Computational fluid dynamics simulations of the flow around the ROtor Body INteraction (ROBIN)-mod7 fuselage with pressure-sensitive paint rotor are conducted using an immersed boundary method and an actuator surface model in OpenFOAM. The ROBIN-mod7 fuselage is represented by the immersed boundary method, while the unsteady rotor is modeled using the actuator surface model. A comprehensive analysis of the generic helicopter configuration is carried out for the hovering flight condition; the isolated fuselage is simulated to provide its baseline aerodynamics, and the isolated rotor and rotor–fuselage cases are studied to measure the rotor performance in hover and the fuselage effect on the performance. The validation of each test case is conducted against both experimental measurements and computational data from the literature. The surface pressure data from the isolated fuselage case shows good agreement with the experimental measurements. Also, the rotor performance predicted on the isolated and installed rotors (rotor–fuselage) has excellent agreement with the reference data; in particular, the performance data on the installed rotor agree with the experimental data better than the previous numerical study does. The fuselage effect has been analyzed by comparing the isolated rotor and rotor–fuselage datasets. The computational effort for different grid levels of each test case is provided. Overall, the results have demonstrated an equivalent level of accuracy compared to the previous high-fidelity simulation results at their fraction of setup and computational expenses.
{"title":"Simulation of Rotorcraft Fuselage with Rotor Effects Using an Immersed Boundary Method","authors":"Jack Heesung Park, D. Linton, B. Thornber","doi":"10.4050/jahs.68.022006","DOIUrl":"https://doi.org/10.4050/jahs.68.022006","url":null,"abstract":"Computational fluid dynamics simulations of the flow around the ROtor Body INteraction (ROBIN)-mod7 fuselage with pressure-sensitive paint rotor are conducted using an immersed boundary method and an actuator surface model in OpenFOAM. The ROBIN-mod7 fuselage is represented by the immersed boundary method, while the unsteady rotor is modeled using the actuator surface model. A comprehensive analysis of the generic helicopter configuration is carried out for the hovering flight condition; the isolated fuselage is simulated to provide its baseline aerodynamics, and the isolated rotor and rotor–fuselage cases are studied to measure the rotor performance in hover and the fuselage effect on the performance. The validation of each test case is conducted against both experimental measurements and computational data from the literature. The surface pressure data from the isolated fuselage case shows good agreement with the experimental measurements. Also, the rotor performance predicted on the isolated and installed rotors (rotor–fuselage) has excellent agreement with the reference data; in particular, the performance data on the installed rotor agree with the experimental data better than the previous numerical study does. The fuselage effect has been analyzed by comparing the isolated rotor and rotor–fuselage datasets. The computational effort for different grid levels of each test case is provided. Overall, the results have demonstrated an equivalent level of accuracy compared to the previous high-fidelity simulation results at their fraction of setup and computational expenses.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70218672","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}
To characterize the interactions between rotorcraft and ground obstacles when tackling modern and emerging problems such as shipboard landings and urban air mobility, first-principles computational models offer the ability to perform design and analytical studies while resolving detailed flow features. However, the cost of Navier–Stokes methods with very high resolution is, for the most part, only tractable for research use cases. Conversely, midfidelity potential-based methods are cost-effective but may not capture important physics that occur near the rotor blades. Hybrid approaches that couple Navier–Stokes and potential solvers have recently been developed, which provide the ability to resolve complex physics with a Navier–Stokes solution while employing a potential solver to resolve far-wake effects for which it is well-suited. This research discusses the impact of new improvements to and best practices for the hybrid Navier–Stokes/free-wake solver OVERFLOW-CHARM applied to rotors in ground effect. Predictions of rotor performance and flow features are compared with experimental data for microscale and subscale rotors. Rotor performance is predicted within 6% of a conventional computational fluid dynamics simulation at approximately 20% of the computational cost and predicted flow features correlate well to experimental flow visualization.
