Science.gov

Sample records for active damper wind

  1. Smart Novel Semi-Active Tuned Mass Damper for Fixed-Bottom and Floating Offshore Wind (Presentation)

    SciTech Connect

    Rodriguez Tsouroukdissian, Arturo

    2016-05-02

    The intention of this paper is to present the results of a novel smart semi-active tuned mass damper (SA-TMD), which mitigates unwanted loads for both fixed-bottom and floating offshore wind systems. (Presentation Format).

  2. Active Vibration Dampers For Rotating Machinery

    NASA Technical Reports Server (NTRS)

    Kascack, Albert F.; Ropchock, John J.; Lakatos, Tomas F.; Montague, Gerald T.; Palazzolo, Alan; Lin, Reng Rong

    1994-01-01

    Active dampers developed to suppress vibrations in rotating machinery. Essentially feedback control systems and reciprocating piezoelectric actuators. Similar active damper containing different actuators described in LEW-14488. Concept also applicable to suppression of vibrations in stationary structures subject to winds and earthquakes. Active damper offers adjustable suppression of vibrations. Small and lightweight and responds faster to transients.

  3. Space Shuttle Damper System for Ground Wind Load Tests

    NASA Technical Reports Server (NTRS)

    Robinson, G. D.; Holt, J. R.; Chang, C. S.

    1973-01-01

    An active damper system which was originally developed for a 5.5% Saturn IB/Skylab Ground Winds Model was modified and used for similar purposes in a Space Shuttle model. A second damper system which was originally used in a 3% Saturn V/Dry Workshop model was also modified and made compatible with the Space Shuttle model to serve as a back-up system. Included in this final report are descriptions of the modified damper systems and the associated control and instrumentation.

  4. Cable connected active tuned mass dampers for control of in-plane vibrations of wind turbine blades

    NASA Astrophysics Data System (ADS)

    Fitzgerald, B.; Basu, B.

    2014-11-01

    In-plane vibrations of wind turbine blades are of concern in modern multi-megawatt wind turbines. Today's turbines with capacities of up to 7.5 MW have very large, flexible blades. As blades have grown longer the increasing flexibility has led to vibration problems. Vibration of blades can reduce the power produced by the turbine and decrease the fatigue life of the turbine. In this paper a new active control strategy is designed and implemented to control the in-plane vibration of large wind turbine blades which in general is not aerodynamically damped. A cable connected active tuned mass damper (CCATMD) system is proposed for the mitigation of in-plane blade vibration. An Euler-Lagrangian wind turbine model based on energy formulation has been developed for this purpose which considers the structural dynamics of the system and the interaction between in-plane and out-of-plane vibrations and also the interaction between the blades and the tower including the CCATMDs. The CCATMDs are located inside the blades and are controlled by an LQR controller. The turbine is subject to turbulent aerodynamic loading simulated using a modification to the classic Blade Element Momentum (BEM) theory with turbulence generated from rotationally sampled spectra. The turbine is also subject to gravity loading. The effect of centrifugal stiffening of the rotating blades has also been considered. Results show that the use of the proposed new active control scheme significantly reduces the in-plane vibration of large, flexible wind turbine blades.

  5. Smart Novel Semi-Active Tuned Mass Damper for Fixed-Bottom and Floating Offshore Wind (Paper)

    SciTech Connect

    Rodriguez Tsouroukdissian, Arturo; Lackner, Mathew; Cross-Whiter, John; Park, Se Myung; Pourazarm, Pariya; La Cava, William; Lee, Sungho

    2016-05-02

    The intention of this paper is to present the results of a novel smart semi-active tuned mass damper (SA-TMD), which mitigates unwanted loads for both fixed-bottom and floating offshore wind systems. The paper will focus on the most challenging water depths for both fixed-bottom and floating systems. A close to 38m Monopile and 55m Tension Leg Platform (TLP) will be considered. A technical development and trade-off analysis will be presented comparing the new system with existing passive non-linear TMD (N-TMD) technology and semi-active. TheSATMD works passively and activates itself with low power source under unwanted dynamic loading in less than 60msec. It is composed of both variable stiffness and damping elements coupled to a central pendulum mass. The analysis has been done numerically in both FAST(NREL) and Orcaflex (Orcina), and integrated in the Wind Turbine system employing CAD/CAE. The results of this work will pave the way for experimental testing to complete the technology qualification process. The load reductions under extreme and fatigue cases reach up significant levels at tower base, consequently reducing LCOE for fixed-bottom to floating wind solutions. The nacelle acceleration is reduced substantially under severe random wind and sea states, reducing the risks of failure of electromechanical components and blades at the rotor nacelle assembly. The SA-TMD system isa new technology that has not been applied previously in wind solutions. Structural damping devices aim to increase offshore wind turbine system robustness and reliability, which eases multiple substructures installations and global stability.

  6. Viscoelastic damper overview for seismic and wind applications

    NASA Astrophysics Data System (ADS)

    Nielsen, Edmond J.; Lai, Ming-Lai; Soong, T. T.; Kelly, James M.

    1996-05-01

    Viscoelastic dampers to reduce building structural vibration were first utilized in the Twin World Trade Center Towers in New York in 1969 for wind induced vibrations. In the 1980s, the Columbia SeaFirst and Two Union Square Buildings in Seattle utilized dampers for wind. In 1994 the Chien-Tan railroad station roof in Taipei, Taiwan utilized viscoelastic dampers to reduce wind induced vibrations. Recent seismic studies at several universities have demonstrated the benefits of viscoelastic dampers for steel and concrete structures. A 13 story steel moment frame building in Santa Clara County was retrofitted with viscoelastic dampers in 1994 to reduce seismic vibrations. A non-ductile concrete building in San Diego will be retrofitted with viscoelastic dampers in 1996. The results of university testing and building application installations are reviewed in this paper.

  7. Experimental studies on semi active suspension systems with various dampers

    NASA Astrophysics Data System (ADS)

    Kumar, B. Anil; Bharath Raj, Ch; Rajendar, K.

    2015-12-01

    Some results of an experimental probe on semi Active suspension systems with various Dampers have been studied in the present paper. Dampers with different configurations were studied by using Magneto Rheological gel Damper. A comparison have been done for different configurations of Dampers viz.MR gel Damper with Magnetic field, MR gel Damper without magnetic field, Damper with conventional oil, Natural vibration without damper.

  8. Slot ripples in the damper windings of a salient-pole synchronous generator

    SciTech Connect

    Matsuki, U.; Okada, T. . Dept. of Electrical Engineering); Katagi, T. . Dept. of Marine Engineering)

    1994-03-01

    The understanding of the performances and characteristics of damper windings has become increasingly important as the importance of power system stability has increased these days. However, the characteristics of damper windings and their effects on machine dynamics in the electric power system have yet to be sufficiently clarified. This paper summarizes the results of an experimental and analytical investigation of the slot ripples in the damper windings of a salient-pole synchronous machine under steady state operation. A new method of measuring damper winding currents and voltages directly has been established and used to examine the ripples owing to the stator slot openings, which appear in the damper bar currents and voltages, air gap flux density distributions and terminal voltages. By examining the physical relationship between air gap fluxes and damper winding currents and voltages both at no load and on load, slot ripples phenomena have been made clearer than before.

  9. Active Inertial Vibration Isolators And Dampers

    NASA Technical Reports Server (NTRS)

    Laughlin, Darren; Blackburn, John; Smith, Dennis

    1994-01-01

    Report describes development of active inertial vibration isolators and dampers in which actuators electromagnet coils moving linearly within permanent magnetic fields in housings, somewhat as though massive, low-frequency voice coils in loudspeakers. Discusses principle of operation, electrical and mechanical considerations in design of actuators, characteristics of accelerometers, and frequency responses of control systems. Describes design and performance of one- and three-degree-of-freedom vibration-suppressing system based on concept.

  10. Single-Point Attachment Wind Damper for Launch Vehicle On-Pad Motion

    NASA Technical Reports Server (NTRS)

    Hrinda, Glenn A.

    2009-01-01

    A single-point-attachment wind-damper device is proposed to reduce on-pad motion of a cylindrical launch vehicle. The device is uniquely designed to attach at only one location along the vehicle and capable of damping out wind gusts from any lateral direction. The only source of damping is from two viscous dampers in the device. The effectiveness of the damper design in reducing vehicle displacements is determined from transient analysis results using an Ares I-X launch vehicle. Combinations of different spring stiffnesses and damping are used to show how the vehicle's displacement response is significantly reduced during a wind gust.

  11. Semi-active tuned mass dampers with phase control

    NASA Astrophysics Data System (ADS)

    Chung, Lap-Loi; Lai, Yong-An; Walter Yang, Chuang-Sheng; Lien, Kuan-Hua; Wu, Lai-Yun

    2013-07-01

    The present study aims at proposing an innovative phase control methodology for semi-active tuned mass dampers (SA-TMDs) that intend to minimize the off-tuned problems associated with passive tuned mass dampers (P-TMDs). The phase control algorithm is first developed, the essential of which is to apply the variable friction force to slow down the mass block at specific moments when the phase lag of the SA-TMD with respect to the structure is different from 90°, resulting in the SA-TMD back to the desired phase lag, i.e., -90° phase deviation, so that the SA-TMD has the maximum power flow to reduce the structural vibration. The feasibility of the application of the phase control in SA-TMDs is verified by performing numerical analyses of a simplified Taipei 101 structure model with a SA-TMD subjected to sinusoidal loads and design level wind loads. The numerical simulation results show that the SA-TMD implemented with phase control can enable the mass block to vibrate in a manner with a phase lag close to the -90° when the structure model is under sinusoidal excitations with frequencies different from the structural fundamental mode. The SA-TMD with phase control not only exhibits better performance than the optimal P-TMD in terms of suppressing the structural vibration, but also enhances its robustness, particularly when the SA-TMD is off-tuned to the structure.

  12. Optimization of Semi-active Seat Suspension with Magnetorheological Damper

    NASA Astrophysics Data System (ADS)

    Segla, Stefan; Kajaste, J.; Keski-Honkola, P.

    The paper deals with modeling, control and optimization of semiactive seat suspension with pneumatic spring and magnetorheological damper. The main focus is on isolating vertical excitation from the cabin of a bucket-wheel excavator in order to protect the excavator driver against harmful vibration. Three different control algorithms are used to determine the desired semi-active damping force: skyhook control, balance control and combination of balance and skyhook controls. The dynamic behavior of the semi-active system is optimized using genetic algorithms. As the objective function the effective value of the seat (sprung mass) acceleration is used.

  13. An enhanced nonlinear damping approach accounting for system constraints in active mass dampers

    NASA Astrophysics Data System (ADS)

    Venanzi, Ilaria; Ierimonti, Laura; Ubertini, Filippo

    2015-11-01

    Active mass dampers are a viable solution for mitigating wind-induced vibrations in high-rise buildings and improve occupants' comfort. Such devices suffer particularly when they reach force saturation of the actuators and maximum extension of their stroke, which may occur in case of severe loading conditions (e.g. wind gust and earthquake). Exceeding actuators' physical limits can impair the control performance of the system or even lead to devices damage, with consequent need for repair or substitution of part of the control system. Controllers for active mass dampers should account for their technological limits. Prior work of the authors was devoted to stroke issues and led to the definition of a nonlinear damping approach, very easy to implement in practice. It consisted of a modified skyhook algorithm complemented with a nonlinear braking force to reverse the direction of the mass before reaching the stroke limit. This paper presents an enhanced version of this approach, also accounting for force saturation of the actuator and keeping the simplicity of implementation. This is achieved by modulating the control force by a nonlinear smooth function depending on the ratio between actuator's force and saturation limit. Results of a numerical investigation show that the proposed approach provides similar results to the method of the State Dependent Riccati Equation, a well-established technique for designing optimal controllers for constrained systems, yet very difficult to apply in practice.

  14. Contribution of tuned liquid column gas dampers to the performance of offshore wind turbines under wind, wave, and seismic excitations

    NASA Astrophysics Data System (ADS)

    Bargi, Khosrow; Dezvareh, Reza; Mousavi, Seyed Amin

    2016-09-01

    The main intention of the present study is to reduce wind, wave, and seismic induced vibrations of jackettype offshore wind turbines (JOWTs) through a newly developed vibration absorber, called tuned liquid column gas damper (TLCGD). Using a Simulink-based model, an analytical model is developed to simulate global behavior of JOWTs under different dynamic excitations. The study is followed by a parametric study to explore efficiency of the TLCGD in terms of nacelle acceleration reduction under wind, wave, and earthquake loads. Study results indicate that optimum frequency of the TLCGD is rather insensitive to excitation type. In addition, while the gain in vibration control from TLCGDs with higher mass ratios is generally more pronounced, heavy TLCGDs are more sensitive to their tuned frequency such that ill-regulated TLCGD with high mass ratio can lead to destructive results. It is revealed that a well regulated TLCGD has noticeable contribution to the dynamic response of the JOWT under any excitation.

