Rotor-to-rotor interaction among neighboring rotors of a multirotor has great significance for aerodynamically efficient multirotor design. Current research is conducted to analyze aerodynamic performance of different...Rotor-to-rotor interaction among neighboring rotors of a multirotor has great significance for aerodynamically efficient multirotor design. Current research is conducted to analyze aerodynamic performance of different octocopter configurations amid hover and forward flight. Conventional and coaxial configurations are studied and a hybrid configuration is also proposed to rectify the disadvantages associated with the earlier two. Comparison is carried out for the aforementioned configurations along with comparison of coaxial and hybrid octocopters with bigger diameter rotors in the same confined space for high thrust requirement missions. Vertical spacing of coaxial configuration is also studied. Virtual Blade Method (VBM) is considered herein due to its great computational efficiency. The results show that there are 11.89% and 14.22% loss in thrust for coaxial octocopter compared to conventional and hybrid configurations with normal size rotors and 15.61% loss compared to hybrid configuration with bigger rotors in hover, whereas coaxial square configuration performs the worst in forward flight with a lift loss of 9.1%, 14.77% and 18.8% compared to coaxial diamond, conventional and hybrid configurations with normal size rotors and 9.96% and 17.82% loss compared to coaxial diamond and hybrid configurations with bigger rotors. Combined FM shows that hybrid configuration outperforms other octocopter configurations in overall aerodynamic performance.展开更多
The purpose of increasing the aerodynamic efficiency and enhancing the supermaneuverability for the selected supersonic aircraft is presented. Aerodynamic characteristics, the surface pressure distribution and the max...The purpose of increasing the aerodynamic efficiency and enhancing the supermaneuverability for the selected supersonic aircraft is presented. Aerodynamic characteristics, the surface pressure distribution and the maximum lift are estimated for the baseline configuration for different Mach numbers and attack angles in subson- ic and supersonic potential flows, using a low-order three-dimensional panel method supported with the semi-empirical formulas of the data compendium （DATCOM）. Total nose-up and nose-down pitching moments about the center of gravity of the complete aircraft in the subsonic region depending on flight conditions and aircraft performance limitations are estimated. A software package is developed to implement the two-dimensional thrust vectoring flight control technique （pitch vectoring up and down） controlled by the advanced aerodynamic and control surface （the foreplane or the canard）. Results show that the canard with the thrust vectoring produces enough nose-down moment and can support the stabilizer at high maneuvers. The suggested surface can increase the aerodynamic efficiency （lift-to-drag ratio） of the baseline configuration by 5%-6% in subsonic and supersonic flight regimes.展开更多
A series of wind tunnel tests were performed to investigate the effect of turbulent inflows on the aerodynamic characteristics of the unsymmetrical airfoil at various turbulence intensities and Reynolds number. To ass...A series of wind tunnel tests were performed to investigate the effect of turbulent inflows on the aerodynamic characteristics of the unsymmetrical airfoil at various turbulence intensities and Reynolds number. To assess the aerodynamic characteristics, surface pressure measurements were made over the unsymmetrical airfoil surface by using a simultaneous pressure scanner MPS4264 of Scanivalve make. Self-generated passive grids made of parallel arrays of round bars were placed at four different locations to generate various Turbulence Intensities(TI) in the wind tunnel. The location of the passive grid has been normalized in terms of considering the distance between the entry of the test section and the leading edge of the model. Based on the wind tunnel results, by comparing the baseline without grid low turbulence case TI = 0.51% with other turbulence generated cases like TI = 4.68%, 4.73%, 6.04% and 8.46% at different Reynolds number, it is found that the coefficient of lift increases with the increase in the turbulence intensity. Results also reveal that the flow featuring turbulence can effectively delay the stall characteristics of an airfoil by attaching the flow over the airfoil for an extended region. Additionally, attempts were made to understand the influence of turbulence on the aerodynamic hysteresis.展开更多
