Journals
On the numerical assessment of engine exhaust plumes with a scaled cowling Mohamed, M.A., Teo, Z.W., New, T.H. and Ng, B.F., Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, 2023. DOI |
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Investigation of recycled materials for radiative cooling under tropical climate Han, D., Fei, J., Wan, M. P., Li, H. and Ng, B.F., Nanophotonics, 2023. DOI |
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Jing, P., He, G., Chen, B., Zhang, C., Ng, B. F., Physics of Fluid, 2023. DOI |
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Experimental study on the impact of indoor air quality on creativity by Serious Brick Play method Arikrishnan, S., Roberts, A.C., Lau, W.S., Wan, M.P. and Ng, B.F., Scientific Reports, 2023. DOI |
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Liu, Y., Wang, L. and Ng, B.F., Computer Methods in Applied Mechanics and Engineering, 2023. DOI |
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Mechanics of Re-Entrant Anti-Trichiral Honeycombs with Nature-Inspired Gradient Distributions Zhang, E.T., Liu, H. and Ng, B.F., International Journal of Mechanical Sciences, 2023. DOI |
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Mohamed, M.A., Wood, D. and Ng, B.F., Physics of Fluid, 2023. DOI |
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Modelling of fire-suppressant injection into engine nacelle for various flight regimes Mohamed, M.A., New, T.H. and Ng, B.F., Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, 2023. DOI |
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Physics-Informed Neural Networks for Low Reynolds Number Flows over Cylinder Ang, E.H.W., Wang, G. and Ng, B.F., Energies, 2023. DOI |
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Structure and mechanical properties of ladybird elytra as biological sandwich panels Zhou, J., Ng, B.F., Han, N., Chen, L., Wang, Z., Li, X. and Zou, M., Journal of the Mechanical Behavior of Biomedical Materials, 2023. DOI
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Actuator fault detection and isolation on multi-rotor UAV using extreme learning neuro-fuzzy systems Thanaraj, T., Low, K.H. and Ng, B.F., ISA Transactions, 2023. DOI
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Energy harvesting performance of a tandem-hydrofoil based closely-interconnected tidal array Wang, G. and Ng, B.F., Energy Conversion and Management, 2023. DOI
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Crashworthiness and optimization of bionic sandwich cores under out-of-plane compression Zhou, J., Ng, B.F., Han, N., Xu, S. and Zou, M., International Journal of Mechanical Sciences, 2023. DOI In this paper, novel bionic sandwich cores are proposed based on the cross section of seagull feather shaft to provide an effective protective mechanism against impact. Compared to conventional honeycomb core, the optimal peak force of the bionic core is decreased by 11.53%. Through the combination of experiment, simulation and theoretical analysis, this study provides a novel idea for the optimization of the crashworthiness of the bionic core under out-of-plane compression. |
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Flow Structures of Wishbone Vortex Generators and Their Interactions with a Backward-Facing Ramp Cheawchan, A., Mohamed, M.A., Ng, B.F. and New, T.H., Journal of Aerospace Engineering, 2023. DOI In this study, streamwise vortex structures produced by wishbone vortex generators (VGs) and their interactions with a 30° backward-facing ramp (BFR) are investigated to understand their impact upon BFR flow separation behavior at Re=3×10^6. In particular, the effects of skewing the VGs relative to the free-stream are considered and results compared to those reported for vane-type VGs previously. Near-field formations of and interactions between the primary streamwise, horseshoe, and edge vortices are clarified along with the stagnation points and recirculating regions, where they are sensitive towards the VG skewness angle. |
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Energy harnessing of multiple semi-active flapping ellipses in V-shape formation Gong, L., Zhu, H., Huan, C., Bao, Y., Zhou, D., Han, Z. and Ng, B.F., Physics of Fluids, 2022. DOI Two-dimensional numerical simulations based on an immersed boundary method are performed for the two-foil system with varying spacings, and a staggered arrangement with a spacing normalised by chord length (Xd/D, Yd/D)=(2.0, 2.5) is found to be the most favourable for energy harnessing with efficiency enhancement of nearly 40% for the downstream foil. Based on the staggered arrangement for the two-foil system, a V-shape formation is further proposed for the multiple-foil system and verified with the highest efficiency of energy harnessing up to nearly twice that of a single foil. |
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The criteria to achieving sub-ambient radiative cooling and its limits in tropical daytime Han, D., Fei, J., Li, H. and Ng, B.F., Building and Environment, 2022. DOI The criteria to achieve sub-ambient temperatures in the challenging conditions of tropical daytime is recommended. Briefly, the total solar reflectance of the material should be above 97% with an infrared emittance of over 80% to achieve sub-ambient temperatures. To illustrate, the feasibility of daytime radiative cooling under Singapore’s tropical climate is investigated using a radiative cooler that meets these criteria and a sustained daytime sub-ambient temperature of 2°C can be achieved under direct exposure to solar intensity of 1000 W/m2 and downwelling atmospheric radiation of 450 W/m2. |
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Switchable Surface Coating for Bifunctional Passive Radiative Cooling and Solar Heating Fei, J., Han, D., Ge, J., Wang, X., Koh, S. W., Gao, S., Sun, Z., Wan, M.P., Ng, B.F., Cai, L., and Li, H., Advanced Functional Materials, 2022. DOI Herein, single-layer coating made in a facile one-step process is reported, which exhibits rapid switch between high solar reflection (≈96.6%) and high solar transmission (≈86.6%). In the dry state, high solar reflectance and infrared (IR) emittance (>96% from 8 to 13 µm) enable passive radiative cooling, resulting in all-day near/sub-ambient temperatures. Upon wetting, high transparency in the broadband range (0.3–2.5 µm) allows solar heating, leading to switchable thermal regulation. This structure breaks the thickness constraint and broadens its applicability for seasonal areas with large temperature variation throughout the day. |
