Martin M. Müller, Armin Weiss, Johannes N. Braukmann
Experimental investigations of three-dimensional dynamic stall on a four-bladed Mach-scaled semielastic rotor with an innovative double-swept rotor blade planform are presented. The study focuses on the coupling between the aeroelastic behavior of the blade and the underlying aerodynamics. Blade bending moment and flap displacement measurements were conducted using strain gauges and optical tracking of blade tip markers. The aerodynamic behavior was characterized by means of unsteady surface pressure measurements using unsteady pressure-sensitive paint (iPSP) across the outer 65% of the blade span and fast response pressure transducers at discrete locations. Different cyclic-pitch settings were investigated at a rotation frequency of f rotor = 23.6 Hz that corresponds to blade tip Mach and Reynolds numbers of M tip = 0.282– 0.285 and Re tip = 5.84-5.95 ×10 5 . The findings reveal a detailed insight into the nonlinear behavior in the flap movement during downstroke. iPSP and pressure transducer data indicate that this nonlinear flap behavior is caused by a radially phase-shifted dynamic stall process at the forward and backward swept part of the blade.
{"title":"Dynamic Stall Investigation on a Rotating Semielastic Double-swept Rotor Blade at the Rotor Test Facility Göttingen","authors":"Martin M. Müller, Armin Weiss, Johannes N. Braukmann","doi":"10.4050/jahs.68.022007","DOIUrl":"https://doi.org/10.4050/jahs.68.022007","url":null,"abstract":"Experimental investigations of three-dimensional dynamic stall on a four-bladed Mach-scaled semielastic rotor with an innovative double-swept rotor blade planform are presented. The study focuses on the coupling between the aeroelastic behavior of the blade and the underlying aerodynamics. Blade bending moment and flap displacement measurements were conducted using strain gauges and optical tracking of blade tip markers. The aerodynamic behavior was characterized by means of unsteady surface pressure measurements using unsteady pressure-sensitive paint (iPSP) across the outer 65% of the blade span and fast response pressure transducers at discrete locations. Different cyclic-pitch settings were investigated at a rotation frequency of f rotor = 23.6 Hz that corresponds to blade tip Mach and Reynolds numbers of M tip = 0.282– 0.285 and Re tip = 5.84-5.95 ×10 5 . The findings reveal a detailed insight into the nonlinear behavior in the flap movement during downstroke. iPSP and pressure transducer data indicate that this nonlinear flap behavior is caused by a radially phase-shifted dynamic stall process at the forward and backward swept part of the blade.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136261408","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A hybrid gear concept that combines a metallic outer rim of gear teeth with a composite web to reduce drivetrain weight was evaluated for impact of tooth microgeometry modifications on transmission error. Control of transmission error through tooth microgeometry modification is important for control of noise and vibrations generated by a drivetrain. The added flexibility of hybrid gears over steel gears brings to question the performance of hybrid over conventional gears relative to their dynamic transmission error and resulting noise levels. Previously developed drivetrain models featuring hybrid spur gears were used to determine optimal tooth microgeometry modifications that minimized peak-to-peak transmission error. Static and dynamic transmission errors were then calculated using the optimal microgeometries and compared to results for a similarly optimized all-steel drivetrain. From the results, it appears that the use of hybrid gears will not negatively affect vibration performance for low- and medium-speed applications, as hybrid gear models predicted similar transmission errors to their all-steel counterparts. At higher speeds, drivetrains featuring hybrid gears were predicted to have significantly different transmission errors, but whether this difference was an improvement or detriment is design and speed-dependent. Therefore, careful design is necessary for high-speed hybrid gears.