  15. An investigation on a semi-active magnetorheological tuned liquid column damper (MR-TLCD)

    NASA Astrophysics Data System (ADS)

    Sun, H. X.; Wang, X. Y.

    2016-04-01

    this paper, a novel semi-active magnetorheological tuned liquid column damper (MR-TLCD) device combining tuned liquid column damper (TLCD) and magnetorheological damper (MRD) is devised for wind or earthquake vibration control of civil structures. In this device, a traditional moving head loss in the TLCD is replaced with a controlled MRD in the bottom or one side of the vertical column, which can easily and rapidly adjust the damping of the device. A semi-active experimental prototype MR-TLCD consisting of a shear rotary MRD and a TLCD is built. Based on the four basic presumptions, a dynamic model of the devised MR-TLCD is established using the Lagrange equation. In this equation, the formula of MRD employs the Bingham Boltzmann model. The natural frequency of the MR-TLCD is determined by the total central length and spring stiffness. It is worth noting that the natural frequency differs with the simple TLCD, because the device adds a joint spring. An equivalent linear damping expression is developed under harmonic excitation, and its mechanical model is developed using the equivalent period displacement and the coulomb friction force of MRD. At the same time, the equivalent damping can be adjusted by the real-time applied current, which can achieve the semi-active control performance. To validate the proposed frequency and damping model, Experimental test is conducted on a section area 150mm × 150mm and a total length 2.24m of the MR-TLCD dimensions. Comparisons are made between predicted and measured TLCD liquid surface displacement motion. The result shows the error of its nature frequency is only 2.29%.

  16. Vibration Control by a Shear Type Semi-active Damper Using Magnetorheological Grease

    NASA Astrophysics Data System (ADS)

    Shiraishi, Toshihiko; Misaki, Hirotaka

    2016-09-01

    This paper describes semi-active vibration control by a controllable damper with high reliability and wide dynamic range using magnetorheological (MR) grease. Some types of cylindrical controllable dampers based on pressure difference between chambers in the dampers using “MR fluid”, whose rheological properties can be varied by applying a magnetic field, have been reported as a semi-active device. However, there are some challenging issues of them. One is to improve dispersion stability. The particles dispersed in MR fluid would make sedimentation after a period. Another is to expand dynamic range. Since cylindrical dampers require sealing elements because of pressure difference in the dampers, the dynamic range between the maximum and minimum damping force according to a magnetic field is reduced. In this study, a controllable damper using the MR effect was proposed and its performance was experimentally verified to improve the dispersion stability by using “MR grease”, which includes grease as the carrier of magnetic particles, and to expand the dynamic range by adopting a shear type structure not requiring sealing elements. Furthermore, semiactive vibration control experiments by the MR grease damper using a simple algorithm based on the skyhook damper scheme were conducted and its performance was investigated.

  17. Digital active material processing platform effort (DAMPER), SBIR phase 2

    NASA Technical Reports Server (NTRS)

    Blackburn, John; Smith, Dennis

    1992-01-01

    Applied Technology Associates, Inc., (ATA) has demonstrated that inertial actuation can be employed effectively in digital, active vibration isolation systems. Inertial actuation involves the use of momentum exchange to produce corrective forces which act directly on the payload being actively isolated. In a typical active vibration isolation system, accelerometers are used to measure the inertial motion of the payload. The signals from the accelerometers are then used to calculate the corrective forces required to counteract, or 'cancel out' the payload motion. Active vibration isolation is common technology, but the use of inertial actuation in such systems is novel, and is the focus of the DAMPER project. A May 1991 report was completed which documented the successful demonstration of inertial actuation, employed in the control of vibration in a single axis. In the 1 degree-of-freedom (1DOF) experiment a set of air bearing rails was used to suspend the payload, simulating a microgravity environment in a single horizontal axis. Digital Signal Processor (DSP) technology was used to calculate in real time, the control law between the accelerometer signals and the inertial actuators. The data obtained from this experiment verified that as much as 20 dB of rejection could be realized by this type of system. A discussion is included of recent tests performed in which vibrations were actively controlled in three axes simultaneously. In the three degree-of-freedom (3DOF) system, the air bearings were designed in such a way that the payload is free to rotate about the azimuth axis, as well as translate in the two horizontal directions. The actuator developed for the DAMPER project has applications beyond payload isolation, including structural damping and source vibration isolation. This report includes a brief discussion of these applications, as well as a commercialization plan for the actuator.

  18. Optimal semi-active vibration absorber for harmonic excitation based on controlled semi-active damper

    NASA Astrophysics Data System (ADS)

    Weber, F.

    2014-09-01

    The semi-active vibration absorber (SVA) based on controlled semi-active damper is formulated to realize the behaviour of the passive undamped vibration absorber tuned to the actual harmonic disturbing frequency. It is shown that the controlled stiffness force, which is emulated by the semi-active damper to realize the precise real-time frequency tuning of the SVA, is unpreventably combined with the generation of undesirable damping in the semi-active damper whereby the SVA does not behave as targeted. The semi-active stiffness force is therefore optimized for minimum primary structure response. The results point out that the optimal semi-active stiffness force reduces the undesirable energy dissipation in the SVA at the expenses of slight imprecise frequency tuning. Based on these findings, a real-time applicable suboptimal SVA is formulated that also takes the relative motion constraint of real mass dampers into account. The results demonstrate that the performance of the suboptimal SVA is closer to that of the active solution than that of the passive mass damper.

  19. Dynamic response mitigation of floating wind turbine platforms using tuned liquid column dampers.

    PubMed

    Jaksic, V; Wright, C S; Murphy, J; Afeef, C; Ali, S F; Mandic, D P; Pakrashi, V

    2015-02-28

    In this paper, we experimentally study and compare the effects of three combinations of multiple tuned liquid column dampers (MTLCDs) on the dynamic performance of a model floating tension-leg platform (TLP) structure in a wave basin. The structural stability and safety of the floating structure during operation and maintenance is of concern for the performance of a renewable energy device that it might be supporting. The dynamic responses of the structure should thus be limited for these renewable energy devices to perform as intended. This issue is particularly important during the operation of a TLP in extreme weather conditions. Tuned liquid column dampers (TLCDs) can use the power of sloshing water to reduce surge motions of a floating TLP exposed to wind and waves. This paper demonstrates the potential of MTLCDs in reducing dynamic responses of a scaled TLP model through an experimental study. The potential of using output-only statistical markers for monitoring changes in structural conditions is also investigated through the application of a delay vector variance (DVV) marker for different conditions of control for the experiments.

  20. Aeromechanical stability augmentation using semi-active friction-based lead-lag damper

    NASA Astrophysics Data System (ADS)

    Agarwal, Sandeep

    2005-11-01

    Lead-lag dampers are present in most rotors to provide the required level of damping in all flight conditions. These dampers are a critical component of the rotor system, but they also represent a major source of maintenance cost. In present rotor systems, both hydraulic and elastomeric lead-lag dampers have been used. Hydraulic dampers are complex mechanical components that require hydraulic fluids and have high associated maintenance costs. Elastomeric dampers are conceptually simpler and provide a "dry" rotor, but are rather costly. Furthermore, their damping characteristics can degrade with time without showing external signs of failure. Hence, the dampers must be replaced on a regular basis. A semi-active friction based lead-lag damper is proposed as a replacement for hydraulic and elastomeric dampers. Damping is provided by optimized energy dissipation due to frictional forces in semi-active joints. An actuator in the joint modulates the normal force that controls energy dissipation at the frictional interfaces, resulting in large hysteretic loops. Various selective damping strategies are developed and tested for a simple system containing two different frequency modes in its response, one of which needs to be damped out. The system reflects the situation encountered in rotor response where 1P excitation is present along with the potentially unstable regressive lag motion. Simulation of the system response is obtained to compare their effectiveness. Next, a control law governing the actuation in the lag damper is designed to generate the desired level of damping for performing adaptive selective damping of individual blade lag motion. Further, conceptual design of a piezoelectric friction based lag damper for a full-scale rotor is presented and various factors affecting size, design and maintenance cost, damping capacity, and power requirements of the damper are discussed. The selective semi-active damping strategy is then studied in the context of classical

  1. Real-time hybrid simulation technique for performance evaluation of full-scale sloshing dampers in wind turbines

    NASA Astrophysics Data System (ADS)

    Zhang, Zili; Basu, Biswajit; Nielsen, Saren R. K.

    2016-09-01

    As a variation of the pseudodynamic testing technique, the real-time hybrid simulation (RTHS) technique is executed in real time, thus allowing investigation of structural systems with rate-dependent components. In this paper, the RTHS is employed for performance evaluation of full-scale liquid sloshing dampers in multi-megawatt wind turbines, where the tuned liquid damper (TLD) is manufactured and tested as the physical substructure while the wind turbine is treated as the numerical substructure and modelled in the computer using a 13-degree-of-freedom (13-DOF) aeroelastic model. Wind turbines with 2 MW and 3 MW capacities have been considered under various turbulent wind conditions. Extensive parametric studies have been performed on the TLD, e.g., various tuning ratios by changing the water level, TLD without and with damping screens (various mesh sizes of the screen considered), and TLD with flat and sloped bottoms. The present study provides useful guidelines for employing sloshing dampers in large wind turbines, and indicates huge potentials of applying RTHS technique in the area of wind energy.

  2. Modeling of Semi-Active Vehicle Suspension with Magnetorhological Damper

    NASA Astrophysics Data System (ADS)

    Hasa, Richard; Danko, Ján; Milesich, Tomáš; Magdolen, Ľuboš

    2014-12-01

    Modeling of suspension is a current topic. Vehicle users require both greater driving comfort and safety. There is a space to invent new technologies like magnetorheological dampers and their control systems to increase these conflicting requirements. Magnetorheological dampers are reliably mathematically described by parametric and nonparametric models. Therefore they are able to reliably simulate the driving mode of the vehicle. These simulations are important for automotive engineers to increase vehicle safety and passenger comfort.

  3. Parameter Identification of Long Stroke and Short Stroke MR Damper for its Use in Semi-Active Vibration Control

    NASA Astrophysics Data System (ADS)

    Bharathi Priya, C.; Gopalakrishnan, N.

    2016-12-01

    Magnetorheological (MR) dampers are devices that can be used for structural vibration reduction under seismic excitation. These devices are used in semi-active control which require less power compared to active devices and offer high reliability compared to passive devices. Despite the advantages of MR damper, use of these dampers in an effective way in a structure is highly challenging and a precise modelling is required as these dampers are highly non-linear. Among the parametric models available, Bouc-Wen model is widely used because of its effective modelling of the hysteretic force-velocity curve of MR damper. The parameters of Bouc-Wen model are damper dependent and hence need to be identified before utilising the damper for further simulation studies. In this work, the parametric identification of Bouc-Wen model for commercially available long stroke and short stroke MR damper (RD 8040-1 and RD 8041-1) is done. For this, experimental characterization of the dampers are carried out using hydraulic actuators mounted on a self-restraining frame. The damper is driven harmonically in the testing setup at various combinations of frequency, amplitude, current and displacement. Using the experimental characterization, parameters of Bouc-Wen model are identified by Levenberg-Marquardt optimization Algorithm (LMA). The identified parameters are validated by comparing with the experimental results. The identified parameters are believed to be worthwhile for the use of these MR dampers in further studies of real-time semi-active vibration control of structures.

  4. Vibration Reduction of Wind Turbines Using Tuned Liquid Column Damper Using Stochastic Analysis

    NASA Astrophysics Data System (ADS)

    Alkmim, M. H.; de Morais, M. V. G.; Fabro, A. T.

