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Sample records for helicopter fuselage drag

  1. Helicopter fuselage drag - combined computational fluid dynamics and experimental studies

    Batrakov, A.; Kusyumov, A.; Mikhailov, S.; Pakhov, V.; Sungatullin, A.; Valeev, M.; Zherekhov, V.; Barakos, G.

    2015-06-01

    In this paper, wind tunnel experiments are combined with Computational Fluid Dynamics (CFD) aiming to analyze the aerodynamics of realistic fuselage configurations. A development model of the ANSAT aircraft and an early model of the AKTAI light helicopter were employed. Both models were tested at the subsonic wind tunnel of KNRTU-KAI for a range of Reynolds numbers and pitch and yaw angles. The force balance measurements were complemented by particle image velocimetry (PIV) investigations for the cases where the experimental force measurements showed substantial unsteadiness. The CFD results were found to be in fair agreement with the test data and revealed some flow separation at the rear of the fuselages. Once confidence on the CFD method was established, further modifications were introduced to the ANSAT-like fuselage model to demonstrate drag reduction via small shape changes.

  2. Heavy Class Helicopter Fuselage Model Drag Reduction by Active Flow Control Systems

    De Gregorio, F.

    2017-08-01

    A comprehensive experimental investigation of helicopter blunt fuselage drag reduction using active flow control is being carried out within the European Clean Sky program. The objective is to demonstrate the capability of several active flow technologies to decrease fuselage drag by alleviating the flow separation occurring in the rear area of some helicopters. The work is performed on a simplified blunt fuselage at model-scale. Two different flow control actuators are considered for evaluation: steady blowing, unsteady blowing (or pulsed jets). Laboratory tests of each individual actuator are first performed to assess their performance and properties. The fuselage model is then equipped with these actuators distributed in 3 slots located on the ramp bottom edge. This paper addresses the promising results obtained during the wind-tunnel campaign, since significant drag reductions are achieved for a wide range of fuselage angles of attack and yaw angles without detriment of the other aerodynamic characteristics.

  3. Simulation of Flow around Isolated Helicopter Fuselage

    Garipov A.O.

    2013-04-01

    Full Text Available Low fuselage drag has always been a key target of helicopter manufacturers. Therefore, this paper focuses on CFD predictions of the drag of several components of a typical helicopter fuselage. In the first section of the paper, validation of the obtained CFD predictions is carried out using wind tunnel measurements. The measurements were carried out at the Kazan National Research Technical University n.a. A. Tupolev. The second section of the paper is devoted to the analysis of drag contributions of several components of the ANSAT helicopter prototype fuselage using the RANS approach. For this purpose, several configurations of fuselages are considered with different levels of complexity including exhausts and skids. Depending on the complexity of the considered configuration and CFD mesh both the multi-block structured HMB solver and the unstructured commercial tool Fluent are used. Finally, the effect of an actuator disk on the predicted drag is addressed.

  4. TO THE DEVELOPMENT OF AERODYNAMIC SHAPE OF MEDIUM SIZED PERSPECTIVE HELICOPTER FUSELAGE

    2016-01-01

    Full Text Available This paper presents the initial stage of work out of the helicopter body aerodynamic configuration. The main pur- pose of this work is to design the model of the fuselage and to minimize its drag.The analysis of experimental data obtained in TsAGI and other research centers was made at the first stage of the work. All features of flow around parts of the fuselage obtained from experimental data were taken into account. The de- pendencies of the fuselage component drag, such as the bow, fairings exhaust pipes of helicopter, sponsons, and tail sectionof the fuselage, on their form are described in this article.At the second stage the fuselage geometry was created in program SolidWorks. All the features of the flow around various fuselage components derived from the experimental data were considered in designing.The third stage is calculating of fuselage model aerodynamic characteristics. The calculations were made in the program ANSYS CFX (TsAGI License №501024. Boundary conditions were chosen so as to correspond to normal at- mospheric conditions at 1,000 meters with velocity of flight is V = 85 m/s. The output of the hot jet from engines is takinginto account in computation. The purpose of this calculation is to find the optimal angle of the engine exhaust pipe whenthe hot spray does not intersect with the tail and stabilizer and creates the maximum of propulsive force. The volume of the grid in computational domain is approximately 13 million cells.Data analysis has shown that the fuselage has a 20% less drag at cruising flight (аf = -4 ° compared to the original model. The hot jets do not intersect with the tail and stabilizers at cruising flight so the fuselage is protected from overheating.

  5. Helicopter Fuselage Active Flow Control in the Presence of a Rotor

    Martin, Preston B; Overmeyer, Austin D.; Tanner, Philip E.; Wilson, Jacob S.; Jenkins, Luther N.

    2014-01-01

    This work extends previous investigations of active flow control for helicopter fuselage drag and download reduction to include the effects of the rotor. The development of the new wind tunnel model equipped with fluidic oscillators is explained in terms of the previous test results. Large drag reductions greater than 20% in some cases were measured during powered testing without increasing, and in some cases decreasing download in forward flight. As confirmed by Particle Image Velocimetry (PIV), the optimum actuator configuration that provided a decrease in both drag and download appeared to create a virtual (fluidic) boat-tail fairing instead of attaching flow to the ramp surface. This idea of a fluidic fairing shifts the focus of 3D separation control behind bluff bodies from controlling/reattaching surface boundary layers to interacting with the wake flow.

  6. Distribution of Acoustic Power Spectra for an Isolated Helicopter Fuselage

    Kusyumov A.N.

    2016-01-01

    Full Text Available The broadband aerodynamic noise can be studied, assuming isotropic flow, turbulence and decay. Proudman’s approach allows practical calculations of noise based on CFD solutions of RANS or URANS equations at the stage of post processing and analysis of the solution. Another aspect is the broadband acoustic spectrum and the distribution of acoustic power over a range of frequencies. The acoustic energy spectrum distribution in isotropic turbulence is non monotonic and has a maximum at a certain value of Strouhal number. In the present work the value of acoustic power peak frequency is determined using a prescribed form of acoustic energy spectrum distribution presented in papers by S. Sarkar and M. Y. Hussaini and by G. M. Lilley. CFD modelling of the flow around isolated helicopter fuselage model was considered using the HMB CFD code and the RANS equations.

  7. COMPUTING EXPERIMENT FOR ASSESSMENT OF AERODYNAMIC CHARACTERISTICS OF SEPARATE ELEMENTS IN THE STRUCTURE OF THE FUSELAGE OF A HELICOPTER

    V. A. Ivchin

    2015-01-01

    Full Text Available The present publication describes the calculation of helicopter fuselage aerodynamic characteristics and its separate elements, by computing experiment. On the basis of program commercial package CFX ANSYS the technique has been mastered and longitudinal and lateral characteristics of the helicopter fuselage on the various flight modes are calculated.

  8. Navier-Stokes Calculations of Helicopter Fuselage Flowfield and Loads

    M, Costes; Filippone, Antonino; N, Kroll

    1999-01-01

    This paper describes the theoretically basedactivities conducted during the first year of theBrite/Euram Helifuse Porgramme. These activitiesmainly consisted of the numerical prediction ofhelicopter fuselage flowfields with existing Navier-Stokes solvers on a number of pre-selectedcases, taken out...

  9. Capability of State-of-the-Art Navier-Stokes Solvers for the Prediction of Helicopter Fuselage Aerodynamics

    N., Kroll; P., Renzoni; M., Amato

    1998-01-01

    The purpose of this paper is to describe the influence of different Navier-Stokes solvers and grids on the prediction of the global coefficients for a simplified geometry of a helicopter fuselage.......The purpose of this paper is to describe the influence of different Navier-Stokes solvers and grids on the prediction of the global coefficients for a simplified geometry of a helicopter fuselage....

  10. A Coupled Helicopter Rotor/Fuselage Dynamics Model Using Finite Element Multi-body

    Cheng Qi-you

    2016-01-01

    Full Text Available To develop a coupled rotor/flexible fuselage model for vibration reduction studies, the equation of coupled rotor-fuselage is set up based on the theory of multi-body dynamics, and the dynamic analysis model is established with the software MSC.ADMAS and MSC.NASTRAN. The frequencies and vibration acceleration responses of the system are calculated with the model of coupled rotor-fuselage, and the results are compared with those of uncoupled modeling method. Analysis results showed that compared with uncoupled model, the dynamic characteristic obtained by the model of coupled rotor-fuselage are some different. The intrinsic frequency of rotor is increased with the increase of rotational velocities. The results also show that the flying speed has obvious influence on the vibration acceleration responses of the fuselage. The vibration acceleration response in the vertical direction is much higher at the low speed and high speed flight conditions.

  11. Helicopter Non-Unique Trim Strategies for Blade-Vortex Interaction (BVI) Noise Reduction

    Malpica, Carlos; Greenwood, Eric; Sim, Ben W.

    2016-01-01

    An acoustics parametric analysis of the effect of fuselage drag and pitching moment on the Blade-Vortex Interaction (BVI) noise radiated by a medium lift helicopter (S-70UH-60) in a descending flight condition was conducted. The comprehensive analysis CAMRAD II was used for the calculation of vehicle trim, wake geometry and integrated air loads on the blade. The acoustics prediction code PSU-WOPWOP was used for calculating acoustic pressure signatures for a hemispherical grid centered at the hub. This paper revisits the concept of the X-force controller for BVI noise reduction, and investigates its effectiveness on an S-70 helicopter. The analysis showed that further BVI noise reductions were achievable by controlling the fuselage pitching moment. Reductions in excess of 6 dB of the peak BVI noise radiated towards the ground were demonstrated by compounding the effect of airframe drag and pitching moment simultaneously.

  12. Nonlinear Dynamics of a Helicopter Model in Ground Resonance

    Tang, D. M.; Dowell, E. H.

    1985-01-01

    An approximate theoretical method is presented which determined the limit cycle behavior of a helicopter model which has one or two nonlinear dampers. The relationship during unstable ground resonance oscillations between lagging motion of the blades and fuselage motion is discussed. An experiment was carried out on using a helicopter scale model. The experimental results agree with those of the theoretical analysis.

  13. Numerical simulation of helicopter engine plume in forward flight

    Dimanlig, Arsenio C. B.; Vandam, Cornelis P.; Duque, Earl P. N.

    1994-01-01

    Flowfields around helicopters contain complex flow features such as large separated flow regions, vortices, shear layers, blown and suction surfaces and an inherently unsteady flow imposed by the rotor system. Another complicated feature of helicopters is their infrared signature. Typically, the aircraft's exhaust plume interacts with the rotor downwash, the fuselage's complicated flowfield, and the fuselage itself giving each aircraft a unique IR signature at given flight conditions. The goal of this project was to compute the flow about a realistic helicopter fuselage including the interaction of the engine air intakes and exhaust plume. The computations solve the Think-Layer Navier Stokes equations using overset type grids and in particular use the OVERFLOW code by Buning of NASA Ames. During this three month effort, an existing grid system of the Comanche Helicopter was to be modified to include the engine inlet and the hot engine exhaust. The engine exhaust was to be modeled as hot air exhaust. However, considerable changes in the fuselage geometry required a complete regriding of the surface and volume grids. The engine plume computations have been delayed to future efforts. The results of the current work consists of a complete regeneration of the surface and volume grids of the most recent Comanche fuselage along with a flowfield computation.

  14. Stiffened Composite Fuselage Barrel Optimization

    Movva, R. G.; Mittal, A.; Agrawal, K.; Upadhyay, C. S.

    2012-07-01

    In a typical commercial transport aircraft, Stiffened skin panels and frames contribute around 40% of the fuselage weight. In the current study a stiffened composite fuselage skin panel optimization engine is developed for optimization of the layups of composite panels and stringers using Genetic Algorithm (GA). The skin and stringers of the fuselage section are optimized for the strength and the stability requirements. The selection of the GA parameters considered for the optimization is arrived by performing case studies on selected problems. The optimization engine facilitates in carrying out trade studies for selection of the optimum ply layup and material combination for the configuration being analyzed. The optimization process is applied on a sample model and the results are presented.

  15. Drag Reduction by Laminar Flow Control

    Nils Beck

    2018-01-01

    Full Text Available The Energy System Transition in Aviation research project of the Aeronautics Research Center Niedersachsen (NFL searches for potentially game-changing technologies to reduce the carbon footprint of aviation by promoting and enabling new propulsion and drag reduction technologies. The greatest potential for aerodynamic drag reduction is seen in laminar flow control by boundary layer suction. While most of the research so far has been on partial laminarization by application of Natural Laminar Flow (NLF and Hybrid Laminar Flow Control (HLFC to wings, complete laminarization of wings, tails and fuselages promises much higher gains. The potential drag reduction and suction requirements, including the necessary compressor power, are calculated on component level using a flow solver with viscid/inviscid coupling and a 3D Reynolds-Averaged Navier-Stokes (RANS solver. The effect on total aircraft drag is estimated for a state-of-the-art mid-range aircraft configuration using preliminary aircraft design methods, showing that total cruise drag can be halved compared to today’s turbulent aircraft.

  16. Evaluation of Skin Friction Drag for Liner Applications in Aircraft

    Gerhold, Carl H.; Brown, Martha C.; Jasinski, Christopher M.

    2016-01-01

    A parameter that is gaining significance in the evaluation of acoustic liner performance is the skin friction drag induced by air flow over the liner surface. Estimates vary widely regarding the amount of drag the liner induces relative to a smooth wall, from less than a 20% increase to nearly 100%, and parameters such as face sheet perforate hole diameter, percent open area, and sheet thickness are expected to figure prominently in the skin friction drag. Even a small increase in liner drag can impose an economic penalty, and current research is focused on developing 'low drag' liner concepts, with the goal being to approach the skin friction drag of a smooth wall. The issue of skin friction drag takes on greater significance as airframe designers investigate the feasibility of putting sound absorbing liners on the non-lifting surfaces of the wings and fuselage, for the purpose of reducing engine noise reflected and scattered toward observers on the ground. Researchers at the NASA Langley Research Center have embarked on investigations of liner skin friction drag with the aims of: developing a systematic drag measurement capability, establishing the drag of current liners, and developing liners that produce reduced drag without compromising acoustic performance. This paper discusses the experimental procedures that have been developed to calculate the drag coefficient based on the change in momentum thickness and the companion research program being carried out to measure the drag directly using a force balance. Liner samples that are evaluated include a solid wall with known roughness and conventional liners with perforated facesheets of varying hole diameter and percent open area.

  17. Helicopter rotor dynamics and aeroelasticity - Some key ideas and insights

    Friedmann, Peretz P.

    1990-01-01

    Four important current topics in helicopter rotor dynamics and aeroelasticity are discussed: (1) the role of geometric nonlinearities in rotary-wing aeroelasticity; (2) structural modeling, free vibration, and aeroelastic analysis of composite rotor blades; (3) modeling of coupled rotor/fuselage areomechanical problems and their active control; and (4) use of higher-harmonic control for vibration reduction in helicopter rotors in forward flight. The discussion attempts to provide an improved fundamental understanding of the current state of the art. In this way, future research can be focused on problems which remain to be solved instead of producing marginal improvements on problems which are already understood.

  18. Wall temperature control of low-speed body drag

    Lin, J. C.; Ash, R. L.

    1986-01-01

    The use of thermal means to control drag under turbulent boundary layer conditions is examined. Numerical calculations are presented for both skin friction and (unseparated) pressure drag for turbulent boundary-layer flows over a fuselage-like body with wall heat transfer. In addition, thermal control of separation on a bluff body is investigated. It is shown that a total drag reduction of up to 20 percent can be achieved for wall heating with a wall-to-total-freestream temperature ratio of 2. For streamlined slender bodies, partial wall heating of the forebody can produce almost the same order of total drag reduction as the full body heating case. For bluff bodies, the separation delay from partial wall cooling of the afterbody is approximately the same as for the fully cooled body.

  19. Wireless Sensor Network for Helicopter Rotor Blade Vibration Monitoring: Requirements Definition and Technological Aspects

    Sanchez Ramirez, Andrea; Das, Kallol; Loendersloot, Richard; Tinga, Tiedo; Havinga, Paul J.M.; Basu, Biswajit

    The main rotor accounts for the largest vibration source for a helicopter fuselage and its components. However, accurate blade monitoring has been limited due to the practical restrictions on instrumenting rotating blades. The use of Wireless Sensor Networks (WSNs) for real time vibration monitoring

  20. Effects of boundary layer refraction and fuselage scattering on fuselage surface noise from advanced turboprop propellers

    Mcaninch, G. L.; Rawls, J. W., Jr.

    1984-01-01

    An acoustic disturbance's propagation through a boundary layer is discussed with a view to the analysis of the acoustic field generated by a propfan rotor incident to the fuselage of an aircraft. Applying the parallel flow assumption, the resulting partial differential equations are reduced to an ordinary acoustic pressure differential equation by means of the Fourier transform. The methods used for the solution of this equation include those of Frobenius and of analytic continuation; both yield exact solutions in series form. Two models of the aircraft fuselage-boundary layer system are considered, in the first of which the fuselage is replaced by a flat plate and the acoustic field is assumed to be two-dimensional, while in the second the fuselage is a cylinder in a fully three-dimensional acoustic field. It is shown that the boundary layer correction improves theory-data comparisons over simple application of a pressure-doubling rule at the fuselage.

  1. Studies of Aerodynamic Drag.

    1982-12-01

    31. Strouhal number vs Reynolds number - Effect of Wind tunnel Blockage. 150- P ecrit 100- 50k- o present d Qta o Mitry (1977) --Shair et ati (1963) 0...forces measured by the balance. 4.12 Final Tests A comprehensive set of drag measurements was taken with the new drag plates, the drag plates being

  2. Active noise control in fuselage design

    Krakers, L.A.; Tooren, M.J.L. van; Beukers, A.; Berkhof, A.P.; Goeje, M.P. de

    2003-01-01

    To achieve comfortable noise levels inside the passenger cabin, sound damping measures have to be taken to improve the sound insulation properties of the bare airframe. Usually the sound insulation requirements of a passenger cabin are met after the mechanical design of the fuselage structure is

  3. 14 CFR 25.783 - Fuselage doors.

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Fuselage doors. 25.783 Section 25.783 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT AIRWORTHINESS... operated manually; (ii) The powered latch actuators, if installed; and (iii) The relative motion between...

  4. Numerical simulation of turbulent flows past the RoBin helicopter with a four-bladed rotor

    Xu, H.; Mamou, M.; Khalid, M. [National Research Council, Inst. for Aerospace Research, Ottawa, Ontario (Canada)]. E-mail: Hongyi.Xu@nrc.ca

    2003-07-01

    The current paper presents a turbulent flow simulation study past a generic helicopter RoBin with a four-bladed rotor using the Chimera moving grid approach. The aerodynamic performance of the rotor blades and their interactions with the RoBin fuselage are investigated using the k - {omega} SST turbulence model contained in the WIND code. The rotor is configured as a Chimera moving grid in a quasisteady flow field. The rotor blades are rectangular, untapered, linearly twisted and are made from NACA 0012 airfoil profile. The blade motion (rotation and cyclic pitching) schedule is specified in the NASA wind tunnel testing of a generic helicopter RoBin. The aerodynamic radial load distributions in the rotor plane are generated by integrating the pressure on each blade surfaces along the blade chordwise direction. The rotor flow interacts strongly with the flow coming off from the fuselage and thus has a significant impact on helicopter aerodynamic performance. (author)

  5. 78 FR 18224 - Airworthiness Directives; Robinson Helicopter Company Helicopters

    2013-03-26

    ... Airworthiness Directives; Robinson Helicopter Company Helicopters AGENCY: Federal Aviation Administration (FAA... Helicopter Company (Robinson) Model R44 and R44 II helicopters equipped with emergency floats. This AD..., contact Robinson Helicopter Company, 2901 Airport Drive, Torrance, CA 90505; telephone (310) 539-0508; fax...

  6. Composite fuselage crown panel manufacturing technology

    Willden, Kurtis; Metschan, S.; Grant, C.; Brown, T.

    1992-01-01

    Commercial fuselage structures contain significant challenges in attempting to save manufacturing costs with advanced composite technology. Assembly issues, material costs, and fabrication of elements with complex geometry are each expected to drive the cost of composite fuselage structures. Boeing's efforts under the NASA ACT program have pursued key technologies for low-cost, large crown panel fabrication. An intricate bond panel design and manufacturing concepts were selected based on the efforts of the Design Build Team (DBT). The manufacturing processes selected for the intricate bond design include multiple large panel fabrication with the Advanced Tow Placement (ATP) process, innovative cure tooling concepts, resin transfer molding of long fuselage frames, and utilization of low-cost material forms. The process optimization for final design/manufacturing configuration included factory simulations and hardware demonstrations. These efforts and other optimization tasks were instrumental in reducing cost by 18 percent and weight by 45 percent relative to an aluminum baseline. The qualitative and quantitative results of the manufacturing demonstrations were used to assess manufacturing risks and technology readiness.

  7. Advanced Technology Composite Fuselage - Materials and Processes

    Scholz, D. B.; Dost, E. F.; Flynn, B. W.; Ilcewicz, L. B.; Nelson, K. M.; Sawicki, A. J.; Walker, T. H.; Lakes, R. S.

    1997-01-01

    The goal of Boeing's Advanced Technology Composite Aircraft Structures (ATCAS) program was to develop the technology required for cost and weight efficient use of composite materials in transport fuselage structure. This contractor report describes results of material and process selection, development, and characterization activities. Carbon fiber reinforced epoxy was chosen for fuselage skins and stiffening elements and for passenger and cargo floor structures. The automated fiber placement (AFP) process was selected for fabrication of monolithic and sandwich skin panels. Circumferential frames and window frames were braided and resin transfer molded (RTM'd). Pultrusion was selected for fabrication of floor beams and constant section stiffening elements. Drape forming was chosen for stringers and other stiffening elements. Significant development efforts were expended on the AFP, braiding, and RTM processes. Sandwich core materials and core edge close-out design concepts were evaluated. Autoclave cure processes were developed for stiffened skin and sandwich structures. The stiffness, strength, notch sensitivity, and bearing/bypass properties of fiber-placed skin materials and braided/RTM'd circumferential frame materials were characterized. The strength and durability of cocured and cobonded joints were evaluated. Impact damage resistance of stiffened skin and sandwich structures typical of fuselage panels was investigated. Fluid penetration and migration mechanisms for sandwich panels were studied.

  8. Racializing white drag.

    Rhyne, Ragan

    2004-01-01

    While drag is primarily understood as a performance of gender, other performative categories such as race, class, and sexuality create drag meaning as well. Though other categories of identification are increasingly understood as essential elements of drag by performers of color, whiteness remains an unmarked category in the scholarship on drag performances by white queens. In this paper, I argue that drag by white queens must be understood as a performance of race as well as gender and that codes of gender excess are specifically constructed through the framework of these other axes of identity. This essay asks whether white performance by white queens necessarily reinscribes white supremacy through the performance of an unmarked white femininity, or might drag performance complicate (though not necessarily subvert) categories of race as well as gender? In this essay, I will suggest that camp drag performances, through the deployment of class as a crucial category of performative femininity, might indeed be a key site through which whiteness is denaturalized and its power challenged. Specifically, I will read on camp as a politicized mode of race, class and gender performance, focusing on the intersections of these categories of identity in the drag performance of Divine.

  9. Pipeline Drag Reducers

    Marawan, H.

    2004-01-01

    Pipeline drag reducers have proven to be an extremely powerful tool in fluid transportation. High molecular weight polymers are used to reduce the frictional pressure loss ratio in crude oil pipelines, refined fuel and aqueous pipelines. Chemical structure of the main used pipeline drag reducers is one of the following polymers and copolymers classified according to the type of fluid to ; low density polyethylene, copolymer of I-hexane cross linked with divinyl benzene, polyacrylamide, polyalkylene oxide polymers and their copolymers, fluorocarbons, polyalkyl methacrylates and terpolymer of styrene, alkyl acrylate and acrylic acid. Drag reduction is the increase in pump ability of a fluid caused by the addition of small amounts of an additive to the fluid. The effectiveness of a drag reducer is normally expressed in terms of percent drag reduction. Frictional pressure loss in a pipeline system is a waste of energy and it costly. The drag reducing additive minimizes the flow turbulence, increases throughput and reduces the energy costs. The Flow can be increased by more than 80 % with existing assets. The effectiveness of the injected drag reducer in Mostorod to Tanta crude oil pipeline achieved 35.4 % drag reduction and 23.2 % flow increase of the actual performance The experimental application of DRA on Arab Petroleum Pipeline Company (Summed) achieved a flow increase ranging from 9-32 %

  10. Safe-life and damage-tolerant design approaches for helicopter structures

    Reddick, H. K., Jr.

    1983-01-01

    The safe-life and damage-tolerant design approaches discussed apply to both metallic and fibrous composite helicopter structures. The application of these design approaches to fibrous composite structures is emphasized. Safe-life and damage-tolerant criteria are applied to all helicopter flight critical components, which are generally categorized as: dynamic components with a main and tail rotor system, which includes blades, hub and rotating controls, and drive train which includes transmission, and main and interconnecting rotor shafts; and the airframe, composed of the fuselage, aerodynamic surfaces, and landing gear.

  11. Combat Rescue Helicopter (CRH)

    2015-12-01

    Selected Acquisition Report (SAR) RCS: DD-A&T(Q&A)823-479 Combat Rescue Helicopter (CRH) As of FY 2017 President’s Budget Defense Acquisition...Name Combat Rescue Helicopter (CRH) DoD Component Air Force Responsible Office References SAR Baseline (Development Estimate) Defense Acquisition... Helicopter (CRH) system will provide Personnel Recovery (PR) forces with a vertical takeoff and landing aircraft that is quickly deployable and

  12. Numerical investigation of turbulent flow past a four-bladed helicopter rotor using k - ω SST model

    Xu, H.; Khalid, M.

    2002-01-01

    In a previous study of the laminar flow over a four-bladed helicopter rotor, abnormal Cp distributions were observed on the upper surfaces of the blades. To address this problem, the aerodynamic performance of the same rotor is investigated using the k - ω SST turbulence model, as contained in the WIND code. The rotor is configured as a Chimera moving grid in a quasi-steady flow field. The rotor rotation schedule and the blade twisting are implemented as specified in the wind tunnel testing of a RoBin generic helicopter. More realistic Cp distributions on the blade surfaces are thus obtained. The aerodynamic load distributions in the radial direction of the rotor plane are generated by integrating the pressure on each blade surfaces along the blade chordwise direction. The analyses of these load distributions in the azmuthal direction provide a critical insight into the rotor model, which is based on the actuator-disc assumption. Also, some preliminary results for the flow past a full helicopter configuration, including the rotor and the RoBin fuselage, are presented. The current paper demonstrates the Chimera grid topologies and the Chimera grid generation technique for both blade and fuselage configuration. This would provide a powerful tool to simulate flow past an entire helicopter and to study the rotor-fuselage flow interaction. (author)

  13. Air Layer Drag Reduction

    Ceccio, Steven; Elbing, Brian; Winkel, Eric; Dowling, David; Perlin, Marc

    2008-11-01

    A set of experiments have been conducted at the US Navy's Large Cavitation Channel to investigate skin-friction drag reduction with the injection of air into a high Reynolds number turbulent boundary layer. Testing was performed on a 12.9 m long flat-plate test model with the surface hydraulically smooth and fully rough at downstream-distance-based Reynolds numbers to 220 million and at speeds to 20 m/s. Local skin-friction, near-wall bulk void fraction, and near-wall bubble imaging were monitored along the length of the model. The instrument suite was used to access the requirements necessary to achieve air layer drag reduction (ALDR). Injection of air over a wide range of air fluxes showed that three drag reduction regimes exist when injecting air; (1) bubble drag reduction that has poor downstream persistence, (2) a transitional regime with a steep rise in drag reduction, and (3) ALDR regime where the drag reduction plateaus at 90% ± 10% over the entire model length with large void fractions in the near-wall region. These investigations revealed several requirements for ALDR including; sufficient volumetric air fluxes that increase approximately with the square of the free-stream speed, slightly higher air fluxes are needed when the surface tension is reduced, higher air fluxes are required for rough surfaces, and the formation of ALDR is sensitive to the inlet condition.

  14. 77 FR 63260 - Airworthiness Directives; Robinson Helicopter Company Helicopters

    2012-10-16

    ... Helicopter Company Helicopters AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of proposed rulemaking (NPRM). SUMMARY: We propose to adopt a new airworthiness directive (AD) for Robinson Helicopter Company (Robinson) Model R44 and R44 II helicopters equipped with emergency floats, which would require...

  15. 77 FR 12991 - Airworthiness Directives; Robinson Helicopter Company Helicopters

    2012-03-05

    ... Airworthiness Directives; Robinson Helicopter Company Helicopters AGENCY: Federal Aviation Administration (FAA...) that was published in the Federal Register. That AD applies to Robinson Helicopter Company (Robinson) Model R22, R22 Alpha, R22 Beta, R22 Mariner, R44, and R44 II helicopters. The paragraph reference in...

  16. 77 FR 68055 - Airworthiness Directives; Bell Helicopter Textron Helicopters

    2012-11-15

    ... Airworthiness Directives; Bell Helicopter Textron Helicopters AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Final rule. SUMMARY: We are adopting a new airworthiness directive (AD) for Bell Helicopter Textron (BHT) Model 412, 412EP, and 412CF helicopters. This AD requires a repetitive inspection of the...

  17. Aerodynamic Drag Scoping Work.

    Voskuilen, Tyler [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Erickson, Lindsay Crowl [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Knaus, Robert C. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2018-02-01

    This memo summarizes the aerodynamic drag scoping work done for Goodyear in early FY18. The work is to evaluate the feasibility of using Sierra/Low-Mach (Fuego) for drag predictions of rolling tires, particularly focused on the effects of tire features such as lettering, sidewall geometry, rim geometry, and interaction with the vehicle body. The work is broken into two parts. Part 1 consisted of investigation of a canonical validation problem (turbulent flow over a cylinder) using existing tools with different meshes and turbulence models. Part 2 involved calculating drag differences over plate geometries with simple features (ridges and grooves) defined by Goodyear of approximately the size of interest for a tire. The results of part 1 show the level of noise to be expected in a drag calculation and highlight the sensitivity of absolute predictions to model parameters such as mesh size and turbulence model. There is 20-30% noise in the experimental measurements on the canonical cylinder problem, and a similar level of variation between different meshes and turbulence models. Part 2 shows that there is a notable difference in the predicted drag on the sample plate geometries, however, the computational cost of extending the LES model to a full tire would be significant. This cost could be reduced by implementation of more sophisticated wall and turbulence models (e.g. detached eddy simulations - DES) and by focusing the mesh refinement on feature subsets with the goal of comparing configurations rather than absolute predictivity for the whole tire.

  18. Magnon-drag thermopile.

    Costache, Marius V; Bridoux, German; Neumann, Ingmar; Valenzuela, Sergio O

    2011-12-18

    Thermoelectric effects in spintronics are gathering increasing attention as a means of managing heat in nanoscale structures and of controlling spin information by using heat flow. Thermal magnons (spin-wave quanta) are expected to play a major role; however, little is known about the underlying physical mechanisms involved. The reason is the lack of information about magnon interactions and of reliable methods to obtain it, in particular for electrical conductors because of the intricate influence of electrons. Here, we demonstrate a conceptually new device that enables us to gather information on magnon-electron scattering and magnon-drag effects. The device resembles a thermopile formed by a large number of pairs of ferromagnetic wires placed between a hot and a cold source and connected thermally in parallel and electrically in series. By controlling the relative orientation of the magnetization in pairs of wires, the magnon drag can be studied independently of the electron and phonon-drag thermoelectric effects. Measurements as a function of temperature reveal the effect on magnon drag following a variation of magnon and phonon populations. This information is crucial to understand the physics of electron-magnon interactions, magnon dynamics and thermal spin transport.

  19. Al-Li alloy 1441 for fuselage applications

    Bird, R.K.; Dicus, D.L. [National Aeronautics and Space Administration, Hampton, VA (United States). Langley Research Center; Fridlyander, J.N.; Sandler, V.S.

    2000-07-01

    A cooperative investigation was conducted to evaluate Al-Cu-Mg-Li alloy 1441 for long service life fuselage applications. Alloy 1441 is currently being used for fuselage applications on the Russian Be- 103 amphibious aircraft, and is expected to be used for fuselage skin on a new Tupolev business class aircraft. Alloy 1441 is cold-rollable and has several attributes that make it attractive for fuselage skin applications. These attributes include lower density and higher specific modulus with similar strength as compared to conventional Al-Cu-Mg alloys. Cold-rolled 1441 Al-Li sheet specimens were tested at NASA Langley research center (LaRC) and at the All-Russia Institute of Aviation Materials (VIAM) in Russia to evaluate tensile properties, fracture toughness, impact resistance, fatigue life and fatigue crack growth rate. In addition, fuselage panels were fabricated by Tupolev Design Bureau (TDB) using 1441 skins and Al-Zn-Mg-Cu alloy stiffeners. The panels were subjected to cyclic pressurization fatigue tests at TDB and at LaRC to simulate fuselage pressurization/depressurization during aircraft service. This paper discusses the results from this investigation. (orig.)

  20. Dragging of inertial frames.

    Ciufolini, Ignazio

    2007-09-06

    The origin of inertia has intrigued scientists and philosophers for centuries. Inertial frames of reference permeate our daily life. The inertial and centrifugal forces, such as the pull and push that we feel when our vehicle accelerates, brakes and turns, arise because of changes in velocity relative to uniformly moving inertial frames. A classical interpretation ascribed these forces to acceleration relative to some absolute frame independent of the cosmological matter, whereas an opposite view related them to acceleration relative to all the masses and 'fixed stars' in the Universe. An echo and partial realization of the latter idea can be found in Einstein's general theory of relativity, which predicts that a spinning mass will 'drag' inertial frames along with it. Here I review the recent measurements of frame dragging using satellites orbiting Earth.

  1. An Analysis of CFD and Flat Plate Predictions of Friction Drag for the TCA W/B at Supersonic Cruise

    Lawrence, Scott L.

    1999-01-01

    This paper presents results of a study which attempted to provide some understanding of the relationship between skin friction drag estimates produced by flat plate methods and those produced by Navier-Stokes computations. A brief introduction is followed by analysis, including a flat plate grid study, analysis of the wing flow, an analysis of the fuselage flow. Other results of interest are then presented, including turbulence model sensitivities, and brief analysis of other configurations.

  2. 77 FR 30232 - Airworthiness Directives; Bell Helicopter Textron Helicopters

    2012-05-22

    ...-0530; Directorate Identifier 2011-SW-075-AD] RIN 2120-AA64 Airworthiness Directives; Bell Helicopter Textron Helicopters AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of proposed rulemaking (NPRM). SUMMARY: We propose to adopt a new airworthiness directive (AD) for Bell Helicopter...

  3. Fluid Mechanics, Drag Reduction and Advanced Configuration Aeronautics

    Bushnell, Dennis M.

    2000-01-01

    This paper discusses Advanced Aircraft configurational approaches across the speed range, which are either enabled, or greatly enhanced, by clever Flow Control. Configurations considered include Channel Wings with circulation control for VTOL (but non-hovering) operation with high cruise speed, strut-braced CTOL transports with wingtip engines and extensive ('natural') laminar flow control, a midwing double fuselage CTOL approach utilizing several synergistic methods for drag-due-to-lift reduction, a supersonic strut-braced configuration with order of twice the L/D of current approaches and a very advanced, highly engine flow-path-integrated hypersonic cruise machine. This paper indicates both the promise of synergistic flow control approaches as enablers for 'Revolutions' in aircraft performance and fluid mechanic 'areas of ignorance' which impede their realization and provide 'target-rich' opportunities for Fluids Research.

  4. 77 FR 52264 - Airworthiness Directives; Hughes Helicopters, Inc., and McDonnell Douglas Helicopter Systems...

    2012-08-29

    ... Airworthiness Directives; Hughes Helicopters, Inc., and McDonnell Douglas Helicopter Systems (Type Certificate... Airworthiness Directive (AD): Hughes Helicopters Inc., and McDonnel Douglas Helicopter Systems (Type Certificate...

  5. 78 FR 18226 - Airworthiness Directives; Hughes Helicopters, Inc., and McDonnell Douglas Helicopter Systems...

    2013-03-26

    ... Airworthiness Directives; Hughes Helicopters, Inc., and McDonnell Douglas Helicopter Systems (Type Certificate... directive (AD): 2013-05-16 Hughes Helicopters, Inc., and McDonnell Douglas Helicopter Systems (Type...

  6. Composite Structure Modeling and Analysis of Advanced Aircraft Fuselage Concepts

    Mukhopadhyay, Vivek; Sorokach, Michael R.

    2015-01-01

    NASA Environmentally Responsible Aviation (ERA) project and the Boeing Company are collabrating to advance the unitized damage arresting composite airframe technology with application to the Hybrid-Wing-Body (HWB) aircraft. The testing of a HWB fuselage section with Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) construction is presently being conducted at NASA Langley. Based on lessons learned from previous HWB structural design studies, improved finite-element models (FEM) of the HWB multi-bay and bulkhead assembly are developed to evaluate the performance of the PRSEUS construction. In order to assess the comparative weight reduction benefits of the PRSEUS technology, conventional cylindrical skin-stringer-frame models of a cylindrical and a double-bubble section fuselage concepts are developed. Stress analysis with design cabin-pressure load and scenario based case studies are conducted for design improvement in each case. Alternate analysis with stitched composite hat-stringers and C-frames are also presented, in addition to the foam-core sandwich frame and pultruded rod-stringer construction. The FEM structural stress, strain and weights are computed and compared for relative weight/strength benefit assessment. The structural analysis and specific weight comparison of these stitched composite advanced aircraft fuselage concepts demonstrated that the pressurized HWB fuselage section assembly can be structurally as efficient as the conventional cylindrical fuselage section with composite stringer-frame and PRSEUS construction, and significantly better than the conventional aluminum construction and the double-bubble section concept.

  7. Riveted Lap Joints in Aircraft Fuselage Design, Analysis and Properties

    Skorupa, Andrzej

    2012-01-01

    Fatigue of the pressurized fuselages of transport aircraft is a significant problem all builders and users of aircraft have to cope with for reasons associated with assuring a sufficient lifetime and safety, and formulating adequate inspection procedures. These aspects are all addressed in various formal protocols for creating and maintaining airworthiness, including damage tolerance considerations. In most transport aircraft, fatigue occurs in lap joints, sometimes leading to circumstances that threaten safety in critical ways. The problem of fatigue of lap joints has been considerably enlarged by the goal of extending aircraft lifetimes. Fatigue of riveted lap joints between aluminium alloy sheets, typical of the pressurized aircraft fuselage, is the major topic of the present book. The richly illustrated and well-structured chapters treat subjects such as: structural design solutions and loading conditions for fuselage skin joints; relevance of laboratory test results for simple lap joint specimens to rive...

  8. Drag Reduction Devices for Aircraft (Latest Citations from the Aerospace Database)

    1996-01-01

    The bibliography contains citations concerning the modeling, application, testing, and development of drag reduction devices for aircraft. Slots, flaps, fences, large-eddy breakup (LEBU) devices, vortex generators and turbines, Helmholtz resonators, and winglets are among the devices discussed. Contour shaping to ensure laminar flow, control boundary layer transition, or minimize turbulence is also covered. Applications include the wings, nacelles, fuselage, empennage, and externals of aircraft designed for high-lift, subsonic, or supersonic operation. The design, testing, and development of directional grooves, commonly called riblets, are covered in a separate bibliography.(Contains 50-250 citations and includes a subject term index and title list.)

  9. Experimental Investigation of a Helicopter Rotor Hub Flow

    Reich, David

    The rotor hub system is by far the largest contributor to helicopter parasite drag and a barrier to increasing helicopter forward-flight speed and range. Additionally, the hub sheds undesirable vibration- and instability-inducing unsteady flow over the empennage. The challenges associated with rotor hub flows are discussed, including bluff body drag, interactional aerodynamics, and the effect of the turbulent hub wake on the helicopter empennage. This study was conducted in three phases to quantify model-scale rotor hub flows in water tunnels at The Pennsylvania State University Applied research lab. The first phase investigated scaling and component interaction effects on a 1:17 scale rotor hub model in the 12-inch diameter water tunnel. Effects of Reynolds number, advance ratio, and hub geometry configuration on the drag and wake shed from the rotor hub were quantified using load cell measurements and particle-image velocimetry (PIV). The second phase focused on flow visualization and measurement on a rotor hub and rotor hub/pylon geometry in the 12-inch diameter water tunnel. Stereo PIV was conducted in a cross plane downstream of the hub and flow visualization was conducted using oil paint and fluorescent dye. The third phase concentrated on high accuracy load measurement and prediction up to full-scale Reynolds number on a 1:4.25 scale model in the 48-inch diameter water tunnel. Measurements include 6 degree of freedom loads on the hub and two-component laser-Doppler velocimetry in the wake. Finally, results and conclusions are discussed, followed by recommendations for future investigations.

  10. LAYOUT of the PASSENGER twin-fuselage AIRPLANE FOR LOCAL LINES

    V. G. Gusev

    2015-01-01

    Full Text Available The article shows the peculiarities and disadvantages of the classical single-fuselage configuration aircraft for local lines. It also provides an overview of the twin-fuselage configuration aircraft. A version of the twin-fuselage passenger aircraft is offered and the ground of its advantages is given.

  11. Advanced Airfoils Boost Helicopter Performance

    2007-01-01

    Carson Helicopters Inc. licensed the Langley RC4 series of airfoils in 1993 to develop a replacement main rotor blade for their Sikorsky S-61 helicopters. The company's fleet of S-61 helicopters has been rebuilt to include Langley's patented airfoil design, and the helicopters are now able to carry heavier loads and fly faster and farther, and the main rotor blades have twice the previous service life. In aerial firefighting, the performance-boosting airfoils have helped the U.S. Department of Agriculture's Forest Service control the spread of wildfires. In 2003, Carson Helicopters signed a contract with Ducommun AeroStructures Inc., to manufacture the composite blades for Carson Helicopters to sell

  12. Parametric fuselage design : Integration of mechanics and acoustic & thermal insulation

    Krakers, L.A.

    2009-01-01

    Designing a fuselage is a very complex process, which involves many different aspects like strength and stability, fatigue, damage tolerance, fire resistance, thermal and acoustic insulation but also inspection, maintenance, production and repair aspects. It is difficult to include all design

  13. Aerodynamic drag on intermodal railcars

    Kinghorn, Philip; Maynes, Daniel

    2014-11-01

    The aerodynamic drag associated with transport of commodities by rail is becoming increasingly important as the cost of diesel fuel increases. This study aims to increase the efficiency of intermodal cargo trains by reducing the aerodynamic drag on the load carrying cars. For intermodal railcars a significant amount of aerodynamic drag is a result of the large distance between loads that often occurs and the resulting pressure drag resulting from the separated flow. In the present study aerodynamic drag data have been obtained through wind tunnel testing on 1/29 scale models to understand the savings that may be realized by judicious modification to the size of the intermodal containers. The experiments were performed in the BYU low speed wind tunnel and the test track utilizes two leading locomotives followed by a set of five articulated well cars with double stacked containers. The drag on a representative mid-train car is measured using an isolated load cell balance and the wind tunnel speed is varied from 20 to 100 mph. We characterize the effect that the gap distance between the containers and the container size has on the aerodynamic drag of this representative rail car and investigate methods to reduce the gap distance.

  14. 78 FR 1730 - Airworthiness Directives; Bell Helicopter Textron Inc. Helicopters

    2013-01-09

    ... Helicopter Textron Inc. (BHTI) Model 205A, 205A-1, and 205B helicopters with certain starter/generator power... that may lead to a fire in the starter/generator, smoke in the cockpit that reduces visibility, and... Office, M-30, West Building Ground Floor, Room W12- 140, 1200 New Jersey Avenue SE., Washington, DC 20590...

  15. 77 FR 729 - Airworthiness Directives; Enstrom Helicopter Corporation Helicopters

    2012-01-06

    ... to the specified helicopters with a reversible trim motor, P/N 28-16621 (Ford Motor Company C1AZ... helicopters with a reversible trim motor, P/N 28-16621 (Ford Motor Company C1AZ- 14553A) or P/N AD1R-10...

  16. Thermal lift generation and drag reduction in rarefied aerodynamics

    Pekardan, Cem; Alexeenko, Alina

    2016-11-01

    With the advent of the new technologies in low pressure environments such as Hyperloop and helicopters designed for Martian applications, understanding the aerodynamic behavior of airfoils in rarefied environments are becoming more crucial. In this paper, verification of rarefied ES-BGK solver and ideas such as prediction of the thermally induced lift and drag reduction in rarefied aerodynamics are investigated. Validation of the rarefied ES-BGK solver with Runge-Kutta discontinous Galerkin method with experiments in transonic regime with a Reynolds number of 73 showed that ES-BGK solver is the most suitable solver in near slip transonic regime. For the quantification of lift generation, A NACA 0012 airfoil is studied with a high temperature surface on the bottom for the lift creation for different Knudsen numbers. It was seen that for lower velocities, continuum solver under predicts the lift generation when the Knudsen number is 0.00129 due to local velocity gradients reaching slip regime although lift coefficient is higher with the Boltzmann ES-BGK solutions. In the second part, the feasibility of using thermal transpiration for drag reduction is studied. Initial study in drag reduction includes an application of a thermal gradient at the upper surface of a NACA 0012 airfoil near trailing edge at a 12-degree angle of attack and 5 Pa pressure. It was seen that drag is reduced by 4 percent and vortex shedding frequency is reduced due to asymmetry introduced in the flow due to temperature gradient causing reverse flow due to thermal transpiration phenomena.

  17. Semi-active control of helicopter vibration using controllable stiffness and damping devices

    Anusonti-Inthra, Phuriwat

    Semi-active concepts for helicopter vibration reduction are developed and evaluated in this dissertation. Semi-active devices, controllable stiffness devices or controllable orifice dampers, are introduced; (i) in the blade root region (rotor-based concept) and (ii) between the rotor and the fuselage as semi-active isolators (in the non-rotating frame). Corresponding semi-active controllers for helicopter vibration reduction are also developed. The effectiveness of the rotor-based semi-active vibration reduction concept (using stiffness and damping variation) is demonstrated for a 4-bladed hingeless rotor helicopter in moderate- to high-speed forward flight. A sensitivity study shows that the stiffness variation of root element can reduce hub vibrations when proper amplitude and phase are used. Furthermore, the optimal semi-active control scheme can determine the combination of stiffness variations that produce significant vibration reduction in all components of vibratory hub loads simultaneously. It is demonstrated that desired cyclic variations in properties of the blade root region can be practically achieved using discrete controllable stiffness devices and controllable dampers, especially in the flap and lag directions. These discrete controllable devices can produce 35--50% reduction in a composite vibration index representing all components of vibratory hub loads. No detrimental increases are observed in the lower harmonics of blade loads and blade response (which contribute to the dynamic stresses) and controllable device internal loads, when the optimal stiffness and damping variations are introduced. The effectiveness of optimal stiffness and damping variations in reducing hub vibration is retained over a range of cruise speeds and for variations in fundamental rotor properties. The effectiveness of the semi-active isolator is demonstrated for a simplified single degree of freedom system representing the semi-active isolation system. The rotor

  18. A Comparison of Computed and Experimental Flowfields of the RAH-66 Helicopter

    vanDam, C. P.; Budge, A. M.; Duque, E. P. N.

    1996-01-01

    This paper compares and evaluates numerical and experimental flowfields of the RAH-66 Comanche helicopter. The numerical predictions were obtained by solving the Thin-Layer Navier-Stokes equations. The computations use actuator disks to investigate the main and tail rotor effects upon the fuselage flowfield. The wind tunnel experiment was performed in the 14 x 22 foot facility located at NASA Langley. A suite of flow conditions, rotor thrusts and fuselage-rotor-tail configurations were tested. In addition, the tunnel model and the computational geometry were based upon the same CAD definition. Computations were performed for an isolated fuselage configuration and for a rotor on configuration. Comparisons between the measured and computed surface pressures show areas of correlation and some discrepancies. Local areas of poor computational grid-quality and local areas of geometry differences account for the differences. These calculations demonstrate the use of advanced computational fluid dynamic methodologies towards a flight vehicle currently under development. It serves as an important verification for future computed results.

  19. 46 CFR 108.653 - Helicopter facilities.

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Helicopter facilities. 108.653 Section 108.653 Shipping... EQUIPMENT Equipment Markings and Instructions § 108.653 Helicopter facilities. (a) Each helicopter fueling facility must be marked adjacent to the fueling hose storage: “WARNING—HELICOPTER FUELING STATION—KEEP...

  20. 46 CFR 108.486 - Helicopter decks.

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Helicopter decks. 108.486 Section 108.486 Shipping COAST... Fire Extinguishing Systems Fire Protection for Helicopter Facilities § 108.486 Helicopter decks. At least two of the accesses to the helicopter landing deck must each have a fire hydrant on the unit's...

  1. Damage Tolerant Repair Techniques for Pressurized Aircraft Fuselages

    1994-01-01

    RepoW Techniques for Prwurized Aircraft AXWdOg 4.9 Summary and Conclusions The basics of adhesive bonded repairs for aluminum aircraft fuselages have... of cruise altitude and bending stresses in the plate at the tip of one-sided reinforcements (chapter 5). The expanded Rose model was transformed into a...DEPARTMEN1 OF THE AIR FORCE AGENCY REPORT NUMBER AFIT/CI 2950 P STREET WRIGHT-PATTERSON AFB OH 45433-7765 11. SUPPLEMENTARY NOTES Usa. DISTRUISUIOII

  2. Cabin fuselage structural design with engine installation and control system

    Balakrishnan, Tanapaal; Bishop, Mike; Gumus, Ilker; Gussy, Joel; Triggs, Mike

    1994-01-01

    Design requirements for the cabin, cabin system, flight controls, engine installation, and wing-fuselage interface that provide adequate interior volume for occupant seating, cabin ingress and egress, and safety are presented. The fuselage structure must be sufficient to meet the loadings specified in the appropriate sections of Federal Aviation Regulation Part 23. The critical structure must provide a safe life of 10(exp 6) load cycles and 10,000 operational mission cycles. The cabin seating and controls must provide adjustment to account for various pilot physiques and to aid in maintenance and operation of the aircraft. Seats and doors shall not bind or lockup under normal operation. Cabin systems such as heating and ventilation, electrical, lighting, intercom, and avionics must be included in the design. The control system will consist of ailerons, elevator, and rudders. The system must provide required deflections with a combination of push rods, bell cranks, pulleys, and linkages. The system will be free from slack and provide smooth operation without binding. Environmental considerations include variations in temperature and atmospheric pressure, protection against sand, dust, rain, humidity, ice, snow, salt/fog atmosphere, wind and gusts, and shock and vibration. The following design goals were set to meet the requirements of the statement of work: safety, performance, manufacturing and cost. To prevent the engine from penetrating the passenger area in the event of a crash was the primary safety concern. Weight and the fuselage aerodynamics were the primary performance concerns. Commonality and ease of manufacturing were major considerations to reduce cost.

  3. World helicopter market study

    Cleary, B.; Pearson, R. W.; Greenwood, S. W.; Kaplan, L.

