Pub Date : 2021-05-10DOI: 10.4050/f-0077-2021-16721
M. Ramasamy, T. Norman, R. Jain
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 pressure, sectional loads, and torsional moments were analyzed. Spatial eigenmodes resulting from the decomposition provided the optimal basis; projection of the individual cycles on to 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, bimodal distribution was found in the high thrust cases, where statistically normal distribution is generally assumed. Consequent clustering of the measured cycles produced excellent correlation among clusters found in the pushrod loads, blade surface pressure, and torsional moment that suggest 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 stall, chordwise location of separation and reattachment etc. When one of the cluster 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 data set 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. Misjudged earlier as under/over-predictive when compared with the simple phase-average data, Helios results consistently showed significantly improved correlation with the smaller 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 also been hypothesized as potential sources of furcation.
{"title":"Does Scatter Matter? Improved Understanding of UH-60A Wind Tunnel Rotor Measurements Using Data-Driven Clustering and CREATE-AV Helios","authors":"M. Ramasamy, T. Norman, R. Jain","doi":"10.4050/f-0077-2021-16721","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16721","url":null,"abstract":"\u0000 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 pressure, sectional loads, and torsional moments were analyzed. Spatial eigenmodes resulting from the decomposition provided the optimal basis; projection of the individual cycles on to 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, bimodal distribution was found in the high thrust cases, where statistically normal distribution is generally assumed. Consequent clustering of the measured cycles produced excellent correlation among clusters found in the pushrod loads, blade surface pressure, and torsional moment that suggest 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 stall, chordwise location of separation and reattachment etc. When one of the cluster 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 data set 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. Misjudged earlier as under/over-predictive when compared with the simple phase-average data, Helios results consistently showed significantly improved correlation with the smaller 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 also been hypothesized as potential sources of furcation.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"50 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":"114979028","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-0077-2021-16810
Paul J. Fardink
Floyd Carlson was a true pioneer and major contributor in the early development and testing of a broad-range of cutting-edge vertical flight aircraft. His contributions are numerous. Starting with the birth of Bell Helicopter in Gardenville, New York (1942-1945), he performed the first flight of every helicopter Bell designed and built until 1960. His biography mirrors the early history of Bell Helicopter. During this time, Carlson became one of the most experienced and renowned helicopter test pilots in the world, testing aircraft which included the Model 30 (1942); Model 47 (1945); HSL-1 Tandem Rotor Helicopter (1953); XV-3 (1955), forerunner of the XV-15 and V-22 Osprey tiltrotors; and XH-40 (1956), prototype of the iconic UH-1 “Huey.” Floyd Carlson’s passion for aviation began with the guidance of his older brother Milton, whose tragic accident and death left an enduring impact on Floyd’s life as he continued to develop and master the techniques of vertical flight.
{"title":"Floyd Carlson: The Legacy and Contributions of One of America's Greatest Rotary Wing Test Pilots","authors":"Paul J. Fardink","doi":"10.4050/f-0077-2021-16810","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16810","url":null,"abstract":"\u0000 Floyd Carlson was a true pioneer and major contributor in the early development and testing of a broad-range of cutting-edge vertical flight aircraft. His contributions are numerous. Starting with the birth of Bell Helicopter in Gardenville, New York (1942-1945), he performed the first flight of every helicopter Bell designed and built until 1960. His biography mirrors the early history of Bell Helicopter. During this time, Carlson became one of the most experienced and renowned helicopter test pilots in the world, testing aircraft which included the Model 30 (1942); Model 47 (1945); HSL-1 Tandem Rotor Helicopter (1953); XV-3 (1955), forerunner of the XV-15 and V-22 Osprey tiltrotors; and XH-40 (1956), prototype of the iconic UH-1 “Huey.” Floyd Carlson’s passion for aviation began with the guidance of his older brother Milton, whose tragic accident and death left an enduring impact on Floyd’s life as he continued to develop and master the techniques of vertical flight.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"1 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":"115169955","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-0077-2021-16751
A. Kelley, Amanda M Hayes, Ryan Mackie
Current scheduling of unmanned aerial system (UAS) operators often allows for 8 hour shifts, where operators are typically exposed to low event rate tasks, thus leading to the occurrence of underload. While a long, rich history of vigilance research exists, few studies have examined the threshold at which performance decrements occur in UAS operators in operational settings and the utility of strategies to mitigate vigilance and performance decrements. This study evaluated the performance thresholds relative to time-on-task during a 4 hour simulated UAS mission. Additionally, this study evaluated the effectiveness of countermeasure strategies (secondary task and ambient lighting) on sustaining performance and vigilance during simulated UAS missions. Finally, the study demonstrated patterns of psychophysiological indicators of operator states (comparing high and low workload). Findings suggest that performance begins to decline after 15 minutes on task and plateaus by 45 minutes on task for both workload conditions. There was insufficient evidence to support any of the countermeasures, yet patterns in EEG are consistent with past findings regarding shifts in perceived workload.