    2016-09-01

    Passive energy dissipation systems encompass a range of materials and devices for enhancing damping. They can be used both for natural hazard mitigation and for rehabilitation of aging or deficient structures. Among the current passive energy dissipation systems, tuned liquid column damper (TLCD), a class of passive control that utilizes liquid in a “U” shape reservoir to control structural vibration of the primary system, has been widely researched in a variety of applications. This paper focus in TLCD application for wind turbines presenting the mathematical model as well as the methods used to overcome the nonlinearity embedded in the system. Optimization methods are used to determine optimum parameters of the system. Additionally, a comparative analysis is done considering the equivalent linearized system and the nonlinear system under random excitation with the goal of compare the nonlinear model with the linear equivalent and investigated the effectiveness of the TLCD. The results are shown using two types of random excitation, a white noise and a first order filters spectrum, the latter presents more satisfactory results since the excitation spectrum is physically more realistic than white noise spectrum model. The results indicate that TLCDs at optimal tuning can significantly dissipate energy of the primary structure between 3 to 11%.

  5. A semi-active control suspension system for railway vehicles with magnetorheological fluid dampers

    NASA Astrophysics Data System (ADS)

    Wei, Xiukun; Zhu, Ming; Jia, Limin

    2016-07-01

    The high-speed train has achieved great progress in the last decades. It is one of the most important modes of transportation between cities. With the rapid development of the high-speed train, its safety issue is paid much more attention than ever before. To improve the stability of the vehicle with high speed, extra dampers (i.e. anti-hunting damper) are used in the traditional bogies with passive suspension system. However, the curving performance of the vehicle is undermined due to the extra lateral force generated by the dampers. The active suspension systems proposed in the last decades attempt to solve the vehicle steering issue. However, the active suspension systems need extra actuators driven by electrical power or hydraulic power. There are some implementation and even safety issues which are not easy to be overcome. In this paper, an innovative semi-active controlled lateral suspension system for railway vehicles is proposed. Four magnetorheological fluid dampers are fixed to the primary suspension system of each bogie. They are controlled by online controllers for enhancing the running stability on the straight track line on the one hand and further improving the curving performance by controlling the damper force on the other hand. Two control strategies are proposed in the light of the pure rolling concept. The effectiveness of the proposed strategies is demonstrated by SIMPACK and Matlab co-simulation for a full railway vehicle with two conventional bogies.

  6. Semi-active friction damper for buildings subject to seismic excitation

    NASA Astrophysics Data System (ADS)

    Mantilla, Juan S.; Solarte, Alexander; Gomez, Daniel; Marulanda, Johannio; Thomson, Peter

    2016-04-01

    Structural control systems are considered an effective alternative for reducing vibrations in civil structures and are classified according to their energy supply requirement: passive, semi-active, active and hybrid. Commonly used structural control systems in buildings are passive friction dampers, which add energy dissipation through damping mechanisms induced by sliding friction between their surfaces. Semi-Active Variable Friction Dampers (SAVFD) allow the optimum efficiency range of friction dampers to be enhanced by controlling the clamping force in real time. This paper describes the development and performance evaluation of a low-cost SAVFD for the reduction of vibrations of structures subject to earthquakes. The SAVFD and a benchmark structural control test structure were experimentally characterized and analytical models were developed and updated based on the dynamic characterization. Decentralized control algorithms were implemented and tested on a shaking table. Relative displacements and accelerations of the structure controlled with the SAVFD were 80% less than those of the uncontrolled structure

  7. Semi-active tuned liquid column damper implementation with real-time hybrid simulations

    NASA Astrophysics Data System (ADS)

    Riascos, Carlos; Marulanda Casas, Johannio; Thomson, Peter

    2016-04-01

    Real-time hybrid simulation (RTHS) is a modern cyber-physical technique used for the experimental evaluation of complex systems, that treats the system components with predictable behavior as a numerical substructure and the components that are difficult to model as an experimental substructure. Therefore it is an attractive method for evaluation of the response of civil structures under earthquake, wind and anthropic loads. In this paper, the response of three-story shear frame controlled by a tuned liquid column damper (TLCD) and subject to base excitation is considered. Both passive and semi-active control strategies were implemented and are compared. While the passive TLCD achieved a reduction of 50% in the acceleration response of the main structure in comparison with the structure without control, the semi-active TLCD achieved a reduction of 70%, and was robust to variations in the dynamic properties of the main structure. In addition, a RTHS was implemented with the main structure modeled as a linear, time-invariant (LTI) system through a state space representation and the TLCD, with both control strategies, was evaluated on a shake table that reproduced the displacement of the virtual structure. Current assessment measures for RTHS were used to quantify the performance with parameters such as generalized amplitude, equivalent time delay between the target and measured displacement of the shake table, and energy error using the measured force, and prove that the RTHS described in this paper is an accurate method for the experimental evaluation of structural control systems.

  8. Experimental Comparison of Dynamic Responses of a Tension Moored Floating Wind Turbine Platform with and without Spring Dampers

    NASA Astrophysics Data System (ADS)

    Wright, C.; O'Sullivan, K.; Murphy, J.; Pakrashi, V.

    2015-07-01

    The offshore wind industry is rapidly maturing and is now expanding to more extreme environments in deeper water and farther from shore. To date fixed foundation types (i.e. monopoles, jackets) have been primarily used but become uneconomical in water depths greater than 50m. Floating foundations have more complex dynamics but at the moment no design has reached commercialization, although a number of devices are being tested at prototype stage. The development of concepts is carried out through physical model testing of scaled devices such that to better understand the dynamics of the system and validate numerical models. This paper investigates the testing of a scale model of a tension moored wind turbine at two different scales and in the presence and absence of a spring damper controlling its dynamic response. The models were tested under combined wave and wind thrust loading conditions. The analysis compares the motions of the platform at different scales and structural conditions through RAO, testing a mooring spring damper for load reductions.

  9. Maximizing semi-active vibration isolation utilizing a magnetorheological damper with an inner bypass configuration

    SciTech Connect

    Bai, Xian-Xu; Wereley, Norman M.; Hu, Wei

    2015-05-07

    A single-degree-of-freedom (SDOF) semi-active vibration control system based on a magnetorheological (MR) damper with an inner bypass is investigated in this paper. The MR damper employing a pair of concentric tubes, between which the key structure, i.e., the inner bypass, is formed and MR fluids are energized, is designed to provide large dynamic range (i.e., ratio of field-on damping force to field-off damping force) and damping force range. The damping force performance of the MR damper is modeled using phenomenological model and verified by the experimental tests. In order to assess its feasibility and capability in vibration control systems, the mathematical model of a SDOF semi-active vibration control system based on the MR damper and skyhook control strategy is established. Using an MTS 244 hydraulic vibration exciter system and a dSPACE DS1103 real-time simulation system, experimental study for the SDOF semi-active vibration control system is also conducted. Simulation results are compared to experimental measurements.

  10. Development of passive-controlled HUB (teetered brake & damper mechanism) of horizontal axis wind turbine

    SciTech Connect

    Shimizu, Yukimaru; Kamada, Yasunari; Maeda, Takao

    1997-12-31

    For the purpose of the improvement of reliability of the Mega-Watt wind turbine, this paper indicates the development of an original mechanism for the passive-controlled hub, which has the effects of braking and damping on aerodynamic forces. This mechanism is useful for variable speed control of the large wind turbine. The passive-controlled hub is the combination of two mechanisms. One is the passive-teetered and damping mechanism, and the other is the passive-variable-pitch mechanism. These mechanism are carried out by the combination of the teetering and feathering motions. When the wind speed exceeds the rated wind speed, the blade is passively teetered in a downwind direction and, simultaneously, a feathering mechanism, which is linked to the teetering mechanism through a connecting rods, is activated. Testing of the model horizontal axis wind turbine in a wind tunnel showed that the passive-controlled hub mechanism can suppress the over-rotational speed of the rotor. By the application of the passive-controlled hub mechanism, the maximum rotor speed is reduced to about 60%.

  11. ANFIS optimized semi-active fuzzy logic controller for magnetorheological dampers

    NASA Astrophysics Data System (ADS)

    César, Manuel Braz; Barros, Rui Carneiro

    2016-11-01

    In this paper, we report on the development of a neuro-fuzzy controller for magnetorheological dampers using an Adaptive Neuro-Fuzzy Inference System or ANFIS. Fuzzy logic based controllers are capable to deal with non-linear or uncertain systems, which make them particularly well suited for civil engineering applications. The main objective is to develop a semi-active control system with a MR damper to reduce the response of a three degrees-of-freedom (DOFs) building structure. The control system is designed using ANFIS to optimize the fuzzy inference rule of a simple fuzzy logic controller. The results show that the proposed semi-active neuro-fuzzy based controller is effective in reducing the response of structural system.

  12. State of the art review of semi active control for magnetorheological dampers

    NASA Astrophysics Data System (ADS)

    Mughal, Umair Najeeb

    2017-01-01

    Earthquakes causes severe damage to badly designed structures or buildings to fail or collapse, and also have caused some damage to well-designed structures to malfunction due to the damage or failure of the equipment housed in the structure or building. The use magnetorheological dampers to mitigate the effect of external excitation is increased to resolve this. This article is a state of the art review of nonlinear analytical models to understand the efficacy of semi-active control theory for magnetorheological dampers. A nonlinear semi active control law is desired to be designed which atleast guarantees analytical closed loop stability in order to mitigate the effect of perturbations and drive the desired output to equilibrium.

  13. Semi-active sliding mode control of vehicle suspension with magneto-rheological damper

    NASA Astrophysics Data System (ADS)

    Zhang, Hailong; Wang, Enrong; Zhang, Ning; Min, Fuhong; Subash, Rakheja; Su, Chunyi

    2015-01-01

    The vehicle semi-active suspension with magneto-rheological damper(MRD) has been a hot topic since this decade, in which the robust control synthesis considering load variation is a challenging task. In this paper, a new semi-active controller based upon the inverse model and sliding mode control (SMC) strategies is proposed for the quarter-vehicle suspension with the magneto-rheological (MR) damper, wherein an ideal skyhook suspension is employed as the control reference model and the vehicle sprung mass is considered as an uncertain parameter. According to the asymptotical stability of SMC, the dynamic errors between the plant and reference systems are used to derive the control damping force acquired by the MR quarter-vehicle suspension system. The proposed modified Bouc-wen hysteretic force-velocity ( F- v) model and its inverse model of MR damper, as well as the proposed continuous modulation (CM) filtering algorithm without phase shift are employed to convert the control damping force into the direct drive current of the MR damper. Moreover, the proposed semi-active sliding mode controller (SSMC)-based MR quarter-vehicle suspension is systematically evaluated through comparing the time and frequency domain responses of the sprung and unsprung mass displacement accelerations, suspension travel and the tire dynamic force with those of the passive quarter-vehicle suspension, under three kinds of varied amplitude harmonic, rounded pulse and real-road measured random excitations. The evaluation results illustrate that the proposed SSMC can greatly suppress the vehicle suspension vibration due to uncertainty of the load, and thus improve the ride comfort and handling safety. The study establishes a solid theoretical foundation as the universal control scheme for the adaptive semi-active control of the MR full-vehicle suspension decoupled into four MR quarter-vehicle sub-suspension systems.

  14. Nutation damper

    NASA Technical Reports Server (NTRS)

    Evans, J. (Inventor)

    1973-01-01

    A nutation damper for use on a spinning body is disclosed. The damper is positioned parallel to the spin axis of the body and radially displaced therefrom. The damper is partially filled with a fluid and contains a porous media to impede the flow of the fluid induced by nutation.

  15. Semi-active vibration absorber based on real-time controlled MR damper

    NASA Astrophysics Data System (ADS)

    Weber, F.

    2014-06-01

    A semi-active vibration absorber with real-time controlled magnetorheological damper (MR-SVA) for the mitigation of harmonic structural vibrations is presented. The MR damper force targets to realize the frequency and damping adaptations to the actual structural frequency according to the principle of the undamped vibration absorber. The relative motion constraint of the MR-SVA is taken into account by an adaptive nonlinear control of the internal damping of the MR-SVA. The MR-SVA is numerically and experimentally validated for harmonic excitation of the primary structure when the natural frequency of the passive mass spring system of the MR-SVA is correctly tuned to the targeted structural resonance frequency and when de-tuning is present. The results demonstrate that the MR-SVA outperforms the passive TMD at structural resonance frequency by at least 12.4% and up to 60.0%.

  16. Improving the vibration suppression capabilities of a magneto-rheological damper using hybrid active and semi-active control

    NASA Astrophysics Data System (ADS)

    Ullah Khan, Irfan; Wagg, David; Sims, Neil D.

