Browsing by Author "Guo, Shijun"
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Item Open Access 3D-printed thermoplastic composite fasteners for single lap joint reinforcement(Elsevier, 2021-12-10) Li, Wenhao; Guo, Shijun; Giannopoulos, Ioannis K.; Lin, Minxiao; Xiong, Yi; Liu, Yiding; Shen, ZhengquanThis study presents findings for the strength and failure mechanism of a 3D-printed Continuous Carbon Fibre reinforced Onyx (CCF/Onyx) Thermo-Plastic Composite Fastener (TPCF) and a single lap-joint (SLJ) made of fibre/polymer composite reinforced by the TPCF. The study was carried out by numerical analysis and experiment methods including test sample design, manufacturing process and mechanical test. The 3D-printed fasteners were manufactured and tested in shear mode for two types of joining arrangement: fastened and hybrid bonded/fastened joints. Firstly, experiment was carried out for the TPCF fastened SLJ and the results show that addition of CCF in the Onyx matrix and post heat-treatment process could significant enhance the TPCF strength. The results was then benchmarked against a SLJ with steel fastening. The shear failure load of the SLJ reinforced by heat-treated CCF/Onyx TPCF of 8mm diameter was 36% lower than a SLJ reinforced by a steel bolt of the same size. Numerical model for progressive damage simulation was also created based on the failure theory from Puck and Schürmann achieving good correlation with the experimental data. Secondly, the TPCF fasteners were manufactured with two types of heat-treated countersunk head and pan head forming and used to reinforce bonded SLJ. The test results show that the bonded SLJ reinforced by the TPCF fastener of countersunk head is of 11.7% higher strength and an increase in ultimate deformation by 9.1% compared to a bonded SLJ reinforced by steel fastener of 5mm diameter. From the numerical and experimental study, it was noted that this was attributed to countersunk configuration to reduce out-out-plane bending and provide better crack arresting for the joint bonding.Item Open Access Aerodynamic analysis of a flapping wing aircraft for short landing(MDPI, 2020-05-14) Ji, Bing; Zhu, Zenggang; Guo, Shijun; Chen, Si; Zhu, Qiaolin; Li, Yushuai; Yang, Fan; Song, Rui; Li, YibinAn investigation into the aerodynamic characteristics has been presented for a bio-inspired flapping wing aircraft. Firstly, a mechanism has been developed to transform the usual rotation powered by a motor to a combined flapping and pitching motion of the flapping wing. Secondly, an experimental model of the flapping wing aircraft has been built and tested to measure the motion and aerodynamic forces produced by the flapping wing. Thirdly, aerodynamic analysis is carried out based on the measured motion of the flapping wing model using an unsteady aerodynamic model (UAM) and validated by a computational fluid dynamics (CFD) method. The difference of the average lift force between the UAM and CFD method is 1.3%, and the difference between the UAM and experimental results is 18%. In addition, a parametric study is carried out by employing the UAM method to analyze the effect of variations of the pitching angle on the aerodynamic lift and drag forces. According to the study, the pitching amplitude for maximum lift is in the range of 60°~70° as the flight velocity decreases from 5 m/s to 1 m/s during landing.Item Open Access Aerodynamic analysis of insect-like flapping wings in fan-sweep and parallel motions with the slit effect(Elsevier, 2022-05-23) Zhu, Zenggang; Zhao, Jingtai; He, Yuanyuan; Guo, Shijun; Chen, Si; Ji, BingIn this study, the aerodynamic performance of flapping wings using a parallel motion was investigated and compared with the insect-like “fan-sweep” motion, and the effect of adding a slit to the wings was analyzed. First, numerical simulations were performed to analyze the wing aerodynamics of two flapping motions with equivalent stroke amplitudes over a range of pitching angles based on computational fluid dynamics (CFD). The simulation results indicated that flapping wings with a rapid and short parallel motion achieved better lift and efficiency than those of the fan-sweep motion while maintaining the same aerodynamic characteristics regarding stall delay and leading-edge vortices. For a parallel motion with a pitching angle of 25° and 100 mm stroke amplitude, the wings generated an average lift of 8.4 gf with a lift-to-drag ratio of 1.06, respectively, which were 1.8% and 26% greater than those of the fan-sweep motion with a corresponding 96° stroke amplitude. This situation was reversed when the pitching angle and stroke amplitude were increased to 45° and 144° for the fan-sweep motion, which was equivalent to the parallel motion with a 150 mm stroke amplitude. The slit effect in the parallel motion was also evaluated, and the CFD results indicated that a slit width of 1 mm (1/50 wing chord) increased the lift of the wing by approximately 27% in the case of the 150 mm stroke amplitude. Further, the slit width slightly influenced the lift and aerodynamic efficiency.