Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16894
Stefan Görlich, Rainer Arelt, Jan-Christoph Arent
The H160-B is the latest recently certified helicopter from Airbus Helicopters with extensive use of composite materials in the airframe. In this paper an overview of the fuselage architecture and its design will be provided. During the design phase emphasis was laid on close cooperation between all the involved engineering disciplines like architecture, design, stress, tooling, manufacturing simulation and production. Target was to achieve smaller tolerances resulting in better fit of the parts during assembly, increase first time right and show compliance with the latest airworthiness requirements. For composite parts this process will be shown using the examples of a main frame in prepreg technology and the Upper Deck Framework in RTM technology. The substantiation of the airframe was based on the similar new structure approach with analytical tools for numerical simulation that have been supported by tests of novel design features.
{"title":"H160 Composite Fuselage: Multidisciplinary Approach","authors":"Stefan Görlich, Rainer Arelt, Jan-Christoph Arent","doi":"10.4050/f-0077-2021-16894","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16894","url":null,"abstract":"\u0000 The H160-B is the latest recently certified helicopter from Airbus Helicopters with extensive use of composite materials in the airframe. In this paper an overview of the fuselage architecture and its design will be provided. During the design phase emphasis was laid on close cooperation between all the involved engineering disciplines like architecture, design, stress, tooling, manufacturing simulation and production. Target was to achieve smaller tolerances resulting in better fit of the parts during assembly, increase first time right and show compliance with the latest airworthiness requirements. For composite parts this process will be shown using the examples of a main frame in prepreg technology and the Upper Deck Framework in RTM technology. The substantiation of the airframe was based on the similar new structure approach with analytical tools for numerical simulation that have been supported by tests of novel design features.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123951254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16795
S. Fasiello, P. Masarati, M. Jump
This paper presents the results of a pilot-in-the-loop experiment performed to investigate the efficacy of a pilot induced oscillation (PIO) or adverse rotorcraft-pilot coupling (RPC) real-time detection method, to be implemented as an in-cockpit warning system. A test pilot performed a number of simulated flights inside the Heliflight-R simulator at the University of Liverpool. Two handling qualities (HQ) mission task element (MTE) maneuvers were chosen, namely Precision Hover and Lateral Reposition. The baseline dynamics were those of a FLIGHTLAB BO105-like helicopter model, as used in previous tests; changes in rate limits were introduced to induce the pilot-vehicle system (PVS) to be more RPC/PIO prone, and to observe pilot’s adaptation to these variations causing system instabilities during the chosen MTEs. To objectively measure the severity of the PIO encountered during the tests, the PhaseAggression Criterion (PAC) has been used. This method has been developed to allow for real-time PIO detection in order to provide the information inside the cockpit. In addition, pilot subjective ratings were collected, by using the HQs, PIO and Pilot Workload rating scales. Overall, the results show a good correlation between objective and subjective evaluations, and that it is possible to detect PIOs in real-time. The information can be provided to the pilot by means of visual, aural or haptic cues, which is the work the authors are currently carrying out.
{"title":"Evaluation of the Phase-Aggression Criterion for PIO Detection in Real-time ","authors":"S. Fasiello, P. Masarati, M. Jump","doi":"10.4050/f-0077-2021-16795","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16795","url":null,"abstract":"\u0000 This paper presents the results of a pilot-in-the-loop experiment performed to investigate the efficacy of a pilot induced oscillation (PIO) or adverse rotorcraft-pilot coupling (RPC) real-time detection method, to be implemented as an in-cockpit warning system. A test pilot performed a number of simulated flights inside the Heliflight-R simulator at the University of Liverpool. Two handling qualities (HQ) mission task element (MTE) maneuvers were chosen, namely Precision Hover and Lateral Reposition. The baseline dynamics were those of a FLIGHTLAB BO105-like helicopter model, as used in previous tests; changes in rate limits were introduced to induce the pilot-vehicle system (PVS) to be more RPC/PIO prone, and to observe pilot’s adaptation to these variations causing system instabilities during the chosen MTEs. To objectively measure the severity of the PIO encountered during the tests, the PhaseAggression Criterion (PAC) has been used. This method has been developed to allow for real-time PIO detection in order to provide the information inside the cockpit. In addition, pilot subjective ratings were collected, by using the HQs, PIO and Pilot Workload rating scales. Overall, the results show a good correlation between objective and subjective evaluations, and that it is possible to detect PIOs in real-time. The information can be provided to the pilot by means of visual, aural or haptic cues, which is the work the authors are currently carrying out.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125134947","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16742
Calvin Lu, Justin Blanco, R. Celi, R. Gentili, B. Hatfield, Hyuk Oh, Jessica Mohlar, Ann C. Vanleer
Assessment of operator support technology is of great concern in order to enhance pilots’ safety and performance. Accordingly, the development of the Terrain Obstacle Avoidance Display (TOAD) guidance system is a specific example of such technology, and the present study was conducted to examine if TOAD decreases the operator’s mental workload, allowing for better decision-making capacity under conditions of stress, such as that induced by diminished cues during exposure to degraded visual environments (DVE). Specifically, we examined rotorcraft pilots’ cognitive workload during simulated flight with this visual assistive technology to understand the impact of TOAD on mental workload under variable conditions of challenge using a suite of physiological sensors, subjective ratings of work and flight performance. Collectively, the results for the biophysiological markers and subjective ratings revealed a reduction of the pilot’s cognitive workload when flying with the assistance of TOAD relative to flight without such assistance. In addition, the employment of assistive technology resulted in a trend toward a greater reduction of collisions. Overall, the results provide evidence of the effectiveness of TOAD assistive technology to enhance pilot safety and performance.