{"title":"Physics and Accuracy of Dual-Solver Simulations of Rotors in Ground Effect","authors":"A. Moushegian, Marilyn J. Smith","doi":"10.4050/jahs.68.012010","DOIUrl":"https://doi.org/10.4050/jahs.68.012010","url":null,"abstract":"To characterize the interactions between rotorcraft and ground obstacles when tackling modern and emerging problems such as shipboard landings and urban air mobility, first-principles computational models offer the ability to perform design and analytical studies while resolving detailed flow features. However, the cost of Navier–Stokes methods with very high resolution is, for the most part, only tractable for research use cases. Conversely, midfidelity potential-based methods are cost-effective but may not capture important physics that occur near the rotor blades. Hybrid approaches that couple Navier–Stokes and potential solvers have recently been developed, which provide the ability to resolve complex physics with a Navier–Stokes solution while employing a potential solver to resolve far-wake effects for which it is well-suited. This research discusses the impact of new improvements to and best practices for the hybrid Navier–Stokes/free-wake solver OVERFLOW-CHARM applied to rotors in ground effect. Predictions of rotor performance and flow features are compared with experimental data for microscale and subscale rotors. Rotor performance is predicted within 6% of a conventional computational fluid dynamics simulation at approximately 20% of the computational cost and predicted flow features correlate well to experimental flow visualization.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70218889","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 wingtip-mounted propeller configuration is widely used in many aircraft, particularly owing to the emergence of urban air mobility. This paper focuses on analyzing the aeroacoustic properties of a wingtip-mounted tractor propeller by understanding the aerodynamic interaction between the two geometric components. Computational fluid dynamics based on Reynolds-averaged Navier–Stokes equations were used to calculate the flow field and aerodynamic loads on a wingtip-mounted propeller model, and the results were compared with experimental data for validation. The resulting surface pressure was fed as input data for the acoustic analysis performed using a Ffowcs Williams–Hawkings equation-based acoustic solver at multiple angles of attack. The presence of the wing significantly increased the propeller noise along the rotational axis. With increasing angle of attack, the propeller noise increased further. By contrast, the wing noise decreased with the angle of attack due to propeller wake dissipation, leading to only a small increase in the maximum total noise.
翼尖螺旋桨结构广泛应用于许多飞机，特别是由于城市空中机动性的出现。本文通过了解翼尖螺旋桨和翼尖螺旋桨之间的气动相互作用，重点分析了翼尖螺旋桨的气动声学特性。采用基于reynolds -average Navier-Stokes方程的计算流体力学方法，对翼尖螺旋桨模型的流场和气动载荷进行了计算，并与实验数据进行了对比验证。得到的表面压力作为输入数据，使用基于Ffowcs williams - hawkins方程的多攻角声学求解器进行声学分析。机翼的存在显著增加了螺旋桨沿旋转轴的噪音。随着迎角的增大，螺旋桨噪声进一步增大。相比之下，由于螺旋桨尾流耗散，机翼噪声随迎角减小，最大总噪声仅小幅增加。
{"title":"Aeroacoustic and Aerodynamic Investigation of a Wingtip-Mounted Tractor Propeller","authors":"Dilhara Jayasundara, Y. Jung, J. Baeder","doi":"10.4050/jahs.68.012011","DOIUrl":"https://doi.org/10.4050/jahs.68.012011","url":null,"abstract":"The wingtip-mounted propeller configuration is widely used in many aircraft, particularly owing to the emergence of urban air mobility. This paper focuses on analyzing the aeroacoustic properties of a wingtip-mounted tractor propeller by understanding the aerodynamic interaction between the two geometric components. Computational fluid dynamics based on Reynolds-averaged Navier–Stokes equations were used to calculate the flow field and aerodynamic loads on a wingtip-mounted propeller model, and the results were compared with experimental data for validation. The resulting surface pressure was fed as input data for the acoustic analysis performed using a Ffowcs Williams–Hawkings equation-based acoustic solver at multiple angles of attack. The presence of the wing significantly increased the propeller noise along the rotational axis. With increasing angle of attack, the propeller noise increased further. By contrast, the wing noise decreased with the angle of attack due to propeller wake dissipation, leading to only a small increase in the maximum total noise.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70218939","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}
In this paper, the geometrically exact beam model and aeroelastic solution methods for composite rotor blades in forward flight by the latest variational asymptotic beam sectional analysis (VABS) have been employed. The geometrically exact beam equations of motion in the mixed variational form and the latest VABS are used to deal with one-dimensional blade analysis and the structural property of blade cross section, respectively. The methods can be used for the aeroelastic solution of composite rotor blades with arbitrary cross-sectional shape and material distribution, large deflections and significant nonclassical effects such as cross-sectional warping, transverse shear deformation, and elastic couplings caused by anisotropic material properties. The Peters–He finite state dynamic inflow model and the Peters finite state airloads theory are used to calculate the induced velocity and blade airloads, respectively. An auto-pilot trim scheme is used for calculating the blade pitch controls to meet the trim requirements. The convergence issue encountered when solving the geometrically exact, mixed variational aeroelastic equations in time domain has been successfully addressed. The values of the empirical parameters in the auto-pilot trim scheme for the presented aeroelastic model have been properly selected. The accuracy of the presented aeroelastic modeling and solution methods has been verified against the SA349/2 flight-test data. The influence of transverse shear deformation on the aeroelastic response of composite rotor blades was also investigated, indicating that this effect has a nonnegligible influence on the aeroelastic response of the five different kinds of elastically coupled hingeless composite rotors investigated in this paper.
