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Dr. Mostafa Nabawy
Department of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M1 3BB, UK

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0 Aerodynamics
0 Biomechanics
0 Biomimetics
0 Fluid Dynamics
0 Microsystems

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Aerodynamics
Fluid Dynamics
piezoelectric actuators
Piezoelectric Harvesters

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Journal article
Published: 24 August 2021 in Remote Sensing
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The accuracy of stockpile estimations is of immense criticality to process optimisation and overall financial decision making within manufacturing operations. Despite well-established correlations between inventory management and profitability, safe deployment of stockpile measurement and inspection activities remain challenging and labour-intensive. This is perhaps owing to a combination of size, shape irregularity as well as the health hazards of cement manufacturing raw materials and products. Through a combination of simulations and real-life assessment within a fully integrated cement plant, this study explores the potential of drones to safely enhance the accuracy of stockpile volume estimations. Different types of LiDAR sensors in combination with different flight trajectory options were fully assessed through simulation whilst mapping representative stockpiles placed in both open and fully confined areas. During the real-life assessment, a drone was equipped with GPS for localisation, in addition to a 1D LiDAR and a barometer for stockpile height estimation. The usefulness of the proposed approach was established based on mapping of a pile with unknown volume in an open area, as well as a pile with known volume within a semi-confined area. Visual inspection of the generated stockpile surface showed strong correlations with the actual pile within the open area, and the volume of the pile in the semi-confined area was accurately measured. Finally, a comparative analysis of cost and complexity of the proposed solution to several existing initiatives revealed its proficiency as a low-cost robotic system within confined spaces whereby visibility, air quality, humidity, and high temperature are unfavourable.

ACS Style

Ahmad Alsayed; Akilu Yunusa-Kaltungo; Mark K. Quinn; Farshad Arvin; Mostafa R. A. Nabawy. Drone-Assisted Confined Space Inspection and Stockpile Volume Estimation. Remote Sensing 2021, 13, 3356 .

AMA Style

Ahmad Alsayed, Akilu Yunusa-Kaltungo, Mark K. Quinn, Farshad Arvin, Mostafa R. A. Nabawy. Drone-Assisted Confined Space Inspection and Stockpile Volume Estimation. Remote Sensing. 2021; 13 (17):3356.

Chicago/Turabian Style

Ahmad Alsayed; Akilu Yunusa-Kaltungo; Mark K. Quinn; Farshad Arvin; Mostafa R. A. Nabawy. 2021. "Drone-Assisted Confined Space Inspection and Stockpile Volume Estimation." Remote Sensing 13, no. 17: 3356.

Conference paper
Published: 11 February 2021 in Notes on Numerical Fluid Mechanics and Multidisciplinary Design
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This paper aims to develop a novel concept for energy harvesting via flexible inverted flags combining photovoltaic cells with piezoelectric material. Using technology currently available off-the-shelf, we have built dual piezo-solar harvesters made of polyvinylidene fluoride (PVDF) piezoelectric elements combined with mini solar panels of different sizes. Dynamics and power generation experimental measurements were collected for the flags when simultaneously subjected to both wind and light sources. This allowed for an improved understanding of the effect of adding the solar panels on the motion and power generation characteristics. Additionally, flapping amplitude and frequency responses are confirmed using a lattice Boltzmann-immersed boundary numerical method. Results indicate a significant improvement in the capability of energy harvesting compared to isolated single piezoelectric devices. As such, we anticipate a significant impact of dual piezo-solar energy harvesting devices on a range of applications where remote power generation is needed.

ACS Style

Mostafa Nabawy; Jorge Silva-Leon; Joseph O'Connor; Andrew Kennaugh; Andrea Cioncolini; Alistair Revell. Simultaneous Energy Harvesting Using Dual Piezo-Solar Devices. Notes on Numerical Fluid Mechanics and Multidisciplinary Design 2021, 267 -278.

AMA Style

Mostafa Nabawy, Jorge Silva-Leon, Joseph O'Connor, Andrew Kennaugh, Andrea Cioncolini, Alistair Revell. Simultaneous Energy Harvesting Using Dual Piezo-Solar Devices. Notes on Numerical Fluid Mechanics and Multidisciplinary Design. 2021; ():267-278.

Chicago/Turabian Style

Mostafa Nabawy; Jorge Silva-Leon; Joseph O'Connor; Andrew Kennaugh; Andrea Cioncolini; Alistair Revell. 2021. "Simultaneous Energy Harvesting Using Dual Piezo-Solar Devices." Notes on Numerical Fluid Mechanics and Multidisciplinary Design , no. : 267-278.

