Browsing by Author "Samaraweera, N"

Now showing 1 - 8 of 8

item: Conference-Full-text
A computational study of the aerodynamics of plunging and pitching motions of airfoils
(IEEE, 2022-07) De Silva, L; Samaraweera, N; Jayaweera, N; Sugathapala, T; Rathnayake, M; Adhikariwatte, V; Hemachandra, K
Investigation of flow characteristics and force generation of flapping wings have received significant attention in modern fluid dynamics due to emerging applications like bio-inspired Micro Air Vehicles (MAVs) and energy harvesters. In this study, aerodynamic characteristics of NACA 2412 airfoil in plunging and pitching motion are simulated using an incompressible Navier Stokes solver in varying Reynolds and Strouhal numbers. The wake of the airfoil which is visualized using velocity and pressure contour plots and aerodynamic force generation are analyzed. A close agreement is obtained between numerically simulated aerodynamic characteristics including wake structure and forces in this study and experimental results in the literature. The analysis discloses that wing-wake interaction enables a dramatic increment in trust and lift forces up to 300%. Moreover, aerodynamic forces generated in combined pitching and plunging motion show a maximum of 225% increment from the numerical sum of forces in the two sub-motion in some combinations of Reynolds and Strouhal numbers, demonstrating the coupled behaviour of plunging and pitching motions.
item: Conference-Full-text
Design and analysis of an aerodynamic structure for a ground and aerial vehicle
(IEEE, 2022-07) Wijenayaka, RS; Bamunuge, R; Sameem, S; Amarasinghe, R; Samaraweera, N; Rathnayake, M; Adhikariwatte, V; Hemachandra, K
This paper proposes a novel hybrid approach for ground and aerial locomotion. Conceptual designs have been created for ground and aerial platforms and analyzed them separately. 3D models are optimized considering the practicality and ease of manufacturing. Mecanum wheels have been integrated with the ground platform to enable multidirectional locomotion. Thrust vector system has been added to quad rotor aerial platform to increase the forward propulsion. Mathematical models are generated and simulated to visualize the motion virtually and to derive torque requirement to select suitable actuator components. FEA (Finite Element Analysis) analysis proved the proposed platform can withstand the predefined load conditions (10kg) with a good safety factor of 5.9. Combined platforms have been subjected to CFD (Computational Fluid Dynamics) analysis and it has been proved that platform lift force is significantly increased (by 3.5N) compared to traditional quad rotor configuration due to the aerodynamic body.
item: Conference-Full-text
Design and experimental characterization of a soft bending actuator for morphing aerofoils
(IEEE, 2023-12-09) De Silva, K; Maduranga, S; Chamika, V; De Silva, L; Kulasekera, AL; Samaraweera, N; Jayaweera, ND; Abeysooriya, R; Adikariwattage, V; Hemachandra, K
This paper presents the design, simulation, and experimental validation of a vacuum-driven, soft-bending actuator for morphing wing development for small fixed-wing unmanned aerial vehicles (UAVs). The actuator uses an origami-inspired folding mechanism as its control skeleton. A flexible 3D printed structure employing the NACA 2415 aerofoil was used for the development of the morphing aerofoil, driven by the proposed soft actuator. An experimental evaluation of the bending angle and blocking force characteristics of the proposed actuator was conducted. The actuator has achieved a maximum bending angle of 18.75°, while the maximum blocked force at the tip measured 4.8 N at 40 kPa (abs) pressure. Furthermore, aerodynamic simulations revealed that increasing the length of the morphing section with respect to the aerofoil length (Morphing Section Ratio: MSR) resulted in elevated Cl and Cd, while the maximum Cl/Cd values are achieved near the trailing edge morphing. The findings of this study suggest the suitability of soft actuators in the development of flexible morphing wing structures for smallscale UAVs.
item: Conference-Full-text
A design framework for subsonic low-speed wind tunnels
(IEEE, 2023-12-09) Jayasooriya, DL; Wedikkara, CVP; Kodithuwakku, HKH; Samaraweera, N; Abeysooriya, R; Adikariwattage, V; Hemachandra, K
Wind tunnels can be used to perceive the aerodynamic behaviour around objects by sending streamlined air at suitable speeds. This paper entails the details of work focusing on building a design framework for subsonic low-speed (wind speeds less than a Mach number of 0.3) wind tunnels with a medium-scale test section, which reduces the mathematical modelling and analysis required in designing a wind tunnel from scratch, and in turn, reduces the cost. The approach to building the design framework is based on non-dimensional parameters of the component geometry. In order to obtain the most optimum non-dimensional parameters for each critical component (mainly contraction and diffuser), a computational fluid dynamics (CFD) analysis followed by a MOGA (Multi-Objective Genetic Algorithm) design optimization is performed using the ANSYS software package. A combined model of contraction, test section and diffuser is optimized using ANSYS DesignXplorer, governed by objectives set for an optimum flow condition in the test section. In the optimization process, flow simulations are done through ANSYS FLUENT. Using the resulting optimum non-dimensional parameters, a database is developed for different test section dimensions in the medium-scale range. The database is then fed into an online platform (https://blk-vol1-2f260.web.app/) where users can obtain complete design specifications for the wind tunnel by entering the required wind speed and test section dimensions.
item: Article-Full-text
How can we turn heat into useful energy using nanotechnology?