{"title":"Geometrically Exact Beam-Based Aeroelastic Modeling and Solution of Composite Rotor Blades in Forward Flight","authors":"L. Shang, P. Xia, D. Hodges, C. Lin","doi":"10.4050/jahs.68.022011","DOIUrl":"https://doi.org/10.4050/jahs.68.022011","url":null,"abstract":"In this paper, the geometrically exact beam model and aeroelastic solution methods for composite rotor blades in forward flight by the latest variational asymptotic beam sectional analysis (VABS) have been employed. The geometrically exact beam equations of motion in the mixed variational form and the latest VABS are used to deal with one-dimensional blade analysis and the structural property of blade cross section, respectively. The methods can be used for the aeroelastic solution of composite rotor blades with arbitrary cross-sectional shape and material distribution, large deflections and significant nonclassical effects such as cross-sectional warping, transverse shear deformation, and elastic couplings caused by anisotropic material properties. The Peters–He finite state dynamic inflow model and the Peters finite state airloads theory are used to calculate the induced velocity and blade airloads, respectively. An auto-pilot trim scheme is used for calculating the blade pitch controls to meet the trim requirements. The convergence issue encountered when solving the geometrically exact, mixed variational aeroelastic equations in time domain has been successfully addressed. The values of the empirical parameters in the auto-pilot trim scheme for the presented aeroelastic model have been properly selected. The accuracy of the presented aeroelastic modeling and solution methods has been verified against the SA349/2 flight-test data. The influence of transverse shear deformation on the aeroelastic response of composite rotor blades was also investigated, indicating that this effect has a nonnegligible influence on the aeroelastic response of the five different kinds of elastically coupled hingeless composite rotors investigated in this paper.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70219004","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}
T. Berger, C. Blanken, Jeff A. Lusardi, M. Tischler, J. Horn
To provide the government with independent control-system design, handling qualities analysis, and simulation research capabilities in support of Future Vertical Lift, the U.S. Army Combat Capabilities Development Command Aviation & Missile Center has developed generic high-fidelity flight-dynamics models of several advanced high-speed rotorcraft configurations. One of the configurations modeled is a lift offset coaxial-compound helicopter with a pusher propeller. Full flight envelope explicit model following control laws were designed for the generic coaxial-compound helicopter using a multiobjective optimization approach to meet a comprehensive set of stability, handling qualities, and performance specifications. Helicopter response types were used for hover/low-speed, while typical fixed-wing response types (normal acceleration and sideslip command) were used at high speed. The control laws were evaluated in a piloted simulation experiment at the NASA Ames Vertical Motion Simulator using a series of previously developed high-speed handling qualities demonstration maneuvers. This paper discusses the control laws and the results of the piloted handling qualities assessment, which showed assigned Level 1 handling qualities for six of the seven maneuvers evaluated.