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 Aerodynamic performance of a flyable flapping wing rotor with dragonfly-like flexible wings(Elsevier, 2024-03-29) Pan, Yingjun; Guo, Shijun; Whidborne, James F.; Huang, XunDrawing inspiration from insect flapping wings, a Flapping Wing Rotor (FWR) has been developed for Micro Aerial Vehicle (MAV) applications. The FWR features unique active flapping and passive rotary kinematics of motion to achieve a high lift coefficient and flight efficiency. This study thoroughly investigates the aerodynamic performance and design of a bio-inspired flexible wing for FWR-MAVs, emphasizing its novel backward-curved wingtip and variable spanwise stiffness resembling a dragonfly's wing. The research departs from previous aerodynamic studies of FWR, which focused predominantly on rectangular and rigid wings, and delves into wing flexibility. Employing Computational Fluid Dynamics (CFD), Computational Structural Dynamics (CSD), and experimental measurements, the study demonstrates the aerodynamic benefits of the dragonfly-inspired FWR wingtip shape and its reinforced structure. Fluid-Structure Interaction (FSI) analysis is used to examine the effects of elastic deformation encompassing twist and bending on aerodynamic forces. The results underscore the importance of bending deformation in enhancing lift and power efficiency and propose a method for analysing variable stiffness along the wingspan using a vortex delay mechanism that is induced by delayed flapping motion. By comparing modelled and measured stiffness, the study validates the flexibility of the FWR wing, revealing optimal aerodynamic efficiency is achieved through moderate flexibility and spanwise stiffness variation. The curving leading-edge beam forming the sweep-back wingtip offers a practical approach to obtaining variable stiffness and aerodynamic benefits for FWR-MAVs. Using the same pair of dragonfly-like flexible wings, FWR-MAVs have effectively exhibited VTOL and hovering flight capabilities, spanning from a 25-g single-motor drive model to a 51-g dual-motor drive model. This research provides valuable insights into flexible wing design for FWR-MAVs, leveraging biomimicry to improve flight efficiency.Item Open Access Backstepping control with fixed-time prescribed performance for fixed wing UAV under model uncertainties and external disturbances(Taylor and Francis, 2020-10-15) Tan, Jian; Guo, ShijunIn this paper, a novel backstepping control scheme with fixed-time prescribed performance is proposed for the longitudinal model of fixed wing UAV subject to model uncertainties and external disturbances. The novel performance function with arbitrarily preassigned fixed-time convergence property is developed, which imposes priori performance envelops on both altitude and airspeed tracking errors. By using error transformed technology, the constrained fixed-time performance envelops are changed into unconstrained equivalent errors. Based on modified error compensation mechanism, a novel backstepping approach is proposed to guarantee altitude tracking equivalent error converges to the specified small neighborhood and presents excellent robustness against model uncertainties and external disturbances, and airspeed controller with fixed-time prescribed performance is designed. The proposed methodology guarantees the transient and steady-state performance of altitude and airspeed tracking errors within constrained fixed-time performance envelops in spite of lumped disturbances. Finally, numerical simulations are used to verify the effectiveness of the proposed control schemeItem Open Access A bio-inspired flapping wing rotor of variant frequency driven by ultrasonic motor(MDPI, 2020-01-06) Chen, Si; Wang, Le; Guo, Shijun; Zhao, Chunsheng; Tong, MingboBy combining the flapping and rotary motion, a bio-inspired flapping wing rotor (FWR) is a unique kinematics of motion. It can produce a significantly greater aerodynamic lift and efficiency than mimicking the insect wings in a vertical take-off and landing (VTOL). To produce the same lift, the FWR’s flapping frequency, twist angle, and self-propelling rotational speed is significantly smaller than the insect-like flapping wings and rotors. Like its opponents, however, the effect of variant