{"title":"Sustaining Performance and Vigilance during Extended Unmanned Aerial System Operations","authors":"A. Kelley, Amanda M Hayes, Ryan Mackie","doi":"10.4050/f-0077-2021-16751","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16751","url":null,"abstract":"\u0000 Current scheduling of unmanned aerial system (UAS) operators often allows for 8 hour shifts, where operators are typically exposed to low event rate tasks, thus leading to the occurrence of underload. While a long, rich history of vigilance research exists, few studies have examined the threshold at which performance decrements occur in UAS operators in operational settings and the utility of strategies to mitigate vigilance and performance decrements. This study evaluated the performance thresholds relative to time-on-task during a 4 hour simulated UAS mission. Additionally, this study evaluated the effectiveness of countermeasure strategies (secondary task and ambient lighting) on sustaining performance and vigilance during simulated UAS missions. Finally, the study demonstrated patterns of psychophysiological indicators of operator states (comparing high and low workload). Findings suggest that performance begins to decline after 15 minutes on task and plateaus by 45 minutes on task for both workload conditions. There was insufficient evidence to support any of the countermeasures, yet patterns in EEG are consistent with past findings regarding shifts in perceived workload.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"15 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":"123090472","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-0077-2021-16888
H. Desmidt, Zhisheng Ai
This paper develops a design code for sizing the major components of a two speed, dual clutch OCG transmission for rotorcraft applications. Furthermore, this design code is integrated into a single main rotor helicopter sizing model to assess any overall system-level performance benefits offered by the two speed transmission. The results of this study show that the two speed variant will always be heavier that the single speed baseline for a given maximum design payload. The results also show that the combined weight of multiple smaller OCG units placed upstream from the combiner stage are significantly lighter than a single OCG located after the combiner. Finally, the results also show that, despite the added weight due to the OCG transmission, the best two speed variant achieved a 20% increase in flight range compared to the single speed baseline carrying the same maximum payload. Hence, the added weight and complexity of the two speed OCG transmission looks like it can indeed "buy it's way onboard".