{"title":"Coaxial-Compound Helicopter Flight Control Design and High-Speed Handling Qualities Assessment","authors":"T. Berger, C. Blanken, Jeff A. Lusardi, M. Tischler, J. Horn","doi":"10.4050/jahs.67.032008","DOIUrl":"https://doi.org/10.4050/jahs.67.032008","url":null,"abstract":"To provide the government with independent control-system design, handling qualities analysis, and simulation research capabilities in support of Future Vertical Lift, the U.S. Army Combat Capabilities Development Command Aviation & Missile Center has developed generic high-fidelity flight-dynamics models of several advanced high-speed rotorcraft configurations. One of the configurations modeled is a lift offset coaxial-compound helicopter with a pusher propeller. Full flight envelope explicit model following control laws were designed for the generic coaxial-compound helicopter using a multiobjective optimization approach to meet a comprehensive set of stability, handling qualities, and performance specifications. Helicopter response types were used for hover/low-speed, while typical fixed-wing response types (normal acceleration and sideslip command) were used at high speed. The control laws were evaluated in a piloted simulation experiment at the NASA Ames Vertical Motion Simulator using a series of previously developed high-speed handling qualities demonstration maneuvers. This paper discusses the control laws and the results of the piloted handling qualities assessment, which showed assigned Level 1 handling qualities for six of the seven maneuvers evaluated.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70217327","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 data-driven clustering algorithm based on proper orthogonal decomposition was applied to assess the scatter found in the UH-60A wind tunnel airloads measurements. Upon verifying the capability of the algorithm, pushrod loads, blade surface pressures, sectional loads, and torsional moments were analyzed. Spatial eigenmodes resulting from the decomposition provided the optimal basis; projection of the individual cycles onto the high singular value modes allowed visualizing the statistical distribution of data over the entire azimuth. While not all cases showed furcation in the data, the bimodal distribution was found in the high-thrust cases, where statistically normal distribution is generally assumed. Consequent clustering of the measured cycles produced an excellent correlation among clusters found in the pushrod loads, blade surface pressure, and torsional moment that suggests a common source for furcation in the data. The cycles assigned to one group repeatedly showed distinguishable variations from the other group in terms of the presence/absence of a dynamic stall vortex, azimuthal occurrence of the stall, chordwise location of separation, reattachment, and so on. When one of the clusters is smaller in size compared to the other, the conventional phase average obscured all the intricate features even when the loads are substantially higher than the larger cluster. In general, clustering the dataset when warranted showed not only higher peak loads but also lower variance for both the clusters across the entire azimuth compared to the conventional simple phase-average results. Computational simulations were conducted using CREATETM-AV Helios towards understanding the underlying flow field. Misinterpreted earlier as under-/overpredictive when compared with the simple phase-average data, Helios results consistently showed significantly improved correlation with one of the two clusters. Combining the clustered results and the flow visualization provided by Helios, aperiodicity in the spatial location and the strength of both the trim tab vortices and tip vortices have been hypothesized as potential sources of furcation.
{"title":"Data-Driven Analysis of Cycle-to-Cycle Variations, Scatter, and Furcation in the UH-60A Wind Tunnel Rotor Airloads Measurements","authors":"M. Ramasamy, R. Jain, T. Norman","doi":"10.4050/jahs.67.042011","DOIUrl":"https://doi.org/10.4050/jahs.67.042011","url":null,"abstract":"A data-driven clustering algorithm based on proper orthogonal decomposition was applied to assess the scatter found in the UH-60A wind tunnel airloads measurements. Upon verifying the capability of the algorithm, pushrod loads, blade surface pressures, sectional loads, and torsional moments were analyzed. Spatial eigenmodes resulting from the decomposition provided the optimal basis; projection of the individual cycles onto the high singular value modes allowed visualizing the statistical distribution of data over the entire azimuth. While not all cases showed furcation in the data, the bimodal distribution was found in the high-thrust cases, where statistically normal distribution is generally assumed. Consequent clustering of the measured cycles produced an excellent correlation among clusters found in the pushrod loads, blade surface pressure, and torsional moment that suggests a common source for furcation in the data. The cycles assigned to one group repeatedly showed distinguishable variations from the other group in terms of the presence/absence of a dynamic stall vortex, azimuthal occurrence of the stall, chordwise location of