    2016-08-01

    This paper presents a new hybrid active and semi-active control method for vibration suppression in flexible structures. The method uses a combination of a semi-active device and an active control actuator situated elsewhere in the structure to suppress vibrations. The key novelty is to use the hybrid controller to enable the magneto-rheological damper to achieve a performance as close to a fully active device as possible. This is achieved by ensuring that the active actuator can assist the magneto-rheological damper in the regions where energy is required. In addition, the hybrid active and semi-active controller is designed to minimize the switching of the semi-active controller. The control framework used is the immersion and invariance control technique in combination with sliding mode control. A two degree-of-freedom system with lightly damped resonances is used as an example system. Both numerical and experimental results are generated for this system, and then compared as part of a validation study. The experimental system uses hardware-in-the-loop to simulate the effect of both the degrees-of-freedom. The results show that the concept is viable both numerically and experimentally, and improved vibration suppression results can be obtained for the magneto-rheological damper that approach the performance of an active device.

  17. Experimental evaluation of magnetorheological dampers for semi-active tuned vibration absorbers

    NASA Astrophysics Data System (ADS)

    Koo, Jeong-Hoi; Ahmadian, Mehdi; Setareh, Mehdi

    2003-07-01

    The main purpose of this study is to experimentally evaluate the dynamic performance of a semi-active Tuned Vibration Absorber (TVA) with a Magneto-Rheological (MR) damper. To this end, a test apparatus was built to represent a two-degree-of-freedom primary structure model coupled with a MR TVA. The primary structure mass, which is modeled with steel plates, was excited by a hydraulic actuator through four air springs. The air springs represent the stiffness of the primary structure and offer the ability to change the stiffness. The semi-active TVA consists of a steel plate, a MR damper, and four coil springs for physical representation of the mass, the damping element, and the stiffness of the TVA, respectively. Mounted on top of the primary structure, the TVA is connected to the primary structure plates by hardened linear bearing shafts. A series of transducers along with a data acquisition system was used to collect sensory information and implement real time control of the MR TVA. Using this test rig setup, a parametric study was performed to analyze the dynamics of the semi-active TVA and to compare the performance of the semi-active TVA with a passive TVA. Displacement based on-off groundhook (on-off DBG) control was used as the control policy for the semi-active TVA. In the parametric study, the effects of on/off-state damping of the MR damper were investigated and compared with a passive TVA to analyze the relative benefits of a semi-active TVA. When damping increased in the passive TVA, the two resonant peaks merge into one peak, and the peak grows. This indicates that the primary structure and TVA are linked together, disabling the TVA, and it eventually magnifies the vibrations. For a semi-active TVA, however, the two resonant peaks decrease as on-state damping increases (keeping low off-state damping), indicating reduction of vibrations. It is shown that semi-active TVAs outperform passive TVAs in reducing the peak transmissibility, implying that semi-active

  18. Comparative study on semi-active control algorithms for piezoelectric friction dampers

    NASA Astrophysics Data System (ADS)

    Chen, Chaoqiang; Chen, Genda

    2004-07-01

    A semi-active Tri-D algorithm combining Coulomb, Reid and viscous damping mechanisms has recently been developed by the authors to drive piezoelectric friction dampers. The objective of this study is to analytically compare its performance with those of bang-bang control, clipped-optimal control, modulated homogeneous control, and a modified clipped-optimal control. Two far-field and two near-field historical earthquake records with various intensities and dominant frequencies were used in this study. All algorithms were evaluated with a ¼ scale 3-story frame structure in terms of reductions in peak inter-story drift ratio and peak floor acceleration. A piezoelectric friction damper was considered to be installed between a bracing support and the first floor of the frame structure. Both advantages and disadvantages of each control algorithm were discussed with numerical simulations. At near resonance, both bang-bang and clipped-optimal algorithms are more effective in drift reduction, and the modified clipped-optimal algorithm is more effective in acceleration reduction than both Tri-D and modulated homogeneous algorithms. But the latter requires less control force on the average. For a non-resonant case, the Tri-D and modulated homogeneous algorithms are more effective in acceleration reduction than others even with less control force required. Overall, the Tri-D and modulated homogeneous controls are effective in response reduction, adaptive, and robust to earthquake characteristics.

  19. Influence analysis of time delay to active mass damper control system using pole assignment method

    NASA Astrophysics Data System (ADS)

    Teng, J.; Xing, H. B.; Lu, W.; Li, Z. H.; Chen, C. J.

    2016-12-01

    To reduce the influence of time delay on the Active Mass Damper (AMD) control systems, influence analysis of time delay on system poles and stability is applied in the paper. A formula of the maximum time delay for ensuring system stability is established, by which the influence analysis of control gains on system stability is further arisen. In addition, the compensation controller is designed based on the given analysis results and pole assignment. A numerical example and an experiment are illustrated to verify that the performance of time-delay system. The result is consistent to that of the long-time delay control system, as well as to proof the better effectiveness of the new method proposed in this article.

  20. Design of a stand-alone active damper for distributed control of vibration

    NASA Astrophysics Data System (ADS)

    Cinquemani, S.; Cazzulani, G.; Costa, A.; Resta, F.

    2016-04-01

    The aim of active vibration control is to enhance the performance of a system (eg. comfort, fatigue life, etc.) by limiting vibrations. One of the most effective technique to reach this goal is to increase the equivalent damping of the system and then the dissipation of the kinetic energy (the so called skyhook damping technique). Application of active vibration control often require a complex setup. When large structures are considered, it is often necessary to have a high number of sensors and actuators, suitably cabled, in addition to all the devices necessary to condition and amplify the signals of measurement and control and to execute in real time the control algorithms synthesized. This work arises from the need to simplify this situation, developing a standalone device that is able of carrying out operations of vibration control in an autonomous way, thus containing in itself an actuator, the sensors needed to evaluate the vibratory state of the structure, and a micro-controller embedding different control algorithm. The design of the smart damper covers many aspects and requires a strong integration of different disciplines. A prototype has been realized and tested on a vibrating structure. The experimental results show good performance in suppress vibration.

  1. Evaluation method for a controller of active mass damper using central pattern generator

    NASA Astrophysics Data System (ADS)

    Hongu, Junichi; Iba, Daisuke; Nakamura, Morimasa; Moriwaki, Ichiro

    2013-04-01

    This paper proposes an evaluation method for a CPG controller designed for active mass dampers. Neural oscillators composing the CPG have nonlinear and entrainment properties. Therefore, the proposed controller has possibility to have flexibility, when the structural parameters, i.e. stiffness or damping, are changed by the effect of earthquakes and the like. However, there has been no study to evaluate the controller's above-mentioned properties. For tuning into practical application, the reliability and flexibility along with the controller's performance must be analyzed. In our previous study, the phase reduction theory was tried to appraise the synchronization between a structure and a single neural oscillator and the synchronization region of the neural oscillator was obtained as basic research. However, the information from the synchronization region was insufficient to evaluate the system, because the neural oscillator has a phase difference called a phase locking point between the structure and the neural oscillator during the synchronization. Then, in this paper, the phase locking point within the synchronization region between a structure and a single neural oscillator is focused on, and the phase locking point and the vibration mitigation effect are considered with the simple object model.

  2. Cyclic modulation of semi-active controllable dampers for tonal vibration isolation

    NASA Astrophysics Data System (ADS)

    Anusonti-Inthra, P.; Gandhi, F.

    2004-08-01

    The present study examines the potential of using a semi-active controllable damper, whose damping coefficient can be modulated in real time, for tonal vibration isolation applications. A frequency-domain control algorithm is developed for determining the damping coefficient variation (at twice the disturbance frequency) that minimizes the force transmitted to the support at the disturbance frequency. The effectiveness of open-loop, closed-loop, and adaptive controllers in rejecting the transmitted disturbances are evaluated. The results of the study indicate that when limits in damping coefficient variation are considered, the support force could be reduced by about an additional 30%, beyond the levels due to the passive isolation characteristics (no cyclic damping modulation). When the disturbance phase changes during operation, the effectiveness of the open-loop controller is rapidly degraded. While the closed-loop controller (with inputs based on current levels of force transmitted to the support) performed better, there was still some degradation in performance, and transmitted support forces were not reduced to levels prior to the change in disturbance phase. The results show that for the semi-active system to retain its effectiveness in rejecting disturbances, a closed-loop, adaptive controller (with on-line system identification) is required; even when there is only a change in disturbance, and no change in basic system properties. An explanation for this phenomenon, related to the bi-linear nature of the semi-active system, is provided. Cyclic modulations in the damping coefficient were more effective in reducing the transmitted forces at the disturbance frequency than simply reducing the baseline damping coefficient (to improve the passive isolation characteristics).

  3. Effects of the lower extremities muscle activation during muscular strength training on an unstable platform with magneto-rheological dampers

    NASA Astrophysics Data System (ADS)

    Piao, YongJun; Choi, YounJung; Kim, JungJa; Kwan, TaeKyu; Kim, Nam-Gyun

    2009-03-01

    Adequate postural balance depends on the spatial and temporal integration of vestibular, visual, and somatosensory information. Especially, the musculoskeletal function (range of joint, flexibility of spine, muscular strength) is essential in maintaining the postural balance. Muscular strength training methods include the use of commercialized devices and repeatable resistance training tools (rubber band, ball, etc). These training systems cost high price and can't control of intensity. Thus we suggest a new training system which can adjust training intensity and indicate the center of pressure of a subject while the training was passively controlled by applying controlled electric current to the Magneto- Rheological damper. And we performed experimental studies on the muscular activities in the lower extremities during maintaining, moving and pushing exercises on an unstable platform with Magneto rheological dampers. A subject executed the maintaining, moving and pushing exercises which were displayed in a monitor. The electromyographic signals of the eight muscles in lower extremities were recorded and analyzed in the time and frequency domain: the muscles of interest were rectus femoris, biceps femoris, tensor fasciae latae, vastus lateralis, vastus medialis, gastrocnemius, tibialis anterior, and soleus. The experimental results showed the difference of muscular activities at the four moving exercises and the nine maintaining exercises. The rate of the increase in the muscular activities was affected by the condition of the unstable platform with MR dampers for the maintaining and moving exercises. The experimental results suggested the choice of different maintaining and moving exercises could selectively train different muscles with varying intensity. Furthermore, the findings also suggested the training using this system can improve the ability of postural balance.

  4. The effect of time delay on control stability of an electromagnetic active tuned mass damper for vibration control

    NASA Astrophysics Data System (ADS)

    Hassan, A.; Torres-Perez, A.; Kaczmarczyk, S.; Picton, P.

    2016-05-01

    The aim of this paper is to investigate the effect of time delays on the stability of a zero-placement position and velocity feedback law for a vibratory system comprising harmonic excitation equipped with an electromagnetic active tuned mass damper (ATMD). The purpose of the active control is broadening the vibration attenuation envelope of a primary mass to a higher frequency region identified as from 50±0.5Hz with a passive tuned mass damper (TMD) to a wider range of 50±5Hz with an ATMD. Stability conditions of the closed-loop system are determined by studying the position of the system closed-loop poles after the introduction of time delays for different excitation frequencies. A computer simulation of the model predicted that the proposed control system is subject to instability after a critical time delay margin dependent upon the frequency of excitation and the finding were experimentally validated. Three solutions are derived and experimentally tested for minimising the effect of time delays on the stability of the control system. The first solution is associated with the introduction of more damping in the absorber system. The second incorporates using a time-delayed ATMD by tuning its original natural resonant frequency to beyond the nominal operational frequency range of the composite system. The third involves an online gain tuning of filter coefficients in a dual arrangement of low-pass and high-pass filters to eliminate the effect time delays by manipulating the signal phase shifts.

  5. Active vibration control of structure by Active Mass Damper and Multi-Modal Negative Acceleration Feedback control algorithm

    NASA Astrophysics Data System (ADS)

    Yang, Don-Ho; Shin, Ji-Hwan; Lee, HyunWook; Kim, Seoug-Ki; Kwak, Moon K.

    2017-03-01

    In this study, an Active Mass Damper (AMD) consisting of an AC servo motor, a movable mass connected to the AC servo motor by a ball-screw mechanism, and an accelerometer as a sensor for vibration measurement were considered. Considering the capability of the AC servo motor which can follow the desired displacement accurately, the Negative Acceleration Feedback (NAF) control algorithm which uses the acceleration signal directly and produces the desired displacement for the active mass was proposed. The effectiveness of the NAF control was proved theoretically using a single-degree-of-freedom (SDOF) system. It was found that the stability condition for the NAF control is static and it can effectively increase the damping of the target natural mode without causing instability in the low frequency region. Based on the theoretical results of the SDOF system, the Multi-Modal NAF (MMNAF) control is proposed to suppress the many natural modes of multi-degree-of-freedom (MDOF) systems using a single AMD. It was proved both theoretically and experimentally that the MMNAF control can suppress vibrations of the MDOF system.