Journal article
Published: 03 January 2021 in Energies
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In the present paper, we report a systematic investigation of planform geometry and excitation level effects on the dynamics and power generation characteristics of polyvinylidene difluoride (PVDF)-based cantilevered vibration energy harvesters. Piezoelectric vibration energy harvesters provide a promising energy harvesting solution for widespread use of wireless sensors in remote locations. Highly flexible PVDF polymers offer resonant frequencies at suitable range for harvesting mechanical energy within low-frequency applications, though information on the efficient sizing of these devices is currently limited. We test the response of a set of eight harvesters to typical vibration sources excitation levels in the range 0.2–0.6 g. This set comprises four widths and two lengths, incrementing each time by a factor of two. The selected range of dimensions is sufficient to identify optimal power output versus width for both lengths tested. This optimal width value depends on excitation amplitude in such a way that narrower harvesters are more suited for small excitations, whereas wider harvesters perform better upon experiencing large excitations. Non-linear effects present in longer harvesters are demonstrated to significantly reduce performance, which motivates the selection of planform dimensions inside the linear range. Finally, we explore the correlation of performance with various geometric quantities in order to inform future design studies and highlight the value of using the second moment of planform area to measure harvester efficiency in terms of power density. This points towards the use of harvesters with non-rectangular planform area for optimal performance.

ACS Style

Jie Wang; Mostafa R. A. Nabawy; Andrea Cioncolini; Alistair Revell; Samuel Weigert. Planform Geometry and Excitation Effects of PVDF-Based Vibration Energy Harvesters. Energies 2021, 14, 211 .

AMA Style

Jie Wang, Mostafa R. A. Nabawy, Andrea Cioncolini, Alistair Revell, Samuel Weigert. Planform Geometry and Excitation Effects of PVDF-Based Vibration Energy Harvesters. Energies. 2021; 14 (1):211.

Chicago/Turabian Style

Jie Wang; Mostafa R. A. Nabawy; Andrea Cioncolini; Alistair Revell; Samuel Weigert. 2021. "Planform Geometry and Excitation Effects of PVDF-Based Vibration Energy Harvesters." Energies 14, no. 1: 211.

Journal article
Published: 19 October 2020 in Aerospace
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Tailless aircraft without vertical stabilisers typically use drag effectors in the form of spoilers or split flaps to generate control moments in yaw. This paper introduces a novel control allocation method by which full three-axis control authority can be achieved by the use of conventional lift effectors only, which reduces system complexity and control deflection required to achieve a given yawing moment. The proposed method is based on synthesis of control allocation modes that generate asymmetric profile and lift induced drag whilst maintaining the lift, pitching moment and rolling moment at the trim state. The method uses low order models for aerodynamic behaviour characterisation based on thin aerofoil theory, lifting surface methodology and ESDU datasheets and is applied to trapezoidal wings of varying sweep and taper. Control allocation modes are derived using the zero-sets of surrogate models for the characterised aerodynamic behaviours. Results are presented in the form of control allocations for a range of trimmed sideslip angles up to 10 degrees optimised for either maximum aerodynamic efficiency (minimum drag for a specific yawing moment) or minimum aggregate control deflection (as a surrogate observability metric). Outcomes for the two optimisation objectives are correlated in that minimum deflection solutions are always consistent with efficient ones. A configuration with conventional drag effector is used as a reference baseline. It is shown that, through appropriate allocation of lift based control effectors, a given yawing moment can be produced with up to a factor of eight less aggregate control deflection and up to 30% less overall drag compared to use of a conventional drag effector.

ACS Style

Thomas R. Shearwood; Mostafa R. A. Nabawy; William J. Crowther; Clyde Warsop. A Novel Control Allocation Method for Yaw Control of Tailless Aircraft. Aerospace 2020, 7, 150 .

AMA Style

Thomas R. Shearwood, Mostafa R. A. Nabawy, William J. Crowther, Clyde Warsop. A Novel Control Allocation Method for Yaw Control of Tailless Aircraft. Aerospace. 2020; 7 (10):150.

Chicago/Turabian Style

Thomas R. Shearwood; Mostafa R. A. Nabawy; William J. Crowther; Clyde Warsop. 2020. "A Novel Control Allocation Method for Yaw Control of Tailless Aircraft." Aerospace 7, no. 10: 150.