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Sub-ambient radiative cooling under tropical climate using highly reflective polymeric coating Han, D., Fei, J., Mandal, J., Liu, Z., Raman, A.P. and Ng, B.F., Solar Energy Materials and Solar Cells, 2022. DOI For the first time, sub-ambient temperatures are achieved in tropical daytime by a cost-effective single-layer coating. Surfaces could maintain sub-ambient temperatures under direct exposure to the sky and surroundings even when the solar intensity was 1000 W/m2 and downwelling atmospheric radiation was 480 W/m2, while separately achieving 2°C below ambient during night-time with an effective cooling power of 54.4 W/m2. With a scalable fabrication-process, our cost-effective single-layer coating can be easily applied to diverse substrates, which is suitable for real-world applications in the tropics. |
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Liu, H., Zhang, E.T., Wang, G. and Ng, B.F., International Journal of Mechanical Sciences, 2022. DOI Inspired by nature, an innovative graded hierarchical honeycomb is proposed to enhance crashworthiness by replacing cell walls of regular honeycombs with triangular and hexagonal sub-structures and varying the hierarchical length ratio in each layer. The triangular sub-structure presents better energy absorption than the hexagonal sub-structure, and its specific energy absorption is enhanced by up to 32.2% as compared to the uniform hierarchical honeycomb. The present study suggests that the combination of hierarchy and gradient is an effective strategy to improve the dynamic crushing behaviors of honeycombs. |
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A numerical investigation on flow past skewed vortex generators ahead of a backward facing ramp Cheawchan, A., Mohamed, M.A., Ng, B.F. and New, T.H., Aerospace Science and Technology, 2022. DOI Flow past a backward facing ramp with rectangular vane-type VGs located upstream are studied numerically using OpenFOAM based steady-state RANS simulations. Streamwise and cross-stream results show that single VGs produce counter-rotating streamwise vortices with increasingly different vortex-core strengths and vortical interactions when skewness angle increases. The use of multiple VGs under the same condition further accentuate these behaviour and results in significant changes to the wall shear stress distribution. |
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Infection risk of SARS-CoV-2 in a dining setting: Deposited droplets and aerosols Ding, S., Lee, J.S., Mohamed, M.A. and Ng, B.F., Building and Environment, 2022. DOI Considering that safe-distancing and mask-wearing measures are not strictly enforced in dining settings in the context of SARS-CoV-2, the infection risks of patrons in a dining outlet (e.g., a cafe) is assessed in this study. In a four-person dining setting around a rectangular table, a diner seated diagonally across an infected person posed the least infection risk and current ventilation standards (e.g., 8–10 L/s per person) for a cafe are not enough to avoid the airborne transmission of SARS-CoV-2. |
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Dynamic response of density-graded foam subjected to soft impact Liu, H. and Ng, B.F., Composite Structures, 2022. DOI An analytical model based on the double shock wave theory is established by using a deformable projectile impinging onto a density-graded foam target. The dynamic stress at the supported end is analyzed for uniform, positive, and negative density gradients. The findings indicate lower mechanical requirements of target materials for soft projectile impact protections, potentially leading to weight and cost savings. |
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Zhang, E.T., Liu, H. and Ng, B.F., J Composites Part B: Engineering, vol. 227, pp. 109366, 2021. DOI In this study, novel re-entrant anti-trichiral (REAT) structures with arc-shaped ligaments are proposed to enhance both the elastic modulus and energy absorption capabilities through both experimental and numerical approaches. The study sheds light on the development of novel REAT honeycombs that can be achieved through simple ligament modifications and combinational designs. |
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Crashworthiness improvements of multi-cell thin-walled tubes through lattice structure enhancements Liu, H., Chng, Z.X.C., Wang, G. and Ng, B.F., International Journal of Mechanical Sciences, 2021. DOI Taking advantage of multi-cell tubes and lattice structures on improving crashworthiness performances, a novel multi-cell thin-walled tube filled with uniform and graded lattice structures is explored in this paper. It is observed that the multi-cell tubes exhibit significant improvements to the absorbed energy and crushing force efficiency over the single-cell tubes. In addition, the specific energy absorption (SEA) is improved by 78.6% with respect to the sum of its individual constituents. |
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Ma, X.Y.D., Zeng, Z., Wang, Z., Xu, L., Zhang, Y., Ang, J.M., Wan, M.P., Ng, B.F. and Lu, X., Journal of Membrane Science, 2021. DOI In this article, we report highly porous yet robust microhoneycomb-like nanofibrous aerogels (NFAs) with porous cell walls and hierarchical porous structures, and their potential as durable high-performance air filters. In particular, a high filtration efficiency of 99.86% with a fairly low pressure drop (ΔP) of 59.5 Pa could be achieved for 0.1 μm particles at the face velocity of ∼5 cm s−1. |
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Aerosols from Speaking can Linger in the Air for up to Nine Hours Ding, S., Teo, Z.W., Wan, M.P. and Ng, B.F., Building and Environment, 2021. DOI To understand the role of speech aerosols in the spread of COVID-19 globally, the lifetime and size distribution of the aerosols are studied through a combination of light scattering observation and aerosol sampling. It was found that aerosols from speaking suspended in stagnant air for up to 9 h with a half-life of 87.2 min. |
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Toh, Y.H. and Ng, B.F., Physics of Fluid, 2021. DOI A novel approach to curvature effects based on the bifurcation theory and rotation turbulence energy spectrum is implemented to improve the sensitivity of the k-epsilon two-equation turbulence model (Jones–Launder form) to curved surfaces. This is done by accounting for the vorticity tensor, which becomes more significant in curved flows, something that the standard k-epsilon model does not originally consider. |