    1978-01-01

    The extent of the threat to the US helicopter industry posed by a determined effort by foreign manufacturers, European companies in particular, to supply their own domestic markets and also to penetrate export markets, including the USA is assessed. Available data on US and world markets for civil and military uses are collated and presented in both graphic and tabular form showing the past history of production and markets and, where forecasts are available, anticipated future trends. The data are discussed on an item-by-item basis and inferences are drawn in as much depth as appears justified.

  4. Helicopter Icing Review.

    1980-09-01

    helicopter (i.e. in an icing tunnel or engine test cell ) and therefore can be subjected to controlled icing where spe- cific problems can be safely...evaluation. 69 2.2.5.2 Ice Protection Systems Demonstration Many of the systems noted in 2.2.5.1 can be evaluated in icing test cells or icing wind tunnels...Figure 2-32 illustrates a typical rotor deice system control arrangement. 104 (N >4 A.dO INaH -E- C4) uo U En 9 E-1 H m I ~z O 04 04iH U 0 El4 E-f C E

  5. Finite Element Analysis of Composite Aircraft Fuselage Frame

    Dandekar, Aditya Milind

    Composites have been introduced in aircraft industries, for their stronger, stiffer, and lighter properties than their metal-alloys counterparts. The general purpose of an aircraft is to transport commercial or military payload. Aircraft frames primarily maintains the shape of fuselage and prevent instability of the structure. Fuselage is similar as wing in construction which consist of longitudinal elements (longerons and stringers), transverse elements (frames and bulkheads) and its external skin. The fuselage is subjected to forces such as the wing reactions, landing gear reaction, empennage reaction, inertia forces subjected due to size and weight, internal pressure forces due to high altitude. Frames also ensure fail-safe design against skin crack propagation due to hoops stress. Ideal fuselage frames cross section is often circular ring shape with a frame cap of Z section. They are mainly made up of light alloy commonly used is aluminium alloys such as Al-2024, Al-7010, Al-7050, Al-7175. Aluminium alloys have good strength to density ratios in compression and bending of thin plate. A high strength to weight ratio of composite materials can result in a lighter aircraft structure or better safety factor. This research focuses on analysis of fuselage frame under dynamic load condition with change in material. Composites like carbon fibre reinforced plastics [CFRP] and glass fibre reinforced plastics [GFRP] are compared with traditional aluminium alloy Al-7075. The frame is subjected to impact test by dropping it at a velocity of 30 ft. / secs from a height of 86 inch from its centre of gravity. These parameters are considered in event of failure of landing gear, and an aircraft is subject to belly landing or gear-up landing. The shear flow is calculated due to impact force which acts in radial direction. The frame is analysed under static structural and explicit dynamic load conditions. Geometry is created in ANSYS Design Modeler. Analysis setup is created using

  6. Gravitational waves and dragging effects

    Bičák, Jiří; Katz, Joseph; Lynden-Bell, Donald

    2008-08-01

    Linear and rotational dragging effects of gravitational waves on local inertial frames are studied in purely vacuum spacetimes. First, the linear dragging caused by a simple cylindrical pulse is investigated. Surprisingly strong transverse effects of the pulse are exhibited. The angular momentum in cylindrically symmetric spacetimes is then defined and confronted with some results in the literature. In the main part, a general procedure is developed for studying weak gravitational waves with translational but not axial symmetry which can carry angular momentum. After a suitable averaging the rotation of local inertial frames due to such rotating waves can be calculated explicitly and illustrated graphically. This is done in detail in the accompanying paper. Finally, the rotational dragging is given for strong cylindrical waves interacting with a rotating cosmic string with a small angular momentum.

  7. Modeling, Control and Coordination of Helicopter Systems

    Ren, Beibei; Chen, Chang; Fua, Cheng-Heng; Lee, Tong Heng

    2012-01-01

    Modeling, Control and Coordination of Helicopter Systems provides a comprehensive treatment of helicopter systems, ranging from related nonlinear flight dynamic modeling and stability analysis to advanced control design for single helicopter systems, and also covers issues related to the coordination and formation control of multiple helicopter systems to achieve high performance tasks. Ensuring stability in helicopter flight is a challenging problem for nonlinear control design and development. This book is a valuable reference on modeling, control and coordination of helicopter systems,providing readers with practical solutions for the problems that still plague helicopter system design and implementation. Readers will gain a complete picture of helicopters at the systems level, as well as a better understanding of the technical intricacies involved. This book also: Presents a complete picture of modeling, control and coordination for helicopter systems Provides a modeling platform for a general class of ro...

  8. An Investigation of the Drag and Pressure Recovery of a Submerged Inlet and a Nose Inlet in the Transonic Flight Range with Free-fall Models

    Selna, James; Schlaff, Bernard A

    1951-01-01

    The drag and pressure recovery of an NACA submerged-inlet model and an NACA series I nose-inlet model were investigated in the transonic flight range. The tests were conducted over a mass-flow-ratio range of 0.4 to 0.8 and a Mach number range of about 0.8 to 1.10 employing large-scale recoverable free-fall models. The results indicate that the Mach number of drag divergence of the inlet models was about the same as that of a basic model without inlets. The external drag coefficients of the nose-inlet model were less than those of the submerged-inlet model throughout the test range. The difference in drag coefficient based on the maximum cross-sectional area of the models was about 0.02 at supersonic speeds and about 0.015 at subsonic speeds. For a hypothetical airplane with a ratio of maximum fuselage cross-sectional area to wing area of 0.06, the difference in airplane drag coefficient would be relatively small, about 0.0012 at supersonic speeds and about 0.0009 at subsonic speeds. Additional drag comparisons between the two inlet models are made considering inlet incremental and additive drag.

  9. Vertebral pain in helicopter pilots

    Auffret, R.; Delahaye, R. P.; Metges, P. J.; VICENS

    1980-01-01

    Pathological forms of spinal pain engendered by piloting helicopters were clinically studied. Lumbalgia and pathology of the dorsal and cervical spine are discussed along with their clinical and radiological signs and origins.

  10. Piezoelectric actuation of helicopter rotor blades

    Lieven, Nicholas A. J.

    2001-07-01

    The work presented in this paper is concerned with the application of embedded piezo-electric actuators in model helicopter rotor blades. The paper outlines techniques to define the optimal location of actuators to excite particular modes of vibration whilst the blade is rotating. Using composite blades the distribution of strain energy is defined using a Finite Element model with imposed rotor-dynamic and aerodynamics loads. The loads are specified through strip theory to determine the position of maximum bending moment and thus the optimal location of the embedded actuators. The effectiveness of the technique is demonstrated on a 1/4 scale fixed cyclic pitch rotor head. Measurement of the blade displacement is achieved by using strain gauges. In addition a redundant piezo-electric actuator is used to measure the blades' response characteristics. The addition of piezo-electric devices in this application has been shown to exhibit adverse aeroelastic effects, such as counter mass balancing and increased drag. Methods to minimise these effects are suggested. The outcome of the paper is a method for defining the location and orientation of piezo-electric devices in rotor-dynamic applications.

  11. Symmetry breaking for drag minimization

    Roper, Marcus; Squires, Todd M.; Brenner, Michael P.

    2005-11-01

    For locomotion at high Reynolds numbers drag minimization favors fore-aft asymmetric slender shapes with blunt noses and sharp trailing edges. On the other hand, in an inertialess fluid the drag experienced by a body is independent of whether it travels forward or backward through the fluid, so there is no advantage to having a single preferred swimming direction. In fact numerically determined minimum drag shapes are known to exhibit almost no fore-aft asymmetry even at moderate Re. We show that asymmetry persists, albeit extremely weakly, down to vanishingly small Re, scaling asymptotically as Re^3. The need to minimize drag to maximize speed for a given propulsive capacity gives one possible mechanism for the increasing asymmetry in the body plans seen in nature, as organisms increase in size and swimming speed from bacteria like E-Coli up to pursuit predator fish such as tuna. If it is the dominant mechanism, then this signature scaling will be observed in the shapes of motile micro-organisms.

  12. Helicopters for the future

    Ward, J. F.

    1984-01-01

    Technology needed to provide the basis for creating a widening rotary wing market include: well defined and proven design; reductions in noise, vibration, and fuel consumption; improvement of flying and ride quality; better safety; reliability; maintainability; and productivity. Unsteady transonic flow, yawed flow, dynamic stall, and blade vortex interaction are some of the problems faced by scientists and engineers in the helicopter industry with rotorcraft technology seen as an important development for future advanced high speed vehicle configurations. Such aircraft as the Boeing Vertol medium lift Model 360 composite aircraft, the Sikorsky Advancing Blade Concept (ABC) aircraft, the Bell Textron XV-15 Tilt Rotor Aircraft, and the X-wing rotor aircraft are discussed in detail. Even though rotorcraft technology has become an integral part of the military scene, the potential market for its civil applications has not been fully developed.

  13. Drag Reduction by Leidenfrost Vapor Layers

    Vakarelski, Ivan Uriev; Marston, Jeremy O.; Chan, Derek Y. C.; Thoroddsen, Sigurdur T

    2011-01-01

    , we show that such vapor layers can reduce the hydrodynamic drag by over 85%. These results appear to approach the ultimate limit of drag reduction possible by different methods based on gas-layer lubrication and can stimulate the development

  14. Helicopter fuel burn modeling in AEDT.

    2011-08-01

    This report documents work done to enhance helicopter fuel consumption modeling in the Federal Aviation : Administrations Aviation Environmental Design Tool (AEDT). Fuel consumption and flight performance data : were collected from helicopter flig...

  15. Quadrotor helicopter for surface hydrological measurements

    Pagano, C.; Tauro, F.; Porfiri, M.; Grimaldi, S.

    2013-12-01

    Surface hydrological measurements are typically performed through user-assisted and intrusive field methodologies which can be inadequate to monitor remote and extended areas. In this poster, we present the design and development of a quadrotor helicopter equipped with digital acquisition system and image calibration units for surface flow measurements. This custom-built aerial vehicle is engineered to be lightweight, low-cost, highly customizable, and stable to guarantee optimal image quality. Quadricopter stability guarantees minimal vibrations during image acquisition and, therefore, improved accuracy in flow velocity estimation through large scale particle image velocimetry algorithms or particle tracking procedures. Stability during the vehicle pitching and rolling is achieved by adopting large arm span and high-wing configurations. Further, the vehicle framework is composed of lightweight aluminum and durable carbon fiber for optimal resilience. The open source Ardupilot microcontroller is used for remote control of the quadricopter. The microcontroller includes an inertial measurement unit (IMU) equipped with accelerometers and gyroscopes for stable flight through feedback control. The vehicle is powered by a 3 cell (11.1V) 3000 mAh Lithium-polymer battery. Electronic equipment and wiring are hosted into the hollow arms and on several carbon fiber platforms in the waterproof fuselage. Four 35A high-torque motors are supported at the far end of each arm with 10 × 4.7 inch propellers. Energy dissipation during landing is accomplished by four pivoting legs that, through the use of shock absorbers, prevent the impact energy from affecting the frame thus causing significant damage. The data capturing system consists of a GoPro Hero3 camera and in-house built camera gimbal and shock absorber damping device. The camera gimbal, hosted below the vehicle fuselage, is engineered to maintain the orthogonality of the camera axis with respect to the water surface by

  16. Coulomb drag in the mesoscopic regime

    Mortensen, N.A.; Flensberg, Karsten; Jauho, Antti-Pekka

    2002-01-01

    We present a theory for Coulomb drag between two mesoscopic systems which expresses the drag in terms of scattering matrices and wave functions. The formalism can be applied to both ballistic and disordered systems and the consequences can be studied either by numerical simulations or analytic...... means such as perturbation theory or random matrix theory. The physics of Coulomb drag in the mesoscopic regime is very different from Coulomb drag between extended electron systems. In the mesoscopic regime we in general find fluctuations of the drag comparable to the mean value. Examples are vanishing...

  17. Investigating Flight with a Toy Helicopter

    Liebl, Michael

    2010-01-01

    Flight fascinates people of all ages. Recent advances in battery technology have extended the capabilities of model airplanes and toy helicopters. For those who have never outgrown a childhood enthusiasm for the wonders of flight, it is possible to buy inexpensive, remotely controlled planes and helicopters. A toy helicopter offers an opportunity…

  18. 46 CFR 109.577 - Helicopter fueling.

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Helicopter fueling. 109.577 Section 109.577 Shipping... Miscellaneous § 109.577 Helicopter fueling. (a) The master or person in charge shall designate persons to conduct helicopter fueling operations. (b) Portable tanks are handled and stowed in accordance with...

  19. Coulomb drag in coherent mesoscopic systems

    Mortensen, Asger; Flensberg, Karsten; Jauho, Antti-Pekka

    2001-01-01

    We present a theory for Coulomb drag between two mesoscopic systems. Our formalism expresses the drag in terms of scattering matrices and wave functions, and its range of validity covers both ballistic and disordered systems. The consequences can be worked out either by analytic means, such as th......We present a theory for Coulomb drag between two mesoscopic systems. Our formalism expresses the drag in terms of scattering matrices and wave functions, and its range of validity covers both ballistic and disordered systems. The consequences can be worked out either by analytic means......, such as the random matrix theory, or by numerical simulations. We show that Coulomb drag is sensitive to localized states. which usual transport measurements do not probe. For chaotic 2D systems we find a vanishing average drag, with a nonzero variance. Disordered 1D wires show a finite drag, with a large variance...

  20. Helicopter transport: help or hindrance?

    Plevin, Rebecca E; Evans, Heather L

    2011-12-01

    Traumatic injury continues to be a significant cause of morbidity and mortality in the year 2011. In addition, the healthcare expenditures and lost years of productivity represent significant economic cost to the affected individuals and their communities. Helicopters have been used to transport trauma patients for the past 40 years, but there are conflicting data on the benefits of helicopter emergency medical service (HEMS) in civilian trauma systems. Debate persists regarding the mortality benefit, cost-effectiveness, and safety of helicopter usage, largely because the studies to date vary widely in design and generalizability to trauma systems serving heterogeneous populations and geography. Strict criteria should be established to determine when HEMS transport is warranted and most likely to positively affect patient outcomes. Individual trauma systems should conduct an assessment of their resources and needs in order to most effectively incorporate helicopter transport into their triage model. Research suggests that HEMS improves mortality in certain subgroups of trauma patients, both after transport from the scene of injury and following interfacility transport. Studies examining the cost-effectiveness of HEMS had mixed results, but the majority found that it is a cost-effective tool. Safety remains an issue of contention with HEMS transport, as helicopters are associated with significant safety risk to the crew and patient. However, this risk may be justified provided there is a substantial mortality benefit to be gained. Recent studies suggest that strict criteria should be established to determine when helicopter transport is warranted and most likely to positively affect patient outcomes. Individual trauma systems should conduct an assessment of their resources and needs in order to most effectively incorporate HEMS into their triage model. This will enable regional hospitals to determine if the costs and safety risks associated with HEMS are worthwhile

  1. Fuselage panel noise attenuation by piezoelectric switching control

    Makihara, Kanjuro; Onoda, Junjiro; Minesugi, Kenji; Miyakawa, Takeya

    2010-01-01

    This paper describes a problem that we encountered in our noise attenuation project and our solution for it. We intend to attenuate low-frequency noise that transmits through aircraft fuselage panels. Our method of noise attenuation is implemented with a piezoelectric semi-active system having a selective switch instead of an active energy-supply system. The semi-active controller is based on the predicted sound pressure distribution obtained from acoustic emission analysis. Experiments and numerical simulations demonstrate that the semi-active method attenuates acoustic levels of not only the simple monochromatic noise but also of broadband noise. We reveal that tuning the electrical parameters in the circuit is the key to effective noise attenuation, to overcome the acoustic excitation problem due to sharp switching actions, as well as to control chattering problems. The results obtained from this investigation provide meaningful insights into designing noise attenuation systems for comfortable aircraft cabin environments

  2. 78 FR 9793 - Airworthiness Directives; Bell Helicopter Textron Helicopters

    2013-02-12

    ...-numbered main rotor hub inboard strap fittings (fittings). This AD requires magnetic particle inspecting... identified in this AD, contact Bell Helicopter Textron, Inc., P.O. Box 482, Fort Worth, TX 76101, telephone..., perform a magnetic particle inspection (MPI) of each fitting for a crack. If an MPI was already performed...

  3. Modelling and Analysis of Vibrations in a UAV Helicopter with a Vision System

    G. Nicolás Marichal Plasencia

    2012-11-01

    Full Text Available The analysis of the nature and damping of unwanted vibrations on Unmanned Aerial Vehicle (UAV helicopters are important tasks when images from on-board vision systems are to be obtained. In this article, the authors model a UAV system, generate a range of vibrations originating in the main rotor and design a control methodology in order to damp these vibrations. The UAV is modelled using VehicleSim, the vibrations that appear on the fuselage are analysed to study their effects on the on-board vision system by using Simmechanics software. Following this, the authors present a control method based on an Adaptive Neuro-Fuzzy Inference System (ANFIS to achieve satisfactory damping results over the vision system on board.

  4. Drag and drop display & builder

    Bolshakov, Timofei B.; Petrov, Andrey D.; /Fermilab

    2007-12-01

    The Drag and Drop (DnD) Display & Builder is a component-oriented system that allows users to create visual representations of data received from data acquisition systems. It is an upgrade of a Synoptic Display mechanism used at Fermilab since 2002. Components can be graphically arranged and logically interconnected in the web-startable Project Builder. Projects can be either lightweight AJAX- and SVG-based web pages, or they can be started as Java applications. The new version was initiated as a response to discussions between the LHC Controls Group and Fermilab.

  5. Short revolving wings enable hovering animals to avoid stall and reduce drag

    Lentink, David; Kruyt, Jan W.; Heijst, Gertjan F.; Altshuler, Douglas L.

    2014-11-01

    Long and slender wings reduce the drag of airplanes, helicopters, and gliding animals, which operate at low angle of attack (incidence). Remarkably, there is no evidence for such influence of wing aspect ratio on the energetics of hovering animals that operate their wings at much higher incidence. High incidence causes aircraft wings to stall, hovering animals avoid stall by generating an attached vortex along the leading edge of their wings that elevates lift. Hypotheses that explain this capability include the necessity for a short radial distance between the shoulder joint and wing tip, measured in chord lengths, instead of the long tip-to-tip distance that elevates aircraft performance. This stems from how hovering animals revolve their wings around a joint, a condition for which the precise effect of aspect ratio on stall performance is unknown. Here we show that the attachment of the leading edge vortex is determined by wing aspect ratio with respect to the center of rotation-for a suite of aspect ratios that represent both animal and aircraft wings. The vortex remains attached when the local radius is shorter than 4 chord lengths, and separates outboard on more slender wings. Like most other hovering animals, hummingbirds have wing aspect ratios between 3 and 4, much stubbier than helicopters. Our results show this makes their wings robust against flow separation, which reduces drag below values obtained with more slender wings. This revises our understanding of how aspect ratio improves performance at low Reynolds numbers.

  6. Development of pressure containment and damage tolerance technology for composite fuselage structures in large transport aircraft

    Smith, P. J.; Thomson, L. W.; Wilson, R. D.

    1986-01-01

    NASA sponsored composites research and development programs were set in place to develop the critical engineering technologies in large transport aircraft structures. This NASA-Boeing program focused on the critical issues of damage tolerance and pressure containment generic to the fuselage structure of large pressurized aircraft. Skin-stringer and honeycomb sandwich composite fuselage shell designs were evaluated to resolve these issues. Analyses were developed to model the structural response of the fuselage shell designs, and a development test program evaluated the selected design configurations to appropriate load conditions.

  7. Helicopter-Ship Qualification Testing

    Hoencamp, A.

    2015-01-01

    The goal of this research project is to develop a novel test methodology which can be used for optimizing cost and time efficiency of helicopter-ship qualification testing without reducing safety. For this purpose, the so-called “SHOL-X” test methodology has been established, which includes the

  8. Helicopter Toy and Lift Estimation

    Shakerin, Said

    2013-01-01

    A $1 plastic helicopter toy (called a Wacky Whirler) can be used to demonstrate lift. Students can make basic measurements of the toy, use reasonable assumptions and, with the lift formula, estimate the lift, and verify that it is sufficient to overcome the toy's weight. (Contains 1 figure.)

  9. Smart actuation for helicopter rotorblades

    Paternoster, Alexandre; Loendersloot, Richard; de Boer, Andries; Akkerman, Remko; Berselli, G.; Vertechy, R.; Vassura, G.

    2012-01-01

    Successful rotorcrafts were only achieved when the differences between hovering flight conditions and a stable forward flight were understood. During hovering, the air speed on all helicopter blades is linearly distributed along each blade and is the same for each. However, during forward flight,

  10. Helicopter detection and classification demonstrator

    Koersel, A.C. van

    2000-01-01

    A technology demonstrator that detects and classifies different helicopter types automatically, was developed at TNO-FEL. The demonstrator is based on a PC, which receives its acoustic input from an all-weather microphone. The demonstrator uses commercial off-the-shelf hardware to digitize the

  11. Coulomb drag in the mesoscopic regime

    Mortensen, N. Asger; Flensberg, Karsten; Jauho, Antti-Pekka

    2002-01-01

    We present a theory for Coulomb drug between two mesoscopic systems which expresses the drag in terms of scattering matrices and wave functions. The formalism can be applied to both ballistic and disordered systems and the consequences can be studied either by numerical simulations or analytic...... means such as perturbation theory or random matrix theory. The physics of Coulomb drag in the mesoscopic regime is very different from Coulomb drag between extended electron systems. In the mesoscopic regime we in general find fluctuations of the drag comparable to the mean value. Examples are vanishing...

  12. DOE Project on Heavy Vehicle Aerodynamic Drag

    McCallen, R; Salari, K; Ortega, J; Castellucci, P; Pointer, D; Browand, F; Ross, J; Storms, B

    2007-01-04

    Class 8 tractor-trailers consume 11-12% of the total US petroleum use. At highway speeds, 65% of the energy expenditure for a Class 8 truck is in overcoming aerodynamic drag. The project objective is to improve fuel economy of Class 8 tractor-trailers by providing guidance on methods of reducing drag by at least 25%. A 25% reduction in drag would present a 12% improvement in fuel economy at highway speeds, equivalent to about 130 midsize tanker ships per year. Specific goals include: (1) Provide guidance to industry in the reduction of aerodynamic drag of heavy truck vehicles; (2) Develop innovative drag reducing concepts that are operationally and economically sound; and (3) Establish a database of experimental, computational, and conceptual design information, and demonstrate the potential of new drag-reduction devices. The studies described herein provide a demonstration of the applicability of the experience developed in the analysis of the standard configuration of the Generic Conventional Model. The modeling practices and procedures developed in prior efforts have been applied directly to the assessment of new configurations including a variety of geometric modifications and add-on devices. Application to the low-drag 'GTS' configuration of the GCM has confirmed that the error in predicted drag coefficients increases as the relative contribution of the base drag resulting from the vehicle wake to the total drag increases and it is recommended that more advanced turbulence modeling strategies be applied under those circumstances. Application to a commercially-developed boat tail device has confirmed that this restriction does not apply to geometries where the relative contribution of the base drag to the total drag is reduced by modifying the geometry in that region. Application to a modified GCM geometry with an open grille and radiator has confirmed that the underbody flow, while important for underhood cooling, has little impact on the drag

  13. Improvements of evaporation drag model

    Li Xiaoyan; Yang Yanhua; Xu Jijun

    2004-01-01

    A special observable experiment facility has been established, and a series of experiments have been carried out on this facility by pouring one or several high-temperature particles into a water pool. The experiment has verified the evaporation drag model, which believe the non-symmetric profile of the local evaporation rate and the local density of the vapor would bring about a resultant force on the hot particle so as to resist its motion. However, in Yang's evaporation drag model, radiation heat transfer is taken as the only way to transfer heat from hot particle to the vapor-liquid interface and all of the radiation energy is deposited on the vapor-liquid interface, thus contributing to the vaporization rate and mass balance of the vapor film. So, the heat conduction and the heat convection are taken into account in improved model. At the same time, the improved model given by this paper presented calculations of the effect of hot particles temperature on the radiation absorption behavior of water

  14. Vorticity confinement technique for drag prediction

    Povitsky, Alex; Snyder, Troy

    2011-11-01

    This work couples wake-integral drag prediction and vorticity confinement technique (VC) for the improved prediction of drag from CFD simulations. Induced drag computations of a thin wing are shown to be more accurate than the more widespread method of surface pressure integration when compared to theoretical lifting-line value. Furthermore, the VC method improves trailing vortex preservation and counteracts the shift from induced drag to numerical entropy drag with increasing distance of Trefftz plane downstream of the wing. Accurate induced drag prediction via the surface integration of pressure barring a sufficiently refined surface grid and increased computation time. Furthermore, the alternative wake-integral technique for drag prediction suffers from numerical dissipation. VC is shown to control the numerical dissipation with very modest computational overhead. The 2-D research code is used to test specific formulations of the VC body force terms and illustrate the computational efficiency of the method compared to a ``brute force'' reduction in spatial step size. For the 3-D wing simulation, ANSYS FLUENT is employed with the VC body force terms added to the solver with user-defined functions (UDFs). VC is successfully implemented to highly unsteady flows typical for Micro Air Vehicles (MAV) producing oscillative drag force either by natural vortex shedding at high angles of attack or by flapping wing motion.

  15. A Study of the Utilization of Advanced Composites in Fuselage Structures of Commercial Aircraft

    Watts, D. J.; Sumida, P. T.; Bunin, B. L.; Janicki, G. S.; Walker, J. V.; Fox, B. R.

    1985-01-01

    A study was conducted to define the technology and data needed to support the introduction of advanced composites in the future production of fuselage structure in large transport aircraft. Fuselage structures of six candidate airplanes were evaluated for the baseline component. The MD-100 was selected on the basis of its representation of 1990s fuselage structure, an available data base, its impact on the schedule and cost of the development program, and its availability and suitability for flight service evaluation. Acceptance criteria were defined, technology issues were identified, and a composite fuselage technology development plan, including full-scale tests, was identified. The plan was based on composite materials to be available in the mid to late 1980s. Program resources required to develop composite fuselage technology are estimated at a rough order of magnitude to be 877 man-years exclusive of the bird strike and impact dynamic test components. A conceptual composite fuselage was designed, retaining the basic MD-100 structural arrangement for doors, windows, wing, wheel wells, cockpit enclosure, major bulkheads, etc., resulting in a 32 percent weight savings.

  16. Detailed design of a lattice composite fuselage structure by a mixed optimization method

    Liu, D.; Lohse-Busch, H.; Toropov, V.; Hühne, C.; Armani, U.

    2016-10-01

    In this article, a procedure for designing a lattice fuselage barrel is developed. It comprises three stages: first, topology optimization of an aircraft fuselage barrel is performed with respect to weight and structural performance to obtain the conceptual design. The interpretation of the optimal result is given to demonstrate the development of this new lattice airframe concept for the fuselage barrel. Subsequently, parametric optimization of the lattice aircraft fuselage barrel is carried out using genetic algorithms on metamodels generated with genetic programming from a 101-point optimal Latin hypercube design of experiments. The optimal design is achieved in terms of weight savings subject to stability, global stiffness and strain requirements, and then verified by the fine mesh finite element simulation of the lattice fuselage barrel. Finally, a practical design of the composite skin complying with the aircraft industry lay-up rules is presented. It is concluded that the mixed optimization method, combining topology optimization with the global metamodel-based approach, allows the problem to be solved with sufficient accuracy and provides the designers with a wealth of information on the structural behaviour of the novel anisogrid composite fuselage design.

  17. Determination of the surface drag coefficient

    Mahrt, L.; Vickers, D.; Sun, J.L.

    2001-01-01

    This study examines the dependence of the surface drag coefficient on stability, wind speed, mesoscale modulation of the turbulent flux and method of calculation of the drag coefficient. Data sets over grassland, sparse grass, heather and two forest sites are analyzed. For significantly unstable...... conditions, the drag coefficient does not depend systematically on z/L but decreases with wind speed for fixed intervals of z/L, where L is the Obukhov length. Even though the drag coefficient for weak wind conditions is sensitive to the exact method of calculation and choice of averaging time, the decrease...... of the drag coefficient with wind speed occurs for all of the calculation methods. A classification of flux calculation methods is constructed, which unifies the most common previous approaches. The roughness length corresponding to the usual Monin-Obukhov stability functions decreases with increasing wind...

  18. Fuselage mounted anti-collision lights utilizing high power LEDs

    Lundberg, John; Machi, Nicolo; Mangum, Scott; Singer, Jeffrey

    2005-09-01

    As LEDs continue to improve in efficacy and total light output, they are increasingly finding their way in to new applications in the aviation industry as well as adjacent markets. One function that is particularly challenging and may reap substantial benefits from this new technology is the fuselage mounted anti-collision light. Anti-collision lights provide conspicuity for the aircraft by periodically emitting bright flashes of light. The color, light distribution and intensity levels for these lights are all closely regulated through Federal Aviation Regulation (FAR) documents. These lighting requirements, along with thermal, environmental and aerodynamic requirements, drive the overall design. In this paper, we will discuss the existing technologies used in anti-collision lights and the advantages and challenges associated with an LED solution. Particular attention will be given to the optical, thermal, electrical and aerodynamic aspects associated with an LED approach. A specific case study will be presented along with some of the challenges that have arisen during the design process. These challenges include the addition of an integrated covert anti-collision lighting.

  19. A Helicopter submarine Search Game

    1988-09-01

    Figure 3. Graphical representation of Baston and Bostock ................. 10 Figure 4. Dips and Speed Circle...dimen.ional helicopter submarine gaines studied by Meinardi [Ref. 7] and more recently by Baston and Bostock [Ref. 8]. Meinardi solves a discr,-te form of...the game while Baston and Bostock solve the continuous case. Bes.ides Danskin’s game, not much work has been done on the two dimensional case except

  20. Drag Coefficient Estimation in Orbit Determination

    McLaughlin, Craig A.; Manee, Steve; Lichtenberg, Travis

    2011-07-01

    Drag modeling is the greatest uncertainty in the dynamics of low Earth satellite orbits where ballistic coefficient and density errors dominate drag errors. This paper examines fitted drag coefficients found as part of a precision orbit determination process for Stella, Starlette, and the GEOSAT Follow-On satellites from 2000 to 2005. The drag coefficients for the spherical Stella and Starlette satellites are assumed to be highly correlated with density model error. The results using MSIS-86, NRLMSISE-00, and NRLMSISE-00 with dynamic calibration of the atmosphere (DCA) density corrections are compared. The DCA corrections were formulated for altitudes of 200-600 km and are found to be inappropriate when applied at 800 km. The yearly mean fitted drag coefficients are calculated for each satellite for each year studied. The yearly mean drag coefficients are higher for Starlette than Stella, where Starlette is at a higher altitude. The yearly mean fitted drag coefficients for all three satellites decrease as solar activity decreases after solar maximum.

  1. Modelling of Aerodynamic Drag in Alpine Skiing

    Elfmark, Ola

    2017-01-01

    Most of the breaking force in the speed disciplines in alpine skiing is caused by the aerodynamic drag, and a better knowledge of the drag force is therefore desirable to gain time in races. In this study a complete database of how the drag area (CDA) changes, with respect to the different body segments, was made and used to explain a complete body motion in alpine skiing. Three experiments were performed in the wind tunnel at NTNU, Trondheim. The database from a full body measurement on an a...

  2. Drag and Torque on Locked Screw Propeller

    Tomasz Tabaczek

    2014-09-01

    Full Text Available Few data on drag and torque on locked propeller towed in water are available in literature. Those data refer to propellers of specific geometry (number of blades, blade area, pitch and skew of blades. The estimation of drag and torque of an arbitrary propeller considered in analysis of ship resistance or propulsion is laborious. The authors collected and reviewed test data available in the literature. Based on collected data there were developed the empirical formulae for estimation of hydrodynamic drag and torque acting on locked screw propeller. Supplementary CFD computations were carried out in order to prove the applicability of the formulae to modern moderately skewed screw propellers.

  3. Drag Reduction by Leidenfrost Vapor Layers

    Vakarelski, Ivan Uriev

    2011-05-23

    We demonstrate and quantify a highly effective drag reduction technique that exploits the Leidenfrost effect to create a continuous and robust lubricating vapor layer on the surface of a heated solid sphere moving in a liquid. Using high-speed video, we show that such vapor layers can reduce the hydrodynamic drag by over 85%. These results appear to approach the ultimate limit of drag reduction possible by different methods based on gas-layer lubrication and can stimulate the development of related energy saving technologies.

  4. Surveys of Students Challenge "Helicopter Parent" Stereotypes

    Hoover, Eric

    2008-01-01

    Stories of "helicopter parents" abound. But several longtime student-affairs officials agree that while helicopter parents are real, their numbers--and behaviors--have been exaggerated. Parental involvement on campus, they say, is usually more of a help than a headache, for students and colleges alike. Some officials believe colleges must do even…

  5. 29 CFR 1926.551 - Helicopters.

    2010-07-01

    ...) Loose gear and objects. Every practical precaution shall be taken to provide for the protection of the employees from flying objects in the rotor downwash. All loose gear within 100 feet of the place of lifting... manner in which loads are connected to the helicopter. If, for any reason, the helicopter operator...

  6. 46 CFR 108.487 - Helicopter deck fueling operations.

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Helicopter deck fueling operations. 108.487 Section 108... DESIGN AND EQUIPMENT Fire Extinguishing Systems Fire Protection for Helicopter Facilities § 108.487 Helicopter deck fueling operations. (a) Each helicopter landing deck on which fueling operations are...

  7. 46 CFR 108.489 - Helicopter fueling facilities.

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Helicopter fueling facilities. 108.489 Section 108.489... AND EQUIPMENT Fire Extinguishing Systems Fire Protection for Helicopter Facilities § 108.489 Helicopter fueling facilities. (a) Each helicopter fueling facility must have a fire protection system that...

  8. Helicopter Operations and Personnel Safety (Helirescue Manual). Fourth Edition.

    Dalle-Molle, John

    The illustrated manual includes information on various aspects of helicopter rescue missions, including mission management roles for key personnel, safety rules around helicopters, requests for helicopter support, sample military air support forms, selection of landing zones, helicopter evacuations, rescuer delivery, passenger unloading, crash…

  9. Weight Assessment for Fuselage Shielding on Aircraft With Open-Rotor Engines and Composite Blade Loss

    Carney, Kelly; Pereira, Michael; Kohlman, Lee; Goldberg, Robert; Envia, Edmane; Lawrence, Charles; Roberts, Gary; Emmerling, William

    2013-01-01

    The Federal Aviation Administration (FAA) has been engaged in discussions with airframe and engine manufacturers concerning regulations that would apply to new technology fuel efficient "openrotor" engines. Existing regulations for the engines and airframe did not envision features of these engines that include eliminating the fan blade containment systems and including two rows of counter-rotating blades. Damage to the airframe from a failed blade could potentially be catastrophic. Therefore the feasibility of using aircraft fuselage shielding was investigated. In order to establish the feasibility of this shielding, a study was conducted to provide an estimate for the fuselage shielding weight required to provide protection from an open-rotor blade loss. This estimate was generated using a two-step procedure. First, a trajectory analysis was performed to determine the blade orientation and velocity at the point of impact with the fuselage. The trajectory analysis also showed that a blade dispersion angle of 3deg bounded the probable dispersion pattern and so was used for the weight estimate. Next, a finite element impact analysis was performed to determine the required shielding thickness to prevent fuselage penetration. The impact analysis was conducted using an FAA-provided composite blade geometry. The fuselage geometry was based on a medium-sized passenger composite airframe. In the analysis, both the blade and fuselage were assumed to be constructed from a T700S/PR520 triaxially-braided composite architecture. Sufficient test data on T700S/PR520 is available to enable reliable analysis, and also demonstrate its good impact resistance properties. This system was also used in modeling the surrogate blade. The estimated additional weight required for fuselage shielding for a wing- mounted counterrotating open-rotor blade is 236 lb per aircraft. This estimate is based on the shielding material serving the dual use of shielding and fuselage structure. If the

  10. Microblowing Technique for Drag Reduction, Phase I

    National Aeronautics and Space Administration — NASA seeks to develop technologies for aircraft drag reduction which contribute to improved aerodynamic efficiency in support of national goals for reducing fuel...

  11. The physics of orographic gravity wave drag

    Miguel A C Teixeira

    2014-07-01

    Full Text Available The drag and momentum fluxes produced by gravity waves generated in flow over orography are reviewed, focusing on adiabatic conditions without phase transitions or radiation effects, and steady mean incoming flow. The orographic gravity wave drag is first introduced in its simplest possible form, for inviscid, linearized, non-rotating flow with the Boussinesq and hydrostatic approximations, and constant wind and static stability. Subsequently, the contributions made by previous authors (primarily using theory and numerical simulations to elucidate how the drag is affected by additional physical processes are surveyed. These include the effect of orography anisotropy, vertical wind shear, total and partial critical levels, vertical wave reflection and resonance, non-hydrostatic effects and trapped lee waves, rotation and nonlinearity. Frictional and boundary layer effects are also briefly mentioned. A better understanding of all of these aspects is important for guiding the improvement of drag parametrization schemes.

  12. Satellite Formation Control Using Atmospheric Drag

    Hajovsky, Blake B

    2007-01-01

    This study investigates the use of a linear quadratic terminal controller to reconfigure satellite formations using atmospheric drag actuated control while minimizing the loss of energy of the formation...

  13. Crashworthiness Analysis and Evaluation of Fuselage Section with Sub-floor Composite Sinusoidal Specimens

    H.L. Mou

    Full Text Available Abstract Crashworthiness is one of the main concerns in civil aviation safety particularly with regard to the increasing ratio of carbon fiber reinforced plastic (CFRP in aircraft primary structures. In order to generate dates for model validations, the mechanical properties of T700/3234 were obtained by material performance tests, and energy-absorbing results were gained by quasi-static crushing tests of composite sinusoidal specimens. The correctness of composite material model and single-layer finite element model of composite sinusoidal specimens were verified based on the simulation results and test results that were in good agreement. A typical civil aircraft fuselage section with composite sinusoidal specimens under cargo floor was suggested. The crashworthiness of finite element model of fuselage section was assessed by simulating the vertical drop test subjected to 7 m/s impact velocity, and the influences of different thickness of sub-floor composite sinusoidal specimens on crashworthiness of fuselage section were also analyzed. The simulation results show that the established finite element model can accurately simulate the crushing process of composite sinusoidal specimens; the failure process of fuselage section is more stable, and the safety of occupants can be effectively improved because of the smaller peak accelerations that was limited to human tolerance, a critical thickness of sub-floor composite sinusoidal specimens can restrict the magnitude of acceleration peaks, which has certain reference values for enhancing crashworthiness capabilities of fuselage section and improving the survivability of passengers.

  14. Active aerodynamic drag reduction on morphable cylinders

    Guttag, M.; Reis, P. M.

    2017-12-01

    We study a mechanism for active aerodynamic drag reduction on morphable grooved cylinders, whose topography can be modified pneumatically. Our design is inspired by the morphology of the Saguaro cactus (Carnegiea gigantea), which possesses an array of axial grooves, thought to help reduce aerodynamic drag, thereby enhancing the structural robustness of the plant under wind loading. Our analog experimental samples comprise a spoked rigid skeleton with axial cavities, covered by a stretched elastomeric film. Decreasing the inner pressure of the sample produces axial grooves, whose depth can be accurately varied, on demand. First, we characterize the relation between groove depth and pneumatic loading through a combination of precision mechanical experiments and finite element simulations. Second, wind tunnel tests are used to measure the aerodynamic drag coefficient (as a function of Reynolds number) of the grooved samples, with different levels of periodicity and groove depths. We focus specifically on the drag crisis and systematically measure the associated minimum drag coefficient and the critical Reynolds number at which it occurs. The results are in agreement with the classic literature of rough cylinders, albeit with an unprecedented level of precision and resolution in varying topography using a single sample. Finally, we leverage the morphable nature of our system to dynamically reduce drag for varying aerodynamic loading conditions. We demonstrate that actively controlling the groove depth yields a drag coefficient that decreases monotonically with Reynolds number and is significantly lower than the fixed sample counterparts. These findings open the possibility for the drag reduction of grooved cylinders to be operated over a wide range of flow conditions.

  15. Bioinspired surfaces for turbulent drag reduction.

    Golovin, Kevin B; Gose, James W; Perlin, Marc; Ceccio, Steven L; Tuteja, Anish

    2016-08-06

    In this review, we discuss how superhydrophobic surfaces (SHSs) can provide friction drag reduction in turbulent flow. Whereas biomimetic SHSs are known to reduce drag in laminar flow, turbulence adds many new challenges. We first provide an overview on designing SHSs, and how these surfaces can cause slip in the laminar regime. We then discuss recent studies evaluating drag on SHSs in turbulent flow, both computationally and experimentally. The effects of streamwise and spanwise slip for canonical, structured surfaces are well characterized by direct numerical simulations, and several experimental studies have validated these results. However, the complex and hierarchical textures of scalable SHSs that can be applied over large areas generate additional complications. Many studies on such surfaces have measured no drag reduction, or even a drag increase in turbulent flow. We discuss how surface wettability, roughness effects and some newly found scaling laws can help explain these varied results. Overall, we discuss how, to effectively reduce drag in turbulent flow, an SHS should have: preferentially streamwise-aligned features to enhance favourable slip, a capillary resistance of the order of megapascals, and a roughness no larger than 0.5, when non-dimensionalized by the viscous length scale.This article is part of the themed issue 'Bioinspired hierarchically structured surfaces for green science'. © 2016 The Author(s).

  16. Measurement of drag and its cancellation

    DeBra, D B; Conklin, J W, E-mail: johnwc@stanford.edu [Department of Aeronautics and Astronautics, Stanford University, Stanford, CA 94305-4035 (United States)

    2011-05-07

    The design of drag cancellation missions of the future will take advantage of the technology experience of the past. The importance of data for modeling of the atmosphere led to at least six types of measurement: (a) balloon flights, (b) missile-launched falling spheres, (c) the 'cannonball' satellites of Ken Champion with accelerometers for low-altitude drag measurement (late 1960s and early 1970s), (d) the Agena flight of LOGACS (1967), a Bell MESA accelerometer mounted on a rotating platform to spectrally shift low-frequency errors in the accelerometer, (e) a series of French low-level accelerometers (e.g. CACTUS, 1975), and (f) correction of differential accelerations for drag errors in measuring gravity gradient on a pair of satellites (GRACE, 2002). The independent invention of the drag-free satellite concept by Pugh and Lange (1964) to cancel external disturbance added implementation opportunities. Its first flight application was for ephemeris prediction improvement with the DISCOS flight (1972)-still the only extended free test mass flight. Then successful flights for reduced disturbance environment for science measurement with gyros on GP-B (2004) and for improved accuracy in geodesy and ocean studies (GOCE, 2009) each using accelerometer measurements to control the drag-canceling thrust. LISA, DECIGO, BBO and other gravity wave-measuring satellite systems will push the cancellation of drag to new levels.

  17. Measurement of drag and its cancellation

    DeBra, D B; Conklin, J W

    2011-01-01

    The design of drag cancellation missions of the future will take advantage of the technology experience of the past. The importance of data for modeling of the atmosphere led to at least six types of measurement: (a) balloon flights, (b) missile-launched falling spheres, (c) the 'cannonball' satellites of Ken Champion with accelerometers for low-altitude drag measurement (late 1960s and early 1970s), (d) the Agena flight of LOGACS (1967), a Bell MESA accelerometer mounted on a rotating platform to spectrally shift low-frequency errors in the accelerometer, (e) a series of French low-level accelerometers (e.g. CACTUS, 1975), and (f) correction of differential accelerations for drag errors in measuring gravity gradient on a pair of satellites (GRACE, 2002). The independent invention of the drag-free satellite concept by Pugh and Lange (1964) to cancel external disturbance added implementation opportunities. Its first flight application was for ephemeris prediction improvement with the DISCOS flight (1972)-still the only extended free test mass flight. Then successful flights for reduced disturbance environment for science measurement with gyros on GP-B (2004) and for improved accuracy in geodesy and ocean studies (GOCE, 2009) each using accelerometer measurements to control the drag-canceling thrust. LISA, DECIGO, BBO and other gravity wave-measuring satellite systems will push the cancellation of drag to new levels.

  18. Drag Performance of Twist Morphing MAV Wing

    Ismail N.I.

    2016-01-01

    Full Text Available Morphing wing is one of latest evolution found on MAV wing. However, due to few design problems such as limited MAV wing size and complicated morphing mechanism, the understanding of its aerodynamic behaviour was not fully explored. In fact, the basic drag distribution induced by a morphing MAV wing is still remained unknown. Thus, present work is carried out to compare the drag performance between a twist morphing wing with membrane and rigid MAV wing design. A quasi-static aeroelastic analysis by using the Ansys-Fluid Structure Interaction (FSI method is utilized in current works to predict the drag performance a twist morphing MAV wing design. Based on the drag pattern study, the results exhibits that the morphing wing has a partial similarities in overall drag pattern with the baseline (membrane and rigid wing. However, based CD analysis, it shows that TM wing induced higher CD magnitude (between 25% to 82% higher than to the baseline wing. In fact, TM wing also induced the largest CD increment (about 20% to 27% among the wings. The visualization on vortex structure revealed that TM wing also produce larger tip vortex structure (compared to baseline wings which presume to promote higher induce drag component and subsequently induce its higher CD performance.

  19. Helicopter overtriage in pediatric trauma.

    Michailidou, Maria; Goldstein, Seth D; Salazar, Jose; Aboagye, Jonathan; Stewart, Dylan; Efron, David; Abdullah, Fizan; Haut, Elliot R

    2014-11-01

    Helicopter Emergency Medical Services (HEMS) have been designed to provide faster access to trauma center care in cases of life-threatening injury. However, the ideal recipient population is not fully characterized, and indications for helicopter transport in pediatric trauma vary dramatically by county, state, and region. Overtriage, or unnecessary utilization, can lead to additional patient risk and expense. In this study we perform a nationwide descriptive analysis of HEMS for pediatric trauma and assess the incidence of overtriage in this group. We reviewed records from the American College of Surgeons National Trauma Data Bank (2008-11) and included patients less than 16 years of age who were transferred from the scene of injury to a trauma center via HEMS. Overtriage was defined as patients meeting all of the following criteria: Glasgow Coma Scale (GCS) equal to 15, absence of hypotension, an Injury Severity Score (ISS) less than 9, no need for procedure or critical care, and a hospital length of stay of less than 24 hours. A total of 19,725 patients were identified with a mean age of 10.5 years. The majority of injuries were blunt (95.6%) and resulted from motor vehicle crashes (48%) and falls (15%). HEMS transported patients were predominately normotensive (96%), had a GCS of 15 (67%), and presented with minor injuries (ISS<9, 41%). Overall, 28 % of patients stayed in the hospital for less than 24 hours, and the incidence of overtriage was 17%. Helicopter overtriage is prevalent among pediatric trauma patients nationwide. The ideal model to predict need for HEMS must consider clinical outcomes in the context of judicious resource utilization. The development of guidelines for HEMS use in pediatric trauma could potentially limit unnecessary transfers while still identifying children who require trauma center care in a timely fashion. Copyright © 2014. Published by Elsevier Inc.

  20. Stability theory and transition prediction applied to a general aviation fuselage

    Spall, R. E.; Wie, Y.-S.

    1993-01-01

    The linear stability of a fully three-dimensional boundary layer formed over a general aviation fuselage was investigated. The location of the onset of transition was estimated using the N-factor method. The results were compared with existing experimental data and indicate N-factors of approximately 8.5 on the side of the fuselage and 3.0 near the top. Considerable crossflow existed along the side of the body, which significantly affected the unstable modes present in the boundary layer. Fair agreement was found between the predicted frequency range of linear instability modes and available experimental data concerning the spectral content of the boundary layer.

  1. Hydrodynamic Drag on Streamlined Projectiles and Cavities

    Jetly, Aditya

    2016-04-19

    The air cavity formation resulting from the water-entry of solid objects has been the subject of extensive research due to its application in various fields such as biology, marine vehicles, sports and oil and gas industries. Recently we demonstrated that at certain conditions following the closing of the air cavity formed by the initial impact of a superhydrophobic sphere on a free water surface a stable streamlined shape air cavity can remain attached to the sphere. The formation of superhydrophobic sphere and attached air cavity reaches a steady state during the free fall. In this thesis we further explore this novel phenomenon to quantify the drag on streamlined shape cavities. The drag on the sphere-cavity formation is then compared with the drag on solid projectile which were designed to have self-similar shape to that of the cavity. The solid projectiles of adjustable weight were produced using 3D printing technique. In a set of experiments on the free fall of projectile we determined the variation of projectiles drag coefficient as a function of the projectiles length to diameter ratio and the projectiles specific weight, covering a range of intermediate Reynolds number, Re ~ 104 – 105 which are characteristic for our streamlined cavity experiments. Parallel free fall experiment with sphere attached streamlined air cavity and projectile of the same shape and effective weight clearly demonstrated the drag reduction effect due to the stress-free boundary condition at cavity liquid interface. The streamlined cavity experiments can be used as the upper bound estimate of the drag reduction by air layers naturally sustained on superhydrophobic surfaces in contact with water. In the final part of the thesis we design an experiment to test the drag reduction capacity of robust superhydrophobic coatings deposited on the surface of various model vessels.

  2. STUDY ON SAFETY TECHNOLOGY SCHEME OF THE UNMANNED HELICOPTER

    Z. Lin

    2013-08-01

    Full Text Available Nowadays the unmanned helicopter is widely used for its' unique strongpoint, however, the high failure rate of unmanned helicopter seriously limits its further application and development. For solving the above problems, in this paper, the reasons for the high failure rate of unmanned helicopter is analyzed and the corresponding solution schemes are proposed. The main problem of the failure cause of the unmanned helicopter is the aircraft engine fault, and the failure cause of the unmanned helicopter is analyzed particularly. In order to improving the safety performance of unmanned helicopter system, the scheme of adding the safety parachute system to the unmanned helicopter system is proposed and introduced. These schemes provide the safety redundancy of the unmanned helicopter system and lay on basis for the unmanned helicopter applying into residential areas.

  3. Helicopter Flight Procedures for Community Noise Reduction

    Greenwood, Eric

    2017-01-01

    A computationally efficient, semiempirical noise model suitable for maneuvering flight noise prediction is used to evaluate the community noise impact of practical variations on several helicopter flight procedures typical of normal operations. Turns, "quick-stops," approaches, climbs, and combinations of these maneuvers are assessed. Relatively small variations in flight procedures are shown to cause significant changes to Sound Exposure Levels over a wide area. Guidelines are developed for helicopter pilots intended to provide effective strategies for reducing the negative effects of helicopter noise on the community. Finally, direct optimization of flight trajectories is conducted to identify low noise optimal flight procedures and quantify the magnitude of community noise reductions that can be obtained through tailored helicopter flight procedures. Physically realizable optimal turns and approaches are identified that achieve global noise reductions of as much as 10 dBA Sound Exposure Level.

  4. 29 CFR 1910.183 - Helicopters.