flapping frequency (VFF) of a FWR, during a flapping cycle on its aerodynamic characteristics and efficiency, remains to be evaluated. A FWR model is built to carry out experimental work. To be able to vary the flapping frequency rapidly during a stroke, an ultrasonic motor (USM) is used to drive the FWR. Experiment and numerical simulation using computational fluid dynamics (CFD) are performed in a VFF range versus the usual constant flapping frequency (CFF) cases. The measured lifting forces agree very well with the CFD results. Flapping frequency in an up-stroke is smaller than a down-stroke, and the negative lift and inertia forces can be reduced significantly. The average lift of the FWR where the motion in VFF is greater than the CFF, in the same input motor power or equivalent flapping frequency. In other words, the required power for a VFF case to produce a specified lift is less than a CFF case. For this FWR model, the optimal installation angle of the wings for high lift and efficiency is found to be 30° and the Strouhal number of the VFF cases is between 0.3–0.36. View Full-TextItem Open Access Composites joints reinforced by composite rivets(Asranet, Glasgow, 2018-05-08) Li, Wenhao; Guo, Shijun; Giannopoulos, Ioannis K.This paper presents an investigation into the mechanical behaviour of composite joints reinforced by using a novel composite rivet made of rolled laminates. Two typical joints have been modelled using three-dimensional solid finite element model in the study. The first type is a composites single lap joint bonded and reinforced by a composite rivet compared with the joint reinforced by a titanium bolt subjected to tensile load. The results are also compared with an adhesive bonded joint as reference. The second type of joint model is a wing box section with skin-rib joint reinforced by composite rivet subjected to a pulling load. A range of adhesive damage was modelled up to 50% (undamaged WBDM, WBDM I 16%, WBDM II 33% and WBDM III 50% respectively) of the bonding area. The results show that the rivets located in the regions where the adhesive bonding failed will carry higher stress and make more contribution to the structure integrity. Although the titanium rivets provide better mechanical performance to carry more load, composite rivets offer an alternative adequate reinforcement to delay the bonding failure and safeguard the structure.Item Open Access Damage tolerance of CFRP airframe bolted joints in bearing, following bolt pull-through failure(Elsevier, 2020-01-15) Giannopoulos, Ioannis K.; Grafton, Kaelan; Guo, Shijun; Smith, HowardThe experimental study presented herein, investigated the residual strength of bolted joints on Carbon Fiber Reinforced Polymer (CFRP) airframe structures within the context of structural damage tolerance and airworthiness regulations. The damage scenario assumed, subjected a series of bolted joint CFRP laminate specimens to quasi-static bearing loading, following bolt pull-through failure events of different magnitude. Representative CFRP laminate specimens manufactured from AS7/8552 carbon fiber/epoxy matrix system were artificially damaged under bolt pull-through loading, following the herein proposed modifications to the current pull-through ASTM testing procedure. The specimens were subsequently tested in static bearing loading for examining the specimen residual bearing strength. The residual joint bearing strength was related to the displacement travelled passed the initial failure stage in pull-through mode and was measured up to a maximum of a 13% decrease for the tested samples and the maximum damage imposed. The study explored the safe utilization of bolted joints at higher operating loading levels, within the context of the current airworthiness regulations. The inherent damage arrest features of the joints were highlighted. The study concluded with comments and suggestions on the expansion of the current utilization spectrum of damaged bolted joints from pull-through loading in airframe design, bound by the current airworthiness certification requirements.Item Open Access Design and experiment of a bionic flapping wing mechanism with flapping–twist–swing motion based on a single rotation(AIP Publishing, 2020-06-12) Ji, Bing; Zhu, Qiaolin; Guo, Shijun; Yang, Fan; Li, Yushuai; Zhu, Zenggang; Chen, Si; Song, Rui; Li, YibinIn the present study, a bionic flapping mechanism of a spatial six-bar configuration was designed to transform a single rotation of a motor into a three degrees of freedom “flapping–twist–swing” cooperative motion of a flapping wing. The kinematics model of the flapping mechanism movement was constructed. The flapping trajectory of the