Accepted manuscript
Published: 13 August 2020 in Engineering Research Express
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Piezoelectric energy harvesters represent a viable and well-proven solution to convert ambient vibrations into useful electric power within a number of modern life applications. Whilst a large amount of studies has focused on improving power output from these devices, relatively little research has been directed to investigate how these devices degrade over time and the effect this has on long-term power generation. This paper, therefore, aims to experimentally investigate how piezoelectric vibration energy harvesters degrade during long-term operation in realistic harvesting conditions. The harvesters tested are unimorph cantilevers based on three of the most commonly used piezoelectric options: polyvinylidene fluoride (PVDF), Macro Fiber Composite (MFC), and Quick Pack (QP). Testing was carried out under single-frequency excitation (1040 Hz) of 1g amplitude for three million vibration cycles. Our results show that the natural frequency and the optimum load resistance of the harvesters may vary during prolonged operation. Importantly, a larger cumulative variation in natural frequency and optimum load resistance yields a larger variation in power output, thereby linking the variation in power to the variation of the mechanical and/or electrical properties of the harvesters. Comparing the average power values over the testing period we found that increasing the tip mass does not necessarily improve the average power output, suggesting that a larger tip mass may exacerbate the degradation of the mechanical and/or electrical properties of the harvester. This was particularly evident for the stiffest QP harvesters which showed the highest signs of power degradation; nevertheless, QP harvesters still managed to demonstrate the highest power density values. When cost consideration is taken into account in the assessment, PVDF harvesters managed to demonstrate the highest power density to cost ratio.

ACS Style

Jacob Hirst; Ms Jie Wang; Mostafa R A Nabawy; Andrea Cioncolini. Long-term power degradation testing of piezoelectric vibration energy harvesters for low-frequency applications. Engineering Research Express 2020, 2, 035026 .

AMA Style

Jacob Hirst, Ms Jie Wang, Mostafa R A Nabawy, Andrea Cioncolini. Long-term power degradation testing of piezoelectric vibration energy harvesters for low-frequency applications. Engineering Research Express. 2020; 2 (3):035026.

Chicago/Turabian Style

Jacob Hirst; Ms Jie Wang; Mostafa R A Nabawy; Andrea Cioncolini. 2020. "Long-term power degradation testing of piezoelectric vibration energy harvesters for low-frequency applications." Engineering Research Express 2, no. 3: 035026.

Communication
Published: 18 June 2020 in Fluids
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Yellow rust spores currently blight commercial and domestic wheat production in areas of East Africa such as Ethiopia. Yellow rust is a hazard to crops which appears asymptomatic for a time, but inevitably causes significant losses in yield once symptoms of infection manifest themselves to the point where they can be readily observed by the naked eye. Regionally recurrent losses of up to 5% are common and reach as high as 25% in rare cases. Historically, spore sampling has been undertaken by large, cumbersome devices that require heavy power supplies and significant expertise to reliably operate. Moreover, tools for the design and development of such devices are currently limited. This paper, therefore, proposes design and testing processes to develop a spore sampling device that is compact, passive (requires no power to operate), and can better direct spores onto a biomimetic sensor platform enhancing the capture and detection of pathogens. This represents a novel design context for fluidic devices. Performance of the device has been simulated using Lagrangian particle tracking embedded into computational fluid dynamics (CFD) simulations, demonstrating significant improvements across a range of spore Stokes numbers. Experimental validation of numerical simulations was performed using wind tunnel testing and practical performance such as weathervaning was demonstrated. Results show that that the developed sampler is capable of enhancing the probability of yellow rust spores interacting with an internal sensor by a factor of between 20 and 25; demonstrating the effectiveness of the developed design.

ACS Style

James Blackall; Jie Wang; Mostafa R. A. Nabawy; Mark K. Quinn; Bruce D. Grieve. Development of a Passive Spore Sampler for Capture Enhancement of Airborne Crop Pathogens. Fluids 2020, 5, 97 .

AMA Style

James Blackall, Jie Wang, Mostafa R. A. Nabawy, Mark K. Quinn, Bruce D. Grieve. Development of a Passive Spore Sampler for Capture Enhancement of Airborne Crop Pathogens. Fluids. 2020; 5 (2):97.

Chicago/Turabian Style

James Blackall; Jie Wang; Mostafa R. A. Nabawy; Mark K. Quinn; Bruce D. Grieve. 2020. "Development of a Passive Spore Sampler for Capture Enhancement of Airborne Crop Pathogens." Fluids 5, no. 2: 97.