{"title":"Assessment of Augmented Operator's Mental Workload with Visual Assistive Technology in Simulated Rotorcraft Piloting Tasks","authors":"Calvin Lu, Justin Blanco, R. Celi, R. Gentili, B. Hatfield, Hyuk Oh, Jessica Mohlar, Ann C. Vanleer","doi":"10.4050/f-0077-2021-16742","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16742","url":null,"abstract":"\u0000 Assessment of operator support technology is of great concern in order to enhance pilots’ safety and performance. Accordingly, the development of the Terrain Obstacle Avoidance Display (TOAD) guidance system is a specific example of such technology, and the present study was conducted to examine if TOAD decreases the operator’s mental workload, allowing for better decision-making capacity under conditions of stress, such as that induced by diminished cues during exposure to degraded visual environments (DVE). Specifically, we examined rotorcraft pilots’ cognitive workload during simulated flight with this visual assistive technology to understand the impact of TOAD on mental workload under variable conditions of challenge using a suite of physiological sensors, subjective ratings of work and flight performance. Collectively, the results for the biophysiological markers and subjective ratings revealed a reduction of the pilot’s cognitive workload when flying with the assistance of TOAD relative to flight without such assistance. In addition, the employment of assistive technology resulted in a trend toward a greater reduction of collisions. Overall, the results provide evidence of the effectiveness of TOAD assistive technology to enhance pilot safety and performance.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125237157","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16817
Andrew Lavoie
Appropriate consideration of tolerances is critical to the design and manufacture of products that meet customer requirements and defined cost targets. Tolerance analysis is most commonly conducted at the individual part or sub-assembly level utilizing basic stack-up methods (worst-case analysis) to ensure the producibility of the assembled product. A worst-case analysis assumes that each dimension in the stack-up will be manufactured on the extreme end or limit of its assigned tolerance (max or min) in such a way that all tolerances become additive. This usually results in tighter than required drawing tolerances being assigned to guarantee the product can be assembled. Modern day manufacturing processes focus on targeting the nominal dimensional value, so it is safe to assume that a higher number of parts will be produced closer to the nominal value than parts produced at the extreme end of the tolerance range. When evaluating the tolerance stack-up of a larger assembly with many parts additional tolerance analysis methods apply (Root Sum Squared, RSS), and a worst-case analysis becomes more costly and less meaningful. The RSS method of tolerance analysis takes into consideration manufacturing targets and applies normal distribution methods to assess more likely tolerance results, allowing relaxed drawing tolerances to be assigned while still maintaining a high level of confidence in a successful assembly. For analysis of complex systems or installations, tolerance studies using more sophisticated approaches to deal with variation such as Monte Carlo statistical analysis is required. Variational Tolerance Analysis (VTA) tools available today allow a typical Monte Carlo tolerance simulation to be visualized by the designer through 3-dimensional real time manufacturing simulations and sensitivity analysis. This in turn simplifies the development process and allows better identification of tolerance drivers within a large system installation; analysis of the geometric effect of tolerances within the installation; and the ability to quickly iterate the analysis to optimize designs for producibility and lower cost. In this paper, the use of VTA is assessed and quantified to form a business case for further investment by Lockheed Martin. In the course of this work, VTA has been evaluated both before and after final designs were released to manufacturing. Before final designs are released VTA can be used for design optimization (i.e. build before you build simulations), part sequencing studies, or to gain insight into the assembly/installation process enabling advanced planning to take place up front. VTA can also address challenges discovered after final designs have been released to manufacturing and parts are on hand (i.e. during the build) such as: assembly issues, out of spec part disposition, and to inform manufacturing of any special tooling or part rework considerations aiding in corrective action or risk mitigation plans. Cost savings to