{"title":"Effects of Optimal Tooth Microgeometry Modifications on Static and Dynamic Transmission Errors of Hybrid Spur Gear Drivetrains","authors":"Sean Gauntt, S. McIntyre, R. Campbell","doi":"10.4050/jahs.68.042006","DOIUrl":"https://doi.org/10.4050/jahs.68.042006","url":null,"abstract":"A hybrid gear concept that combines a metallic outer rim of gear teeth with a composite web to reduce drivetrain weight was evaluated for impact of tooth microgeometry modifications on transmission error. Control of transmission error through tooth microgeometry modification is important for control of noise and vibrations generated by a drivetrain. The added flexibility of hybrid gears over steel gears brings to question the performance of hybrid over conventional gears relative to their dynamic transmission error and resulting noise levels. Previously developed drivetrain models featuring hybrid spur gears were used to determine optimal tooth microgeometry modifications that minimized peak-to-peak transmission error. Static and dynamic transmission errors were then calculated using the optimal microgeometries and compared to results for a similarly optimized all-steel drivetrain. From the results, it appears that the use of hybrid gears will not negatively affect vibration performance for low- and medium-speed applications, as hybrid gear models predicted similar transmission errors to their all-steel counterparts. At higher speeds, drivetrains featuring hybrid gears were predicted to have significantly different transmission errors, but whether this difference was an improvement or detriment is design and speed-dependent. Therefore, careful design is necessary for high-speed hybrid gears.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"37 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70219303","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This article describes the development, implementation, and validation of a generic tilt-rotor simulation model with coupled flight dynamics, state-variable aeromechanics, and aeroacoustics. A major novelty of this work lies in the integration of the flight dynamics with a state-space free-vortex wake code that adopts a near-wake vortex-lattice model. This way, the flight dynamics are augmented by the vortex wake dynamics so that the coupled flight and wake dynamics are self-contained and inherently linearizable. The model is implemented for a Bell XV-15 tiltrotor and validated against U.S. Army/NASA XV-15 flight-test data and other data in the literature. Flight control design is performed to provide desired stability, performance, and handling-quality properties and to allow for a fully autonomous transition between hover in helicopter mode and high-speed flight in aircraft mode. The simulation model has clear applications in the development and testing of advanced flight control laws, aeromechanics analysis, and the prediction of aerodynamically generated noise in generalized maneuvering flight.
{"title":"Tiltrotor Simulations with Coupled Flight Dynamics, State-Space Aeromechanics, and Aeroacoustics","authors":"Umberto Saetti, Batän Buäday","doi":"10.4050/jahs.69.012003","DOIUrl":"https://doi.org/10.4050/jahs.69.012003","url":null,"abstract":"This article describes the development, implementation, and validation of a generic tilt-rotor simulation model with coupled flight dynamics, state-variable aeromechanics, and aeroacoustics. A major novelty of this work lies in the integration of the flight dynamics with a state-space free-vortex wake code that adopts a near-wake vortex-lattice model. This way, the flight dynamics are augmented by the vortex wake dynamics so that the coupled flight and wake dynamics are self-contained and inherently linearizable. The model is implemented for a Bell XV-15 tiltrotor and validated against U.S. Army/NASA XV-15 flight-test data and other data in the literature. Flight control design is performed to provide desired stability, performance, and handling-quality properties and to allow for a fully autonomous transition between hover in helicopter mode and high-speed flight in aircraft mode. The simulation model has clear applications in the development and testing of advanced flight control laws, aeromechanics analysis, and the prediction of aerodynamically generated noise in generalized maneuvering flight.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70219668","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vertical bounce is a rotorcraft aeroelastic instability triggered by the feedback interaction between two significantly damped vibration modes: the rotor collective flap mode and the biodynamic vertical oscillation of the pilot’s left arm holding the collective lever in the cockpit. The instability can endanger the safety of flight and in some cases led to catastrophic events. This work develops simple yet complete models that allow us to better understand the dependency of the phenomenon on parameters like the flight condition, the characteristics of the aircraft, and the properties of the pilot’s biodynamic feedthrough. The stability analyses presented demonstrate that the landing gear dynamics may amplify the vertical oscillations driven by the pilot’s biodynamic response when considering on-ground conditions, reducing the stability margins of the pilot–vehicle system. The detailed sensitivity analysis allows inferring indications to develop future rotorcraft that could be less prone to this adverse rotorcraft–pilot coupling phenomenon.