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Performance augmentation of tandem flapping wings in asymmetric flapping strokes Wang, G., Ng, B.F., Teo, Z.W., Lua, K.B. and Bao, Y., Aerospace Science and Technology, 2021. DOI The performance augmentation mechanism of a tandem-foil system undergoing time-asymmetric flapping with unequal up- and downstroke durations (velocities) is investigated at three different phase angles, 0°, 90°, and 180°. The findings not only provide insights toward the characteristics of tandem foils which are operated in non-sinusoidal flapping strokes but also offer a reference to the design of efficient wing kinematics for high-performance biomimetic propulsors. |
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Ding, S. and Ng, B.F., Rapid Prototyping Journal, 2021. DOI This study examines on-site particle concentration levels due to emissions from a wide spectrum of additive manufacturing techniques, including polymer-based material extrusion, metal and polymer-based powder bed fusion, directed energy deposition and ink-based material jetting. |
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In-plane dynamic crushing of a novel honeycomb with functionally graded fractal self-similarity Liu, H., Zhang, E.T. and Ng, B.F., Composite Structures, 2021. DOI In this study, a series of novel fractal honeycombs are proposed based on the combination of functionally gradient with fractal self-similarity features, which are constructed by varying the fractal parameter in each layer of the traditional self-similar honeycombs. It is demonstrated that SG-I honeycomb present the best energy absorption behavior (89% higher than traditional honeycomb) for low-velocity impact, while SG-II honeycomb performs the best for specific energy absorption (17% larger than traditional honeycomb) for high-velocity impact. |
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Yang, S., Wan, M.P., Ng, B.F., Dubey, S., Henze, G.P., Chen, W. and Baskaran, K., Applied Energy, 2021. DOI A MPC system that features a multi-objective scheme to enable coordinated control of multiple building services for overall optimized energy efficiency, indoor thermal and visual comfort, as well as a hybrid model for predicting indoor visual comfort and lighting power is proposed and demonstrated in this study. The MPC achieved 15.1–20.7% electricity consumption reduction, improved indoor thermal comfort by maintaining the room within the comfortable range for 98.3% of the time, up from 91.8% of the time on the BMS side. Visual comfort was maintained for the entire test period on the MPC side. |
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Flow behavior of skewed vortex-generators on a backward-facing ramp Cheawchan,., Wen, Y., Teo, Z.W., Ng, B.F. and New, T.H., Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, 2021. DOI The impact of skewness angle on the effectiveness of VGs and the behavior of streamwise vortices on flow separation behind a backward-facing ramp (BFR) with a sharp transition were experimentally investigated using surface oil flow visualizations, planar and stereoscopic particle image velocimetry measurements. Results show that the reattachment length was reduced by ∼45% when the VG was located five times its height ahead of the transition. |
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Yang, S., Wan, M.P., W. Chen, Ng, B.F. and Dubey, S., Applied Energy, 2021. DOI This study proposes a recurrent neural network with nonlinear autoregressive network and exogenous inputs for building controls without needing to solve the optimization problem, significantly reducing the computation load as compared to MPC. The MPC and neural network reduced 58.5% and 51.6% of cooling energy consumption, respectively, as compared to the original control. Meanwhile, both methods significantly improved indoor thermal comfort and the neural network was more than 100 times faster than MPC. |
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Ding, S., Wan, M.P. and Ng, B.F., Environmental Science and Technology, 2020. DOI Here, a dynamic analysis of the size-resolved particle emission rates from FDM printers is conducted through a comparative study of chamber and flow tunnel measurements. It was found that chamber measurements for different materials underestimated PER by up to an order of magnitude and overestimated particle diameters by up to 2.3 times, while the flow tunnel measurements provided more accurate results. |
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Teo, Z.W., Wong, W.H., Lee, Z.W., New, T. H. and Ng, B.F., Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, 2020. DOI In this study, a scaled helicopter fuselage model was used to simulate hot exhaust gases by engines that may inadvertently impinge upon the tail boom or dissipate inefficiently that compromises on operation safety. The observations on the trajectory and shape of plume provide basis to understanding the nature and interaction of the plume with its surroundings. |
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Zhang, N., Liu, H., Ng, B.F. and Low, K.H., Transportation Research Part C: Emerging Technologies, 2020. DOI To minimize the interference of drones on normal operations in the airports, a collision probability evaluation scheme based on collision-course trajectories modeling is proposed. Firstly, a trajectory planning model of drones intruding restricted airspace is derived based on a given trajectory of the commercial aircraft (CA) and the collision-course of the drone. Subsequently, a probabilistic model based on the stochastic kinematic model is developed to implement the collision risk evaluation. |
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Yang, S., Wan, M.P., Chen, W., Ng, B.F. and Dubey, S., Applied Energy, 2020. DOI A MPC system with adaptive machine-learning-based building models for building automation and control applications is proposed. The system features an adaptive machine-learning-based building dynamics modelling scheme that updates the building model regularly using online building data through an artificial neural network with a nonlinear autoregressive exogenous structure. The MPC system reduces 58.5% cooling thermal energy consumption in the office and 36.7% cooling electricity consumption in the lecture theatre. |
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Zhou, M., Long, Y., Zhang, X., Kiran Kumar, D.E.V.S., Ng, B.F. and Wan, M.P., Journal of Geophysical Research: Atmospheres, 2020. DOI Mesoscale meteorological modeling was used to study the urban heat island (UHI) effect and urban cooling effect by applying cool coating on various urban surfaces. At nighttime, when the UHI effect is generally more intense than daytime, applying cool coating on all urban surfaces can reduce the UHI effect by about 30% in residential areas and about 6% in commercial/industrial areas. Maximum T2 reduction of 3.1°C and surface skin temperature (TSK) reduction of 9.8°C due to cool coating is found at 13:00 at certain locations. |