{"title":"Minimum Weight Design of a Two Speed Dual Clutch Offset Compound Gear Transmission for Rotorcraft Applications","authors":"H. Desmidt, Zhisheng Ai","doi":"10.4050/f-0077-2021-16888","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16888","url":null,"abstract":"\u0000 This paper develops a design code for sizing the major components of a two speed, dual clutch OCG transmission for rotorcraft applications. Furthermore, this design code is integrated into a single main rotor helicopter sizing model to assess any overall system-level performance benefits offered by the two speed transmission. The results of this study show that the two speed variant will always be heavier that the single speed baseline for a given maximum design payload. The results also show that the combined weight of multiple smaller OCG units placed upstream from the combiner stage are significantly lighter than a single OCG located after the combiner. Finally, the results also show that, despite the added weight due to the OCG transmission, the best two speed variant achieved a 20% increase in flight range compared to the single speed baseline carrying the same maximum payload. Hence, the added weight and complexity of the two speed OCG transmission looks like it can indeed \"buy it's way onboard\".\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"59 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":"116794749","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-0077-2021-16735
D. Schrage
The Main Rotor Hub is the design centerpiece for helicopters and other forms of rotorcraft. It has been a very complex mechanical system design in the past, especially for fully articulated rotor systems. Two major efforts have been made to reduce this complexity. First, was the introduction of elastomeric bearings and dampers which have freed articulated rotor hubs from liquid lubrication and extreme mechanical complexity. This has made them economically feasible for designers and manufacturers of articulated helicopters, such as Boeing and Sikorsky in the U.S; Airbus and Leonardo in Europe; and MIL in Russia. However, the major progress in main rotor hubs has been the continuous movement "and search" toward the ideal hingeless and/or bearingless main rotor hubs. Designing the "Ideal Bearingless Main Rotor (BMR)" hub has been akin to seeking the "holy grail." One outside critic of the progress made toward the "Ideal BMR" over the years has been Thomas A. Hanson, who was involved in early designs of the Lockheed hingeless and bearingless rotor hubs in the 1960s. Having tried to go on his own after Lockheed failed and abandoned their hingeless and baringless rotor hubs, e.g. the XH-51A and the AH-56A Cheyenne, Tom revisited the status of rotorcraft hub design in the 1990s. However, due to the "not invented here" syndrome no major helicopter/rotorcraft manufacturer picked up on his innovative solutions. Helicopter/rotorcraft design engineers, especially those addressing aeroelasticity and dynamics, are a very small element in industry and government engineering organizations. The author of this paper was one of these and has been involved in developing, assessing and evaluating helicopter/rotorcraft designs for almost 50 years, e.g. UTTAS, AAH, AH-1 IRB, CH-47D, MDX, OH-58D, and LHX/RAH-66, along with accident investigations. He has also been the Georgia Tech Rotorcraft Design Professor from 1984 to 2019, where he taught and evaluated student design teams. In addition, his D.Sc. research and dissertation thesis under Dr. David A. Peters in 1978 (Schrage, D.P., "Effect of Structural Parameters on the Flap-Lag Forced response of a Rotor Blade in Forward Flight") shed new light on the tradeoffs between rotor loads and stability by developing an eigenvalue and modal decomposition approach. This included the evaluation of the Boeing and Sikorsky UTTAS bearingless tail rotors. This paper will review this search for the Ideal BMR and identify the importance it will play in future BMR designs which will be Cyber Physical Vehicle Systems (CPVS) to meet and satisfy the safety and design requirements of these new complex electrical, mechanical and adaptive control systems.
主旋翼轮毂是直升机和其他形式旋翼飞行器的设计核心。在过去，它一直是一个非常复杂的机械系统设计，特别是对于全铰接转子系统。为了减少这种复杂性，已经做出了两项主要努力。首先，引入了弹性轴承和阻尼器，将铰接式转子轮毂从液体润滑和极端机械复杂性中解放出来。这使得铰接式直升机的设计师和制造商，如美国的波音和西科斯基，在经济上是可行的;欧洲的空客和莱昂纳多;俄罗斯的MIL。然而，主转子轮毂的主要进展是朝着理想的无铰链和/或无轴承主转子轮毂的不断运动和探索。设计“理想无轴承主转子(BMR)”轮毂类似于寻找“圣杯”。多年来，外界对“理想BMR”取得的进展持批评态度的是托马斯·a·汉森(Thomas A. Hanson)，他在20世纪60年代参与了洛克希德公司无铰链和无轴承转子轮毂的早期设计。在洛克希德失败并放弃他们的无铰链和无铰链转子轮毂后，他试图自己去，例如XH-51A和AH-56A夏安，汤姆在20世纪90年代重新审视了旋翼机轮毂设计的现状。然而，由于“不是在这里发明的”综合症，没有主要的直升机/旋翼飞机制造商接受他的创新解决方案。直升机/旋翼机设计工程师，特别是那些研究气动弹性和动力学的工程师，在工业和政府工程组织中是一个非常小的元素。本文作者就是其中之一，近50年来一直参与开发、评估和评估直升机/旋翼机设计，如UTTAS、AAH、AH-1 IRB、CH-47D、MDX、OH-58D和LHX/RAH-66，以及事故调查。1984年至2019年，他还担任佐治亚理工学院旋翼飞机设计教授，在那里他教授和评估学生设计团队。此外，他的博士研究和1978年David a . Peters博士的论文(Schrage, d.p.，“结构参数对前飞中旋翼叶片的扑动滞后强迫响应的影响”)通过发展特征值和模态分解方法，为旋翼载荷和稳定性之间的权衡提供了新的视角。这包括对波音和西科斯基UTTAS无轴承尾桨的评估。本文将回顾对理想BMR的研究，并确定它在未来BMR设计中的重要性，这将是网络物理车辆系统(CPVS)，以满足这些新的复杂电气，机械和自适应控制系统的安全和设计要求。