{"title":"Lichten Award Paper: Variational Tolerance Analysis (VTA) - Design and Manufacturing Optimization Using Statistical Simulation","authors":"Andrew Lavoie","doi":"10.4050/f-0077-2021-16817","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16817","url":null,"abstract":"\u0000 Appropriate consideration of tolerances is critical to the design and manufacture of products that meet customer requirements and defined cost targets. Tolerance analysis is most commonly conducted at the individual part or sub-assembly level utilizing basic stack-up methods (worst-case analysis) to ensure the producibility of the assembled product. A worst-case analysis assumes that each dimension in the stack-up will be manufactured on the extreme end or limit of its assigned tolerance (max or min) in such a way that all tolerances become additive. This usually results in tighter than required drawing tolerances being assigned to guarantee the product can be assembled. Modern day manufacturing processes focus on targeting the nominal dimensional value, so it is safe to assume that a higher number of parts will be produced closer to the nominal value than parts produced at the extreme end of the tolerance range. When evaluating the tolerance stack-up of a larger assembly with many parts additional tolerance analysis methods apply (Root Sum Squared, RSS), and a worst-case analysis becomes more costly and less meaningful. The RSS method of tolerance analysis takes into consideration manufacturing targets and applies normal distribution methods to assess more likely tolerance results, allowing relaxed drawing tolerances to be assigned while still maintaining a high level of confidence in a successful assembly. For analysis of complex systems or installations, tolerance studies using more sophisticated approaches to deal with variation such as Monte Carlo statistical analysis is required. Variational Tolerance Analysis (VTA) tools available today allow a typical Monte Carlo tolerance simulation to be visualized by the designer through 3-dimensional real time manufacturing simulations and sensitivity analysis. This in turn simplifies the development process and allows better identification of tolerance drivers within a large system installation; analysis of the geometric effect of tolerances within the installation; and the ability to quickly iterate the analysis to optimize designs for producibility and lower cost. \u0000In this paper, the use of VTA is assessed and quantified to form a business case for further investment by Lockheed Martin. In the course of this work, VTA has been evaluated both before and after final designs were released to manufacturing. Before final designs are released VTA can be used for design optimization (i.e. build before you build simulations), part sequencing studies, or to gain insight into the assembly/installation process enabling advanced planning to take place up front. VTA can also address challenges discovered after final designs have been released to manufacturing and parts are on hand (i.e. during the build) such as: assembly issues, out of spec part disposition, and to inform manufacturing of any special tooling or part rework considerations aiding in corrective action or risk mitigation plans. \u0000Cost savings to ","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125265120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16758
S. Jung, Sung-Boo Hong, J. Bae, Seonguk Hong, Jae-Sang Park
A rotor-body coupled vibration analysis is performed for a coaxial compound lift offset (LO) helicopter. The vehicle is featured by two-bladed counterrotating rotors, main wing, and auxiliary propulsions installed at each wing tip. The fuselage analysis model is constructed considering the existing designs of conventional helicopters and tilt rotors, while the blade structural design is established modifying the original platform of XH-59A blades. As many as 17 free vibrating modes are used to represent the airframe motions after conducting a convergence test on the vibration behavior of the rotor. An in-house structural design optimization framework based on the evolutionary algorithm is employed to systematically search the best suited combinations of the objective function while meeting all the design constraints set from the static and structural dynamics perspectives. The resulting property values of the optimized configuration are correlated with those by XH-59A. The predicted results on the performance show in good agreement with the flight test data of XH-59A. The trim, loads and vibration responses are examined using either isolated coaxial LO or compound coaxial LO rotors. Key results showing the beneficial effects of LO rotor in both configurations are discussed with the shaft-fixed or shaft-free conditions of the compound helicopter in high speed flights.