    2010-07-01

    ... objects. The employer shall take all necessary precautions to protect employees from flying objects in the... safety. The size and weight of loads, and the manner in which loads are connected to the helicopter shall...

  5. Geodetic precession or dragging of inertial frames?

    Ashby, N.; Shahid-Saless, B.

    1990-01-01

    In metric theories of gravity the principle of general covariance allows one to describe phenomena by means of any convenient choice of coordinate system. In this paper it is shown that in an appropriately chosen coordinate system, geodetic precession of a gyroscope orbiting a spherically symmetric, spinning mass can be recast as a Lense-Thirring frame-dragging effect without invoking spatial curvature. The origin of this reference frame moves around the source but the frame axes point in fixed directions. The drag can be interpreted to arise from the orbital angular momentum of the source around the origin of the reference frame. In this reference frame the effects of geodetic precession and Lense-Thirring drag due to intrinsic angular momentum of the source have the same origin, namely, gravitomagnetism

  6. Experimental Investigation of a Helicopter Rotor Hub Wake

    Reich, David; Elbing, Brian; Schmitz, Sven

    2013-11-01

    A scaled model of a notional helicopter rotor hub was tested in the 48'' Garfield Thomas Water Tunnel at the Applied Research Laboratory Penn State. The main objectives of the experiment were to understand the spatial- and temporal content of the unsteady wake downstream of a rotor hub up to a distance corresponding to the empennage. Primary measurements were the total hub drag and velocity measurements at three nominal downstream locations. Various flow structures were identified and linked to geometric features of the hub model. The most prominent structures were two-per-revolution (hub component: scissors) and four-per-revolution (hub component: main hub arms) vortices shed by the hub. Both the two-per-revolution and four-per-revolution structures persisted far downstream of the hub, but the rate of dissipation was greater for the four-per-rev structures. This work provides a dataset for enhanced understanding of the fundamental physics underlying rotor hub flows and serves as validation data for future CFD analyses.

  7. Flow Structures within a Helicopter Rotor Hub Wake

    Elbing, Brian; Reich, David; Schmitz, Sven

    2015-11-01

    A scaled model of a notional helicopter rotor hub was tested in the 48'' Garfield Thomas Water Tunnel at the Applied Research Laboratory Penn State. The measurement suite included total hub drag and wake velocity measurements (LDV, PIV, stereo-PIV) at three downstream locations. The main objective was to understand the spatiotemporal evolution of the unsteady wake between the rotor hub and the nominal location of the empennage (tail). Initial analysis of the data revealed prominent two- and four-per-revolution fluid structures linked to geometric hub features persisting into the wake far-field. In addition, a six-per-revolution fluid structure was observed in the far-field, which is unexpected due to the lack of any hub feature with the corresponding symmetry. This suggests a nonlinear interaction is occurring within the wake to generate these structures. This presentation will provide an overview of the experimental data and analysis with particular emphasis on these six-per-revolution structures.

  8. Attack Helicopter Operations: Art or Science

    1991-05-13

    ATTACK HELICOPTER OPERATIONS: ART OR SCIENCE ? BY LIEUTENANT COLONEL JAN CALLEN United States Army DISTRIBUTION STATEMENT A: Approved for public release...TASK IWORK UNIT ELEMENT NO. NO. NO. ACCESSION NC 11. TITLE (Include Socurity Classification) Attack Helicopter Operations: Art or Science ? 12. PERSONAL...OPERATIONS: ART OR SCIENCE ? AN INDIVIDUAL STUDY PROJECT by Lieutenant Colonel Jan Callen United States Army Colonel Greg Snelgrove Project Adviser U.S

  9. Helicopter training simulators: Key market factors

    Mcintosh, John

    1992-01-01

    Simulators will gain an increasingly important role in training helicopter pilots only if the simulators are of sufficient fidelity to provide positive transfer of skills to the aircraft. This must be done within an economic model of return on investment. Although rotor pilot demand is still only a small percentage of overall pilot requirements, it will grow in significance. This presentation described the salient factors influencing the use of helicopter training simulators.

  10. Fuselage Burnthrough Protection for Increased Postcrash Occupant Survivability: Safety Benefit Analysis Based on Past Accidents

    Cherry, Ray

    1999-01-01

    .... The methodology gives a reasonable assessment of the tolerance on the predicted levels. Fire hardening of fuselages will provide benefits in terms of enhanced occupant survival and may be found to be cost beneficial if low-cost solutions can be found...

  11. Hybrid-Wing-Body Vehicle Composite Fuselage Analysis and Case Study

    Mukhopadhyay, Vivek

    2014-01-01

    Recent progress in the structural analysis of a Hybrid Wing-Body (HWB) fuselage concept is presented with the objective of structural weight reduction under a set of critical design loads. This pressurized efficient HWB fuselage design is presently being investigated by the NASA Environmentally Responsible Aviation (ERA) project in collaboration with the Boeing Company, Huntington Beach. The Pultruded Rod-Stiffened Efficient Unitized Structure (PRSEUS) composite concept, developed at the Boeing Company, is approximately modeled for an analytical study and finite element analysis. Stiffened plate linear theories are employed for a parametric case study. Maximum deflection and stress levels are obtained with appropriate assumptions for a set of feasible stiffened panel configurations. An analytical parametric case study is presented to examine the effects of discrete stiffener spacing and skin thickness on structural weight, deflection and stress. A finite-element model (FEM) of an integrated fuselage section with bulkhead is developed for an independent assessment. Stress analysis and scenario based case studies are conducted for design improvement. The FEM model specific weight of the improved fuselage concept is computed and compared to previous studies, in order to assess the relative weight/strength advantages of this advanced composite airframe technology

  12. Design, Analysis, Fabrication and Testing of Grid-Stiffened for Fuselage Applications

    Shroff, S.

    2014-01-01

    The application of composites in aircraft structures has grown significantly in the past decade, and an increase in this growth in application has recently been achieved in fuselage designs for large civil aircraft such as the Boeing B787 and the Airbus A350. In conventional design philosophies,

  13. Fracture and strain rate behavior of airplane fuselage materials under blast loading

    Mediavilla Varas, J.; Soetens, F.; Kroon, E.; Aanhold, van J.E.; Meulen, van der O.R.; Sagimon, M.

    2010-01-01

    The dynamic behavior of three commonly used airplane fuselage materials is investigated, namely of Al2024-T3, Glare-3 and CFRP. Dynamic tensile tests using a servo-hydraulic and a light weight shock testing machine (LSM) have been performed. The results showed no strain rate effect on Al2024-T3 and

  14. Fracture and strain rate behavior of airplane fuselage materials under blast loading

    Mediavilla Varas, J.; Soetens, F.; Kroon, E.; Aanhold, J.E. van; Meulen, O.R. van der; Sagimon, M.

    2010-01-01

    The dynamic behavior of three commonly used airplane fuselage materials is investigated, namely of Al2024-T3, Glare-3 and CFRP. Dynamic tensile tests using a servo-hydraulic and a light weight shock testing machine (LSM) have been performed. The results showed no strain rate effect on Al2024-T3 and

  15. Fuselage boundary-layer refraction of fan tones radiated from an installed turbofan aero-engine.

    Gaffney, James; McAlpine, Alan; Kingan, Michael J

    2017-03-01

    A distributed source model to predict fan tone noise levels of an installed turbofan aero-engine is extended to include the refraction effects caused by the fuselage boundary layer. The model is a simple representation of an installed turbofan, where fan tones are represented in terms of spinning modes radiated from a semi-infinite circular duct, and the aircraft's fuselage is represented by an infinitely long, rigid cylinder. The distributed source is a disk, formed by integrating infinitesimal volume sources located on the intake duct termination. The cylinder is located adjacent to the disk. There is uniform axial flow, aligned with the axis of the cylinder, everywhere except close to the cylinder where there is a constant thickness boundary layer. The aim is to predict the near-field acoustic pressure, and in particular, to predict the pressure on the cylindrical fuselage which is relevant to assess cabin noise. Thus no far-field approximations are included in the modelling. The effect of the boundary layer is quantified by calculating the area-averaged mean square pressure over the cylinder's surface with and without the boundary layer included in the prediction model. The sound propagation through the boundary layer is calculated by solving the Pridmore-Brown equation. Results from the theoretical method show that the boundary layer has a significant effect on the predicted sound pressure levels on the cylindrical fuselage, owing to sound radiation of fan tones from an installed turbofan aero-engine.

  16. Frictional Coulomb drag in strong magnetic fields

    Bønsager, Martin Christian; Flensberg, Karsten; Hu, Ben Yu-Kuang

    1997-01-01

    A treatment of frictional Coulomb drag between two two-dimensional electron layers in a strong perpendicular magnetic field, within the independent electron picture, is presented. Assuming fully resolved Landau levels, the linear response theory expression for the transresistivity rho(21) is eval......A treatment of frictional Coulomb drag between two two-dimensional electron layers in a strong perpendicular magnetic field, within the independent electron picture, is presented. Assuming fully resolved Landau levels, the linear response theory expression for the transresistivity rho(21...

  17. Correlated Coulomb drag in capacitively coupled quantum-dot structures

    Kaasbjerg, Kristen; Jauho, Antti-Pekka

    2016-01-01

    We study theoretically Coulomb drag in capacitively coupled quantum dots (CQDs) -- a biasdriven dot coupled to an unbiased dot where transport is due to Coulomb mediated energy transfer drag. To this end, we introduce a master-equation approach which accounts for higher-order tunneling (cotunneling......) processes as well as energy-dependent lead couplings, and identify a mesoscopic Coulomb drag mechanism driven by nonlocal multi-electron cotunneling processes. Our theory establishes the conditions for a nonzero drag as well as the direction of the drag current in terms of microscopic system parameters...... on Coulomb drag in CQD systems....

  18. The effect of sodium hydroxide on drag reduction using banana peel as a drag reduction agent

    Kaur, H.; Jaafar, A.

    2018-02-01

    Drag reduction is observed as reduced frictional pressure losses under turbulent flow conditions. Drag reduction agent such as polymers can be introduced to increase the flowrate of water flowing and reduce the water accumulation in the system. Currently used polymers are synthetic polymers, which will harm our environment in excessive use of accumulation. A more environmentally-friendly drag reduction agent such as the polymer derived from natural sources or biopolymer, is then required for such purpose. As opposed to the synthetic polymers, the potential of biopolymers as drag reduction agents, especially those derived from a local plant source are not extensively explored. The drag reduction of a polymer produced from a local plant source within the turbulent regime was explored and assessed in this study using a rheometer, where a reduced a torque produced was perceived as a reduction of drag. This method proposed is less time consuming and is more practical which is producing carboxymethylcellulose from the banana peel. The cellulose powder was converted to carboxymethylcellulose (CMC) by etherification process. The carboxymethylation reaction during the synthesizing process was then optimized against the reaction temperature, reaction time and solubility. The biopolymers were then rheologically characterized, where the viscoelastic effects and the normal stresses produced by these biopolymers were utilized to further relate and explain the drag reduction phenomena. The research was structured to focus on producing the biopolymer and to assess the drag reduction ability of the biopolymer produced. The rheological behavior of the biopolymers was then analyzed based on the ability of reducing drag. The results are intended to expand the currently extremely limited experimental database. Based on the results, the biopolymer works as a good DRA.

  19. Magnetic Viscous Drag for Friction Labs

    Gaffney, Chris; Catching, Adam

    2016-01-01

    The typical friction lab performed in introductory mechanics courses is usually not the favorite of either the student or the instructor. The measurements are not all that easy to make, and reproducibility is usually a troublesome issue. This paper describes the augmentation of such a friction lab with a study of the viscous drag on a magnet…

  20. High accuracy satellite drag model (HASDM)

    Storz, Mark F.; Bowman, Bruce R.; Branson, Major James I.; Casali, Stephen J.; Tobiska, W. Kent

    The dominant error source in force models used to predict low-perigee satellite trajectories is atmospheric drag. Errors in operational thermospheric density models cause significant errors in predicted satellite positions, since these models do not account for dynamic changes in atmospheric drag for orbit predictions. The Air Force Space Battlelab's High Accuracy Satellite Drag Model (HASDM) estimates and predicts (out three days) a dynamically varying global density field. HASDM includes the Dynamic Calibration Atmosphere (DCA) algorithm that solves for the phases and amplitudes of the diurnal and semidiurnal variations of thermospheric density near real-time from the observed drag effects on a set of Low Earth Orbit (LEO) calibration satellites. The density correction is expressed as a function of latitude, local solar time and altitude. In HASDM, a time series prediction filter relates the extreme ultraviolet (EUV) energy index E10.7 and the geomagnetic storm index ap, to the DCA density correction parameters. The E10.7 index is generated by the SOLAR2000 model, the first full spectrum model of solar irradiance. The estimated and predicted density fields will be used operationally to significantly improve the accuracy of predicted trajectories for all low-perigee satellites.

  1. Judicial civil procedure dragging out in Kosovo

    Rrustem Qehaja

    2016-03-01

    Full Text Available This article tends to deal with one of the most worrying issues in the judicial system of Kosovo the problem of judicial civil procedure dragging out. The article analyses the reasons of these dragging outs of the judicial civil procedure focusing on the context of one of the basic procedural principles in civil procedure-the principle of economy or efficiency in the courts. Dragging out of civil procedure in Kosovo has put in question not only the basic principles of civil procedure, but it also challenges the general principles related to human rights and freedoms sanctioned not only by the highest legal act of the country, but also with international treaties. The article tends to give a reflection to the most important reasons that effect and influence in these dragging outs of civil procedure, as well as, at the same time aims to give the necessary alternatives to pass through them by identifying dilemmas within the judicial practice. As a result, the motives of this scientific paper are exactly focused at the same time on identifying the dilemmas, as well as presenting ideas, to overstep them, including the judicial practice of the European Court of Human Rights on Article 6 of the European Convention on Human Rights, by which it is given the possibility to offering people efficient and within a reasonable time legal protection of their rights before national courts. For these reasons, the paper elaborates this issue based on both, the legal theory and judicial practice.

  2. Measurements of drag and flow over biofilm

    Hartenberger, Joel; Gose, James W.; Perlin, Marc; Ceccio, Steven L.

    2017-11-01

    Microbial `slime' biofilms detrimentally affect the performance of every day systems from medical devices to large ocean-going vessels. In flow applications, the presence of biofilm typically results in a drag increase and may alter the turbulence in the adjacent boundary layer. Recent studies emphasize the severity of the drag penalty associated with soft biofouling and suggest potential mechanisms underlying the increase; yet, fundamental questions remain-such as the role played by compliance and the contribution of form drag to the overall resistance experienced by a fouled system. Experiments conducted on live biofilm and 3D printed rigid replicas in the Skin-Friction Flow Facility at the University of Michigan seek to examine these factors. The hydrodynamic performance of the biofilms grown on test panels was evaluated through pressure drop measurements as well as conventional and microscale PIV. High-resolution, 3D rigid replicas of select cases were generated via additive manufacturing using surface profiles obtained from a laser scanning system. Drag and flow measurements will be presented along with details of the growth process and the surface profile characterization method.

  3. Drag Reducing and Cavitation Resistant Coatings

    Pease, Leonard F.

    2016-12-28

    Client, Green Building Systems (GBS), presented PNNL a coating reported to reduce drag and prevent cavitation damage on marine vessels, turbines and pumps. The composition of the coating remains proprietary but has as constituents including silicon oxides, aliphatic carbon chains, and fluorine rich particles. The coating is spray applied to surfaces. Prior GBS testing and experiments suggest reduction of both drag and cavitation on industrial scale propellers, but the underlying mechanism for these effects remains unclear. Yet, the application is compelling because even modest reductions in drag to marine vessels and cavitation to propellers and turbines present a significant economic and environmental opportunity. To discern among possible mechanisms, PNNL considered possible mechanisms with the client, executed multiple experiments, and completed one theoretical analysis (see appendix). The remainder of this report first considers image analysis to gain insight into drag reduction mechanisms and then exposes the coating to cavitation to explore its response to an intensely cavitating environment. Although further efforts may be warranted to confirm mechanisms, this report presents a first investigation into these coatings within the scope and resources of the technology assistance program (TAP).

  4. The making of helicopters: its strategic implications for EMS helicopter operations.

    Thomas, F

    1998-01-01

    The purpose of this article is to provide EMS helicopter personnel with an understanding of the civil helicopter manufacturing industry. Specifically, this article examines the current helicopter marketplace and how various manufactures are responding to the recent decline in new helicopter sales. This article further describes how helicopters are designed and manufactured and how global markets, international competition, and strategic considerations are influencing future helicopter design and production. Data for this paper were obtained from a literature search through the ABI-inform Telnet Services offered through the University of Utah Marriott Library. On a search of "helicopter" during the past 5 years, 566 abstracts were identified, all of which were reviewed for information related to the purpose of this article. Forty-seven articles were identified and read in detail for information that may have related to the purpose of this article. In addition, a library search to identify textbooks that describe helicopter production systems was undertaken but did not identify any written resources. Because of the lack of written resources available in writing this article, a direct interview survey of leading helicopter manufactures, associations, and industry writers was conducted. Only information that was considered "public knowledge" was available because of concerns by the various manufactures that publication of confidential information could be detrimental to their competitive advantage. Because helicopter-manufacturing plants were not located within easy travel range, no direct observation of the production facilities could be undertaken. Furthermore, information regarding production and operational management was not easily accessible because the data were not published or were considered confidential. Therefore industry analysis had to take place through direct survey interviewing technique and data obtained through an analysis of the available published

  5. Drag coefficient Variability and Thermospheric models

    Moe, Kenneth

    Satellite drag coefficients depend upon a variety of factors: The shape of the satellite, its altitude, the eccentricity of its orbit, the temperature and mean molecular mass of the ambient atmosphere, and the time in the sunspot cycle. At altitudes where the mean free path of the atmospheric molecules is large compared to the dimensions of the satellite, the drag coefficients can be determined from the theory of free-molecule flow. The dependence on altitude is caused by the concentration of atomic oxygen which plays an important role by its ability to adsorb on the satellite surface and thereby affect the energy loss of molecules striking the surface. The eccentricity of the orbit determines the satellite velocity at perigee, and therefore the energy of the incident molecules relative to the energy of adsorption of atomic oxygen atoms on the surface. The temperature of the ambient atmosphere determines the extent to which the random thermal motion of the molecules influences the momentum transfer to the satellite. The time in the sunspot cycle affects the ambient temperature as well as the concentration of atomic oxygen at a particular altitude. Tables and graphs will be used to illustrate the variability of drag coefficients. Before there were any measurements of gas-surface interactions in orbit, Izakov and Cook independently made an excellent estimate that the drag coefficient of satellites of compact shape would be 2.2. That numerical value, independent of altitude, was used by Jacchia to construct his model from the early measurements of satellite drag. Consequently, there is an altitude dependent bias in the model. From the sparce orbital experiments that have been done, we know that the molecules which strike satellite surfaces rebound in a diffuse angular distribution with an energy loss given by the energy accommodation coefficient. As more evidence accumulates on the energy loss, more realistic drag coefficients are being calculated. These improved drag

  6. Long Island north shore helicopter route environmental study

    2012-02-21

    This report presents the results of the noise and emissions analysis of helicopter operations along the North Shore Helicopter Route of Long Island, New York performed by the Federal Aviation Administration, with the assistance of the Volpe Center...

  7. Analysing Blast and Fragment Penetration Effects on Composite Helicopter Structures

    van't Hof, C; Herlaar, K; Luyten, J. M; van der Jagt, M. J

    2005-01-01

    .... The last decades the threat of helicopters has increased in military circumstances. Consequently the helicopters will be exposed to weapon effects like high blast loads and fragment impact more frequently...

  8. Helicopter Rotor Blade Monitoring using Autonomous Wireless Sensor Network

    Sanchez Ramirez, Andrea; Loendersloot, Richard; Tinga, Tiedo; Basu, B.

    2013-01-01

    The advancement on Wireless Sensor Networks for vibration monitoring presents important possibilities for helicopter rotor health and usage monitoring. While main rotor blades account for the main source of lift for helicopters, rotor induced vibration establishes an important source for

  9. Input Shaping for Helicopter Slung Load Swing Reduction

    Bisgaard, Morten; la Cour-Harbo, Anders; Bendtsen, Jan Dimon

    2008-01-01

    This chapter presents a feedforward swing reducing control system for augmenting already existing helicopter controllers and enables slung load flight with autonomous helicopters general cargo transport. The feedforward controller is designed to avoid excitation of the lightly damped modes...

  10. 77 FR 56581 - Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

    2012-09-13

    ... Corporation Helicopters AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Supplemental notice of... airworthiness directive (AD) for the Sikorsky Aircraft Corporation (Sikorsky) Model S-92A helicopter, which... proposed AD, contact Sikorsky Aircraft Corporation, Attn: Manager, Commercial Technical Support, mailstop...

  11. 77 FR 23382 - Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

    2012-04-19

    ... Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters AGENCY: Federal Aviation Administration (FAA... Aircraft Corporation (Sikorsky) Model S-92A helicopters. This AD was prompted by the manufacturer's..., contact Sikorsky Aircraft Corporation, Attn: Manager, Commercial Technical Support, Mailstop s581a, 6900...

  12. 77 FR 41889 - Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

    2012-07-17

    ... Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters AGENCY: Federal Aviation Administration (FAA... airworthiness directive (AD) for Sikorsky Aircraft Corporation (Sikorsky) Model S-92A helicopters. This AD... identified in this AD, contact Sikorsky Aircraft Corporation, Attn: Manager, Commercial Technical Support...

  13. 77 FR 49710 - Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

    2012-08-17

    ... Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters AGENCY: Federal Aviation Administration (FAA... Aircraft Corporation (Sikorsky) Model S-76A helicopters to require modifying the electric rotor brake (ERB... service information identified in this AD, contact Sikorsky Aircraft Corporation, Attn: Manager...

  14. Correlated Coulomb Drag in Capacitively Coupled Quantum-Dot Structures.

    Kaasbjerg, Kristen; Jauho, Antti-Pekka

    2016-05-13

    We study theoretically Coulomb drag in capacitively coupled quantum dots (CQDs)-a bias-driven dot coupled to an unbiased dot where transport is due to Coulomb mediated energy transfer drag. To this end, we introduce a master-equation approach that accounts for higher-order tunneling (cotunneling) processes as well as energy-dependent lead couplings, and identify a mesoscopic Coulomb drag mechanism driven by nonlocal multielectron cotunneling processes. Our theory establishes the conditions for a nonzero drag as well as the direction of the drag current in terms of microscopic system parameters. Interestingly, the direction of the drag current is not determined by the drive current, but by an interplay between the energy-dependent lead couplings. Studying the drag mechanism in a graphene-based CQD heterostructure, we show that the predictions of our theory are consistent with recent experiments on Coulomb drag in CQD systems.

  15. Significance of relative velocity in drag force or drag power estimation for a tethered float

    Vethamony, P.; Sastry, J.S.

    There is difference in opinion regarding the use of relative velocity instead of particle velocity alone in the estimation of drag force or power. In the present study, a tethered spherical float which undergoes oscillatory motion in regular waves...

  16. Drag force, drag torque, and Magnus force coefficients of rotating spherical particle moving in fluid

    Lukerchenko, Nikolay; Kvurt, Y.; Keita, Ibrahima; Chára, Zdeněk; Vlasák, Pavel

    2012-01-01

    Roč. 30, č. 1 (2012), s. 55-67 ISSN 0272-6351 R&D Projects: GA AV ČR IAA200600603; GA ČR GA103/09/1718 Institutional research plan: CEZ:AV0Z20600510 Keywords : drag force * drag torque * Magnus force * Reynolds number * rotational Reynolds number Subject RIV: BK - Fluid Dynamics Impact factor: 0.435, year: 2012

  17. On the Drag Effect of a Refuelling Pellet

    Chang, Tinghong; Michelsen, Poul

    1981-01-01

    A refueling pellet is subjected mainly to two kinds of drags: (1) inertial drag caused by the motion of the pellet relative to the surrounding plasma, and (2) ablation drag caused by an uneven ablation rate of the front and the rear surface of the pellet in an inhomogeneous plasma. Computational ...... results showed that for reasonable combinations of pellet size and injection speed, the drag effect is hardly detectable for plasma conditions prevailing in current large tokamaks....

  18. 14 CFR 136.13 - Helicopter performance plan and operations.

    2010-01-01

    ... 14 Aeronautics and Space 3 2010-01-01 2010-01-01 false Helicopter performance plan and operations... Helicopter performance plan and operations. (a) Each operator must complete a performance plan before each helicopter commercial air tour, or flight operated under 14 CFR 91.146 or 91.147. The pilot in command must...

  19. 14 CFR 135.207 - VFR: Helicopter surface reference requirements.

    2010-01-01

    ... 14 Aeronautics and Space 3 2010-01-01 2010-01-01 false VFR: Helicopter surface reference... VFR/IFR Operating Limitations and Weather Requirements § 135.207 VFR: Helicopter surface reference requirements. No person may operate a helicopter under VFR unless that person has visual surface reference or...

  20. CHANGES IN FLIGHT TRAINEE PERFORMANCE FOLLOWING SYNTHETIC HELICOPTER FLIGHT TRAINING.

    CARO, PAUL W., JR.; ISLEY, ROBERT N.

    A STUDY WAS CONDUCTED AT THE U.S. ARMY PRIMARY HELICOPTER SCHOOL, FORT WOLTERS, TEXAS, TO DETERMINE WHETHER THE USE OF A HELICOPTER TRAINING DEVICE WOULD IMPROVE STUDENT PERFORMANCE DURING SUBSEQUENT HELICOPTER CONTACT FLIGHT TRAINING. SUBJECTS WERE TWO EXPERIMENTAL GROUPS AND TWO CONTROL GROUPS OF WARRANT OFFICER CANDIDATES ENROLLED FOR A…

  1. Helicopter emergency medical service patient transport safe at night?

    Peters, J.H.; Wageningen, B. van; Hoogerwerf, N.; Biert, J.

    2014-01-01

    OBJECTIVE: Dutch helicopter emergency medical services are available 24/7. Working without daylight brings additional challenges, both in patient care and in-flight operation. We retrospectively evaluated the safety of this nighttime helicopter transportation of patients. METHODS: Our helicopter

  2. 14 CFR 136.11 - Helicopter floats for over water.

    2010-01-01

    ... 14 Aeronautics and Space 3 2010-01-01 2010-01-01 false Helicopter floats for over water. 136.11... TOURS AND NATIONAL PARKS AIR TOUR MANAGEMENT National Air Tour Safety Standards § 136.11 Helicopter floats for over water. (a) A helicopter used in commercial air tours over water beyond the shoreline must...

  3. 46 CFR 132.320 - Helicopter-landing decks.

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Helicopter-landing decks. 132.320 Section 132.320 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OFFSHORE SUPPLY VESSELS FIRE-PROTECTION EQUIPMENT Miscellaneous § 132.320 Helicopter-landing decks. Each vessel with a helicopter-landing deck must...

  4. 78 FR 51123 - Airworthiness Directives; Bell Helicopter Textron

    2013-08-20

    ...-0734; Directorate Identifier 2012-SW-080-AD] RIN 2120-AA64 Airworthiness Directives; Bell Helicopter...). SUMMARY: We propose to supersede an existing airworthiness directive (AD) for Bell Helicopter Textron (Bell) Model 222, 222B, 222U, 230, and 430 helicopters. The existing AD currently requires inspecting...

  5. 78 FR 44043 - Airworthiness Directives; Eurocopter France Helicopters

    2013-07-23

    ... lead to failure of the swashplate and subsequent loss of helicopter control. DATES: We must receive..., which may cause failure of MRH parts and loss of control of the helicopter. The EASA AD requires..., Section 2.3 Flight Envelope, Item 2 Temperature Limits, of the helicopter's Rotorcraft Flight Manual (RFM...

  6. Helicopter industry - early beginnings to now; an outlook on the helicopter market and its major players in the rotorcraft industry

    Spranger, L.

    2013-01-01

    The helicopter is probably the most flexible aircraft that we know today. Although its history dates back to around 1500, the first practical helicopter wasn’t manufactured until the 1940s, roughly three decades after the Wright brothers’ first powered human flight. Today, helicopters fulfil a wide

  7. Minimum-complexity helicopter simulation math model

    Heffley, Robert K.; Mnich, Marc A.

    1988-01-01

    An example of a minimal complexity simulation helicopter math model is presented. Motivating factors are the computational delays, cost, and inflexibility of the very sophisticated math models now in common use. A helicopter model form is given which addresses each of these factors and provides better engineering understanding of the specific handling qualities features which are apparent to the simulator pilot. The technical approach begins with specification of features which are to be modeled, followed by a build up of individual vehicle components and definition of equations. Model matching and estimation procedures are given which enable the modeling of specific helicopters from basic data sources such as flight manuals. Checkout procedures are given which provide for total model validation. A number of possible model extensions and refinement are discussed. Math model computer programs are defined and listed.

  8. Aerodynamic drag reduction by vertical splitter plates

    Gilliéron, Patrick; Kourta, Azeddine

    2010-01-01

    The capacity of vertical splitter plates placed at the front or the rear of a simplified car geometry to reduce drag, with and without skew angle, is investigated for Reynolds numbers between 1.0 × 106 and 1.6 × 106. The geometry used is a simplified geometry to represent estate-type vehicles, for the rear section, and MPV-type vehicle. Drag reductions of nearly 28% were obtained for a zero skew angle with splitter plates placed at the front of models of MPV or utility vehicles. The results demonstrate the advantage of adapting the position and orientation of the splitter plates in the presence of a lateral wind. All these results confirm the advantage of this type of solution, and suggest that this expertise should be used in the automotive field to reduce consumption and improve dynamic stability of road vehicles.

  9. Aerodynamic drag reduction by vertical splitter plates

    Gillieron, Patrick [Renault Group, Research Division, Fluid Mechanics and Aerodynamics, Guyancourt (France); Kourta, Azeddine [Polytech' Orleans, Institut PRISME, ESA, Orleans (France)

    2010-01-15

    The capacity of vertical splitter plates placed at the front or the rear of a simplified car geometry to reduce drag, with and without skew angle, is investigated for Reynolds numbers between 1.0 x 10{sup 6} and 1.6 x 10{sup 6}. The geometry used is a simplified geometry to represent estate-type vehicles, for the rear section, and MPV-type vehicle. Drag reductions of nearly 28% were obtained for a zero skew angle with splitter plates placed at the front of models of MPV or utility vehicles. The results demonstrate the advantage of adapting the position and orientation of the splitter plates in the presence of a lateral wind. All these results confirm the advantage of this type of solution, and suggest that this expertise should be used in the automotive field to reduce consumption and improve dynamic stability of road vehicles. (orig.)

  10. Switchable and Tunable Aerodynamic Drag on Cylinders

    Guttag, Mark; Lopéz Jiménez, Francisco; Upadhyaya, Priyank; Kumar, Shanmugam; Reis, Pedro

    We report results on the performance of Smart Morphable Surfaces (Smporhs) that can be mounted onto cylindrical structures to actively reduce their aerodynamic drag. Our system comprises of an elastomeric thin shell with a series of carefully designed subsurface cavities that, once depressurized, lead to a dramatic deformation of the surface topography, on demand. Our design is inspired by the morphology of the giant cactus (Carnegiea gigantea) which possesses an array of axial grooves, thought to help reduce aerodynamic drag, thereby enhancing the structural robustness of the plant under wind loading. We perform systematic wind tunnel tests on cylinders covered with our Smorphs and characterize their aerodynamic performance. The switchable and tunable nature of our system offers substantial advantages for aerodynamic performance when compared to static topographies, due to their operation over a wider range of flow conditions.

  11. Vertical drop test of a transport fuselage center section including the wheel wells

    Williams, M. S.; Hayduk, R. J.

    1983-01-01

    A Boeing 707 fuselage section was drop tested to measure structural, seat, and anthropomorphic dummy response to vertical crash loads. The specimen had nominally zero pitch, roll and yaw at impact with a sink speed of 20 ft/sec. Results from this drop test and other drop tests of different transport sections will be used to prepare for a full-scale crash test of a B-720.

  12. Slender body theory programmed for bodies with arbitrary cross section. [including fuselages

    Werner, J.; Krenkel, A. R.

    1978-01-01

    A computer program developed for determining the subsonic pressure, force, and moment coefficients for a fuselage-type body using slender body theory is described. The program is suitable for determining the angle of attack and sideslipping characteristics of such bodies in the linear range where viscous effects are not predominant. Procedures developed which are capable of treating cross sections with corners or regions of large curvature are outlined.

  13. Hybrid Wing-Body Pressurized Fuselage and Bulkhead, Design and Optimization

    Mukhopadhyay, Vivek

    2013-01-01

    The structural weight reduction of a pressurized Hybrid Wing-Body (HWB) fuselage is a serious challenge. Hence, research and development are presently being continued at NASA under the Environmentally Responsible Aviation (ERA) and Subsonic Fixed Wing (SFW) projects in collaboration with the Boeing Company, Huntington Beach and Air Force Research Laboratory (AFRL). In this paper, a structural analysis of the HWB fuselage and bulkhead panels is presented, with the objectives of design improvement and structural weight reduction. First, orthotropic plate theories for sizing, and equivalent plate analysis with appropriate simplification are considered. Then parametric finite-element analysis of a fuselage section and bulkhead are conducted using advanced stitched composite structural concepts, which are presently being developed at Boeing for pressurized HWB flight vehicles. With this advanced stiffened-shell design, structural weights are computed and compared to the thick sandwich, vaulted-ribbed-shell, and multi-bubble stiffened-shell structural concepts that had been studied previously. The analytical and numerical results are discussed to assess the overall weight/strength advantages.

  14. Hybrid Wing-Body (HWB) Pressurized Fuselage Modeling, Analysis, and Design for Weight Reduction

    Mukhopadhyay, Vivek

    2012-01-01

    This paper describes the interim progress for an in-house study that is directed toward innovative structural analysis and design of next-generation advanced aircraft concepts, such as the Hybrid Wing-Body (HWB) and the Advanced Mobility Concept-X flight vehicles, for structural weight reduction and associated performance enhancement. Unlike the conventional, skin-stringer-frame construction for a cylindrical fuselage, the box-type pressurized fuselage panels in the HWB undergo significant deformation of the outer aerodynamic surfaces, which must be minimized without significant structural weight penalty. Simple beam and orthotropic plate theory is first considered for sizing, analytical verification, and possible equivalent-plate analysis with appropriate simplification. By designing advanced composite stiffened-shell configurations, significant weight reduction may be possible compared with the sandwich and ribbed-shell structural concepts that have been studied previously. The study involves independent analysis of the advanced composite structural concepts that are presently being developed by The Boeing Company for pressurized HWB flight vehicles. High-fidelity parametric finite-element models of test coupons, panels, and multibay fuselage sections, were developed for conducting design studies and identifying critical areas of potential failure. Interim results are discussed to assess the overall weight/strength advantages.

  15. Application of Carbon Fibre Truss Technology to the Fuselage Structure of the SKYLON Spaceplane

    Varvill, R.; Bond, A.

    A reusable SSTO spaceplane employing dual mode airbreathing/rocket engines, such as SKYLON, has a voluminous fuselage in order to accommodate the considerable quantities of hydrogen fuel needed for the ascent. The loading intensity which this fuselage has to withstand is relatively low due to the modest in-flight inertial accelerations coupled with the very low density of liquid hydrogen. Also the requirement to accommo- date considerable temperature differentials between the internal cryogenic tankage and the aerodynamically heated outer skin of the vehicle imposes an additional design constraint that results in an optimum fuselage structural concept very different to conventional aircraft or rocket practice. Several different structural con- cepts exist for the primary loadbearing structure. This paper explores the design possibilities of the various types and explains why an independent near ambient temperature CFRP truss structure was selected for the SKYLON vehicle. The construction of such a truss structure, at a scale not witnessed since the days of the airship, poses a number of manufacturing and design difficulties. In particular the construction of the nodes and their attachment to the struts is considered to be a key issue. This paper describes the current design status of the overall truss geometry, strut construction and manufacturing route, and the final method of assembly. The results of a preliminary strut and node test programme are presented which give confidence that the design targets will eventually be met.

  16. An Airplane Design having a Wing with Fuselage Attached to Each Tip

    Spearman, Leroy M.

    2001-01-01

    This paper describes the conceptual design of an airplane having a low aspect ratio wing with fuselages that are attached to each wing tip. The concept is proposed for a high-capacity transport as an alternate to progressively increasing the size of a conventional transport design having a single fuselage with cantilevered wing panels attached to the sides and tail surfaces attached at the rear. Progressively increasing the size of conventional single body designs may lead to problems in some area's such as manufacturing, ground-handling and aerodynamic behavior. A limited review will be presented of some past work related to means of relieving some size constraints through the use of multiple bodies. Recent low-speed wind-tunnel tests have been made of models representative of the inboard-wing concept. These models have a low aspect ratio wing with a fuselage attached to each tip. Results from these tests, which included force measurements, surface pressure measurements, and wake surveys, will be presented herein.

  17. Simulating Electrophoresis with Discrete Charge and Drag

    Mowitz, Aaron J.; Witten, Thomas A.

    A charged asymmetric rigid cluster of colloidal particles in saline solution can respond in exotic ways to an electric field: it may spin or move transversely. These distinctive motions arise from the drag force of the neutralizing countercharge surrounding the cluster. Because of this drag, calculating the motion of arbitrary asymmetric objects with nonuniform charge is impractical by conventional methods. Here we present a new method of simulating electrophoresis, in which we replace the continuous object and the surrounding countercharge with discrete point-draggers, called Stokeslets. The balance of forces imposes a linear, self-consistent relation among the drag and Coulomb forces on the Stokeslets, which allows us to easily determine the object's motion via matrix inversion. By explicitly enforcing charge+countercharge neutrality, the simulation recovers the distinctive features of electrophoretic motion to few-percent accuracy using as few as 1000 Stokeslets. In particular, for uniformly charged objects, we observe the characteristic Smoluchowski independence of mobility on object size and shape. We then discuss electrophoretic motion of asymmetric objects, where our simulation method is particularly advantageous. This work is supported by a Grant from the US-Israel Binational Science Foundation.

  18. Drag reduction by a polymeric aluminium soap

    Rodriquez, F.

    1971-04-12

    The pressure drop per unit length of pipe during the turbulent flow of liquids is reduced by certain additives. Most such drag reducing or friction-reducing agents are polymers of very high molecular weight. Some time ago, aluminum soaps were described as reducing drag in organic solvents, but the viscosity in laminar flow of such solutions was much higher than that of the solvents. More recently, it was found that aluminum dioleate and aluminum palmitate did not reduce turbulent friction until the solute concentration reached 0.75%. The viscosity at this concentration was 2 or 3 times that of the solvent, benzene. Exploratory work with aluminum di-2-ethylhexanoate indicates that it is an effective drag-reducing agent at concentrations which increase the viscosity of toluene by less than 10%. The dependence of the effectiveness on concentration is similar to that of most polymers. Taking into account the normal change in friction factor with Reynolds number together with end effects in the apparatus, the maximum effectiveness (x = 54 cm) corresponds to a a decrease in friction factor to less than a quarter of the original value for toluene alone. (13 refs.)

  19. Helicopter trajectory planning using optimal control theory

    Menon, P. K. A.; Cheng, V. H. L.; Kim, E.

    1988-01-01

    A methodology for optimal trajectory planning, useful in the nap-of-the-earth guidance of helicopters, is presented. This approach uses an adjoint-control transformation along with a one-dimensional search scheme for generating the optimal trajectories. In addition to being useful for helicopter nap-of-the-earth guidance, the trajectory planning solution is of interest in several other contexts, such as robotic vehicle guidance and terrain-following guidance for cruise missiles and aircraft. A distinguishing feature of the present research is that the terrain constraint and the threat envelopes are incorporated in the equations of motion. Second-order necessary conditions are examined.

  20. Thermospheric density and satellite drag modeling

    Mehta, Piyush Mukesh

    The United States depends heavily on its space infrastructure for a vast number of commercial and military applications. Space Situational Awareness (SSA) and Threat Assessment require maintaining accurate knowledge of the orbits of resident space objects (RSOs) and the associated uncertainties. Atmospheric drag is the largest source of uncertainty for low-perigee RSOs. The uncertainty stems from inaccurate modeling of neutral atmospheric mass density and inaccurate modeling of the interaction between the atmosphere and the RSO. In order to reduce the uncertainty in drag modeling, both atmospheric density and drag coefficient (CD) models need to be improved. Early atmospheric density models were developed from orbital drag data or observations of a few early compact satellites. To simplify calculations, densities derived from orbit data used a fixed CD value of 2.2 measured in a laboratory using clean surfaces. Measurements from pressure gauges obtained in the early 1990s have confirmed the adsorption of atomic oxygen on satellite surfaces. The varying levels of adsorbed oxygen along with the constantly changing atmospheric conditions cause large variations in CD with altitude and along the orbit of the satellite. Therefore, the use of a fixed CD in early development has resulted in large biases in atmospheric density models. A technique for generating corrections to empirical density models using precision orbit ephemerides (POE) as measurements in an optimal orbit determination process was recently developed. The process generates simultaneous corrections to the atmospheric density and ballistic coefficient (BC) by modeling the corrections as statistical exponentially decaying Gauss-Markov processes. The technique has been successfully implemented in generating density corrections using the CHAMP and GRACE satellites. This work examines the effectiveness, specifically the transfer of density models errors into BC estimates, of the technique using the CHAMP and

  1. Finite Element Simulations of Two Vertical Drop Tests of F-28 Fuselage Sections

    Jackson, Karen E.; Littell, Justin D.; Annett, Martin S.; Haskin, Ian M.

    2018-01-01

    In March 2017, a vertical drop test of a forward fuselage section of a Fokker F-28 MK4000 aircraft was conducted as part of a joint NASA/FAA project to investigate the performance of transport aircraft under realistic crash conditions. In June 2017, a vertical drop test was conducted of a wing-box fuselage section of the same aircraft. Both sections were configured with two rows of aircraft seats, in a triple-double configuration. A total of ten Anthropomorphic Test Devices (ATDs) were secured in seats using standard lap belt restraints. The forward fuselage section was also configured with luggage in the cargo hold. Both sections were outfitted with two hat racks, each with added ballast mass. The drop tests were performed at the Landing and Impact Research facility located at NASA Langley Research Center in Hampton, Virginia. The measured impact velocity for the forward fuselage section was 346.8-in/s onto soil. The wing-box section was dropped with a downward facing pitch angle onto a sloping soil surface in order to create an induced forward acceleration in the airframe. The vertical impact velocity of the wing-box section was 349.2-in/s. A second objective of this project was to assess the capabilities of finite element simulations to predict the test responses. Finite element models of both fuselage sections were developed for execution in LS-DYNA(Registered Trademark), a commercial explicit nonlinear transient dynamic code. The models contained accurate representations of the airframe structure, the hat racks and hat rack masses, the floor and seat tracks, the luggage in the cargo hold for the forward section, and the detailed under-floor structure in the wing-box section. Initially, concentrated masses were used to represent the inertial properties of the seats, restraints, and ATD occupants. However, later simulations were performed that included finite element representations of the seats, restraints, and ATD occupants. These models were developed to more

  2. Flight Investigation to Determine the Effect of Jet Exhaust on Drag, Trim Characteristics, and Afterbody Pressures of a 0.125-Scale Rocket Model of the Mcdonnell F-101A Airplane

    Kennedy, Thomas L.

    1956-01-01

    A flight investigation was conducted to determine the effect of jet exhaust on the drag, trim characteristics, and afterbody pressures on a 0.125-scale rocket model of the McDonnell F-101A airplance. Power-off data were obtained over a Mach number range of 1.04 to 1.9 and power-on data were obtained at a Mach number of about 1.5. The data indicated that with power-on the change in external drag coefficient was within the data accuracy and there was a decrease in trim angle of attack of 1.27 degrees with a corresponding decrease of 0.07 in lift coefficient. Correspondingly, pressure coefficients on the side and bottom of the fuselage indicated a positive increment near the jet exit. As the distance downstream of the jet exit increased, the increment on the bottom of the fuselage increased, whereas the increments on the side decreased to a negative peak.

  3. The Counterproductive Effects of Helicopter Universities

    Von Bergen, C. W.; Bressler, Martin S.

    2017-01-01

    Perhaps universities have gone too far in their attempts to provide the best learning experience for our students? We have heard of helicopter parents who hover over their sons and daughters, removing all obstacles their student might face and solve problems for them. Have colleges and universities adopted this same kind of behavior in their…

  4. Helicopter Parents Can Be a Good Thing

    Hiltz, Julie

    2015-01-01

    Helicopter parents get a bad rap. Teachers and administrators should view them as a resource--not a nuisance. By encouraging open communication, teachers can begin to understand the motivations of these parents and find creative ways to connect them with opportunities to promote their students' academic success and the school's overall…

  5. Helicopter Parents Help Students, Survey Finds

    Lipka, Sara

    2007-01-01

    Helicopter parents, notorious for hovering over their college-age children, may actually help students thrive, according to this year's National Survey of Student Engagement. Students whose parents intervene on their behalf--38 percent of freshmen and 29 percent of seniors--are more active in and satisfied with college, says the monstrous annual…

  6. Feasibility of Helicopter Support Seek Frost.

    1980-05-01

    the allowable maximum weight can be used as the payload. The payload is a variable. Small helicopters with full fuel and auxillary tanks can fly...equipment, that the program to obtain icing approval on the S-76 will be finalized for management evaluation, and a decision can be made at that time to

  7. Performance Measurement in Helicopter Training and Operations.

    Prophet, Wallace W.

    For almost 15 years, HumRRO Division No. 6 has conducted an active research program on techniques for measuring the flight performance of helicopter trainees and pilots. This program addressed both the elemental aspects of flying (i.e., maneuvers) and the mission- or goal-oriented aspects. A variety of approaches has been investigated, with the…

  8. Helicopter noise footprint prediction in unsteady maneuvers

    Gennaretti, Massimo; Bernardini, Giovanni; Serafini, Jacopo; Anobile, A.; Hartjes, S.

    2017-01-01

    This paper investigates different methodologies for the evaluation of the acoustic disturbance emitted by helicopter’s main rotors during unsteady maneuvers. Nowadays, the simulation of noise emitted by helicopters is of great interest to designers, both for the assessment of the acoustic impact

  9. Multicenter observational prehospital resuscitation on helicopter study.

    Holcomb, John B; Swartz, Michael D; DeSantis, Stacia M; Greene, Thomas J; Fox, Erin E; Stein, Deborah M; Bulger, Eileen M; Kerby, Jeffrey D; Goodman, Michael; Schreiber, Martin A; Zielinski, Martin D; O'Keeffe, Terence; Inaba, Kenji; Tomasek, Jeffrey S; Podbielski, Jeanette M; Appana, Savitri N; Yi, Misung; Wade, Charles E

    2017-07-01

    Earlier use of in-hospital plasma, platelets, and red blood cells (RBCs) has improved survival in trauma patients with severe hemorrhage. Retrospective studies have associated improved early survival with prehospital blood product transfusion (PHT). We hypothesized that PHT of plasma and/or RBCs would result in improved survival after injury in patients transported by helicopter. Adult trauma patients transported by helicopter from the scene to nine Level 1 trauma centers were prospectively observed from January to November 2015. Five helicopter systems had plasma and/or RBCs, whereas the other four helicopter systems used only crystalloid resuscitation. All patients meeting predetermined high-risk criteria were analyzed. Patients receiving PHT were compared with patients not receiving PHT. Our primary analysis compared mortality at 3 hours, 24 hours, and 30 days, using logistic regression to adjust for confounders and site heterogeneity to model patients who were matched on propensity scores. Twenty-five thousand one hundred eighteen trauma patients were admitted, 2,341 (9%) were transported by helicopter, of which 1,058 (45%) met the highest-risk criteria. Five hundred eighty-five of 1,058 patients were flown on helicopters carrying blood products. In the systems with blood available, prehospital median systolic blood pressure (125 vs 128) and Glasgow Coma Scale (7 vs 14) was significantly lower, whereas median Injury Severity Score was significantly higher (21 vs 14). Unadjusted mortality was significantly higher in the systems with blood products available, at 3 hours (8.4% vs 3.6%), 24 hours (12.6% vs 8.9%), and 30 days (19.3% vs 13.3%). Twenty-four percent of eligible patients received a PHT. A median of 1 unit of RBCs and plasma were transfused prehospital. Of patients receiving PHT, 24% received only plasma, 7% received only RBCs, and 69% received both. In the propensity score matching analysis (n = 109), PHT was not significantly associated with mortality

  10. Fuel Savings and Aerodynamic Drag Reduction from Rail Car Covers

    Storms, Bruce; Salari, Kambiz; Babb, Alex

    2008-01-01

    The potential for energy savings by reducing the aerodynamic drag of rail cars is significant. A previous study of aerodynamic drag of coal cars suggests that a 25% reduction in drag of empty cars would correspond to a 5% fuel savings for a round trip [1]. Rail statistics for the United States [2] report that approximately 5.7 billion liters of diesel fuel were consumed for coal transportation in 2002, so a 5% fuel savings would total 284 million liters. This corresponds to 2% of Class I railroad fuel consumption nationwide. As part of a DOE-sponsored study, the aerodynamic drag of scale rail cars was measured in a wind tunnel. The goal of the study was to measure the drag reduction of various rail-car cover designs. The cover designs tested yielded an average drag reduction of 43% relative to empty cars corresponding to an estimated round-trip fuel savings of 9%.

  11. Engineering drag currents in Coulomb coupled quantum dots

    Lim, Jong Soo; Sánchez, David; López, Rosa

    2018-02-01

    The Coulomb drag phenomenon in a Coulomb-coupled double quantum dot system is revisited with a simple model that highlights the importance of simultaneous tunneling of electrons. Previously, cotunneling effects on the drag current in mesoscopic setups have been reported both theoretically and experimentally. However, in both cases the sequential tunneling contribution to the drag current was always present unless the drag level position were too far away from resonance. Here, we consider the case of very large Coulomb interaction between the dots, whereby the drag current needs to be assisted by cotunneling events. As a consequence, a quantum coherent drag effect takes place. Further, we demonstrate that by properly engineering the tunneling probabilities using band tailoring it is possible to control the sign of the drag and drive currents, allowing them to flow in parallel or antiparallel directions. We also show that the drag current can be manipulated by varying the drag gate potential and is thus governed by electron- or hole-like transport.

  12. Drag reduction through self-texturing compliant bionic materials

    Eryong Liu; Longyang Li; Gang Wang; Zhixiang Zeng; Wenjie Zhao; Qunji Xue

    2017-01-01

    Compliant fish skin is effectively in reducing drag, thus the design and application of compliant bionic materials may be a good choice for drag reduction. Here we consider the drag reduction of compliant bionic materials. First, ZnO and PDMS mesh modified with n-octadecane were prepared, the drag reduction of self-texturing compliant n-octadecane were studied. The results show that the mesh modified by ZnO and PDMS possess excellent lipophilic and hydrophobic, thus n-octadecane at solid, sem...