  6. Robust hybrid mass damper

    NASA Astrophysics Data System (ADS)

    Collette, C.; Chesné, S.

    2016-08-01

    In this paper, the design of a hybrid mass damper (HMD) is proposed for the reduction of the resonant vibration amplitude of a multiple degree-of-freedom structure. HMD includes both passive and active elements. Combining these elements the system is fail-safe and its performances are comparable to usual purely active systems. The control law is a revisited direct velocity feedback. Two zeros are added to the controller to interact with the poles of the plant. The developed control law presents the particularity to be simple and hyperstable. The proposed HMD is compared to other classical control approaches for similar purpose in term of vibration attenuation, power consumption and stroke.

  7. DGA-based approach for optimal design of active mass damper for nonlinear structures considering ground motion effect

    NASA Astrophysics Data System (ADS)

    Mohebbi, Mohtasham; Rasouli Dabbagh, Hamed; Moradpour, Solmaz; Shakeri, Kazem; Tarbali, Karim

    2015-04-01

    This paper presents an effective method to design active mass dampers (AMDs) for mitigating the seismic response of nonlinear frames. The method is based on using the Newmark-based instantaneous optimal control algorithm for designing AMD, as well as using distributed genetic algorithm (DGA) for optimization of the active control system. To this end, an optimization problem has been defined which considers the parameters of the active control system as design variables and minimization of the maximum required control force of AMD as the objective function with some constraints defined on the maximum stroke length of AMD. Also, the effect of design excitation on performance of AMD under testing earthquakes has been studied. To assess the capabilities of the proposed method, a numerical example has been worked out where an AMD has been designed to control the response of an eight-story nonlinear shear building frame with hysteretic bilinear elasto-plastic behavior under white noise and real earthquake excitations. The designed control systems have been tested under a number of scaled and real earthquakes including both near and far-field earthquakes. Controller’s robustness against variations of structural parameters has also been assessed. The results of numerical simulations show the effectiveness, simplicity and capability of the proposed method in designing AMDs for nonlinear frames. Also comparing the performance of AMD system with that of passive tuned mass damper and active tendon control shows that the AMD has been more effective in reducing the seismic response of nonlinear frames under design and different testing earthquakes.

  8. SSME blade damper technology

    NASA Technical Reports Server (NTRS)

    Kielb, Robert E.; Griffin, Jerry H.

    1987-01-01

    Before 1975 turbine blade damper designs were based on experience and very simple mathematical models. Failure of the dampers to perform as expected showed the need to gain a better understanding of the physical mechanism of friction dampers. Over the last 10 years research on friction dampers for aeronautical propulsion systems has resulted in methods to optimize damper designs. The first-stage turbine blades on the Space Shuttle Main Engine (SSME) high-pressure oxygen pump have experienced cracking problems due to excessive vibration. A solution is to incorporate a well-designed friction dampers to attenuate blade vibration. The subject study, a cooperative effort between NASA Lewis and Carnegie-Mellon University, represents an application of recently developed friction damper technology to the SSME high-pressure oxygen turbopump. The major emphasis was the contractor's design known as the two-piece damper. Damping occurs at the frictional interface between the top half of the damper and the underside of the platforms of the adjacent blades. The lower half of the damper is an air seal to retard airflow in the volume between blade necks.

  9. Skyhook-based semi-active control of full-vehicle suspension with magneto-rheological dampers

    NASA Astrophysics Data System (ADS)

    Zhang, Hailong; Wang, Enrong; Min, Fuhong; Subash, Rakheja; Su, Chunyi

    2013-05-01

    The control study of vehicle semi-active suspension with magneto-rheological (MR) dampers has been attracted much attention internationally. However, a simple, real time and easy implementing semi-active controller has not been proposed for the MR full-vehicle suspension system, and a systematic analysis method has not been established for evaluating the multi-objective suspension performances of MR full-vehicle vertical, pitch and roll motions. For this purpose, according to the 7-degree of freedom (DOF) full-vehicle dynamic system, a generalized 7-DOF MR and passive full-vehicle dynamic model is set up by employing the modified Bouc-wen hysteretic force-velocity ( F-v) model of the MR damper. A semi-active controller is synthesized to realize independent control of the four MR quarter-vehicle sub-suspension systems in the full-vehicle, which is on the basis of the proposed modified skyhook damping scheme of MR quarter-vehicle sub-suspension system. The proposed controller can greatly simplify the controller design complexity of MR full-vehicle suspension and has merits of easy implementation in real application, wherein only absolute velocities of sprung and unsprung masses with reference to the road surface are required to measure in real time when the vehicle is moving. Furthermore, a systematic analysis method is established for evaluating the vertical, pitch and roll motion properties of both MR and passive full-vehicle suspensions in a more realistic road excitation manner, in which the harmonic, rounded pulse and real road measured random signals with delay time are employed as different road excitations inserted on the front and rear two wheels, by considering the distance between front and rear wheels in full-vehicle. The above excitations with different amplitudes are further employed as the road excitations inserted on left and right two wheels for evaluating the roll motion property. The multi-objective suspension performances of ride comfort and

  10. Testing a simple control law to reduce broadband frequency harmonic vibrations using semi-active tuned mass dampers

    NASA Astrophysics Data System (ADS)

    Moutinho, Carlos

    2015-05-01

    This paper is focused on the control problems related to semi-active tuned mass dampers (TMDs) used to reduce harmonic vibrations, specially involving civil structures. A simplified version of the phase control law is derived and its effectiveness is investigated and evaluated. The objective is to improve the functioning of control systems of this type by simplifying the measurement process and reducing the number of variables involved, making the control system more feasible and reliable. Because the control law is of ON/OFF type, combined with appropriate trigger conditions, the activity of the actuation system may be significantly reduced, which may be of few seconds a day in many practical cases, increasing the durability of the device and reducing its maintenance. Moreover, due to the ability of the control system to command the motion of the inertial mass, the semi-active TMD is relatively insensitive to its initial tuning, resulting in the capability of self-tuning and in the possibility of controlling several vibration modes of a structure over a significant broadband frequency.

  11. Hardware-in-the-loop simulation experiment for semi-active vibration control of lateral vibrations of railway vehicle by magneto-rheological fluid damper

    NASA Astrophysics Data System (ADS)

    Kwak, Moon K.; Lee, Jae-Ha; Yang, Dong-Ho; You, Won-Hee

    2014-07-01

    The active lateral suspension (ALS) of a train consists of either active or semi-active technologies. However, such an active system on a real railway vehicle is not easy to test because of cost and time. In this study, a hardware-in-the-loop simulation (HILS) system is developed to test the ALS. To this end, the dynamic model of a railway vehicle is equipped with the actuator, two bogies and four-wheel sets, and the ALS is used. The proposed HILS system consists of an alternating current servo motor connected to a ball-screw mechanism and a digital control system. The digital control system implements the dynamic model and the control algorithm. The design and manufacture of the HILS system are explained in detail. Both the passive damper and the magneto-rheological (MR) fluid damper are tested using the HILS system, where the sky-hook control algorithm was applied for the MR fluid damper. Experimental results show that the proposed HILS system can be effectively used for the performance estimation of the ALS.

  12. Active mass damper system for high-rise buildings using neural oscillator and position controller considering stroke limitation of the auxiliary mass

    NASA Astrophysics Data System (ADS)

    Hongu, J.; Iba, D.; Nakamura, M.; Moriwaki, I.

    2016-04-01

    This paper proposes a problem-solving method for the stroke limitation problem, which is related to auxiliary masses of active mass damper systems for high-rise buildings. The proposed method is used in a new simple control system for the active mass dampers mimicking the motion of bipedal mammals, which has a neural oscillator synchronizing with the acceleration response of structures and a position controller. In the system, the travel distance and direction of the auxiliary mass of the active mass damper is determined by reference to the output of the neural oscillator, and then, the auxiliary mass is transferred to the decided location by using a PID controller. The one of the purpose of the previouslyproposed system is stroke restriction problem avoidance of the auxiliary mass during large earthquakes by the determination of the desired value within the stroke limitation of the auxiliary mass. However, only applying the limited desired value could not rigorously restrict the auxiliary mass within the limitation, because the excessive inertia force except for the control force produced by the position controller affected on the motion of the auxiliary mass. In order to eliminate the effect on the auxiliary mass by the structural absolute acceleration, a cancellation method is introduced by adding a term to the control force of the position controller. We first develop the previously-proposed system for the active mass damper and the additional term for cancellation, and verity through numerical experiments that the new system is able to operate the auxiliary mass within the restriction during large earthquakes. Based on the comparison of the proposed system with the LQ system, a conclusion was drawn regarding which the proposed neuronal system with the additional term appears to be able to limit the stroke of the auxiliary mass of the AMD.

  13. Performance of a Single Liquid Column Damper for the Control of Dynamic Responses of a Tension Leg Platform

    NASA Astrophysics Data System (ADS)

    Jaksic, V.; Wright, C.; Chanayil, Afeef; Faruque Ali, Shaikh; Murphy, Jimmy; Pakrashi, Vikram

    2015-07-01

    Tuned liquid column dampers have been proved to be successful in mitigating the dynamic responses of civil infrastructure. There have been some recent applications of this concept on wind turbines and this passive control system can help to mitigate responses of offshore floating platforms and wave devices. The control of dynamic responses of these devices is important for reducing loads on structural elements and facilitating operations and maintenance (O&M) activities. This paper outlines the use of a tuned single liquid column damper for the control of a tension leg platform supported wind turbine. Theoretical studies were carried out and a scaled model was tested in a wave basin to assess the performance of the damper. The tests on the model presented in this paper correspond to a platform with a very low natural frequency for surge, sway and yaw motions. For practical purposes, it was not possible to tune the liquid damper exactly to this frequency. The consequent approach taken and the efficiency of such approach are presented in this paper. Responses to waves of a single frequency are investigated along with responses obtained from wave spectra characterising typical sea states. The extent of control is quantified using peak and root mean squared dynamic responses respectively. The tests present some guidelines and challenges for testing scaled devices in relation to including response control mechanisms. Additionally, the results provide a basis for dictating future research on tuned liquid column damper based control on floating platforms.

  14. Sliding mode fault detection and fault-tolerant control of smart dampers in semi-active control of building structures

    NASA Astrophysics Data System (ADS)

    Yeganeh Fallah, Arash; Taghikhany, Touraj

    2015-12-01

    Recent decades have witnessed much interest in the application of active and semi-active control strategies for seismic protection of civil infrastructures. However, the reliability of these systems is still in doubt as there remains the possibility of malfunctioning of their critical components (i.e. actuators and sensors) during an earthquake. This paper focuses on the application of the sliding mode method due to the inherent robustness of its fault detection observer and fault-tolerant control. The robust sliding mode observer estimates the state of the system and reconstructs the actuators’ faults which are used for calculating a fault distribution matrix. Then the fault-tolerant sliding mode controller reconfigures itself by the fault distribution matrix and accommodates the fault effect on the system. Numerical simulation of a three-story structure with magneto-rheological dampers demonstrates the effectiveness of the proposed fault-tolerant control system. It was shown that the fault-tolerant control system maintains the performance of the structure at an acceptable level in the post-fault case.

  15. Compact Vibration Damper

    NASA Technical Reports Server (NTRS)

    Ivanco, Thomas G. (Inventor)

    2014-01-01

    A vibration damper includes a rigid base with a mass coupled thereto for linear movement thereon. Springs coupled to the mass compress in response to the linear movement along either of two opposing directions. A converter coupled to the mass converts the linear movement to a corresponding rotational movement. A rotary damper coupled to the converter damps the rotational movement.