Shock formation due to flow compressibility and its interaction with boundary layers has adverse effects on aerodynamic characteristics, such as drag increase and flow separation. The objective of this paper is to app...Shock formation due to flow compressibility and its interaction with boundary layers has adverse effects on aerodynamic characteristics, such as drag increase and flow separation. The objective of this paper is to appraise the practicability of weakening shock waves and, hence, reducing the wave drag in transonic flight regime using a two-dimensional jagged wall and thereby to gain an appropriate jagged wall shape for future empirical study. Different shapes of the jagged wall, including rectangular, circular, and triangular shapes, were employed. The numerical method was validated by experimental and numerical studies involving transonic flow over the NACA0012 airfoil, and the results presented here closely match previous experimental and numerical results. The impact of parameters, including shape and the length-to-spacing ratio of a jagged wall, was studied on aerodynamic forces and flow field. The results revealed that applying a jagged wall method on the upper surface of an airfoil changes the shock structure significantly and disintegrates it, which in turn leads to a decrease in wave drag. It was also found that the maximum drag coefficient decrease of around 17 % occurs with a triangular shape, while the maximum increase in aerodynamic efficiency（lift-to-drag ratio）of around 10 % happens with a rectangular shape at an angle of attack of 2.26？.展开更多
The need for revolutionary techniques to augment aerodynamic efficiency is paramount for achieving substantial reductions in drag and consequent fuel consumption.This paper revolves around exploiting zinc oxide nanost...The need for revolutionary techniques to augment aerodynamic efficiency is paramount for achieving substantial reductions in drag and consequent fuel consumption.This paper revolves around exploiting zinc oxide nanostructures to increase boundary layer adhesion and delay stall in airfoils.Zinc oxide nanostructures are employed to induce vortices,re-energize the airflowand function as nano flowcontrol device.Thework on this paper commenced with the proof of concept by means of comprehensive computational simulation utilizing COMSOL software and ended with experimental lab tests.A meticulous two-step process involving the sol–gel method and dip coating was employed to grow nanorods on the wing’s surface.Initial prototyping utilized 3D printing,and subsequent aluminum samples were produced using sand casting techniques.The coated wing specimen underwent rigorous wind tunnel testing to assess its aerodynamic performance under controlled airflow conditions.This thorough approach facilitated a profound understanding of the coated wing’s behavior,enabling insights for further optimization.The results revealed a significant 16%delay in stall and an average 4%reduction in drag.This pioneering approach not only optimizes aircraft aerodynamics but also mitigates fuel costs and environmental impact.Moreover,the study’s observations offer avenues for future exploration,including the fine-tuning of coating parameters and exploring diverse applications of ZnO nanorods in aerospace engineering.展开更多
Essential qualities which a drone can effortlessly accomplish for every task include performance,safety,accessibility,and adaptability because of its efficiency.For different reasons,the efficiency of the drone is aff...Essential qualities which a drone can effortlessly accomplish for every task include performance,safety,accessibility,and adaptability because of its efficiency.For different reasons,the efficiency of the drone is affected by an extensive number of parameters.Thus,a focus on improving drone’s efficiency has been proposed in this study.Usually,operational speed affects efficiency.Propellers have the potential to regulate operating speed.The propeller is an essential component of the drone’s operation,and experts are always looking for new ways to improve its performance through novel studies.Multiple studies have been conducted and the findings indicate that employing leading-edge(LE)tubercles on propellers produces superior outcomes.For this computational study,the re-normalization group(RNG)equations with a k−1 turbulence model have been solved,using the Ansys Fluent solver.The range of RPM was 2000–8000,while the flow velocity ranged from 0.1 to 0.6 J(advance ratio).Calculations showed that the propeller with serrations had a significant improvement in thrust,power,thrust coefficient and power coefficient values.The outcomes were contrasted with the computational results from the available literature.Aerodynamic and overall performance trends showed a good degree of consistency,suggesting that tubercle propellers will be superior to baseline propellers in terms of efficiency.展开更多
In 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.F...In 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.展开更多
This study investigates the potential of Fish Bone Morphing(FBM)technology for enhancing the aerodynamic performance of aerofoils.FBM is a bio-inspired concept that incorporates flexible structural elements to facilit...This study investigates the potential of Fish Bone Morphing(FBM)technology for enhancing the aerodynamic performance of aerofoils.FBM is a bio-inspired concept that incorporates flexible structural elements to facilitate morphing of the aerofoil shape in response to varying flight conditions.The NACA 2412 aerofoil is chosen for its camber adaptability,and CFD simulations are employed to assess the efficacy of FBM integration.The k-ω SST turbulence model is adopted for its ability to combine the strengths of the k-ω and k-ε models.The investigation encompasses a systematic exploration of geometric configurations,including trailing edge deflection at various chord lengths(0.6c,0.65c,0.70c,0.75c,and 0.80c)and deflection angles(4°,8°,and 12°).The results reveal that FBM aerofoils exhibit a consistent increase in maximum lift coefficient compared to conventional aerofoils across all deflection points and angles.Additionally,improvements in lift-todrag ratio are observed.Furthermore,the stalling angle remains unaffected by deflection point variations,while deflection angle increments lead to corresponding increases in maximum lift coefficient.The morphing aerofoil with a 0.60c deflection point demonstrates themost significant enhancement in maximum lift coefficient,achieving a 13% increase at a 12°deflection angle.These findings establish the aerodynamic efficiency of FBM aerofoils,characterized by superior lift-to-drag ratios and increased maximum lift coefficients.展开更多