Journal article
Published: 09 October 2019 in Energies
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Tip masses are used in cantilevered piezoelectric energy harvesters to shift device resonance towards the required frequency for harvesting and to improve the electric power generation. Tip masses are typically in the form of concentrated passive weights. The aim of this study is to assess the inclusion of solar panels as active tip masses on the dynamics and power generation performance of cantilevered PVDF (polyvinylidene fluoride)-based vibration energy harvesters. Four different harvester geometries with and without solar panels are realized using off-the-shelf components. Our experimental results show that the flexible solar panels considered in this study are capable of reducing resonance frequency by up to 14% and increasing the PVDF power generated by up to 54%. Two analytical models are developed to investigate this concept; employing both an equivalent concentrated tip mass to represent the case of flexible solar panels and a distributed tip mass to represent rigid panels. Good prediction agreement with experimental results is achieved with an average error in peak power of less than 5% for the cases considered. The models are also used to identify optimum tip mass configurations. For the flexible solar panel model, it is found that the highest PVDF power output is produced when the length of solar panels is two thirds of the total length. On the other hand, results from the rigid solar panel model show that the optimum length of solar panels increases with the relative tip mass ratio, approaching an asymptotic value of half of the total length as the relative tip mass ratio increases significantly.

ACS Style

Jie Wang; Mostafa R. A. Nabawy; Andrea Cioncolini; Alistair Revell; Wang. Solar Panels as Tip Masses in Low Frequency Vibration Harvesters. Energies 2019, 12, 3815 .

AMA Style

Jie Wang, Mostafa R. A. Nabawy, Andrea Cioncolini, Alistair Revell, Wang. Solar Panels as Tip Masses in Low Frequency Vibration Harvesters. Energies. 2019; 12 (20):3815.

Chicago/Turabian Style

Jie Wang; Mostafa R. A. Nabawy; Andrea Cioncolini; Alistair Revell; Wang. 2019. "Solar Panels as Tip Masses in Low Frequency Vibration Harvesters." Energies 12, no. 20: 3815.

Conference paper
Published: 14 June 2019 in AIAA Aviation 2019 Forum
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ACS Style

Thomas R. Shearwood; Mostafa R. Nabawy; William J. Crowther; Clyde Warsop. Directional Control of Finless Flying Wing Vehicles - An Assessment of Opportunities for Fluidic Actuation. AIAA Aviation 2019 Forum 2019, 1 .

AMA Style

Thomas R. Shearwood, Mostafa R. Nabawy, William J. Crowther, Clyde Warsop. Directional Control of Finless Flying Wing Vehicles - An Assessment of Opportunities for Fluidic Actuation. AIAA Aviation 2019 Forum. 2019; ():1.

Chicago/Turabian Style

Thomas R. Shearwood; Mostafa R. Nabawy; William J. Crowther; Clyde Warsop. 2019. "Directional Control of Finless Flying Wing Vehicles - An Assessment of Opportunities for Fluidic Actuation." AIAA Aviation 2019 Forum , no. : 1.

Journal article
Published: 11 May 2019 in Fluids
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This paper presents results from experiments and simplified numerical simulations on the flow-induced dynamics and power generation of inverted flags that combine flexible piezoelectric strips with photovoltaic cells to simultaneously harvest kinetic wind energy and solar radiant energy. Experiments were conducted in a wind tunnel under controlled wind excitation and light exposure, focusing in particular on the dynamics and power generation of the inverted flag harvester. Numerical simulations were carried out using a lattice-Boltzmann fluid solver coupled with a finite element structural solver via the immersed-boundary method, focusing in particular on minimizing the simulation run time. The power generated during the tests shows that the proposed inverted flag harvester is a promising concept, capable of producing enough power (on the order of 1 mW) to supply low-power electronic devices in a range of applications where distributed power generation is needed. Notwithstanding key simplifications implemented in the numerical model to achieve a fast execution, simulations and measurements are in good agreement, confirming that the lattice-Boltzmann method is a viable and time-effective alternative to classic Navier–Stokes-based solvers when dealing with strongly coupled fluid–structure interaction problems characterized by large structural displacements.

ACS Style

Andrea Cioncolini; Mostafa R.A. Nabawy; Jorge Silva-Leon; Joseph O’Connor; Alistair Revell. An Experimental and Computational Study on Inverted Flag Dynamics for Simultaneous Wind–Solar Energy Harvesting. Fluids 2019, 4, 87 .

AMA Style

Andrea Cioncolini, Mostafa R.A. Nabawy, Jorge Silva-Leon, Joseph O’Connor, Alistair Revell. An Experimental and Computational Study on Inverted Flag Dynamics for Simultaneous Wind–Solar Energy Harvesting. Fluids. 2019; 4 (2):87.

Chicago/Turabian Style

Andrea Cioncolini; Mostafa R.A. Nabawy; Jorge Silva-Leon; Joseph O’Connor; Alistair Revell. 2019. "An Experimental and Computational Study on Inverted Flag Dynamics for Simultaneous Wind–Solar Energy Harvesting." Fluids 4, no. 2: 87.