  16. A New Generation of Magneto-Rheological Fluid Dampers

    DTIC Science & Technology

    2007-11-02

    suspension systems [20]. Many of the studies on semi-active suspension systems consider dampers using electro-hydraulic valves but recently magneto...HMMWV prove that the power absorbed by the driver is reduced up to 70% [21]. MRF dampers do not need any movable valve to change a force characteristic...external magnetic field to valves . Recently, an MRF damper for a High Mobility Multi-Purpose Wheeled Vehicle (HMMWV) has been developed at the

  17. Active motion and load control of floating offshore wind turbines

    NASA Astrophysics Data System (ADS)

    Jalili, Kaveh

    The research in this thesis is focused on stabilization and load reduction of floating offshore wind turbine (FOWT) structures for both the fore-aft (pitch) and side-to-side (roll) directions. Based on the Tuned Mass Damper (TMD) and Active Vane concepts recently proposed, two composite actuation schemes are investigated. The first scheme is to apply the horizontal vane and vertical vane to platform pitch and roll, respectively, resulting in the so-called Double Vane Actuation (DVA) scheme. The second scheme is the combination of the TMD based pitch control and active vertical vane based roll control, resulting in the so-called Hybrid Actuation (HA) scheme. Simulation results of DVA show great reductions of motions and loads in the fore-aft and side-to-side directions. Performance of HA is investigated by extensive simulations based on the IEC61400-3 standard and results show significant and consistent motions and loads reductions in both FA and SS directions.

  18. An electroviscous damper

    NASA Technical Reports Server (NTRS)

    Nikolajsen, Jorgen L.; Hoque, M. S.

    1989-01-01

    A new type of vibration damper for rotor systems was developed and tested. The damper contains electroviscous fluid which solidifies and provides Coulomb damping when an electric voltage is imposed across the fluid. The damping capacity is controlled by the voltage. The damper was incorporated in a flexible rotor system and found to be able to damp out high levels of unbalanced excitation. Other proven advantages include controllability, simplicity, and no requirement for oil supply. Still unconfirmed are the capabilities to eliminate critical speeds and to suppress rotor instabilities.

  19. Science Activities in Energy: Wind Energy.

    ERIC Educational Resources Information Center

    Oak Ridge Associated Universities, TN.

    Included in this science activities energy package are 12 activities related to wind energy for elementary students. Each activity is outlined on a single card and is introduced by a question. Topics include: (1) At what time of day is there enough wind to make electricity where you live?; (2) Where is the windiest spot on your schoolground?; and…

  20. Damper bearing rotordynamics

    NASA Technical Reports Server (NTRS)

    Elrod, David A.

    1990-01-01

    High side loads reduce the life of the Space Shuttle Main Engine (SSME) High Pressure Oxygen Turbopump (HPOTP) bearings. High stiffness damper seals were recommended to reduce the loads on the pump and turbine end bearings in the HPOTP. The seals designed for use on the pump end are expected to adequately reduce the bearing loads; the predicted performance of the planned turbine end seal is marginal. An alternative to the suggested turbine end seal design is a damper bearing with radial holes from the pressurized center of the turbopump rotor, feeding a smooth land region between two rough-stator/smooth-rotor annular seals. An analysis was prepared to predict the leakage and rotor dynamic coefficients (stiffness, damping, and added mass) of the damper bearing. Governing equations of the seal analysis modified to model the damper bearing; differences between the upstream conditions of the damper bearing and a typical annular seal; prediction of the damper bearing analysis; and assumptions of the analysis which require further investigation are described.

  1. Frequency analysis of a semi-active suspension with magneto-rheological dampers

    NASA Astrophysics Data System (ADS)

    Andronic, Florin; Mihai, Ioan; Suciu, Cornel; Beniuga, Marius

    2015-02-01

    Suspension systems for motor vehicles are constantly evolving in order to ensure vehicle stability and traffic safety under all driving conditions. The present work aims to highlight the influence factors in the case of a quarter car model for semi-active suspensions. The functions that must be met by such suspension systems are first presented. Mathematical models for passive systems are first illustrated and then customized for the semi-active case. A simulation diagram was conceived for Matlab Simulink. The obtained simulation results allow conducting a frequency analysis of the passive and semi-active cases of the quarter car model. Various charts for Passive Suspension Transmissibility and for the Effect of Damping on Vertical Acceleration Response were obtained for both passive and semi-active situations. Analysis of obtained results allowed evaluating of the suspension systems behavior and their frequency dependence. Significant differences were found between the behaviors of passive and semi-active suspensions. It was found that semi-active suspensions ensure damping in accordance to the chosen control method, and are much more efficient than passive ones.

  2. Experimental evaluation of a neural-oscillator-driven active mass damper system

    NASA Astrophysics Data System (ADS)

    Iba, Daisuke; Hongu, Junichi

    2014-03-01

    This paper proposes a new active dynamic absorber control system for high-rise buildings using a neural oscillator and a map, which estimates the amplitude level of the oscillator, and shows some experimental results by using an apparatus, which realizes the proposed control algorithm. The proposed system decides the travel distance and direction of the auxiliary mass of the dynamic absorber using the output of oscillator, which is the filtering result of structure acceleration responses by the property of the oscillator, and Amplitude-Phase map (AP-map) for estimation of the structural response in specific frequency between synchronization region, and then, transfer the auxiliary mass to the predetermined location by using a position controller. In addition, the developed active dynamic absorber system is mounted on the top of the experimental single degree of freedom structure, which represents high-rise buildings, and consists of the auxiliary mass, a DC motor, a ball screw, a microcomputer, a laser displacement sensor, and an acceleration sensor. The proposed AP-map and the algorithm to determine the travel direction of the mass using the oscillator output are embedded in the microcomputer. This paper starts by illuminating the relation among subsystems of the proposed system with reference to a block diagram, and then, shows experimental responses of the whole system excited by earthquakes to confirm the validity of the proposed system.

  3. Wind Powering America FY06 Activities Summary

    SciTech Connect

    Not Available

    2007-02-01

    The Wind Powering America FY06 Activities Summary reflects the accomplishments of our state wind working groups, our programs at the National Renewable Energy Laboratory, and our partner organizations. The national WPA team remains a leading force for moving wind energy forward in the United States. WPA continues to work with its national, regional, and state partners to communicate the opportunities and benefits of wind energy to a diverse set of stakeholders. WPA now has 29 state wind working groups (welcoming New Jersey, Indiana, Illinois, and Missouri in 2006) that form strategic alliances to communicate wind's benefits to the state stakeholders. More than 120 members of national and state public and private sector organizations from 34 states attended the 5th Annual WPA All-States Summit in Pittsburgh in June.

  4. Active load control techniques for wind turbines.

    SciTech Connect

    van Dam, C.P.; Berg, Dale E.; Johnson, Scott J.

    2008-07-01

    This report provides an overview on the current state of wind turbine control and introduces a number of active techniques that could be potentially used for control of wind turbine blades. The focus is on research regarding active flow control (AFC) as it applies to wind turbine performance and loads. The techniques and concepts described here are often described as 'smart structures' or 'smart rotor control'. This field is rapidly growing and there are numerous concepts currently being investigated around the world; some concepts already are focused on the wind energy industry and others are intended for use in other fields, but have the potential for wind turbine control. An AFC system can be broken into three categories: controls and sensors, actuators and devices, and the flow phenomena. This report focuses on the research involved with the actuators and devices and the generated flow phenomena caused by each device.

  5. Hermetically sealed vibration damper

    NASA Technical Reports Server (NTRS)

    Wheatley, D. G.

    1969-01-01

    Simple fluidic vibration damper for installation at each pivotal mounting between gimbals isolates inertial measuring units from external vibration and other disruptive forces. Installation between each of the three gimbal axes can dampen vibration and shock in any direction while permitting free rotation of the gimbals.

  6. Airfoil Vibration Dampers program

    NASA Technical Reports Server (NTRS)

    Cook, Robert M.

    1991-01-01

    The Airfoil Vibration Damper program has consisted of an analysis phase and a testing phase. During the analysis phase, a state-of-the-art computer code was developed, which can be used to guide designers in the placement and sizing of friction dampers. The use of this computer code was demonstrated by performing representative analyses on turbine blades from the High Pressure Oxidizer Turbopump (HPOTP) and High Pressure Fuel Turbopump (HPFTP) of the Space Shuttle Main Engine (SSME). The testing phase of the program consisted of performing friction damping tests on two different cantilever beams. Data from these tests provided an empirical check on the accuracy of the computer code developed in the analysis phase. Results of the analysis and testing showed that the computer code can accurately predict the performance of friction dampers. In addition, a valuable set of friction damping data was generated, which can be used to aid in the design of friction dampers, as well as provide benchmark test cases for future code developers.

  7. Smart hybrid rotary damper

    NASA Astrophysics Data System (ADS)

    Yang, C. S. Walter; DesRoches, Reginald

    2014-03-01

    This paper develops a smart hybrid rotary damper using a re-centering smart shape memory alloy (SMA) material as well as conventional energy-dissipating metallic plates that are easy to be replaced. The ends of the SMA and steel plates are inserted in the hinge. When the damper rotates, all the plates bend, providing energy dissipating and recentering characteristics. Such smart hybrid rotary dampers can be installed in structures to mitigate structural responses and to re-center automatically. The damaged energy-dissipating plates can be easily replaced promptly after an external excitation, reducing repair time and costs. An OpenSEES model of a smart hybrid rotary was established and calibrated to reproduce the realistic behavior measured from a full-scale experimental test. Furthermore, the seismic performance of a 3-story moment resisting model building with smart hybrid rotary dampers designed for downtown Los Angeles was also evaluated in the OpenSEES structural analysis software. Such a smart moment resisting frame exhibits perfect residual roof displacement, 0.006", extremely smaller than 18.04" for the conventional moment resisting frame subjected to a 2500 year return period ground motion for the downtown LA area (an amplified factor of 1.15 on Kobe earthquake). The smart hybrid rotary dampers are also applied into an eccentric braced steel frame, which combines a moment frame system and a bracing system. The results illustrate that adding smart hybrid rotaries in this braced system not only completely restores the building after an external excitation, but also significantly reduces peak interstory drifts.

  8. Enhanced damping for bridge cables using a self-sensing MR damper

    NASA Astrophysics Data System (ADS)

    Chen, Z. H.; Lam, K. H.; Ni, Y. Q.

    2016-08-01

    This paper investigates enhanced damping for protecting bridge stay cables from excessive vibration using a newly developed self-sensing magnetorheological (MR) damper. The semi-active control strategy for effectively operating the self-sensing MR damper is formulated based on the linear-quadratic-Gaussian (LQG) control by further considering a collocated control configuration, limited measurements and nonlinear damper dynamics. Due to its attractive feature of sensing-while-damping, the self-sensing MR damper facilitates the collocated control. On the other hand, only the sensor measurements from the self-sensing device are employed in the feedback control. The nonlinear dynamics of the self-sensing MR damper, represented by a validated Bayesian NARX network technique, are further accommodated in the control formulation to compensate for its nonlinearities. Numerical and experimental investigations are conducted on stay cables equipped with the self-sensing MR damper operated in passive and semi-active control modes. The results verify that the collocated self-sensing MR damper facilitates smart damping for inclined cables employing energy-dissipative LQG control with only force and displacement measurements at the damper. It is also demonstrated that the synthesis of nonlinear damper dynamics in the LQG control enhances damping force tracking efficiently, explores the features of the self-sensing MR damper, and achieves better control performance over the passive MR damping control and the Heaviside step function-based LQG control that ignores the damper dynamics.

  9. Wind Powering America FY07 Activities Summary

    SciTech Connect

    Not Available

    2008-02-01

    The Wind Powering America FY07 Activities Summary reflects the accomplishments of our state wind working groups, our programs at the National Renewable Energy Laboratory, and our partner organizations. The national WPA team remains a leading force for moving wind energy forward in the United States. WPA continues to work with its national, regional, and state partners to communicate the opportunities and benefits of wind energy to a diverse set of stakeholders. WPA now has 30 state wind working groups (welcoming Georgia and Wisconsin in 2007) that form strategic alliances to communicate wind's benefits to the state stakeholders. More than 140 members of national and state public and private sector organizations from 39 U.S. states and Canada attended the 6th Annual WPA All-States Summit in Los Angeles in June. WPA's emphasis remains on the rural agricultural sector, which stands to reap the significant economic development benefits of wind energy development. Additionally, WPA continues its program of outreach, education, and technical assistance to Native American communities, public power entities, and regulatory and legislative bodies.