{"title":"Impact of Design and Operational Parameters on Helicopter Vertical Bounce","authors":"V. Muscarello, A. Zanoni, G. Quaranta","doi":"10.4050/jahs.68.032009","DOIUrl":"https://doi.org/10.4050/jahs.68.032009","url":null,"abstract":"Vertical bounce is a rotorcraft aeroelastic instability triggered by the feedback interaction between two significantly damped vibration modes: the rotor collective flap mode and the biodynamic vertical oscillation of the pilot’s left arm holding the collective lever in the cockpit. The instability can endanger the safety of flight and in some cases led to catastrophic events. This work develops simple yet complete models that allow us to better understand the dependency of the phenomenon on parameters like the flight condition, the characteristics of the aircraft, and the properties of the pilot’s biodynamic feedthrough. The stability analyses presented demonstrate that the landing gear dynamics may amplify the vertical oscillations driven by the pilot’s biodynamic response when considering on-ground conditions, reducing the stability margins of the pilot–vehicle system. The detailed sensitivity analysis allows inferring indications to develop future rotorcraft that could be less prone to this adverse rotorcraft–pilot coupling phenomenon.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70219224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Park, Byeonguk Im, Dongyeol Lee, Sang-Joon Shin
With the wide application of unmanned aerial vehicles, interest in multirotor configurations has increased. The unique features of multirotor configuration have been intensely investigated, including aerodynamic interference, which is particularly important because it influences the vibration, noise, and handling quality of rotorcraft. Most previous studies have used high-fidelity approaches, such as computational fluid dynamics to identify such interference. However, such an approach is inappropriate for real-time flight simulations. In this study, an improved aerodynamic interference analysis based on a dynamic vortex tube was established for performance prediction in real-time flight simulation. A simple and effective formulation is proposed for integration with rotor aerodynamics to evaluate the interference of multirotor configurations. The present analysis is validated on various multirotor configurations. An investigation of interference in a multirotor unmanned aerial vehicle (UAV) is then presented. The analysis results exhibit good agreement with experimental results and high-fidelity predictions. Although the accuracy of the proposed analysis is lower than that of experimental studies and high-fidelity analyses, it is sufficient for capturing interference trends. The proposed analysis can account for aerodynamic interference in the flight simulation of a multirotor UAV.
{"title":"Aerodynamic interference analysis for a nonoverlapping multirotor UAV based on dynamic vortex tube","authors":"S. Park, Byeonguk Im, Dongyeol Lee, Sang-Joon Shin","doi":"10.4050/jahs.68.042010","DOIUrl":"https://doi.org/10.4050/jahs.68.042010","url":null,"abstract":"With the wide application of unmanned aerial vehicles, interest in multirotor configurations has increased. The unique features of multirotor configuration have been intensely investigated, including aerodynamic interference, which is particularly important because it influences the vibration, noise, and handling quality of rotorcraft. Most previous studies have used high-fidelity approaches, such as computational fluid dynamics to identify such interference. However, such an approach is inappropriate for real-time flight simulations. In this study, an improved aerodynamic interference analysis based on a dynamic vortex tube was established for performance prediction in real-time flight simulation. A simple and effective formulation is proposed for integration with rotor aerodynamics to evaluate the interference of multirotor configurations. The present analysis is validated on various multirotor configurations. An investigation of interference in a multirotor unmanned aerial vehicle (UAV) is then presented. The analysis results exhibit good agreement with experimental results and high-fidelity predictions. Although the accuracy of the proposed analysis is lower than that of experimental studies and high-fidelity analyses, it is sufficient for capturing interference trends. The proposed analysis can account for aerodynamic interference in the flight simulation of a multirotor UAV.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70220034","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Frederick Tsai, James Sutherland, Akinola Akinwale, Amy Morin, Seyhan Gul, Anubhav Datta
The first whirl flutter test of the Maryland Tiltrotor Rig (MTR) was recently completed in the Naval Surface Warfare Center Carderock Division 2.44 m by 3.05 m (8- by 10-ft) large subsonic wind tunnel. The MTR is a 1.45 m (4.75-ft) diameter, three-bladed, semispan, floor-mounted, optionally powered, flutter rig. This paper describes the major features of the MTR and the results obtained from the first successful flutter tests. Parametric variations of rig features include wing profile on and off, gimbal free and gimbal locked hub, powered and freewheeling rotor, and straight and swept-tip blades. For the freewheeling rotor condition, the rotor speed is trimmed to 1050 RPM by setting blade collective. The gimbal is trimmed to zero first harmonic flapping by setting blade cyclics. Model configurations were tested up to 100 kt windspeed. The model was excited by oscillating the swashplate at the wing-pylon natural frequencies. Eight speed sweeps were carried out to acquire frequency and damping data on different model configurations. Frequency and damping of the wing beam and chord modes were extracted using the moving-block method.