Vehicle skin is the key component in maintaining the aerodynamic shape of the vehicle.A deformable high-speed vehicle needs to adjust its shape in real time to realize optimum aerodynamic efficiency and to withstand e...Vehicle skin is the key component in maintaining the aerodynamic shape of the vehicle.A deformable high-speed vehicle needs to adjust its shape in real time to realize optimum aerodynamic efficiency and to withstand extreme heat flow induced by high-speed flight,which requires the skin to possess large strain and high-temperature resistance.Traditional vehicle skin cannot satisfy both of the requirements.Biomimetic flexible skin for deformable high-speed vehicles(DHSV-bio-FS)combines flexible material fabrication with transpiration cooling technology,which can simulate human skin sweat cooling,and has the characteristics of large strain and high-temperature resistance.The thermal protection performance of the prepared prototype of DHSV-bio-FS was evaluated by simulation and wind tunnel experiments at 40% tensile strain with liquid water as coolant.Simulation results suggest that the surface temperature of the DHSV-bio-FS at 40% tensile strain is consistent with the temperature of the coolant(350 K)in a 3,000 K high-temperature gas environment.In addition,the prepared prototype DHSV-bio-FS survived for 1,200 s in a high-temperature gas environment of 200 kW/m^(2)in wind tunnel experiments.This paper verifies the reliability of DHSV-bio-FS in a high-temperature gas environment and can be deployed in applications of flexible skin for deformable high-speed vehicles(DHSV-FS).展开更多
Blended wing body(BWB)is a new design in which both the fuselage and the wings form the lifting surface of the body.Due to this design,the aerodynamic performance of the aircraft is enhanced as a result there is reduc...Blended wing body(BWB)is a new design in which both the fuselage and the wings form the lifting surface of the body.Due to this design,the aerodynamic performance of the aircraft is enhanced as a result there is reduction in noise and fuel consumption.Themajor two drawbacks of this design are the handling and the complex design.Due to these issues,this design cannot be used predominantly in the aircraft industry.This paper gives a holistic review of various experimental,numerical,and theoretical studies done on the topic along with the basic analysis and study along various recent developments like geometric alterations such as canard or gurney flaps.The studies done in implementing the advantages of BWB in UAVs and under water bodies are also mentioned in this review.The BWB is a new revolutionary concept that can find its way into the modern aircraft design,but it has certain limitations that need to be addressed before using this design commercially or in military aircraft.It is likely that the information acquired in this paper could be useful to the future BWB aircraft design and study along with its various geometric alterations and uses.展开更多
基金supported by the National Natural Science Foundation of China(No.11972190).
文摘Rotor-to-rotor interaction among neighboring rotors of a multirotor has great significance for aerodynamically efficient multirotor design. Current research is conducted to analyze aerodynamic performance of different octocopter configurations amid hover and forward flight. Conventional and coaxial configurations are studied and a hybrid configuration is also proposed to rectify the disadvantages associated with the earlier two. Comparison is carried out for the aforementioned configurations along with comparison of coaxial and hybrid octocopters with bigger diameter rotors in the same confined space for high thrust requirement missions. Vertical spacing of coaxial configuration is also studied. Virtual Blade Method (VBM) is considered herein due to its great computational efficiency. The results show that there are 11.89% and 14.22% loss in thrust for coaxial octocopter compared to conventional and hybrid configurations with normal size rotors and 15.61% loss compared to hybrid configuration with bigger rotors in hover, whereas coaxial square configuration performs the worst in forward flight with a lift loss of 9.1%, 14.77% and 18.8% compared to coaxial diamond, conventional and hybrid configurations with normal size rotors and 9.96% and 17.82% loss compared to coaxial diamond and hybrid configurations with bigger rotors. Combined FM shows that hybrid configuration outperforms other octocopter configurations in overall aerodynamic performance.
