Proceedings of the Vertical Flight Society 78th Annual Forum最新文献

Experimental Evaluation of Multi-Rotor Aerodynamic Interactions 多旋翼气动相互作用的实验评价

Proceedings of the Vertical Flight Society 78th Annual Forum Pub Date : 2022-05-10 DOI: 10.4050/f-0078-2022-17467

Daley Wylie, Abraham Atte, Juergen Rauleder

{"title":"Experimental Evaluation of Multi-Rotor Aerodynamic Interactions","authors":"Daley Wylie, Abraham Atte, Juergen Rauleder","doi":"10.4050/f-0078-2022-17467","DOIUrl":"https://doi.org/10.4050/f-0078-2022-17467","url":null,"abstract":"\u0000 An investigation was performed into the aerodynamic interactions between the rotors of multi-rotor vehicles in different configurations. The effects of these interactions on the thrust and torque of all individual rotors were quantified in wind tunnel tests. Flow visualization and a limited number of particle image velocimetry measurements were conducted to get further insight in to the aerodynamic interactions. The effects of the changes in hub spacings, rotor rotational speeds, and wind speeds were investigated for isolated, tandem, quad-rotor plus and X configurations. The maximum and minimum tip chord Reynolds numbers were 118,000 and 73,000, respectively. Results showed that the aft rotors experienced detrimental aerodynamic interactions in all configurations. In all examined multi-rotor configurations, an increase in the hub spacing caused a decrease in the thrust deficit between the aft rotor and the isolated rotor. However, the differences in the configurations also affected the measured loads. In the tandem configuration, the aft rotor experienced up to 24% reduction in the thrust coefficient at a hub spacing of 2.1R when compared to the isolated rotor at the same rotational frequency and wind speed. The aft-most rotor in the plus configuration experienced as large as a 28% decrease in the thrust coefficient when compared to one of the aft rotors in the X configuration for the same hub spacing and flight conditions. Good correlation was found between these wind tunnel test sand flight tests for the front and side rotors in X and plus configurations (7.9-14.2% difference), but a larger difference of 30-41.9% was found for the aft rotors, which is likely due to the different rotor trim conditions.\u0000","PeriodicalId":223727,"journal":{"name":"Proceedings of the Vertical Flight Society 78th Annual Forum","volume":"201 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124288199","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}

引用次数: 0

Analytic Prediction of Rotor Broadband Noise with Serrated Trailing Edges 带锯齿尾缘转子宽带噪声的分析预测

Proceedings of the Vertical Flight Society 78th Annual Forum Pub Date : 2022-05-10 DOI: 10.4050/f-0078-2022-17432

Sicheng Li, Seongkyu Lee

{"title":"Analytic Prediction of Rotor Broadband Noise with Serrated Trailing Edges","authors":"Sicheng Li, Seongkyu Lee","doi":"10.4050/f-0078-2022-17432","DOIUrl":"https://doi.org/10.4050/f-0078-2022-17432","url":null,"abstract":"\u0000 Trailing-edge serrations are known to be an effective way to reduce broadband noise on wing sections, but their noise reduction capabilities on rotorcraft have not been fully understood. This paper develops a new approach to analytically predicting and investigating broadband noise of rotors with serrated trailing edges. To achieve rotorcraft broadband noise predictions, we extend Lyu and Ayton's semi-infinite serrated wing model to include the finite blade span, the modified scattering coefficient, and the spanwise observer distance. The validations show good agreements with experimental data for serrated trailing-edge noise of a wing section, a hovering rotor, and a forward-flight rotor. Next, the effects of serration parameters on rotor broadband noise are studied. For optimal and realistic rotor broadband noise reduction, the desirable design of a serrated-blade rotor has the serration height to wavelength ratio of 2, the radial range of serrations from 50% blade span to the tip. It is also found that the sine-wave, chopped peak, or saw-tooth serration shapes reduce noise most among various shapes that are considered. Finally, noise reduction with serrations is applied to urban air mobility (UAM) aircraft. A 6-passenger eVTOL quadrotor is found to have more than 9 dB noise reduction potential with serrated trailing edges, where higher noise reductions are observed with higher tip speeds and fewer blades. Serrated-blade quadrotors are found to have the dipole broadband noise directivity, and noise reductions are observed at all observer angles.\u0000","PeriodicalId":223727,"journal":{"name":"Proceedings of the Vertical Flight Society 78th Annual Forum","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116654034","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}