{"title":"Development and Whirl Flutter Test of the Maryland Tiltrotor Rig","authors":"Frederick Tsai, James Sutherland, Akinola Akinwale, Amy Morin, Seyhan Gul, Anubhav Datta","doi":"10.4050/jahs.69.012009","DOIUrl":"https://doi.org/10.4050/jahs.69.012009","url":null,"abstract":"The first whirl flutter test of the Maryland Tiltrotor Rig (MTR) was recently completed in the Naval Surface Warfare Center Carderock Division 2.44 m by 3.05 m (8- by 10-ft) large subsonic wind tunnel. The MTR is a 1.45 m (4.75-ft) diameter, three-bladed, semispan, floor-mounted, optionally powered, flutter rig. This paper describes the major features of the MTR and the results obtained from the first successful flutter tests. Parametric variations of rig features include wing profile on and off, gimbal free and gimbal locked hub, powered and freewheeling rotor, and straight and swept-tip blades. For the freewheeling rotor condition, the rotor speed is trimmed to 1050 RPM by setting blade collective. The gimbal is trimmed to zero first harmonic flapping by setting blade cyclics. Model configurations were tested up to 100 kt windspeed. The model was excited by oscillating the swashplate at the wing-pylon natural frequencies. Eight speed sweeps were carried out to acquire frequency and damping data on different model configurations. Frequency and damping of the wing beam and chord modes were extracted using the moving-block method.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"258 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135505063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Time-dependent Navier–Stokes simulations have been carried out for a V22 rotor in hover using an improved, low-dissipation, HLLE++ upwind algorithm in the OVERFLOW code. Emphasis is placed on lessons learned over the past decade regarding the effects of high-order spatial accuracy, grid resolution, and the use of detached eddy simulation in predicting the figure-of-merit, the rotor's chief performance parameter. A general quick-start procedure is described together with a statistical measure of FM convergence that reduces hover computations by fourfold, similar to computational work for forward flight. Cartesian adaptive mesh refinement is used to resolve the tip–vortex to its correct physical size. This adaptive mesh refinement in the rotor wake also revealed a complex turbulent flow with worm-like structures of various scales. These structures were numerically found a decade ago and recently observed in experiment.