wing based on the kinematics model was to mimic the motion of a pigeon wing in landing flight. To reduce the manufacturing complexity, the flapping mechanism was simplified with only two degrees of freedom (flapping and twist) retained. Finally, a prototype model with a 0.9 m wing span was built and tested. A comparison among the experimental data, theoretical calculation results, and ADAMS simulation results revealed that the difference in the flapping and the twist amplitude between experimental observations and theoretical calculation results was 12.5% and 2.3%, respectively. This was owing to the elastic deformation of the bar and the mechanism simplification. The comparison results also indicated that the maximum difference in the inertial force was 5.9% in up-stroke and 6.7% in down-stroke, respectively. The experimental results showed that the inertial force of the model with the wing patagium was approximately 2.2 N, and the maximum positive and negative lift was 2.1 N and −1.5 N, respectively. It is hoped that this study can provide guidance for the design of bionic flapping wing mechanisms of a flapping wing aircraft for short landing flight.Item Open Access Effect of asymmetric feathering angle on the aerodynamic performance of a flyable bionic flapping-wing rotor(MDPI, 2023-03-18) Chen, Si; Wang, Le; Guo, Shijun; Tong, Mingbo; He, YuanyuanThe current study involves an experimental as well as numerical study on the aerodynamic behavior of a flapping-wing rotor (FWR) with different feathering amplitudes (−20°–50°, −50°–20°, and −35°–35°). In order to fulfil the experimental test, an FWR which weighs 18.7 g is designed in this manuscript. According to the experimental and numerical results, it was observed that, compared with the cases under a zero average stroke angle, the cases under a positive average stroke angle or negative average stroke angle share a higher rotary speed given the same input voltage. Despite the fact that the negative average stroke angle would facilitate the generation of a higher rotary speed, the negative average stroke angle cases tend to generate the smallest lift-to-power ratio. On the other hand, the cases with a positive average stroke angle tend to share the largest lift-to-power ratio (about 1.25 times those of zero average stroke angle cases and about 1.6 times those of negative average stroke angle cases). The above study indicates that the application of a positive average stroke angle can provide an effective solution to further increase the aerodynamic performance of a bio-inspired FWR.Item Open Access Flow field calculation and dynamic characteristic analysis of spherical hybrid gas bearings based on passive grid(Springer, 2019-01-03) Jia, Chenhui; Cui, Zhiwu; Guo, Shijun; Qiu, Ming; Ma, WensuoIn order to research the spherical spiral groove hybrid gas bearings, the Realizable k − ε turbulence model of gas film was established based on FLUENT. The simulation calculation method of 6-degrees of freedom passive grid was used, which can simulate the lubrication characteristics of the gas film transient flow field accurately. And the gas film pressure distribution and dynamic characteristic coefficients are numerically calculated. The dynamic and static pressure coupling effects of the gas flow field were analyzed, and the axis motion trajectory was simulated. The effect of rotation speed, gas supply pressure and tangential angle on the dynamic characteristic coefficients during bearing operation was analyzed. And the stability of the gas bearing was studied. The conclusion from the analysis shows that different rotation speed and gas supply pressure will change the pressure distribution of the gas bearing during the operation. The dynamic characteristics of the gas film can be changed by reasonably optimizing the operation parameters, which can change the whirl characteristics of the gas film and improve the stability. Through calculation and analysis, the tangential angle is selected between 55° and 60°, to ensure that the gas film has a high stiffness, while it also can obtain the larger damping. The simulation results and the experimental results are compared and analyzed to verify the correctness and effectiveness of the simulation method. At the same time, the research of this paper provided a theoretical basis for optimizing the bearing structure and operating parameters, improving the dynamic characteristics of gas bearings and improving the operation stability.Item Open Access Gust response and body freedom flutter of a flying-wing aircraft with a passive gust alleviation device(Elsevier, 2017-08-14) Guo, Shijun; Jing, Z. W.; Li, H; Lei, W. T.; He, Yuan YuanThe effectiveness