  13. On the origin of the drag force on golf balls

    Balaras, Elias; Beratlis, Nikolaos; Squires, Kyle

    2017-11-01

    It is well establised that dimples accelerate the drag-crisis on a sphere. The result of the early drag-crisis is a reduction of the drag coefficient by more than a factor of two when compared to a smooth sphere at the same Reynolds number. However, when the drag coefficients for smooth and dimpled spheres in the supercritical regime are compared, the latter is higher by a factor of two to three. To understand the origin of this behavior we conducted direct numerical simulations of the flow around a dimpled sphere, which is similar to commercially available golf balls, in the supercritical regime. By comparing the results to those for a smooth sphere it is found that dimples, although effective in accelerating the drag crisis, impose a local drag-penalty, which contributes significantly to the overall drag force. This finding challenges the broadly accepted view, that the dimples only indirectly affect the drag force on a golf ball by manipulating the structure of the turbulent boundary layer near the wall and consequently affect global separation. Within this view, typically the penalty on the drag force imposed by the dimples is assumed to be small and coming primarily from skin friction. The direct numerical simulations we will report reveal a very different picture.

  14. Drag Reduction Through Distributed Electric Propulsion

    Stoll, Alex M.; Bevirt, JoeBen; Moore, Mark D.; Fredericks, William J.; Borer, Nicholas K.

    2014-01-01

    One promising application of recent advances in electric aircraft propulsion technologies is a blown wing realized through the placement of a number of electric motors driving individual tractor propellers spaced along each wing. This configuration increases the maximum lift coefficient by providing substantially increased dynamic pressure across the wing at low speeds. This allows for a wing sized near the ideal area for maximum range at cruise conditions, imparting the cruise drag and ride quality benefits of this smaller wing size without decreasing takeoff and landing performance. A reference four-seat general aviation aircraft was chosen as an exemplary application case. Idealized momentum theory relations were derived to investigate tradeoffs in various design variables. Navier-Stokes aeropropulsive simulations were performed with various wing and propeller configurations at takeoff and landing conditions to provide insight into the effect of different wing and propeller designs on the realizable effective maximum lift coefficient. Similar analyses were performed at the cruise condition to ensure that drag targets are attainable. Results indicate that this configuration shows great promise to drastically improve the efficiency of small aircraft.

  15. Effects of Increasing Drag on Conjunction Assessment

    Frigm, Ryan Clayton; McKinley, David P.

    2010-01-01

    Conjunction Assessment Risk Analysis relies heavily on the computation of the Probability of Collision (Pc) and the understanding of the sensitivity of this calculation to the position errors as defined by the covariance. In Low Earth Orbit (LEO), covariance is predominantly driven by perturbations due to atmospheric drag. This paper describes the effects of increasing atmospheric drag through Solar Cycle 24 on Pc calculations. The process of determining these effects is found through analyzing solar flux predictions on Energy Dissipation Rate (EDR), historical relationship between EDR and covariance, and the sensitivity of Pc to covariance. It is discovered that while all LEO satellites will be affected by the increase in solar activity, the relative effect is more significant in the LEO regime around 700 kilometers in altitude compared to 400 kilometers. Furthermore, it is shown that higher Pc values can be expected at larger close approach miss distances. Understanding these counter-intuitive results is important to setting Owner/Operator expectations concerning conjunctions as solar maximum approaches.

  16. Helicopter Control Energy Reduction Using Moving Horizontal Tail

    Oktay, Tugrul; Sal, Firat

    2015-01-01

    Helicopter moving horizontal tail (i.e., MHT) strategy is applied in order to save helicopter flight control system (i.e., FCS) energy. For this intention complex, physics-based, control-oriented nonlinear helicopter models are used. Equations of MHT are integrated into these models and they are together linearized around straight level flight condition. A specific variance constrained control strategy, namely, output variance constrained Control (i.e., OVC) is utilized for helicopter FCS. Control energy savings due to this MHT idea with respect to a conventional helicopter are calculated. Parameters of helicopter FCS and dimensions of MHT are simultaneously optimized using a stochastic optimization method, namely, simultaneous perturbation stochastic approximation (i.e., SPSA). In order to observe improvement in behaviors of classical controls closed loop analyses are done. PMID:26180841

  17. Helicopter Control Energy Reduction Using Moving Horizontal Tail

    Tugrul Oktay

    2015-01-01

    Full Text Available Helicopter moving horizontal tail (i.e., MHT strategy is applied in order to save helicopter flight control system (i.e., FCS energy. For this intention complex, physics-based, control-oriented nonlinear helicopter models are used. Equations of MHT are integrated into these models and they are together linearized around straight level flight condition. A specific variance constrained control strategy, namely, output variance constrained Control (i.e., OVC is utilized for helicopter FCS. Control energy savings due to this MHT idea with respect to a conventional helicopter are calculated. Parameters of helicopter FCS and dimensions of MHT are simultaneously optimized using a stochastic optimization method, namely, simultaneous perturbation stochastic approximation (i.e., SPSA. In order to observe improvement in behaviors of classical controls closed loop analyses are done.

  18. Drop test and crash simulation of a civil airplane fuselage section

    Liu Xiaochuan

    2015-04-01

    Full Text Available Crashworthiness of a civil airplane fuselage section was studied in this paper. Firstly, the failure criterion of a rivet was studied by test, showing that the ultimate tension and shear failure loads were obviously affected by the loading speed. The relations between the loading speed and the average ultimate shear, tension loads were expressed by two logarithmic functions. Then, a vertical drop test of a civil airplane fuselage section was conducted with an actual impact velocity of 6.85 m/s, meanwhile the deformation of cabin frame and the accelerations at typical locations were measured. The finite element model of a main fuselage structure was developed and validated by modal test, and the error between the calculated frequencies and the test ones of the first four modes were less than 5%. Numerical simulation of the drop test was performed by using the LS-DYNA code and the simulation results show a good agreement with that of drop test. Deforming mode of the analysis was the same as the drop test; the maximum average rigid acceleration in test was 8.81g while the calculated one was 9.17g, with an error of 4.1%; average maximum test deformation at four points on the front cabin floor was 420 mm, while the calculated one was 406 mm, with an error of 3.2%; the peak value of the calculated acceleration at a typical location was 14.72g, which is lower than the test result by 5.46%; the calculated rebound velocity result was greater than the test result 17.8% and energy absorption duration was longer than the test result by 5.73%.

  19. Preliminary Analysis of Helicopter Options to Support Tunisian Counterterrorism Operations

    2016-04-27

    helicopters from Sikorsky to fulfill a number of roles in counterterrorism operations. Rising costs and delays in delivery raised the question of...whether other cost-effective options exist to meet Tunisia’s helicopter requirement. Approach Our team conducted a preliminary assessment of...alternative helicopters for counterterrorism air assault missions. Any decision to acquire an aircraft must consider many factors, including technical

  20. Swing Damping for Helicopter Slung Load Systems using Delayed Feedback

    Bisgaard, Morten; la Cour-Harbo, Anders; Bendtsen, Jan Dimon

    2009-01-01

    This paper presents the design and verification of a swing reducing controller for helicopter slung load systems usingintentional delayed feedback. It is intended for augmenting a trajectory tracking helicopter controller and thereby improving the slung load handing capabilities for autonomous helicopters. The delayed feedback controller is added to actively reduce oscillations of the slung load by improving the damping of the slung load pendulum modes. Furthermore, it is intended for integra...

  1. An anthropometric analysis of Korean male helicopter pilots for helicopter cockpit design.

    Lee, Wonsup; Jung, Kihyo; Jeong, Jeongrim; Park, Jangwoon; Cho, Jayoung; Kim, Heeeun; Park, Seikwon; You, Heecheon

    2013-01-01

    This study measured 21 anthropometric dimensions (ADs) of 94 Korean male helicopter pilots in their 20s to 40s and compared them with corresponding measurements of Korean male civilians and the US Army male personnel. The ADs and the sample size of the anthropometric survey were determined by a four-step process: (1) selection of ADs related to helicopter cockpit design, (2) evaluation of the importance of each AD, (3) calculation of required sample sizes for selected precision levels and (4) determination of an appropriate sample size by considering both the AD importance evaluation results and the sample size requirements. The anthropometric comparison reveals that the Korean helicopter pilots are larger (ratio of means = 1.01-1.08) and less dispersed (ratio of standard deviations = 0.71-0.93) than the Korean male civilians and that they are shorter in stature (0.99), have shorter upper limbs (0.89-0.96) and lower limbs (0.93-0.97), but are taller on sitting height, sitting eye height and acromial height (1.01-1.03), and less dispersed (0.68-0.97) than the US Army personnel. The anthropometric characteristics of Korean male helicopter pilots were compared with those of Korean male civilians and US Army male personnel. The sample size determination process and the anthropometric comparison results presented in this study are useful to design an anthropometric survey and a helicopter cockpit layout, respectively.

  2. London 2012 Paralympic swimming: passive drag and the classification system.

    Oh, Yim-Taek; Burkett, Brendan; Osborough, Conor; Formosa, Danielle; Payton, Carl

    2013-09-01

    The key difference between the Olympic and Paralympic Games is the use of classification systems within Paralympic sports to provide a fair competition for athletes with a range of physical disabilities. In 2009, the International Paralympic Committee mandated the development of new, evidence-based classification systems. This study aims to assess objectively the swimming classification system by determining the relationship between passive drag and level of swimming-specific impairment, as defined by the current swimming class. Data were collected on participants at the London 2012 Paralympic Games. The passive drag force of 113 swimmers (classes 3-14) was measured using an electro-mechanical towing device and load cell. Swimmers were towed on the surface of a swimming pool at 1.5 m/s while holding their most streamlined position. Passive drag ranged from 24.9 to 82.8 N; the normalised drag (drag/mass) ranged from 0.45 to 1.86 N/kg. Significant negative associations were found between drag and the swimming class (τ = -0.41, p < 0.01) and normalised drag and the swimming class (τ = -0.60, p < 0.01). The mean difference in drag between adjacent classes was inconsistent, ranging from 0 N (6 vs 7) to 11.9 N (5 vs 6). Reciprocal Ponderal Index (a measure of slenderness) correlated moderately with normalised drag (r(P) = -0.40, p < 0.01). Although swimmers with the lowest swimming class experienced the highest passive drag and vice versa, the inconsistent difference in mean passive drag between adjacent classes indicates that the current classification system does not always differentiate clearly between swimming groups.

  3. Automatic guidance and control laws for helicopter obstacle avoidance

    Cheng, Victor H. L.; Lam, T.

    1992-01-01

    The authors describe the implementation of a full-function guidance and control system for automatic obstacle avoidance in helicopter nap-of-the-earth (NOE) flight. The guidance function assumes that the helicopter is sufficiently responsive so that the flight path can be readily adjusted at NOE speeds. The controller, basically an autopilot for following the derived flight path, was implemented with parameter values to control a generic helicopter model used in the simulation. Evaluation of the guidance and control system with a 3-dimensional graphical helicopter simulation suggests that the guidance has the potential for providing good and meaningful flight trajectories.

  4. Pilot ejection, parachute, and helicopter crash injuries.

    McBratney, Colleen M; Rush, Stephen; Kharod, Chetan U

    2014-01-01

    USAF Pararescuemen (PJs) respond to downed aircrew as a fundamental mission for personnel recovery (PR), one of the Air Force's core functions. In addition to responding to these in Military settings, the PJs from the 212 Rescue Squadron routinely respond to small plane crashes in remote regions of Alaska. While there is a paucity of information on the latter, there have been articles detailing injuries sustained from helicopter crashes and while ejecting or parachuting from fixed wing aircraft. The following represents a new chapter added to the Pararescue Medical Operations Handbook, Sixth Edition (2014, editors Matt Wolf, MD, and Stephen Rush, MD, in press). It was designed to be a quick reference for PJs and their Special Operations flight surgeons to help with understanding of mechanism of injury with regard to pilot ejection, parachute, and helicopter accident injuries. It outlines the nature of the injuries sustained in such mishaps and provides an epidemiologic framework from which to approach the problem. 2014.

  5. NASA/FAA helicopter simulator workshop

    Larsen, William E. (Editor); Randle, Robert J., Jr. (Editor); Bray, Richard S. (Editor); Zuk, John (Editor)

    1992-01-01

    A workshop was convened by the FAA and NASA for the purpose of providing a forum at which leading designers, manufacturers, and users of helicopter simulators could initiate and participate in a development process that would facilitate the formulation of qualification standards by the regulatory agency. Formal papers were presented, special topics were discussed in breakout sessions, and a draft FAA advisory circular defining specifications for helicopter simulators was presented and discussed. A working group of volunteers was formed to work with the National Simulator Program Office to develop a final version of the circular. The workshop attracted 90 individuals from a constituency of simulator manufacturers, training organizations, the military, civil regulators, research scientists, and five foreign countries.

  6. Autonomous vertical autorotation for unmanned helicopters

    Dalamagkidis, Konstantinos

    Small Unmanned Aircraft Systems (UAS) are considered the stepping stone for the integration of civil unmanned vehicles in the National Airspace System (NAS) because of their low cost and risk. Such systems are aimed at a variety of applications including search and rescue, surveillance, communications, traffic monitoring and inspection of buildings, power lines and bridges. Amidst these systems, small helicopters play an important role because of their capability to hold a position, to maneuver in tight spaces and to take off and land from virtually anywhere. Nevertheless civil adoption of such systems is minimal, mostly because of regulatory problems that in turn are due to safety concerns. This dissertation examines the risk to safety imposed by UAS in general and small helicopters in particular, focusing on accidents resulting in a ground impact. To improve the performance of small helicopters in this area, the use of autonomous autorotation is proposed. This research goes beyond previous work in the area of autonomous autorotation by developing an on-line, model-based, real-time controller that is capable of handling constraints and different cost functions. The approach selected is based on a non-linear model-predictive controller, that is augmented by a neural network to improve the speed of the non-linear optimization. The immediate benefit of this controller is that a class of failures that would otherwise result in an uncontrolled crash and possible injuries or fatalities can now be accommodated. Furthermore besides simply landing the helicopter, the controller is also capable of minimizing the risk of serious injury to people in the area. This is accomplished by minimizing the kinetic energy during the last phase of the descent. The presented research is designed to benefit the entire UAS community as well as the public, by allowing for safer UAS operations, which in turn also allow faster and less expensive integration of UAS in the NAS.

  7. Helicopter Aircrew Training Using Fused Reality

    2006-06-01

    PROCESS Blue screening involving human filming usually employs a blue or green backdrop, since skin contains little blue or green hue. These backdrops...Helicopter Aircrew Training Using Fused Reality 27 - 10 RTO-MP-HFM-136 a. b. c. d. e. f. Figure 13: Frames Showing Physical Object ( witch ... filming . However, when a user’s hands disrupt the light from a helmet-mounted light source, the shadows cast onto the distant background are diffuse and

  8. Learning Basic Mechatronics through Helicopter Workshop

    Adzly Anuar; Maryam Huda Ahmad Phesal; Azrul Abidin Zakaria; Goh Chin Hock; Sivadass Thiruchelvam; Dickson Neoh Tze How; Muhammad Fahmi Abdul Ghani; Khairul Salleh Mohamed Sahari

    2014-01-01

    In recent years, technologies related to mechatronics and robotics is available even to elementary level students. It is now common to see schools in Malaysia using Lego Mindstorm as a tool for active learning on mechatronics and robotics. A new yet interesting way of learning mechatronics and robotics is introduced by Dr. Dan Barry, a former astronaut and his son Andrew Barry during their visit to Malaysia. The kits used are based on a 4-channel RC helicopter, Arduino Uno microcontroller, IR...

  9. High-integrity databases for helicopter operations

    Pschierer, Christian; Schiefele, Jens; Lüthy, Juerg

    2009-05-01

    Helicopter Emergency Medical Service missions (HEMS) impose a high workload on pilots due to short preparation time, operations in low level flight, and landings in unknown areas. The research project PILAS, a cooperation between Eurocopter, Diehl Avionics, DLR, EADS, Euro Telematik, ESG, Jeppesen, the Universities of Darmstadt and Munich, and funded by the German government, approached this problem by researching a pilot assistance system which supports the pilots during all phases of flight. The databases required for the specified helicopter missions include different types of topological and cultural data for graphical display on the SVS system, AMDB data for operations at airports and helipads, and navigation data for IFR segments. The most critical databases for the PILAS system however are highly accurate terrain and obstacle data. While RTCA DO-276 specifies high accuracies and integrities only for the areas around airports, HEMS helicopters typically operate outside of these controlled areas and thus require highly reliable terrain and obstacle data for their designated response areas. This data has been generated by a LIDAR scan of the specified test region. Obstacles have been extracted into a vector format. This paper includes a short overview of the complete PILAS system and then focus on the generation of the required high quality databases.

  10. Reynolds number dependence of drag reduction by rodlike polymers

    Amarouchene, Y.; Bonn, D.; Kellay, H.; Lo, T.-S.; L'vov, V.S.; Procaccia, I.

    2008-01-01

    We present experimental and theoretical results addressing the Reynolds number (Re) dependence of drag reduction by sufficiently large concentrations of rodlike polymers in turbulent wall-bounded flows. It is shown that when Re is small the drag is enhanced. On the other hand, when Re increases, the

  11. Determination of the Drag Resistance Coefficients of Different Vehicles

    Fahsl, Christoph; Vogt, Patrik

    2018-01-01

    While it has been demonstrated how air resistance could be analyzed by using mobile devices, this paper demonstrates a method of how to determine the drag resistance coefficient "c" of a commercial automobile by using the acceleration sensor of a smartphone or tablet. In an academic context, the drag resistance is often mentioned, but…

  12. Drag reduction through self-texturing compliant bionic materials

    Liu, Eryong; Li, Longyang; Wang, Gang; Zeng, Zhixiang; Zhao, Wenjie; Xue, Qunji

    2017-01-01

    Compliant fish skin is effectively in reducing drag, thus the design and application of compliant bionic materials may be a good choice for drag reduction. Here we consider the drag reduction of compliant bionic materials. First, ZnO and PDMS mesh modified with n-octadecane were prepared, the drag reduction of self-texturing compliant n-octadecane were studied. The results show that the mesh modified by ZnO and PDMS possess excellent lipophilic and hydrophobic, thus n-octadecane at solid, semisolid and liquid state all have good adhesion with modified mesh. The states of n-octadecane changed with temperature, thus, the surface contact angle and adhesive force all varies obviously at different state. The contact angle decreases with temperature, the adhesive force shows a lower value at semisolid state. Furthermore, the drag testing results show that the compliant n-octadecane film is more effectively in drag reduction than superhydrophobic ZnO/PDMS film, indicating that the drag reduction mechanism of n-octadecane is significantly different with superhydrophobic film. Further research shows that the water flow leads to self-texturing of semisolid state n-octadecane, which is similar with compliant fish skin. Therefore, the compliant bionic materials of semisolid state n-octadecane with regular bulge plays a major role in the drag reduction.

  13. EFFECTIVENESS OF NYLON DRAG STRAPS FOR BRAKING MONORAIL SLEDS.

    Velocity versus coast distance measurements on two monorail rocket sleds were conducted on the Holloman track to obtain numerical information on the...sleds and the drag straps. The straps as described are shown to increase the effective drag area of the monorail sleds used by approximately one square

  14. Spin-transfer mechanism for magnon-drag thermopower

    Lucassen, M.E.|info:eu-repo/dai/nl/314406913; Wong, C.H.; Duine, R.A.|info:eu-repo/dai/nl/304830127; Tserkovnyak, Y.

    2011-01-01

    We point out a relation between the dissipative spin-transfer-torque parameter β and the contribution of magnon drag to the thermoelectric power in conducting ferromagnets. Using this result, we estimate β in iron at low temperatures, where magnon drag is believed to be the dominant contribution to

  15. Analysis of Drag Reduction Methods and Mechanisms of Turbulent

    Gu Yunqing

    2017-01-01

    Full Text Available Turbulent flow is a difficult issue in fluid dynamics, the rules of which have not been totally revealed up to now. Fluid in turbulent state will result in a greater frictional force, which must consume great energy. Therefore, it is not only an important influence in saving energy and improving energy utilization rate but also an extensive application prospect in many fields, such as ship domain and aerospace. Firstly, bionic drag reduction technology is reviewed and is a hot research issue now, the drag reduction mechanism of body surface structure is analyzed, such as sharks, earthworms, and dolphins. Besides, we make a thorough study of drag reduction characteristics and mechanisms of microgrooved surface and compliant wall. Then, the relevant drag reduction technologies and mechanisms are discussed, focusing on the microbubbles, the vibrant flexible wall, the coating, the polymer drag reduction additives, superhydrophobic surface, jet surface, traveling wave surface drag reduction, and the composite drag reduction methods. Finally, applications and advancements of the drag reduction technology in turbulence are prospected.

  16. Frictional drag between quantum wells mediated by phonon exchange

    Bønsager, M.C.; Flensberg, Karsten; Hu, Ben Yu-Kuang

    1998-01-01

    We use the Kubo formalism to evaluate the contribution of acoustic-phonon exchange to the frictional drag between nearby two-dimensional electron systems. In the case of free phonons, we find a divergent drag rate (tau(D)(-l)). However, tau(D)(-l) becomes finite when phonon scattering from either...

  17. Vibroacoustic Tailoring of a Rod-Stiffened Composite Fuselage Panel with Multidisciplinary Considerations

    Allen, Albert R.; Przekop, Adam

    2015-01-01

    An efficient multi-objective design tailoring procedure seeking to improve the vibroacoustic performance of a fuselage panel while maintaining or reducing weight is presented. The structure considered is the pultruded rod stitched efficient unitized structure, a highly integrated composite structure concept designed for a noncylindrical, next-generation flight vehicle fuselage. Modifications to a baseline design are evaluated within a six-parameter design space including spacing, flange width, and web height for both frame and stringer substructure components. The change in sound power radiation attributed to a design change is predicted using finite-element models sized and meshed for analyses in the 500 Hz, 1 kHz, and 2 kHz octave bands. Three design studies are carried out in parallel while considering a diffuse acoustic field excitation and two types of turbulent boundary-layer excitation. Kriging surrogate models are used to reduce the computational costs of resolving the vibroacoustic and weight objective Pareto fronts. The resulting Pareto optimal designs are then evaluated under a static pressurization ultimate load to assess structural strength and stability. Results suggest that choosing alternative configurations within the considered design space can reduce weight and improve vibroacoustic performance without compromising strength and stability of the structure under the static load condition considered, but the tradeoffs are significantly influenced by the spatial characteristics of the assumed excitation field.

  18. A study of the structural-acoustic response and interior noise levels of fuselage structures

    Koval, L. R.

    1978-01-01

    Models of both flat and curved fuselage panels were tested for their sound transmission characteristics. The effect of external air flow on transmission loss was simulated in a subsonic wind-tunnel. By numerically evaluating the known equations for field-incidence transmission loss of single-walled panels in a computer program, a comparison of the theory with the test results was made. As a further extension to aircraft fuselage simulation, equations for the field-incidence transmission loss of a double-walled panel were derived. Flow is shown to provide a small increase in transmission loss for a flat panel. Curvature is shown to increase transmission loss for low frequencies, while also providing a sharp decrease in transmission loss at the ring frequency of the cylindrical panel. The field-incidence transmission loss of a double-walled panel was found to be approximately twice that for a single-walled panel, with the addition of dips in the transmission loss at the air gap resonances and at the critical frequency of the internal panel.

  19. Dancing droplets: Contact angle, drag, and confinement

    Benusiglio, Adrien; Cira, Nate; Prakash, Manu

    2015-11-01

    When deposited on a clean glass slide, a mixture of water and propylene glycol forms a droplet of given contact angle, when both pure liquids spread. (Cira, Benusiglio, Prakash: Nature, 2015). The droplet is stabilized by a gradient of surface tension due to evaporation that induces a Marangoni flow from the border to the apex of the droplets. The apparent contact angle of the droplets depends on both their composition and the external humidity as captured by simple models. These droplets present remarkable properties such as lack of a large pinning force. We discuss the drag on these droplets as a function of various parameters. We show theoretical and experimental results of how various confinement geometries change the vapor gradient and the dynamics of droplet attraction.

  20. Analytical Ballistic Trajectories with Approximately Linear Drag

    Giliam J. P. de Carpentier

    2014-01-01

    Full Text Available This paper introduces a practical analytical approximation of projectile trajectories in 2D and 3D roughly based on a linear drag model and explores a variety of different planning algorithms for these trajectories. Although the trajectories are only approximate, they still capture many of the characteristics of a real projectile in free fall under the influence of an invariant wind, gravitational pull, and terminal velocity, while the required math for these trajectories and planners is still simple enough to efficiently run on almost all modern hardware devices. Together, these properties make the proposed approach particularly useful for real-time applications where accuracy and performance need to be carefully balanced, such as in computer games.

  1. Future Drag Measurements from Venus Express

    Keating, Gerald; Mueller-Wodarg, Ingo; Forbes, Jeffrey M.; Yelle, Roger; Bruinsma, Sean; Withers, Paul; Lopez-Valverde, Miguel Angel; Theriot, Res. Assoc. Michael; Bougher, Stephen

    Beginning in July 2008 during the Venus Express Extended Mission, the European Space Agency will dramatically drop orbital periapsis from near 250km to near 180km above the Venus North Polar Region. This will allow orbital decay measurements of atmospheric densities to be made near the Venus North Pole by the VExADE (Venus Express Atmospheric Drag Experiment) whose team leader is Ingo Mueller-Wodarg. VExADE consists of two parts VExADE-ODA (Orbital Drag Analysis from radio tracking data) and VExADE-ACC (Accelerometer in situ atmospheric density measurements). Previous orbital decay measurements of the Venus thermosphere were obtained by Pioneer Venus from the 1970's into the 1990's and from Magellan in the 1990's. The major difference is that the Venus Express will provide measurements in the North Polar Region on the day and night sides, while the earlier measurements were obtained primarily near the equator. The periapsis will drift upwards in altitude similar to the earlier spacecraft and then be commanded down to its lower original values. This cycle in altitude will allow estimates of vertical structure and thus thermospheric temperatures in addition to atmospheric densities. The periapsis may eventually be lowered even further so that accelerometers can more accurately obtain density measurements of the polar atmosphere as a function of altitude, latitude, longitude, local solar time, pressure, Ls, solar activity, and solar wind on each pass. Bias in accelerometer measurements will be determined and corrected for by accelerometer measurements obtained above the discernable atmosphere on each pass. The second experiment, VExADE-ACC, is similar to the accelerometer experiments aboard Mars Global Surveyor, Mars Odyssey, and Mars Reconnaissance Orbiter that carried similar accelerometers in orbit around Mars. The risk involved in the orbital decay and accelerometer measurements is minimal. We have not lost any spacecraft orbiting Venus or Mars due to unexpected

  2. Friction and drag forces on spheres propagating down inclined planes

    Tee, Yi Hui; Longmire, Ellen

    2017-11-01

    When a submerged sphere propagates along an inclined wall at terminal velocity, it experiences gravity, drag, lift, and friction forces. In the related equations of motion, the drag, lift and friction coefficients are unknown. Experiments are conducted to determine the friction and drag coefficients of the sphere over a range of Reynolds numbers. Through high speed imaging, translational and rotational velocities of spheres propagating along a glass plate are determined in liquids with several viscosities. The onset of sliding motion is identified by computing the dimensionless rotation rate of the sphere. Using drag and lift coefficients for Re friction coefficients are calculated for several materials. The friction coefficients are then employed to estimate the drag coefficient for 350 frictional force over this Re range. Supported by NSF (CBET-1510154).

  3. Airflow in Gravity Sewers - Determination of Wastewater Drag Coefficient.

    Bentzen, Thomas Ruby; Østertoft, Kristian Kilsgaard; Vollertsen, Jes; Fuglsang, Emil Dietz; Nielsen, Asbjørn Haaning

    2016-03-01

    Several experiments have been conducted in order to improve the understanding of the wastewater drag and the wall frictional force acting on the headspace air in gravity sewers. The aim of the study is to improve the data basis for a numerical model of natural sewer ventilation. The results of the study shows that by integrating the top/side wall shear stresses the log-law models for the air velocity distribution along the unwetted perimeter resulted in a good agreement with the friction forces calculated by use of the Colebrook-White formula for hydraulic smooth pipes. Secondly, the water surface drags were found by log-law models of the velocity distribution in turbulent flows to fit velocity profiles measured from the water surface and by integrating the water surface drags along the wetted perimeter, mean water surface drags were found and a measure of the water surface drag coefficient was found.

  4. Electron drag in ferromagnetic structures separated by an insulating interface

    Kozub, V. I.; Muradov, M. I.; Galperin, Y. M.

    2018-06-01

    We consider electron drag in a system of two ferromagnetic layers separated by an insulating interface. The source of it is expected to be magnon-electron interactions. Namely, we assume that the external voltage is applied to the "active" layer stimulating electric current through this layer. In its turn, the scattering of the current-carrying electrons by magnons leads to a magnon drag current within this layer. The 3-magnons interactions between magnons in the two layers (being of non-local nature) lead to magnon drag within the "passive" layer which, correspondingly, produce electron drag current via processes of magnon-electron scattering. We estimate the drag current and compare it to the phonon-induced one.

  5. Experimental evaluation of the drag force and drag torque acting on a rotating spherical particle moving in fluid

    Lukerchenko, Nikolay; Kvurt, Y.; Kharlamov, Alexander; Chára, Zdeněk; Vlasák, Pavel

    2008-01-01

    Roč. 56, č. 2 (2008), s. 88-94 ISSN 0042-790X R&D Projects: GA AV ČR IAA200600603 Institutional research plan: CEZ:AV0Z20600510 Keywords : drag force * drag torque * spherical particle * rotational movement * translational movement Subject RIV: DA - Hydrology ; Limnology

  6. Bubble-induced skin-friction drag reduction and the abrupt transition to air-layer drag reduction

    Elbing, Brian R.; Winkel, Eric S.; Lay, Keary A.; Ceccio, Steven L.; Dowling, David R.; Perlin, Marc

    To investigate the phenomena of skin-friction drag reduction in a turbulent boundary layer (TBL) at large scales and high Reynolds numbers, a set of experiments has been conducted at the US Navy's William B. Morgan Large Cavitation Channel (LCC). Drag reduction was achieved by injecting gas (air) from a line source through the wall of a nearly zero-pressure-gradient TBL that formed on a flat-plate test model that was either hydraulically smooth or fully rough. Two distinct drag-reduction phenomena were investigated; bubble drag reduction (BDR) and air-layer drag reduction (ALDR).The streamwise distribution of skin-friction drag reduction was monitored with six skin-friction balances at downstream-distance-based Reynolds numbers to 220 million and at test speeds to 20.0msinitial zone1. These results indicated that there are three distinct regions associated with drag reduction with air injection: Region I, BDR; Region II, transition between BDR and ALDR; and Region III, ALDR. In addition, once ALDR was established: friction drag reduction in excess of 80% was observed over the entire smooth model for speeds to 15.3ms1 with the surface fully roughened (though approximately 50% greater volumetric air flux was required); and ALDR was sensitive to the inflow conditions. The sensitivity to the inflow conditions can be mitigated by employing a small faired step (10mm height in the experiment) that helps to create a fixed separation line.

  7. Heat stress reduction of helicopter crew wearing a ventilated vest

    Reffeltrath, P.A.

    2006-01-01

    Background: Helicopter pilots are often exposed to periods of high heat strain, especially when wearing survival suits. Therefore, a prototype of a ventilated vest was evaluated on its capability to reduce the heat strain of helicopter pilots during a 2-h simulated flight. Hypothesis: It was

  8. Basic Helicopter Handbook, Revised. AC 61-13A.

    Federal Aviation Administration (DOT), Washington, DC. Flight Standards Service.

    This technical manual was designed to assist applicants preparing for the private, commercial, and flight instructor pilot certificates with a helicopter rating. The chapters outline general aerodynamics, aerodynamics of flight, loads and load factors, function of controls, other helicopter components and their functions, introduction to the…

  9. Small-Scale Helicopter Automatic Autorotation : Modeling, Guidance, and Control

    Taamallah, S.

    2015-01-01

    Our research objective consists in developing a, model-based, automatic safety recovery system, for a small-scale helicopter Unmanned Aerial Vehicle (UAV) in autorotation, i.e. an engine OFF flight condition, that safely flies and lands the helicopter to a pre-specified ground location. In pursuit

  10. Helicopter Emergency Medical Services: effects, costs and benefits

    A.N. Ringburg (Akkie)

    2009-01-01

    textabstractAdvanced prehospital medical care with air transport was introduced in the Netherlands in May 1995. The fi rst helicopter Mobile Medical Team, also called Helicopter Emergency Medical Service (HEMS) was a joint venture initiative of the VU Medical Center in Amsterdam and the Algemene

  11. 78 FR 52407 - Airworthiness Directives; Eurocopter France Helicopters

    2013-08-23

    ... prevent failure of float and subsequent loss of control of the helicopter during an emergency water... requirements were intended to prevent failure of float and subsequent loss of control of the helicopter during... in the float becoming punctured, failure of the float to inflate, and subsequent loss of control of...

  12. The Helicopter Parent: Research toward a Typology (Part I)

    Somers, Patricia; Settle, Jim

    2010-01-01

    With 117,000 hits on a recent Google[TM] search, the phenomenon of helicopter parenting has been widely reported in the popular press. Yet the scholarly literature is anemic on the topic. This article, part one of a two-part series, presents the small body of research on helicopter parenting and describes a qualitative study of 190 participants…

  13. The Helicopter Parent (Part 2): International Arrivals and Departures

    Somers, Patricia; Settle, Jim

    2010-01-01

    The phenomenon of helicopter parenting has been widely reported, yet the research literature is anemic on the topic. Based on interviews and focus groups involving 190 academic and student services professionals, this article continues by discussing the social, psychological, economic, and cultural factors that influence helicoptering; exploring…

  14. Power harvesting using piezoelectric materials: applications in helicopter rotors

    de Jong, Pieter

    2013-01-01

    The blades of helicopters are heavily loaded and are critical components. Failure of any one blade will lead to loss of the aircraft. Currently, the technical lifespan of helicopter blades is calculated using a worst-case operation scenario. The consequence is that a blade that may be suitable for,

  15. Vision Aided State Estimation for Helicopter Slung Load System

    Bisgaard, Morten; Bendtsen, Jan Dimon; la Cour-Harbo, Anders

    2007-01-01

    This paper presents the design and verification of a state estimator for a helicopter based slung load system. The estimator is designed to augment the IMU driven estimator found in many helicopter UAV s and uses vision based updates only. The process model used for the estimator is a simple 4...

  16. Sleep and Alertness in North Sea Helicopter Operations

    Simons, M.; Wilschut, E.S.; Valk, P.J.L.

    2011-01-01

    Introduction : Dutch North Sea helicopter operations are characterized by multiple sector flights to offshore platforms under difficult environmental conditions. In the context of a Ministry of Transport program to improve safety levels of helicopter operations, we assessed effects of pre-duty

  17. 78 FR 15277 - Airworthiness Directives; Eurocopter France Helicopters

    2013-03-11

    ... the ASB as mandatory. Costs of Compliance We estimate that this AD affects three helicopters of U.S... of the helicopter's bottom structure. AD 2006- 0152 requires compliance with Eurocopter Alert Service... with France, EASA, its technical representative, has notified us of the unsafe condition described in...

  18. Modeling, Estimation, and Control of Helicopter Slung Load System

    Bisgaard, Morten

    and simulating different slung load suspension types. It further includes detection and response to wire slacking and tightening, it models the aerodynamic coupling between the helicopter and the load, and can be used for multilift systems with any combination of multiple helicopters and multiple loads...

  19. 77 FR 68057 - Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

    2012-11-15

    ... Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters AGENCY: Federal Aviation Administration (FAA... Sikorsky Aircraft Corporation (Sikorsky) Model S-76C helicopters. This AD requires installing an improved... Corporation, Attn: Manager, Commercial Technical Support, mailstop s581a, 6900 Main Street, Stratford, CT...

  20. 78 FR 23698 - Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

    2013-04-22

    ... Corporation Helicopters AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of proposed... Corporation (Sikorsky) Model S-92A helicopters to require modifying the No. 1 engine forward firewall center... Aircraft Corporation, Attn: Manager, Commercial Technical Support, mailstop s581a, 6900 Main Street...

  1. 78 FR 60656 - Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

    2013-10-02

    ... Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters AGENCY: Federal Aviation Administration (FAA... Aircraft Corporation (Sikorsky) Model S-92A helicopters to require modifying the No. 1 engine forward... Sikorsky Aircraft Corporation, Attn: Manager, Commercial Technical Support, mailstop s581a, 6900 Main...

  2. 77 FR 68061 - Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

    2012-11-15

    ... Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters AGENCY: Federal Aviation Administration (FAA... Aircraft Corporation (Sikorsky) Model S-92A helicopters. This AD requires inspecting the tail rotor (T/R... Corporation, Attn: Manager, Commercial Technical Support, mailstop s581a, 6900 Main Street, Stratford, CT...

  3. 77 FR 18969 - Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

    2012-03-29

    ... Corporation Helicopters AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of proposed... Aircraft Corporation (Sikorsky) Model S-76C helicopters. This proposed AD is prompted by a bird-strike to.... For service information identified in this proposed AD, contact Sikorsky Aircraft Corporation, Attn...

  4. 77 FR 28328 - Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

    2012-05-14

    ... Corporation Helicopters AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of proposed... Corporation (Sikorsky) Model S-92A helicopters, which requires inspecting the tail rotor (T/R) pylon for a... service information identified in this proposed AD, contact Sikorsky Aircraft Corporation, Attn: Manager...

  5. 77 FR 21402 - Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

    2012-04-10

    ... Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters AGENCY: Federal Aviation Administration (FAA... Aircraft Corporation (Sikorsky) Model S-92A helicopters. This AD was prompted by the discovery of tail... identified in this AD, contact Sikorsky Aircraft Corporation, Attn: Manager, Commercial Technical Support...

  6. Full State Estimation for Helicopter Slung Load System

    Bisgaard, Morten; la Cour-Harbo, Anders; Bendtsen, Jan Dimon

    This paper presents the design of a state estimator system for a generic helicopter based slung load system. The estimator is designed to deliver full rigid body state information for both helicopter and load and is based on the unscented Kalman filter. Two different approaches are investigated......: One based on a parameter free kinematic model and one based on a full aerodynamic helicopter and slung load model. The kinematic model approach uses acceleration and rate information from two Inertial Measurement Units, one on the helicopter and one on the load, to drive a simple kinematic model....... A simple and effective virtual sensor method is developed to maintain the constraints imposed by the wires in the system. The full model based approach uses a complex aerodynamical model to describe the helicopter together with a generic rigid body model. This rigid body model is based on a redundant...

  7. Full State Estimation for Helicopter Slung Load System

    Bisgaard, Morten; la Cour-Harbo, Anders; Bendtsen, Jan Dimon

    2007-01-01

    This paper presents the design of a state estimator system for a generic helicopter based slung load system. The estimator is designed to deliver full rigid body state information for both helicopter and load and is based on the unscented Kalman filter. Two different approaches are investigated......: One based on a parameter free kinematic model and one based on a full aerodynamic helicopter and slung load model. The kinematic model approach uses acceleration and rate information from two Inertial Measurement Units, one on the helicopter and one on the load, to drive a simple kinematic model....... A simple and effective virtual sensor method is developed to maintain the constraints imposed by the wires in the system. The full model based approach uses a complex aerodynamical model to describe the helicopter together with a generic rigid body model. This rigid body model is based on a redundant...

  8. 75 FR 62639 - Air Ambulance and Commercial Helicopter Operations, Part 91 Helicopter Operations, and Part 135...

    2010-10-12

    ... helicopter air ambulance operators implement a safety management system program that includes sound risk... partially address NTSB Safety Recommendation A-09-89 regarding the implementation of sound risk management... documents. Authority for This Rulemaking The FAA's authority to issue rules on aviation safety is found in...

  9. 77 FR 64439 - Airworthiness Directives; Bell Helicopter Textron Canada (Bell) Model Helicopters

    2012-10-22

    ... unsafe condition for the Bell Model 430 helicopters. Discrepancies in the processing and display of air... pilot and copilot electronic attitude direction indicators airspeed indicators; [cir] Leak testing the... and responsibilities among the various levels of government. For the reasons discussed, I certify this...

  10. Using Discrete Event Simulation To Analyze Personnel Requirements For The Malaysian Armys New Utility Helicopter Fleet

    2016-06-01

    HELICOPTER FLEET Hasnan bin Mohamad Rais Major, Malaysian Army B.S., University Technology of Malaysia , 2000 Submitted in partial...HELICOPTER MAINTENANCE POLICY B. The objective of MAA helicopter maintenance activities is to preserve helicopter safety and mission reliability to

  11. 14 CFR 29.71 - Helicopter angle of glide: Category B.

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Helicopter angle of glide: Category B. 29... AIRCRAFT AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Flight Performance § 29.71 Helicopter angle of glide: Category B. For each category B helicopter, except multiengine helicopters meeting the...

  12. 33 CFR 149.655 - What are the requirements for helicopter fueling facilities?

    2010-07-01

    ... helicopter fueling facilities? 149.655 Section 149.655 Navigation and Navigable Waters COAST GUARD... EQUIPMENT Design and Equipment Helicopter Fueling Facilities § 149.655 What are the requirements for helicopter fueling facilities? Helicopter fueling facilities must comply with 46 CFR 108.489 or an equivalent...

  13. Drag reduction statistics in a channel flow

    Jimenez-Bernal, Jose A. [Instituto Politecnico Nacional, LABINTHAP-SEPI-ESIME, Edif. 5, 3er piso Col. Lindavista, Mexico DF 07738 (Mexico); Hassan, Yassin A.; Gutierrez-Torres, Claudia del C. [Nuclear Engineering Department, Texas A and M University, College Station, TX 77843-3123 (United States)

    2005-07-01

    Full text of publication follows: Methods to reduce the drag have been studied for many years because of the promising payoffs that can be attained. In this investigation, the evaluation of statistics such as skewness, flatness, spectra of the stream-wise velocity fluctuations is performed for single phase flow and for two phase flow. Micro-bubbles with an average diameter of 30 {mu}m and a local void fraction of 4.8 % were produced by electrolysis and injected inside the boundary layer. This value of void fraction produced a 38.45 % decrease of the drag. The experiments were conducted in a channel flow at a Reynolds number Re 5128 (considering half height of the channel, the bulk velocity and the kinematics viscosity of the water). The channel was made of acrylic due to the optical properties of this material; its dimensions are 3.85 m long, 0.206 m wide and 0.056 m high. A pressure transducer that ranges from 0 to 35 Pa is located in the test station to measure the pressure drop in single phase flow; this pressure value is used to calculate the shear wall stress. The shear wall stress of two phase flow was measured from the velocity fields obtained from Particle Image Velocimetry (PIV) technique. PIV was utilized to measure instantaneous velocity fields in the stream-wise-normal (x-y) plane. The use of low-local values of void fraction caused a reduction of undesirable speckles effects and an absence of extreme brightness provoked by high bubble saturation. The measurements were carried out in the upper wall of the channel at 3.15 m downstream the inlet's channel. The PIV system is formed by a CCD camera with a resolution of 1008 x 1018 pixels and a double pulse laser with a maximum power 400 mJ and a wavelength of 532 nm (green light). The laser beam was transformed into a sheet of light by an array of cylindrical lenses. Two hundred frames with an area of 1.28 cm{sup 2} were recorded to obtain one hundred velocity fields. The time separation between

  14. Drag reduction statistics in a channel flow

    Jimenez-Bernal, Jose A.; Hassan, Yassin A.; Gutierrez-Torres, Claudia del C.

    2005-01-01

    Full text of publication follows: Methods to reduce the drag have been studied for many years because of the promising payoffs that can be attained. In this investigation, the evaluation of statistics such as skewness, flatness, spectra of the stream-wise velocity fluctuations is performed for single phase flow and for two phase flow. Micro-bubbles with an average diameter of 30 μm and a local void fraction of 4.8 % were produced by electrolysis and injected inside the boundary layer. This value of void fraction produced a 38.45 % decrease of the drag. The experiments were conducted in a channel flow at a Reynolds number Re 5128 (considering half height of the channel, the bulk velocity and the kinematics viscosity of the water). The channel was made of acrylic due to the optical properties of this material; its dimensions are 3.85 m long, 0.206 m wide and 0.056 m high. A pressure transducer that ranges from 0 to 35 Pa is located in the test station to measure the pressure drop in single phase flow; this pressure value is used to calculate the shear wall stress. The shear wall stress of two phase flow was measured from the velocity fields obtained from Particle Image Velocimetry (PIV) technique. PIV was utilized to measure instantaneous velocity fields in the stream-wise-normal (x-y) plane. The use of low-local values of void fraction caused a reduction of undesirable speckles effects and an absence of extreme brightness provoked by high bubble saturation. The measurements were carried out in the upper wall of the channel at 3.15 m downstream the inlet's channel. The PIV system is formed by a CCD camera with a resolution of 1008 x 1018 pixels and a double pulse laser with a maximum power 400 mJ and a wavelength of 532 nm (green light). The laser beam was transformed into a sheet of light by an array of cylindrical lenses. Two hundred frames with an area of 1.28 cm 2 were recorded to obtain one hundred velocity fields. The time separation between consecutive pulses

  15. Drag of ballistic electrons by an ion beam

    Gurevich, V. L.; Muradov, M. I., E-mail: mag.muradov@mail.ioffe.ru [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

    2015-12-15

    Drag of electrons of a one-dimensional ballistic nanowire by a nearby one-dimensional beam of ions is considered. We assume that the ion beam is represented by an ensemble of heavy ions of the same velocity V. The ratio of the drag current to the primary current carried by the ion beam is calculated. The drag current turns out to be a nonmonotonic function of velocity V. It has a sharp maximum for V near v{sub nF}/2, where n is the number of the uppermost electron miniband (channel) taking part in conduction and v{sub nF} is the corresponding Fermi velocity. This means that the phenomenon of ion beam drag can be used for investigation of the electron spectra of ballistic nanostructures. We note that whereas observation of the Coulomb drag between two parallel quantum wires may in general be complicated by phenomena such as tunneling and phonon drag, the Coulomb drag of electrons of a one-dimensional ballistic nanowire by an ion beam is free of such spurious effects.

  16. Search for a solute-drag effect in dendritic solidification

    Eckler, K.; Herlach, D.M.; Aziz, M.J.

    1994-01-01

    The authors report the results of an indirect experimental test for the solute-drag effect in alloy solidification by fitting the data of Eckler et.al. for Ni-B dendrite tip velocities vs undercooling to models in several ways. The unknown equilibrium partition coefficient, k e , was varied as a fitting parameter. When they combine the dendrite growth model of Boettinger et al. with the Continuous Growth Model (CGM) of Aziz and Kaplan with solute drag, they cannot fit the data for any value of k e . When they combine dendrite growth theory with the CGM without solute drag, they obtain a reasonable fit to the data for k e = 4 x 10 -6 . When they combine dendrite growth theory with a new partial-solute-drag interpolation between the with-solute-drag and the without-solute-drag versions of the CGM, they obtain a still better fit to the data for k e = 2.8 x 10 - 4. This result points out the possibility of partial solute-drag during solidification and the importance of an independent determination of k e in order to distinguish between models

  17. Resolvent-based feedback control for turbulent friction drag reduction

    Kawagoe, Aika; Nakashima, Satoshi; Luhar, Mitul; Fukagata, Koji

    2017-11-01

    Suboptimal control for turbulent friction drag reduction has been studied extensively. Nakashima et al. (accepted) extended resolvent analysis to suboptimal control, and for the control where the streamwise wall shear stress is used as an input (Case ST), they revealed the control effect across spectral space is mixed: there are regions of drag increase as well as reduction. This suggests that control performance may be improved if the control is applied for selective wavelengths, or if a new law is designed to suppress the spectral region leading to drag increase. In the present study, we first assess the effect of suboptimal control for selective wavelengths via DNS. The friction Reynolds number is set at 180. For Case ST, resolvent analysis predicts drag reduction at long streamwise wavelengths. DNS with control applied only for this spectral region, however, did not result in drag reduction. Then, we seek an effective control law using resolvent analysis and propose a new law. DNS results for this law are consistent with predictions from resolvent analysis, and about 10% drag reduction is attained. Further, we discuss how this law reduces the drag from a dynamical and theoretical point of view. This work was supported through Grant-in-Aid for Scientic Research (C) (No. 25420129) by Japan Society for the Promotion of Science (JSPS).

  18. DEVELOPMENT AND VALIDATION OF NUMERICAL METHOD FOR STRENGTH ANALYSIS OF LATTICE COMPOSITE FUSELAGE STRUCTURES

    2016-01-01

    Full Text Available Lattice composite fuselage structures are developed as an alternative to conventional composite structures based on laminated skin and stiffeners. Structure layout of lattice structures allows to realize advantages of current composite materials to a maximal extent, at the same time minimizing their main shortcomings, that allows to provide higher weight efficiency for these structures in comparison with conventional analogues.Development and creation of lattice composite structures requires development of novel methods of strength anal- ysis, as conventional methods, as a rule, are aiming to strength analysis of thin-walled elements and do not allow to get confident estimation of local strength of high-loaded unidirectional composite ribs.In the present work the method of operative strength analysis of lattice composite structure is presented, based onspecialized FE-models of unidirectional composite ribs and their intersections. In the frames of the method, every rib is modeled by a caisson structure, consisting of arbitrary number of flanges and webs, modeled by membrane finite elements. Parameters of flanges and webs are calculated automatically from the condition of stiffness characteristics equality of real rib and the model. This method allows to perform local strength analysis of high-loaded ribs of lattice structure without use of here-dimensional finite elements, that allows to shorten time of calculations and sufficiently simplify the procedure of analysis of results of calculations.For validation of the suggested method, the results of experimental investigations of full-scale prototype of shell of lattice composite fuselage section have been used. The prototype of the lattice section was manufactured in CRISM and tested in TsAGI within the frames of a number of Russian and International scientific projects. The results of validation have shown that the suggested method allows to provide high operability of strength analysis, keeping

  19. Residual Strength Pressure Tests and Nonlinear Analyses of Stringer- and Frame-Stiffened Aluminum Fuselage Panels with Longitudinal Cracks

    Young, Richard D.; Rouse, Marshall; Ambur, Damodar R.; Starnes, James H., Jr.

    1999-01-01

    The results of residual strength pressure tests and nonlinear analyses of stringer- and frame-stiffened aluminum fuselage panels with longitudinal cracks are presented. Two types of damage are considered: a longitudinal crack located midway between stringers, and a longitudinal crack adjacent to a stringer and along a row of fasteners in a lap joint that has multiple-site damage (MSD). In both cases, the longitudinal crack is centered on a severed frame. The panels are subjected to internal pressure plus axial tension loads. The axial tension loads are equivalent to a bulkhead pressure load. Nonlinear elastic-plastic residual strength analyses of the fuselage panels are conducted using a finite element program and the crack-tip-opening-angle (CTOA) fracture criterion. Predicted crack growth and residual strength results from nonlinear analyses of the stiffened fuselage panels are compared with experimental measurements and observations. Both the test and analysis results indicate that the presence of MSD affects crack growth stability and reduces the residual strength of stiffened fuselage shells with long cracks.