separation, reattachment, and so on. When one of the clusters is smaller in size compared to the other, the conventional phase average obscured all the intricate features even when the loads are substantially higher than the larger cluster. In general, clustering the dataset when warranted showed not only higher peak loads but also lower variance for both the clusters across the entire azimuth compared to the conventional simple phase-average results. Computational simulations were conducted using CREATETM-AV Helios towards understanding the underlying flow field. Misinterpreted earlier as under-/overpredictive when compared with the simple phase-average data, Helios results consistently showed significantly improved correlation with one of the two clusters. Combining the clustered results and the flow visualization provided by Helios, aperiodicity in the spatial location and the strength of both the trim tab vortices and tip vortices have been hypothesized as potential sources of furcation.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"76 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70218374","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}
An active noise control technology is developed here to reduce the in-plane thickness noise associated with multirotor advanced air mobility Vehicles. The basic concept is that few actuators (e.g., microspeakers) are embedded into the blade surfaces. They emit a loading signal to cancel the thickness noise. This actuation signal is determined via the Ffowcs-Williams–Hawking (FWH) formula. We considered here two inline rotors, and we showed that the FWH-determined actuation signal can produce perfect cancellation at a point target. However, the practical need is to achieve noise reduction over an azimuthal zone, not just a single point. To achieve this zonal noise reduction, an optimization technique is developed to determine the required actuation signal produced by the on-blade distribution of embedded actuators on the two rotors. For the specific geometry considered here, this produced about 9 dB reduction in the in-plane thickness noise during forward flight of the two rotors. We further developed a technology that replaces using a point actuator on each blade by distributed microactuator system to achieve the same noise reduction goal with significantly reduced loading amplitudes per actuator.
{"title":"Active Noise Control of Multirotor Advanced Air Mobility Vehicles","authors":"Samuel Afari, R. Mankbadi","doi":"10.4050/jahs.68.032006","DOIUrl":"https://doi.org/10.4050/jahs.68.032006","url":null,"abstract":"An active noise control technology is developed here to reduce the in-plane thickness noise associated with multirotor advanced air mobility Vehicles. The basic concept is that few actuators (e.g., microspeakers) are embedded into the blade surfaces. They emit a loading signal to cancel the thickness noise. This actuation signal is determined via the Ffowcs-Williams–Hawking (FWH) formula. We considered here two inline rotors, and we showed that the FWH-determined actuation signal can produce perfect cancellation at a point target. However, the practical need is to achieve noise reduction over an azimuthal zone, not just a single point. To achieve this zonal noise reduction, an optimization technique is developed to determine the required actuation signal produced by the on-blade distribution of embedded actuators on the two rotors. For the specific geometry considered here, this produced about 9 dB reduction in the in-plane thickness noise during forward flight of the two rotors. We further developed a technology that replaces using a point actuator on each blade by distributed microactuator system to achieve the same noise reduction goal with significantly reduced loading amplitudes per actuator.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70219144","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 noise radiation of an EC135 Fenestron is investigated by means of flight tests. The noise emission was measured with ground microphones during several different maneuvers. These include hover, rearward flight, and forward flight at different combinations of the side slip angle and the airspeed. In hover, a high level of broadband noise is observed. A comparison with available engine noise data suggested that engine noise is not dominant in hover. In rearward flight, the Fenestron may encounter a relatively clean aerodynamic inflow. However, the measurements do not indicate a reduction in noise radiation of the Fenestron. For rearward flight, a significant increase in main rotor noise is observed. Flights at different combinations of the side slip angle and airspeed show that the Fenestron radiates high levels of tonal noise at high-speed flight at negative side slip. The most likely cause for this is a highly disturbed inflow caused by flow separations of the diffusor outlet edge and the sharp trailing edges of the stator blades. Measurements of the tail boom yaw moment and Fenestron drive shaft torque imply that a reverse flow is possible at medium airspeed, while the Fenestron thrust does not reverse sign. Only at higher airspeeds and negative side slip, it is possible to achieve a thrust reversal in addition to a flow reversal.