{"title":"Rotor-Body Coupled Vibration Analysis of a High-Speed Lift Offset Coaxial Rotor","authors":"S. Jung, Sung-Boo Hong, J. Bae, Seonguk Hong, Jae-Sang Park","doi":"10.4050/f-0077-2021-16758","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16758","url":null,"abstract":"\u0000 A rotor-body coupled vibration analysis is performed for a coaxial compound lift offset (LO) helicopter. The vehicle is featured by two-bladed counterrotating rotors, main wing, and auxiliary propulsions installed at each wing tip. The fuselage analysis model is constructed considering the existing designs of conventional helicopters and tilt rotors, while the blade structural design is established modifying the original platform of XH-59A blades. As many as 17 free vibrating modes are used to represent the airframe motions after conducting a convergence test on the vibration behavior of the rotor. An in-house structural design optimization framework based on the evolutionary algorithm is employed to systematically search the best suited combinations of the objective function while meeting all the design constraints set from the static and structural dynamics perspectives. The resulting property values of the optimized configuration are correlated with those by XH-59A. The predicted results on the performance show in good agreement with the flight test data of XH-59A. The trim, loads and vibration responses are examined using either isolated coaxial LO or compound coaxial LO rotors. Key results showing the beneficial effects of LO rotor in both configurations are discussed with the shaft-fixed or shaft-free conditions of the compound helicopter in high speed flights.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"167 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125802832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16897
J. Lua, Ethan Fulghum, Xiaodong Cui, Jian Xiao, S. Kariyawasam, C. Saathoff
This paper presents the characterization of bearing failure mechanisms in composite joints with countersunk bolt by applying an X-ray Computed Tomography (XCT) technique and a developed bearing failure model to build the physical mechanisms into the framework of continuum damage mechanics (CDM) in our composite bolted and bonded analysis tool for Abaqus (CB2ATA). The high-fidelity XCT was explored for the detection and characterization of bearing failure in bolted composite components without removing the fastener, which could introduce significant scatter in XCT scan due to its high density, compared with lightweight carbon fiber reinforced polymer (CFRP) composite laminates. A static bearing model was also developed for the damaged material response in the bearing region based on a micromechanics analysis in the longitudinal and transverse directions. In this study, single shear bearing (SSB) tests was firstly executed with XCT scan, and then progressive failure analyses were performed to explore the effects of bolt failure on the interaction of the intra- and inter-ply damages. The predicted load-displacement response was compared with experimental measurement, and the simulated failure patterns were compared with the XCT images. A new design was proposed using the enhanced analysis tool to achieve a dominant bearing failure mechanism on the basis of the current SSB test.
{"title":"A Combined X-Ray CT and Mechanistic Characterization of Bearing Failure Mechanisms in Bolted Composite Components","authors":"J. Lua, Ethan Fulghum, Xiaodong Cui, Jian Xiao, S. Kariyawasam, C. Saathoff","doi":"10.4050/f-0077-2021-16897","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16897","url":null,"abstract":"\u0000 This paper presents the characterization of bearing failure mechanisms in composite joints with countersunk bolt by applying an X-ray Computed Tomography (XCT) technique and a developed bearing failure model to build the physical mechanisms into the framework of continuum damage mechanics (CDM) in our composite bolted and bonded analysis tool for Abaqus (CB2ATA). The high-fidelity XCT was explored for the detection and characterization of bearing failure in bolted composite components without removing the fastener, which could introduce significant scatter in XCT scan due to its high density, compared with lightweight carbon fiber reinforced polymer (CFRP) composite laminates. A static bearing model was also developed for the damaged material response in the bearing region based on a micromechanics analysis in the longitudinal and transverse directions. In this study, single shear bearing (SSB) tests was firstly executed with XCT scan, and then progressive failure analyses were performed to explore the effects of bolt failure on the interaction of the intra- and inter-ply damages. The predicted load-displacement response was compared with experimental measurement, and the simulated failure patterns were compared with the XCT images. A new design was proposed using the enhanced analysis tool to achieve a dominant bearing failure mechanism on the basis of the current SSB test.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126035979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16688
Chengjian He, J. Baeder, Jeewoong Kim, C. Ware, S. Yang, Y. Jung
Interest in eVTOL air vehicles has increased significantly in recent years. Most development efforts for eVTOL aircraft have addressed conventional performance objectives. However, the acoustic noise remains a critical aspect that must be dealt with due to its significant impact on operations. This paper summarizes a study of eVTOL rotor acoustic noise variation using a CFD augmented comprehensive rotorcraft modeling and simulation tool combined with acoustic analysis that was validated against measured eVTOL drone rotor noise data. The paper presents a thorough parametric investigation of the variation of the rotor/propeller acoustic signature with emphasis on the broadband noise that often dominates in eVTOL rotor/propeller operation. The parametric study has investigated the effect of a range of rotor parameters, including number of rotor blades, rotor solidity, tip Mach number, blade planform (e.g., chord distribution), etc. The study has revealed important acoustic characteristics of eVTOL rotors. Several findings from the study are fundamentally unique to eVTOL rotors, which provide physical insight into supporting low noise eVTOL rotor/propeller design and development.