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Investigation of CFD-PBM simulations based on fixed pivot method: Influence of the moment closure Shang, X., Ng, B.F., Wan, M.P. and Ding, S., Chemical Engineering Journal, 2020. DOI We present a comprehensive investigation regarding the influence of moment closure on population balance and hydrodynamics in the coupled CFD-PBM simulations. The CFD-PBM model conserves the surface area and volume (second and third moment), and the number and volume (zeroth and third moment). |
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Shang, X., Wan, M.P., Ng, B.F., and Ding, S., Powder Technology, 2020. DOI A novel CFD-sectional algorithm is developed to address the challenges in the existing sectional simulations coupled with multi-dimensional fluid dynamics. The acoustic agglomeration in a standing wave is simulated as a representative case. Predictions of particle size distribution and agglomeration process agree well with the experimental data, which verifies capability of the algorithm in simulating spatially inhomogeneous population balance equation coupled with multi-dimensional flows. |
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Yang, S., Wan, M.P., Ng, B.F., Dubey, S., Henze, G.P., Chen, W. and Baskaran, K., Applied Energy, 2020. DOI This paper presents a novel MPC developed for a dedicated outdoor air system (DOAS)-assisted SSLC system, adopting a linear state-space model that captures building thermodynamics, thermal comfort and ACMV for building response prediction and optimization. The MPC system achieved 18% and 20% electricity savings for the single-coil AHU and DOAS-assisted SSLC, respectively, as compared to the BMS controlled single-coil AHU. Furthermore, indoor thermal comfort is significantly improved. |
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Xiong, J.W., Wan, M.P., Ng, B.F. and You, S., Aerosol and Air Quality Research, 2020. DOI We propose a method for identifying and quantifying the emanation of viable bioaerosol from an ACMV system and its impact on indoor pollution through surface and air sampling followed by analysis using a material-balance model. The ACMV system was found to be the largest emission source of indoor viable bacteria and the second largest source of indoor viable fungi in the air. Our method can be used as a tool for analysing the potential sources of indoor bioaerosol and supporting the development of effective control measures. |
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Preliminary Study of Passive Radiative Cooling under Singapore’s Tropical Climate Han, D., Ng, B.F. and Wan, M.P., Solar Energy Materials and Solar Cells, 2020. DOI Sub-ambient cooling can be achieved through radiative coolers that selectively emit radiation within the atmospheric window (8–13 μm) to outer space and suppress absorption/emission of other wavelengths. This study explores the feasibility of adopting radiative cooling in the hot and humid climate of Singapore through both numerical and experimental approaches. |
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Wang, Z., Zhang, Y., Ma, X.Y.D., Ang, J.M., Zeng, Z., Ng, B.F., Wan, M.P., Wong, S-C. and Lu, X., Separation and Purification Technology, 2020. DOI We report a new type of multilayer membranes that exhibits excellent filtration efficiencies for PM of various sizes, low air resistance and good directional moisture transport properties. The membrane exhibits high removal efficiencies of 99.973% for 0.3-μm particles and ≧99.99% for particles of other sizes, including the more harmful ultrafine particles, at a low pressure drop of 80.1 Pa. |
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Ding, S., Ng, B.F., Shang, X., Liu, H., Lu, X. and Wan, M.P., Science of the Total Environment, 2019. DOI Here, we characterize the formation mechanisms of emissions from polymer filaments commonly used in FDM 3D printing. It is observed that emissions initiate at the start of the glass transition process and peak during liquefaction for filaments. More importantly, low heating rate has the potential to restrain the formation of carcinogenic monomer, styrene, from ABS. A TVOC measurement method based on weight loss found that TVOC mass yield was 0.03%, 0.21% and 2.14% for PLA, ABS, and PVA, respectively, at 220 °C. |
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Aeroelastic Load Control of Large and Flexible Wind Turbines through Mechanically Driven Flaps X. Wei, Ng, B.F. and Zhao, X., Journal of the Franklin Institute, 2019. DOI A passive mechanical controller is proposed for blade load reductions, which is realised by passive components including springs, dampers and inerters in rotational form. The parameters of the mechanical components and flap configuration parameters are optimised by H∞ and H2 optimisation, respectively. It is shown that mechanical controllers exhibit marked reductions in blade root-bending moment, blade tip deflection and tower top fore-aft deflection in the presence of external disturbances. |
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Yang, S., Wan, M.P., Ng, B.F., Dubey, S., Henze, G.P., Rai, S. K. and Baskaran, K., Energy and Buildings, 2019. DOI The control characteristics and performance of the MPC controller in controlling a FCU and an ACB system were investigated experimentally in the BCA SkyLab. Compared to the original BMS, the MPC controller achieved 14.7% and 20% electricity savings for the conventional FCU and ACB systems, respectively. The MPC controller also kept the indoor PMV within acceptable thermal comfort range at all time. |
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Yang, S., Wan, M.P., Chen, W., Ng, B.F. and Zhai, D., Building and Environment, 2019. DOI An adaptive robust MPC (ARMPC) is proposed to refine building models and handle uncertainty of disturbances. When an energy-saving-biased setting is applied, ARMPC achieves the best thermal comfort performance among the tested controllers. The energy savings achieved by the ARMPC vary from ~20% to ~15%, compared to the thermostat, as uncertainty level of internal load increases from 0% to 60%. |
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Liu, H., Ding, S. and Ng, B.F., J Composites Part B: Engineering, 2019. DOI An analytical model based on the double shock wave theory is presented to examine the impact performance of density-graded foam rods under temperature gradient environments. A density-graded foam with one end supported and the other end struck by a mass is presented to evaluate impact performances. It is demonstrated that the temperature gradient may lead to transformations in the deformation pattern, enlarge the impact resistance property in most cases and can reduce the energy absorption capacity of density-graded foams. |