  20. Effects of exhaust temperature on helicopter infrared signature

    Cheng-xiong, Pan; Jing-zhou, Zhang; Yong, Shan

    2013-01-01

    The effects of exhaust temperature on infrared signature (in 3–5 μm band) for a helicopter equipped with integrative infrared suppressor were numerically investigated. The internal flow of exhaust gas and the external downwash flow, as well as the mixing between exhaust gas and downwash were simulated by CFD software to determine the temperature distributions on the helicopter skin and in the exhaust plume. Based on the skin and plume temperature distributions, a forward–backward ray-tracing method was used to calculate the infrared radiation intensity from the helicopter with a narrow-band model. The results show that for a helicopter with its integrative infrared suppressor embedded inside its rear airframe, the exhaust temperature has significant influence on the plume radiation characteristics, while the helicopter skin radiation intensity has little impact. When the exhaust temperature is raised from 900 K to 1200 K, the plume radiation intensity in 3–5 μm band is increased by about 100%, while the skin radiation intensity is increased by only about 5%. In general, the effects of exhaust temperature on helicopter infrared radiation intensity are mainly concentrated on plume, especially obvious for a lower skin emissivity case. -- Highlights: ► The effect of exhaust temperature on infrared signature for a helicopter is numerically investigated. ► The impact of exhaust temperature on helicopter skin temperature is revealed. ► The impact of exhaust temperature on plume radiation characteristics is revealed. ► The impact of exhaust temperature on helicopter skin radiation is revealed. ► The impact of exhaust temperature on helicopter's total infrared radiation intensity is revealed

  1. Does modern helicopter construction reduce noise exposure in helicopter rescue operations?

    Küpper, Thomas; Jansing, Paul; Schöffl, Volker; van Der Giet, Simone

    2013-01-01

    During helicopter rescue operations the medical personnel are at high risk for hearing damage by noise exposure. There are two important factors to be taken into account: first, the extreme variability, with some days involving no exposure but other days with extreme exposure; second, the extreme noise levels during work outside the helicopter, e.g. during winch operations. The benefit of modern, less noisier constructions and the consequences for noise protection are still unknown. We estimated the noise exposure of the personnel for different helicopter types used during rescue operations in the Alps and in other regions of the world with special regard to the advanced types like Eurocopter EC 135 to compare the benefit of modern constructions for noise protection with earlier ones. The rescue operations over 1 year of four rescue bases in the Alps (Raron and Zermatt in Switzerland; Landeck and Innsbruck in Austria, n = 2731) were analyzed for duration of rescue operations (noise exposure). Noise levels were measured during rescue operations at defined points inside and outside the different aircraft. The setting is according to the European standard (Richtlinie 2003/10/EG Amtsblatt) and to Class 1 DIN/IEC 651. With both data sets the equivalent noise level L(eq8h) was calculated. For comparison it was assumed that all rescue operations were performed with a specific type of helicopter. Then model calculations for noise exposure by different helicopter types, such as Alouette IIIb, Alouette II 'Lama', Ecureuil AS350, Bell UH1D, Eurocopter EC135, and others were performed. Depending on modern technologies the situation for the personnel has been improved significantly. Nevertheless noise prevention, which includes noise intermissions in spare time, is essential. Medical checks of the crews by occupational medicine (e.g. 'G20' in Germany) are still mandatory.

  2. Bilateral macular colobomata: Temporal dragging of optic disc

    David J Mathew

    2015-01-01

    Full Text Available A 13-year-old male presented with decreased vision and squint from childhood. He had bilateral large colobomata at the macula in each eye, the one on the right being larger than the left. The disc was dragged temporally with straightening of the temporal retinal vessels. This is a case report of bilateral large macular coloboma and serves to report its association with a temporally dragged disc and straightened temporal retinal vessels. A dragged disc if present with a colobomatous defect at the macula may strengthen the case for diagnosis of macular coloboma and help exclude other differentials.

  3. Oscillating Sign of Drag in High Landau Levels

    von Oppen, Felix; Simon, Steven H.; Stern, Ady

    2001-01-01

    Motivated by experiments, we study the sign of the Coulomb drag voltage in a double layer system in a strong magnetic field. We show that the commonly used Fermi golden rule approach implicitly assumes a linear dependence of intralayer conductivity on density, and is thus inadequate in strong magnetic fields. Going beyond this approach, we show that the drag voltage commonly changes sign with density difference between the layers. We find that, in the quantum Hall regime, the Hall and longitudinal drag resistivities may be comparable. Our results are also relevant for pumping and acoustoelectric experiments

  4. Effect of guideway discontinuities on magnetic levitation and drag forces

    Rossing, T.D.; Korte, R.; Hull, J.R.

    1991-01-01

    Transients in the lift and drag forces on a NdFeB permanent magnet were observed as the magnet passed over various discontinuities in a rotating aluminum disk at velocities of 4 to 25 m/s. For full cuts in the disk, the amplitude of the lift and drag transients and the wave form of the drag transient depend on the width, and the amplitudes are much larger than for partial cuts. The use of a backing plate to join two cut segments is ineffective

  5. Conceptual Design of a Single-Aisle Turboelectric Commercial Transport With Fuselage Boundary Layer Ingestion

    Welstead, Jason R.; Felder, James L.

    2016-01-01

    A single-aisle commercial transport concept with a turboelectric propulsion system architecture was developed assuming entry into service in 2035 and compared to a similar technology conventional configuration. The turboelectric architecture consisted of two underwing turbofans with generators extracting power from the fan shaft and sending it to a rear fuselage, axisymmetric, boundary layer ingesting fan. Results indicate that the turbo- electric concept has an economic mission fuel burn reduction of 7%, and a design mission fuel burn reduction of 12% compared to the conventional configuration. An exploration of the design space was performed to better understand how the turboelectric architecture changes the design space, and system sensitivities were run to determine the sensitivity of thrust specific fuel consumption at top of climb and propulsion system weight to the motor power, fan pressure ratio, and electrical transmission efficiency of the aft boundary layer ingesting fan.

  6. Fuselage Boundary Layer Ingestion Propulsion Applied to a Thin Haul Commuter Aircraft for Optimal Efficiency

    Mikic, Gregor Veble; Stoll, Alex; Bevirt, JoeBen; Grah, Rok; Moore, Mark D.

    2016-01-01

    Theoretical and numerical aspects of aerodynamic efficiency of propulsion systems are studied. Focus is on types of propulsion that closely couples to the aerodynamics of the complete vehicle. We discuss the effects of local flow fields, which are affected both by conservative flow acceleration as well as total pressure losses, on the efficiency of boundary layer immersed propulsion devices. We introduce the concept of a boundary layer retardation turbine that helps reduce skin friction over the fuselage. We numerically investigate efficiency gains offered by boundary layer and wake interacting devices. We discuss the results in terms of a total energy consumption framework and show that efficiency gains offered depend on all the elements of the propulsion system.

  7. Investigation of Drag Coefficient for Rigid Ballute-like Shapes

    Carnasciali, Maria-Isabel; Mastromarino, Anthony

    2014-11-01

    One common method of decelerating an object during atmospheric entry, descent, and landing is the use of parachutes. Another deceleration technology is the ballute - a combination of balloon and parachute. A CFD study was conducted using commercially available software to investigate the flow-field and the coefficient of drag for various rigid ballute-like shapes at varying Reynolds numbers. The impact of size and placement of the burble-fence as well as number, size, and shape of inlets was considered. Recent experimental measurements conducted during NASA's Low-Density Supersonic Decelerator program revealed a much higher coefficient of drag (Cd) for ballutes than previously encountered. Using atmospheric drag to slow down and land reduces the need for heavy fuel and rocket engines and thus, high values of drag are desired. Funding for this work, in part, provided by the CT Space Grant Consortium.

  8. Drag Reduction through Pulsed Plasma Actuators, Phase I

    National Aeronautics and Space Administration — Drag reduction is a fundamental necessity in all aerodynamic designs, as it directly affects aircraft fuel efficiency which in turn affects endurance, range, and...

  9. Influence of Surface Roughness on Polymer Drag Reduction

    Ceccio, Steven L; Dowling, David R; Perlin, Marc; Solomon, Michael

    2007-01-01

    .... The details of that effort can be found in the final technical report for that project. The purpose of the additional investigation was to examine the physics and engineering of friction drag reduction methods for turbulent boundary layers (TBL...

  10. Drag force and jet propulsion investigation of a swimming squid

    Tabatabaei Mahdi

    2015-01-01

    Full Text Available In this study, CAD model of a squid was obtained by taking computer tomography images of a real squid. The model later placed into a computational domain to calculate drag force and performance of jet propulsion. The drag study was performed on the CAD model so that drag force subjected to real squid was revealed at squid’s different swimming speeds and comparison has been made with other underwater creatures (e.g., a dolphin, sea lion and penguin. The drag coefficient (referenced to total wetted surface area of squid is 0.0042 at Reynolds number 1.6x106 that is a %4.5 difference from Gentoo penguin. Besides, jet flow of squid was simulated to observe the flow region generated in the 2D domain utilizing dynamic mesh method to mimic the movement of squid’s mantle cavity.

  11. Experimental study of drag reduction in flumes and spillway tunnels

    Ying-kui Wang

    2010-06-01

    Full Text Available Experiments in an open flume model and spillway tunnel model were carried out using drag reduction techniques. Two drag reduction techniques were adopted in the experiments: polymer addition and coating. The drag reduction effect of a polyacrylamide (PAM solution and dimethyl silicone oil coating were studied in the flume model experiments, and the results were analyzed. Experiments were then carried out with a model of the Xiluodu Hydropower Station, the second largest dam in China. In order to reduce the resistance, the spillway tunnels were internally coated with dimethyl silicone oil. This is the first time that these drag reduction techniques have been applied to so large a hydraulic model. The experimental results show that the coating technique can effectively increase flood discharge. The outlet velocity and the jet trajectory distance are also increased, which enhances the energy dissipation of the spillway tunnel.

  12. Performance and Vibration Analyses of Lift-Offset Helicopters

    Jeong-In Go

    2017-01-01

    Full Text Available A validation study on the performance and vibration analyses of the XH-59A compound helicopter is conducted to establish techniques for the comprehensive analysis of lift-offset compound helicopters. This study considers the XH-59A lift-offset compound helicopter using a rigid coaxial rotor system as a verification model. CAMRAD II (Comprehensive Analytical Method of Rotorcraft Aerodynamics and Dynamics II, a comprehensive analysis code, is used as a tool for the performance, vibration, and loads analyses. A general free wake model, which is a more sophisticated wake model than other wake models, is used to obtain good results for the comprehensive analysis. Performance analyses of the XH-59A helicopter with and without auxiliary propulsion are conducted in various flight conditions. In addition, vibration analyses of the XH-59A compound helicopter configuration are conducted in the forward flight condition. The present comprehensive analysis results are in good agreement with the flight test and previous analyses. Therefore, techniques for the comprehensive analysis of lift-offset compound helicopters are appropriately established. Furthermore, the rotor lifts are calculated for the XH-59A lift-offset compound helicopter in the forward flight condition to investigate the airloads characteristics of the ABC™ (Advancing Blade Concept rotor.

  13. Atomistically informed solute drag in Al–Mg

    Zhang, F; Curtin, W A

    2008-01-01

    Solute drag in solute-strengthened alloys, caused by diffusion of solute atoms around moving dislocations, controls the stress at deformation rates and temperatures useful for plastic forming processes. In the technologically important Al–Mg alloys, the solute drag stresses predicted by classical theories are much larger than experiments, which is resolved in general by eliminating the singularity of the dislocation core via Peierls–Nabarro-type models. Here, the drag stress versus dislocation velocity is computed numerically using a realistic dislocation core structure obtained from an atomistic model to investigate the role of the core and obtain quantitative stresses for comparison with experiment. The model solves a discrete diffusion equation in a reference frame moving with the dislocation, with input solute enthalpies and diffusion activation barriers in the core computed by or estimated from atomistic studies. At low dislocation velocities, the solute drag stress is controlled by bulk solute diffusion because the core diffusion occurs too quickly. In this regime, the drag stress can be obtained using a Peierls–Nabarro model with a core spreading parameter tuned to best match the atomistic models. At intermediate velocities, both bulk and core diffusion can contribute to the drag, leading to a complex stress–velocity relationship showing two peaks in stress. At high velocities, the drag stress is controlled solely by diffusion within and across the core. Like the continuum models, the drag stress is nearly linear in solute concentration. The Orowan relationship is used to connect dislocation velocity to deformation strain rate. Accounting for the dependence of mobile dislocation density on stress, the simulations are in good agreement with experiments on Al–Mg alloys over a range of concentrations and temperatures

  14. Drag force in a D-instanton background

    Zhang, Zi-qiang; Luo, Zhong-jie; Hou, De-fu

    2018-06-01

    We study the drag force and diffusion coefficient with respect to a moving heavy quark in a D-instanton background, which corresponds to the Yang-Mills theory in the deconfining, high-temperature phase. It is shown that the presence of the D-instanton density tends to increase the drag force and decrease the diffusion coefficient, reverse to the effects of the velocity and the temperature. Moreover, the inclusion of the D-instanton density makes the medium less viscous.

  15. Thermal Transport and Drag Force in Improved Holographic QCD

    Gürsoy, Umut; Michalogiorgakis, Georgios; Nitti, Francesco; 10.1088

    2009-01-01

    We calculate the bulk viscosity, drag force and jet quenching parameter in Improved Holographic QCD. We find that the bulk viscosity rises near the phase transition but does not exceed the shear viscosity. The drag force shows the effects of asymptotic freedom both as a function of velocity and temperature. It indicates diffusion times of heavy quarks in rough agreement with data. The jet quenching parameter values computed via the light-like Wilson loop are in the lower range suggested by data.

  16. Progress towards a Drag-free SmallSat

    Saraf, Shailendhar

    The net force acting on a drag-free satellite is purely gravitational as all other forces, mainly atmospheric drag and solar radiation pressure, are canceled out. In order to achieve this, a free floating reference (test mass) inside the satellite is shielded against all forces but gravity and a system of thrusters is commanded by a control algorithm such that the relative displacement between the reference and the satellite stays constant. The main input to that control algorithm is the output of a sensor which measures the relative displacement between the satellite and the test mass. Internal disturbance forces such as electrostatic or magnetic forces cannot be canceled out his way and have to be minimized by a careful design of the satellite. A drag-free technology package is under development at Stanford since 2004. It includes an optical displacement sensor to measure the relative position of the test mass inside the satellite, a caging mechanism to lock the test mass during launch, a UV LED based charge management system to minimize the effect of electrostatic forces, a thermal enclosure, and the drag-free control algorithms. Possible applications of drag-free satellites in fundamental physics (Gravity Probe B, LISA), geodesy (GOCE), and navigation (TRIAD I). In this presentation we will highlight the progress of the technology development towards a drag-free mission. The planned mission on a SaudiSat bus will demonstrate drag-free technology on a small spacecraft at a fraction of the cost of previous drag-free missions. The target acceleration noise is 10-12 m/sec2. With multiple such satellites a GRACE-like mission with improved sensitivity and potentially improved spatial and temporal resolution can be achieved.

  17. Airborne radiation monitoring using a manned helicopter

    Sanada, Yukihisa; Nishizawa, Yukiyasu; Ishizaki, Azusa; Urabe, Yoshimi

    2017-01-01

    The Great East Japan Earthquake that occurred on 11 March 2011 generated a series of large tsunami waves that caused serious damage to the Fukushima Dai-ichi Nuclear Power Station, following which a large amount of radioactive material was discharged from the nuclear power plant into the environment. Airborne radiation measurements using a manned helicopter were applied to measure the radiation distribution immediately after accident as technique to quickly measure the radiation distribution over a wide area. In Japan, this technique was researched and developed in the 1980s. However, this technique and system were not applied immediately after the accident because standardization of analysis was not established and the Japanese system became deteriorated. This technique is important for post-accident studies at a nuclear facility. We summarized the methods of the airborne radiation measurement using a manned helicopter. In addition, measurement results of the dose rate distribution at the Fukushima Dai-ichi Nuclear Power Station are given in this paper. (author)

  18. Compound cycle engine for helicopter application

    Castor, Jere G.

    1986-01-01

    The Compound Cycle Engine (CCE) is a highly turbocharged, power compounded, ultra-high power density, light-weight diesel engine. The turbomachinery is similar to a moderate pressure ratio, free power turbine engine and the diesel core is high speed and a low compression ratio. This engine is considered a potential candidate for future military light helicopter applications. This executive summary presents cycle thermodynamic (SFC) and engine weight analyses performed to establish general engine operating parameters and configuration. An extensive performance and weight analysis based on a typical two hour helicopter (+30 minute reserve) mission determined final conceptual engine design. With this mission, CCE performance was compared to that of a T-800 class gas turbine engine. The CCE had a 31% lower-fuel consumption and resulted in a 16% reduction in engine plus fuel and fuel tank weight. Design SFC of the CCE is 0.33 lb-HP-HR and installed wet weight is 0.43 lbs/HP. The major technology development areas required for the CCE are identified and briefly discussed.

  19. Flight service evaluation of composite helicopter components

    Mardoian, George H.; Ezzo, Maureen B.

    1994-01-01

    This paper presents the results of a NASA funded contract and Sikorsky research and development programs to evaluate structural composite components in flight service on Sikorsky Model S-76 helicopters. Selected components were removed and tested at prescribed intervals over a nine year time frame. Four horizontal stabilizers and thirteen tail rotor spars were returned from commercial service in West Palm Beach, Florida and in the Gulf Coast region of Louisiana to determine the long term effects of operations in hot and humid climates on component performance. Concurrent with the flight component evaluation, panels of materials used in their fabrication were exposed to the environment in ground racks. Selected panels were tested annually to determine the effects of exposure on physical and mechanical properties. The results of 55,741 component flight hours and 911 months of field exposure are reported and compared with initial Federal Aviation Administration (FAA) certification data. The findings of this program have provided increased confidence in the long term durability of advanced composite materials used in helicopter structural applications.

  20. Navier slip model of drag reduction by Leidenfrost vapor layers

    Berry, Joseph D.; Vakarelski, Ivan Uriev; Chan, Derek Y. C.; Thoroddsen, Sigurdur T

    2017-01-01

    Recent experiments found that a hot solid sphere that is able to sustain a stable Leidenfrost vapor layer in a liquid exhibits significant drag reduction during free fall. The variation of the drag coefficient with Reynolds number deviates substantially from the characteristic drag crisis behavior at high Reynolds numbers. Measurements based on liquids of different viscosities show that the onset of the drag crisis depends on the viscosity ratio of the vapor to the liquid. Here we attempt to characterize the complexity of the Leidenfrost vapor layer with respect to its variable thickness and possible vapor circulation within, in terms of the Navier slip model that is defined by a slip length. Such a model can facilitate tangential flow and thereby alter the behavior of the boundary layer. Direct numerical and large eddy simulations of flow past a sphere at moderate to high Reynolds numbers (102≤Re≤4×104) are employed to quantify comparisons with experimental results, including the drag coefficient and the form of the downstream wake on the sphere. This provides a simple one parameter characterization of the drag reduction phenomenon due to a stable vapor layer that envelops a solid body.

  1. Navier slip model of drag reduction by Leidenfrost vapor layers

    Berry, Joseph D.

    2017-10-17

    Recent experiments found that a hot solid sphere that is able to sustain a stable Leidenfrost vapor layer in a liquid exhibits significant drag reduction during free fall. The variation of the drag coefficient with Reynolds number deviates substantially from the characteristic drag crisis behavior at high Reynolds numbers. Measurements based on liquids of different viscosities show that the onset of the drag crisis depends on the viscosity ratio of the vapor to the liquid. Here we attempt to characterize the complexity of the Leidenfrost vapor layer with respect to its variable thickness and possible vapor circulation within, in terms of the Navier slip model that is defined by a slip length. Such a model can facilitate tangential flow and thereby alter the behavior of the boundary layer. Direct numerical and large eddy simulations of flow past a sphere at moderate to high Reynolds numbers (102≤Re≤4×104) are employed to quantify comparisons with experimental results, including the drag coefficient and the form of the downstream wake on the sphere. This provides a simple one parameter characterization of the drag reduction phenomenon due to a stable vapor layer that envelops a solid body.

  2. Dragging of inertial frames inside the rotating neutron stars

    Chakraborty, Chandrachur; Modak, Kamakshya Prasad; Bandyopadhyay, Debades, E-mail: chandrachur.chakraborty@saha.ac.in, E-mail: kamakshya.modak@saha.ac.in [Astroparticle Physics and Cosmology Division, Saha Institute of Nuclear Physics, Kolkata 700064 (India)

    2014-07-20

    We derive the exact frame-dragging rate inside rotating neutron stars. This formula is applied to show that the frame-dragging rate monotonically decreases from the center to the surface of the neutron star along the pole. In the case of the frame-dragging rate along the equatorial distance, it decreases initially away from the center, becomes negligibly small well before the surface of the neutron star, rises again, and finally approaches to a small value at the surface. The appearance of a local maximum and minimum in this case is the result of the dependence of frame-dragging frequency on the distance and angle. Moving from the equator to the pole, it is observed that this local maximum and minimum in the frame-dragging rate along the equator disappear after crossing a critical angle. It is also noted that the positions of the local maximum and minimum of the frame-dragging rate along the equator depend on the rotation frequency and central energy density of a particular pulsar.

  3. Aerodynamic drag of modern soccer balls.

    Asai, Takeshi; Seo, Kazuya

    2013-12-01

    Soccer balls such as the Adidas Roteiro that have been used in soccer tournaments thus far had 32 pentagonal and hexagonal panels. Recently, the Adidas Teamgeist II and Adidas Jabulani, respectively having 14 and 8 panels, have been used at tournaments; the aerodynamic characteristics of these balls have not yet been verified. Now, the Adidas Tango 12, having 32 panels, has been developed for use at tournaments; therefore, it is necessary to understand its aerodynamic characteristics. Through a wind tunnel test and ball trajectory simulations, this study shows that the aerodynamic resistance of the new 32-panel soccer ball is larger in the high-speed region and lower in the middle-speed region than that of the previous 14- and 8-panel balls. The critical Reynolds number of the Roteiro, Teamgeist II, Jabulani, and Tango 12 was ~2.2 × 10(5) (drag coefficient, C d  ≈ 0.12), ~2.8 × 10(5) (C d  ≈ 0.13), ~3.3 × 10(5) (C d  ≈ 0.13), and ~2.4 × 10(5) (C d  ≈ 0.15), respectively. The flight trajectory simulation suggested that the Tango 12, one of the newest soccer balls, has less air resistance in the medium-speed region than the Jabulani and can thus easily acquire large initial velocity in this region. It is considered that the critical Reynolds number of a soccer ball, as considered within the scope of this experiment, depends on the extended total distance of the panel bonds rather than the small designs on the panel surfaces.

  4. Simulating effectiveness of helicopter evasive manoeuvres to RPG attack

    Anderson, D.; Thomson, D. G.

    2010-04-01

    The survivability of helicopters under attack by ground troops using rocket propelled grenades has been amply illustrated over the past decade. Given that an RPG is unguided and it is infeasible to cover helicopters in thick armour, existing optical countermeasures are ineffective - the solution is to compute an evasive manoeuvre. In this paper, an RPG/helicopter engagement model is presented. Manoeuvre profiles are defined in the missile approach warning sensor camera image plane using a local maximum acceleration vector. Required control inputs are then computed using inverse simulation techniques. Assessments of platform survivability to several engagement scenarios are presented.

  5. Nonlinear Feedforward Control for Wind Disturbance Rejection on Autonomous Helicopter

    Bisgaard, Morten; la Cour-Harbo, Anders; A. Danapalasingam, Kumeresan

    2010-01-01

    for the purpose. The model is inverted for the calculation of rotor collective and cyclic pitch angles given the wind disturbance. The control strategy is then applied on a small helicopter in a controlled wind environment and flight tests demonstrates the effectiveness and advantage of the feedforward controller.......This paper presents the design and verification of a model based nonlinear feedforward controller for wind disturbance rejection on autonomous helicopters. The feedforward control is based on a helicopter model that is derived using a number of carefully chosen simplifications to make it suitable...

  6. Adaptive Control System for Autonomous Helicopter Slung Load Operations

    Bisgaard, Morten; la Cour-Harbo, Anders; Bendtsen, Jan Dimon

    2010-01-01

    system on the helicopter that measures the position of the slung load. The controller is a combined feedforward and feedback scheme for simultaneous avoidance of swing excitation and active swing damping. Simulations and laboratory flight tests show the effectiveness of the combined control system......This paper presents design and verification of an estimation and control system for a helicopter slung load system. The estimator provides position and velocity estimates of the slung load and is designed to augment existing navigation in autonomous helicopters. Sensor input is provided by a vision......, yielding significant load swing reduction compared to the baseline controller....

  7. 77 FR 63262 - Airworthiness Directives; Eurocopter France Helicopters

    2012-10-16

    ... the outer skin and the butt strap in the sliding cowling right-hand and left-hand rail attachment... sliding cowling right-hand and left-hand rail attachment areas on Frame 5295 as shown in Figure 2 of... States of the European Union, which states that a crack was discovered in a fuselage frame during a daily...

  8. Helicopter type and accident severity in Helicopter Emergency Medical Services missions.

    Hinkelbein, Jochen; Schwalbe, Mandy; Wetsch, Wolfgang A; Spelten, Oliver; Neuhaus, Christopher

    2011-12-01

    Whereas accident rates and fatal accident rates for Helicopter Emergency Medical Services (HEMS) were investigated sufficiently, resulting consequences for the occupants remain largely unknown. The present study aimed to classify HEMS accidents in Germany to prognosticate accident severity with regard to the helicopter model used. German HEMS accidents (1 Sept. 1970-31 Dec. 2009) were gathered as previously reported. Accidents were categorized in relation to the most severe injury, i.e., (1) no; (2) slight; (3) severe; and (4) fatal injuries. Only helicopter models with at least five accidents were analyzed to retrieve representative data. Prognostication was estimated by the relative percentage of each injury type compared to the total number of accidents. The model BO105 was most often involved in accidents (38 of 99), followed by BK117 and UH-1D. OfN = 99 accidents analyzed, N = 63 were without any injuries (63.6%), N = 8 resulted in minor injuries of the occupants (8.1%), and N = 9 in major injuries (9.1%). Additionally, N = 19 fatal accidents (19.2%) were registered. EC135 and BK1 17 had the highest incidence of uninjured occupants (100% vs. 88.2%) and the lowest percentage of fatal injuries (0% vs. 5.9%; all P > 0.05). Most fatal accidents occurred with the models UH-1D, Bell 212, and Bell 412. Use of the helicopter models EC135 and BK117 resulted in a high percentage of uninjured occupants. In contrast, the fatality rate was highest for the models Bell UH-I D, Bell 222, and Bell 412. Data from the present study allow for estimating accident risk in HEMS missions and prognosticating resulting fatalities, respectively.

  9. Nation Drag: Uses of the Exotic

    Micol Seigel

    2009-02-01

    Full Text Available

    In Uneven Encounters, the forthcoming book from which this article is excerpted, Micol Seigel chronicles the exchange of popular culture between Brazil and the United States in the years between the World Wars, and she demonstrates how that exchange affected ideas of race and nation in both countries. From Americans interpreting advertisements for Brazilian coffee or dancing the Brazilian maxixe, to Rio musicians embracing the “foreign” qualities of jazz, Seigel traces a lively, cultural back-and-forth. Along the way, she shows how race and nation are constructed together, by both non-elites and elites, and gleaned from global cultural and intellectual currents as well as local, regional, and national ones. Seigel explores the circulation of images of Brazilian coffee and of maxixe in the United States during the period just after the imperial expansions of the early twentieth century. Exoticist interpretations structured North Americans’ paradoxical sense of self as productive “consumer citizens.” Some people, however, could not simply assume the privileges of citizenship. In their struggles against racism, Afro-descended citizens living in the cities of Rio de Janeiro, São Paulo, New York, and Chicago encountered images and notions of each other, and found them useful. Seigel introduces readers to cosmopolitan Afro-Brazilians and African Americans who rarely traveled far but who absorbed ideas from abroad nonetheless. African American vaudeville artists saw the utility of pretending to “be” Brazilian to cross the color line on stage. Putting on “nation drag,” they passed not from one race to another but out of familiar racial categories entirely. Afro-Brazilian journalists reported intensively on foreign, particularly North American, news and eventually entered into conversation with the U.S. black press in a collaborative but still conflictual dialogue. Seigel suggests that projects comparing U.S. and

  10. Nation Drag: Uses of the Exotic

    Micol Seigel

    2009-02-01

    Full Text Available In Uneven Encounters, the forthcoming book from which this article is excerpted, Micol Seigel chronicles the exchange of popular culture between Brazil and the United States in the years between the World Wars, and she demonstrates how that exchange affected ideas of race and nation in both countries. From Americans interpreting advertisements for Brazilian coffee or dancing the Brazilian maxixe, to Rio musicians embracing the “foreign” qualities of jazz, Seigel traces a lively, cultural back-and-forth. Along the way, she shows how race and nation are constructed together, by both non-elites and elites, and gleaned from global cultural and intellectual currents as well as local, regional, and national ones. Seigel explores the circulation of images of Brazilian coffee and of maxixe in the United States during the period just after the imperial expansions of the early twentieth century. Exoticist interpretations structured North Americans’ paradoxical sense of self as productive “consumer citizens.” Some people, however, could not simply assume the privileges of citizenship. In their struggles against racism, Afro-descended citizens living in the cities of Rio de Janeiro, São Paulo, New York, and Chicago encountered images and notions of each other, and found them useful. Seigel introduces readers to cosmopolitan Afro-Brazilians and African Americans who rarely traveled far but who absorbed ideas from abroad nonetheless. African American vaudeville artists saw the utility of pretending to “be” Brazilian to cross the color line on stage. Putting on “nation drag,” they passed not from one race to another but out of familiar racial categories entirely. Afro-Brazilian journalists reported intensively on foreign, particularly North American, news and eventually entered into conversation with the U.S. black press in a collaborative but still conflictual dialogue. Seigel suggests that projects comparing U.S. and Brazilian racial

  11. Wind-Tunnel Investigations of Blunt-Body Drag Reduction Using Forebody Surface Roughness

    Whitmore, Stephen A.; Sprague, Stephanie; Naughton, Jonathan W.; Curry, Robert E. (Technical Monitor)

    2001-01-01

    This paper presents results of wind-tunnel tests that demonstrate a novel drag reduction technique for blunt-based vehicles. For these tests, the forebody roughness of a blunt-based model was modified using micomachined surface overlays. As forebody roughness increases, boundary layer at the model aft thickens and reduces the shearing effect of external flow on the separated flow behind the base region, resulting in reduced base drag. For vehicle configurations with large base drag, existing data predict that a small increment in forebody friction drag will result in a relatively large decrease in base drag. If the added increment in forebody skin drag is optimized with respect to base drag, reducing the total drag of the configuration is possible. The wind-tunnel tests results conclusively demonstrate the existence of a forebody dragbase drag optimal point. The data demonstrate that the base drag coefficient corresponding to the drag minimum lies between 0.225 and 0.275, referenced to the base area. Most importantly, the data show a drag reduction of approximately 15% when the drag optimum is reached. When this drag reduction is scaled to the X-33 base area, drag savings approaching 45,000 N (10,000 lbf) can be realized.

  12. Swing Damping for Helicopter Slung Load Systems using Delayed Feedback

    Bisgaard, Morten; la Cour-Harbo, Anders; Bendtsen, Jan Dimon

    2009-01-01

    of swing. The design of the delayed feedback controller is presented as an optimization problem which gives the possibility of an automated design process. Simulations and flight test verifications of the control system on two different autonomous helicopters are presented and it is shown how a significant......This paper presents the design and verification of a swing reducing controller for helicopter slung load systems using intentional delayed feedback. It is intended for augmenting a trajectory tracking helicopter controller and thereby improving the slung load handing capabilities for autonomous...... helicopters. The delayed feedback controller is added to actively reduce oscillations of the slung load by improving the damping of the slung load pendulum modes. Furthermore, it is intended for integration with a feedforward control scheme based on input shaping for concurrent avoidance and dampening...

  13. High Fidelity Multidisciplinary Tool Development for Helicopter Quieting

    Chen, Chung-Lung; Chen, Ya-Chi; Chen, Bing; Jain, Rohit; Lund, Tom; Zhao, Hongwu; Wang, Z.-J; Sun, Yuzhi; Saberi, Hossein; Shih, T.-H

    2007-01-01

    .... The problem is indeed multidisciplinary. Current helicopter blade designers use computational models, which depend heavily on experimental data and cannot be used to predict any novel design, which is a significant departure from existing designs...

  14. The effect of air flow, panel curvature, and internal pressurization on field-incidence transmission loss. [acoustic propagation through aircraft fuselage

    Koval, L. R.

    1975-01-01

    In the context of sound transmission through aircraft fuselage panels, equations for the field-incidence transmission loss (TL) of a single-walled panel are derived that include the effects of external air flow, panel curvature, and internal fuselage pressurization. These effects are incorporated into the classical equations for the TL of single panels, and the resulting double integral for field-incidence TL is numerically evaluated for a specific set of parameters.

  15. Structural FEM analysis of the strut-to-fuselage joint of a two-seat composite aircraft

    Vargas-Rojas, Erik; Camarena-Arellano, Diego; Hernández-Moreno, Hilario

    2014-01-01

    An analysis of a strut-to-fuselage joint is realized in order to evaluate the zones with a high probability of failure by means of a safety factor. The whole section is analyzed using the Finite Element Method (FEM) so as to estimate static resistance behavior, therefore it is necessary a numerical mock-up of the section, the mechanical properties of the Carbon-Epoxy (C-Ep) material, and to evaluate the applied loads. Results of the analysis show that the zones with higher probability of failure are found around the wing strut and the fuselage joint, with a safety factor lower than expected in comparison with the average safety factor used on aircrafts built mostly with metals

  16. Engineering Design Handbook. Helicopter Engineering. Part One. Preliminary Design

    1974-08-30

    the cost of prime interest being life-cycle cost, climate that is hot or cold, in atmosphere that is humid Chapter 3 discusses helicopter performance...required to satisfy 8-3.2 ENGINE INSTALLATION LOSSES varying climatic and environmental factors. For in- stance, maintenance of the helicopter should be...thammable h aulic , asytem l at mhtproidtem a considering the overall flight mission in segments, dur- source of flammable fluids, as well as electrical

  17. Structural Integrity and Aging-Related Issues of Helicopters

    2000-10-01

    inherently damage lolerant , any damage- inspection in critical locations where tests have indicated tolerant features in airframe design only enhances...required, so European Rotorcraft Forum. Marseilles, France, 15- that helicopters are equipped with such features as fly- 17 September 1998 . by-wire and...fatigue Evaluation of structural integrity issues of aging helicopters. The Structure," 29 April, 1998 . extended safe-life approach encompasses the best

  18. VH-92A Presidential Helicopter (VH-92A)

    2015-12-01

    provide safe, reliable, and timely transportation for the President, Vice President, Foreign Heads of State, and other official parties as directed by...the Director of the White House Military Office. Presidential helicopter transportation requirements are executed by Marine Helicopter Squadron One...Review Jul 2016 Jul 2016 Jan 2017 Jul 2016 Milestone C Jan 2019 Jan 2019 Jul 2019 Jan 2019 IOT &E Complete Mar 2020 Mar 2020 Sep 2020 Mar 2020 IOC Jul

  19. Study of Helicopter Performance and Terminal Instrument Procedures

    1980-06-01

    possible employment of decelerating or other innovative approaches to be discussed in Section 3 and may be employed to advantage in reviewing missed...330J Puma is a 19 passenger medium helicopter manufactured by Societe Nationale Industrielle Aerospatiale of Marignane, France and marketed in the...for use by the French and British armed forces. It is manufactured by the Helicopter Divison of Societe Nationale Industrielle Aerospatiale of Marignane

  20. Active vibration suppression of helicopter horizontal stabilizers

    Cinquemani, Simone; Cazzulani, Gabriele; Resta, Ferruccio

    2017-04-01

    Helicopters are among the most complex machines ever made. While ensuring high performance from the aeronautical point of view, they are not very comfortable due to vibration mainly created by the main rotor and by the interaction with the surrounding air. One of the most solicited structural elements of the vehicle are the horizontal stabilizers. These elements are particularly stressed because of their composite structure which, while guaranteeing lightness and strength, is characterized by a low damping. This work makes a preliminary analysis on the dynamics of the structure and proposes different solutions to actively suppress vibrations. Among them, the best in terms of the relationship between performance and weight / complexity of the system is that based on inertial actuators mounted on the inside of the horizontal stabilizers. The work addresses the issue of the design of the device and its use in the stabilizer from both the numerical and the experimental points of view.

  1. The Effect of Volumetric Porosity on Roughness Element Drag

    Gillies, John; Nickling, William; Nikolich, George; Etyemezian, Vicken

    2016-04-01

    Much attention has been given to understanding how the porosity of two dimensional structures affects the drag force exerted by boundary-layer flow on these flow obstructions. Porous structures such as wind breaks and fences are typically used to control the sedimentation of sand and snow particles or create micro-habitats in their lee. Vegetation in drylands also exerts control on sediment transport by wind due to aerodynamic effects and interaction with particles in transport. Recent research has also demonstrated that large spatial arrays of solid three dimensional roughness elements can be used to reduce sand transport to specified targets for control of wind erosion through the effect of drag partitioning and interaction of the moving sand with the large (>0.3 m high) roughness elements, but porous elements may improve the effectiveness of this approach. A thorough understanding of the role porosity plays in affecting the drag force on three-dimensional forms is lacking. To provide basic understanding of the relationship between the porosity of roughness elements and the force of drag exerted on them by fluid flow, we undertook a wind tunnel study that systematically altered the porosity of roughness elements of defined geometry (cubes, rectangular cylinders, and round cylinders) and measured the associated change in the drag force on the elements under similar Reynolds number conditions. The elements tested were of four basic forms: 1) same sized cubes with tubes of known diameter milled through them creating three volumetric porosity values and increasing connectivity between the tubes, 2) cubes and rectangular cylinders constructed of brass screen that nested within each other, and 3) round cylinders constructed of brass screen that nested within each other. The two-dimensional porosity, defined as the ratio of total surface area of the empty space to the solid surface area of the side of the element presented to the fluid flow was conserved at 0.519 for

  2. Development of adaptive helicopter seat systems for aircrew vibration mitigation

    Chen, Yong; Wickramasinghe, Viresh; Zimcik, David G.

    2008-03-01

    Helicopter aircrews are exposed to high levels of whole body vibration during flight. This paper presents the results of an investigation of adaptive seat mount approaches to reduce helicopter aircrew whole body vibration levels. A flight test was conducted on a four-blade helicopter and showed that the currently used passive seat systems were not able to provide satisfactory protection to the helicopter aircrew in both front-back and vertical directions. Long-term exposure to the measured whole body vibration environment may cause occupational health issues such as spine and neck strain injuries for aircrew. In order to address this issue, a novel adaptive seat mount concept was developed to mitigate the vibration levels transmitted to the aircrew body. For proof-of-concept demonstration, a miniature modal shaker was properly aligned between the cabin floor and the seat frame to provide adaptive actuation authority. Adaptive control laws were developed to reduce the vibration transmitted to the aircrew body, especially the helmet location in order to minimize neck and spine injuries. Closed-loop control test have been conducted on a full-scale helicopter seat with a mannequin configuration and a large mechanical shaker was used to provide representative helicopter vibration profiles to the seat frame. Significant vibration reductions to the vertical and front-back vibration modes have been achieved simultaneously, which verified the technical readiness of the adaptive mount approach for full-scale flight test on the vehicle.

  3. Idiopathic Syringomyelia in a Military Helicopter Pilot.

    Schiemer, Anthony

    2017-10-01

    A syrinx is a fluid-filled cavity within the spinal cord. They can lead to a variety of symptoms, including limb weakness and back pain. Incidental finding of syringomyelia provides a challenge for clinicians due to the wide variety of possible symptoms. In military aviation, neurological findings in pilots can result in extensive investigation that can lead to potentially invasive management. Conversely, the potential for chronic progression of a spinal syrinx and subsequent neurological deterioration makes early identification critical. Ultimately, the discovery of a lesion may have implications for flying status and operational capability. A 25-yr-old man working as a navy Seahawk helicopter pilot presented with episodes of right arm paraesthesia and pain between the scapulae. On at least one occasion, these symptoms woke him at night. Upon magnetic resonance imaging, dilatation of the central canal in a syrinx-like pattern in the lower cervical region was noted. Neurology review suggested the finding was persistent and unlikely to be responsible for his symptoms. No surgical input was recommended. His symptoms were attributed to mild cervical spondylosis, which resolved with ongoing physiotherapy, and he was returned to flying status. This case highlights several issues involved with the incidental finding of a syringomyelia. Surgical intervention has been known to worsen symptoms. Conversely, studies have identified minimal radiological progression in cases of idiopathic syringomyelia, with fewer individuals displaying neurological deterioration. For aircrew, potentially unnecessary neurosurgical intervention poses risks to a flying career and overall operational capability.Schiemer A. Idiopathic syringomyelia in a military helicopter pilot. Aerosp Med Hum Perform. 2017; 88(10):962-965.

  4. Helicopter flight simulation motion platform requirements

    Schroeder, Jeffery Allyn

    Flight simulators attempt to reproduce in-flight pilot-vehicle behavior on the ground. This reproduction is challenging for helicopter simulators, as the pilot is often inextricably dependent on external cues for pilot-vehicle stabilization. One important simulator cue is platform motion; however, its required fidelity is unknown. To determine the required motion fidelity, several unique experiments were performed. A large displacement motion platform was used that allowed pilots to fly tasks with matched motion and visual cues. Then, the platform motion was modified to give cues varying from full motion to no motion. Several key results were found. First, lateral and vertical translational platform cues had significant effects on fidelity. Their presence improved performance and reduced pilot workload. Second, yaw and roll rotational platform cues were not as important as the translational platform cues. In particular, the yaw rotational motion platform cue did not appear at all useful in improving performance or reducing workload. Third, when the lateral translational platform cue was combined with visual yaw rotational cues, pilots believed the platform was rotating when it was not. Thus, simulator systems can be made more efficient by proper combination of platform and visual cues. Fourth, motion fidelity specifications were revised that now provide simulator users with a better prediction of motion fidelity based upon the frequency responses of their motion control laws. Fifth, vertical platform motion affected pilot estimates of steady-state altitude during altitude repositionings. This refutes the view that pilots estimate altitude and altitude rate in simulation solely from visual cues. Finally, the combined results led to a general method for configuring helicopter motion systems and for developing simulator tasks that more likely represent actual flight. The overall results can serve as a guide to future simulator designers and to today's operators.

  5. The vibro-acoustic response and analysis of a full-scale aircraft fuselage section for interior noise reduction.

    Herdic, Peter C; Houston, Brian H; Marcus, Martin H; Williams, Earl G; Baz, Amr M

    2005-06-01

    The surface and interior response of a Cessna Citation fuselage section under three different forcing functions (10-1000 Hz) is evaluated through spatially dense scanning measurements. Spatial Fourier analysis reveals that a point force applied to the stiffener grid provides a rich wavenumber response over a broad frequency range. The surface motion data show global structural modes (approximately 450 Hz). Some evidence of Bloch wave motion is observed, revealing classical stop/pass bands associated with stiffener periodicity. The interior response (approximately interior cavity. Local intrapanel responses (approximately > 150 Hz) of the fuselage provide a broadband volume velocity source that strongly excites a high density of interior modes. Mode coupling between the structural response and the interior modes appears to be negligible due to a lack of frequency proximity and mismatches in the spatial distribution. A high degree-of-freedom finite element model of the fuselage section was developed as a predictive tool. The calculated response is in good agreement with the experimental result, yielding a general model development methodology for accurate prediction of structures with moderate to high complexity.

  6. Progress report on INEL full flow drag screen

    Arave, A.E.; Colson, J.B.; Fincke, J.R.

    1977-01-01

    The objective in developing a full flow drag screen is to obtain a total momentum flux measurement which when combined with a suitable independent velocity or density measurement will yield a total mass flux. The major design considerations are predicated by the fact that an accurate momentum flux measurement must be made over a wide range of flow conditions. The device should exhibit a constant calibration regardless of Reynolds number, void fraction, slip ratio, or flow regime. The dynamics of drag devices are well understood in single-phase flows. This is not true for two-phase flows. The present development program is directed toward gaining an understanding of the dynamics of drag devices which sample the total area of a pipe in two-phase flow and developing a method for deducing mass flow rate using such a device. Various geometric arrangements are to be investigated. Testing to date has shown excellent results using a round wire mesh screen in the Semiscale air/water loop. Future air/water testing will include perforated plates and wire meshes with both rectangular and diamond shaped cross sections. Analytical models of the hydrodynamics of the drag screen as well as the associated density or velocity measuring device are being used to select the optimum configuration. Alternate force sensing methods are also being considered. These include single and multiple transducer arrangements. Multistage springs and pressure drop across the body are to be evaluated for extending the dynamic range of the drag body

  7. The Overall Drag Losses For A Combination of Bodies

    Sabah Al-Janabi

    2013-05-01

    Full Text Available The objective of this work is to obtain better understanding of the flow over a combination of bluff bodies in close enough proximity to strongly interact with each other. This interaction is often beneficial in that the drag of the overall system is reduced. Proto-types for this problem come from tractor- trailer and missiles, and from various add-on devices designed to reduce their drag. Thus, an experimental investigation was carried out by placing  conical frontal bodies having a base diameter of 0.65 cylinder diameter with different vertex angles (30°, 50°, 70°, and 90°. It was found that, the bluffer cone with 90° vertex angle gives the best minimum drag, which is 31% lower than the drag of the isolated cylinder. Also an interesting phenomenon was observed in that, the minimum drags for all combinations are obtained at the same gap ratio (i.e.at g/d2= 0.365.

  8. A Conventional Liner Acoustic/Drag Interaction Benchmark Database

    Howerton, Brian M.; Jones, Michael G.

    2017-01-01

    The aerodynamic drag of acoustic liners has become a significant topic in the design of such for aircraft noise applications. In order to evaluate the benefits of concepts designed to reduce liner drag, it is necessary to establish the baseline performance of liners employing the typical design features of conventional configurations. This paper details a set of experiments in the NASA Langley Grazing Flow Impedance Tube to quantify the relative drag of a number of perforate-over-honeycomb liner configurations at flow speeds of M=0.3 and 0.5. These conventional liners are investigated to determine their resistance factors using a static pressure drop approach. Comparison of the resistance factors gives a relative measurement of liner drag. For these same flow conditions, acoustic measurements are performed with tonal excitation from 400 to 3000 Hz at source sound pressure levels of 140 and 150 dB. Educed impedance and attenuation spectra are used to determine the interaction between acoustic performance and drag.

  9. Relativistic Gas Drag on Dust Grains and Implications

    Hoang, Thiem, E-mail: thiemhoang@kasi.re.kr [Korea Astronomy and Space Science Institute, Daejeon 34055 (Korea, Republic of); Korea University of Science and Technology, Daejeon, 34113 (Korea, Republic of)

    2017-09-20

    We study the drag force on grains moving at relativistic velocities through interstellar gas and explore its application. First, we derive a new analytical formula of the drag force at high energies and find that it is significantly reduced compared to the classical model. Second, we apply the obtained drag force to calculate the terminal velocities of interstellar grains by strong radiation sources such as supernovae and active galactic nuclei (AGNs). We find that grains can be accelerated to relativistic velocities by very luminous AGNs. We then quantify the deceleration of relativistic spacecraft proposed by the Breakthrough Starshot initiative due to gas drag on a relativistic lightsail. We find that the spacecraft’s decrease in speed is negligible because of the suppression of gas drag at relativistic velocities, suggesting that the lightsail may be open for communication during its journey to α Centauri without causing a considerable delay. Finally, we show that the damage to relativistic thin lightsails by interstellar dust is a minor effect.

  10. Drag reduction in channel flow using nonlinear control

    Keefe, Laurence R.

    1993-01-01

    Two nonlinear control schemes have been applied to the problem of drag reduction in channel flow. Both schemes have been tested using numerical simulations at a mass flux Reynolds numbers of 4408, utilizing 2D nonlinear neutral modes for goal dynamics. The OGY-method, which requires feedback, reduces drag to 60-80 percent of the turbulent value at the same Reynolds number, and employs forcing only within a thin region near the wall. The H-method, or model-based control, fails to achieve any drag reduction when starting from a fully turbulent initial condition, but shows potential for suppressing or retarding laminar-to-turbulent transition by imposing instead a transition to a low drag, nonlinear traveling wave solution to the Navier-Stokes equation. The drag in this state corresponds to that achieved by the OGY-method. Model-based control requires no feedback, but in experiments to date has required the forcing be imposed within a thicker layer than the OGY-method. Control energy expenditures in both methods are small, representing less than 0.1 percent of the uncontrolled flow's energy.

  11. Creating drag and lift curves from soccer trajectories

    Goff, John Eric; Kelley, John; Hobson, Chad M.; Seo, Kazuya; Asai, Takeshi; Choppin, S. B.

    2017-07-01

    Trajectory analysis is an alternative to using wind tunnels to measure a soccer ball’s aerodynamic properties. It has advantages over wind tunnel testing such as being more representative of game play. However, previous work has not presented a method that produces complete, speed-dependent drag and lift coefficients. Four high-speed cameras in stereo-calibrated pairs were used to measure the spatial co-ordinates for 29 separate soccer trajectories. Those trajectories span a range of launch speeds from 9.3 to 29.9 m s-1. That range encompasses low-speed laminar flow of air over a soccer ball, through the drag crises where air flow is both laminar and turbulent, and up to high-speed turbulent air flow. Results from trajectory analysis were combined to give speed-dependent drag and lift coefficient curves for the entire range of speeds found in the 29 trajectories. The average root mean square error between the measured and modelled trajectory was 0.028 m horizontally and 0.034 m vertically. The drag and lift crises can be observed in the plots of drag and lift coefficients respectively.

  12. Theory of Coulomb drag for massless Dirac fermions

    Carrega, M; Principi, A; Polini, M; Tudorovskiy, T; Katsnelson, M I

    2012-01-01

    Coulomb drag between two unhybridized graphene sheets separated by a dielectric spacer has recently attracted considerable theoretical interest. We first review, for the sake of completeness, the main analytical results which have been obtained by other authors. We then illustrate pedagogically the minimal theory of Coulomb drag between two spatially separated two-dimensional systems of massless Dirac fermions which are both away from the charge-neutrality point. This relies on second-order perturbation theory in the screened interlayer interaction and on Boltzmann-transport theory. In this theoretical framework and in the low-temperature limit, we demonstrate that, to leading (i.e. quadratic) order in temperature, the drag transresistivity is completely insensitive to the precise intralayer momentum-relaxation mechanism (i.e. to the functional dependence of the transport scattering time on energy). We also provide analytical results for the low-temperature drag transresistivity for both cases of ‘thick’ and ‘thin’ spacers and for arbitrary values of the dielectric constants of the media surrounding the two Dirac-fermion layers. Finally, we present numerical results for the low-temperature drag transresistivity for the case when one of the media surrounding the Dirac-fermion layers has a frequency-dependent dielectric constant. We conclude by suggesting an experiment that can potentially allow for the observation of departures from the canonical quadratic-in-temperature behavior of the transresistivity. (paper)

  13. Cost model relationships between textile manufacturing processes and design details for transport fuselage elements

    Metschan, Stephen L.; Wilden, Kurtis S.; Sharpless, Garrett C.; Andelman, Rich M.