引用次数: 1

Revisiting Legacy Weight Relationships Using Machine Learning Techniques 使用机器学习技术重访遗留权重关系

Proceedings of the Vertical Flight Society 78th Annual Forum Pub Date : 2022-05-10 DOI: 10.4050/f-0078-2022-17494

J. Vegh, A. Milligan

{"title":"Revisiting Legacy Weight Relationships Using Machine Learning Techniques","authors":"J. Vegh, A. Milligan","doi":"10.4050/f-0078-2022-17494","DOIUrl":"https://doi.org/10.4050/f-0078-2022-17494","url":null,"abstract":"\u0000 This paper investigates the application of K-Means Clustering algorithms to traditional aircraft conceptual-level weight estimation techniques. As a proof of concept demonstration, application was narrowed to fuselage basic weight estimation with expansion to additional component weights as a planned follow on activity. A variety of weight sources were parsed and curated to produce a large, diverse dataset consisting of 82 separate aircraft with a corresponding new universal baseline regression to compare against. A K-Means Clustering algorithm was then employed that sorted aircraft into groupings based on configuration as well as topology and created an associated regression for each grouping. Configuration-based groupings utilized information such as a high-level abstraction of the structural layout as well as whether the aircraft is a fixed-wing or rotary-wing vehicle. Topology-cased groupings utilized information such as landing gear location and possession of a cargo ramp or wing. The configuration-based groupings showed modest improvement compared to the baseline regression while the topology-based groupings consistently outperformed both the baseline regression as well as the configuration-based regressions. Under all conditions, a subset of the data associated with fixed-wing aircraft was shown to be an outlier in regards to error as a result of a large range of weight and speed scales, as well as possible secondary pressurization impacts. Special treatment of the winged dataset led to further reduction in error based on unique design features, presenting an overall fuselage weight estimation methodology that leverages machine learning algorithms that can improve and inform existing best practices.\u0000","PeriodicalId":223727,"journal":{"name":"Proceedings of the Vertical Flight Society 78th Annual Forum","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125894983","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}

引用次数: 0

Improved Initial and Boundary Conditions for Hovering Rotor CFD Simulations 悬停旋翼CFD模拟的改进初始和边界条件

Proceedings of the Vertical Flight Society 78th Annual Forum Pub Date : 2022-05-10 DOI: 10.4050/f-0078-2022-17474

Feilin Jia, Qiqi Wang, P. Spalart

{"title":"Improved Initial and Boundary Conditions for Hovering Rotor CFD Simulations","authors":"Feilin Jia, Qiqi Wang, P. Spalart","doi":"10.4050/f-0078-2022-17474","DOIUrl":"https://doi.org/10.4050/f-0078-2022-17474","url":null,"abstract":"\u0000 The new flow fields originate in a 2012 paper by Spalart (Ref. 1), which addresses the far-field behavior induced by a momentum source, such as a hovering rotor or a static jet. This model incorporates entrainment into the turbulent far wake, and supersedes the time-honored model based on a sink field. In the present study, a new initial condition as well as boundary condition based on a modified version of the above far-field model are investigated by unsteady simulations of the XV-15 rotor in hovering flight condition at collective pitch angle ? = 10?. The idea is to inject an approximation to the rotor's wake under it. From our results, compared to the freestream initial condition, the far-field model based new initial condition can quickly establish the low-speed induced flow and achieve faster convergence of thrust and torque to statistically steady state. The chaotic starting vortex can be effectively flushed out by the new initial condition to prevent the oscillations of thrust due to blade-vortex interaction shown in the simulation from the freestream initial condition. Results of the modified far-field model as a far-field boundary condition to hovering f light in multiple reduced computational domains are also presented. Although the new boundary condition doesn't show evident speedup in convergence of thrust and torque, its wake can be developed much faster than the freestream boundary condition due to its prescribed velocity field at the boundary. This new initial and boundary condition could be beneficial to simulations of multi-rotor aircraft.\u0000","PeriodicalId":223727,"journal":{"name":"Proceedings of the Vertical Flight Society 78th Annual Forum","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123749505","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}

引用次数: 0

Physics and Improved Simulations for Computational Modeling of Synthetic Jets 合成射流计算模型的物理和改进模拟

Proceedings of the Vertical Flight Society 78th Annual Forum Pub Date : 2022-05-10 DOI: 10.4050/f-0078-2022-17582

