Syam Narayanan S. and Asad Ahmed R.
The purpose of this study is to experimentally analyse the effect of flexible and stiffened membrane wings in the lift generation of flapping micro air vehicle (MAV).
Abstract
Purpose
The purpose of this study is to experimentally analyse the effect of flexible and stiffened membrane wings in the lift generation of flapping micro air vehicle (MAV).
Design/methodology/approach
This is analysed by the rectangle wing made up of polyethylene terephthalate sheets of 100 microns. MAV is tested for the free stream velocity of 2 m/s, 4 m/s, 6 m/s and k* of 0, 0.25, 1, 3, 8. This test is repeated for flapping MAV of the free flapping frequency of 2 Hz, 4 Hz, 6 Hz, 10 Hz and 12 Hz.
Findings
This study shows that the membrane wing with proper stiffeners can give better lift generation capacity than a flexible wing.
Research limitations/implications
Only a normal force component is measured, which is perpendicular to the longitudinal axis of the model.
Practical implications
In MAVs, the wing structures are thin and light, so the effect of fluid-structure interactions is important at low Reynold’s numbers. This data are useful for the MAV developments.
Originality/value
The effect of chord-wise flexibility in lift generation is the study of the effect of a flexible wing and rigid wing in MAV. It is analysed by the rectangle wing. The coefficient of normal force at different free stream conditions was analysed.
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Syam Narayanan S., Rajalakshmi Pachamuthu, Alex T. Biju and Srilekha Madupu
This study aims to discuss the mathematical modelling of a compliance-assisted flapping mechanism and morphable structures for an UAV.
Abstract
Purpose
This study aims to discuss the mathematical modelling of a compliance-assisted flapping mechanism and morphable structures for an UAV.
Design/methodology/approach
A compliance-assisted flapping wing was designed and modelled mathematically, and signals for the corresponding curves were calculated. The actual wing tip trace of a hummingbird was taken, and variables a, b, h and k were calculated from the image. This data was given to the mathematical model for plotting the graph, and the curve was compared with the input curve. The wing frame and mechanism for control surfaces using morphing is modelled along with single pivoted spine for centre of gravity augmentation and flight orientation control.
Findings
The model efficiently approximates the 2D path of the wing using line segments using the muscle and compliance mechanism.
Practical implications
Using a compliance-assisted flapping mechanism offers practical advantages. It allows us to synchronize the flapping frequency with the input signal frequency, ensuring efficient operation. Additionally, the authors can enhance the torque output by using multiple muscle strands, resulting in a substantial increase in the system’s torque-to-weight ratio. This approach proves to be more favourable when compared to conventional methods involving motors or servos, ultimately offering a more efficient and robust solution for practical application.
Social implications
This model focuses on creating a flexible and tunable mechanism that can at least trace four types of wing traces from the same design, for shifting from one mode of flight to another.
Originality/value
Conventional ornithopter flapping mechanisms are gear or servo driven and cannot trace a wing tip, but some can trace complicated curves, but only one at a time. This model can trace multiple curves using the same hardware, allowing the user to program the curve based on their needs or bird. The authors may vary the shape of the wing tip trace to switch between forward flight, hovering, backward flying, etc., which is not conceivable with any traditional flapping mechanism.
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Syam Narayanan S., Asad Ahmed R., Jijo Philip Varghese, Gopinath S., Jedidiah Paulraj and Muthukumar M.
The purpose of this paper is to experimentally analyze the effect of wing shape of various insects of different species in a flapping micro aerial vehicle (MAV).
Abstract
Purpose
The purpose of this paper is to experimentally analyze the effect of wing shape of various insects of different species in a flapping micro aerial vehicle (MAV).
Design/methodology/approach
Six different wings are fabricated for the MAV configuration, which is restricted to the size of 15 cm length and width; all wings have different surface area and constant span length of 6 cm. The force is being measured with the help of a force-sensing resistor (FSR), and the coefficients of lift were calculated and compared.
Findings
This study shows that the wing “Tipula sp” has better value of lift than other insect wings, except for the negative angle of attacks. The wing “Aeshna multicolor” gives the better values of lift in negative angles of attack.
Practical implications
This paper lays the foundation for the development of flapping MAVs with the insect wings. This type of wing can be used for spying purpose in the military zone and also can be used to survey remote and dangerous places where humans cannot enter.
Originality/value
This paper covers all basic insect wing configurations of different species with exact mimics of the veins. As the experimental investigation was carried for different angle of attacks, velocities and flapping frequencies, this paper can be used as reference for future flapping wing MAV developers.