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Ma, X.Y.D., Ang, J.M., Zhang, Y., Zeng, Z., Zhao, C., Chen, F., Ng, B.F., Wan, M.P., Wong, S-C., Li, Z., He, C. and Lu, X., Polymer, 2019. DOI We design stable, highly porous PLLA/PDLA blend nanofibrous aerogels (NFAs) fabricated by cross-linking the electrospun nanofibers via spontaneous inter-fiber stereocomplexation, and the potential of the NFAs as an air filter for capturing ultrafine airborne particles. When combined with a layer of HEPA filter to form a composite filter, the NFAs show the potential to significantly improve the filtration efficiency for ultrafine particles with a slight increase in pressure drop. This is attributed predominantly to the high porosity of the NFAs, as well as the slip flow effect of nanofibers. |
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Zeng, Z., Ma, X.Y.D., Zhang, Y., Wang, Z., Ng, B.F., Wan, M.P. and Lu, X., ACS Sustainable Chemistry & Engineering, 2019. DOI We report a new type of lignin-based wood-like aerogel filters composed of aligned micrometer-sized pores and cross-linked lignin-based cell walls. Abundant functional groups retained from lignin and the aligned pore channels lead to high filtration efficiency for ultrafine particles accompanied by fairly low pressure drop. Through filtration tests with particles of various sizes, it is revealed that the air filtration is dominated by diffusion, rather than impaction or interception mechanism, which offers a new avenue for design of novel high-performance air filters. |
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Zhang, Y., Zeng, Z., Ma, X.Y.D., Zhao, C., Ang, J.M., Ng, B.F., Wan, M.P., Wong, S-C. Wang, Z. and Lu, X., Applied Surface Science, 2019. DOI Inspired by mussel glue, cross-linked 3D polyacrylonitrile (PAN) nanofibrous aerogels (NFAs) with ultrahigh porosity, hierarchical porous structures, and good compression resistance are successfully fabricated. When a thin layer of the optimized 3D NFA with a large specific surface area (85.7 m2 g−1) is combined with a commercial air filter, high filtration efficiencies of 99.72% and 99.85% are obtained for particles <100 nm and <500 nm, respectively, at a low pressure drop of only 54.1 Pa. |
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Yan, T., Wang, R., Bao, Y., Zhou, D., Zhu, H.B., Ping, H., Han, Z.L. and Ng, B.F., Physics of Fluids, 2018. DOI In this paper, the flow around a main circular cylinder with two small control cylinders is numerically investigated at a subcritical Reynolds number of 3900. For the main cylinder, the dynamics of shear layers is found to be modified strongly by disturbance from the small control cylinders. As a consequence, the recirculation length is decreased by 89% as compared to that of a single cylinder. This study then suggests that the small control cylinders located in the near wake region of the main cylinder may work differently in the turbulent wake against that in the laminar wake. |
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Numerical Investigation of Spatially Nonhomogeneous Acoustic Agglomeration Using Sectional Algorithm Shang, X., Ng, B.F., Wan, M.P., Xiong, J.W. and Arikrishnan, S., Aerosol Science and Technology, 2018. DOI In this article, we investigated the effects of spatial nonhomogeneity of sound field on the acoustic agglomeration (AA) process through a 1-D spatial sectional model. The first simulation case involves AA in a standing wave field with spatial alternation of acoustic kernels from nodes to antinodes and showed good agreement with experiments. The second case incorporates sound attenuation in the particulate medium into AA, which shows that it can influence AA significantly, particularly at high frequencies. |
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Yang, S., Wan, M.P., Ng, B.F., Zhang, T., Babu, S., Zhang, Z., Chen, W., and Dubey, S., Energy and Buildings, 2018. DOI This paper proposes a method to develop an integrated state-space model (SSM) for indoor air temperature, radiant temperature, humidity and Predicted Mean Vote (PMV) index suitable for fast real-time multiple objectives optimization. Demonstrated on the BCA SkyLab test bed facility in Singapore, the MPC controller can achieve up to 19.4% energy savings while keeping the PMV index within the acceptable comfort range. |
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Ng, B.F., Xiong, J.W., and Wan, M.P., PloS one, 2017. DOI This paper discusses the basic mechanisms of acoustic agglomeration along with influencing factors that could affect the agglomeration efficiency. The feasibility to apply acoustic agglomeration to improve filtration in air-conditioning and mechanical ventilation (ACMV) systems is investigated experimentally in a small-scale wind tunnel. Experimental results indicate that this novel application of acoustic pre-conditioning improves the PM2.5 filtration efficiency of the test filters by up to 10% without introducing additional pressure drop. |
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Model-based aeroelastic analysis and blade load alleviation of offshore wind turbines Ng, B.F., Palacios, R., and Graham, J.M.R., International Journal Control, 2017. DOI This paper introduces a computational methodology for model-based two- and three-dimensional design of load alleviation systems on offshore wind turbines. The aero-hydro-servoelastic model is formulated in a convenient state-space representation, coupling a multi-body composite beam description of the main structural elements with unsteady vortex-lattice aerodynamics and Morison’s description of the hydrodynamics. Numerical results show that trailing-edge flaps actuated by a robust controller can lead to 13% reduction in blade loads. |
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Effects of Leading-Edge Tubercles on Wing Flutter Speeds Ng, B.F., New, T. H. and Palacios, R., Bioinspiration & Biomimetics, 2016. DOI The dynamic aeroelastic effects on wings modified with bio-inspired leading-edge (LE) tubercles are examined in this study. We adopt a state-space aeroelastic model via the coupling of unsteady vortex-lattice method and a composite beam to evaluate stability margins as a result of LE tubercles on a generic wing. Flutter speed is observed to be 5% higher, and this is accompanied by close to 6% decrease in reduced frequencies as an indication of lower structural stiffness requirements for wings with LE tubercles. |