of a passive gust alleviation device (PGAD) mounted at the wingtip of aircraft in conventional and flying-wing configurations have been studied in previous research. However the PGAD influence on the aeroelastic stability in particular the body freedom flutter (BFF) of a flying-wing aircraft remains as a concern. This present investigation is focused on evaluating the beneficial effect of PGAD on both gust load alleviation and BFF of a small flying-wing aircraft of high aspect ratio wing made of composite. A small range of (1-cos) type of gust load has been considered to select a representative critical gust load case for the study. A parametric study indicates that there is a narrow band of optimal key parameters for the PGAD design. Subsequently a set of optimal parameters is selected to further the analysis of the PGAD mechanism. The case study results show that the PGAD can make the bending moment at the wing root due to gust reduced by 16%. In addition, the BFF speed of the flying-wing aircraft is increased by 4.2%. The investigation reveals that the PGAD mode and its interaction with the wing bending mode and short period oscillation of the aircraft can have beneficial aeroelastic effect on both gust alleviation and flutter suppression.Item Open Access Identification of the key design inputs for the FEM-based preliminary sizing and mass estimation of a civil aircraft wing box structure(Elsevier, 2021-12-14) You, Chao; Yasaee, Mehdi; He, Shun; Yang, Daqing; Xu, Yigeng; Dayyani, Iman; Ghasemnejad, Hessam; Guo, Shijun; Webb, Phil; Jennings, James; Federico, GiovanniFEM-based preliminary structural sizing has been successfully carried out for a typical single-aisle wing box structure using MSC Nastran, by considering various load cases representing typical aircraft manoeuvres, engine loads, landing and ground handling conditions. The strength, buckling and fatigue criteria have been applied as the design constraints for sizing. The resultant total mass and the structural (static and modal) behaviour of the sized wing box model have been verified against a validated high-fidelity wing box model. A sensitivity analysis has been performed to evaluate the influence of the number of design fields and the selected design inputs (i.e. load cases and design constraints) on the accuracy of sizing and mass estimation of the wing box. This sensitivity analysis has also been extended to the static and modal behaviour of the wing box structure obtained from sizing. It provides an insight into the significance of considering the buckling and fatigue constraints, aircraft rolling loads, engine loads and landing loads in sizing, in addition to the commonly-applied 2.5 g aircraft pull-up loads under the strength constraint. The findings of this study highlight the trade-off between the sizing efficiency and accuracy of a civil aircraft wing for modelling purposes.Item Open Access Lightweight photovoltaic composite structure on stratospheric airships(Hindawi, 2018-12-12) Zhang, Xinyun; Sun, Kangwen; Xu, Dongdong; Guo, ShijunA semirigid solar array is an efficient energy system on the surface of stratospheric airships for utilizing the solar energy, which we believe that it has succeeded in providing some impressive results for conceptual design. This paper developed a lightweight photovoltaic composite structure (LPCS) according to the characteristics of the stratospheric airship capsule. In order to improve the flexibility of the solar cell, we studied the mechanical properties in the different thicknesses of the honeycomb core for LPCS by FEM software and three-point bending test, and we also launched experiments to measure the temperature difference between upper and lower surfaces of the LPCS test samples under different solar radiation flux conditions. The experimental data were examined to evaluate the mechanical properties and thermal insulation performances of LPCS. Considering the quality of the whole structure, the paper finally comes up with the conclusion of the optimal thickness of the honeycomb core with further detailed descriptions.Item Open Access Modelling and simulation of a novel bioinspired flapping-wing rotary MAV(German Society for Aeronautics and Astronautics (DGLR: Deutsche Gesellschaft für Luft- und Raumfahrt), 2023-09-07) Huang, Xun; Lu, Linghai; Whidborne, James F.; Guo, ShijunAchieving high lift efficiency represents a major research focus in the Micro Air Vehicle (MAV) domain due to stringent size and payload constraints. The Cranfield research team presents a novel semi-biomimetic design called the Flapping Wing Rotor (FWR) to address this challenge. This innovative concept combines a bioinspired flapping