{"title":"eVTOL Rotor Noise Study Using Combined Comprehensive Modeling with Acoustic Analysis","authors":"Chengjian He, J. Baeder, Jeewoong Kim, C. Ware, S. Yang, Y. Jung","doi":"10.4050/f-0077-2021-16688","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16688","url":null,"abstract":"\u0000 Interest in eVTOL air vehicles has increased significantly in recent years. Most development efforts for eVTOL aircraft have addressed conventional performance objectives. However, the acoustic noise remains a critical aspect that must be dealt with due to its significant impact on operations. This paper summarizes a study of eVTOL rotor acoustic noise variation using a CFD augmented comprehensive rotorcraft modeling and simulation tool combined with acoustic analysis that was validated against measured eVTOL drone rotor noise data. The paper presents a thorough parametric investigation of the variation of the rotor/propeller acoustic signature with emphasis on the broadband noise that often dominates in eVTOL rotor/propeller operation. The parametric study has investigated the effect of a range of rotor parameters, including number of rotor blades, rotor solidity, tip Mach number, blade planform (e.g., chord distribution), etc. The study has revealed important acoustic characteristics of eVTOL rotors. Several findings from the study are fundamentally unique to eVTOL rotors, which provide physical insight into supporting low noise eVTOL rotor/propeller design and development.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130008848","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16686
James H. Stephenson, B. Cheung, Nikolas S. Zawodny, D. Sargent, B. Sim, Natasha L. Schatzman
Unmanned Aerial Vehicle (UAV) designs typically have aerodynamic configurations that result in complex aerodynamic and acoustic conditions, such as wing and propeller interaction. In response, the Aerodynamic and Acoustic Rotorprop Test (AART) Program was implemented, a primary objective of which was to determine the aerodynamics and acoustics related to an auxiliary propulsor mounted behind an isolated wing in the National Full-Scale Aerodynamics Complex (NFAC) 40-by 80-Foot Wind Tunnel. Three configurations (no wing, half wing, and full wing) were tested, with conditions including variation of the propeller speed, wind tunnel Mach number, and yaw. The acoustic setup, processing, and analysis are discussed along with the known issues for this complex data set. The interaction of upstream bodies and the resulting substantial increase in acoustic emissions are detailed.
{"title":"Aeroacoustic Measurements from the Aerodynamic and Acoustic Rotorprop Test (AART) in the National Full-Scale Aerodynamics Complex (NFAC) 40- by 80-Foot Wind Tunnel ","authors":"James H. Stephenson, B. Cheung, Nikolas S. Zawodny, D. Sargent, B. Sim, Natasha L. Schatzman","doi":"10.4050/f-0077-2021-16686","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16686","url":null,"abstract":"\u0000 Unmanned Aerial Vehicle (UAV) designs typically have aerodynamic configurations that result in complex aerodynamic and acoustic conditions, such as wing and propeller interaction. In response, the Aerodynamic and Acoustic Rotorprop Test (AART) Program was implemented, a primary objective of which was to determine the aerodynamics and acoustics related to an auxiliary propulsor mounted behind an isolated wing in the National Full-Scale Aerodynamics Complex (NFAC) 40-by 80-Foot Wind Tunnel. Three configurations (no wing, half wing, and full wing) were tested, with conditions including variation of the propeller speed, wind tunnel Mach number, and yaw. The acoustic setup, processing, and analysis are discussed along with the known issues for this complex data set. The interaction of upstream bodies and the resulting substantial increase in acoustic emissions are detailed.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"352 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131459700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16843
Umberto Saetti, J. Rogers
This paper demonstrates the extension of the harmonic decomposition methodology, originally developed for rotorcraft applications, to the study of the nonlinear time-periodic dynamics of flapping-wing flight. A harmonic balance algorithm based on harmonic decomposition is successfully applied to find the periodic equilibrium and approximate linear time-invariant dynamics about that equilibrium of the vertical and longitudinal dynamics of a hawk moth. These approximate linearized models are validated through simulations against the original nonlinear time-periodic dynamics. Dynamic stability using the linear models is assessed and compared to that predicted using the averaged dynamics. In addition, modal participation factors are computed to quantify the influence of the higher harmonics on the flight dynamic modes of motion. The study shows that higher harmonics play a key role in the overall dynamics of f lapping-wing flight. The higher harmonics are shown to induce a vibrational stabilization mechanism that increases the pitch damping and stiffness while reducing the speed stability. This mechanism results in the stabilization of the pitch oscillation mode and thus of the longitudinal hovering cubic. As such, the findings of this study suggest that if a hovering vehicle is excited by periodic forcing at sufficiently high frequency and amplitude, its hovering flight dynamics may become stable.