{"title":"The Search for an Ideal Bearingless Main Rotor (BMR) Design ","authors":"D. Schrage","doi":"10.4050/f-0077-2021-16735","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16735","url":null,"abstract":"\u0000 The Main Rotor Hub is the design centerpiece for helicopters and other forms of rotorcraft. It has been a very complex mechanical system design in the past, especially for fully articulated rotor systems. Two major efforts have been made to reduce this complexity. First, was the introduction of elastomeric bearings and dampers which have freed articulated rotor hubs from liquid lubrication and extreme mechanical complexity. This has made them economically feasible for designers and manufacturers of articulated helicopters, such as Boeing and Sikorsky in the U.S; Airbus and Leonardo in Europe; and MIL in Russia. However, the major progress in main rotor hubs has been the continuous movement \"and search\" toward the ideal hingeless and/or bearingless main rotor hubs. Designing the \"Ideal Bearingless Main Rotor (BMR)\" hub has been akin to seeking the \"holy grail.\" One outside critic of the progress made toward the \"Ideal BMR\" over the years has been Thomas A. Hanson, who was involved in early designs of the Lockheed hingeless and bearingless rotor hubs in the 1960s. Having tried to go on his own after Lockheed failed and abandoned their hingeless and baringless rotor hubs, e.g. the XH-51A and the AH-56A Cheyenne, Tom revisited the status of rotorcraft hub design in the 1990s. However, due to the \"not invented here\" syndrome no major helicopter/rotorcraft manufacturer picked up on his innovative solutions. Helicopter/rotorcraft design engineers, especially those addressing aeroelasticity and dynamics, are a very small element in industry and government engineering organizations. The author of this paper was one of these and has been involved in developing, assessing and evaluating helicopter/rotorcraft designs for almost 50 years, e.g. UTTAS, AAH, AH-1 IRB, CH-47D, MDX, OH-58D, and LHX/RAH-66, along with accident investigations. He has also been the Georgia Tech Rotorcraft Design Professor from 1984 to 2019, where he taught and evaluated student design teams. In addition, his D.Sc. research and dissertation thesis under Dr. David A. Peters in 1978 (Schrage, D.P., \"Effect of Structural Parameters on the Flap-Lag Forced response of a Rotor Blade in Forward Flight\") shed new light on the tradeoffs between rotor loads and stability by developing an eigenvalue and modal decomposition approach. This included the evaluation of the Boeing and Sikorsky UTTAS bearingless tail rotors. This paper will review this search for the Ideal BMR and identify the importance it will play in future BMR designs which will be Cyber Physical Vehicle Systems (CPVS) to meet and satisfy the safety and design requirements of these new complex electrical, mechanical and adaptive control systems.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"22 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":"121049486","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-0077-2021-16748
P. Petit
It is foreseen that in the upcoming application of (electric) urban air taxis, the comfort of ride and especially the experience of motion sickness will play a vital role for acceptance amongst passengers and therefore economic success of these vehicles. For this reason accurate motion sickness prediction models are needed, which later can be employed for e.g. kinetosis-low trajectory generation. Established motion sickness models like the ISO 2631 standard however only take into account the vertical translational axis and no rotational axis. For this reason, the 6-DoF Kamiji motion sickness model is selected and modified in order to circumvent unsatisfactory prediction results with this model. Subsequently the parameters of this model are retuned by employing an optimization approach based on published experimental data. It is then shown that with this approach, the modified Kamiji model is better suited for predicting the motion sickness results of this dataset. In the future, this model shall be tested and validated via a series of flight tests with test subjects in DLR’s BO-105 helicopter.