  10. Extended Kalman filter based structural damage detection for MR damper controlled structures

    NASA Astrophysics Data System (ADS)

    Jin, Chenhao; Jang, Shinae; Sun, Xiaorong; Jiang, Zhaoshuo; Christenson, Richard

    2016-04-01

    The Magneto-rheological (MR) dampers have been widely used in many building and bridge structures against earthquake and wind loadings due to its advantages including mechanical simplicity, high dynamic range, low power requirements, large force capacity, and robustness. However, research about structural damage detection methods for MR damper controlled structures is limited. This paper aims to develop a real-time structural damage detection method for MR damper controlled structures. A novel state space model of MR damper controlled structure is first built by combining the structure's equation of motion and MR damper's hyperbolic tangent model. In this way, the state parameters of both the structure and MR damper are added in the state vector of the state space model. Extended Kalman filter is then used to provide prediction for state variables from measurement data. The two techniques are synergistically combined to identify parameters and track the changes of both structure and MR damper in real time. The proposed method is tested using response data of a three-floor MR damper controlled linear building structure under earthquake excitation. The testing results show that the adaptive extended Kalman filter based approach is capable to estimate not only structural parameters such as stiffness and damping of each floor, but also the parameters of MR damper, so that more insights and understanding of the damage can be obtained. The developed method also demonstrates high damage detection accuracy and light computation, as well as the potential to implement in a structural health monitoring system.

  11. Vibration power generator for a linear MR damper

    NASA Astrophysics Data System (ADS)

    Sapiński, Bogdan

    2010-10-01

    The paper describes the structure and the results of numerical calculations and experimental tests of a newly developed vibration power generator for a linear magnetorheological (MR) damper. The generator consists of permanent magnets and coil with foil winding. The device produces electrical energy according to Faraday's law of electromagnetic induction. This energy is applied to vary the damping characteristics of the MR damper attached to the generator by the input current produced by the device. The objective of the numerical calculations was to determine the magnetic field distribution in the generator as well as the electric potential and current density in the generator's coil during the idle run and under the load applied to the MR damper control coil. The results of the calculations were used during the design and manufacturing stages of the device. The objective of the experimental tests carried out on a dynamic testing machine was to evaluate the generator's efficiency and to compare the experimental and predicted data. The experimental results demonstrate that the engineered device enables a change in the kinetic energy of the reciprocal motion of the MR damper which leads to variations in the damping characteristics. That is why the generator may be used to build up MR damper based vibration control systems which require no external power.

  12. Analysis of high load dampers

    NASA Technical Reports Server (NTRS)

    Bhat, S. T.; Buono, D. F.; Hibner, D. H.

    1981-01-01

    High load damping requirements for modern jet engines are discussed. The design of damping systems which could satisfy these requirements is also discusseed. In order to evaluate high load damping requirements, engines in three major classes were studied; large transport engines, small general aviation engines, and military engines. Four damper concepts applicable to these engines were evaluated; multi-ring, cartridge, curved beam, and viscous/friction. The most promising damper concept was selected for each engine and performance was assessed relative to conventional dampers and in light of projected damping requirements for advanced jet engines.

  13. The Geography of Wind Energy: Problem Solving Activities.

    ERIC Educational Resources Information Center

    Lahart, David E.; Allen, Rodney F.

    1985-01-01

    Today there are many attempts to use wind machines to confront the increasing costs of electricity. Described are activities to help secondary students understand wind energy, its distribution, applications, and limitations. (RM)

  14. Evidence of active region imprints on the solar wind structure

    NASA Technical Reports Server (NTRS)

    Hick, P.; Jackson, B. V.

    1995-01-01

    A common descriptive framework for discussing the solar wind structure in the inner heliosphere uses the global magnetic field as a reference: low density, high velocity solar wind emanates from open magnetic fields, with high density, low speed solar wind flowing outward near the current sheet. In this picture, active regions, underlying closed magnetic field structures in the streamer belt, leave little or no imprint on the solar wind. We present evidence from interplanetary scintillation measurements of the 'disturbance factor' g that active regions play a role in modulating the solar wind and possibly contribute to the solar wind mass output. Hence we find that the traditional view of the solar wind, though useful in understanding many features of solar wind structure, is oversimplified and possibly neglects important aspects of solar wind dynamics

  15. 46 CFR 131.899 - Fire dampers.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 4 2012-10-01 2012-10-01 false Fire dampers. 131.899 Section 131.899 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OFFSHORE SUPPLY VESSELS OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.899 Fire dampers. Each fire damper installed within the boundary...

  16. 46 CFR 131.899 - Fire dampers.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 4 2013-10-01 2013-10-01 false Fire dampers. 131.899 Section 131.899 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OFFSHORE SUPPLY VESSELS OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.899 Fire dampers. Each fire damper installed within the boundary...

  17. 46 CFR 131.899 - Fire dampers.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Fire dampers. 131.899 Section 131.899 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OFFSHORE SUPPLY VESSELS OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.899 Fire dampers. Each fire damper installed within the boundary...

  18. 46 CFR 131.899 - Fire dampers.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 4 2014-10-01 2014-10-01 false Fire dampers. 131.899 Section 131.899 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OFFSHORE SUPPLY VESSELS OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.899 Fire dampers. Each fire damper installed within the boundary...

  19. 46 CFR 131.899 - Fire dampers.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Fire dampers. 131.899 Section 131.899 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OFFSHORE SUPPLY VESSELS OPERATIONS Markings for Fire Equipment and Emergency Equipment § 131.899 Fire dampers. Each fire damper installed within the boundary...

  20. Dampers for Stationary Labyrinth Seals

    NASA Technical Reports Server (NTRS)

    El-Aini, Yehia; Mitchell, William; Roberts, Lawrence; Montgomery, Stuart; Davis, Gary

    2011-01-01

    Vibration dampers have been invented that are incorporated as components within the stationary labyrinth seal assembly. These dampers are intended to supplement other vibration-suppressing features of labyrinth seals in order to reduce the incidence of high-cycle-fatigue failures, which have been known to occur in the severe vibratory environments of jet engines and turbopumps in which labyrinth seals are typically used. A vibration damper of this type includes several leaf springs and/or a number of metallic particles (shot) all held in an annular seal cavity by a retaining ring. The leaf springs are made of a spring steel alloy chosen, in conjunction with design parameters, to maintain sufficient preload to ensure effectiveness of damping at desired operating temperatures. The cavity is vented via a small radial gap between the retaining ring and seal housing. The damping mechanism is complex. In the case of leaf springs, the mechanism is mainly friction in the slippage between the seal housing and individual dampers. In the case of a damper that contains shot, the damping mechanism includes contributions from friction between individual particles, friction between particles and cavity walls, and dissipation of kinetic energy of impact. The basic concept of particle/shot vibration dampers has been published previously; what is new here is the use of such dampers to suppress traveling-wave vibrations in labyrinth seals. Damping effectiveness depends on many parameters, including, but not limited to, coefficient of friction, mode shape, and frequency and amplitude of vibrational modes. In tests, preloads of the order of 6 to 15 lb (2.72 to 6.8 kilograms) per spring damper were demonstrated to provide adequate damping levels. Effectiveness of shot damping of vibrations having amplitudes from 20 to 200 times normal terrestrial gravitational acceleration (196 to 1,960 meters per square second) and frequencies up to 12 kHz was demonstrated for shot sizes from 0.032 to

  1. Vibration control of a structure using Magneto-Rheological grease damper

    NASA Astrophysics Data System (ADS)

    Sugiyama, Shinya; Sakurai, Tomoki; Morishita, Shin

    2013-09-01

    This paper describes an application study of Magneto-Rheological (MR) grease damper to a structure with three stories. MR fluid is known as one of successful smart materials whose rheological properties can be varied by magnetic field strength, and has been applied to various kinds of device such as dampers, clutches, engine mounts, etc. However, ferromagnetic particles dispersed in MR fluid settle out of the suspension after a certain interval due to the density difference between the particles and their career fluid. To overcome this defect, we have developed a new type of controllable working fluid using grease as the career of magnetic particles. Network of thickener in grease is expected to hold the magnetic particles and prevent them from settled down. No or little sedimentation was observed in MR grease whose characteristics could be controlled by the magnetic field strength. MR grease was introduced into a cylindrical damper and its performance was studied. As a result, it was confirmed that the damping force of MR grease damper could be controlled by the applied electric current to the coil in the cylinder of damper. Furthermore, vibration response of a three-story model structure equipped with MR grease damper was investigated experimentally, and it was shown that MR grease damper worked effectively as a semi-active damper.

  2. Novel design of a self powered and self sensing magneto-rheological damper

    NASA Astrophysics Data System (ADS)

    Meftahul Ferdaus, Mohammad; Rashid, M. M.; Bhuiyan, M. M. I.; Muthalif, Asan Gani Bin Abdul; Hasan, M. R.

    2013-12-01

    Magneto-rheological (MR) dampers are semi-active control devices and use MR fluids. Magneto-rheological dampers have successful applications in mechatronics engineering, civil engineering and numerous areas of engineering. At present, traditional MR damper systems, require a isolated power supply and dynamic sensor. This paper presents the achievability and accuracy of a self- powered and self-sensing magneto-rheological damper using harvested energy from the vibration and shock environment in which it is deployed and another important part of this paper is the increased yield stress of the Magneto rheological Fluids. Magneto rheological fluids using replacement of glass beads for Magnetic Particles to surge yield stress is implemented here. Clearly this shows better result on yield stress, viscosity, and settling rate. Also permanent magnet generator (PMG) is designed and attached to a MR damper. For evaluating the self-powered MR damper's vibration mitigating capacity, an Engine Mount System using the MR damper is simulated. The ideal stiffness of the PMG for the Engine Mount System (EMS) is calculated by numerical study. The vibration mitigating performance of the EMS employing the self-powered & self sensing MR damper is theoretically calculated and evaluated in the frequency domain.

  3. Digital control system for space structural dampers

    NASA Technical Reports Server (NTRS)

    Haviland, J. K.

    1984-01-01

    Digital control systems for space structural dampers, also referred to as inertia or proof-mass dampers are investigated. A damper concept is improved by adding a small taper to the proof-mass, and using a proximeter to determine position. Another damper using a three inch stroke rather than the standard one inch stroke is described. Provisions are made for a relative velocity feedback. In one approach, the digital controller is modified to accept the signal from a linear velocity transducer. In the other, the velocity feedback is included in the digital program. An overall system concept for the use of the dampers is presented.

  4. A new magnetorheological damper for seismic control

    NASA Astrophysics Data System (ADS)

    Ding, Yang; Zhang, Lu; Zhu, Hai-Tao; Li, Zhong-Xian

    2013-11-01

    This paper proposes a new MR damper with bidirectional adjusting damping forces to enhance the fail-safe property of the MR damper. The structure of the composite magnetic circuits is improved for the new damper. Four prototype dampers are fabricated and tested by magnetic field tests and dynamic tests. The magnetic field distribution in the damping path and the dynamic properties of the dampers with different input currents are obtained. The Gompertz model is proposed to portray the dynamic behavior of the prototype dampers. The study shows that, due to the improved structure of composite magnetic circuits, the prototype dampers can maintain a medium damping force with zero current input. This behavior may ensure a better fail-safe property and avoid settlement of MR fluid compared with conventional MR dampers. Furthermore, the minimum and maximum output powers of the proposed dampers can be obtained at the states of the negative peak and positive peak of currents inputs, respectively. In addition, the dynamic range of controllable force is wider than that of conventional MR dampers. The analysis further shows that the proposed Gompertz model can precisely portray the nonlinear hysteretic behavior of the proposed dampers without complicated function forms.

  5. Computational investigation on the application of using microjets as active aerodynamic load control for wind turbines

    NASA Astrophysics Data System (ADS)

    Blaylock, Myra Louise

    A fast, efficient way to control loads on industrial scale turbines is important for the growth of the wind industry. Active Aerodynamic Load Control (AALC) is one area which addresses this need. In particular, microjets, which are pneumatic jets located at the trailing edge of a wind turbine blade and blow perpendicular to the blade surface, are a possible AALC candidate. First, the Computational Fluid Dynamics (CFD) solver OVERFLOW is used to explore the effects of a microjet on lift, drag, and pitching moment. Then the interaction between an aerodynamic disturbance and an airfoil equipped with a microjet is modeled. The object of this dissertation is to investigate microtabs as viable AALC devices by presenting their aerodynamic properties and testing whether a proportional-integral (PI) controlled jets can alleviate loads caused by wind gusts. The use of CFD to simulate a microjet is validated by comparing the results to both previous experiments found in the literature as well as wind tunnel tests completed at UC Davis. The aerodynamic effectiveness of the jet is investigated as a function of various parameters such as Reynolds number, angle of attack, and the momentum coefficient of the jet. The effects of the microjet are found to be very similar to another AALC device, the microtab. An aerodynamic disturbance is simulated, and a control algorithm which is incorporated into the OVERFLOW code is used to activate the microjet, thus reducing the change of the blade load due to the gust. Finally, a more realistic model is made by adding both a linear and a torsional spring and damper to represent the blade movement. This two-degree of freedom system shows that during a gust the vertical blade movement is reduced when the microjets are activated. Microjets are found to work well to alleviate the changes in aerodynamic loads felt by the airfoil, and are therefore a good candidate for a practical AALC device. However, further investigation is needed in the areas of

  6. A proposed SSC damper system

    SciTech Connect

    Tsyganov, E.; Dugan, G.; Lopez, G.; Meinke, R.; Nexson, W.; Talman, R. )

    1994-02-01

    A transverse beam damper system for providing stability against ground motion, resistive wall instabilities, and other effects is the Superconducting Super Collider (SSC) is outlined. Use of two monitors, as in existing designs, provides phase insensitivity. The novel feature is the use of two kickers, which permits almost exact orbit compensation within one turn. Bunch-by-bunch stabilization requires fast computation.