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Mostafa Arasteh, Yegane Azargoon and M.H. Djavareshkian
Ground effect is one of the important factors in the enhancement of wing aerodynamic performance. This study aims to investigate the aerodynamic forces and performance of a…
Abstract
Purpose
Ground effect is one of the important factors in the enhancement of wing aerodynamic performance. This study aims to investigate the aerodynamic forces and performance of a flapping wing with the bending deflection angel under the ground effect.
Design/methodology/approach
In this study, the wing and flapping mechanism were designed and manufactured based on the seagull flight and then assembled. It is worth noting that this mechanism is capable of wing bending in the upstroke flight as big birds. Finally, the model was examined at bending deflection angles of 0° and 107° and different distances from the surface, flapping frequencies and velocities in forward flight in a wind tunnel.
Findings
The results revealed that the aerodynamic performance of flapping wings in forward flight improved due to the ground effect. The effect of the bending deflection mechanism on lift generation was escalated when the flapping wing was close to the surface, where the maximum power loading occurred.
Practical implications
Flapping wings have many different applications, such as maintenance, traffic control, pollution monitoring, meteorology and high-risk operations. Unlike fixed-wing micro aerial vehicles, flapping wings are capable of operating in very-low Reynolds-number flow regimes. On the other hand, ground effect poses positive impacts on the provision of aerodynamic forces in the take-off process.
Originality/value
Bending deflection in the flapping motion and ground effect are two influential factors in the enhancement of the aerodynamic performance of flapping wings. The combined effects of these two factors have not been studied yet, which is addressed in this study.
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Although being fired up about changes such as firm expansion, chief executive officers (CEOs) have a hard time with changes that involve divesting businesses or downsizing…
Abstract
Purpose
Although being fired up about changes such as firm expansion, chief executive officers (CEOs) have a hard time with changes that involve divesting businesses or downsizing operations. This study aims to examine how a particular psychological process – regulatory focus – serves as a managerial exit barrier in the context of store closings in the US retail industry. This study also examines how a particular corporate governance mechanism, the board of directors, moderates the relationship between CEO regulatory focus and divestment activity.
Design/methodology/approach
This study content-analyzed letters to shareholders to measure the regulatory focus of retail CEOs and used negative binomial regression to test the effect of the CEO’s regulatory focus and board independence on store closure activity.
Findings
The two motivation orientations – promotion and prevention – focuses have distinct effects on store closure decisions. As predicted, promotion-focused CEOs, who value attainment and growth, resist “pulling the plug.” Conversely, prevention-focused CEOs, who are more sensitive to losses, are more inclined to close stores. Independent boards decrease the CEOs’ resistance to “pull the plug” only when necessary, which is the case when CEOs have less vigilant tendencies.
Research limitations/implications
This study contributes to the strategy and marketing literature. It examines an individual-level antecedent of store closure decisions and responds to the call for research on the effect of regulatory focus on divestment decisions.
Practical implications
Leaders themselves can be a source of resistance to change. The findings suggest the importance of boards hiring CEOs psychologically aligned with the firms’ strategic priorities. Promotion-focused CEOs may be a better fit for companies engaged in growth and acquisition. By contrast, prevention-focused CEOs may be a better fit for firms involved in retrenchment and restructuring. Independent boards still have the power to influence CEO decisions in the case of a misfit, as the findings suggest.
Originality/value
This study examines divestment decisions during the “retail apocalypse” and provides empirical evidence for the existence of managerial exit barriers, first introduced by Michael Porter.
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Alexander Garrido, Fabián Pongutá and Oscar Yecid Buitrago
The aim of this research is to improve the responsiveness of the healthcare network of a large city to a major earthquake, by applying a combined methodology to reduce human…
Abstract
Purpose
The aim of this research is to improve the responsiveness of the healthcare network of a large city to a major earthquake, by applying a combined methodology to reduce human suffering and death.
Design/methodology/approach
Scenario analysis, a non-linear programming (NLP) model, and the analytical network process are sequentially applied to find the “best location pattern”.
Findings
When considering the occurrence of major earthquakes in cities with high population density, as a rule of thumb, the location of healthcare facilities should prioritize areas characteristically overcrowded and/or that were built based on poor standards of seismic resistance.
Research limitations/implications
The proposed research design does not include a cost criterion in the set of decision variables involved. Furthermore, the results derived from the NLP-model are restricted by the input simulation data.
Practical implications
The performance of the “best location pattern” is compared with the current location of healthcare facilities in terms of their distances to the affected zones. Metropolis areas worldwide with similar conditions to the city under consideration could be benefited from applying the general methodology for relocation of healthcare facilities described in this research.
Originality/value
This research implements a diverse combination of methodologies to examine the problem of relocating of healthcare facilities in a large city in the wake of an assumed earthquake. In addition, to the best of authors' knowledge, this is the first study of its kind that proposes improvements in the responsiveness of the healthcare facilities' network in the city in question.