{"title":"A Quantitative Approach for the Accurate CFD Simulation of Hover in Turbulent Flow","authors":"N. Chaderjian","doi":"10.4050/jahs.68.042009","DOIUrl":"https://doi.org/10.4050/jahs.68.042009","url":null,"abstract":"Time-dependent Navier–Stokes simulations have been carried out for a V22 rotor in hover using an improved, low-dissipation, HLLE++ upwind algorithm in the OVERFLOW code. Emphasis is placed on lessons learned over the past decade regarding the effects of high-order spatial accuracy, grid resolution, and the use of detached eddy simulation in predicting the figure-of-merit, the rotor's chief performance parameter. A general quick-start procedure is described together with a statistical measure of FM convergence that reduces hover computations by fourfold, similar to computational work for forward flight. Cartesian adaptive mesh refinement is used to resolve the tip–vortex to its correct physical size. This adaptive mesh refinement in the rotor wake also revealed a complex turbulent flow with worm-like structures of various scales. These structures were numerically found a decade ago and recently observed in experiment.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70219443","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Austin D. Thai, Beatrice Roget, Jayanarayanan Sitaraman, Nikolas S. Zawodny, Sheryl M. Grace
A multirotor trim algorithm is developed and validated using the HPCMP CREATE™-AV Helios rotorcraft analysis and simulation framework. Validation data were sourced from experiments in which a quadrotor with fixed-pitch rotors was trimmed for steady hover and forward flight in the NASA Langley Low-Speed Aeroacoustic Wind Tunnel. For each flight condition, the aircraft attitudes were fixed so that the only control variables were the rotation rates of the four rotors, which were varied until the residual loads were minimal. The resultant trim states were first replicated in the computational framework to verify the aerodynamic solver. Then, the trim algorithm was validated in Helios by constraining the aircraft attitudes and searching for the rotor speeds that minimized the residual loads. The analysis demonstrated excellent agreement between the predicted and measured trim states. Finally, free-flight trim cases were simulated to quantify the effect of the trim constraints and verify the experimentally trimmed flight conditions. The predicted free-flight trim state showed reasonable agreement to the constrained case, with negligible change in the residual loads, indicating trim was achieved in both the experiments and the simulations.
{"title":"Validation of Variable Rotor Speed Trim Using Computational Fluid Dynamics","authors":"Austin D. Thai, Beatrice Roget, Jayanarayanan Sitaraman, Nikolas S. Zawodny, Sheryl M. Grace","doi":"10.4050/jahs.69.012008","DOIUrl":"https://doi.org/10.4050/jahs.69.012008","url":null,"abstract":"A multirotor trim algorithm is developed and validated using the HPCMP CREATE™-AV Helios rotorcraft analysis and simulation framework. Validation data were sourced from experiments in which a quadrotor with fixed-pitch rotors was trimmed for steady hover and forward flight in the NASA Langley Low-Speed Aeroacoustic Wind Tunnel. For each flight condition, the aircraft attitudes were fixed so that the only control variables were the rotation rates of the four rotors, which were varied until the residual loads were minimal. The resultant trim states were first replicated in the computational framework to verify the aerodynamic solver. Then, the trim algorithm was validated in Helios by constraining the aircraft attitudes and searching for the rotor speeds that minimized the residual loads. The analysis demonstrated excellent agreement between the predicted and measured trim states. Finally, free-flight trim cases were simulated to quantify the effect of the trim constraints and verify the experimentally trimmed flight conditions. The predicted free-flight trim state showed reasonable agreement to the constrained case, with negligible change in the residual loads, indicating trim was achieved in both the experiments and the simulations.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"88 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135007568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Umberto Saetti, Batin Bugday, Joseph F. Horn, Kenneth S. Brentner
This article demonstrates the linearization of the coupled rotorcraft flight dynamics and aeroacoustics to provide real-time acoustic predictions in generalized maneuvering flight. To demonstrate the methodology, the study makes use of a nonlinear simulation model of a generic utility helicopter (PSUHeloSim) that is coupled with an aeroacoustic solver based on a marching cubes algorithm. A periodic equilibrium of the coupled rotorcraft flight dynamics and acoustics is first found at a desired flight condition using a modified harmonic balance trim solution method. Next, the nonlinear time-periodic dynamics are linearized about that periodic equilibrium and transformed into an equivalent higher order linear time-invariant system in harmonic decomposition form. Composite aeroacoustic measures are included as an output of this system. To speed up runtime and make control design tractable, the order of these harmonic decomposition models is reduced via residualization to an 8-state model where the states are representative of the rigid-body dynamics of the aircraft. This 8-state model is shown to provide accurate acoustic response predictions for small-amplitude pilot inputs and to abate runtime by a factor of approximately 104, thus enabling acoustic predictions in generalized maneuvering flight that are significantly faster than real time. The 8-state model is subsequently used to demonstrate the use of linear system tools for the dynamic analysis of the coupled rotorcraft flight dynamics and acoustics.