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Ng, B.F., Palacios, R., Graham, J.M.R., Kerrigan, E.C., and Hesse, H., Wind Energy, 2016. DOI We present an aeroelastic modeling approach using geometrically non-linear composite beams coupled with linearized unsteady vortex lattice method, and the resulting aeroelastic system is written in a state-space description. When used for dynamic load alleviation in large wind turbines with composite blades and trailing-edge aerodynamic surfaces, H-infinity controller is capable of providing load reductions of up to 13% in closed loop on the full wind turbine non-linear aeroelastic model. When combined with passive load alleviation through aeroelastic tailoring, dynamic loads can be further reduced to 35%. |
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Aeroservoelastic state-space vortex lattice modeling and load alleviation of wind turbine blades Ng, B.F., Hesse, H., Palacios, R.,Graham, J.M.R., and Kerrigan, E.C., Wind Energy, 2015. DOI An aeroservoelastic model, capturing the structural response and the unsteady aerodynamics of turbine rotors, is used to demonstrate the potential of active load alleviation using aerodynamic control surfaces. The resulting aeroelastic model is in a state-space formulation suitable for control synthesis. Flaps are modeled directly in the vortex lattice description and using a reduced-order model of the coupled aeroelastic formulation, a linear-quadratic-Gaussian controller is synthesized and shown to reduce root mean square values of the root-bending moment and tip deflection in the presence of continuous turbulence. |
Book
Flow Control Through Bio-inspired Leading-Edge Tubercles New, T.H. and Ng, B.F. (eds). Springer Nature, Cham, 2020. DOI This is the first book to document the novel concept of bio-inspired leading-edge tubercles derived from humpback whale flippers. It provides a practical guide to key scientific and engineering aspects of leading-edge tubercles, leading from the aerodynamics, hydrodynamics, noise attenuation, stability and applications. |
Book Chapter
Effects of Leading-Edge Tubercles on Structural Dynamics and Aeroelasticity Ng, B.F., Ong, E.J.G., Palacios, R. and New, T.H., (2020). In: New D., Ng B. (eds) Flow Control Through Bio-inspired Leading-Edge Tubercles. Springer Nature, Cham. DOI The design of tubercles has both aerodynamics and structural considerations. In this chapter, we discuss structural design, stability and aeroelasticity of lifting surfaces that are modified with leading-edge (LE) tubercles. With LE tubercles, bending and torsional frequencies are slightly lower due to the combined effects of spanwise stiffness and inertia variations from spanwise chord length variation and mass redistribution. Numerical investigations show that the flutter speed is consistently mildly higher with LE tubercles and they have reduced effect on the margins for stability when concentrated inboard of the wing or on sweptback wings as the sweep angle is increased. |
Conferences
- Ang, E., Tay, C.M., Cui, Y.D. and Ng, B.F., Wind Tunnel Experiments on Body-Freedom Flutter of Unmanned Aerial Vehicles. Aerospace Technology Seminar (ATS) 2023, Singapore
- Thanaraj, T., Govind, S., Anurag, R., Ng, B.F. and Low, K.H., An Octorotor UAV Reliability Framework for Safe Flight Operations. International Conference on Unmanned Aircraft Systems, ICUAS 2023, Warsaw, Poland
- Han, D. and Ng, B.F., Investigation of Recycled Materials for Radiative Cooling under Tropical Climate. 14th International Conference on Sustainable Energy & Environmental Protection, 2022, London, UK
- Han, D. and Ng, B.F., Investigation of Radiative Cooling under Tropical Climate using Recycled Materials. French Singaporean research network on Renewable Energy, 2022, Aix-en-Provence, France
- Thanaraj, T., Sidharth, R.S., Ng, B.F. and Low, K.H., Hardware-in-the-loop Simulation for Quadrotor Fault Diagnosis Enhancing Airworthiness using OS-Fuzzy-ELM. International Conference on Unmanned Aircraft Systems, ICUAS 2022, Dubrovnik, Croatia. Doi: https://ieeexplore.ieee.org/document/9836162
- Thanaraj, T., Ng, B.F. and Low, K.H., Active Fault Tolerant Control on Multi-rotor UAVs using ELM-based Neuro-Fuzzy System. American Institute of Aeronautics and Astronautics, AIAA Aviation 2022, Chicago, IL, USA Doi: https://doi.org/10.2514/6.2022-3510
- Ang, E. and Ng, B.F., State-Space Aeroelastic Modelling of Flying Wings. International Forum on Aeroelasticity and Structural Dynamics, IFASD 2022, Madrid, Spain
- Ng, B.F. and Ding, S., As Assessment of Particle Exposure during 3D Printing. Global Webinar on 3D Printing and Additive Modelling, Online Plenary Presentation, 2022
- Ng, B.F., New, T.H., Mohamed, M.A., Cheawchan, A. and Teo, Z.W., On the Modelling of the Injection of fire extinguishing agents into an Engine Bay. Singapore Aerospace Technology & Engineering Conference, 2022, Guest speaker, Singapore
- Ng, B.F. and Han D., Passive Radiative Cooling for Hot and Humid Climates. 6th International Conference on Energy and Environmental Science & 8th International Conference on Renewable Energy Technologies, Invited Online Presentation, 2022
- Ang, E. and Ng, B.F., Physics-Informed Neural Networks for Flow Around Airfoil. American Institute of Aeronautics and Astronautics, AIAA Scitech 2022 Forum, USA, Online. DOI: https://arc.aiaa.org/doi/abs/10.2514/6.2022-0187
- Cheawchan, A., New, T.H., Mohamed, M.A. and Ng, B.F., Flow past Skewed Wishbone-type Vortex Generators upstream of a Backward Facing Ramp. The 19th International Symposium on Flow Visualization (ISFV-19), Online, 2020
- Thanaraj, T., Ng, B.F. and Low, K.H., Preliminary Study of Actuator Fault Detection for RUAVs using Neuro-Fuzzy System. American Institute of Aeronautics and Astronautics, AIAA Scitech 2021 Forum, USA, Online. DOI: https://doi.org/10.2514/6.2021-1055
- Toh, Y.H., Mohamed, and Ng, B.F., Eddy Viscosity Modelling Around Curved Boundaries. American Institute of Aeronautics and Astronautics, AIAA Scitech 2021 Forum, USA, Online. DOI: https://doi.org/10.2514/6.2021-1949
- Liu, H., Che Man, M.H., Ng, B.F. and Low, K.H., Airborne collision severity study on engine ingestion caused by harmless-categorized drones. American Institute of Aeronautics and Astronautics, AIAA Scitech 2021 Forum, USA, Online. DOI: https://doi.org/10.2514/6.2021-1263
- Wang, C.H.J., Nathanael J.C., Ng, E. M., Ng, B.F. and Low, K.H., Framework for the Estimation of Safe Wake Separation Distance between Same-Track Multi-Rotor UAS. American Institute of Aeronautics and Astronautics, AIAA SciTech 2021, USA, Online. DOI: https://doi.org/10.2514/6.2021-0708
- Roberts, A.C., Arikrishnan, S., Xiong, J., Ng, B.F. and Wan, M.P., The Effect of Sick Building Syndrome and Perceived Air Quality on Memory and Cognition. The 16th Conference of the International Society of Indoor Air Quality & Climate 2020. Online.