文摘The purpose of increasing the aerodynamic efficiency and enhancing the supermaneuverability for the selected supersonic aircraft is presented. Aerodynamic characteristics, the surface pressure distribution and the maximum lift are estimated for the baseline configuration for different Mach numbers and attack angles in subson- ic and supersonic potential flows, using a low-order three-dimensional panel method supported with the semi-empirical formulas of the data compendium （DATCOM）. Total nose-up and nose-down pitching moments about the center of gravity of the complete aircraft in the subsonic region depending on flight conditions and aircraft performance limitations are estimated. A software package is developed to implement the two-dimensional thrust vectoring flight control technique （pitch vectoring up and down） controlled by the advanced aerodynamic and control surface （the foreplane or the canard）. Results show that the canard with the thrust vectoring produces enough nose-down moment and can support the stabilizer at high maneuvers. The suggested surface can increase the aerodynamic efficiency （lift-to-drag ratio） of the baseline configuration by 5%-6% in subsonic and supersonic flight regimes.
基金supported by the Science Engineering Research Board (SERB)Department of Science & Technology (DST) of India (No. ECR/2017/001199)
文摘A series of wind tunnel tests were performed to investigate the effect of turbulent inflows on the aerodynamic characteristics of the unsymmetrical airfoil at various turbulence intensities and Reynolds number. To assess the aerodynamic characteristics, surface pressure measurements were made over the unsymmetrical airfoil surface by using a simultaneous pressure scanner MPS4264 of Scanivalve make. Self-generated passive grids made of parallel arrays of round bars were placed at four different locations to generate various Turbulence Intensities(TI) in the wind tunnel. The location of the passive grid has been normalized in terms of considering the distance between the entry of the test section and the leading edge of the model. Based on the wind tunnel results, by comparing the baseline without grid low turbulence case TI = 0.51% with other turbulence generated cases like TI = 4.68%, 4.73%, 6.04% and 8.46% at different Reynolds number, it is found that the coefficient of lift increases with the increase in the turbulence intensity. Results also reveal that the flow featuring turbulence can effectively delay the stall characteristics of an airfoil by attaching the flow over the airfoil for an extended region. Additionally, attempts were made to understand the influence of turbulence on the aerodynamic hysteresis.
文摘Shock formation due to flow compressibility and its interaction with boundary layers has adverse effects on aerodynamic characteristics, such as drag increase and flow separation. The objective of this paper is to appraise the practicability of weakening shock waves and, hence, reducing the wave drag in transonic flight regime using a two-dimensional jagged wall and thereby to gain an appropriate jagged wall shape for future empirical study. Different shapes of the jagged wall, including rectangular, circular, and triangular shapes, were employed. The numerical method was validated by experimental and numerical studies involving transonic flow over the NACA0012 airfoil, and the results presented here closely match previous experimental and numerical results. The impact of parameters, including shape and the length-to-spacing ratio of a jagged wall, was studied on aerodynamic forces and flow field. The results revealed that applying a jagged wall method on the upper surface of an airfoil changes the shock structure significantly and disintegrates it, which in turn leads to a decrease in wave drag. It was also found that the maximum drag coefficient decrease of around 17 % occurs with a triangular shape, while the maximum increase in aerodynamic efficiency（lift-to-drag ratio）of around 10 % happens with a rectangular shape at an angle of attack of 2.26？.
文摘The need for revolutionary techniques to augment aerodynamic efficiency is paramount for achieving substantial reductions in drag and consequent fuel consumption.This paper revolves around exploiting zinc oxide nanostructures to increase boundary layer adhesion and delay stall in airfoils.Zinc oxide nanostructures are employed to induce vortices,re-energize the airflowand function as nano flowcontrol device.Thework on this paper commenced with the proof of concept by means of comprehensive computational simulation utilizing COMSOL software and ended with experimental lab tests.A meticulous two-step process involving the sol–gel method and dip coating was employed to grow nanorods on the wing’s surface.Initial prototyping utilized 3D printing,and subsequent aluminum samples were produced using sand casting techniques.The coated wing specimen underwent rigorous wind tunnel testing to assess its aerodynamic performance under controlled airflow conditions.This thorough approach facilitated a profound understanding of the coated wing’s behavior,enabling insights for further optimization.The results revealed a significant 16%delay in stall and an average 4%reduction in drag.This pioneering approach not only optimizes aircraft aerodynamics but also mitigates fuel costs and environmental impact.Moreover,the study’s observations offer avenues for future exploration,including the fine-tuning of coating parameters and exploring diverse applications of ZnO nanorods in aerospace engineering.
