Browsing by Author "Li, Hao"
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Item Open Access Aerodynamic analysis and experiment of a micro flapping wing rotor(Cranfield University, 2015-03) Li, Hao; Guo, Shijun J.This project is aimed at developing a bio-inspired flyable micro/nano aerial vehicle (MAV) of high agility and performance capable of vertical take-off and landing and hovering (VTOLH). To achieve the aim, a novel flapping wing rotor (FWR) concept invented by Dr. Guo has been adopted, which is ideal for MAVs of sub 60 gm and especially for nano scale of sub 5 gm according to aerospace industry’s definition. The advantages and potential of the FWR concept for MAV development has been studied consistently by Dr. Guo’s research team in the last five years. However making a flyable micro FWR model especially in sub 5gm and demonstrate its VTOLH feasibility remains as a big challenge and has not been achieved in previous projects. To meet the above objective, the first achievement in the project is the successful design, build and test of a flyable micro FWR model (FWR-EX1) of only 3 gm based on off-the-shelf available micro motor. The key breakthrough is to achieve the necessary large aeroelastic twist of the flapping wing during the upstroke in an adaptive manner for structural and aerodynamic efficiency. To achieve the next objective for design and performance improvement, study has also been focused on deeper scientific understanding and analysis of the FWR mechanisms. Attention has therefore been paid to a systematic study on aerodynamic modelling and efficiency of the FWR. The method is based on a revised quasi-steady aerodynamic model that combines the theoretical method and experimental data. The numerical results of the revised quasi-steady aerodynamic model are in agreement with existing results obtained via CFD methods. Based on the model and analysis, the optimal kinematics for the FWR has been determined. Subsequently a comparison of the FWR aerodynamic efficiency was made with two other most studied configurations of MAVs, the insect flapping wing and rotorcraft ... [cont.].Item Open Access Aerodynamic efficiency of a bio-inspired flapping wing rotor at low Reynolds number(Royal Society Open Science, 2018-03-14) Li, Hao; Guo, ShijunThis study investigates the aerodynamic efficiency of a bioinspired flapping wing rotor kinematics which combines an active vertical flapping motion and a passive horizontal rotation induced by aerodynamic thrust. The aerodynamic efficiencies for producing both vertical lift and horizontal thrust of the wing are obtained using a quasi-steady aerodynamic model and two-dimensional (2D) CFD analysis at Reynolds number of 2500. The calculated efficiency data show that both efficiencies (propulsive efficiency-ηp, and efficiency for producing lift-Pf) of the wing are optimized at Strouhal number (St) between 0.1 and 0.5 for a range of wing pitch angles (upstroke angle of attack αu less than 45°); the St for high Pf (St = 0.1 ∼ 0.3) is generally lower than for high ηp (St = 0.2 ∼ 0.5), while the St for equilibrium rotation states lies between the two. Further systematic calculations show that the natural equilibrium of the passive rotating wing automatically converges to high-efficiency states: above 85% of maximum Pf can be obtained for a wide range of prescribed wing kinematics. This study provides insight into the aerodynamic efficiency of biological flyers in cruising flight, as well as practical applications for micro air vehicle design.Item Open Access Aeroelastic investigation of conventional fixed wings and bio-inspired flapping wings by analysis and experiment.(2018-09) Li, Hao; Guo, Shijun J.In this thesis, the structure and aeroelastic design, analysis and optimization of conventional fixed wing is firstly addressed. Based on the study results of conventional fixed wing, the study then focuses on the more complicated aerodynamics and aeroelasticity of flapping wing Micro Air Vehicles (MAV). A Finite Element (FE) model of a composite aircraft wing is firstly used as case study for the aeroelasticity of conventional fixed wing. A MATLAB-NASTRAN interfaced optimization platform is created to explore the optimal design of the wing. Optimizations using the developed platform show that 13% of weight reduction can be achieved when the optimization objective is set to minimize wing weight; and 18.5% of flutter speed increase can be achieved when aeroelastic tailoring of composite laminate layups is carried out. The study results further showed that the most sensitive part of the wing for aeroelastic tailoring is near the engine location, which contributes to the majority of flutter speed increment for optimization. In order to facilitate the structural design of non-circular cross section fuselage of Blended-Wing-Body (BWB) aircraft, an analytical model of 2D non-circular cross section is developed, which provides efficient design and optimization of the fuselage