(2023-08) Henadeera, P; Samaraweera, N; Ranasinghe, C; Wijewardane, A
In 1821, the German physicist Thomas Seebeck made a groundbreaking discovery that revealed the direct conversion of heat energy into electricity. He did so by bringing two different metals together and holding one end heated and the other end cooled. This process is famously known as the Seebeck effect. William Thomson, a British physicist later known as Lord Kelvin, further developed the concept of thermoelectric circuits and introduced the idea of a temperature-dependent voltage in a circuit made of two dissimilar metals. Lord Kelvin’s contribution to the field of thermoelectricity paved the way for various applications in temperature sensors, power generators, refrigeration, and cooling systems.
item: Article-Full-text
A molecular dynamics study of thermal conductivity and viscosity in colloidal suspensions: From well-dispersed nanoparticles to nanoparticle aggregates
(Elsevier, 2023) Somarathna, C; Samaraweera, N; Jayasekara, S; Perera, K
This study investigates the microscopic transport behavior of nanofluids addressing some debatable points including the anomalous thermal conductivity ( ), against the predictions of classical effective medium theories. International Nanofluid Property Benchmark Exercise (INPBE) [J. Buongiorno et al., J. Appl. Phys. 106 (2009) 094312] has shown that no such anomaly found in well-dispersed nanofluids after conducting experiments for range of different types of nanofluids. However, a number of molecular dynamics based studies reported otherwise making inconsistent conclusion with INPBE. In this work, it is argued that the over predicted values reported in previous computational studies can be attributed to the ill-defined partial enthalpy formulation of the Green-Kubo method for multicomponent systems. Present study begins by addressing this issue via non-equilibrium molecular dynamics and shows that the results are in agreement with the conclusions of INPBE. Further, it is shown that the contribution of potential micro-mechanisms such as micro-convection due to Brownian motion, and the solid-like liquid layering are either absent or suppressed by the interface thermal resistance. The observed decreasing trend of viscosity enhancement to thermal conductivity enhancement ratio ( ) with increasing particle size indicates the improved heat transfer performance in nanofluids with larger nanoparticles. The effect of nanoparticle aggregation, the proposed originative mechanism of anomalous , is evaluated arranging nanoparticles as chain-like structures. A 67% improvement in is achieved with negligible viscosity variation. This rapidly reduces indicating better heat transfer performance with the presence of conductive paths due to the aggregation or in general extended nanostructures.
item: Article-Full-text
Should We Care about how Birds Fly?
(2023-08) De Silva, L; Samaraweera, N; Jayaweera, N; Sugathapala, T
Bird flight has intrigued human minds ever since the Stone Age. Paintings in Lascaux cave in France are considered the oldest representation of birds in flight made by early ancestors of humans. The ability to fly has been interpreted as a divine power by some cultures which proceeded to include wings in drawings and sculptures of their deities. In the Renaissance period, Polymaths like Leonardo Da Vinci studied birds and their motion in detail. His codex of birds mentions the objective of this study as to develop a human-powered flying machine. Even, the Wright brothers used warping wings in their flight tests mimicking the flight patterns of birds. The wing and fuselage design of fixed-wing aircraft from the earliest versions to modern jet-powered airliners is directly inspired by the bio-mechanics of large birds. However, with the success of fixed-wing aircraft, the flapping wing concepts saw declining interest as a viable design option for air vehicles. During this time, the aerodynamics of bird wings was only studied in fundamental science to answer the questions on their aerodynamic performance. However, the popularization of Unmanned Arial Vehicles (UAVs) renewed the interest in bird-inspired air vehicles with flapping wings as a possible design.
item: Conference-Full-text
Ultra-low thermal conductivity of laterally arranged nanowire arrays through constriction engineering
(IEEE, 2023-12-09) Henadeera, P; Somarathna, C; Satheekshana, W; Withanage, Y; Samaraweera, N; Abeysooriya, R; Adikariwattage, V; Hemachandra, K
Nanostructured semiconductor materials exhibit remarkable thermal insulating properties compared to their bulk counterparts, making them highly promising for Thermo-Electric (TE) applications. This study employs computational tools to investigate the superior thermal insulating properties of Nanowire Chain (NWC) structures achieved through constriction engineering of laterally aligned nanowire arrays. Various surface and constriction modifications of NWCs are investigated to understand their impact on the thermal conductivity. The results demonstrate that the NWC structure achieves a substantial oneorder reduction in thermal conductivity compared to nanowires and nanosheets of similar dimensions. Moreover, this study evaluates the effectiveness of commonly used phonon suppression techniques, such as superlattice structures, shell alloying, and surface atom removal, in NWC configurations. The comprehensive analysis provides valuable insights into the phonon transport characteristics within different classes of NWCs, shedding light on their potential for diverse applications in the field of TE materials and thermal insulators.