{"title":"Prediction of Motion Sickness Onset for Vertical Lift Applications ","authors":"P. Petit","doi":"10.4050/f-0077-2021-16748","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16748","url":null,"abstract":"\u0000 It is foreseen that in the upcoming application of (electric) urban air taxis, the comfort of ride and especially the experience of motion sickness will play a vital role for acceptance amongst passengers and therefore economic success of these vehicles. For this reason accurate motion sickness prediction models are needed, which later can be employed for e.g. kinetosis-low trajectory generation. Established motion sickness models like the ISO 2631 standard however only take into account the vertical translational axis and no rotational axis. For this reason, the 6-DoF Kamiji motion sickness model is selected and modified in order to circumvent unsatisfactory prediction results with this model. Subsequently the parameters of this model are retuned by employing an optimization approach based on published experimental data. It is then shown that with this approach, the modified Kamiji model is better suited for predicting the motion sickness results of this dataset. In the future, this model shall be tested and validated via a series of flight tests with test subjects in DLR’s BO-105 helicopter.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"148 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":"123465905","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-0077-2021-16690
Paulo Arias, J. Baeder, Y. Jung
In recent years, the University of Maryland has worked on an asymmetric lift-offset compound helicopter. The configuration consists of a single main rotor helicopter with the addition of two key ways to increase the forward speed: a stubbed wing on the retreating fuselage side, and a slowed down rotor. Experiments and simulations have shown that the novel concept provides improved thrust potential and lift-to-drag ratios in high-speed forward flight. This study aims to determine whether the asymmetric lift-offset configuration also provides aeroacoustic benefits in forward flight in addition to its aerodynamic advantages. The aerodynamic results from previous computational and experimental studies are recreated using the Mercury framework, an in-house CFD solver based on Reynolds-Averaged NavierStokes (RANS). The acoustic analysis is performed using an acoustic code based on the Ffowcs William-Hawkings equation to solve for the noise propagating from the surfaces of the aircraft. It was found that for an advance ratio of 0.5 the wing-lift offset configuration can produce 56.8% more thrust at the same collective angle without any penalties in total noise. When the configurations produce equal thrust it was found that the wing-lift offset case has a 4 dB reduction in maximum overall sound pressure level. At an advance ratio of 0.3 with trim for equivalent thrust between configurations, a 3 dB maximum OASPL reduction was obtained with the inclusion of the wing.