structure without referring to FE models. A case study based on a typical BWB fuselage using the developed model shows that by optimizing the fuselage structure, significant weight saving (17%) can be achieved. In comparison with the conventional fixed wing, insect flapping wings demonstrate more complicated aerodynamic and aeroelastic phenomena. A semi-empirical quasi-steady aerodynamic model is firstly developed to model the unsteady aerodynamic force of flapping wing. Based on this model, the aerodynamic efficiency of a Flapping Wing Rotor (FWR) MAV is investigated. The results show that the optimal wing kinematics of the FWR falls into a narrow range of design parameters governed by the dimensionless Strouhal number (St). Furthermore, the results show that the passive rotational of the FWR converges to an equilibrium state of high aerodynamic efficiency, which is a desirable feature for MAV applications. Next, the aerodynamic lift coefficient and efficiency of the FWR are calculated and compared with typical insect-like flapping wings and rotary wing. The results show that the aerodynamic efficiency of FWR in typical wing kinematics is higher than insect-like flapping wings, but slightly lower than the conventional rotary wing; the FWR aerodynamic lift coefficient (CL) surpassed the other wings significantly. Based on the numerical results, the study then continued to experimental investigations of the FWR. A prototype FWR model of weight 2.6g is mounted on a load cell to measure the instantaneous lift production. The kinematics of the wing is captured using high speed camera. Aeroelastic twist of the wing is measured using the resulting wing motion. Analyses by CFD and the quasi-steady aerodynamic model is then carried out and compared with experimental results. The study revealed that passive twist of the FWR wing due to aeroelastic effects forms desirable variations of wing Angle of Attack (AoA), which improves the aerodynamic performance of FWR. The results of the thesis provide guidance for structural, aerodynamic and aeroelastic design, analysis and optimization of conventional fixed wing, as well as bio-inspired flapping wing MAVs.Item Open Access Effects of fiber orientation on tool wear evolution and wear mechanism when cutting carbon fiber reinforced plastics(Elsevier, 2022-09-07) Wu, Weizhou; Li, Shipeng; Qin, Xuda; Liu, Wentao; Cui, Xin; Li, Hao; Shi, Mengrui; Liu, HaibaoThe aim of the present paper is to reveal the influence of different fiber orientations on the tool wear evolution and wear mechanism. Side-milling experiments with large-diameter milling tools are conducted. A finite element (FE) cutting model of carbon fiber reinforced plastics (CFRP) is established to get insight into the cutting stress status at different wear stages. The results show that different fiber orientations bring about distinct differences in the extent, profile and mechanism of tool wear. Severer wear occurs when cutting 45° and 90° plies, followed by 0°, correspondingly, the least wear is obtained when θ = 135° (θ represents the orientation of fibers). Moreover, the worn profiles of cutting tools when θ = 0° and 45° are waterfall edge, while round edge occurs when θ = 135° and a combined shape of waterfall and round edge is obtained when θ = 90°. The wear mechanisms under different fiber orientations are strongly dependent on the cutting stress distributions. The evolution of tool wear profile is basically consistent with the stress distribution on the tool surface at different wear stages, and the extent of tool wear is determined by the magnitude of stress on the tool surface. Besides, the worn edges produce an actual negative clearance angle, which decreases the actual cutting thickness and leads to compressing and bending failure of fibers beneath the cutting region as well as low surface qualities.Item Open Access Nonlinear dynamics of a flapping rotary wing: Modeling and optimal wing kinematic analysis(Elsevier, 2018-03-13) Wen, Qiuqiu; Guo, Shijun; Li, Hao; Dong, WeiThe analysis of the passive rotation feature of a micro Flapping Rotary Wing (FRW) applicable for Micro Air Vehicle (MAV) design is presented in this paper. The dynamics of the wing and its influence on aerodynamic performance of FRW is studied at low Reynolds number (∼103). The FRW is modeled as a simplified system of three rigid bodies: a rotary base with two flapping wings. The multibody dynamic theory is employed to derive the motion equations for FRW. A quasi-steady aerodynamic model is utilized for the calculation of the aerodynamic forces and moments. The dynamic motion process and the effects of the kinematics of wings on the dynamic rotational equilibrium of FWR and the aerodynamic performances are studied. The results show that the passive rotation motion of the wings is a continuous dynamic process which converges into an equilibrium rotary velocity due to the interaction between aerodynamic thrust, drag force and wing inertia. This