1), 2025, pp. 41-47
PubDate: 2025-01-28
DOI: 10.3329/jname.v22i1.78578
Issue No: Vol. 22, No. 1 (2025)
- Heat and mass transfer of MHD Williamson fluid flow past a shrinking/
stretching sheet with dual stratification, radiation, Joule heating effect
Authors: Vardireddy Sujatha, Wuriti Sridhar
Pages: 49 - 61
Abstract: The current study examines the Williamson fluid flow on a stretching sheet under the effects of MHD and porous material. In addition, the effects of different characteristics—such as heat source, viscous dissipation, joule heating, and chemical reaction—are examined. The influence of solutal stratification factors and temperature was also investigated.. Partial differential equations are used to represent the problem's governing non-linear equations. These equations are converted into a set of non-linear ordinary differential equations with the necessary similarity transformations. The resulting equations are solved numerically using the Keller Box technique. The influence of various parameters is examined by constructing graphs of velocity, temperature, concentration. Additionally, local parameters are computed and compared with findings from earlier research; the results show compatibility. Profiles of velocity exhibit decreasing behaviour in case of Williamson, Magnetic, and Permeable parameter. Profiles of temperature exhibit increasing behaviour in case of Williamson, Magnetic, Radiation, Joule heating, Heat source, Eckert number parameters whereas opposite trend is witnessed in case of Prandtl number, thermal stratification parameters. Concentration profiles enhances in case of Williamson, Magnetic, permeability parameters and opposite behaviour is examined in case of Chemical reaction, solutal stratification, Schmidt number parameters. Journal of Naval Architecture and Marine Engineering, 22(1), 2025, pp. 49-61
PubDate: 2025-01-28
DOI: 10.3329/jname.v22i1.76875
Issue No: Vol. 22, No. 1 (2025)
- Numerical study on the hydrodynamic performance of a self-propelled
submersible
Authors: M. A. Zenagui, S. E. Belhenniche , A. Miloud, O. Imine
Pages: 63 - 80
Abstract: In this paper, a numerical study of the hydrodynamic performances of an autonomous unmanned vehicle (AUV) is proposed. For its propulsion, a model of a new seven-bladed propeller defined as stock propeller was created. Using FLUENT code, many numerical simulations were carried out, namely tests in open water, towing resistance and self-propulsion. This study is particularly focused on the thruster's ability to perform its task correctly in view of a possible improved use. The examination of the propeller characteristics in open water test exhibits a better efficiency and the thrust can be improved by slightly adjusting the pitch distribution of the propeller. In the towing resistance test, wake behind the body was also investigated by studying axial velocity field in many transversal planes. Added to the self-propulsion test results, the evolution of the thrust magnitude in the wake by moving the thruster plane axially reveals that the required thrust level is reached far behind the actual position of the thruster disc. Therefore, the ratio of thrusts with or without the presence of the body is equal neither to unity nor to the ratio of torques. Journal of Naval Architecture and Marine Engineering, 22(1), 2025, PP. 63-80
PubDate: 2025-01-28
Issue No: Vol. 22, No. 1 (2025)
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