Aaron Crawford, Marilyn J. Smith

{"title":"Physics and Improved Simulations for Computational Modeling of Synthetic Jets","authors":"Aaron Crawford, Marilyn J. Smith","doi":"10.4050/f-0078-2022-17582","DOIUrl":"https://doi.org/10.4050/f-0078-2022-17582","url":null,"abstract":"\u0000 With the rise of active flow control techniques several approaches of flow reattachment have been studied, including the use of direct momentum injection through a zero-net mass flow synthetic jet. The focus of this paper is to further understand the role of turbulence in the physics of synthetic jets and the sensitivity of external crossflow on the prediction of the jet and its downstream behavior while in cross flow. Computational results are correlated with recent experimental data obtained by the U.S. Army. The full actuator geometry is computationally modeled and to develop unsteady and phase-averaged boundary conditions at the jet/outer mold line interface at the relevant spatial and temporal levels. This study also considers the effect of turbulence model, as well as the associated turbulent quantities, and their influence in the prediction of the local synthetic jet flowfield in cross flow. Results indicate that turbulent fluctuations in three-dimensional flows with large eddy simulation wakes are required to predict the jet interactional effects. The external crossflow has a significant impact on the magnitude of the turbulent characteristics, but the trends observed in experiments are captured with the additional of turbulence in the jet.\u0000","PeriodicalId":223727,"journal":{"name":"Proceedings of the Vertical Flight Society 78th Annual Forum","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126954953","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}

引用次数: 0

Hover Dynamics and Flight Control of a UAM-Scale Quadcopter with Hybrid RPM and Collective Pitch Control 混合转速和集体俯仰控制的uam级四轴飞行器的悬停动力学和飞行控制

Proceedings of the Vertical Flight Society 78th Annual Forum Pub Date : 2022-05-10 DOI: 10.4050/f-0078-2022-17540

Ariel Walter, T. Berger, M. McKay, R. Niemiec, F. Gandhi

{"title":"Hover Dynamics and Flight Control of a UAM-Scale Quadcopter with Hybrid RPM and Collective Pitch Control","authors":"Ariel Walter, T. Berger, M. McKay, R. Niemiec, F. Gandhi","doi":"10.4050/f-0078-2022-17540","DOIUrl":"https://doi.org/10.4050/f-0078-2022-17540","url":null,"abstract":"\u0000 Hover trim and dynamic analyses were performed on a UAM-scale quadcopter with both variable rotor speed and variable collective blade pitch. The bare-airframe dynamics were first considered at three different hover trim points, where power consumption is increased to improve authority. The control and stability derivatives were examined at each trim point and an increase in base RPM caused increased authority for pitch inputs (and decreased authority for RPM inputs) in thrust-dominated axes. Explicit model following control laws wre then optimized using CONDUIT® to meet ADS-33E-PRF handling qualities specifications. Design margin optimization was then performed on each axis. Heave and yaw responses of the linearized system were examined for the three trim points with either RPM or pitch control. It was found that pitch-control outperformed RPM-control in heave, while the opposite was true for yaw. Hybrid control mixing was considered using a complementary filter, so that it uses pitch actuators for short-term responses, and RPM for trim. Effects of changes in motor time constant and complementary filter cutoff frequency were examined. The benefits of hybrid control were demonstrated through simulations that involved transition between trim points. Hybrid control required lower maximum power during thrust-driven maneuvers by allowing the aircraft to accelerate using pitch actuators, and recovers the original stall margin by using the rotor speed to re-trim. For a drop-off of 176 lbs of payload, hybrid control provided 5.0% lower trim power than pitch control with the reduced weight. Hybrid control also allowed a 3.9% reduction in power compared to pitch control at a flight speed of 30 kts.\u0000","PeriodicalId":223727,"journal":{"name":"Proceedings of the Vertical Flight Society 78th Annual Forum","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115532410","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}

引用次数: 1

Verification and Validation (V&V) of Numerical Helicopter Airframe Model for Dynamic and Static Finite Element Analysis 直升机机体动态与静态有限元数值模型的验证与验证(V&V)

Proceedings of the Vertical Flight Society 78th Annual Forum Pub Date : 2022-05-10 DOI: 10.4050/f-0078-2022-17622

Junhyeon Seo, Courtney Fisher, S. Kaudur, M. Agarwal, R. Kapania, Larry Pilkington