    1993-01-01

    Textile manufacturing processes offer potential cost and weight advantages over traditional composite materials and processes for transport fuselage elements. In the current study, design cost modeling relationships between textile processes and element design details were developed. Such relationships are expected to help future aircraft designers to make timely decisions on the effect of design details and overall configurations on textile fabrication costs. The fundamental advantage of a design cost model is to insure that the element design is cost effective for the intended process. Trade studies on the effects of processing parameters also help to optimize the manufacturing steps for a particular structural element. Two methods of analyzing design detail/process cost relationships developed for the design cost model were pursued in the current study. The first makes use of existing databases and alternative cost modeling methods (e.g. detailed estimating). The second compares design cost model predictions with data collected during the fabrication of seven foot circumferential frames for ATCAS crown test panels. The process used in this case involves 2D dry braiding and resin transfer molding of curved 'J' cross section frame members having design details characteristic of the baseline ATCAS crown design.

  14. Flight demonstration of aircraft fuselage and bulkhead monitoring using optical fiber distributed sensing system

    Wada, Daichi; Igawa, Hirotaka; Tamayama, Masato; Kasai, Tokio; Arizono, Hitoshi; Murayama, Hideaki; Shiotsubo, Katsuya

    2018-02-01

    We have developed an optical fiber distributed sensing system based on optical frequency domain reflectometry (OFDR) that uses long-length fiber Bragg gratings (FBGs). This technique obtains strain data not as a point data from an FBG but as a distributed profile within the FBG. This system can measure the strain distribution profile with an adjustable high spatial resolution of the mm or sub-mm order in real-time. In this study, we applied this OFDR-FBG technique to a flying test bed that is a mid-sized jet passenger aircraft. We conducted flight tests and monitored the structural responses of a fuselage stringer and the bulkhead of the flying test bed during flights. The strain distribution variations were successfully monitored for various events including taxiing, takeoff, landing and several other maneuvers. The monitoring was effective not only for measuring the strain amplitude applied to the individual structural parts but also for understanding the characteristics of the structural responses in accordance with the flight maneuvers. We studied the correlations between various maneuvers and strains to explore the relationship between the operation and condition of aircraft.

  15. Testing and Analysis of a Composite Non-Cylindrical Aircraft Fuselage Structure . Part II; Severe Damage

    Przekop, Adam; Jegley, Dawn C.; Lovejoy, Andrew E.; Rouse, Marshall; Wu, Hsi-Yung T.

    2016-01-01

    The Environmentally Responsible Aviation Project aimed to develop aircraft technologies enabling significant fuel burn and community noise reductions. Small incremental changes to the conventional metallic alloy-based 'tube and wing' configuration were not sufficient to achieve the desired metrics. One airframe concept identified by the project as having the potential to dramatically improve aircraft performance was a composite-based hybrid wing body configuration. Such a concept, however, presented inherent challenges stemming from, among other factors, the necessity to transfer wing loads through the entire center fuselage section which accommodates a pressurized cabin confined by flat or nearly flat panels. This paper discusses a finite element analysis and the testing of a large-scale hybrid wing body center section structure developed and constructed to demonstrate that the Pultruded Rod Stitched Efficient Unitized Structure concept can meet these challenging demands of the next generation airframes. Part II of the paper considers the final test to failure of the test article in the presence of an intentionally inflicted severe discrete source damage under the wing up-bending loading condition. Finite element analysis results are compared with measurements acquired during the test and demonstrate that the hybrid wing body test article was able to redistribute and support the required design loads in a severely damaged condition.

  16. Influence of artificial tip perturbation on asymmetric vortices flow over a chined fuselage

    Shi Wei

    2015-08-01

    Full Text Available An experimental study was conducted with the aim of understanding behavior of asymmetric vortices flow over a chined fuselage. The tests were carried out in a wind tunnel at Reynolds number of 1.87 × 105 under the conditions of high angles of attack and zero angle of sideslip. The results show that leeward vortices flow becomes asymmetric vortices flow when angle of attack increases over 20°. The asymmetric vortices flow is asymmetry of two forebody vortices owing to the increase of angle of attack but not asymmetry of vortex breakdown which appears when angle of attack is above 35°. Asymmetric vortices flow is sensitive to tip perturbation and is non-deterministic due to randomly distributed natural minute geometrical irregularities on the nose tip within machining tolerance. Deterministic asymmetric vortices flow can be obtained by attaching artificial tip perturbation which can trigger asymmetric vortices flow and decide asymmetric vortices flow pattern. Triggered by artificial tip perturbation, the vortex on the same side with perturbation is in a higher position, and the other vortex on the opposite side is in a lower position. Vortex suction on the lower vortex side is larger, which corresponds to a side force pointing to the lower vortex side.

  17. Fuselage Versus Subcomponent Panel Response Correlation Based on ABAQUS Explicit Progressive Damage Analysis Tools

    Gould, Kevin E.; Satyanarayana, Arunkumar; Bogert, Philip B.

    2016-01-01

    Analysis performed in this study substantiates the need for high fidelity vehicle level progressive damage analyses (PDA) structural models for use in the verification and validation of proposed sub-scale structural models and to support required full-scale vehicle level testing. PDA results are presented that capture and correlate the responses of sub-scale 3-stringer and 7-stringer panel models and an idealized 8-ft diameter fuselage model, which provides a vehicle level environment for the 7-stringer sub-scale panel model. Two unique skin-stringer attachment assumptions are considered and correlated in the models analyzed: the TIE constraint interface versus the cohesive element (COH3D8) interface. Evaluating different interfaces allows for assessing a range of predicted damage modes, including delamination and crack propagation responses. Damage models considered in this study are the ABAQUS built-in Hashin procedure and the COmplete STress Reduction (COSTR) damage procedure implemented through a VUMAT user subroutine using the ABAQUS/Explicit code.

  18. Analysis and Testing of a Composite Fuselage Shield for Open Rotor Engine Blade-Out Protection

    Pereira, J. Michael; Emmerling, William; Seng, Silvia; Frankenberger, Charles; Ruggeri, Charles R.; Revilock, Duane M.; Carney, Kelly S.

    2016-01-01

    The Federal Aviation Administration is working with the European Aviation Safety Agency to determine the certification base for proposed new engines that would not have a containment structure on large commercial aircraft. Equivalent safety to the current fleet is desired by the regulators, which means that loss of a single fan blade will not cause hazard to the Aircraft. The NASA Glenn Research Center and The Naval Air Warfare Center (NAWC), China Lake, collaborated with the FAA Aircraft Catastrophic Failure Prevention Program to design and test lightweight composite shields for protection of the aircraft passengers and critical systems from a released blade that could impact the fuselage. LS-DYNA® was used to predict the thickness of the composite shield required to prevent blade penetration. In the test, two composite blades were pyrotechnically released from a running engine, each impacting a composite shield with a different thickness. The thinner shield was penetrated by the blade and the thicker shield prevented penetration. This was consistent with pre-test LS-DYNA predictions. This paper documents the analysis conducted to predict the required thickness of a composite shield, the live fire test from the full scale rig at NAWC China Lake and describes the damage to the shields as well as instrumentation results.

  19. Validated Feasibility Study of Integrally Stiffened Metallic Fuselage Panels for Reducing Manufacturing Costs

    Pettit, R. G.; Wang, J. J.; Toh, C.

    2000-01-01

    The continual need to reduce airframe cost and the emergence of high speed machining and other manufacturing technologies has brought about a renewed interest in large-scale integral structures for aircraft applications. Applications have been inhibited, however, because of the need to demonstrate damage tolerance, and by cost and manufacturing risks associated with the size and complexity of the parts. The Integral Airframe Structures (IAS) Program identified a feasible integrally stiffened fuselage concept and evaluated performance and manufacturing cost compared to conventional designs. An integral skin/stiffener concept was produced both by plate hog-out and near-net extrusion. Alloys evaluated included 7050-T7451 plate, 7050-T74511 extrusion, 6013-T6511 extrusion, and 7475-T7351 plate. Mechanical properties, structural details, and joint performance were evaluated as well as repair, static compression, and two-bay crack residual strength panels. Crack turning behavior was characterized through panel tests and improved methods for predicting crack turning were developed. Manufacturing cost was evaluated using COSTRAN. A hybrid design, made from high-speed machined extruded frames that are mechanically fastened to high-speed machined plate skin/stringer panels, was identified as the most cost-effective manufacturing solution. Recurring labor and material costs of the hybrid design are up to 61 percent less than the current technology baseline.

  20. Transonic airfoil design for helicopter rotor applications

    Hassan, Ahmed A.; Jackson, B.

    1989-01-01

    Despite the fact that the flow over a rotor blade is strongly influenced by locally three-dimensional and unsteady effects, practical experience has always demonstrated that substantial improvements in the aerodynamic performance can be gained by improving the steady two-dimensional charateristics of the airfoil(s) employed. The two phenomena known to have great impact on the overall rotor performance are: (1) retreating blade stall with the associated large pressure drag, and (2) compressibility effects on the advancing blade leading to shock formation and the associated wave drag and boundary-layer separation losses. It was concluded that: optimization routines are a powerful tool for finding solutions to multiple design point problems; the optimization process must be guided by the judicious choice of geometric and aerodynamic constraints; optimization routines should be appropriately coupled to viscous, not inviscid, transonic flow solvers; hybrid design procedures in conjunction with optimization routines represent the most efficient approach for rotor airfroil design; unsteady effects resulting in the delay of lift and moment stall should be modeled using simple empirical relations; and inflight optimization of aerodynamic loads (e.g., use of variable rate blowing, flaps, etc.) can satisfy any number of requirements at design and off-design conditions.

  1. Acoustic Liner Drag: Measurements on Novel Facesheet Perforate Geometries

    Howerton, Brian M.; Jones, Michael G.

    2016-01-01

    Interest in characterization of the aerodynamic drag of acoustic liners has increased in the past several years. This paper details experiments in the NASA Langley Grazing Flow Impedance Tube to quantify the relative drag of several perforate-over-honeycomb liner configurations at flow speeds of centerline flow Mach number equals 0.3 and 0.5. Various perforate geometries and orientations are investigated to determine their resistance factors using a static pressure drop approach. Comparison of these resistance factors gives a relative measurement of liner drag. For these same flow conditions, acoustic measurements are performed with tonal excitation from 400 to 3000 hertz at source sound pressure levels of 140 and 150 decibels. Educed impedance and attenuation spectra are used to determine the impact of variations in perforate geometry on acoustic performance.

  2. Drag Reduction by Riblets & Sharkskin Denticles: A Numerical Study

    Boomsma, Aaron

    Riblet films are a passive method of turbulent boundary layer control that can reduce viscous drag. They have been studied with great detail for over 30 years. Although common riblet applications include flows with Adverse Pressure Gradients (APG), nearly all research thus far has been performed in channel flows. Recent research has provided motivation to study riblets in more complicated turbulent flows with claims that riblet drag reduction can double in mild APG common to airfoils at moderate angles of attack. Therefore, in this study, we compare drag reduction by scalloped riblet films between riblets in a zero pressure gradient and those in a mild APG using high-resolution large eddy simulations. In order to gain a fundamental understanding of the relationship between drag reduction and pressure gradient, we simulated several different riblet sizes that encompassed a broad range of s + (riblet width in wall units), similarly to many experimental studies. We found that there was only a slight improvement in drag reduction for riblets in the mild APG. We also observed that peak values of streamwise turbulence intensity, turbulent kinetic energy, and streamwise vorticity scale with riblet width. Primary Reynolds shear stresses and turbulence kinetic energy production however scale with the ability of the riblet to reduce skin-friction. Another turbulent roughness of similar shape and size to riblets is sharkskin. The hydrodynamic function of sharkskin has been under investigation for the past 30 years. Current literature conflicts on whether sharkskin is able to reduce skin friction similarly to riblets. To contribute insights toward reconciling these conflicting views, Direct Numerical Simulations (DNS) are carried out to obtain detailed flow fields around realistic denticles. A sharp interface immersed boundary method is employed to simulate two arrangements of actual sharkskin denticles (from Isurus oxyrinchus) in a turbulent boundary layer at Retau ≈ 180

  3. On the energy economics of air lubrication drag reduction

    Simo A. Mäkiharju

    2012-12-01

    Full Text Available Air lubrication techniques for frictional drag reduction on ships have been proposed by numerous researchers since the 19th century. However, these techniques have not been widely adopted as questions persist about their drag reduction performance beyond the laboratory, as well as energy and economic cost-benefit. This paper draws on data from the literature to consider the suitability of air lubrication for large ocean going and U.S. Great Lakes ships, by establishing the basic energy economic calculations and presenting results for a hypothetical air lubricated ship. All the assumptions made in the course of the analysis are clearly stated so that they can be refined when considering application of air lubrication to a specific ship. The analysis suggests that, if successfully implemented, both air layer and partial cavity drag reduction could lead to net energy savings of 10 to 20%, with corresponding reductions in emissions.

  4. Flexural phonon limited phonon drag thermopower in bilayer graphene

    Ansari, Mohd Meenhaz; Ashraf, SSZ

    2018-05-01

    We investigate the phonon drag thermopower from flexural phonons as a function of electron temperature and carrier concentration in the Bloch-Gruneisen regime in non-strained bilayer graphene using Boltzmann transport equation approach. The flexural phonons are expected to be the major source of intrinsic scattering mechanism in unstrained bilayer graphene due to their large density. The flexural phonon modes dispersion relation is quadratic so these low energy flexural phonons abound at room temperature and as a result deform the bilayer graphene sheet in the out of plane direction and affects the transport properties. We also produce analytical result for phonon-drag thermopower from flexural phonons and find that phonon-drag thermopower depicts T2 dependence on temperature and n-1 on carrier concentration.

  5. Spanwise drag variation on low Re wings -- revisited

    Yang, Shanling; Spedding, Geoffrey

    2011-11-01

    Aerodynamic performance measurement and prediction of airfoils and wings at chord Reynolds numbers below 105 is both difficult and increasingly important in application to small-scale aircraft. Not only are the aerodynamics strongly affected by the dynamics of the unstable laminar boundary layer but the flow is decreasingly likely to be two-dimensional as Re decreases. The spanwise variation of the flow along a two-dimensional geometry is often held to be responsible for the large variations in measured profile drag coefficient. Here we measure local two-dimensional drag coefficients along a finite wing using non-intrusive PIV methods. Variations in Cd (y) can be related to local flow variations on the wing itself. Integrated values can be compared with force balance data, and the proper description of drag components at low Re will be discussed.

  6. The contact drag of towed demersal fishing gear components

    O'Neill, F. G.; Summerbell, K.; Ivanović, A.

    2018-01-01

    The contact demersal towed fishing gears make with the seabed can lead to penetration of the substrate, lateral displacement of the sediment and a pressure field transmitted through the sediment. It will also contribute to the overall drag of the fishing gear. Consequently, there can be environmental effects such as habitat alteration and benthic mortality, and impacts to the fuel efficiency of the fishing operation which will affect emissions of nitrogen oxides, sulphur oxides and greenhouse gases such as CO2. Here we present the results of experimental trials that measure the contact drag of a range of elements that represent some of the components of towed demersal gears that are in contact with the seabed. We show that the contact drag of the gear components depends on their weight, geometry, the type of sediment on which they are towed and whether they are rolling or not. As expected, the contact drag of each gear component increases as its weight increases and the drag of fixed elements is greater than that of the rolling ones. The dependence on aspect ratio is more complex and the drag (per unit area) of narrow cylinders is less than that of wider ones when they roll on the finer sediment or are fixed (not permitted to roll) on the coarser sediment. When they roll on the coarse sediment there is no dependence on aspect ratio. Our results also suggest that fixed components may penetrate the seabed to a lesser depth when they are towed at higher speeds but when they roll there is no such relationship.

  7. Locus of the apices of projectile trajectories under constant drag

    Hernández-Saldaña, H.

    2017-11-01

    Using the hodograph method, we present an analytical solution for projectile coplanar motion under constant drag, parametrised by the velocity angle. We find the locus formed by the apices of the projectile trajectories, and discuss its implementation for the motion of a particle on an inclined plane in presence of Coulomb friction. The range and time of flight are obtained numerically, and we find that the optimal launching angle is smaller than in the drag-free case. This is a good example of a problem with constant dissipation of energy that includes curvature; it is appropriate for intermediate courses of mechanics.

  8. The effects of Poynting–Robertson drag on solar sails

    F.A. Abd El-Salam

    2018-06-01

    Full Text Available In the present work, the concept of solar sailing and its developing spacecraft are presented. The effects of Poynting–Robertson drag on solar sails are considered. Some analytical control laws with some mentioned input constraints for optimizing solar sails dynamics in heliocentric orbit using Lagrange’s planetary equations are obtained. Optimum force vector in a required direction is maximized by deriving optimal sail cone angle. New control laws that maximize thrust to obtain certain required maximization in some particular orbital element are obtained. Keywords: Poynting–Robertson drag, Solar sail, Control laws, Optimal sail, Cone angle

  9. A hypersonic lift mechanism with decoupled lift and drag surfaces

    Xu, YiZhe; Xu, ZhiQi; Li, ShaoGuang; Li, Juan; Bai, ChenYuan; Wu, ZiNiu

    2013-05-01

    In the present study, we propose a novel lift mechanism for which the lifting surface produces only lift. This is achieved by mounting a two-dimensional shock-shock interaction generator below the lifting surface. The shock-shock interaction theory in conjunction with a three dimensional correction and checked with computational fluid dynamics (CFD) is used to analyze the lift and drag forces as function of the geometrical parameters and inflow Mach number. Through this study, though limited to only inviscid flow, we conclude that it is possible to obtain a high lift to drag ratio by suitably arranging the shock interaction generator.

  10. Development of drag disk and turbines at the INEL

    Goodrich, L.D.; Edson, J.L.; Averill, R.H.

    1984-01-01

    One of the parameters that must be measured in nuclear safety research is mass flow rate. The reactor environment associated with two-phase flow makes this measurement difficult. To accomplish this at the Idaho National Engineering Laboratory, a drag disk and turbine transducer conbination was developed. These transducers can withstand >2000 h of continuous operation in the reactor environment. Mechanical problems have been solved with these transducers to the point where the electrical coils are now the limiting factor on lifetime. This paper presents the results of the development of the drag disk and turbine with problems and solutions pointed out

  11. Drag force in a strongly coupled anisotropic plasma

    Chernicoff, Mariano; Fernández, Daniel; Mateos, David; Trancanelli, Diego

    2012-08-01

    We calculate the drag force experienced by an infinitely massive quark propagating at constant velocity through an anisotropic, strongly coupled {N} = 4 plasma by means of its gravity dual. We find that the gluon cloud trailing behind the quark is generally misaligned with the quark velocity, and that the latter is also misaligned with the force. The drag coefficient μ can be larger or smaller than the corresponding isotropic value depending on the velocity and the direction of motion. In the ultra-relativistic limit we find that generically μ ∝ p. We discuss the conditions under which this behaviour may extend to more general situations.

  12. Control of the electromagnetic drag using fluctuating light fields

    Pastor, Víctor J. López; Marqués, Manuel I.

    2018-05-01

    An expression for the electromagnetic drag force experienced by an electric dipole in a light field consisting of a monochromatic plane wave with polarization and phase randomly fluctuating is obtained. The expression explicitly considers the transformations of the field and frequency due to the Doppler shift and the change of the polarizability response of the electric dipole. The conditions to be fulfilled by the polarizability of the dipole in order to obtain a positive, a null, and a negative drag coefficient are analytically determined and checked against numerical simulations for the dynamics of a silver nanoparticle. The theoretically predicted diffusive, superdiffusive, and exponentially accelerated dynamical regimes are numerically confirmed.

  13. Determination of the drag resistance coefficients of different vehicles

    Fahsl, Christoph; Vogt, Patrik

    2018-05-01

    While it has been demonstrated how air resistance could be analyzed by using mobile devices, this paper demonstrates a method of how to determine the drag resistance coefficient c of a commercial automobile by using the acceleration sensor of a smartphone or tablet. In an academic context, the drag resistance is often mentioned, but little attention is paid to quantitative measurements. This experiment was driven by the fact that this physical value is most certainly neglected because of its difficult measurability. In addition to that, this experiment gives insights on how the aerodynamic factor of an automobile affects the energy dissipation and thus how much power is required by automobile transportation.

  14. Performance Analysis of a Utility Helicopter with Standard and Advanced Rotors

    Yeo, Hyeonsoo; Bousman, William G; Johnson, Wayne

    2002-01-01

    Flight test measurements of the performance of the UH-60 Black Hawk helicopter with both standard and advanced rotors are compared with calculations obtained using the comprehensive helicopter analysis CAMRAD II...

  15. Amplifying the helicopter drift in a conformal HMD

    Schmerwitz, Sven; Knabl, Patrizia M.; Lueken, Thomas; Doehler, Hans-Ullrich

    2016-05-01

    Helicopter operations require a well-controlled and minimal lateral drift shortly before ground contact. Any lateral speed exceeding this small threshold can cause a dangerous momentum around the roll axis, which may cause a total roll over of the helicopter. As long as pilots can observe visual cues from the ground, they are able to easily control the helicopter drift. But whenever natural vision is reduced or even obscured, e.g. due to night, fog, or dust, this controllability diminishes. Therefore helicopter operators could benefit from some type of "drift indication" that mitigates the influence of a degraded visual environment. Generally humans derive ego motion by the perceived environmental object flow. The visual cues perceived are located close to the helicopter, therefore even small movements can be recognized. This fact was used to investigate a modified drift indication. To enhance the perception of ego motion in a conformal HMD symbol set the measured movement was used to generate a pattern motion in the forward field of view close or on the landing pad. The paper will discuss the method of amplified ego motion drift indication. Aspects concerning impact factors like visualization type, location, gain and more will be addressed. Further conclusions from previous studies, a high fidelity experiment and a part task experiment, will be provided. A part task study will be presented that compared different amplified drift indications against a predictor. 24 participants, 15 holding a fixed wing license and 4 helicopter pilots, had to perform a dual task on a virtual reality headset. A simplified control model was used to steer a "helicopter" down to a landing pad while acknowledging randomly placed characters.

  16. Development of Helicopter Capabilities in the U.S. Army During the Korean and Vietnam Wars

    2016-06-10

    28. 14 and could land almost in any place bigger than its rotor diameter. It demonstrated the nature of the helicopter . Nevertheless, rotorcraft of... composition of airmobile units, and 67 methodology of helicopter use on the battlefield. The study seems to cover a broad spectrum of knowledge and...can be focused on the one of several aspects: employment of armored helicopters , land mobility vs helicopter mobility, composition of airmobile units

  17. 14 CFR Appendix B to Part 27 - Airworthiness Criteria for Helicopter Instrument Flight

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Airworthiness Criteria for Helicopter... Appendix B to Part 27—Airworthiness Criteria for Helicopter Instrument Flight I. General. A normal category helicopter may not be type certificated for operation under the instrument flight rules (IFR) of this chapter...

  18. 14 CFR 61.161 - Aeronautical experience: Rotorcraft category and helicopter class rating.

    2010-01-01

    ... category and helicopter class rating. 61.161 Section 61.161 Aeronautics and Space FEDERAL AVIATION... helicopter class rating. (a) A person who is applying for an airline transport pilot certificate with a rotorcraft category and helicopter class rating, must have at least 1,200 hours of total time as a pilot that...

  19. 14 CFR Appendix B to Part 29 - Airworthiness Criteria for Helicopter Instrument Flight

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Airworthiness Criteria for Helicopter... Appendix B to Part 29—Airworthiness Criteria for Helicopter Instrument Flight I. General. A transport category helicopter may not be type certificated for operation under the instrument flight rules (IFR) of...

  20. 14 CFR 135.271 - Helicopter hospital emergency medical evacuation service (HEMES).

    2010-01-01

    ... 14 Aeronautics and Space 3 2010-01-01 2010-01-01 false Helicopter hospital emergency medical....271 Helicopter hospital emergency medical evacuation service (HEMES). (a) No certificate holder may... certificate holder may assign a helicopter flight crewmember, and no flight crewmember may accept an...

  1. Differences in physical workload between military helicopter pilots and cabin crew

    van den Oord, Marieke H. A.; Sluiter, Judith K.; Frings-Dresen, Monique H. W.

    2014-01-01

    The 1-year prevalence of regular or continuous neck pain in military helicopter pilots of the Dutch Defense Helicopter Command (DHC) is 20%, and physical work exposures have been suggested as risk factors. Pilots and cabin crew perform different tasks when flying helicopters. The aims of the current

  2. 46 CFR 109.575 - Accumulation of liquids on helicopter decks.

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Accumulation of liquids on helicopter decks. 109.575... DRILLING UNITS OPERATIONS Miscellaneous § 109.575 Accumulation of liquids on helicopter decks. The master or person in charge shall ensure that no liquids are allowed to accumulate on the helicopter decks. ...

  3. U.S. Army Primary Helicopter School Training Program Performance Norms.

    Barnes, John A.; Statham, Flavous D.

    The Helicopter Pilot Training Program of the Army differs from those of the other services in concept. It takes nonpilot servicemen and trains them to fly helicopters. The study provides normative performance data for a pilot trainee in an army light-observation helicopter as a first step toward establishing normative data for pilot performance in…

  4. 46 CFR 131.950 - Placard on lifesaving signals and helicopter recovery.

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Placard on lifesaving signals and helicopter recovery... SUPPLY VESSELS OPERATIONS Miscellaneous § 131.950 Placard on lifesaving signals and helicopter recovery..., Chapter V, of SOLAS 74/83; and (2) In helicopter recovery. (b) The signals must be employed by vessels or...

  5. 78 FR 40055 - Airworthiness Directives; Agusta S.p.A. Helicopters

    2013-07-03

    .... We also estimate that it would take about 3 work-hours per helicopter to rework the top cable cutter... helicopter to rework the top cable cutter assembly, $9,085 per helicopter to replace the top cable cutter... installing a WSPS upper installation, P/N 4G9540A00111, either: (i) Rework the top cable cutter assembly, P/N...

  6. 77 FR 52270 - Airworthiness Directives; Agusta S.p.A. Helicopters

    2012-08-29

    ... would take about three work- hours per helicopter to rework the top cable-cutter assembly, one work... would be $255 per helicopter to rework the top cable-cutter assembly, $9,085 per helicopter to replace... 4G9540A00111, either: (i) Rework the top cable cutter assembly, P/N 423-83001-1, in accordance with the...

  7. Helicopter Parenting: The Effect of an Overbearing Caregiving Style on Peer Attachment and Self-Efficacy

    van Ingen, Daniel J.; Freiheit, Stacy R.; Steinfeldt, Jesse A.; Moore, Linda L.; Wimer, David J.; Knutt, Adelle D.; Scapinello, Samantha; Roberts, Amber

    2015-01-01

    Helicopter parenting, an observed phenomenon on college campuses, may adversely affect college students. The authors examined how helicopter parenting is related to self-efficacy and peer relationships among 190 undergraduate students ages 16 to 28 years. Helicopter parenting was associated with low self-efficacy, alienation from peers, and a lack…

  8. Nonlinear Finite Element Analysis of a Composite Non-Cylindrical Pressurized Aircraft Fuselage Structure

    Przekop, Adam; Wu, Hsi-Yung T.; Shaw, Peter

    2014-01-01

    The Environmentally Responsible Aviation Project aims to develop aircraft technologies enabling significant fuel burn and community noise reductions. Small incremental changes to the conventional metallic alloy-based 'tube and wing' configuration are not sufficient to achieve the desired metrics. One of the airframe concepts that might dramatically improve aircraft performance is a composite-based hybrid wing body configuration. Such a concept, however, presents inherent challenges stemming from, among other factors, the necessity to transfer wing loads through the entire center fuselage section which accommodates a pressurized cabin confined by flat or nearly flat panels. This paper discusses a nonlinear finite element analysis of a large-scale test article being developed to demonstrate that the Pultruded Rod Stitched Efficient Unitized Structure concept can meet these challenging demands of the next generation airframes. There are specific reasons why geometrically nonlinear analysis may be warranted for the hybrid wing body flat panel structure. In general, for sufficiently high internal pressure and/or mechanical loading, energy related to the in-plane strain may become significant relative to the bending strain energy, particularly in thin-walled areas such as the minimum gage skin extensively used in the structure under analysis. To account for this effect, a geometrically nonlinear strain-displacement relationship is needed to properly couple large out-of-plane and in-plane deformations. Depending on the loading, this nonlinear coupling mechanism manifests itself in a distinct manner in compression- and tension-dominated sections of the structure. Under significant compression, nonlinear analysis is needed to accurately predict loss of stability and postbuckled deformation. Under significant tension, the nonlinear effects account for suppression of the out-of-plane deformation due to in-plane stretching. By comparing the present results with the previously

  9. On the variability of sea drag in finite water depth

    Toffoli, A.; Loffredo, L.; Le Roy, P.; LefèVre, J.-M.; Babanin, A. V.

    2012-11-01

    The coupling between the atmospheric boundary layer and the ocean surface in large-scale models is usually parameterized in terms of the sea drag coefficient, which is routinely estimated as a function of mean wind speed. The scatter of data around such parametric dependencies, however, is very significant and imposes a serious limitation on the forecasts and predictions that make use of sea surface drag parameterizations. The analysis of an atmospheric and wave data set collected in finite water depth at the Lake George measurement site (Australia) suggests that this variability relates to a number of parameters at the air-sea interface other than wind speed alone. In particular, results indicate that the sea drag depends on water depth and wave steepness, which make the wave profile more vertically asymmetric, and the concentration of water vapor in the air, which modifies air density and friction velocity. These dependencies are used to derive parametric functions based on the combined contribution of wind, waves and relative humidity. A standard statistical analysis confirms a substantial improvement in the prediction of the drag coefficient and sea surface roughness when additional parameters are taken into account.

  10. Measurements of the Drag Coefficient of Simulated Micrometeoroids

    DeLuca, M.; Munsat, T.; Sternovsky, Z.

    2017-12-01

    The dust accelerator facility operated at the University of Colorado is used to simulate meteoric ablation, including measuring the ionization efficiency over a wide range of velocities (e.g., DeLuca et al., Planet. Space Sci., submitted, 2017). This presentation reports on the most recent experimental measurements of the drag coefficient that determines the particles' slowdown from their frictional interaction with the atmosphere. The measurements indicate that meteors experience considerably more slowdown than usually assumed. The simulated meteors consisted of submicron sized aluminum particles shot into an air chamber held at 200 mTorr pressure at velocities between 1 - 10 km/s using the dust accelerator and meteor ablation facility. The slowdown is calculated from precise timing measurements made using pickup tube detectors placed upstream and near the entrance to the air chamber, and an impact detector inside the air chamber at the downstream end of the chamber. Supporting modeling calculations show that the particles have little or no mass loss during their interaction with air and thus constant radius can be assumed. Preliminary results for the drag coefficient calculated from these timing measurements reveal that the aluminum particles have a drag coefficient of 1.51 ± 0.24 in air, which is higher than typically assumed in meteoric ablation models (usually 0.5 to 1), indicating that meteors may experience more air drag than previously assumed. More detailed measurements over a wider parameter range are underway.

  11. Investigation of drag effect using the field signature method

    Wan, Zhengjun; Liao, Junbi; Tian, Gui Yun; Cheng, Liang

    2011-01-01

    The potential drop (PD) method is an established non-destructive evaluation (NDE) technique. The monitoring of internal corrosion, erosion and cracks in piping systems, based on electrical field mapping or direct current potential drop array, is also known as the field signature method (FSM). The FSM has been applied in the field of submarine pipe monitoring and land-based oil and gas transmission pipes and containers. In the experimental studies, to detect and calculate the degree of pipe corrosion, the FSM analyses the relationships between the electrical resistance and pipe thickness using an electrode matrix. The relevant drag effect or trans-resistance will cause a large margin of error in the application of resistance arrays. It is the first time that the drag effect in the paper is investigated and analysed in resistance networks with the help of the FSM. Subsequently, a method to calculate the drag factors and eliminate its errors is proposed and presented. Theoretical analysis, simulation and experimental results show that the measurement accuracy can be improved by eliminating the errors caused by the drag effect

  12. Plasmon-mediated Coulomb drag between graphene waveguides

    Shylau, Artsem A.; Jauho, Antti-Pekka

    2014-01-01

    We analyze theoretically charge transport in Coulomb coupled graphene waveguides (GWGs). The GWGs are defined using antidot lattices, and the lateral geometry bypasses many technological challenges of earlier designs. The drag resistivity ρD, which is a measure of the many-particle interactions...

  13. Drag reduction of dense fine-grained slurries

    Vlasák, Pavel; Chára, Zdeněk; Štern, Petr

    2010-01-01

    Roč. 58, č. 4 (2010), s. 261-270 ISSN 0042-790X R&D Projects: GA ČR(CZ) GAP105/10/1574 Institutional research plan: CEZ:AV0Z20600510 Keywords : kaolin slurry * drag reduction * experimental investigation * peptization * slurry rheology Subject RIV: BK - Fluid Dynamics Impact factor: 0.553, year: 2010

  14. Aerodynamic drag reduction tests on a box-shaped vehicle

    Peterson, R. L.; Sandlin, D. R.

    1981-01-01

    The intent of the present experiment is to define a near optimum value of drag coefficient for a high volume type of vehicle through the use of a boattail, on a vehicle already having rounded front corners and an underbody seal, or fairing. The results of these tests will constitute a baseline for later follow-on studies to evaluate candidate methods of obtaining afterbody drag coefficients approaching the boattail values, but without resorting to such impractical afterbody extensions. The current modifications to the box-shaped vehicle consisted of a full and truncated boattail in conjunction with the faired and sealed underbody. Drag results from these configurations are compared with corresponding wind tunnel results of a 1/10 scale model. Test velocities ranged up to 96.6 km/h (60 mph) and the corresponding Reynolds numbers ranged up to 1.3 x 10 to the 7th power based on the vehicles length which includes the boattail. A simple coast-down technique was used to define drag.

  15. Experimental investigation of drag reduction by forward facing high ...

    Substantial aerodynamic drag, while flying at hypersonic Mach number, due to the presence of strong ... atmospheric flight of hypersonic vehicles, large-angle blunt-cone configurations are preferred at the cost of .... This paper is dedicated to Dr P R Viswanath for his contributions to experimental research in aerodynamics.

  16. Drag power kite with very high lift coefficient

    Bauer, F.; Kennel, R.M.; Hackl, C.M.; Campagnolo, F.; Patt, M.; Schmehl, R.

    2018-01-01

    As an alternative to conventional wind turbines, this study considered kites with onboard wind turbines driven by a high airspeed due to crosswind flight (“drag power”). The hypothesis of this study was, that if the kite's lift coefficient is maximized, then the power, energy yield, allowed costs

  17. Design and performance of the drag-disc turbine transducer

    Averill, R.H.; Goodrich, L.D.; Ford, R.E.

    1979-01-01

    Mass flow rates at the Loss-of-Fluid Test (LOFT) facility, EG and G Idaho, Inc., at the Idaho National Engineering Laboratory, are measured with the drag-disc turbine transducer (DTT). Operational description of the DTT and the developmental effort are discussed. Performance data and experiences with this transducer have been evaluated and are presented in this paper

  18. Investigation into the Mechanism of Polymer Thread Drag Reduction

    1990-01-01

    They conducted experiments in a 3.75 cm diameter pipe, Re = 85,000, where they injected drag reducing solutions of guar gum and polyacrylamide, P-295 a...manufactured by Dow Chemical. Concentrations of 5000 ppm and 466 ppm based on weight were used in the experiments. The dry powder was suspended in 300

  19. Separability of drag and thrust in undulatory animals and machines

    Bale, Rahul; Shirgaonkar, Anup A.; Neveln, Izaak D.; Bhalla, Amneet Pal Singh; Maciver, Malcolm A.; Patankar, Neelesh A.

    2014-12-01

    For nearly a century, researchers have tried to understand the swimming of aquatic animals in terms of a balance between the forward thrust from swimming movements and drag on the body. Prior approaches have failed to provide a separation of these two forces for undulatory swimmers such as lamprey and eels, where most parts of the body are simultaneously generating drag and thrust. We nonetheless show that this separation is possible, and delineate its fundamental basis in undulatory swimmers. Our approach unifies a vast diversity of undulatory aquatic animals (anguilliform, sub-carangiform, gymnotiform, bal-istiform, rajiform) and provides design principles for highly agile bioinspired underwater vehicles. This approach has practical utility within biology as well as engineering. It is a predictive tool for use in understanding the role of the mechanics of movement in the evolutionary emergence of morphological features relating to locomotion. For example, we demonstrate that the drag-thrust separation framework helps to predict the observed height of the ribbon fin of electric knifefish, a diverse group of neotropical fish which are an important model system in sensory neurobiology. We also show how drag-thrust separation leads to models that can predict the swimming velocity of an organism or a robotic vehicle.

  20. Deconstructing Hub Drag. Part 2. Computational Development and Anaysis

    2013-09-30

    leveraged a Vertical Lift Consortium ( VLC )-funded hub drag scaling research effort. To confirm this objective, correlations are performed with the...Technology™ Demonstrator aircraft using an unstructured computational solver. These simpler faired elliptical geome- tries can prove to be challenging ...possible. However, additional funding was obtained from the Vertical Lift Consortium ( VLC ) to perform this study. This analysis is documented in

  1. Clock transport synchronisation and the dragging of inertial frames

    Rosenblum, Arnold

    1987-01-01

    It is shown that it is possible, by using the lack of synchronisation of clocks by clock transport synchronisation in circular orbits, to test for the dragging of inertial frames in Einstein's theory of general relativity. Possible experiments are discussed. (author)

  2. Square tracking sensor for autonomous helicopter hover stabilization

    Oertel, Carl-Henrik

    1995-06-01

    Sensors for synthetic vision are needed to extend the mission profiles of helicopters. A special task for various applications is the autonomous position hold of a helicopter above a ground fixed or moving target. As a proof of concept for a general synthetic vision solution a restricted machine vision system, which is capable of locating and tracking a special target, was developed by the Institute of Flight Mechanics of Deutsche Forschungsanstalt fur Luft- und Raumfahrt e.V. (i.e., German Aerospace Research Establishment). This sensor, which is specialized to detect and track a square, was integrated in the fly-by-wire helicopter ATTHeS (i.e., Advanced Technology Testing Helicopter System). An existing model following controller for the forward flight condition was adapted for the hover and low speed requirements of the flight vehicle. The special target, a black square with a length of one meter, was mounted on top of a car. Flight tests demonstrated the automatic stabilization of the helicopter above the moving car by synthetic vision.

  3. Fatigue damage assessment of high-usage in-service aircraft fuselage structure

    Mosinyi, Bao Rasebolai

    As the commercial and military aircraft fleets continue to age, there is a growing concern that multiple-site damage (MSD) can compromise structural integrity. Multiple site damage is the simultaneous occurrence of many small cracks at independent structural locations, and is the natural result of fatigue, corrosion, fretting and other possible damage mechanisms. These MSD cracks may linkup and form a fatigue lead crack of critical length. The presence of MSD also reduces the structure's ability to withstand longer cracks. The objective of the current study is to assess, both experimentally and analytically, MSD formation and growth in the lap joint of curved panels removed from a retired aircraft. A Boeing 727-232 airplane owned and operated by Delta Air Lines, and retired at its design service goal, was selected for the study. Two panels removed from the left-hand side of the fuselage crown, near stringer 4L, were subjected to extended fatigue testing using the Full-Scale Aircraft Structural Test Evaluation and Research (FASTER) facility located at the Federal Aviation Administration (FAA) William J. Hughes Technical Center. The state of MSD was continuously assessed using several nondestructive inspection (NDI) methods. Damage to the load attachment points of the first panel resulted in termination of the fatigue test at 43,500 fatigue cycles, before cracks had developed in the lap joint. The fatigue test for the second panel was initially conducted under simulated in-service loading conditions for 120,000 cycles, and no cracks were detected in the skin of the panel test section. Artificial damage was then introduced into the panel at selected rivets in the critical (lower) rivet row, and the fatigue loads were increased. Visually detectable crack growth from the artificial notches was first seen after 133,000 cycles. The resulting lead crack grew along the lower rivet row, eventually forming an 11.8" long unstable crack after 141,771 cycles, at which point the

  4. Drag reduction of nata de coco suspensions in circular pipe flow

    Warashina, J.; Ogata, S.

    2015-04-01

    Reducing pipe friction by adding a drag-reducing agent has attracted interest as a means to reduce energy consumption. In addition to reducing drag, these agents are required to have a low environmental load and conserve natural resources. However, no drag-reducing agent currently satisfies both these conditions. We focused on nata de coco and found that the nata de coco fiber reduced drag by up to 25%. With respect to the mechanism of drag reduction by nata de coco fiber, the relationship between drag-reduction phenomena and the fiber form of nata de coco was investigated by visualization. We also found that the drag-reduction effect appeared to be due to the formation of networks of tangled fibers of nata de coco. However, drag reduction did not occur in the case in which fibers of nata de coco did not form networks.

  5. An Aerodynamic Database for the Mk 82 General Purpose Low Drag Bomb

    Krishnamoorthy, L

    1997-01-01

    The drag database of the Mk 82 General Purpose Low Drag bomb, the primary gravity weapon in the RAAF inventory, has some shortcomings in the quality and traceability of data, and in the variations due...

  6. Helicopter EMS: Research Endpoints and Potential Benefits

    Stephen H. Thomas

    2012-01-01

    Full Text Available Patients, EMS systems, and healthcare regions benefit from Helicopter EMS (HEMS utilization. This article discusses these benefits in terms of specific endpoints utilized in research projects. The endpoint of interest, be it primary, secondary, or surrogate, is important to understand in the deployment of HEMS resources or in planning further HEMS outcomes research. The most important outcomes are those which show potential benefits to the patients, such as functional survival, pain relief, and earlier ALS care. Case reports are also important “outcomes” publications. The benefits of HEMS in the rural setting is the ability to provide timely access to Level I or Level II trauma centers and in nontrauma, interfacility transport of cardiac, stroke, and even sepsis patients. Many HEMS crews have pharmacologic and procedural capabilities that bring a different level of care to a trauma scene or small referring hospital, especially in the rural setting. Regional healthcare and EMS system's benefit from HEMS by their capability to extend the advanced level of care throughout a region, provide a “backup” for areas with limited ALS coverage, minimize transport times, make available direct transport to specialized centers, and offer flexibility of transport in overloaded hospital systems.

  7. Dynamics of a split torque helicopter transmission

    Krantz, Timothy L.

    1994-06-01

    Split torque designs, proposed as alternatives to traditional planetary designs for helicopter main rotor transmissions, can save weight and be more reliable than traditional designs. This report presents the results of an analytical study of the system dynamics and performance of a split torque gearbox that uses a balance beam mechanism for load sharing. The Lagrange method was applied to develop a system of equations of motion. The mathematical model includes time-varying gear mesh stiffness, friction, and manufacturing errors. Cornell's method for calculating the stiffness of spur gear teeth was extended and applied to helical gears. The phenomenon of sidebands spaced at shaft frequencies about gear mesh fundamental frequencies was simulated by modeling total composite gear errors as sinusoid functions. Although the gearbox has symmetric geometry, the loads and motions of the two power paths differ. Friction must be considered to properly evaluate the balance beam mechanism. For the design studied, the balance beam is not an effective device for load sharing unless the coefficient of friction is less than 0.003. The complete system stiffness as represented by the stiffness matrix used in this analysis must be considered to precisely determine the optimal tooth indexing position.

  8. Quantifying drag on wellbore casings in moving salt sheets

    Weijermars, R.; Jackson, M. P. A.; Dooley, T. P.

    2014-08-01

    Frontier hydrocarbon development projects in the deepwater slopes of the Gulf of Mexico Basin, Santos Basin and Lower Congo Basin all require wells to cross ductile layers of autochthonous or allochthonous salt moving at peak rates of 100 mm yr-1. The Couette-Poiseuille number is introduced here to help pinpoint the depth of shear stress reversal in such salt layers. For any well-planned through salt, the probable range of creep forces of moving salt needs to be taken into account when designing safety margins and load-factor tolerance of the well casing. Drag forces increase with wellbore diameter, but more significantly with effective viscosity and speed of the creeping salt layer. The potential drag forces on cased wellbores in moving salt sheets are estimated analytically using a range of salt viscosities (1015-1019 Pa s) and creep rates (0-10 mm yr-1). Drag on perfectly rigid casing of infinite strength may reach up to 13 Giga Newton per meter wellbore length in salt having a viscosity of 1019 Pa s. Well designers may delay stress accumulations due to salt drag when flexible casing accommodates some of the early displacement and strain. However, all creeping salt could displace, fracture and disconnect well casing, eventually. The shear strength of typical heavy duty well casing (about 1000 MPa) can be reached due to drag by moving salt. Internal flow of salt will then fracture the casing near salt entry and exit points, but the structural damage is likely to remain unnoticed early in the well-life when the horizontal shift of the wellbore is still negligibly small (at less than 1 cm yr-1). Disruption of casing and production flow lines within the anticipated service lifetime of a well remains a significant risk factor within distinct zones of low-viscosity salt which may reach ultrafast creep rates of 100 mm yr-1.

  9. Reducing drag of a commuter train, using engine exhaust momentum

    Ha, Dong Keun

    The objective of this thesis was to perform numerical investigations of two different methods of injecting fluid momentum into the air flow above a commuter train to reduce its drag. Based on previous aerodynamic modifications of heavy duty trucks in improving fuel efficiency, two structural modifications were designed and applied to a Metrolink Services commuter train in the Los Angeles (LA) County area to reduce its drag and subsequently improve fuel efficiency. The first modification was an L-shaped channel, added to the exhaust cooling fan above the locomotive roof to divert and align the exhaust gases in the axial direction. The second modification was adding an airfoil shaped lid over the L-shape channel, to minimize the drag of the perturbed structure, and thus reduce the overall drag. The computational fluid dynamic (CFD) software CCM+ from CD-Adapco with the ?-? turbulence model was used for the simulations. A single train set which consists of three vehicles: one locomotive, one trailer car and one cab car were used. All the vehicles were modeled based on the standard Metrolink fleet train size. The wind speed was at 90 miles per hour (mph), which is the maximum speed for the Orange County Metrolink line. Air was used as the exhaust gas in the simulation. The temperature of the exhausting air emitting out of the cooling fan on the roof was 150 F and the average fan speed was 120 mph. Results showed that with the addition of the lid, momentum injection results in reduced flow separation and pressure recovery behind the locomotive, which reduces the overall drag by at least 30%.

  10. Mechanism of drag reduction for circular cylinders with patterned surface

    Butt, U.; Jehring, L.; Egbers, C.

    2014-01-01

    Highlights: • Reduced drag of patterned cylinders over a wide range of Re numbers. • Hexagonal patterns cannot be characterized as roughness structures. • Hexagonal bumps affect the flow like spherical dimples of smaller k/d ratio do. • Main separation is delayed caused by a partial separation. • Angle of a separation line is not constant over the length of cylinder. -- Abstract: In this paper, the flow over cylinders with a patterned surface (k/d = 1.98 × 10 −2 ) is investigated in a subsonic wind tunnel over Reynolds numbers ranging from 3.14 × 10 4 to 2.77 × 10 5 by measuring drag, flow visualization and measuring velocity profiles above the surface of the cylinders, to observe the effect of hexagonal patterns on the flow of air. These patterns can also be referred as hexagonal dimples or bumps depending on their configuration. The investigations revealed that a patterned cylinder with patterns pressed outwards has a drag coefficient of about 0.65 times of a smooth one. Flow visualization techniques including surface oil-film technique and velocity profile measurement were employed to elucidate this effect, and hence present the mechanism of drag reduction. The measurement of velocity profiles using hot-wire anemometry above the surface reveal that a hexagonal bump cause local separation generating large turbulence intensity along the separating shear layer. Due to this increased turbulence, the flow reattaches to the surface with higher momentum and become able to withstand the pressure gradient delaying the main separation significantly. Besides that, the separation does not appear to occur in a straight line along the length of the cylinder as in case of most passive drag control methods, but follow exactly the hexagonal patterns forming a wave with its crest at 115° and trough at 110°, in contrast to the laminar separation line at 85° for a smooth cylinder

  11. Wind Tunnel Test of a Risk-Reduction Wing/Fuselage Model to Examine Juncture-Flow Phenomena

    Kegerise, Michael A.; Neuhart, Dan H.

    2016-01-01

    A wing/fuselage wind-tunnel model was tested in the Langley 14- by 22-foot Subsonic Wind Tunnel in preparation for a highly-instrumented Juncture Flow Experiment to be conducted in the same facility. This test, which was sponsored by the NASA Transformational Tool and Technologies Project, is part of a comprehensive set of experimental and computational research activities to develop revolutionary, physics-based aeronautics analysis and design capability. The objectives of this particular test were to examine the surface and off-body flow on a generic wing/body combination to: 1) choose a final wing for a future, highly instrumented model, 2) use the results to facilitate unsteady pressure sensor placement on the model, 3) determine the area to be surveyed with an embedded laser-doppler velocimetry (LDV) system, 4) investigate the primary juncture corner- flow separation region using particle image velocimetry (PIV) to see if the particle seeding is adequately entrained and to examine the structure in the separated region, and 5) to determine the similarity of observed flow features with those predicted by computational fluid dynamics (CFD). This report documents the results of the above experiment that specifically address the first three goals. Multiple wing configurations were tested at a chord Reynolds number of 2.4 million. Flow patterns on the surface of the wings and in the region of the wing/fuselage juncture were examined using oil- flow visualization and infrared thermography. A limited number of unsteady pressure sensors on the fuselage around the wing leading and trailing edges were used to identify any dynamic effects of the horseshoe vortex on the flow field. The area of separated flow in the wing/fuselage juncture near the wing trailing edge was observed for all wing configurations at various angles of attack. All of the test objectives were met. The staff of the 14- by 22-foot Subsonic Wind Tunnel provided outstanding support and delivered

  12. Maneuver Acoustic Flight Test of the Bell 430 Helicopter

    Watts, Michael E.; Snider, Royce; Greenwood, Eric; Baden, Joel

    2012-01-01

    A cooperative flight test by NASA, Bell Helicopter and the U.S. Army to characterize the steady state acoustics and measure the maneuver noise of a Bell Helicopter 430 aircraft was accomplished. The test occurred during June/July, 2011 at Eglin Air Force Base, Florida. This test gathered a total of 410 data points over 10 test days and compiled an extensive data base of dynamic maneuver measurements. Three microphone configurations with up to 31 microphones in each configuration were used to acquire acoustic data. Aircraft data included DGPS, aircraft state and rotor state information. This paper provides an overview of the test.

  13. Helicopter Pilot Performance for Discrete-maneuver Flight Tasks

    Heffley, R. K.; Bourne, S. M.; Hindson, W. S.