- Arikrishnan, S., Roberts, A.C., Ng, B.F., Soh, C.K. and Wan, M.P., Associations between Indoor Air Quality and Cognitive Health: A randomised masked trial in the tropics. The 16th Conference of the International Society of Indoor Air Quality & Climate 2020. Online.
- Ang, E. and Ng, B.F., Physics-Informed Neural Networks for the Modelling of Fluid-Structure Interactions. 73rd Annual Meeting of the American Physical Society Division of Fluid Dynamics, USA, Q02.004, 2020, Online.
- Wang, G., Teo, Z. W. and Ng, B.F., A Deep Neural Network (DNN) Model for Predicting the Propulsive Performances of 3D Printed Tandem Flapping Wings with Stroke Time-Asymmetry. 73rd Annual Meeting of the American Physical Society Division of Fluid Dynamics, USA, S02. 006, 2020, Online.
- Che Man, M. H., Liu, H., Ng, B.F. and Low, K.H., Preliminary Evaluation of Thrust Loss in Commercial Aircraft Engine due to Airborne Collision with Unmanned Aerial Vehicles (UAVs). The 2020 International Conference on Unmanned Aircraft Systems, Greece, Athens, 2020. DOI: https://doi.org/10.1109/ICUAS48674.2020.9214048
- Liu, H., Che Man, M. H., Ng, B.F. and Low, K.H., Airborne Collision Evaluation between Drone and Aircraft Engine: Effects of Position and Posture on Damage of Fan Blades. American Institute of Aeronautics and Astronautics, AIAA Aviation 2020, USA, Online. DOI: https://doi.org/10.2514/6.2020-3214
- Teo, Z.W., Wong, W. H., Mohamed, M.A., Ang, H. W., Ng, B.F. and New, T.H., On the Flow Measurements of Simulated Helicopter Exhausts. American Institute of Aeronautics and Astronautics, AIAA SciTech 2020, Orlando, FL, USA, 2020. DOI: https://doi.org/10.2514/6.2020-2226
- Xiong, J.W., Wan, M.P., Ng, B.F. and You, S., Influence of meteorological factors on indoor viable bioaerosol concentrations in offices in Singapore. Healthy Buildings Asia, Changsha, China, 2019
- Ding, S., Ng, B.F. and Wan, M.P., Particle emissions from diverse 3D printers. Healthy Buildings Asia, Changsha, China, 2019
- Shang, X., Ng, B.F., Wan, M.P. and Ding, S., CFD-PBM simulation of bubble columns based on fixed pivot method: Influence of the moment closure. 72nd Annual Meeting of the American Physical Society, American Physical Society Division of Fluid Dynamics, P02. 003, Seattle, WA, USA, 2019
- Ng, T.Y., Lin, R., Toh, W., Koneru, R., Yap, Y.L. and Ng, B.F., Extreme Weight Reduction in the Design and Prototyping Process of 3D-Printed Unmanned Aerial Vehicle (UAVs) – Attraction and Challenges. International Conference and Exhibition on Mechanical and Aerospace Engineering, San Francisco, CA, USA, 2019 [Keynote].
- Ding, S., Shang, X., Ng, B.F. and Wan, M.P., Simulation the acoustic entrainment of moving air-borne microscale droplets. XV Recontres du Vietnam Soft Matter Science, Quy Nhon, Vietnam, 2019
- Kiran Kumar, D.E.V.S., Wan, M.P., Zhou, M., Long, Y. and Ng, B.F., Impact of solar reflectance of wall and road on outdoor thermal comfort – experimental study in a street canyon setup. Central European Symposium on Building Physics, Prague, Czech Republic, 2019
- Mohamed, M.A., Cheawchan, A.U., Teo, Z.W., New, T.H., Ng, B.F., On Coherent Structures Produced By A Vortex-Generator Located Upstream of A Ramp. Eleventh International Symposium on Turbulence and Shear Flow Phenomena (TSFP11), Southampton, UK, 2019
- Kandath, H., Abdul, H., Pratama, M. and Ng, B.F., Robust Evolving Neuro-Fuzzy Control of a Novel Tilt-rotor Vertical Takeoff and Landing. International Conference on Fuzzy Systems, New Orleans, LA, USA, 2019. DOI: https://doi.org/10.1109/FUZZ-IEEE.2019.8858923
- Wei, X., Ng, B.F. and Zhao, X., Aeroelastic Load Control through the Use of a Mechanically Driven Flap. United Kingdom Automatic Control Council, UKACC International Conference on Control (CONTROL), Sheffield, UK, 2018. DOI: https://doi.org/10.1109/CONTROL.2018.8516896
- Zhou, M., Long, Y., Kiran Kumar, D.E.V.S., Ng, B.F. and Wan, M.P., Numerical study of the city-wide effect of albedo change in Singapore. American Geophysical Union, AGU Fall Meeting Abstracts 2018, Washington, DC, USA.