Journal article
Published: 08 February 2019 in Applied Energy
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This paper presents a novel wind/solar energy-harvesting device based on the inverted flag concept that combines flexible piezoelectric strips with flexible photovoltaic cells to simultaneously harvest both wind and solar energy. Three inverted flags built using off-the-shelf components were experimentally investigated under controlled wind and illumination conditions to analyse their dynamics and electrical power generation capability. Our results provide an improved understanding of the dynamics of inverted flags that incorporate flexible piezoelectric strips and flexible solar panels, and indicate that the piezoelectric strips mainly increase the damping of the flags, while the solar panels act as an added mass. The power measurements show that the wind/solar energy-harvesting device proposed here is a viable concept that is capable of generating up to 3–4 mW of total power, enough to meet the demand of remote sensors and small-scale portable electronics, for wind speeds varying from 0 m/s (calm) to about 26 m/s (storm/whole gale) and 1.8 kLux constant light exposure, suggesting a rather diversified range of potential practical applications.

ACS Style

Jorge Silva-Leon; Andrea Cioncolini; Mostafa R.A. Nabawy; Alistair Revell; Andrew Kennaugh. Simultaneous wind and solar energy harvesting with inverted flags. Applied Energy 2019, 239, 846 -858.

AMA Style

Jorge Silva-Leon, Andrea Cioncolini, Mostafa R.A. Nabawy, Alistair Revell, Andrew Kennaugh. Simultaneous wind and solar energy harvesting with inverted flags. Applied Energy. 2019; 239 ():846-858.

Chicago/Turabian Style

Jorge Silva-Leon; Andrea Cioncolini; Mostafa R.A. Nabawy; Alistair Revell; Andrew Kennaugh. 2019. "Simultaneous wind and solar energy harvesting with inverted flags." Applied Energy 239, no. : 846-858.

Journal article
Published: 08 May 2018 in Scientific Reports
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Jumping spiders are proficient jumpers that use jumps in a variety of behavioural contexts. We use high speed, high resolution video to measure the kinematics of a single regal jumping spider for a total of 15 different tasks based on a horizontal gap of 2-5 body lengths and vertical gap of +/-2 body lengths. For short range jumps, we show that low angled trajectories are used that minimise flight time. For longer jumps, take-off angles are steeper and closer to the optimum for minimum energy cost of transport. Comparison of jump performance against other arthropods shows that Phidippus regius is firmly in the group of animals that use dynamic muscle contraction for actuation as opposed to a stored energy catapult system. We find that the jump power requirements can be met from the estimated mass of leg muscle; hydraulic augmentation may be present but appears not to be energetically essential.

ACS Style

Mostafa R. A. Nabawy; Girupakaran Sivalingam; Russell J. Garwood; William J. Crowther; William I. Sellers. Energy and time optimal trajectories in exploratory jumps of the spider Phidippus regius. Scientific Reports 2018, 8, 7142 .

AMA Style

Mostafa R. A. Nabawy, Girupakaran Sivalingam, Russell J. Garwood, William J. Crowther, William I. Sellers. Energy and time optimal trajectories in exploratory jumps of the spider Phidippus regius. Scientific Reports. 2018; 8 (1):7142.

Chicago/Turabian Style

Mostafa R. A. Nabawy; Girupakaran Sivalingam; Russell J. Garwood; William J. Crowther; William I. Sellers. 2018. "Energy and time optimal trajectories in exploratory jumps of the spider Phidippus regius." Scientific Reports 8, no. 1: 7142.

Proceedings article
Published: 07 January 2018 in 2018 AIAA Aerospace Sciences Meeting
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ACS Style

Ahmed M. Mohamed; William Crowther; Mostafa Nabawy. Development of Valveless Resonant Micropumps for Liquid Applications. 2018 AIAA Aerospace Sciences Meeting 2018, 1 .

AMA Style

Ahmed M. Mohamed, William Crowther, Mostafa Nabawy. Development of Valveless Resonant Micropumps for Liquid Applications. 2018 AIAA Aerospace Sciences Meeting. 2018; ():1.

Chicago/Turabian Style

Ahmed M. Mohamed; William Crowther; Mostafa Nabawy. 2018. "Development of Valveless Resonant Micropumps for Liquid Applications." 2018 AIAA Aerospace Sciences Meeting , no. : 1.