    1984-01-01

    This paper describes a current study of several basic helicopter flight maneuvers. The data base consists of in-flight measurements from instrumented helicopters using experienced pilots. The analysis technique is simple enough to apply without automatic data processing, and the results can be used to build quantitative matah models of the flight task and some aspects of the pilot control strategy. In addition to describing the performance measurement technqiue, some results are presented which define the aggressiveness and amplitude of maneuvering for several lateral maneuvers including turns and sidesteps.

  14. CH-53K Heavy Lift Replacement Helicopter (CH-53K)

    2015-12-01

    Selected Acquisition Report (SAR) RCS: DD-A&T(Q&A)823-390 CH-53K Heavy Lift Replacement Helicopter (CH-53K) As of FY 2017 President’s Budget...December 2015 SAR March 4, 2016 10:04:18 UNCLASSIFIED 4 Col Henry Vanderborght PMA-261 Heavy Lift Helicopters Program Executive Office - Air, Anti...757-5780 Fax: 301-757-5109 DSN Phone: 757-5780 DSN Fax: 757-5109 Date Assigned: May 29, 2014 Program Information Program Name CH-53K Heavy Lift

  15. Robust Helicopter Stabilization in the Face of Wind Disturbance

    A. Danapalasingam, Kumeresan; Leth, John-Josef; la Cour-Harbo, Anders

    2010-01-01

    When a helicopter is required to hover with minimum deviations from a desired position without measurements of an affecting persistent wind disturbance, a robustly stabilizing control action is vital. In this paper, the stabilization of the position and translational velocity of a nonlinear...... controller is then designed based on nonlinear adaptive output regulations and robust stabilization of a chain of integrators by a saturated feedback. Simulation results show the effectiveness of the control design in the stabilization of helicopter motion and the built-in robustness of the controller...

  16. Tests with an integrated helmet system for the TIGER helicopter

    Boehm, Hans-Dieter V.; Evers, Carl; Stenner, K.-H.

    1998-08-01

    The TIGER helicopter is under development by the MODs of France and Germany for their armies. The initial German requirement was for anti-tank missions only. This task has been extended to support missions which resulted in an upgrade to the German 'UH-TIGER' variant. German MOD is planning to procure 212 UH-TIGER helicopters armed with TRIGAT-, HOT anti-tank missiles, STINGER air-to-air missiles, 68 mm rockets and a gun pod with a 12.7 mm gun.

  17. Conceptual Design and Performance Analysis for a Large Civil Compound Helicopter

    Russell, Carl; Johnson, Wayne

    2012-01-01

    A conceptual design study of a large civil compound helicopter is presented. The objective is to determine how a compound helicopter performs when compared to both a conventional helicopter and a tiltrotor using a design mission that is shorter than optimal for a tiltrotor and longer than optimal for a helicopter. The designs are generated and analyzed using conceptual design software and are further evaluated with a comprehensive rotorcraft analysis code. Multiple metrics are used to determine the suitability of each design for the given mission. Plots of various trade studies and parameter sweeps as well as comprehensive analysis results are presented. The results suggest that the compound helicopter examined for this study would not be competitive with a tiltrotor or conventional helicopter, but multiple possibilities are identified for improving the performance of the compound helicopter in future research.

  18. Flying control of small-type helicopter by detecting its in-air natural features

    Chinthaka Premachandra

    2015-05-01

    Full Text Available Control of a small type helicopter is an interesting research area in unmanned aerial vehicle development. This study aims to detect a more typical helicopter unequipped with markers as a means by which to resolve the various issues of the prior studies. Accordingly, we propose a method of detecting the helicopter location and pose through using an infrastructure camera to recognize its in-air natural features such as ellipse traced by the rotation of the helicopter's propellers. A single-rotor system helicopter was used as the controlled airframe in our experiments. Here, helicopter location is measured by detecting the main rotor ellipse center and pose is measured following relationship between the main rotor ellipse and the tail rotor ellipse. Following these detection results we confirmed the hovering control possibility of the helicopter through experiments.

  19. Moffies, artists, and queens: race and the production of South African gay male drag.

    Swarr, Amanda Lock

    2004-01-01

    This article draws on seventeen months of ethnographic fieldwork in South Africa to explore the experiences of urban and township drag performers. I show that two distinct sex-gender-sexuality systems have emerged based in the sociopolitical history of South Africa, and I argue that urban drag produces race oppositionally and examine how township femininity creates raced forms of gender, sex, and sexuality. Contemporary South African drag foregrounds the performativity and constitution of race and gender. My analysis attempts to challenge definitions of "drag" and "audience," suggesting the necessity for an integrated reconceptualization of drag studies.

  20. Experimental Investigation of the Fresnel Drag Effect in RF Coaxial Cables

    Brotherton D.

    2011-01-01

    Full Text Available An experiment that confirms the Fresnel drag formalism in RF coaxial cables is reported. The Fresnel "drag" in bulk dielectrics and in optical fibers has previously been well established. An explanation for this formalism is given, and it is shown that there is no actual drag phenomenon, rather that the Fresnel drag effect is merely the consequence of a simplified description of EM scattering within a dielectric in motion wrt the dynamical 3-space. The Fresnel drag effect plays a critical role in the design of various light-speed anisotropy detectors.

  1. Controlling turbulent drag across electrolytes using electric fields.

    Ostilla-Mónico, Rodolfo; Lee, Alpha A

    2017-07-01

    Reversible in operando control of friction is an unsolved challenge that is crucial to industrial tribology. Recent studies show that at low sliding velocities, this control can be achieved by applying an electric field across electrolyte lubricants. However, the phenomenology at high sliding velocities is yet unknown. In this paper, we investigate the hydrodynamic friction across electrolytes under shear beyond the transition to turbulence. We develop a novel, highly parallelised numerical method for solving the coupled Navier-Stokes Poisson-Nernst-Planck equation. Our results show that turbulent drag cannot be controlled across dilute electrolytes using static electric fields alone. The limitations of the Poisson-Nernst-Planck formalism hint at ways in which turbulent drag could be controlled using electric fields.

  2. Intershell resistance in multiwall carbon nanotubes: A Coulomb drag study

    Lunde, Anders Mathias; Flensborg, Karsten; Jauho, Antti-Pekka

    2005-01-01

    We calculate the intershell resistance R-21 in a multiwall carbon nanotube as a function of temperature T and Fermi level epsilon(F) (e.g., a gate voltage), varying the chirality of the inner and outer tubes. This is done in a so-called Coulomb drag setup, where a current I-1 in one shell induces...... a voltage drop V-2 in another shell by the screened Coulomb interaction between the shells neglecting the intershell tunneling. We provide benchmark results for R-21 = V2/I-1 within the Fermi liquid theory using Boltzmann equations. The band structure gives rise to strongly chirality-dependent suppression...... effects for the Coulomb drag between different tubes due to selection rules combined with mismatching of wave vector and crystal angular momentum conservation near the Fermi level. This gives rise to orders of magnitude changes in R-21 and even the sign of R-21 can change depending on the chirality...

  3. Wave drag reduction due to a self-aligning aerodisk

    Schnepf, Ch.; Wysocki, O.; Schülein, E.

    2015-06-01

    The effect of a self-aligning aerodisk on the wave drag of a blunt slender body in a pitching maneuver has been numerically investigated. The self-alignment was realized by a coupling of the flow solver and a flight mechanics tool. The slender body was pitched with high repetition rate between α = 0° and 20° at M = 1.41. Even at high α, the concept could align the aerodisk to the oncoming flow. In comparison to the reference body without a self-aligning aerodisk, a distinct drag reduction is achieved. A comparison with existing experimental data shows a qualitatively good agreement considering the shock and separation structure and the kinematics of the aerodisk.

  4. Bioinspired superhydrophobic, self-cleaning and low drag surfaces

    Bhushan, Bharat

    2013-09-01

    Nature has evolved objects with desired functionality using commonly found materials. Nature capitalizes on hierarchical structures to achieve functionality. The understanding of the functions provided by objects and processes found in nature can guide us to produce nanomaterials, nanodevices, and processes with desirable functionality. This article provides an overview of four topics: (1) Lotus Effect used to develop superhydrophobic and self-cleaning/antifouling surfaces with low adhesion, (2) Shark Skin Effect to develop surfaces with low fluid drag and anti-fouling characteristics, and (3-4) Rice Leaf and Butterfly Wing Effect to develop superhydrophobic and self-cleaning surfaces with low drag. Rice Leaf and Butterfly Wings combine the Shark Skin and Lotus Effects.

  5. Collisionless ion drag force on a spherical grain

    Hutchinson, I H

    2006-01-01

    The ion drag force on a spherical grain situated in a flowing collisionless plasma is obtained from the specialized coordinate electrostatic particle and thermals in cell simulation code (SCEPTIC) (Hutchinson 2002 Plasma Phys. Control. Fusion 44 1953, Hutchinson 2003 Plasma Phys. Control. Fusion 45 1477, Hutchinson 2005 Plasma Phys. Control. Fusion 47 71) and compared with recent analytic approximate treatments in the interesting and relevant case when the Debye length is only moderately larger than the sphere radius. There is a substantial complex structure in the results for transonic flows, which is explained in terms of the details of ion orbits. Naturally the prior analytic approximations miss this structure, and as a result they seriously underestimate the drag for speeds near the sound speed. An easy-to-evaluate expression for force is provided that fits the comprehensive results of the code. This expression, with minor modification, also fits the results even for Debye length much smaller than the sphere radius

  6. Drag reduction by dimples? - A complementary experimental/numerical investigation

    Lienhart, Hermann; Breuer, Michael; Koeksoy, Cagatay

    2008-01-01

    The paper is concerned with an experimental and numerical investigation of the turbulent flow over dimpled surfaces. Shallow dimples distributed regularly over the wall of a plane channel with large aspect ratio are used to study their effect on the friction drag. The resulting pressure drop in the channel was measured for smooth and dimpled walls. In addition to these investigations on internal flows, an external flow study was performed and boundary-layer profiles were measured using a Pitot-tube rake. Complementary to the measurements, direct numerical simulations for the internal flow configuration with and without dimples were carried out for two different grid resolutions and analyzed in detail. The objective was to clarify whether or not dimples cause reduction of the skin-friction drag

  7. Suboptimal control for drag reduction in turbulent pipe flow

    Choi, Jung Il; Sung, Hyung Jin; Xu, Chun Xiao

    2001-01-01

    A suboptimal control law in turbulent pipe flow is derived and tested. Two sensing variables ∂ρ/∂θ / w and ∂ν θ /∂r / w are applied with two actuations φ θ and φ γ . To test the suboptimal control law, direct numerical simulations of turbulent pipe flow at Re τ =150 are performed. When the control law is applied, a 13∼23% drag reduction is achieved. The most effective drag reduction is made at the pair of ∂υ θ /∂r / w and φ γ . An impenetrable virtual wall concept is useful for analyzing the near-wall suction and blowing. The virtual wall concept is useful for analyzing the near-wall behavior of the controlled flow. Comparison of the present suboptimal control with that of turbulent channel flow reveals that the curvature effect is insignificant

  8. Simultaneous drag and flow measurements of Olympic skeleton athletes

    Moon, Yae Eun; Digiulio, David; Peters, Steve; Wei, Timothy

    2009-11-01

    The Olympic sport of skeleton involves an athlete riding a small sled face first down a bobsled track at speeds up to 130 km/hr. In these races, the difference between gold and missing the medal stand altogether can be hundredths of a second per run. As such, reducing aerodynamic drag through proper body positioning is of first order importance. To better study the flow behavior and to improve the performance of the athletes, we constructed a static force balance system on a mock section of a bobsled track. Athlete and the sled are placed on the force balance system which is positioned at the exit of an open loop wind tunnel. Simultaneous drag force and DPIV velocity field measurements were made along with video recordings of body position to aid the athletes in determining their optimal aerodynamic body position.

  9. Physics and control of wall turbulence for drag reduction.

    Kim, John

    2011-04-13

    Turbulence physics responsible for high skin-friction drag in turbulent boundary layers is first reviewed. A self-sustaining process of near-wall turbulence structures is then discussed from the perspective of controlling this process for the purpose of skin-friction drag reduction. After recognizing that key parts of this self-sustaining process are linear, a linear systems approach to boundary-layer control is discussed. It is shown that singular-value decomposition analysis of the linear system allows us to examine different approaches to boundary-layer control without carrying out the expensive nonlinear simulations. Results from the linear analysis are consistent with those observed in full nonlinear simulations, thus demonstrating the validity of the linear analysis. Finally, fundamental performance limit expected of optimal control input is discussed.

  10. Effect of truncated cone roughness element density on hydrodynamic drag

    Womack, Kristofer; Schultz, Michael; Meneveau, Charles

    2017-11-01

    An experimental study was conducted on rough-wall, turbulent boundary layer flow with roughness elements whose idealized shape model barnacles that cause hydrodynamic drag in many applications. Varying planform densities of truncated cone roughness elements were investigated. Element densities studied ranged from 10% to 79%. Detailed turbulent boundary layer velocity statistics were recorded with a two-component LDV system on a three-axis traverse. Hydrodynamic roughness length (z0) and skin-friction coefficient (Cf) were determined and compared with the estimates from existing roughness element drag prediction models including Macdonald et al. (1998) and other recent models. The roughness elements used in this work model idealized barnacles, so implications of this data set for ship powering are considered. This research was supported by the Office of Naval Research and by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program.

  11. Reducing Aerodynamic Drag on Empty Open Cargo Vehicles

    Ross, James C.; Storms, Bruce L.; Dzoan, Dan

    2009-01-01

    Some simple structural modifications have been demonstrated to be effective in reducing aerodynamic drag on vehicles that have empty open cargo bays. The basic idea is to break up the airflow in a large open cargo bay by inserting panels to divide the bay into a series of smaller bays. In the case of a coal car, this involves inserting a small number (typically between two and four) of vertical full-depth or partial-depth panels.

  12. The effects of Poynting-Robertson drag on solar sails

    Abd El-Salam, F. A.

    2018-06-01

    In the present work, the concept of solar sailing and its developing spacecraft are presented. The effects of Poynting-Robertson drag on solar sails are considered. Some analytical control laws with some mentioned input constraints for optimizing solar sails dynamics in heliocentric orbit using Lagrange's planetary equations are obtained. Optimum force vector in a required direction is maximized by deriving optimal sail cone angle. New control laws that maximize thrust to obtain certain required maximization in some particular orbital element are obtained.

  13. Stokes’ and Lamb's viscous drag laws

    Eames, I; Klettner, C A

    2017-01-01

    Since Galileo used his pulse to measure the time period of a swinging chandelier in the 17th century, pendulums have fascinated scientists. It was not until Stokes' (1851 Camb. Phil. Soc. 9 8–106) (whose interest was spurred by the pendulur time pieces of the mid 19th century) treatise on viscous flow that a theoretical framework for the drag on a sphere at low Reynolds number was laid down. Stokes' famous drag law has been used to determine two fundamental physical constants—the charge on an electron and Avogadro's constant—and has been used in theories which have won three Nobel prizes. Considering its illustrious history it is then not surprising that the flow past a sphere and its two-dimensional analog, the flow past a cylinder, form the starting point of teaching flow past a rigid body in undergraduate level fluid mechanics courses. Usually starting with the two-dimensional potential flow past a cylinder, students progress to the three-dimensional potential flow past a sphere. However, when the viscous flow past rigid bodies is taught, the three-dimensional example of a sphere is first introduced, and followed by (but not often), the two-dimensional viscous flow past a cylinder. The reason why viscous flow past a cylinder is generally not taught is because it is usually explained from an asymptotic analysis perspective. In fact, this added mathematical complexity is why the drag on a cylinder was only solved in 1911, 60 years after the drag on a sphere. In this note, we show that the viscous flow past a cylinder can be explained without the need to introduce any asymptotic analysis while still capturing all the physical insight of this classic fluid mechanics problem. (paper)

  14. Biomimetics inspired surfaces for drag reduction and oleophobicity/philicity

    Bharat Bhushan

    2011-02-01

    Full Text Available The emerging field of biomimetics allows one to mimic biology or nature to develop nanomaterials, nanodevices, and processes which provide desirable properties. Hierarchical structures with dimensions of features ranging from the macroscale to the nanoscale are extremely common in nature and possess properties of interest. There are a large number of objects including bacteria, plants, land and aquatic animals, and seashells with properties of commercial interest. Certain plant leaves, such as lotus (Nelumbo nucifera leaves, are known to be superhydrophobic and self-cleaning due to the hierarchical surface roughness and presence of a wax layer. In addition to a self-cleaning effect, these surfaces with a high contact angle and low contact angle hysteresis also exhibit low adhesion and drag reduction for fluid flow. An aquatic animal, such as a shark, is another model from nature for the reduction of drag in fluid flow. The artificial surfaces inspired from the shark skin and lotus leaf have been created, and in this article the influence of structure on drag reduction efficiency is reviewed. Biomimetic-inspired oleophobic surfaces can be used to prevent contamination of the underwater parts of ships by biological and organic contaminants, including oil. The article also reviews the wetting behavior of oil droplets on various superoleophobic surfaces created in the lab.

  15. The influence of numerical models on determining the drag coefficient

    Dobeš Josef

    2014-03-01

    Full Text Available The paper deals with numerical modelling of body aerodynamic drag coefficient in the transition from laminar to turbulent flow regimes, where the selection of a suitable numerical model is problematic. On the basic problem of flow around a simple body – sphere selected computational models are tested. The values obtained by numerical simulations of drag coefficients of each model are compared with the graph of dependency of the drag coefficient vs. Reynolds number for a sphere. Next the dependency of Strouhal number vs. Reynolds number is evaluated, where the vortex shedding frequency values for given speed are obtained numerically and experimentally and then the values are compared for each numerical model and experiment. The aim is to specify trends for the selection of appropriate numerical model for flow around bodies problem in which the precise description of the flow field around the obstacle is used to define the acoustic noise source. Numerical modelling is performed by finite volume method using CFD code.

  16. Drag reduction: enticing turbulence, and then an industry.

    Spalart, Philippe R; McLean, J Douglas

    2011-04-13

    We examine drag-reduction proposals, as presented in this volume and in general, first with concrete examples of how to bridge the distance from pure science through engineering to what makes inventions go into service; namely, the value to the public. We point out that the true drag reduction can be markedly different from an estimate based simply on the difference between turbulent and laminar skin friction over the laminarized region, or between the respective skin frictions of the baseline and the riblet-treated flow. In some situations, this difference is favourable, and is due to secondary differences in pressure drag. We reiterate that the benefit of riblets, if it is expressed as a percentage in skin-friction reduction, is unfortunately lower at full-size Reynolds numbers than in a small-scale experiment or simulation. The Reynolds number-independent measure of such benefits is a shift of the logarithmic law, or 'ΔU(+)'. Anticipating the design of a flight test and then a product, we note the relative ease in representing riblets or laminarization in computational fluid dynamics, in contrast with the huge numerical and turbulence-modelling challenge of resolving active flow control systems in a calculation of the full flow field. We discuss in general terms the practical factors that have limited applications of concepts that would appear more than ready after all these years, particularly riblets and laminar-flow control.

  17. Drag reduction of a reverse-engineered vehicle

    Lecrivain, G.; Slaouti, A.; Kennedy, I. [Manchester Metropolitan Univ., Manchester (United Kingdom). Dept. of Engineering and Technology

    2007-08-09

    The aerodynamic performance of a hand-made sports car was numerically assessed using computational fluid dynamics (CFD) analysis of various shape modifications. The purpose was to achieve a lower drag design. Reverse-engineering was used to create a virtual model of complex 3D shapes for which no computer-aided drawings (CAD) data existed. From the predicted flow, the body could be redesigned for better performance prior to its remanufacturing. This paper described the multidisciplinary procedure involving reverse-engineering and CAD that was used to recreate a suitable watertight model of the sports car. The different errors embedded in the successive stages leading to the final model were accurately assessed and minimized. The whole vehicle was remodelled for drag reduction. Surface reconstruction was carried out, an an accurate set of high quality Non-Uniform Rational B-Spline (NURBS) surfaces was produced over the polygonal mesh resulting in a fine visual surface finish with smooth lines and contours, as required in the automotive industry. Further modifications were implemented for the purpose of drag reduction and to improve its aerodynamic performance. The application described in this paper can be extended to any other similarly intricate vehicle or industrial component. 12 refs., 1 tab., 11 figs.

  18. Aerodynamic drag control by pulsed jets on simplified car geometry

    Gilliéron, Patrick; Kourta, Azeddine

    2013-02-01

    Aerodynamic drag control by pulsed jets is tested in a wind tunnel around a simplified car geometry named Ahmed body with a rear slant angle of 35°. Pulsed jet actuators are located 5 × 10-3 m from the top of the rear window. These actuators are produced by a pressure difference ranging from 1.5 to 6.5 × 105 Pa. Their excitation frequency can vary between 10 and 550 Hz. The analysis of the control effects is based on wall visualizations, aerodynamic drag coefficient measurements, and the velocity fields obtained by 2D PIV measurements. The maximum drag reduction is 20 % and is obtained for the excitation frequency F j = 500 Hz and for the pressure difference ∆ P = 1.5 × 105 Pa. This result is linked with a substantial reduction in the transverse development of the longitudinal vortex structures coming from the left and right lateral sides of the rear window, with a displacement of the vortex centers downstream and with a decrease in the transverse rotational absolute values of these structures.

  19. The elaborate plumage in peacocks is not such a drag.

    Askew, Graham N

    2014-09-15

    One of the classic examples of an exaggerated sexually selected trait is the elaborate plumage that forms the train in male peafowl Pavo cristatus (peacock). Such ornaments are thought to reduce locomotor performance as a result of their weight and aerodynamic drag, but this cost is unknown. Here, the effect that the train has on take-off flight in peacocks was quantified as the sum of the rates of change of the potential and kinetic energies of the body (P(CoM)) in birds with trains and following the train's removal. There was no significant difference between P(CoM) in birds with and without a train. The train incurs drag during take-off; however, while this produces a twofold increase in parasite drag, parasite power only accounts for 0.1% of the total aerodynamic power. The train represented 6.9% of body weight and is expected to increase induced power. The absence of a detectable effect on take-off performance does not necessarily mean that there is no cost associated with possessing such ornate plumage; rather, it suggests that given the variation in take-off performance per se, the magnitude of any effect of the train has little meaningful functional relevance. © 2014. Published by The Company of Biologists Ltd.

  20. 5th Drag Reduction in Engineering Flows Meeting

    1991-01-01

    The European Drag Reduction Meeting has been held on 15th and 16th November 1990 in London. This was the fifth of the annual European meetings on drag reduction in engineering flows. The main objective of this meeting was to discuss up-to-date results of drag reduction research carried out in Europe. The organiser has adopted the philosophy of discussing the yesterday's results rather than the last year's results. No written material has therefore been requested for the meeting. It was only after the meeting the submission of papers was requested to the participants, from which 16 papers were selected for this proceedings volume. The meeting has attracted a record number of participants with a total of 52 researchers from seven European countries, U. K. , France, Germany, the Netherlands, Italy, Switzerland and U. S. S. R. as well as from Japan, Canada and Australia. The subjects covered in this proceedings volume include riblets, LEBUs (Large Eddy Break-Up device), surface roughness, compliant surfaces and p...

  1. Coordination of multiple appendages in drag-based swimming.

    Alben, Silas; Spears, Kevin; Garth, Stephen; Murphy, David; Yen, Jeannette

    2010-11-06

    Krill are aquatic crustaceans that engage in long distance migrations, either vertically in the water column or horizontally for 10 km (over 200,000 body lengths) per day. Hence efficient locomotory performance is crucial for their survival. We study the swimming kinematics of krill using a combination of experiment and analysis. We quantify the propulsor kinematics for tethered and freely swimming krill in experiments, and find kinematics that are very nearly metachronal. We then formulate a drag coefficient model which compares metachronal, synchronous and intermediate motions for a freely swimming body with two legs. With fixed leg velocity amplitude, metachronal kinematics give the highest average body speed for both linear and quadratic drag laws. The same result holds for five legs with the quadratic drag law. When metachronal kinematics is perturbed towards synchronous kinematics, an analysis shows that the velocity increase on the power stroke is outweighed by the velocity decrease on the recovery stroke. With fixed time-averaged work done by the legs, metachronal kinematics again gives the highest average body speed, although the advantage over synchronous kinematics is reduced.

  2. Airfoil Drag Reduction using Controlled Trapped Vorticity Concentrations

    Desalvo, Michael; Glezer, Ari

    2017-11-01

    The aerodynamic performance of a lifting surface at low angles of attack (when the base flow is fully attached) is improved through fluidic modification of its ``apparent'' shape by superposition of near-surface trapped vorticity concentrations. In the present wind tunnel investigations, a controlled trapped vorticity concentration is formed on the pressure surface of an airfoil (NACA 4415) using a hybrid actuator comprising a passive obstruction of scale O(0.01c) and an integral synthetic jet actuator. The jet actuation frequency [Stact O(10)] is selected to be at least an order of magnitude higher than the characteristic unstable frequency of the airfoil wake, thereby decoupling the actuation from the global instabilities of the base flow. Regulation of vorticity accumulation in the vicinity of the actuator by the jet effects changes in the local pressure, leading in turn to changes in the airfoil's drag and lift. Trapped vorticity can lead to a significant reduction in drag and reduced lift (owing to the sense of the vorticity), e.g. at α =4° and Re = 6.7 .105 the drag and lift reductions are 14% and 2%, respectively. PIV measurements show the spatial variation in the distribution of vorticity concentrations and yield estimates of the corresponding changes in circulation.

  3. Role of Elasto-Inertial Turbulence in Polymer Drag Reduction

    Dubief, Yves; Sid, Samir; Terrapon, Vincent

    2017-11-01

    Elasto-Inertial Turbulence (EIT) is a peculiar state of turbulence found in dilute polymer solutions flowing in parallel wall flows over a wide range of Reynolds numbers. At subcritical Reynolds numbers, appropriate boundary conditions trigger EIT, a self-sustaining cycle of energy transfers between thin sheets of stretched polymers and velocity perturbations, which translates into an increase of friction drag. For critical and supercritical Reynolds numbers, polymer additives may lead to significant drag reduction, bounded by the asymptotic state known as Maximum Drag Reduction (MDR). The present research investigates the role of EIT in the dynamics of critical and supercritical Reynolds number wall flows. Using high-fidelity direct numerical simulations of channel flows and the FENE-P model, we establish that (i) EIT is two-dimensional, (ii) the scales essential to the existence of EIT are sub-Kolmogorov, and (iii) EIT drives MDR at low and possibly moderate Reynolds number turbulent flows. These findings were validated in two different codes and using unprecedented resolutions for polymer flows. YD is grateful for the support of Binational Science Foundation. SS and VT acknowledges Fonds de la Recherche Scientifique (FNRS), MarieCurie Career Integration Grant and computing allocation from University of Liege and PRACE.

  4. Perturbed Partial Cavity Drag Reduction at High Reynolds Numbers

    Makiharju, Simo; Elbing, Brian; Wiggins, Andrew; Dowling, David; Perlin, Marc; Ceccio, Steven

    2010-11-01

    Ventilated partial cavities were investigated at Reynolds numbers to 80 million. These cavities could be suitable for friction drag reduction on ocean going vessels and thereby lead to environmental and economical benefits. The test model was a 3.05 m wide by 12.9 m long flat plate, with a 0.18 m backward-facing step and a cavity-terminating beach, which had an adjustable slope, tilt and height. The step and beach trapped a ventilated partial cavity over the longitudinal mid-section of the model. Large-scale flow perturbations, mimicking the effect of ambient ocean waves were investigated. For the conditions tested a cavity could be maintained under perturbed flow conditions when the gas flux supplied was greater than the minimum required to maintain a cavity under steady conditions, with larger perturbations requiring more excess gas flux to maintain the cavity. High-speed video was used to observe the unsteady three dimensional cavity closure, the overall cavity shape, and the cavity oscillations. Cavities with friction drag reduction exceeding 95% were attained at optimal conditions. A simplified energy cost-benefit analysis of partial cavity drag reduction was also performed. The results suggest that PCDR could potentially lead to energy savings.

  5. Optimal Aerodynamic Design of Conventional and Coaxial Helicopter Rotors in Hover and Forward Flight

    Giovanetti, Eli B.

    This dissertation investigates the optimal aerodynamic performance and design of conventional and coaxial helicopters in hover and forward flight using conventional and higher harmonic blade pitch control. First, we describe a method for determining the blade geometry, azimuthal blade pitch inputs, optimal shaft angle (rotor angle of attack), and division of propulsive and lifting forces among the components that minimize the total power for a given forward flight condition. The optimal design problem is cast as a variational statement that is discretized using a vortex lattice wake to model inviscid forces, combined with two-dimensional drag polars to model profile losses. The resulting nonlinear constrained optimization problem is solved via Newton iteration. We investigate the optimal design of a compound vehicle in forward flight comprised of a coaxial rotor system, a propeller, and optionally, a fixed wing. We show that higher harmonic control substantially reduces required power, and that both rotor and propeller efficiencies play an important role in determining the optimal shaft angle, which in turn affects the optimal design of each component. Second, we present a variational approach for determining the optimal (minimum power) torque-balanced coaxial hovering rotor using Blade Element Momentum Theory including swirl. We show that the optimal hovering coaxial rotor generates only a small percentage of its total thrust on the portion of the lower rotor operating in the upper rotor's contracted wake, resulting in an optimal design with very different upper and lower rotor twist and chord distributions. We also show that the swirl component of induced velocity has a relatively small effect on rotor performance at the disk loadings typical of helicopter rotors. Third, we describe a more refined model of the wake of a hovering conventional or coaxial rotor. We approximate the rotor or coaxial rotors as actuator disks (though not necessarily uniformly loaded

  6. Helicopter Gas Turbine Engine Performance Analysis : A Multivariable Approach

    Arush, Ilan; Pavel, M.D.

    2017-01-01

    Helicopter performance relies heavily on the available output power of the engine(s) installed. A simplistic single-variable analysis approach is often used within the flight-testing community to reduce raw flight-test data in order to predict the available output power under different atmospheric

  7. Extending helicopter operations to meet future integrated transportation needs.

    Stanton, Neville A; Plant, Katherine L; Roberts, Aaron P; Harvey, Catherine; Thomas, T Glyn

    2016-03-01

    Helicopters have the potential to be an integral part of the future transport system. They offer a means of rapid transit in an overly populated transport environment. However, one of the biggest limitations on rotary wing flight is their inability to fly in degraded visual conditions in the critical phases of approach and landing. This paper presents a study that developed and evaluated a Head up Display (HUD) to assist rotary wing pilots by extending landing to degraded visual conditions. The HUD was developed with the assistance of the Cognitive Work Analysis method as an approach for analysing the cognitive work of landing the helicopter. The HUD was tested in a fixed based flight simulator with qualified helicopter pilots. A qualitative analysis to assess situation awareness and workload found that the HUD enabled safe landing in degraded conditions whilst simultaneously enhancing situation awareness and reducing workload. Continued development in this area has the potential to extend the operational capability of helicopters in the future. Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.

  8. Neck Pain in Military Helicopter Pilots: Prevalence and Associated Factors

    van den Oord, Marieke H. A. H.; de Loose, Veerle; Meeuwsen, Ted; Sluiter, Judith K.; Frings-Dresen, Monique H. W.

    2010-01-01

    Our aim is to estimate the self-reported one-year prevalence of neck pain in military helicopter pilots and to compare work-related, individual, and health-related factors in the pilots with (neck pain group) and without (reference group) regular or continuous neck pain. A questionnaire was

  9. At Issue: Helicopter Parents and Millennial Students, an Annotated Bibliography

    Pricer, Wayne F.

    2008-01-01

    Technological advances have made it easy for parents and children--many of them students--to communicate instantaneously. Devices and technologies such as cell phones, laptops, texting, and e-mail all enable various forms of instant communication. "Helicopter parents" are regarded as very overprotective and overly involved in the affairs of their…

  10. Leadership Styles in United States Marine Corps Transport Helicopter Squadrons

    1989-12-01

    This thesis examined leadership styles in United States Marine Corps transport helicopter squadrons. Analyses were conducted to determine how... leadership styles related to subordinate extra effort, leader effectiveness, satisfaction with leader, unit cohesion, and unit morale. The importance of...military history to the development of military leaders was also examined. Leadership styles of officers were evaluated by the leader himself as well as

  11. 78 FR 63429 - Airworthiness Directives; Eurocopter France Helicopters

    2013-10-24

    ... Jersey Avenue SE., Washington, DC 20590-0001. Hand Delivery: Deliver to the ``Mail'' address between 9 a... rotor control turnbuckle ruptured because of corrosion. The damage was discovered during a flight... corrosion or a crack. The delivery date is the date the helicopter left Eurocopter's manufacturing plant in...

  12. 78 FR 23686 - Airworthiness Directives; Eurocopter France Helicopters

    2013-04-22

    ...-140, 1200 New Jersey Avenue SE., Washington, DC 20590-0001. Hand Delivery: Deliver to the ``Mail... during a scheduled maintenance check, a helicopter was discovered to have interference between the...) Inspect the right and left attachment points of the TGB forward attachment to measure the dimension for a...

  13. Enhancing Public Helicopter Safety as a Component of Homeland Security

    2016-12-01

    Risk Assessment Tool GPS Global Positioning System IFR instrument flight rules ILS instrument landing system IMC instrument meteorological...daily operations. Additionally, the effectiveness of the standards is evaluated by determining if these standards would have prevented the accidents...trends, such as human behavior and lack of standards, that are common in public safety helicopter accidents. Public safety aviation agencies can use this

  14. Organizing a Ground Crew for Today's Helicopter Parents

    Coburn, Karen Levin

    2006-01-01

    The relationship between college students and their parents is far closer than it was when most of today's educators were in school. Tapping into the upside and managing the potential drawbacks of highly involved parents is taking on great importance on an increasing number of campuses. Whether people call them "helicopter parents" or…

  15. 77 FR 70360 - Airworthiness Directives; Eurocopter France Helicopters

    2012-11-26

    ... helicopters. This AD requires inspecting the cage of the free-wheel assembly for the correct alignment of the... tail rotor drive shaft free-wheel cage, which caused a pilot to experience a heavy jerk in the yaw.... That NPRM proposed to require inspecting the cage of the free-wheel assembly for the correct alignment...

  16. 78 FR 76984 - Airworthiness Directives; Eurocopter France Helicopters

    2013-12-20

    ... inspecting each jettisonable emergency exit window panel (window) for sealant, and removing any sealant that... prevent failure of the windows to jettison, so helicopter occupants can exit the aircraft during an... Office, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE., Washington, DC 20590...

  17. 78 FR 37156 - Airworthiness Directives; Eurocopter France Helicopters

    2013-06-20

    ... inspecting each jettisonable emergency exit window panel (window) for sealant, and removing any sealant that... prevent failure of the windows to jettison, so helicopter occupants can exit the aircraft during an... comments to the U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor...

  18. Helicopter Rotor Noise Prediction: Background, Current Status, and Future Direction

    Brentner, Kenneth S.

    1997-01-01

    Helicopter noise prediction is increasingly important. The purpose of this viewgraph presentation is to: 1) Put into perspective the recent progress; 2) Outline current prediction capabilities; 3) Forecast direction of future prediction research; 4) Identify rotorcraft noise prediction needs. The presentation includes an historical perspective, a description of governing equations, and the current status of source noise prediction.

  19. Helicopter pilots' views of air traffic controller responsibilities: a mismatch.

    Martin, Daniel; Nixon, Jim

    2018-02-21

    Controllers and pilots must work together to ensure safe and efficient helicopter flight within the London control zone. Subjective ratings of pilot perception of controller responsibility for five key flight tasks were obtained from thirty helicopter pilots. Three types of airspace were investigated. Results indicate that there is variation in pilot understanding of controller responsibility compared to the formal regulations that define controller responsibility. Significant differences in the perception of controller responsibility were found for the task of aircraft separation in class D airspace and along helicopter routes. Analysis of the patterns of response suggests that task type rather than the airspace type may be the key factor. Results are framed using the concept of a shared mental model. This research demonstrates that pilots flying in complex London airspace have an expectation of controller responsibility for certain flight tasks, in certain airspace types that is not supported by aviation regulation. Practitioner Summary: The responsibility for tasks during flight varies according to the flight rules used and airspace type. Helicopter pilots may attribute responsibility to controllers for tasks when controllers have no responsibility as defined by regulation. This variation between pilot perceptions of controller responsibility could affect safety within the London control zone.

  20. 78 FR 20234 - Airworthiness Directives; Eurocopter France Helicopters

    2013-04-04

    ... prompted by flight crew reports of deviations between the displayed attitude on the attitude display screen... screens occurred simultaneously during flight on several helicopters equipped with the GV76-1 vertical... of the Rotorcraft Flight Manual (RFM) by inserting a copy of this AD into the RFM or by pen and ink...

  1. 77 FR 58971 - Airworthiness Directives; Eurocopter France (Eurocopter) Helicopters

    2012-09-25

    ... prompted by flight crew reports of deviations between the displayed attitude on the attitude display screen... screens occurred simultaneously during flight on several helicopters equipped with the GV76-1 vertical... of the Rotorcraft Flight Manual (RFM) by inserting a copy of this AD into the RFM or by pen and ink...

  2. Military Potential Test of the UH-2A Helicopter.

    1963-10-25

    required to fully service two engines during engine change. 3. One quart of hydr aulic fluid , MIL 5606. Used to replace spillage while disconnecting...Maryland , dated 24 January 1963. 7. Report Nr. 1, Final Report, Climatic Laboratory Environ- mental Test of the Model UH- 2A Helicopter , by US

  3. Development in helicopter tail boom strake applications in the US

    Wilson, John C.; Kelley, Henry L.; Donahue, Cynthia C.; Yenni, Kenneth R.

    1988-01-01

    The use of a strake or spoiler on a helicopter tail boom to beneficially change helicopter tail boom air loads was suggested in the United States in 1975. The anticipated benefits were a change of tail boom loads to reduce required tail rotor thrust and power and improve directional control. High tail boom air loads experienced by the YAH-64 and described in 1978 led to a wind tunnel investigation of the usefullness of strakes in altering such loads on the AH-64, UH-60, and UH-1 helicopters. The wind tunnel tests of 2-D cross sections of the tail boom of each demonstrated that a strake or strakes would be effective. Several limited test programs with the U.S. Army's OH-58A, AH-64, and UH-60A were conducted which showed the effects of strakes were modest for those helicopters. The most recent flight test program, with a Bell 204B, disclosed that for the 204B the tail boom strake or strakes would provide more than a modest improvement in directional control and reduction in tail rotor power.

  4. 77 FR 30230 - Airworthiness Directives; Eurocopter Deutschland Helicopters

    2012-05-22

    ... September 30, 2011. (g) Subject Joint Aircraft Service Component (JASC) Code: 2436: DC Generator Control... Deutschland GmbH Model MBB-BK117 C-2 helicopters with certain Generator Control Units (GCU) installed. This..., West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE., Washington, DC 20590-0001. Hand...

  5. 77 FR 69556 - Airworthiness Directives; Eurocopter Deutschland Helicopters

    2012-11-20

    ..., 2011. (h) Subject Joint Aircraft Service Component (JASC) Code: 2436: DC Generator Control Unit. Issued... Deutschland GmbH (ECD) Model MBB-BK117 C-2 helicopters with certain Generator Control Units (GCU) installed... Ground Floor, Room W12- 140, 1200 New Jersey Avenue SE., Washington, DC 20590. FOR FURTHER INFORMATION...

  6. Helicopter Approach Capability Using the Differential Global Positioning System

    Kaufmann, David N.

    1994-01-01

    The results of flight tests to determine the feasibility of using the Global Positioning System (GPS) in the Differential mode (DGPS) to provide high accuracy, precision navigation and guidance for helicopter approaches to landing are presented. The airborne DGPS receiver and associated equipment is installed in a NASA UH-60 Black Hawk helicopter. The ground-based DGPS reference receiver is located at a surveyed test site and is equipped with a real-time VHF data link to transmit correction information to the airborne DGPS receiver. The corrected airborne DGPS information, together with the preset approach geometry, is used to calculate guidance commands which are sent to the aircraft's approach guidance instruments. The use of DGPS derived guidance for helicopter approaches to landing is evaluated by comparing the DGPS data with the laser tracker truth data. The errors indicate that the helicopter position based on DGPS guidance satisfies the International Civil Aviation Organization (ICAO) Category 1 (CAT 1) lateral and vertical navigational accuracy requirements.

  7. Routing helicopters for crew exchanges on off-shore locations

    Sierksma, G.; Tijssen, G.A.

    This paper deals with a vehicle routing problem with split demands, namely the problem of determining a flight schedule for helicopters to off-shore platform locations for exchanging crew people employed on these platforms. The problem is formulated as an LP model and solved by means of a

  8. Characteristics, Causes, and Evaluation of Helicopter Particulate Visual Obstruction

    2012-09-10

    future full-scale testing. The thrust sources examined were a 1 in. diameter nozzle , a 4 in. diameter nozzle , and a 16 in. ducted fan. The sources...Hiller also evaluated inclining the thrust vector , and determined there was little reduction in dynamic pressure at the point of ground interaction...CHARACTERISTICS, CAUSES, AND EVALUATION OF HELICOPTER PARTICULATE VISUAL OBSTRUCTION THESIS

  9. 77 FR 5418 - Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

    2012-02-03

    ...) Subject Joint Aircraft Service Component (JASC) Code: 2800, Fuel system. Issued in Fort Worth, Texas, on... aft fuel system 40 micron fuel filter element with a 10 micron fuel filter element. This proposed AD... AD for the Sikorsky Model S-61A, D, E, L, N, NM, R, and V helicopters with a fuel system 40 micron...

  10. 78 FR 17591 - Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

    2013-03-22

    ... aft fuel system 40 micron fuel filter element with a 10 micron nominal (40 micron absolute) fuel... helicopters with a fuel system 40 micron fuel filter element, part number (P/N) 52-0505-2 or 52-01064-1. That NPRM proposed to require replacing each forward and aft fuel system 40 micron fuel filter element with...

  11. Flight Test Guide (Part 61 Revised): Instrument Pilot: Helicopter.

    Federal Aviation Administration (DOT), Washington, DC. Flight Standards Service.

    The guide provides an outline of the skills required to pass the flight test for an Instrument Pilot Helicopter Rating under Part 61 (revised) of Federal Aviation Regulations. General procedures for flight tests are described and the following pilot operations outlined: maneuvering by reference to instruments, IFR navigation, instrument…

  12. 78 FR 58256 - Airworthiness Directives; Eurocopter France Helicopters

    2013-09-23

    ... revising the RFM to reduce the Velocity Never Exceed (V NE ) indicated airspeed (IAS) limitation. It also... (IAS). EAD 2012-0217-E retains some of the requirements of EAD 2012-0207-E, removes the airspeed... Model AS550C3 helicopters (EASB 01.00.65). EASB 01.00.65 is Revision 3, dated February 4, 2013. EASB 01...

  13. Using Paper Helicopters to Teach Statistical Process Control

    Johnson, Danny J.

    2011-01-01

    This hands-on project uses a paper helicopter to teach students how to distinguish between common and special causes of variability when developing and using statistical process control charts. It allows the student to experience a process that is out-of-control due to imprecise or incomplete product design specifications and to discover how the…

  14. Helicopter blades running elevation measurement using omnidirectional vision

    Chengtao CAI

    2017-12-01

    Full Text Available Omnidirectional dynamic space parameters of high-speed rotating helicopter blades are precise 3D vector description of the blades. In particular, the elevation difference is directly related to the aerodynamic performance and maneuverability of the helicopter. The state of the art detection techniques based on optics and common vision have several drawbacks, such as high demands on devices but poor extensibility, limited measurement range and fixed measurement position. In this paper, a novel approach of helicopter blades running elevation measurement is proposed based on omnidirectional vision. With the advantages of panoramic visual imaging integration, 360° field of view and rotation in-variance, high-resolution images of all rotating blades positions are obtained at one time. By studying the non-linear calibration and calculation model of omnidirectional vision system, aiming at solving the problem of inaccurate visual space mapping model, the omnidirectional and full-scale measurement of the elevation difference are finalized. Experiments are carried out on our multifunctional simulation blades test system and the practical blades test tower, respectively. The experimental results demonstrate the effectiveness of the proposed method and show that the proposed method can considerably reduce the complexity of measurement. Keywords: Full-scale measurement, Helicopter blades elevation, Non-linear calibration, Omnidirectional vision, Unified sphere model

  15. 78 FR 38826 - Airworthiness Directives; Various Helicopter Models

    2013-06-28

    ... (ECD) Model MBB-BK 117 C-2 helicopter picked up a dummy load of 552 lbs. to conduct a ``maximum load... comply with this AD. It will take about 1 work-hour to perform the lift testing at an average labor rate... the distribution of power and responsibilities among the various levels of government. For the reasons...

  16. Transformation of Helicopter PinS Procedures for Airplanes

    Jakub Kraus

    2013-09-01

    Full Text Available This article deals with the possibility to use existing helicopter Point in Space procedures with minor changes for airplanes. The basis is to find parts of PinS procedures that need to be changed, suggest these changes, and then determine whether the revised procedures could be usable and could bring the benefits for airplane operations.

  17. The need for a dedicated public service helicopter design

    Morrison, R.

    1984-01-01

    The need to provide the necessary funding to research, design and contract the building of an advanced technology rotorcraft that will meet the mission demands of public service (fire, police, paramedics and rescue) operators is discussed. Noise and cost factors, the greatest objections on the part of many police and public adminstrators are addressed. The growth of helicopter utilization in public service is documented.

  18. 77 FR 68058 - Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

    2012-11-15

    ... Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters AGENCY: Federal Aviation Administration (FAA... airworthiness directive (AD) for Sikorsky Aircraft Corporation (Sikorsky) Model S-70, S-70A, S-70C, S-70C(M... after receipt. For service information identified in this AD, contact Sikorsky Aircraft Corporation...

  19. Effects of helicopter transport on red blood cell components

    Otani, Taiichi; Oki, Ken-ichi; Akino, Mitsuaki; Tamura, Satoru; Naito, Yuki; Homma, Chihiro; Ikeda, Hisami; Sumita, Shinzou

    2012-01-01

    Background There are no reported studies on whether a helicopter flight affects the quality and shelf-life of red blood cells stored in mannitol-adenine-phosphate. Materials and methods Seven days after donation, five aliquots of red blood cells from five donors were packed into an SS-BOX-110 container which can maintain the temperature inside the container between 2 °C and 6 °C with two frozen coolants. The temperature of an included dummy blood bag was monitored. After the box had been transported in a helicopter for 4 hours, the red blood cells were stored again and their quality evaluated at day 7 (just after the flight), 14, 21 and 42 after donation. Red blood cell quality was evaluated by measuring adenosine triphosphate, 2,3-diphosphoglycerate, and supernatant potassium, as well as haematocrit, intracellular pH, glucose, supernatant haemoglobin, and haemolysis rate at the various time points. Results During the experiment the recorded temperature remained between 2 and 6 °C. All data from the red blood cells that had undergone helicopter transportation were the same as those from a control group of red blood cell samples 7 (just after the flight), 14, 21, and 42 days after the donation. Only supernatant Hb and haemolysis rate 42 days after the donation were slightly increased in the helicopter-transported group of red blood cell samples. All other parameters at 42 days after donation were the same in the two groups of red blood cells. Discussion These results suggest that red blood cells stored in mannitol-adenine-phosphate are not significantly affected by helicopter transportation. The differences in haemolysis by the end of storage were small and probably not of clinical significance. PMID:22153688

  20. Effects of helicopter transport on red blood cell components.

    Otani, Taiichi; Oki, Ken-ichi; Akino, Mitsuaki; Tamura, Satoru; Naito, Yuki; Homma, Chihiro; Ikeda, Hisami; Sumita, Shinzou

    2012-01-01

    There are no reported studies on whether a helicopter flight affects the quality and shelf-life of red blood cells stored in mannitol-adenine-phosphate. Seven days after donation, five aliquots of red blood cells from five donors were packed into an SS-BOX-110 container which can maintain the temperature inside the container between 2 °C and 6 °C with two frozen coolants. The temperature of an included dummy blood bag was monitored. After the box had been transported in a helicopter for 4 hours, the red blood cells were stored again and their quality evaluated at day 7 (just after the flight), 14, 21 and 42 after donation. Red blood cell quality was evaluated by measuring adenosine triphosphate, 2,3-diphosphoglycerate, and supernatant potassium, as well as haematocrit, intracellular pH, glucose, supernatant haemoglobin, and haemolysis rate at the various time points. During the experiment the recorded temperature remained between 2 and 6 °C. All data from the red blood cells that had undergone helicopter transportation were the same as those from a control group of red blood cell samples 7 (just after the flight), 14, 21, and 42 days after the donation. Only supernatant Hb and haemolysis rate 42 days after the donation were slightly increased in the helicopter-transported group of red blood cell samples. All other parameters at 42 days after donation were the same in the two groups of red blood cells. These results suggest that red blood cells stored in mannitol-adenine-phosphate are not significantly affected by helicopter transportation. The differences in haemolysis by the end of storage were small and probably not of clinical significance.

  1. Solar and Drag Sail Propulsion: From Theory to Mission Implementation

    Johnson, Les; Alhorn, Dean; Boudreaux, Mark; Casas, Joe; Stetson, Doug; Young, Roy

    2014-01-01

    Solar and drag sail technology is entering the mainstream for space propulsion applications within NASA and around the world. Solar sails derive propulsion by reflecting sunlight from a large, mirror- like sail made of a lightweight, reflective material. The continuous sunlight pressure provides efficient primary propulsion, without the expenditure of propellant or any other consumable, allowing for very high V maneuvers and long-duration deep space exploration. Drag sails increase the aerodynamic drag on Low Earth Orbit (LEO) spacecraft, providing a lightweight and relatively inexpensive approach for end-of-life deorbit and reentry. Since NASA began investing in the technology in the late 1990's, significant progress has been made toward their demonstration and implementation in space. NASA's Marshall Space Flight Center (MSFC) managed the development and testing of two different 20-m solar sail systems and rigorously tested them under simulated space conditions in the Glenn Research Center's Space Power Facility at Plum Brook Station, Ohio. One of these systems, developed by L'Garde, Inc., is planned for flight in 2015. Called Sunjammer, the 38m sailcraft will unfurl in deep space and demonstrate solar sail propulsion and navigation as it flies to Earth-Sun L1. In the Flight Center (MSFC) managed the development and testing of two different 20-m solar sail systems and rigorously tested them under simulated space conditions in the Glenn Research Center's Space Power Facility at Plum Brook Station, Ohio. One of these systems, developed by L'Garde, Inc., is planned for flight in 2015. Called Sunjammer, the 38m sailcraft will unfurl in deep space and demonstrate solar sail propulsion and navigation as it flies to Earth-Sun L1. In the interim, NASA MSFC funded the NanoSail-D, a subscale drag sail system designed for small spacecraft applications. The NanoSail-D flew aboard the Fast Affordable Science and Technology SATellite (FASTSAT) in 2010, also developed by MSFC

  2. Common aspects and differences in the behaviour of classical configuration versus canard configuration aircraft in the presence of vertical gusts, assuming the hypothesis of an elastic fuselage

    Octavian PREOTU

    2011-06-01

    Full Text Available The paper analyzes, in parallel, common aspects and differences in the behavior of classical configuration versus canard configuration aircraft in the presence of vertical gusts, assuming the hypothesis of an elastic fuselage. The effects of the main constructional dimensions of the horizontal empennage on lift cancelling and horizontal empennage control are being analyzed

  3. 78 FR 66317 - Special Conditions: Learjet Inc. Model LJ-200-1A10; Airplane Fuselage Post-Crash Fire Survivability

    2013-11-05

    ... Existing regulations do not adequately ensure that composite structure offers passengers the same... feature associated with advanced composite materials in the construction of its fuselage and wings. The... Directorate, Aircraft Certification Service, 1601 Lind Avenue SW., Renton, Washington, 98057-3356; telephone...