{"title":"Experimental Investigation of Fenestron Noise","authors":"W. Olsman","doi":"10.4050/jahs.67.032002","DOIUrl":"https://doi.org/10.4050/jahs.67.032002","url":null,"abstract":"The noise radiation of an EC135 Fenestron is investigated by means of flight tests. The noise emission was measured with ground microphones during several different maneuvers. These include hover, rearward flight, and forward flight at different combinations of the side slip angle and the airspeed. In hover, a high level of broadband noise is observed. A comparison with available engine noise data suggested that engine noise is not dominant in hover. In rearward flight, the Fenestron may encounter a relatively clean aerodynamic inflow. However, the measurements do not indicate a reduction in noise radiation of the Fenestron. For rearward flight, a significant increase in main rotor noise is observed. Flights at different combinations of the side slip angle and airspeed show that the Fenestron radiates high levels of tonal noise at high-speed flight at negative side slip. The most likely cause for this is a highly disturbed inflow caused by flow separations of the diffusor outlet edge and the sharp trailing edges of the stator blades. Measurements of the tail boom yaw moment and Fenestron drive shaft torque imply that a reverse flow is possible at medium airspeed, while the Fenestron thrust does not reverse sign. Only at higher airspeeds and negative side slip, it is possible to achieve a thrust reversal in addition to a flow reversal.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70217603","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}
Aero medical transportation (AMT) services provide transportation of patients, medical teams, and organs for the U.S. healthcare system. Categories of AMT operations include scene response (33%), interfacility transfers (54%), delivering specialty care and organs (13%), and repatriation from outside the United States (statistics not recorded). Scene response is conducted primarily using rotary wing aircraft that can land and takeoff from accident scenes and hospital heliports. Data from 12 publicly available databases were combined to identify AMT vehicles and to generate operational statistics including the number of vehicles, ownership, flight distances, flight frequency, geographic distribution, and the types of airports, air traffic control, and navigation systems used. This information can be used for aircraft design, airport and air traffic control infrastructure assessment and funding allocation, industry sector analysis, and strategic planning.
{"title":"Operational Statistics for Rotary Wing Aero Medical Transportation in the United States (2020)","authors":"L. Sherry, Charlie Wang","doi":"10.4050/jahs.68.022002","DOIUrl":"https://doi.org/10.4050/jahs.68.022002","url":null,"abstract":"Aero medical transportation (AMT) services provide transportation of patients, medical teams, and organs for the U.S. healthcare system. Categories of AMT operations include scene response (33%), interfacility transfers (54%), delivering specialty care and organs (13%), and repatriation from outside the United States (statistics not recorded). Scene response is conducted primarily using rotary wing aircraft that can land and takeoff from accident scenes and hospital heliports. Data from 12 publicly available databases were combined to identify AMT vehicles and to generate operational statistics including the number of vehicles, ownership, flight distances, flight frequency, geographic distribution, and the types of airports, air traffic control, and navigation systems used. This information can be used for aircraft design, airport and air traffic control infrastructure assessment and funding allocation, industry sector analysis, and strategic planning.","PeriodicalId":50017,"journal":{"name":"Journal of the American Helicopter Society","volume":"1 1","pages":""},"PeriodicalIF":1.5,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70218956","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}
T. Berger, C. Blanken, Jeff A. Lusardi, M. Tischler, J. Horn
To provide the government with independent control-system design, handling qualities analysis, and simulation research capabilities in support of Future Vertical Lift, the U.S. Army Combat Capabilities Development Command Aviation & Missile Center has developed generic high-fidelity flight-dynamics models of several advanced high-speed rotorcraft configurations including a tiltrotor. Full-flight envelope explicit model following control laws were designed for the generic tiltrotor using a multiobjective optimization approach to meet a comprehensive set of stability, handling qualities, and performance specifications. Helicopter response types were used for hover/low-speed, while typical fixed-wing response types (normal acceleration and sideslip command) were used at high speed. The control laws were evaluated in a piloted simulation experiment at the NASA Ames Vertical Motion Simulator using a series of previously developed high-speed handling qualities demonstration maneuvers. This paper discusses the control laws and the results of the piloted handling qualities assessment which show overall assigned Level 1 handling qualities in high-speed and Level 2 in transition.
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