causes a unique dynamic time-lag phenomena of lift generation for FRW, unlike the normal flapping wing flight vehicle driven by its own motor to actively rotate its wings. The analysis also shows that in order to acquire a high positive lift generation with high power efficiency and small dynamic time-lag, a relative high mid-up stroke angle within 7–15° and low mid-down stroke angle within −40° to −35° are necessary. The results provide a quantified guidance for design option of FRW together with the optimal kinematics of motion according to flight performance requirement.Item Open Access Optimization of multi-tooth milling tool for interlaminar damage suppression in the milling of carbon fiber–reinforced polymers(Springer, 2022-05-27) Liu, Jian; Tang, Xinkai; Li, Shipeng; Qin, Xuda; Li, Hao; Wu, Weizhou; Srijana, Yadav; Liu, Wentao; Liu, HaibaoCarbon fiber–reinforced polymers (CFRP) are widely utilized in the aerospace field due to their significant specific strength, specific modulus, and strong design ability. However, anisotropy and low interlaminar bonding strength lead to burr, tear, lamination, and other damages in CFRP machining. In this paper, a 3D finite element model for the milling of CFRP was carefully developed, and the cutting forces, the interlaminar stress, and the interlaminar damage were properly obtained. Typically based on the developed model, the effects of geometric parameters of the multi-tooth milling tool were precisely analyzed. Next tool geometries were optimized for suppressing the interlaminar damage in the milling of CFRP. Results convincingly show that the multi-tooth milling tool with the geometry of 1.4 mm length of the micro tooth, 38.2° left helix angle, 11 left-handed chip grooves, 15° right helix angle, 12 right-handed helix grooves, approximately rectangular of section shape of the chip groove, 10° rake angle, and 15° clearance angle efficiently delivers the optimal performance. Besides, cutting performance of numerous coated tools was also studied. Results typically show that the multi-tooth milling tool with a diamond coating maintains significant advantages in aspects of the tool life and costs compared with the uncoated and diamond-like carbon coating (DLC)-coated tools.Item Open Access Peridynamic modeling of mode-I delamination growth in double cantilever composite beam test: a two-dimensional modeling using revised energy-based failure criteria(MDPI, 2019-02-15) Jiang, Xiao-Wei; Guo, Shijun; Li, Hao; Wang, HaiThis study presents a two-dimensional ordinary state-based peridynamic (OSB PD) modeling of mode-I delamination growth in a double cantilever composite beam (DCB) test using revised energy-based failure criteria. The two-dimensional OSB PD composite model for DCB modeling is obtained by reformulating the previous OSB PD lamina model in x–z direction. The revised energy-based failure criteria are derived following the approach of establishing the relationship between critical bond breakage work and energy release rate. Loading increment convergence analysis and grid spacing influence study are conducted to investigate the reliability of the present modeling. The peridynamic (PD) modeling load–displacement curve and delamination growth process are then quantitatively compared with experimental results obtained from standard tests of composite DCB samples, which show good agreement between the modeling results and experimental results. The PD modeling delamination growth process damage contours are also illustrated. Finally, the influence of the revised energy-based failure criteria is investigated. The results show that the revised energy-based failure criteria improve the accuracy of the PD delamination modeling of DCB test significantly.Item Open Access Recent advances in carbon dioxide utilization(Elsevier, 2020-03-12) Zhang, Zhien; Pan, Shu Yuan; Li, Hao; Cai, Jianchao; Olabi, Abdul Ghani; Anthony, Ben; Manovic, VasilijeCarbon dioxide (CO2) is the major contributor to greenhouse gas (GHG) emissions and the main driver of climate change. Currently, CO2 utilization is increasingly attracting interest in processes like enhanced oil recovery and coal bed methane and it has the potential to be used in hydraulic fracturing processes, among others. In this review, the latest developments in CO2 capture, utilization, conversion, and sequestration are examined through a multi-scale perspective. The diverse range of CO2 utilization applications, including mineralization, biological utilization, food and beverages, energy storage media, and chemicals, is comprehensively presented. We also discuss the worldwide research and development of CO2 utilization projects. Lastly, we examine the key challenges and issues that must be faced for pilot-scale and industrial applications in the future. This study demonstrates that CO2 utilization can be a driver for the future development of carbon capture and utilization technologies. However, considering the amount of CO2 produced