近年来，马里兰大学研究了一种不对称升力偏移复合直升机。该结构由一个主旋翼直升机和两个增加前进速度的关键方式组成:后退机身一侧的短翼和减速旋翼。实验和仿真结果表明，这种新型设计在高速前飞中提高了推力潜力和升阻比。本研究旨在确定非对称升力偏移配置是否在前飞中除了气动优势之外还提供气动声学优势。利用基于reynolds - average NavierStokes (RANS)的内部CFD求解器Mercury框架，重新创建了先前计算和实验研究的空气动力学结果。声学分析使用基于Ffowcs william - hawkins方程的声学编码来求解从飞机表面传播的噪声。研究发现，当推进比为0.5时，在相同的总角度下，翼升偏置结构可以产生56.8%的推力，而不会对总噪声产生任何影响。当两种结构产生相同推力时，发现机翼升力偏移的情况下最大总声压级降低了4 dB。在各配置间的等效推力下，在带装饰的推进比为0.3时，在包含机翼的情况下，最大OASPL降低了3 dB。
{"title":"Aeroacoustic Analysis of Asymmetric Lift-Offset Helicopter in Forward Flight","authors":"Paulo Arias, J. Baeder, Y. Jung","doi":"10.4050/f-0077-2021-16690","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16690","url":null,"abstract":"\u0000 In recent years, the University of Maryland has worked on an asymmetric lift-offset compound helicopter. The configuration consists of a single main rotor helicopter with the addition of two key ways to increase the forward speed: a stubbed wing on the retreating fuselage side, and a slowed down rotor. Experiments and simulations have shown that the novel concept provides improved thrust potential and lift-to-drag ratios in high-speed forward flight. This study aims to determine whether the asymmetric lift-offset configuration also provides aeroacoustic benefits in forward flight in addition to its aerodynamic advantages. The aerodynamic results from previous computational and experimental studies are recreated using the Mercury framework, an in-house CFD solver based on Reynolds-Averaged NavierStokes (RANS). The acoustic analysis is performed using an acoustic code based on the Ffowcs William-Hawkings equation to solve for the noise propagating from the surfaces of the aircraft. It was found that for an advance ratio of 0.5 the wing-lift offset configuration can produce 56.8% more thrust at the same collective angle without any penalties in total noise. When the configurations produce equal thrust it was found that the wing-lift offset case has a 4 dB reduction in maximum overall sound pressure level. At an advance ratio of 0.3 with trim for equivalent thrust between configurations, a 3 dB maximum OASPL reduction was obtained with the inclusion of the wing.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"33 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":"128779520","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-0077-2021-16893
Meaghan Podlaski, F. Gandhi, R. Niemiec, L. Vanfretti
This paper presents the modeling and validation of an electric drivetrain through an object-oriented, equation-based framework that includes aerodynamics, electric machine, power electronic converter and battery models at various levels of detail. The proposed drivetrain model considers different losses in the machine and levels of fidelity for the power source and converters. It is simulated with various maneuvers, aiming to show the effects of modeling simplifications on the behavior of UAMs. These studies show that the level of detail in the motors and power system has significant impact on the dynamic response and power consumption of the system. This is most evident in the cases where the system uses a detailed battery model and in the cases where the switching electrical components are used, creating a torque ripple.
{"title":"Multi-Domain Electric Drivetrain Modeling for UAM-Scale eVTOL Aircraft","authors":"Meaghan Podlaski, F. Gandhi, R. Niemiec, L. Vanfretti","doi":"10.4050/f-0077-2021-16893","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16893","url":null,"abstract":"\u0000 This paper presents the modeling and validation of an electric drivetrain through an object-oriented, equation-based framework that includes aerodynamics, electric machine, power electronic converter and battery models at various levels of detail. The proposed drivetrain model considers different losses in the machine and levels of fidelity for the power source and converters. It is simulated with various maneuvers, aiming to show the effects of modeling simplifications on the behavior of UAMs. These studies show that the level of detail in the motors and power system has significant impact on the dynamic response and power consumption of the system. This is most evident in the cases where the system uses a detailed battery model and in the cases where the switching electrical components are used, creating a torque ripple.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"72 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":"129165455","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}
Luke D. Allen, Joon W. Lim, R. Haehnel, I. Dettwiller
This paper presents advancements in a surrogate-based, rotor blade design optimization framework for improved helicopter performance. The framework builds on previous successes by allowing multiple airfoil sections to designed simultaneously to minimize required rotor power in multiple flight conditions. Rotor power in hover and forward flight, at advance ratio 𝜇 = 0.3, are used as objective functions in a multi-objective genetic algorithm. The framework is constructed using Galaxy Simulation Builder with optimization provided through integration with Dakota. Three independent airfoil sections are morphed using ParFoil and aerodynamic coefficients for the updated airfoil shapes (i.e., lift, drag, moment) are calculated using linear interpolation from a database generated using C81Gen/ARC2D. Final rotor performance is then calculated using RCAS. Several demonstrative optimization case studies were conducted using the UH-60A main rotor. The degrees of freedom for this case are limited to the airfoil camber, camber crest position, thickness, and thickness crest position for each of the sections. The results of the three-segment case study show improvements in rotor power of 4.3% and 0.8% in forward flight and hover, respectively. This configuration also yields greater reductions in rotor power for high advance ratios, e.g., 6.0% reduction at 𝜇 = 0.35, and 8.8% reduction at 𝜇 = 0.4.