- Yang, S., Wan, M.P., Ng, B.F., Zhang, Z., Lamano, A. and Chen, W., Modelling and model calibration for model predictive occupants comfort control in buildings. 7th International Building Physics Conference, IBPC 2018, Syracuse, NY, USA.
- Jimmy, Zhang, T., Ng, B.F. and Wan, M.P., Modelling Energy System for Intelligent Building Control. The 15th International Conference of Indoor Air Quality and Climate 2018. Philadelphia, PA, USA.
- Lim, Y. Q., Shang, X. P., Ng, B.F. and Wan, M.P., A Comparison of Simulation Methods for the Acoustic Agglomeration of Air-borne Particulate Matter (PM). The 15th International Conference of Indoor Air Quality and Climate 2018. Philadelphia, PA, USA.
- Ng, B.F. and Wan, M.P., Cool surfaces for building energy efficiency and urban thermal comfort. 12th International Conference on Ceramic Materials and Components for Energy and Environmental Applications 2018, Singapore.
- Teo, Z.W., Cheawchan, A.U., Mohamed, M.A., New, T. H. and Ng, B.F., A Flow Visualization Study on the Use of Vortex Generators Upon Ramps to Enhance Helicopter Aerodynamics. 18th International Symposium on Flow Visualization 2018, Zurich, Switzerland. DOI: https://doi.org/10.3929/ethz-b-000279162
- Mohamed, M.A., Teo, Z.W., Cheawchan, A.U. , Chen, Y. H. , Ng, B.F. and New, T.H., Enhancements to Helicopter Aerodynamics – A Leonardo-NTU Research Collaboration. Singapore Aerospace Technology & Engineering Conference, 2018, Singapore.
- Zhang, T., Wan, M.P., Ng, B.F. and S, Yang., Model Predictive Control for Building Energy Reduction and Temperature Regulation. Institute of Electrical and Electronics, IEEE GreenTech 2018 Conference, Austin, TX, USA. DOI: https://doi.org/10.1109/GreenTech.2018.00027
- Lim, J. J. and Ng, B.F., Hydroelasticity of Tidal Current Turbine Blades. Asian Wave and Tidal Energy Conference 2016, Singapore.
- Ng, B.F., Xiong, J.W., Elankovan, S. J. and Wan, M.P., Acoustic-agglomeration enhanced filtration. The 14th International Conference of Indoor Air Quality and Climate 2016. Ghent, Belgium.
- Xiong, J.W. , Ng, B.F. and Wan, M.P., Evaluation of Contribution of an Air-Conditioning and Mechanical Ventilation System to Level of Indoor Bioaerosols. The 14th International Conference of Indoor Air Quality and Climate 2016. Ghent, Belgium.
- Ng, B.F., Hesse, H., Palacios, R., Graham, J.M.R., and Kerrigan, E.C., Model-based Aeroservoelastic Design and Load Alleviation of Large Wind Turbines. 32nd American Society of Mechanical Engineers, ASME Wind Energy Symposium at the AIAA SciTech 2014, National Harbour, MD, USA. DOI: https://doi.org/10.2514/6.2014-0521
- Van Parys, B.P., Ng, B.F., Goulart, P. J., and Palacios, R., Optimal control for load alleviation in wind turbines. 32nd American Society of Mechanical Engineers, American Society of Mechanical Engineers, ASME Wind Energy Symposium at the AIAA SciTech 2014, National Harbour, MD, USA. DOI: https://doi.org/10.2514/6.2014-1222
- Ng, B.F., Hesse, H., Kerrigan, E.C., Palacios, R. and Graham, J.M.R., Efficient aeroservoelastic modeling and control using trailing-edge flaps of wind turbines. United Kingdom Automatic Control Council, UKACC International Conference on Control (CONTROL), 2014, Loughborough, UK. DOI: https://doi.org/10.1109/CONTROL.2014.6915106
- Ng, B.F., Hesse, H., Palacios, R., Graham, J.M.R., and Kerrigan, E.C., Aeroservoelastic Modelling and Active Control of Very Large Wind Turbine Blades for Gust Load Alleviation. 9th PhD Seminar on Wind Energy in Europe 2013, Visby, Gotland, Sweden.
- Ng, B.F., Hesse, H., Palacios, R., Graham, J.M.R., and Kerrigan, E.C., Aeroservoelastic Modelling and Active Load Alleviation of Very Large Wind Turbine Blades. American Wind Energy Association, AWEA Windpower 2013, Chicago, IL, USA.
- Ng, B.F., Hesse, H.. Palacios, R., Graham, J.M.R., and Kerrigan, E.C., Robust control synthesis for gust load alleviation of large aeroelastic wind turbine models. UKACC PhD Presentation Showcase 2012, London, UK.
- Ng, B.F., Palacios, R., Graham, J.M.R., and Kerrigan, E.C., Robust Control Synthesis for Gust Load Alleviation of Large Aeroelastic Wind Turbine Models. 8th PhD Seminar on Wind Energy in Europe 2012, Zurich, Switzerland.
- Ng, B.F., Palacios, R., Graham, J.M.R., and Kerrigan, E.C., Robust Control Synthesis for Gust Load Alleviation from Large Aeroelastic Models with Relaxation of Spatial Discretisation. European Wind Energy Association, EWEA 2012, Copenhagen, Denmark.
- Ng, B.F., Kng, Q. M., Pey, Y. Y. and Schlüter, J. U., On the Aerodynamics of Paper Airplanes. 27th American Institute of Aeronautics and Astronautics, AIAA Applied Aerodynamics Conference 2009, San Antonio, TX, USA. DOI: https://doi.org/10.2514/6.2009-3958