{"title":"Linearized Models of the Coupled Rotorcraft Flight Dynamics and Acoustics for Real-Time Noise Prediction","authors":"Umberto Saetti, Batin Bugday, Joseph F. Horn, Kenneth S. Brentner","doi":"10.4050/jahs.69.022002","DOIUrl":"https://doi.org/10.4050/jahs.69.022002","url":null,"abstract":"This article demonstrates the linearization of the coupled rotorcraft flight dynamics and aeroacoustics to provide real-time acoustic predictions in generalized maneuvering flight. To demonstrate the methodology, the study makes use of a nonlinear simulation model of a generic utility helicopter (PSUHeloSim) that is coupled with an aeroacoustic solver based on a marching cubes algorithm. A periodic equilibrium of the coupled rotorcraft flight dynamics and acoustics is first found at a desired flight condition using a modified harmonic balance trim solution method. Next, the nonlinear time-periodic dynamics are linearized about that periodic equilibrium and transformed into an equivalent higher order linear time-invariant system in harmonic decomposition form. Composite aeroacoustic measures are included as an output of this system. To speed up runtime and make control design tractable, the order of these harmonic decomposition models is reduced via residualization to an 8-state model where the states are representative of the rigid-body dynamics of the aircraft. This 8-state model is shown to provide accurate acoustic response predictions for small-amplitude pilot inputs and to abate runtime by a factor of approximately 104, thus enabling acoustic predictions in generalized maneuvering flight that are significantly faster than real time. The 8-state model is subsequently used to demonstrate the use of linear system tools for the dynamic analysis of the coupled rotorcraft flight dynamics and acoustics.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"59 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135158839","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The high fatality rate of autogyros in the 1990s sparked academic research into autogyro performance, stability and control, and handling qualities. This has included limited study on the inverse simulation of autogyros. The conducted research relied on the use of a modified version of the Generic Inverse Simulation Algorithm (GENISA), which used an iteratively recalculated inverse simulation time step to account for the variability in rotor speed throughout maneuvers. This does not allow for prediction of maneuver completion time, though, significantly increasing computational workload when developing ADS-33E mission task element maneuver models. The research conducted in this article presents a further modified inverse simulation algorithm, based on GENISA, which allows a constant inverse simulation time step to be utilized. Robustness analysis of the inverse simulation algorithm, using a mathematical model of the longitudinal dynamics of a two-seat Montgomerie–Parsons autogyro, showed it is robust enough to analyze realistic medium (60 mph) and high-speed (80 mph) longitudinal pop-up and pop-down maneuvers. More importantly, the constant time step in the algorithm allows for prediction of maneuver completion time, significantly reducing workload when conducting handling qualities assessment.
{"title":"Inverse Simulation of Autogyros","authors":"Matthew G. Gallup","doi":"10.4050/jahs.68.042001","DOIUrl":"https://doi.org/10.4050/jahs.68.042001","url":null,"abstract":"The high fatality rate of autogyros in the 1990s sparked academic research into autogyro performance, stability and control, and handling qualities. This has included limited study on the inverse simulation of autogyros. The conducted research relied on the use of a modified version of the Generic Inverse Simulation Algorithm (GENISA), which used an iteratively recalculated inverse simulation time step to account for the variability in rotor speed throughout maneuvers. This does not allow for prediction of maneuver completion time, though, significantly increasing computational workload when developing ADS-33E mission task element maneuver models. The research conducted in this article presents a further modified inverse simulation algorithm, based on GENISA, which allows a constant inverse simulation time step to be utilized. Robustness analysis of the inverse simulation algorithm, using a mathematical model of the longitudinal dynamics of a two-seat Montgomerie–Parsons autogyro, showed it is robust enough to analyze realistic medium (60 mph) and high-speed (80 mph) longitudinal pop-up and pop-down maneuvers. More importantly, the constant time step in the algorithm allows for prediction of maneuver completion time, significantly reducing workload when conducting handling qualities assessment.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"44 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70219428","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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