wing mechanism with passive rotor rotation, leveraging unsteady aerodynamic principles analogous to insect flight. The research aims to highlight a promising biomimetic flapping-rotor MAV enabled through advanced modeling to unlock the benefits of bio-inspired unsteady aerodynamics. To demonstrate this approach, a 60g proof-of-concept prototype was developed alongside a digital twin methodology for modeling, simulation, and control. A mathematical model has been formulated to analyze FWR's lift generation performance and enable flight control system design for stabilization and controllability. This work concentrates on enhancing the physical modeling process. The model is refined by tuning two key aerodynamic coefficients to account for nonlinearities from unsteady aerodynamics, flexible structures, and low Reynolds number flow inherent in MAV flight. This improved model achieves superior lift prediction accuracy versus real flight test data. Ongoing efforts focus on optimizing control torque, load distribution, and stability to further augment FWR's flight capabilities.Item Open Access Nonlinear aeroelastic behavior of an airfoil with free-play in transonic flow(Elsevier, 2019-12-16) He, Shun; Guo, Shijun; Li, Wenhao; Yang, Daqing; Gu, Yingsong; Yang, ZhichunAn investigation has been made into the nonlinear aeroelastic behavior of an airfoil system with free-play nonlinear stiffness in transonic flow. Computational Fluid Dynamics (CFD) and Reduced Order Model (ROM) based on Euler and Navier-Stokes equations are implemented to calculate unsteady aerodynamic forces. Results show that the nonlinear aeroelastic system experiences various bifurcations with increasing Mach number. Regular subcritical bifurcations are observed in low Mach number region. Subsequently, complex Limit Cycle Oscillations (LCOs) and even non-periodic motions appear at specific airspeed regions. When the Mach number is increased above the freeze Mach number, regular subcritical bifurcations occur again. Comparisons with inviscid solutions are used to identify and elaborate the effect of viscosity with the help of aeroelastic analysis techniques, including root locus, Single Degree of Freedom (SDOF) flutter and aerodynamic influence coefficient (AIC). For low Mach numbers in the transonic regime, the viscosity has little effect on the linear flutter characteristic because of limited influence on AIC, but a remarkable impact on the nonlinear dynamic behavior due to the sensitivity of the nonlinear structure. As the Mach number increases, the viscosity becomes significantly important due to the existence of shock-boundary layer interaction. It affects the unstable mechanism of linear flutter, impacts the aerodynamic center and hence the snap-through phenomenon, influences the AIC and consequently the nonlinear aeroelastic response. When the Mach number is increased further, the shock wave dominates the air flow and the viscosity is of minor importance.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 Passive gust alleviation of a flying-wing aircraft by analysis and wind-tunnel test of a scaled model in dynamic similarity(Elsevier, 2021-03-29) He, Shun; Guo, Shijun; Liu, Ying; Luo, WukuiAn investigation was conducted to evaluate the effectiveness of a passive gust alleviation device (PGAD) installed in a flying-wing aircraft of 62.3m wing span at large swept back angle. It was performed by numerical analysis and validated by wind-tunnel test of a 1:25 reduced scale physical model of dynamic similarity to the full-scale aircraft. The 1-cosine gust model with a range of gust parameters specified in the airworthiness regulation CS-23 was taken in the gust response analysis that led to 7~9% gust alleviation results by employing the PGAD. The gust response dominated by the first three modes of the aircraft was most critical in the frequency close to the first bending mode of the wing. The wind-tunnel test model was designed and manufactured based on dynamic scaling law, and proved to be of excellent dynamic similarity by the deviation of less than 5.5% between the first three modes of the physical model measured by vibration test and the full-scale aircraft model. The wind tunnel test results show that the gust response of the model in the specified range was reduced by 8.3~14.3% according to the measured wing tip deflection associated with the PGAD oscillation amplitude at 4.0°~15.5°. The present study shows that the numerical analysis of gust response and alleviation of a full-scale aircraft installed with PGAD can be validated by wind tunnel test of a scaled physical model with dynamic similarity.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.