{"title":"Linear Time-Invariant Models of the Dynamics of Flapping-Wing Flight","authors":"Umberto Saetti, J. Rogers","doi":"10.4050/f-0077-2021-16843","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16843","url":null,"abstract":"\u0000 This paper demonstrates the extension of the harmonic decomposition methodology, originally developed for rotorcraft applications, to the study of the nonlinear time-periodic dynamics of flapping-wing flight. A harmonic balance algorithm based on harmonic decomposition is successfully applied to find the periodic equilibrium and approximate linear time-invariant dynamics about that equilibrium of the vertical and longitudinal dynamics of a hawk moth. These approximate linearized models are validated through simulations against the original nonlinear time-periodic dynamics. Dynamic stability using the linear models is assessed and compared to that predicted using the averaged dynamics. In addition, modal participation factors are computed to quantify the influence of the higher harmonics on the flight dynamic modes of motion. The study shows that higher harmonics play a key role in the overall dynamics of f lapping-wing flight. The higher harmonics are shown to induce a vibrational stabilization mechanism that increases the pitch damping and stiffness while reducing the speed stability. This mechanism results in the stabilization of the pitch oscillation mode and thus of the longitudinal hovering cubic. As such, the findings of this study suggest that if a hovering vehicle is excited by periodic forcing at sufficiently high frequency and amplitude, its hovering flight dynamics may become stable.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115937312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16899
Biqiang Xu
Gear load is transmitted by the engaged gear teeth. The load distribution on the engaged tooth surfaces directly determines gear tooth stress status and service life. The contact pattern, gear tooth contact pressure distribution, directly alters the maximum contact and bending stresses, is critical for drive system designs. For a real gear train, the deformations of gear blank, bearing, housing, etc. contribute to contact pressure distribution. It consequently changes local contact pressure and bending stress. To accurately predict the gear contact pressure and bending stress in service, the interaction of whole gear train components needs to be modeled in the gear tooth contact analysis. It is not computational efficient for general purpose FEA packages. Transmission3D (Calyx) is designed for gear contact pattern simulation for given gear tooth surface geometry. When the contact pattern deviates from the design target, how to design a new gear tooth geometry is an open issue and discussed in this paper. Inverse engineering concept with Boussinesq solution is invoked and implemented through Excel macro for gear tooth surface microgeometry design. The design iteration based on this developed method is fast and low cost for gear pattern development.
{"title":"Quick Iteration Algorithm for Cylindrical Gear Contact Pattern Development","authors":"Biqiang Xu","doi":"10.4050/f-0077-2021-16899","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16899","url":null,"abstract":"\u0000 Gear load is transmitted by the engaged gear teeth. The load distribution on the engaged tooth surfaces directly determines gear tooth stress status and service life. The contact pattern, gear tooth contact pressure distribution, directly alters the maximum contact and bending stresses, is critical for drive system designs. For a real gear train, the deformations of gear blank, bearing, housing, etc. contribute to contact pressure distribution. It consequently changes local contact pressure and bending stress. To accurately predict the gear contact pressure and bending stress in service, the interaction of whole gear train components needs to be modeled in the gear tooth contact analysis. It is not computational efficient for general purpose FEA packages. Transmission3D (Calyx) is designed for gear contact pattern simulation for given gear tooth surface geometry. When the contact pattern deviates from the design target, how to design a new gear tooth geometry is an open issue and discussed in this paper. Inverse engineering concept with Boussinesq solution is invoked and implemented through Excel macro for gear tooth surface microgeometry design. The design iteration based on this developed method is fast and low cost for gear pattern development.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"103 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125696069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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