Review article
Published: 26 July 2017 in Journal of The Royal Society Interface
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The presence of a stable leading edge vortex (LEV) on steadily revolving wings increases the maximum lift coefficient that can be generated from the wing and its role is important to understanding natural flyers and flapping wing vehicles. In this paper, the role of LEV in lift augmentation is discussed under two hypotheses referred to as ‘additional lift' and ‘absence of stall’. The ‘additional lift' hypothesis represents the traditional view. It presumes that an additional suction/circulation from the LEV increases the lift above that of a potential flow solution. This behaviour may be represented through either the ‘Polhamus leading edge suction' model or the so-called ‘trapped vortex' model. The ‘absence of stall' hypothesis is a more recent contender that presumes that the LEV prevents stall at high angles of attack where flow separation would normally occur. This behaviour is represented through the so-called ‘normal force' model. We show that all three models can be written in the form of the same potential flow kernel with modifiers to account for the presence of a LEV. The modelling is built on previous work on quasi-steady models for hovering wings such that model parameters are determined from first principles, which allows a fair comparison between the models themselves, and the models and experimental data. We show that the two models which directly include the LEV as a lift generating component are built on a physical picture that does not represent the available experimental data. The simpler ‘normal force' model, which does not explicitly model the LEV, performs best against data in the literature. We conclude that under steady conditions the LEV as an ‘absence of stall’ model/mechanism is the most satisfying explanation for observed aerodynamic behaviour.

ACS Style

Mostafa R. A. Nabawy; William J. Crowther. The role of the leading edge vortex in lift augmentation of steadily revolving wings: a change in perspective. Journal of The Royal Society Interface 2017, 14, 20170159 .

AMA Style

Mostafa R. A. Nabawy, William J. Crowther. The role of the leading edge vortex in lift augmentation of steadily revolving wings: a change in perspective. Journal of The Royal Society Interface. 2017; 14 (132):20170159.

Chicago/Turabian Style

Mostafa R. A. Nabawy; William J. Crowther. 2017. "The role of the leading edge vortex in lift augmentation of steadily revolving wings: a change in perspective." Journal of The Royal Society Interface 14, no. 132: 20170159.

Journal article
Published: 01 October 2016 in Journal of Theoretical Biology
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Theoretical analysis is used to identify the optimum wing planform of a flapping/revolving wing in hover. This solution is of interest as a benchmark to which hovering wing geometries driven by broader multidisciplinary evolutionary or engineering constraints can be compared. Furthermore, useful insights into the aerodynamic performance of untwisted hovering wings are delivered. It is shown that profile power is minimised by using an untwisted elliptical planform whereas induced power is minimised by a more highly tapered planform similar to that of a hummingbird.

ACS Style

Mostafa R.A. Nabawy; William J. Crowther. Optimum hovering wing planform. Journal of Theoretical Biology 2016, 406, 187 -191.

AMA Style

Mostafa R.A. Nabawy, William J. Crowther. Optimum hovering wing planform. Journal of Theoretical Biology. 2016; 406 ():187-191.

Chicago/Turabian Style

Mostafa R.A. Nabawy; William J. Crowther. 2016. "Optimum hovering wing planform." Journal of Theoretical Biology 406, no. : 187-191.

Journal article
Published: 20 January 2016 in Micromachines
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Electromechanical coupling defines the ratio of electrical and mechanical energy exchanged during a flexure cycle of a piezoelectric actuator. This paper presents an analysis of the dynamic electromechanical coupling factor (dynamic EMCF) for cantilever based piezoelectric actuators and provides for the first time explicit expressions for calculation of dynamic EMCF based on arrangement of passive and active layers, layer geometry, and active and passive materials selection. Three main cantilever layer configurations are considered: unimorph, dual layer bimorph and triple layer bimorph. The actuator is modeled using standard constitutive dynamic equations that relate deflection and charge to force and voltage. A mode shape formulation is used for the cantilever dynamics that allows the generalized mass to be the actual mass at the first resonant frequency, removing the need for numerical integration in the design process. Results are presented in the form of physical insight from the model structure and also numerical evaluations of the model to provide trends in dynamic EMCF with actuator design parameters. For given material properties of the active and passive layers and given system overall damping ratio, the triple layer bimorph topology is the best in terms of theoretically achievable dynamic EMCF, followed by the dual layer bimorph. For a damping ratio of 0.035, the dynamic EMCF for an example dual layer bimorph configuration is 9% better than for a unimorph configuration. For configurations with a passive layer, the ratio of thicknesses for the passive and active layers is the primary geometric design variable. Choice of passive layer stiffness (Young’s modulus) relative to the stiffness of the material in the active layer is an important materials related design choice. For unimorph configurations, it is beneficial to use the highest stiffness possible passive material, whereas for triple layer bimorph configurations, the passive material should have a low stiffness. In all cases, increasing the transverse electromechanical coupling coefficient of the active material improves the dynamic EMCF.