{"title":"Verification and Validation (V&V) of Numerical Helicopter Airframe Model for Dynamic and Static Finite Element Analysis","authors":"Junhyeon Seo, Courtney Fisher, S. Kaudur, M. Agarwal, R. Kapania, Larry Pilkington","doi":"10.4050/f-0078-2022-17622","DOIUrl":"https://doi.org/10.4050/f-0078-2022-17622","url":null,"abstract":"\u0000 In this research, Columbia Helicopters, Inc. (CHI) and Virginia Polytechnic Institute and State University collaborated to conduct the numerical model Verification and Validation (V&V) of a Global Finite Element Model (GFEM) of a tandem rotor helicopter developed by CHI. The V&V process is followed based on the ASME V&V guide for computational solid mechanics. The target mathematical model is verified with a convergence study by improving the mesh density and quality. For the model validation, the authors compare the dynamic and static finite element analyses (FEA) with the experimental results. During 1980s, NASA along with some industry participants pursued a Design Analysis Methods for Vibration (DAMVIBS) project to develop and validate accurate FEM based framework for dynamic analysis of helicopters. This work utilizes NASA's DAMVIBS project results to validate the dynamic responses for vertical, lateral, and pitch loading cases. In addition, for static validation, the authors have used CHI's static pull experimental data. This data includes measured strain values at various locations on the fuselage structure. Both dynamic and static FEA results match within 10 % of the DAMVIBS and static pull experimental results, respectively. Thus, this study successfully validates the reliability of the numerical model.\u0000","PeriodicalId":223727,"journal":{"name":"Proceedings of the Vertical Flight Society 78th Annual Forum","volume":"101 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115578314","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}

引用次数: 0

Fabrication, Testing, and Comparative Analysis of Lithium Sulfur and Lithium-Ion Electrochemistries 锂硫和锂离子电化学的制造、测试和比较分析

Proceedings of the Vertical Flight Society 78th Annual Forum Pub Date : 2022-05-10 DOI: 10.4050/f-0078-2022-17531

Emily Fisler, A. Datta

{"title":"Fabrication, Testing, and Comparative Analysis of Lithium Sulfur and Lithium-Ion Electrochemistries","authors":"Emily Fisler, A. Datta","doi":"10.4050/f-0078-2022-17531","DOIUrl":"https://doi.org/10.4050/f-0078-2022-17531","url":null,"abstract":"This paper addresses the fundamental barriers of eVTOL aircraft- energy and power. Lithium sulfur and lithium-ion coin cells were fabricated with identical overhead for a clear and consistent comparison of specific energy and power. The characteristics measured were discharge cycles, cycle life, impedance under conditions unique to electric vertical takeoff and landing aircraft namely high C-Rates, half cycles, and high transients. Equivalent circuit models were developed and validated to predict the steady-state and transient behavior of these cells. The key conclusions are lithium sulfur provides more than twice the specific energy of lithium-ion up to currents of almost C/2. At 1C, it is comparable. Above 1C it drops drastically and by 4C the energy vanishes almost entirely. This is traced to an order of magnitude higher impedance of these cells. The price to pay for high energy is low cycle life. However, it appear this problem can be eliminated by half cycles. The dynamic behavior of lithium sulfur is richer in comparison to lithium-ion. The response is still capacitative, hence first order, but the complex Warburg and constant phase elements have far greater influence. The behavior is harder to model as it does not fit neatly into linear equivalent circuits. The key conclusion is that lithium sulfur appears to be an attractive alternative to lithium-ion with characteristics that have significant ramifications on future eVTOL design and infrastructure.","PeriodicalId":223727,"journal":{"name":"Proceedings of the Vertical Flight Society 78th Annual Forum","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122832118","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}

引用次数: 0

Experimental Evaluation of Panel-Method-Based Path Planning for eVTOL in A Scaled Urban Environment 城市环境下基于面板法的eVTOL路径规划实验评价

Proceedings of the Vertical Flight Society 78th Annual Forum Pub Date : 2022-05-10 DOI: 10.4050/f-0078-2022-17536

Z. Bilgin, M. Bronz, I. Yavrucuk

引用次数: 1

Variation in Helicopter Noise During Approach Maneuvers 直升机进近机动过程中的噪声变化

Proceedings of the Vertical Flight Society 78th Annual Forum Pub Date : 2022-05-10 DOI: 10.4050/f-0078-2022-17438

Damaris Zachos, Lauren Weist, K. Brentner, Eric Greenwood

引用次数: 0