{"title":"Helicopter rotor blade multiple-section optimization with performance","authors":"Luke D. Allen, Joon W. Lim, R. Haehnel, I. Dettwiller","doi":"10.21079/11681/41031","DOIUrl":"https://doi.org/10.21079/11681/41031","url":null,"abstract":"This paper presents advancements in a surrogate-based, rotor blade design optimization framework for improved helicopter performance. The framework builds on previous successes by allowing multiple airfoil sections to designed simultaneously to minimize required rotor power in multiple flight conditions. Rotor power in hover and forward flight, at advance ratio 𝜇 = 0.3, are used as objective functions in a multi-objective genetic algorithm. The framework is constructed using Galaxy Simulation Builder with optimization provided through integration with Dakota. Three independent airfoil sections are morphed using ParFoil and aerodynamic coefficients for the updated airfoil shapes (i.e., lift, drag, moment) are calculated using linear interpolation from a database generated using C81Gen/ARC2D. Final rotor performance is then calculated using RCAS. Several demonstrative optimization case studies were conducted using the UH-60A main rotor. The degrees of freedom for this case are limited to the airfoil camber, camber crest position, thickness, and thickness crest position for each of the sections. The results of the three-segment case study show improvements in rotor power of 4.3% and 0.8% in forward flight and hover, respectively. This configuration also yields greater reductions in rotor power for high advance ratios, e.g., 6.0% reduction at 𝜇 = 0.35, and 8.8% reduction at 𝜇 = 0.4.","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"39 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":"125458317","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-0077-2021-16814
M. Smit, Antonio Paesano, L. Hoen-Velterop, Maria L. Montero-Sistiaga
This paper describes the work that was conducted to demonstrate the capability to produce high quality representative magnesium products for vertical lift applications by Laser Powder Bed Fusion (LPBF). An important step in the development was the selection of a metal powder with adequate spreadability for LPBF. Optimum process parameters are required for the production of parts featuring low porosity and low roughness. An efficient optimization approach was applied that enabled the selection of process parameters by analysis of an array of thin wall and block samples from one single build job. After the process parameter selection, benchmark parts were produced for evaluating design rules to print magnesium parts. Demonstrator parts were successfully produced based on a representative light-weight component for Vertical Lift application. A very fine homogeneous microstructure was found at the melt-pool and grain scale. After the removal of the parts from the baseplate, some deformation occurred due to residual stresses.
{"title":"Development of Magnesium Laser Powder Bed Fusion to Manufacture Light-weight Components for Vertical Lift Applications","authors":"M. Smit, Antonio Paesano, L. Hoen-Velterop, Maria L. Montero-Sistiaga","doi":"10.4050/f-0077-2021-16814","DOIUrl":"https://doi.org/10.4050/f-0077-2021-16814","url":null,"abstract":"\u0000 This paper describes the work that was conducted to demonstrate the capability to produce high quality representative magnesium products for vertical lift applications by Laser Powder Bed Fusion (LPBF). An important step in the development was the selection of a metal powder with adequate spreadability for LPBF. Optimum process parameters are required for the production of parts featuring low porosity and low roughness. An efficient optimization approach was applied that enabled the selection of process parameters by analysis of an array of thin wall and block samples from one single build job. After the process parameter selection, benchmark parts were produced for evaluating design rules to print magnesium parts. Demonstrator parts were successfully produced based on a representative light-weight component for Vertical Lift application. A very fine homogeneous microstructure was found at the melt-pool and grain scale. After the removal of the parts from the baseplate, some deformation occurred due to residual stresses.\u0000","PeriodicalId":273020,"journal":{"name":"Proceedings of the Vertical Flight Society 77th Annual Forum","volume":"48 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":"121760670","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：