  4. Comparison of Test Stand and Helicopter Oil Cooler Bearing Condition Indicators

    Dempsey, Paula J.; Branning, Jeremy; Wade, Damiel R.; Bolander, Nathan

    2010-01-01

    The focus of this paper was to compare the performance of HUMS condition indicators (CI) when detecting a bearing fault in a test stand or on a helicopter. This study compared data from two sources: first, CI data collected from accelerometers installed on two UH-60 Black Hawk helicopters when oil cooler bearing faults occurred, along with data from helicopters with no bearing faults; and second, CI data that was collected from ten cooler bearings, healthy and faulted, that were removed from fielded helicopters and installed in a test stand. A method using Receiver Operating Characteristic (ROC) curves to compare CI performance was demonstrated. Results indicated the bearing energy CI responded differently for the helicopter and the test stand. Future research is required if test stand data is to be used validate condition indicator performance on a helicopter.

  5. Analysis of Satellite Drag Coefficient Based on Wavelet Transform

    Liu, Wei; Wang, Ronglan; Liu, Siqing

    Abstract: Drag coefficient sequence was obtained by solving Tiangong1 continuous 55days GPS orbit data with different arc length. The same period solar flux f10.7 and geomagnetic index Ap ap series were high and low frequency multi-wavelet decomposition. Statistical analysis results of the layers sliding correlation between space environmental parameters and decomposition of Cd, showed that the satellite drag coefficient sequence after wavelet decomposition and the corresponding level of f10.7 Ap sequence with good lag correlation. It also verified that the Cd prediction is feasible. Prediction residuals of Cd with different regression models and different sample length were analysed. The results showed that the case was best when setting sample length 20 days and f10.7 regression model were used. It also showed that NRLMSIS-00 model's response in the region of 350km (Tiangong's altitude) and low-middle latitude (Tiangong's inclination) is excessive in ascent stage of geomagnetic activity Ap and is inadequate during fall off segment. Additionally, the low-frequency decomposition components NRLMSIS-00 model's response is appropriate in f10.7 rising segment. High frequency decomposition section, Showed NRLMSIS-00 model's response is small-scale inadequate during f10.7 ascent segment and is reverse in decline of f10.7. Finally, the potential use of a summary and outlook were listed; This method has an important reference value to improve the spacecraft orbit prediction accuracy. Key words: wavelet transform; drag coefficient; lag correlation; Tiangong1;space environment

  6. Resistive Heating and Ion Drag in Saturn's Thermosphere

    Vriesema, Jess William; Koskinen, Tommi; Yelle, Roger V.

    2017-10-01

    One of the most puzzling observations of the jovian planets is that the thermospheres of Jupiter, Saturn, Uranus and Neptune are all several times hotter than solar heating can account for (Strobel and Smith 1973; Yelle and Miller 2004; Muller-Wodarg et al. 2006). On Saturn, resistive heating appears sufficient to explain these temperatures in auroral regions, but the particular mechanism(s) responsible for heating the lower latitudes remains unclear. The most commonly proposed heating mechanisms are breaking gravity waves and auroral heating at the poles followed by redistribution of energy to mid-and low latitudes. Both of these energy sources are potentially important but also come with significant problems. Wave heating would have to be continuous and global to produce consistently elevated temperatures and the strong Coriolis forces coupled with polar ion drag appear to hinder redistribution of auroral energy (see Strobel et al. 2016 for review). Here we explore an alternative: wind-driven electrodynamics that can alter circulation and produce substantial heating outside of the auroral region. Smith (2013) showed this in-situ mechanism to be potentially significant in Jupiter’s thermosphere. We present new results from an axisymmetric, steady-state model that calculates resistive (Joule) heating rates through rigorous solutions of the electrodynamic equations for the coupled neutral atmosphere and ionosphere of Saturn. At present, we assume a dipole magnetic field and neglect any contributions from the magnetosphere. We use ion mixing ratios from the model of Kim et al. (2014) and the observed temperature-pressure profile from Koskinen et al. (2015) to calculate the generalized conductivity tensor as described by Koskinen et al. (2014). We calculate the current density under the assumption that it has no divergence and use it to calculate the resistive heating rates and ion drag. Our results suggest that resistive heating and ion drag at low latitudes likely

  7. A fuselage/tank structure study for actively cooled hypersonic cruise vehicles, summary. [aircraft design of aircraft fuel systems

    Pirrello, C. J.; Baker, A. H.; Stone, J. E.

    1976-01-01

    A detailed analytical study was made to investigate the effects of fuselage cross section (circular and elliptical) and the structural arrangement (integral and nonintegral tanks) on aircraft performance. The vehicle was a 200 passenger, liquid hydrogen fueled Mach 6 transport designed to meet a range goal of 9.26 Mn (5000 NM). A variety of trade studies were conducted in the area of configuration arrangement, structural design, and active cooling design in order to maximize the performance of each of three point design aircraft: (1) circular wing-body with nonintegral tanks, (2) circular wing-body with integral tanks and (3) elliptical blended wing-body with integral tanks. Aircraft range and weight were used as the basis for comparison. The resulting design and performance characteristics show that the blended body integral tank aircraft weights the least and has the greatest range capability, however, producibility and maintainability factors favor nonintegral tank concepts.

  8. Effects of cavity resonances on sound transmission into a thin cylindrical shell. [noise reduction in aircraft fuselage

    Koval, L. R.

    1978-01-01

    In the context of the transmission of airborne noise into an aircraft fuselage, a mathematical model is presented for the effects of internal cavity resonances on sound transmission into a thin cylindrical shell. The 'noise reduction' of the cylinder is defined and computed, with and without including the effects of internal cavity resonances. As would be expected, the noise reduction in the absence of cavity resonances follows the same qualitative pattern as does transmission loss. Numerical results show that cavity resonances lead to wide fluctuations and a general decrease of noise reduction, especially at cavity resonances. Modest internal absorption is shown to greatly reduce the effect of cavity resonances. The effects of external airflow, internal cabin pressurization, and different acoustical properties inside and outside the cylinder are also included and briefly examined.

  9. Signal Separation of Helicopter Radar Returns Using Wavelet-Based Sparse Signal Optimisation

    2016-10-01

    helicopter from the composite radar returns. The received signal consists of returns from the rotating main and tail rotor blades, the helicopter body...is used to separate the main and tail rotor blade components of a helicopter from the composite radar returns. The received signal consists of returns...Two algorithms are presented in the report to separately extract main rotor blade returns and tail rotor blade returns from the composite signal

  10. The Use of Commercial Remote Sensing Systems in Predicting Helicopter Brownout Conditions

    2009-09-01

    REFERENCES Anthoni, J. F. (2000). Soil Erosion and Conservation – Part 2. Retrieved 15 August 2009, from http://www.seafriends.org.nz/ enviro / soil ... soils susceptible to helicopter brownout. Helicopter brownout occurs when downwash disturbs the dust and sand beneath the aircraft during takeoff...destruction, as well as personnel injury or death. The likelihood of helicopter brownout is related to soil moisture content, particle size distribution, and

  11. A general method for closed-loop inverse simulation of helicopter maneuver flight

    Wei WU

    2017-01-01

    Maneuverability is a key factor to determine whether a helicopter could finish certain flight missions successfully or not. Inverse simulation is commonly used to calculate the pilot controls of a helicopter to complete a certain kind of maneuver flight and to assess its maneuverability. A general method for inverse simulation of maneuver flight for helicopters with the flight control system online is developed in this paper. A general mathematical describing function is established to provid...

  12. Satellite Orbit Under Influence of a Drag - Analytical Approach

    Martinović, M. M.; Šegan, S. D.

    2017-12-01

    The report studies some changes in orbital elements of the artificial satellites of Earth under influence of atmospheric drag. In order to develop possibilities of applying the results in many future cases, an analytical interpretation of the orbital element perturbations is given via useful, but very long expressions. The development is based on the TD88 air density model, recently upgraded with some additional terms. Some expressions and formulae were developed by the computer algebra system Mathematica and tested in some hypothetical cases. The results have good agreement with iterative (numerical) approach.

  13. Air Flows in Gravity Sewers - Determination of Wastewater Drag Coefficient

    Bentzen, Thomas Ruby; Østertoft, Kristian; Vollertsen, Jes

    2016-01-01

    Several experiments have been conducted in order to improve the understanding of the wastewater drag and the wall frictional force acting on the headspace air in gravity sewers. The aim of the study is to improve the data basis for a numerical model of natural sewer ventilation. The results...... of the study shows that by integrating the top/side wall shear stresses the log-law models for the air velocity distribution along the unwetted perimeter resulted in a good agreement with the friction forces calculated by use of the Colebrook-White formula for hydraulic smooth pipes. Secondly, the water...

  14. Drag Reduction trough Special paints Coated on the hull

    Izaguirre Alza, Patricia; Pérez Rojas, Luis; Núñez Basáñez, José Fernando

    2010-01-01

    The economic recession, the environmental impact as well as the continuous fossil fuel consumption encourage actions that focus on saving energy. In the vessels sector, one of the main objectives has always been to reach a hydro-dynamically optimum hull which gave the desired speed with minimum power. Hydrodynamic drag is basically divided into two parts: a) the friction between the water and the hull, and b) the wave generation due to the free-surface air-water. Presented in this paper...

  15. Drag prediction for blades at high angle of attack using CFD

    Sørensen, Niels N.; Michelsen, J.A.

    2004-01-01

    In the present paper it is first demonstrated that state of the art 3D CFD codes are. capable of predicting the correct dependency of the integrated drag of a flat plate placed perpendicular to the flow. This is in strong contrast to previous 2D investigations of infinite plates, where computations...... are known to severely overpredict drag. We then demonstrate that the computed drag distribution along the plate span deviate from the general expectation of 2D behavior at the central part of the plate, an important finding in connection with the theoretical estimation of drag behavior on wind turbine...... blades. The computations additionally indicate that a tip effect is present that produces increased drag near the end of the plate, which is opposite of the assumptions generally used in drag estimation for blades. Following this several wind turbine blades are analyzed, ranging from older blades...

  16. Nonuniform charging effects on ion drag force in drifting dusty plasmas

    Chang, Dong-Man; Chang, Won-Seok; Jung, Young-Dae

    2006-01-01

    The nonuniform polarization charging effects on the ion drag force are investigated in drifting dusty plasmas. The ion drag force due to the ion-dust grain interaction is obtained as a function of the dust charge, ion charge, plasma temperature, Mach number, Debye length, and collision energy. The result shows that the nonuniform charging effects enhance the momentum transfer cross section as well as the ion drag force. It is found that the momentum transfer cross section and the ion drag force including nonuniform polarization charging effects increase with increasing the Mach number and also the ion drag force increases with increasing the temperature. In addition, it is found that the ion drag force is slightly decreasing with an increase of the Debye length

  17. Frictional Magneto-Coulomb Drag in Graphene Double-Layer Heterostructures.

    Liu, Xiaomeng; Wang, Lei; Fong, Kin Chung; Gao, Yuanda; Maher, Patrick; Watanabe, Kenji; Taniguchi, Takashi; Hone, James; Dean, Cory; Kim, Philip

    2017-08-04

    Coulomb interaction between two closely spaced parallel layers of conductors can generate the frictional drag effect by interlayer Coulomb scattering. Employing graphene double layers separated by few-layer hexagonal boron nitride, we investigate density tunable magneto- and Hall drag under strong magnetic fields. The observed large magnetodrag and Hall-drag signals can be related with Laudau level filling status of the drive and drag layers. We find that the sign and magnitude of the drag resistivity tensor can be quantitatively correlated to the variation of magnetoresistivity tensors in the drive and drag layers, confirming a theoretical formula for magnetodrag in the quantum Hall regime. The observed weak temperature dependence and ∼B^{2} dependence of the magnetodrag are qualitatively explained by Coulomb scattering phase-space argument.

  18. Aerodynamic Efficiency Analysis on Modified Drag Generator of Tanker-Ship Using Symmetrical Airfoil

    Moranova, Starida; Rahmat Hadiyatul A., S. T.; Indra Permana S., S. T.

    2018-04-01

    Time reduction of tanker ship spent in the sea should be applied for solving problems occured in oil and gas distribution, such as the unpunctuality of the distribution and oil spilling. The aerodynamic design for some parts that considered as drag generators is presumed to be one of the solution, utilizing our demand of the increasing speed. This paper suggests two examples of the more-aerodynamic design of a part in the tanker that is considered a drag generator, and reports the value of drag generated from the basic and the suggested aerodynamic designs. The new designs are made by adding the NACA airfoil to the cross section of the drag generator. The scenario is assumed with a 39 km/hour speed of tanker, neglecting the hydrodynamic effects occured in the tanker by cutting it at the waterline which separated the drag between air and water. The results of produced drag in each design are calculated by Computational Fluid Dynamic method.

  19. Ad/dressing the nation: drag and authenticity in post-apartheid South Africa.

    Spruill, Jennifer

    2004-01-01

    This paper examines a style of drag in South Africa that features "traditional African" clothing. In a region in which homosexuality is denigrated as a colonial, European import and "unAfrican," the meaning of "traditional drag" is deeply inflected by the question of cultural authenticity. This dragging practice fits within a distinctly post-colonial production of tradition and its self-conscious display--in the form of attire--of a decidedly "gay" one. Traditional drag also responds to ongoing politics within and between lesbian and gay communities about racial "representivity" and "transformation." The paper focuses on displays of traditional drag at Johannesburg's Gay and Lesbian Pride Parade but also explores the complex politics of publicity and address suggested by varying contexts in which traditional dress and drag are mobilized.

  20. Hypersonic wave drag reduction performance of cylinders with repetitive laser energy depositions

    Fang, J; Hong, Y J; Li, Q; Huang, H

    2011-01-01

    It has been widely research that wave drag reduction on hypersonic vehicle by laser energy depositions. Using laser energy to reduce wave drag can improve vehicle performance. A second order accurate scheme based on finite-difference method and domain decomposition of structural grid is used to compute the drag performance of cylinders in a hypersonic flow of Mach number 2 at altitude of 15km with repetitive energy depositions. The effects of frequency on drag reduction are studied. The calculated results show: the recirculation zone is generated due to the interaction between bow shock over the cylinder and blast wave produced by energy deposition, and a virtual spike which is supported by an axis-symmetric recirculation, is formed in front of the cylinder. By increasing the repetitive frequency, the drag is reduced and the oscillation of the drag is decreased; however, the energy efficiency decreases by increasing the frequency.

  1. Synthetic Effect of Vivid Shark Skin and Polymer Additive on Drag Reduction Reinforcement

    Huawei Chen

    2014-06-01

    Full Text Available Natural shark skin has a well-demonstrated drag reduction function, which is mainly owing to its microscopic structure and mucus on the body surface. In order to improve drag reduction, it is necessary to integrate microscopic drag reduction structure and drag reduction agent. In this study, two hybrid approaches to synthetically combine vivid shark skin and polymer additive, namely, long-chain grafting and controllable polymer diffusion, were proposed and attempted to mimic such hierarchical topography of shark skin without waste of polymer additive. Grafting mechanism and optimization of diffusion port were investigated to improve the efficiency of the polymer additive. Superior drag reduction effects were validated, and the combined effect was also clarified through comparison between drag reduction experiments.

  2. Numerical Study of Natural Supercavitation Influenced by Rheological Properties of Turbulent Drag-Reducing Additives

    Chen-Xing Jiang

    2014-08-01

    Full Text Available Natural supercavitations in water and turbulent drag-reducing solution were numerically simulated using unsteady Reynolds averaged Navier-Stokes (RANS scheme with mixture-multiphase model. The Cross viscosity equation was adopted to represent the fluid property of aqueous solution of drag-reducing additives. The characteristics of natural supercavity configuration and overall resistance of the navigating body were presented, respectively. The numerical simulation results indicated that, at the same cavitation number, the length and diameter of supercavity in drag-reducing solution are larger than those in water, and the drag coefficient of navigating body in solution is smaller than that in water; the surface tension plays an important role in incepting and maintaining the cavity. Turbulent drag-reducing additives have the potential in enhancement of supercavitation, drag reduction, and decrease of turbulent vortex structures. Numerical simulation results are consistent with the available experimental data.

  3. CFD Prediction of Airfoil Drag in Viscous Flow Using the Entropy Generation Method

    Wei Wang

    2018-01-01

    Full Text Available A new aerodynamic force of drag prediction approach was developed to compute the airfoil drag via entropy generation rate in the flow field. According to the momentum balance, entropy generation and its relationship to drag were derived for viscous flow. Model equations for the calculation of the local entropy generation in turbulent flows were presented by extending the RANS procedure to the entropy balance equation. The accuracy of algorithm and programs was assessed by simulating the pressure coefficient distribution and dragging coefficient of different airfoils under different Reynolds number at different attack angle. Numerical data shows that the total entropy generation rate in the flow field and the drag coefficient of the airfoil can be related by linear equation, which indicates that the total drag could be resolved into entropy generation based on its physical mechanism of energy loss.

  4. Optimal control of helicopters following power failure. Helicopter no engine koshoji no saiteki hiko seigyo

    Okuno, Y.

    1993-01-01

    In order to study the optimal control of helicopters, the control procedures following power failure were theoretically investigated by applying nonlinear optimal control theory to the following four optimization problems. The first was minimization of the touchdown speed following power failure. Comparisons between the calculated optimal solutions and the empirical flight test results showed that pilots used nonoptimal controls, especially in the timing and amplitude of the collective flare before touchdowns. The second was prediction of the height-velocity (H-V) boundaries. The calculated H-V boundaries showed good correlation with the flight test results. The third was optimization of the takeoff procedures for category A STOL operation following power failure. The results showed that the required takeoff distance using the normal takeoff procedure can be significantly reduced. The fourth was evaluation of the takeoff performance for category A VTOL operation. The calculating method of the maximum takeoff weight was confirmed, and possibility of allowing the payload to be increased was shown. 38 refs., 53 figs.

  5. The Role of Rough Topography in Mediating Impacts of Bottom Drag in Eddying Ocean Circulation Models.

    Trossman, David S; Arbic, Brian K; Straub, David N; Richman, James G; Chassignet, Eric P; Wallcraft, Alan J; Xu, Xiaobiao

    2017-08-01

    Motivated by the substantial sensitivity of eddies in two-layer quasi-geostrophic (QG) turbulence models to the strength of bottom drag, this study explores the sensitivity of eddies in more realistic ocean general circulation model (OGCM) simulations to bottom drag strength. The OGCM results are interpreted using previous results from horizontally homogeneous, two-layer, flat-bottom, f-plane, doubly periodic QG turbulence simulations and new results from two-layer β -plane QG turbulence simulations run in a basin geometry with both flat and rough bottoms. Baroclinicity in all of the simulations varies greatly with drag strength, with weak drag corresponding to more barotropic flow and strong drag corresponding to more baroclinic flow. The sensitivity of the baroclinicity in the QG basin simulations to bottom drag is considerably reduced, however, when rough topography is used in lieu of a flat bottom. Rough topography reduces the sensitivity of the eddy kinetic energy amplitude and horizontal length scales in the QG basin simulations to bottom drag to an even greater degree. The OGCM simulation behavior is qualitatively similar to that in the QG rough bottom basin simulations in that baroclinicity is more sensitive to bottom drag strength than are eddy amplitudes or horizontal length scales. Rough topography therefore appears to mediate the sensitivity of eddies in models to the strength of bottom drag. The sensitivity of eddies to parameterized topographic internal lee wave drag, which has recently been introduced into some OGCMs, is also briefly discussed. Wave drag acts like a strong bottom drag in that it increases the baroclinicity of the flow, without strongly affecting eddy horizontal length scales.

  6. On the influence of drag effect on acoustic modes in two-condensate relativistic superfluid systems

    Vil'chinskij, S.I.

    1999-01-01

    Equations of velocities of acoustic excitations in a relativistic two-condensate superfluid system are derived with due account of reciprocal drag of superfluid motion (drag effect). The influence of the drag effect on acoustic modes in the system is considered. It is shown that the effect does not influence the nature of acoustic excitation oscillations but produces changes in the velocities of the second, third and fourth sounds

  7. Direct Self-Repairing Control for Quadrotor Helicopter Attitude Systems

    Huiliao Yang

    2014-01-01

    Full Text Available A quadrotor helicopter with uncertain actuator faults, such as loss of effectiveness and lock-in-place, is studied in this paper. An adaptive fuzzy sliding mode controller based on direct self-repairing control is designed for such nonlinear system to track the desired output signal, when any actuator of this quadrotor helicopter is loss of effectiveness or stuck at some place. Moreover, using the Lyapunov stability theory, the stability of the whole system and the convergence of the tracking error can be guaranteed. Finally, the availability of the proposed method is verified by simulation on 3-DOF hover to ensure that the system performance under faulty conditions can be quickly recovered to its normal level. And this proposed method is also proved to be better than that of LQR through simulation.

  8. NASA/FAA experiments concerning helicopter IFR airworthiness criteria

    Lebacqz, J. V.

    1983-01-01

    A sequence of ground and flight simulation experiments was conducted as part of a joint NASA/FAA program to investigate helicopter instrument flight rules (IFR) airworthiness criteria. The first six of these experiments are described and the results summarized. Five of the experiments were conducted on large amplitude motion base simulators; V/STOLAND UH-1H variable stability helicopter was used in the flight experiment. Airworthiness implications of selected variables that were investigated across all of the experiments are discussed, including the level of longitudinal static stability, the type of stability and control augmentation, the addition of flight director displays, and the type of instrument approach task. Among the specific results reviewed are the adequacy of neutral longitudinal statics for dual pilot approaches and the requirement for pitch and roll attitude stabilization in the stability and control augmentation system to achieve flying qualities evaluated as satisfactory.

  9. A Maneuvering Flight Noise Model for Helicopter Mission Planning

    Greenwood, Eric; Rau, Robert; May, Benjamin; Hobbs, Christopher

    2015-01-01

    A new model for estimating the noise radiation during maneuvering flight is developed in this paper. The model applies the Quasi-Static Acoustic Mapping (Q-SAM) method to a database of acoustic spheres generated using the Fundamental Rotorcraft Acoustics Modeling from Experiments (FRAME) technique. A method is developed to generate a realistic flight trajectory from a limited set of waypoints and is used to calculate the quasi-static operating condition and corresponding acoustic sphere for the vehicle throughout the maneuver. By using a previously computed database of acoustic spheres, the acoustic impact of proposed helicopter operations can be rapidly predicted for use in mission-planning. The resulting FRAME-QS model is applied to near-horizon noise measurements collected for the Bell 430 helicopter undergoing transient pitch up and roll maneuvers, with good agreement between the measured data and the FRAME-QS model.

  10. Helicopter Acoustic Flight Test with Altitude Variation and Maneuvers

    Watts, Michael E.; Greenwood, Eric; Sim, Ben; Stephenson, James; Smith, Charles D.

    2016-01-01

    A cooperative flight test campaign between NASA and the U.S. Army was performed from September 2014 to February 2015. The purposes of the testing were to: investigate the effects of altitude variation on noise generation, investigate the effects of gross weight variation on noise generation, establish the statistical variability in acoustic flight testing of helicopters, and characterize the effects of transient maneuvers on radiated noise for a medium-lift utility helicopter. This test was performed at three test sites (0, 4000, and 7000 feet above mean sea level) with two aircraft (AS350 SD1 and EH-60L) tested at each site. This report provides an overview of the test, documents the data acquired and describes the formats of the stored data.

  11. Application of Face-Gear Drives in Helicopter Transmissions

    Litvin, F. L.; Wang, J.-C.; Bossler, R. B., Jr.; Chen, Y.-J. D.; Heath, G.; Lewicki, D. G.

    1992-01-01

    The use of face gears in helicopter transmissions was explored. A light-weight, split torque transmission design utilizing face gears was described. Face-gear design and geometry were investigated. Topics included tooth generation, limiting inner and outer radii, tooth contact analysis, contact ratio, gear eccentricity, and structural stiffness. Design charts were developed to determine minimum and maximum face-gear inner and outer radii. Analytical study of transmission error showed face-gear drives were relatively insensitive to gear misalignment, but tooth contact was affected by misalignment. A method of localizing bearing contact to compensate for misalignment was explored. The proper choice of shaft support stiffness enabled good load sharing in the split torque transmission design. Face-gear experimental studies were also included and the feasibility of face gears in high-speed, high-load applications such as helicopter transmissions was demonstrated.

  12. Towards a better understanding of helicopter external noise

    Damongeot, A.; Dambra, F.; Masure, B.

    The problem of helicopter external noise generation is studied taking into consideration simultaneously the multiple noise sources: rotor rotational-, rotor broadband -, and engine noise. The main data are obtained during flight tests of the rather quiet AS 332 Super Puma. The flight procedures settled by ICAO for noise regulations are used: horizontal flyover at 90 percent of the maximum speed, approach at minimum power velocity, take-off at best rate of climb. Noise source levels are assessed through narrow band analysis of ground microphone recordings, ground measurements of engine noise and theoretical means. With the perceived noise level unit used throughout the study, relative magnitude of noise sources is shown to be different from that obtained with linear noise unit. A parametric study of the influence of some helicopter parameters on external noise has shown that thickness-tapered, chord-tapered, and swept-back blade tips are good means to reduce the overall noise level in flyover and approach.

  13. Drag Moderation by the Melting of an Ice Surface in Contact with Water

    Vakarelski, Ivan Uriev

    2015-07-24

    We report measurements of the effects of a melting ice surface on the hydrodynamic drag of ice-shell-metal-core spheres free falling in water at a Reynolds of number Re∼2×104–3×105 and demonstrate that the melting surface induces the early onset of the drag crisis, thus reducing the hydrodynamic drag by more than 50%. Direct visualization of the flow pattern demonstrates the key role of surface melting. Our observations support the hypothesis that the drag reduction is due to the disturbance of the viscous boundary layer by the mass transfer from the melting ice surface.

  14. Experimental and numerical investigation of low-drag intervals in turbulent boundary layer

    Park, Jae Sung; Ryu, Sangjin; Lee, Jin

    2017-11-01

    It has been widely investigated that there is a substantial intermittency between high and low drag states in wall-bounded shear flows. Recent experimental and computational studies in a turbulent channel flow have identified low-drag time intervals based on wall shear stress measurements. These intervals are a weak turbulence state characterized by low-speed streaks and weak streamwise vortices. In this study, the spatiotemporal dynamics of low-drag intervals in a turbulent boundary layer is investigated using experiments and simulations. The low-drag intervals are monitored based on the wall shear stress measurement. We show that near the wall conditionally-sampled mean velocity profiles during low-drag intervals closely approach that of a low-drag nonlinear traveling wave solution as well as that of the so-called maximum drag reduction asymptote. This observation is consistent with the channel flow studies. Interestingly, the large spatial stretching of the streak is very evident in the wall-normal direction during low-drag intervals. Lastly, a possible connection between the mean velocity profile during the low-drag intervals and the Blasius profile will be discussed. This work was supported by startup funds from the University of Nebraska-Lincoln.

  15. Drag Moderation by the Melting of an Ice Surface in Contact with Water

    Vakarelski, Ivan Uriev; Chan, Derek Y.  C.; Thoroddsen, Sigurdur T

    2015-01-01

    We report measurements of the effects of a melting ice surface on the hydrodynamic drag of ice-shell-metal-core spheres free falling in water at a Reynolds of number Re∼2×104–3×105 and demonstrate that the melting surface induces the early onset of the drag crisis, thus reducing the hydrodynamic drag by more than 50%. Direct visualization of the flow pattern demonstrates the key role of surface melting. Our observations support the hypothesis that the drag reduction is due to the disturbance of the viscous boundary layer by the mass transfer from the melting ice surface.

  16. Modelling of Structural Loads in Drag Augmented Space Debris Removal Concepts

    Kristensen, Anders Schmidt; Nikolajsen, Jan Ánike; Lauridsen, Peter Riddersholm

    2017-01-01

    A Self-deployable Deorbiting Space Structure (SDSS) is used for drag augmented space debris removal. A highly flexible frame allows for a folding of the structure by bifurcation. This research models the structural loads during the deployment and unfolding of the drag sail in Low Earth Orbit (LEO......). The Spacecraft travels with 7.8 km/s at deployment. As the drag sail unfolds instantaneously the structure must withstand the loads from the unfolding and the drag. Thermal loads are included in the FEA as the temperature varies from -80°C to +80°C during deorbit. The results are used to verify the structural...

  17. Further development of drag bodies for the measurement of mass flow rates during blowdown experiments

    Brockmann, E.; John, H.; Reimann, J.

    1983-01-01

    Drag bodies have already been used for sometime for the measurement of mass flow rates in blowdown experiments. Former research concerning the drag body behaviour in non-homogeneous two-phase flows frequently dealt with special effects by means of theoretical models only. For pipe flows most investigations were conducted for ratios of drag plate area to pipe cross section smaller 0.02. The present paper gives the results of experiments with drag bodies in a horizontal, non-homogeneous two-phase pipe flow with slip, which were carried through under the sponsorship of the German Ministry for Research and Technology (BMFT). Special interest was layed on the behaviour of the drag coefficient in stationary flows and at various cross sectional ratios. Both design and response of various drag bodies, which were developed at the Battelle-Institut, were tested in stationary and instationary two-phase flows. The influences of density and velocity profiles as well as the drag body position were studied. The results demonstrate, that the drag body is capable of measuring mass flow rates in connection with a gamma densitometer also in non-homogeneous two-phase flows. Satisfying results could be obtained, using simply the drag coefficient which was determined from single-phase flow calibrations

  18. Concentrated energy addition for active drag reduction in hypersonic flow regime

    Ashwin Ganesh, M.; John, Bibin

    2018-01-01

    Numerical optimization of hypersonic drag reduction technique based on concentrated energy addition is presented in this study. A reduction in wave drag is realized through concentrated energy addition in the hypersonic flowfield upstream of the blunt body. For the exhaustive optimization presented in this study, an in-house high precision inviscid flow solver has been developed. Studies focused on the identification of "optimum energy addition location" have revealed the existence of multiple minimum drag points. The wave drag coefficient is observed to drop from 0.85 to 0.45 when 50 Watts of energy is added to an energy bubble of 1 mm radius located at 74.7 mm upstream of the stagnation point. A direct proportionality has been identified between energy bubble size and wave drag coefficient. Dependence of drag coefficient on the upstream added energy magnitude is also revealed. Of the observed multiple minimum drag points, the energy deposition point (EDP) that offers minimum wave drag just after a sharp drop in drag is proposed as the most optimum energy addition location.

  19. Monte Carlo calculations of the free-molecule drag on chains of uniform spheres

    Dahneke, B.; Chan, P.

    1980-01-01

    Monte Carlo calculations of the free-molecule drag on straight chains of uniform spheres are presented. The drag on a long chain is expressed in terms of the drag on a basic chain unit (two hemispheres touching at their poles) multiplied by the number of spheres in the chain. Since there is no interaction between the basic chain units, it is argued that the results also apply as a good approximation to the drag on kinked and branched chains covering a broad range of geometries. Experimental data are cited which support this claim

  20. Experimental Investigation of the Fresnel Drag Effect in RF Coaxial Cables

    Cahill R. T.

    2011-01-01

    Full Text Available An experiment that confirms the Fresnel drag formalism in RF coaxial cables is re- ported. The Fresnel ‘drag’ in bulk dielectrics and in optical fibers has previously been well established. An explanation for this formalism is given, and it is shown that there is no actual drag phenomenon, rather that the Fresnel drag effect is merely the conse- quence of a simplified description of EM scattering within a dielectric in motion wrt the dynamical 3-space. The Fresnel drag effect plays a critical role in the design of various light-speed anisotropy detectors.

  1. INVESTINGATION DOWNWARD WIND PRESSURE ON A SMALL QUADROTOR HELICOPTER

    RAHMATI, Sadegh; GHASED, Amir

    2015-01-01

    Abstract. Small rotary-wing UAVs are susceptible to gusts and other environmental disturbances that affect inflow at their rotors. Inflow variations cause unexpected aerodynamic forces through changes in thrust conditions and unmodeled blade-flapping dynamics. This pa­per introduces an onboard, pressure-based flow measurement system developed for a small quadrotor helicopter. The probe-based instrumentation package provides spatially dis­tributed airspeed measurements along each of the aircra...

  2. Conservative Management of Mechanical Neck Pain in a Helicopter Pilot.

    Alagha, Babak

    2015-10-01

    Acute and chronic spinal symptoms such as neck pain may limit flying performance significantly and disqualify the pilot from flight duty. Mechanical neck pain is very common among pilots because of their exposure to vibration, +GZ forces, helmet weight, poor neck posture during air combat maneuvers, previous neck injuries, and poor treatment plans for such injuries. Successful treatment of such injuries requires appropriate therapeutic procedures as well as an aeromedical assessment. The aim of this case study was to demonstrate the benefits of conservative procedures such as spinal manipulation and mobilization therapy (SMMT) and exercise therapy (ET) in treating chronic mechanical neck pain in an Iranian commercial helicopter pilot. A 36-yr-old male patient presented to the clinic with moderate, intermittent nonradicular chronic neck pain and limited range of motion over a 2-yr period. The patient was treated with cervical and upper thoracic SMMT followed by home ET for 5 wk. After this period, the patient reported significant recovery and improvement in range of motion in his neck. Mechanical neck pain is very common among helicopter pilots. Although Air Force and Navy waiver guides recommend nonsteroidal anti-inflammatory medications as well as SMMT and ET, there are currently very few published studies that examine the benefits of manual and exercise therapy for treating mechanical neck pain in commercial and military pilots. Based on the results of this study, it seems that SMMT and ET may be a safe and effective in treatment of uncomplicated mechanical neck pain in helicopter pilots. Alagha B. Conservative management of mechanical neck pain in a helicopter pilot.

  3. Exploration of Configuration Options for a Large Civil Compound Helicopter

    Russell, Carl; Johnson, Wayne

    2013-01-01

    Multiple compound helicopter configurations are designed using a combination of rotorcraft sizing and comprehensive analysis codes. Results from both the conceptual design phase and rotor comprehensive analysis are presented. The designs are evaluated for their suitability to a short-to-medium-haul civil transport mission carrying a payload of 90 passengers. Multiple metrics are used to determine the best configuration, with heavy emphasis placed on minimizing fuel burn.

  4. 78 FR 25365 - Airworthiness Directives; Eurocopter France Helicopters

    2013-05-01

    ... this AD, do not install any of the following parts on any helicopter: (i) Left-hand sliding door, part number (P/N) 350A25-0030-00XX, 350A25-0120-00XX, and 350AMR-0227-0052; (ii) Right-hand sliding door, P/N... following a case of total failure and a case of a crack discovered on the support shaft of the sliding door...

  5. Helicopter Fatigue. A Review of Current Requirements and Substantiation Procedures

    1979-01-01

    stress versus cycles to failure (S/N) method of testing and verification. A mi..iimum of six test specimens is required to establish the mean curve with...Approach) A.D. Hall B.Sc., C.Eng., M.R.Ae.S. 4 Chief Stress Engineer (Dynamic Components) Westland Helicopters Limited, Yeovil, Somerset, England...airworthiness requirements concerning the fatifue strength of British milltary nelicopters are embodied in the U.K. Ministry Documents Aviation Publication

  6. Helicopter precision approach capability using the Global Positioning System

    Kaufmann, David N.

    1992-01-01

    The period between 1 July and 31 December, 1992, was spent developing a research plan as well as a navigation system document and flight test plan to investigate helicopter precision approach capability using the Global Positioning System (GPS). In addition, all hardware and software required for the research was acquired, developed, installed, and verified on both the test aircraft and the ground-based reference station.

  7. Failure Analysis of a Helicopter External Fuel-Tank Pylon

    Newman, John A.; Piascik, Robert S.; Lindenberg, Richard A.

    2002-01-01

    An eight-inch-long (0.2 m) crack was found in an external fuel-tank pylon of a U.S. Coast Guard HH-60 helicopter. The damaged pylon was removed from service and destructively examined at NASA Langley Research Center (LaRC) to determine the cause of the crack. Results of the analysis revealed that crack initiation occurred at corrosion pits in a fastener hole and crack propagation was a result of cyclic loading.

  8. Incorporating modelled subglacial hydrology into inversions for basal drag

    C. P. Koziol

    2017-12-01

    Full Text Available A key challenge in modelling coupled ice-flow–subglacial hydrology is initializing the state and parameters of the system. We address this problem by presenting a workflow for initializing these values at the start of a summer melt season. The workflow depends on running a subglacial hydrology model for the winter season, when the system is not forced by meltwater inputs, and ice velocities can be assumed constant. Key parameters of the winter run of the subglacial hydrology model are determined from an initial inversion for basal drag using a linear sliding law. The state of the subglacial hydrology model at the end of winter is incorporated into an inversion of basal drag using a non-linear sliding law which is a function of water pressure. We demonstrate this procedure in the Russell Glacier area and compare the output of the linear sliding law with two non-linear sliding laws. Additionally, we compare the modelled winter hydrological state to radar observations and find that it is in line with summer rather than winter observations.

  9. Bluff-body drag reduction using a deflector

    Fourrie, Gregoire; Keirsbulck, Laurent; Labraga, Larbi [Univ Lille Nord de France, Lille (France); UVHC, TEMPO, Valenciennes (France); Gillieron, Patrick [Fluid Mechanics and Aerodynamics, Renault Group, Research Division, Guyancourt (France)

    2011-02-15

    A passive flow control on a generic car model was experimentally studied. This control consists of a deflector placed on the upper edge of the model rear window. The study was carried out in a wind tunnel at Reynolds numbers based on the model height of 3.1 x 10{sup 5} and 7.7 x 10{sup 5}. The flow was investigated via standard and stereoscopic particle image velocimetry, Kiel pressure probes and surface flow visualization. The aerodynamic drag was measured using an external balance and calculated using a wake survey method. Drag reductions up to 9% were obtained depending on the deflector angle. The deflector increases the separated region on the rear window. The results show that when this separated region is wide enough, it disrupts the development of the counter-rotating longitudinal vortices appearing on the lateral edges of the rear window. The current study suggests that flow control on such geometries should consider all the flow structures that contribute to the model wake flow. (orig.)

  10. Bluff-body drag reduction using a deflector

    Fourrié, Grégoire; Keirsbulck, Laurent; Labraga, Larbi; Gilliéron, Patrick

    2011-02-01

    A passive flow control on a generic car model was experimentally studied. This control consists of a deflector placed on the upper edge of the model rear window. The study was carried out in a wind tunnel at Reynolds numbers based on the model height of 3.1 × 105 and 7.7 × 105. The flow was investigated via standard and stereoscopic particle image velocimetry, Kiel pressure probes and surface flow visualization. The aerodynamic drag was measured using an external balance and calculated using a wake survey method. Drag reductions up to 9% were obtained depending on the deflector angle. The deflector increases the separated region on the rear window. The results show that when this separated region is wide enough, it disrupts the development of the counter-rotating longitudinal vortices appearing on the lateral edges of the rear window. The current study suggests that flow control on such geometries should consider all the flow structures that contribute to the model wake flow.

  11. CAPTURE OF PLANETESIMALS BY GAS DRAG FROM CIRCUMPLANETARY DISKS

    Fujita, Tetsuya; Ohtsuki, Keiji; Suetsugu, Ryo; Tanigawa, Takayuki

    2013-01-01

    Growing giant planets have circumplanetary disks around them in the late stage of their formation if their mass is sufficiently large. We examine capture of relatively large planetesimals that are decoupled from the gas inflow, due to gas drag from a circumplanetary disk of a growing giant planet. Assuming that the structure of the circumplanetary disk is axisymmetric, and solving the three-body problem including gas drag, we perform analytic and numerical calculations for capture of planetesimals. When planetesimal random velocity is small, planetesimals approaching in the retrograde direction are more easily captured, owing to their larger velocity relative to the gas. Planetesimals with large orbital inclinations interact with the disk for a short period of time and show lower capture rates. The effect of ablation on capture rates seems insignificant, although mass loss due to ablation would be significant in the case of high random velocity. We also examine the effect of non-uniform radial distribution of planetesimals in the protoplanetary disk due to gap opening by the planet. When the random velocity of planetesimals is small, the planetesimal capture rate decreases rapidly as the half width of the gap in the planetesimal disk increases from two planetary Hill radii to three planetary Hill radii; planetesimals with low random velocities cannot approach the planet in the case of a sufficiently wide gap. Our results show that the radial distribution and random velocity of planetesimals in the protoplanetary disk are essentially important for the understanding of capture of planetesimals by circumplanetary disks

  12. Drag reduction in silica nanochannels induced by graphitic wall coatings

    Wagemann, Enrique; Walther, J. H.; Zambrano, Harvey A.

    2017-11-01

    Transport of water in hydrophilic nanopores is of significant technological and scientific interest. Water flow through hydrophilic nanochannels is known to experience enormous hydraulic resistance. Therefore, drag reduction is essential for the development of highly efficient nanofluidic devices. In this work, we propose the use of graphitic materials as wall coatings in hydrophilic silica nanopores. Specifically, by conducting atomistic simulations, we investigate the flow inside slit and cylindrical silica channels with walls coated with graphene (GE) layers and carbon nanotubes (CNTs), respectively. We develop realistic force fields to simulate the systems of interest and systematically, compare flow rates in coated and uncoated nanochannels under different pressure gradients. Moreover, we assess the effect that GE and CNT translucencies to wettability have on water hydrodynamics in the nanochannels. The influence of channel size is investigated by systematically varying channel heights and nanopore diameters. In particular, we present the computed water density and velocity profiles, volumetric flow rates, slip lengths and flow enhancements, to clearly demonstrate the drag reduction capabilities of graphitic wall coatings. We wish to thank partial funding from CRHIAM Conicyt/ Fondap Project 15130015 and computational support from DTU and NLHPC (Chile).

  13. Studies of drag on the nanocomposite superhydrophobic surfaces

    Brassard, Jean-Denis; Sarkar, D. K.; Perron, Jean

    2015-01-01

    The nanocomposite thin films of stearic acid (SA)-functionalized ZnO nanoparticles incorporated in epoxy polymer matrix have been achieved. The X-ray diffraction (XRD) studies show the formation of zinc stearate on ZnO nanoparticles as the confirmation of SA-functionalization of ZnO nanoparticles in the thin films. Morphological analyses reveal the presence of micro-holes with the presence of irregular nanoparticles. The measured root mean square (rms) roughness of the thin film is found to be 12 ± 1 μm with the adhesion of 5B on both glass and aluminum substrates. The wetting property shows that the surface of the film is superhydrophobic with the contact angle of water of 156 ± 4° having contact angle hysteresis (CAH) of 4 ± 2°. The average terminal velocity in the water of the as-received glass spheres and superhydrophobic spheres were found to be 0.66 ± 0.01 m/s and 0.72 ± 0.01 m/s respectively. Consequently, the calculated average coefficients of the surface drag of the as-received glass sphere and superhydrophobic glass sphere were 2.30 ± 0.01 and 1.93 ± 0.03, respectively. Hence, the drag reduction on the surface of superhydrophobic glass sphere is found to be approximately 16% lower than as-received glass sphere.

  14. Vertical, radial and drag force analysis of superconducting magnetic bearings

    Cansiz, Ahmet

    2009-01-01

    The behavior of the force between a permanent magnet (PM) and a high temperature superconductor (HTS) was tested with the frozen-image model based on flux pinning. It was found that the associated dipole moment assumptions of the method of the frozen image underestimate the force somewhat; thus a quadrupole moment analysis is proposed. The radial and drag forces associated with the rotation of the PM levitated above the HTS were measured by using a force transducer and by means of a cantilevered beam technique. The radial force was found not to be dependent on the radial direction, and the least radial force was found to be periodic with an angular displacement during the slow rotation of the PM relative to the HTS. The periodicity behavior of the force is attributed to the geometric eccentricity from the magnetization distribution of the PM and HTS. The drag force associated with the torsional stiffness of the levitated PM during the low and high rotational speeds was incorporated with the data from the literature.

  15. Drag reduction of a rapid vehicle in supercavitating flow

    D. Yang

    2017-01-01

    Full Text Available Supercavitation is one of the most attractive technologies to achieve high speed for underwater vehicles. However, the multiphase flow with high-speed around the supercavitating vehicle (SCV is difficult to simulate accurately. In this paper, we use modified the turbulent viscosity formula in the Standard K-Epsilon (SKE turbulent model to simulate the supercavitating flow. The numerical results of flow over several typical cavitators are in agreement with the experimental data and theoretical prediction. In the last part, a flying SCV was studied by unsteady numerical simulation. The selected computation setup corresponds to an outdoor supercavitating experiment. Only very limited experimental data was recorded due to the difficulties under the circumstance of high-speed underwater condition. However, the numerical simulation recovers the whole scenario, the results are qualitatively reasonable by comparing to the experimental observations. The drag reduction capacity of supercavitation is evaluated by comparing with a moving vehicle launching at the same speed but without supercavitation. The results show that the supercavitation reduces the drag of the vehicle dramatically.

  16. Do spinors give rise to a frame-dragging effect?

    Randono, Andrew

    2010-01-01

    We investigate the effect of the intrinsic spin of a fundamental spinor field on the surrounding spacetime geometry. We show that despite the lack of a rotating stress-energy source (and despite claims to the contrary) the intrinsic spin of a spin-half fermion gives rise to a frame-dragging effect analogous to that of orbital angular momentum, even in Einstein-Hilbert gravity where torsion is constrained to be zero. This resolves a paradox regarding the counter-force needed to restore Newton's third law in the well-known spin-orbit interaction. In addition, the frame-dragging effect gives rise to a long-range gravitationally mediated spin-spin dipole interaction coupling the internal spins of two sources. We argue that despite the weakness of the interaction, the spin-spin interaction will dominate over the ordinary inverse square Newtonian interaction in any process of sufficiently high energy for quantum field theoretical effects to be non-negligible.

  17. Gliding flight: drag and torque of a hawk and a falcon with straight and turned heads, and a lower value for the parasite drag coefficient.

    Tucker, V A

    2000-12-01

    Raptors - falcons, hawks and eagles in this study - such as peregrine falcons (Falco peregrinus) that attack distant prey from high-speed dives face a paradox. Anatomical and behavioral measurements show that raptors of many species must turn their heads approximately 40 degrees to one side to see the prey straight ahead with maximum visual acuity, yet turning the head would presumably slow their diving speed by increasing aerodynamic drag. This paper investigates the aerodynamic drag part of this paradox by measuring the drag and torque on wingless model bodies of a peregrine falcon and a red-tailed hawk (Buteo jamaicensis) with straight and turned heads in a wind tunnel at a speed of 11.7 m s(-)(1). With a turned head, drag increased more than 50 %, and torque developed that tended to yaw the model towards the direction in which the head pointed. Mathematical models for the drag required to prevent yawing showed that the total drag could plausibly more than double with head-turning. Thus, the presumption about increased drag in the paradox is correct. The relationships between drag, head angle and torque developed here are prerequisites to the explanation of how a raptor could avoid the paradox by holding its head straight and flying along a spiral path that keeps its line of sight for maximum acuity pointed sideways at the prey. Although the spiral path to the prey is longer than the straight path, the raptor's higher speed can theoretically compensate for the difference in distances; and wild peregrines do indeed approach prey by flying along curved paths that resemble spirals. In addition to providing data that explain the paradox, this paper reports the lowest drag coefficients yet measured for raptor bodies (0.11 for the peregrine and 0.12 for the red-tailed hawk) when the body models with straight heads were set to pitch and yaw angles for minimum drag. These values are markedly lower than value of the parasite drag coefficient (C(D,par)) of 0.18 previously

  18. Recurrent and Transient Spinal Pain Among Commercial Helicopter Pilots.

    Andersen, Knut; Baardsen, Roald; Dalen, Ingvild; Larsen, Jan Petter

    2015-11-01

    The aim of this study was to provide information on the occurrence of spinal pain, i.e., low back and neck pain, among commercial helicopter pilots, along with possible associations between pain and anthropometric and demographic factors and flying exposure. Data were collected through a subjective and retrospective survey among all the 313 (294 men, 19 women) full-time pilots employed by two helicopter companies. A questionnaire was used to assess the extent of spinal complaints in a transient and recurrent pain pattern along with information on physical activities, occupational flying experience, and airframes. The survey had 207 responders (194 men, 13 women). The pilots had extensive flying experience. Spinal pain was reported by 67%. Flying-related transient pain was reported among 50%, whereas recurrent spinal pain, not necessarily associated with flying, was reported by 52%. Women experienced more pain, but sample size prevented further conclusions. Male pilots reporting any spinal pain flew significantly more hours last year (median 500 h, IQR 400-650) versus men with no pain (median 445 h, IQR 300-550). Male pilots with transient or recurrent spinal pain did not differ from nonaffected male colleagues in the measured parameters. Spinal pain is a frequent problem among male and female commercial helicopter pilots. For men, no significant associations were revealed for transient or recurrent spinal pain with age, flying experience in years, total hours, annual flying time, type of aircraft, or anthropometric factors except for any spinal pain related to hours flown in the last year.

  19. Simulation Analysis of Helicopter Ground Resonance Nonlinear Dynamics

    Zhu, Yan; Lu, Yu-hui; Ling, Ai-min

    2017-07-01

    In order to accurately predict the dynamic instability of helicopter ground resonance, a modeling and simulation method of helicopter ground resonance considering nonlinear dynamic characteristics of components (rotor lead-lag damper, landing gear wheel and absorber) is presented. The numerical integral method is used to calculate the transient responses of the body and rotor, simulating some disturbance. To obtain quantitative instabilities, Fast Fourier Transform (FFT) is conducted to estimate the modal frequencies, and the mobile rectangular window method is employed in the predictions of the modal damping in terms of the response time history. Simulation results show that ground resonance simulation test can exactly lead up the blade lead-lag regressing mode frequency, and the modal damping obtained according to attenuation curves are close to the test results. The simulation test results are in accordance with the actual accident situation, and prove the correctness of the simulation method. This analysis method used for ground resonance simulation test can give out the results according with real helicopter engineering tests.

  20. The Effects of Modafinil on Aviator Performance During 40 Hours of Continuous Wakefulness: A UH-60 Helicopter Simulator Study

    Caidwell, John

    1999-01-01

    ...) activation in helicopter pilots who had been deprived of sleep. Six Army helicopter pilots were each exposed to two 40-hour periods of continuous wakefulness separated by one night of recovery sleep...