ACS Style

Mostafa R. A. Nabawy; William J. Crowther. Dynamic Electromechanical Coupling of Piezoelectric Bending Actuators. Micromachines 2016, 7, 12 .

AMA Style

Mostafa R. A. Nabawy, William J. Crowther. Dynamic Electromechanical Coupling of Piezoelectric Bending Actuators. Micromachines. 2016; 7 (1):12.

Chicago/Turabian Style

Mostafa R. A. Nabawy; William J. Crowther. 2016. "Dynamic Electromechanical Coupling of Piezoelectric Bending Actuators." Micromachines 7, no. 1: 12.

Research article
Published: 07 August 2015 in PLOS ONE
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A novel lifting line formulation is presented for the quasi-steady aerodynamic evaluation of insect-like wings in hovering flight. The approach allows accurate estimation of aerodynamic forces from geometry and kinematic information alone and provides for the first time quantitative information on the relative contribution of induced and profile drag associated with lift production for insect-like wings in hover. The main adaptation to the existing lifting line theory is the use of an equivalent angle of attack, which enables capture of the steady non-linear aerodynamics at high angles of attack. A simple methodology to include non-ideal induced effects due to wake periodicity and effective actuator disc area within the lifting line theory is included in the model. Low Reynolds number effects as well as the edge velocity correction required to account for different wing planform shapes are incorporated through appropriate modification of the wing section lift curve slope. The model has been successfully validated against measurements from revolving wing experiments and high order computational fluid dynamics simulations. Model predicted mean lift to weight ratio results have an average error of 4% compared to values from computational fluid dynamics for eight different insect cases. Application of an unmodified linear lifting line approach leads on average to a 60% overestimation in the mean lift force required for weight support, with most of the discrepancy due to use of linear aerodynamics. It is shown that on average for the eight insects considered, the induced drag contributes 22% of the total drag based on the mean cycle values and 29% of the total drag based on the mid half-stroke values.

ACS Style

Mostafa R. A. Nabawy; William Crowther. A Quasi-Steady Lifting Line Theory for Insect-Like Hovering Flight. PLOS ONE 2015, 10, e0134972 .

AMA Style

Mostafa R. A. Nabawy, William Crowther. A Quasi-Steady Lifting Line Theory for Insect-Like Hovering Flight. PLOS ONE. 2015; 10 (8):e0134972.

Chicago/Turabian Style

Mostafa R. A. Nabawy; William Crowther. 2015. "A Quasi-Steady Lifting Line Theory for Insect-Like Hovering Flight." PLOS ONE 10, no. 8: e0134972.

Journal article
Published: 01 August 2015 in Bioinspiration & Biomimetics
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Hovering flight for flapping wing vehicles requires rapid and relatively complex reciprocating movement of a wing relative to a stationary surrounding fluid. This note develops a compact analytical aero-kinematic model that can be used for optimization of flapping wing kinematics against aerodynamic criteria of effectiveness (maximum lift) and efficiency (minimum power for a given amount of lift). It can also be used to make predictions of required flapping frequency for a given geometry and basic aerodynamic parameters. The kinematic treatment is based on a consolidation of an existing formulation that allows explicit derivation of flapping velocity for complex motions whereas the aerodynamic model is based on existing quasi-steady analysis. The combined aero-kinematic model provides novel explicit analytical expressions for both lift and power of a hovering wing in a compact form that enables exploration of a rich kinematic design space. Good agreement is found between model predictions of flapping frequency and observed results for a number of insects and optimal hovering kinematics identified using the model are consistent with results from studies using higher order computational models. For efficient flight, the flapping angle should vary using a triangular profile in time leading to a constant velocity flapping motion, whereas for maximum effectiveness the shape of variation should be sinusoidal. For both cases the wing pitching motion should be rectangular such that pitch change at stroke reversal is as rapid as possible.

ACS Style

Mostafa Nabawy; William Crowther. Aero-optimum hovering kinematics. Bioinspiration & Biomimetics 2015, 10, 044002 .

AMA Style

Mostafa Nabawy, William Crowther. Aero-optimum hovering kinematics. Bioinspiration & Biomimetics. 2015; 10 (4):044002.

Chicago/Turabian Style

Mostafa Nabawy; William Crowther. 2015. "Aero-optimum hovering kinematics." Bioinspiration & Biomimetics 10, no. 4: 044002.