globally, even if it can be reduced in the near-to mid-term future, carbon capture and storage will remain the primary strategy and, so, complementary strategies are desirable. Currently, the main CO2 utilization industry is enhanced oil and gas recovery, but considering the carbon life cycle, these processes still add CO2 to the atmosphere. In order to implement other CO2 utilization technologies at a large scale, in addition to their current technical feasibility, their economic and societal viability is critical. Therefore, future efforts should be directed toward reduction of energy penalties and costs, and the introduction of policies and regulation encouraging carbon capture, utilization and storage, and increasing the public acceptance of the strategies in a complementary manner.Item Open Access Short landing performance and scale effect of a flapping wing aircraft(ASCE, 2020-09-15) Chen, Si; Guo, Shijun; Li, Hao; Tong, Mingbo; Ji, BingAn investigation was made into the performance and scale effect of birdlike flapping wing aircraft in short landing. A flapping mechanism is proposed to transform a powered shaft rotation to an optimal kinematics of wing motion combining up-and-down stroke, pitching, and fore-and-back swing. An unsteady aerodynamic method (UAM) was developed based on potential flow theory, including the leading- and trailing-edge vortices generated by a flapping wing. After validation based on computational fluid dynamics (CFD) results, the method is used to calculate the aerodynamic forces of flapping wings. The flight dynamics model of the aircraft is built using Automated Dynamic Analysis of Mechanical Systems (ADAMS) software version 2012 interfacing with the UAM coded in Python. The coupling between the inertial force of the body motion and the aerodynamic forces from flapping wings and tailplane is incorporated into the numerical simulation of the aircraft landing. Taking a 0.196-kg birdlike aircraft model with a prescribed kinematics of flapping wing motion as an example, a parametric study was carried out in a small range of initial tailplane angles and subsequent flapping frequencies. Optimal parameters were obtained to reduce the forward and descending velocities of the aircraft to a minimum value for safe and short landing performance. The study is then extended to aircraft of different geometric scales in a range of 0.5–10 associated with a weight scale of 0.1–1,000. Based on the study, a method is developed to determine the required flapping frequency for birdlike aircraft of different scales to achieve a short landing target with the descending velocity reduced to a specified value. For the aforementioned example aircraft (geometric scale of 1), the flapping frequency is 4 Hz to reduce both descending and forward velocities to 50% of the landing performance in fixed-wing mode, while a birdlike aircraft on a geometric scale of 10 and landing weight of 196 kg requires a minimum flapping frequency of 1.25 Hz to achieve a 50% reduction of the descending and forward velocities compared with the same aircraft landing in fixed-wing mode.Item Open Access Unsteady aerodynamic model of flexible flapping wing(Elsevier, 2018-08-17) Chen, Si; Li, Hao; Guo, Shijun; Tong, Mingbo; Ji, BingBio-inspired flapping wing has potential application to micro air vehicles (MAV). Due to the nature of lightweight and flexibility of micro flapping wing structures, elastic deformation as a result of aeroelastic coupling is inevitable in flapping motion. This effect can be significant and beneficial to the aerodynamic performance as revealed in the present investigation for a flexible flapping wing of variable camber versus a rigid one. Firstly a two dimensional (2D) unsteady aerodynamic model (UAM) based on potential flow theory has been extended from previous study. Both leading and trailing edge discrete vortices are included in the model with unsteady Kutta condition satisfied to fully characterize the unsteady flow around a flapping wing. A wall function is created to modify the induced velocity of the vortices in the UAM to solve the vortices penetration problem. The modified UAM is then validated by comparing with CFD results of a typical insect-like flapping motion from previous research. Secondly the UAM is further extended for a flexible flapping wing of camber variation. Comparing with a rigid wing in a prescribed plunging and pitching motion, the results show lift increase with positive camber in upstroke by mitigating negative lift. The results also agree well with CFD simulation. Thirdly the 2D UAM is extended to calculate the aerodynamic forces of a 3D wing with camber variation, and validated by CFD results. Finally the model is applied to aerodynamic analysis of a 3D flexible flapping wing with aeroelastic coupling effect. Significant increase of lift coefficient can be achieved for a flexible flapping wing of positive camber and twist in upstroke produced by the structure elastic deformation.