文摘Essential qualities which a drone can effortlessly accomplish for every task include performance,safety,accessibility,and adaptability because of its efficiency.For different reasons,the efficiency of the drone is affected by an extensive number of parameters.Thus,a focus on improving drone’s efficiency has been proposed in this study.Usually,operational speed affects efficiency.Propellers have the potential to regulate operating speed.The propeller is an essential component of the drone’s operation,and experts are always looking for new ways to improve its performance through novel studies.Multiple studies have been conducted and the findings indicate that employing leading-edge(LE)tubercles on propellers produces superior outcomes.For this computational study,the re-normalization group(RNG)equations with a k−1 turbulence model have been solved,using the Ansys Fluent solver.The range of RPM was 2000–8000,while the flow velocity ranged from 0.1 to 0.6 J(advance ratio).Calculations showed that the propeller with serrations had a significant improvement in thrust,power,thrust coefficient and power coefficient values.The outcomes were contrasted with the computational results from the available literature.Aerodynamic and overall performance trends showed a good degree of consistency,suggesting that tubercle propellers will be superior to baseline propellers in terms of efficiency.
基金funding organizations in China:the National Key Research and Development Program of China(Grant No.2018YFB1305400)the National Natural Science Foundation of China(Grant Nos.62173212 and 11972079).
文摘In 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.
文摘This study investigates the potential of Fish Bone Morphing(FBM)technology for enhancing the aerodynamic performance of aerofoils.FBM is a bio-inspired concept that incorporates flexible structural elements to facilitate morphing of the aerofoil shape in response to varying flight conditions.The NACA 2412 aerofoil is chosen for its camber adaptability,and CFD simulations are employed to assess the efficacy of FBM integration.The k-ω SST turbulence model is adopted for its ability to combine the strengths of the k-ω and k-ε models.The investigation encompasses a systematic exploration of geometric configurations,including trailing edge deflection at various chord lengths(0.6c,0.65c,0.70c,0.75c,and 0.80c)and deflection angles(4°,8°,and 12°).The results reveal that FBM aerofoils exhibit a consistent increase in maximum lift coefficient compared to conventional aerofoils across all deflection points and angles.Additionally,improvements in lift-todrag ratio are observed.Furthermore,the stalling angle remains unaffected by deflection point variations,while deflection angle increments lead to corresponding increases in maximum lift coefficient.The morphing aerofoil with a 0.60c deflection point demonstrates themost significant enhancement in maximum lift coefficient,achieving a 13% increase at a 12°deflection angle.These findings establish the aerodynamic efficiency of FBM aerofoils,characterized by superior lift-to-drag ratios and increased maximum lift coefficients.
基金supported by the Major Research Plan of the National Natural Science Foundation of China(Grant No.92271201)the Natural Science Basic Research Program of Shaanxi(Program No.2024JC-JCQN-61).
文摘Vehicle skin is the key component in maintaining the aerodynamic shape of the vehicle.A deformable high-speed vehicle needs to adjust its shape in real time to realize optimum aerodynamic efficiency and to withstand extreme heat flow induced by high-speed flight,which requires the skin to possess large strain and high-temperature resistance.Traditional vehicle skin cannot satisfy both of the requirements.Biomimetic flexible skin for deformable high-speed vehicles(DHSV-bio-FS)combines flexible material fabrication with transpiration cooling technology,which can simulate human skin sweat cooling,and has the characteristics of large strain and high-temperature resistance.The thermal protection performance of the prepared prototype of DHSV-bio-FS was evaluated by simulation and wind tunnel experiments at 40% tensile strain with liquid water as coolant.Simulation results suggest that the surface temperature of the DHSV-bio-FS at 40% tensile strain is consistent with the temperature of the coolant(350 K)in a 3,000 K high-temperature gas environment.In addition,the prepared prototype DHSV-bio-FS survived for 1,200 s in a high-temperature gas environment of 200 kW/m^(2)in wind tunnel experiments.This paper verifies the reliability of DHSV-bio-FS in a high-temperature gas environment and can be deployed in applications of flexible skin for deformable high-speed vehicles(DHSV-FS).
文摘Blended wing body(BWB)is a new design in which both the fuselage and the wings form the lifting surface of the body.Due to this design,the aerodynamic performance of the aircraft is enhanced as a result there is reduction in noise and fuel consumption.Themajor two drawbacks of this design are the handling and the complex design.Due to these issues,this design cannot be used predominantly in the aircraft industry.This paper gives a holistic review of various experimental,numerical,and theoretical studies done on the topic along with the basic analysis and study along various recent developments like geometric alterations such as canard or gurney flaps.The studies done in implementing the advantages of BWB in UAVs and under water bodies are also mentioned in this review.The BWB is a new revolutionary concept that can find its way into the modern aircraft design,but it has certain limitations that need to be addressed before using this design commercially or in military aircraft.It is likely that the information acquired in this paper could be useful to the future BWB aircraft design and study along with its various geometric alterations and uses.