Research article
Published: 14 October 2014 in Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering
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Piezoelectric bending actuators utilise the inverse piezoelectric effect to convert input electric energy to useful mechanical work. A comprehensive analytical model of the dynamic electromechanical behaviour of a unimorph piezoelectric actuator has been developed and successfully validated against experimental data. The model provides a mapping between force, displacement, voltage and charge. Damping is modelled using experimental data. Experimental validation is based on measurement of mode shape and frequency response of a series of unimorph beams of varying length but of the same thickness and material. The experimental frequency response is weakly nonlinear with excitation voltage, with a reduction in natural frequency and increase in damping with increasing excitation amplitude. An expression for the electromechanical coupling factor has been extracted from the analytical model and is used as the objective for parametric design studies. The design parameters are thickness and Young’s modulus ratios of the elastic and piezoceramic layers, and the piezoelectric constant k31. The operational design point is defined by the damping ratio. It is found that the relative variation in the electromechanical coupling factor with the design parameters for dynamic operation is similar to static operation; however, for light damping, the magnitude of the peak electromechanical coupling factor will typically be an order of magnitude greater than that of static operation. For the actuator configuration considered in this study, it is shown that the absolute variation in electromechanical coupling factor with thickness ratio for dynamic operation is same as that for static operation when the damping ratio is 0.44.

ACS Style

Mostafa R A Nabawy; Ben Parslew; William J Crowther. Dynamic performance of unimorph piezoelectric bending actuators. Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering 2014, 229, 118 -129.

AMA Style

Mostafa R A Nabawy, Ben Parslew, William J Crowther. Dynamic performance of unimorph piezoelectric bending actuators. Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering. 2014; 229 (2):118-129.

Chicago/Turabian Style

Mostafa R A Nabawy; Ben Parslew; William J Crowther. 2014. "Dynamic performance of unimorph piezoelectric bending actuators." Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering 229, no. 2: 118-129.

Conference paper
Published: 13 June 2014 in 32nd AIAA Applied Aerodynamics Conference
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ACS Style

Mostafa R. Nabawy; William J. Crowther. Is Flapping Flight Aerodynamically Efficient? 32nd AIAA Applied Aerodynamics Conference 2014, 1 .

AMA Style

Mostafa R. Nabawy, William J. Crowther. Is Flapping Flight Aerodynamically Efficient? 32nd AIAA Applied Aerodynamics Conference. 2014; ():1.

Chicago/Turabian Style

Mostafa R. Nabawy; William J. Crowther. 2014. "Is Flapping Flight Aerodynamically Efficient?" 32nd AIAA Applied Aerodynamics Conference , no. : 1.

Journal article
Published: 06 May 2014 in Journal of The Royal Society Interface
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This paper introduces a generic, transparent and compact model for the evaluation of the aerodynamic performance of insect-like flapping wings in hovering flight. The model is generic in that it can be applied to wings of arbitrary morphology and kinematics without the use of experimental data, is transparent in that the aerodynamic components of the model are linked directly to morphology and kinematics via physical relationships and is compact in the sense that it can be efficiently evaluated for use within a design optimization environment. An important aspect of the model is the method by which translational force coefficients for the aerodynamic model are obtained from first principles; however important insights are also provided for the morphological and kinematic treatments that improve the clarity and efficiency of the overall model. A thorough analysis of the leading-edge suction analogy model is provided and comparison of the aerodynamic model with results from application of the leading-edge suction analogy shows good agreement. The full model is evaluated against experimental data for revolving wings and good agreement is obtained for lift and drag up to 90° incidence. Comparison of the model output with data from computational fluid dynamics studies on a range of different insect species also shows good agreement with predicted weight support ratio and specific power. The validated model is used to evaluate the relative impact of different contributors to the induced power factor for the hoverfly and fruitfly. It is shown that the assumption of an ideal induced power factor ( k = 1) for a normal hovering hoverfly leads to a 23% overestimation of the generated force owing to flapping.

ACS Style

Mostafa R. A. Nabawy; William Crowther. On the quasi-steady aerodynamics of normal hovering flight part II: model implementation and evaluation. Journal of The Royal Society Interface 2014, 11, 20131197 .

AMA Style

Mostafa R. A. Nabawy, William Crowther. On the quasi-steady aerodynamics of normal hovering flight part II: model implementation and evaluation. Journal of The Royal Society Interface. 2014; 11 (94):20131197.

Chicago/Turabian Style

Mostafa R. A. Nabawy; William Crowther. 2014. "On the quasi-steady aerodynamics of normal hovering flight part II: model implementation and evaluation." Journal of The Royal Society Interface 11, no. 94: 20131197.