  7. Sources of solar wind over the solar activity cycle

    PubMed Central

    Poletto, Giannina

    2012-01-01

    Fast solar wind has been recognized, about 40 years ago, to originate in polar coronal holes (CHs), that, since then, have been identified with sources of recurrent high speed wind streams. As of today, however, there is no general consensus about whether there are, within CHs, preferential locations where the solar wind is accelerated. Knowledge of slow wind sources is far from complete as well. Slow wind observed in situ can be traced back to its solar source by backward extrapolation of magnetic fields whose field lines are streamlines of the outflowing plasma. However, this technique often has not the necessary precision for an indisputable identification of the region where wind originates. As the Sun progresses through its activity cycle, different wind sources prevail and contribute to filling the heliosphere. Our present knowledge of different wind sources is here summarized. Also, a Section addresses the problem of wind acceleration in the low corona, as inferred from an analysis of UV data, and illustrates changes between fast and slow wind profiles and possible signatures of changes along the solar cycle. A brief reference to recent work about the deep roots of solar wind and their changes over different solar cycles concludes the review. PMID:25685421

  8. Sources of solar wind over the solar activity cycle.

    PubMed

    Poletto, Giannina

    2013-05-01

    Fast solar wind has been recognized, about 40 years ago, to originate in polar coronal holes (CHs), that, since then, have been identified with sources of recurrent high speed wind streams. As of today, however, there is no general consensus about whether there are, within CHs, preferential locations where the solar wind is accelerated. Knowledge of slow wind sources is far from complete as well. Slow wind observed in situ can be traced back to its solar source by backward extrapolation of magnetic fields whose field lines are streamlines of the outflowing plasma. However, this technique often has not the necessary precision for an indisputable identification of the region where wind originates. As the Sun progresses through its activity cycle, different wind sources prevail and contribute to filling the heliosphere. Our present knowledge of different wind sources is here summarized. Also, a Section addresses the problem of wind acceleration in the low corona, as inferred from an analysis of UV data, and illustrates changes between fast and slow wind profiles and possible signatures of changes along the solar cycle. A brief reference to recent work about the deep roots of solar wind and their changes over different solar cycles concludes the review.

  9. Special Fluid Viscous Dampers For The Messina Strait Bridge

    SciTech Connect

    Colato, Gian Paolo; Infanti, Samuele; Castellano, Maria Gabriella

    2008-07-08

    The Messina Strait Bridge would be the world's longest suspension bridge, with a design earthquake characterised by a PGA value of 0.58 g and a distance between the ipocenter and the bridge of 15 km. Said critical structure of course would need a suitable restraint system for traffic braking loads, wind and seismic actions. Each type of load requires a specific behaviour of the restraint system, making its design a big challenge.The restraint system comprises special types of fluid viscous dampers, installed both in longitudinal and transverse direction, both at the towers and at the anchorages. In seismic conditions they behave as viscous dampers, to reduce the forces on the structural elements and the movements of the bridge deck. But in service dynamic conditions, e.g. under traffic or wind load, the devices shall behave like shock transmission units, thus preventing the longitudinal and transverse movements of the deck.FIP Industriale cooperated with the selected General Contractor, a consortium lead by Impregilo, in the design of said viscous dampers. This paper describes the main features of said devices.

  10. Update of wind resource assessment activities at NREL

    SciTech Connect

    Elliott, D L; Schwartz, M N

    1996-07-01

    The goal of the wind resource assessment activity at the National Renewable Energy Laboratory (NREL) is to improve the characterization of the wind resource for regions where there are market opportunities for U.S. wind energy technology. A variety of wind resource assessment activities have recently been undertaken at NREL in support of this effort. The major tasks during the past year include aiding the establishment of new wind measurement programs in the United States, the development of updated comprehensive meteorological and geographical data bases to be used for resource assessments in the United States and abroad, and designing progressive wind resource mapping tools to facilitate products used in support of emerging markets.

  11. Experimental and numerical investigations on the dynamic response of turbine blades with tip pin dampers

    NASA Astrophysics Data System (ADS)

    Zucca, S.; Berruti, T.; Cosi, L.

    2016-09-01

    Friction dampers are used to reduce vibration amplitude of turbine blades. The dynamics of these assemblies (blades + dampers) is nonlinear and the analysis is challenging from both the experimental and the numerical point of view. The study of the dynamics of blades with a tip damper is the aim of the present paper. The blades with axial-entry fir tree attachment carry a damper in a pocket between the blade covers. Pin dampers significantly affect the resonance frequency of the first blade bending mode and introduces non linearity due to friction contacts. A test rig, made of two blades held in a fixture by an hydraulic press with one damper between the blades was used for the experimental activity. Three different types of dampers (cylindrical, asymmetrical, wedge) have been experimentally investigated and experiments have shown that asymmetrical damper performs better than the others. The response of the blades with the asymmetrical damper was then simulated with a non linear code based on the Harmonic Balance Method (HBM). In the analysis, both the blade and the damper are modelled with the Finite Elements and then the matrices reduced with the Craig- Bampton Component Mode Synthesis (CB-CMS), while the periodical contact forces are modelled with state-of-the-art node-to-node contact elements. Numerical analysis has shown a strong influence of the actual extent of the contact area on the dynamics of the assembly. A model updating process was necessary. In the end, the numerical predictions match very well with the experimental curves.

  12. Wind Turbines Adaptation to the Variability of the Wind Field

    NASA Astrophysics Data System (ADS)

    Ulianov, Yuriy; Martynenko, Gennadii; Misaylov, Vitaliy; Soliannikova, Iuliia

    2010-05-01

    including combined RF-acoustic antenna installed coaxially with the gondola of the wind power turbine. The work of the technique is synchronized with rotation of blades to eliminate their shielding action. Dangerous in terms of dynamic strength is the wind load pulse, the rise time which is comparable with the period of the natural frequency of the wind turbine elements (blade, tower, rotor, etc.). The amplitude decay of resonant vibrations at critical values of the speed of rotation can be realized through the use of mechanical elastic supports with nonlinear artificial dampers. They have a high coefficient of resistance, but may cause self-excited oscillations. We propose the way to deal with raised vibration of wind turbine elements at the expense of short-term increase of damping in the range of critical rotary axis speeds or during impulsive effects of wind loadings (wind gusts). This is possible through the use of non-linear electromagnetic dampers or active magnetic bearings. Their feature is the possibility of varying the mechanical stiffness and damping properties by changing the electrical parameters of electromagnets. The controlling of these parameters is carried out by the control system (CS) with the information feedback on the spatial-temporal structure of the wind field obtained from IRASS. In the composition of the CS can also be included the rotational speed sensor of the WPT rotor. This approach to the adaptation of wind turbines will allow to reduce vibration and to perform early compensation of the load on their components, which arise under the wind gusts. In addition, corrections about the wind field obtained with IRASS, would increase the mean power of WPT.

  13. Solar wind control of auroral zone geomagnetic activity

    NASA Technical Reports Server (NTRS)

    Clauer, C. R.; Mcpherron, R. L.; Searls, C.; Kivelson, M. G.

    1981-01-01

    Solar wind magnetosphere energy coupling functions are analyzed using linear prediction filtering with 2.5 minute data. The relationship of auroral zone geomagnetic activity to solar wind power input functions are examined, and a least squares prediction filter, or impulse response function is designed from the data. Computed impulse response functions are observed to have characteristics of a low pass filter with time delay. The AL index is found well related to solar wind energy functions, although the AU index shows a poor relationship. High frequency variations of auroral indices and substorm expansions are not predictable with solar wind information alone, suggesting influence by internal magnetospheric processes. Finally, the epsilon parameter shows a poorer relationship with auroral geomagnetic activity than a power parameter, having a VBs solar wind dependency.

  14. Lateral dampers for thrust bearings

    NASA Technical Reports Server (NTRS)

    Hibner, D. H.; Szafir, D. R.

    1985-01-01

    The development of lateral damping schemes for thrust bearings was examined, ranking their applicability to various engine classes, selecting the best concept for each engine class and performing an in-depth evaluation. Five major engine classes were considered: large transport, military, small general aviation, turboshaft, and non-manrated. Damper concepts developed for evaluation were: curved beam, constrained and unconstrained elastomer, hybrid boost bearing, hydraulic thrust piston, conical squeeze film, and rolling element thrust face.

  15. Damper Spring For Omega Seal

    NASA Technical Reports Server (NTRS)

    Maclaughlin, Scott T.; Montgomery, Stuart K.

    1993-01-01

    Damper spring reduces deflections of omega-cross-section seal, reducing probability of failure and extending life of seal. Spring is split ring with U-shaped cross section. Placed inside omega seal and inserted with seal into seal cavity. As omega seal compressed into cavity, spring and seal make contact near convolution of seal, and spring becomes compressed also. During operation, when seal dynamically loaded, spring limits deflection of seal, reducing stress on seal.

  16. A new adaptive hybrid electromagnetic damper: modelling, optimization, and experiment

    NASA Astrophysics Data System (ADS)

    Asadi, Ehsan; Ribeiro, Roberto; Behrad Khamesee, Mir; Khajepour, Amir

    2015-07-01

    This paper presents the development of a new electromagnetic hybrid damper which provides regenerative adaptive damping force for various applications. Recently, the introduction of electromagnetic technologies to the damping systems has provided researchers with new opportunities for the realization of adaptive semi-active damping systems with the added benefit of energy recovery. In this research, a hybrid electromagnetic damper is proposed. The hybrid damper is configured to operate with viscous and electromagnetic subsystems. The viscous medium provides a bias and fail-safe damping force while the electromagnetic component adds adaptability and the capacity for regeneration to the hybrid design. The electromagnetic component is modeled and analyzed using analytical (lumped equivalent magnetic circuit) and electromagnetic finite element method (FEM) (COMSOL® software package) approaches. By implementing both modeling approaches, an optimization for the geometric aspects of the electromagnetic subsystem is obtained. Based on the proposed electromagnetic hybrid damping concept and the preliminary optimization solution, a prototype is designed and fabricated. A good agreement is observed between the experimental and FEM results for the magnetic field distribution and electromagnetic damping forces. These results validate the accuracy of the modeling approach and the preliminary optimization solution. An analytical model is also presented for viscous damping force, and is compared with experimental results The results show that the damper is able to produce damping coefficients of 1300 and 0-238 N s m-1 through the viscous and electromagnetic components, respectively.

  17. Simple Activity Demonstrates Wind Energy Principles

    ERIC Educational Resources Information Center

    Roman, Harry T.

    2012-01-01

    Wind energy is an exciting and clean energy option often described as the fastest-growing energy system on the planet. With some simple materials, teachers can easily demonstrate its key principles in their classroom. (Contains 1 figure and 2 tables.)

  18. Active Power Controls from Wind Power: Bridging the Gaps

    SciTech Connect

    Ela, E.; Gevorgian, V.; Fleming, P.; Zhang, Y. C.; Singh, M.; Muljadi, E.; Scholbrook, A.; Aho, J.; Buckspan, A.; Pao, L.; Singhvi, V.; Tuohy, A.; Pourbeik, P.; Brooks, D.; Bhatt, N.

    2014-01-01

    This paper details a comprehensive study undertaken by the National Renewable Energy Laboratory, Electric Power Research Institute, and the University of Colorado to understand how the contribution of wind power providing active power control (APC) can benefit the total power system economics, increase revenue streams, improve the reliability and security of the power system, and provide superior and efficient response while reducing any structural and loading impacts that may reduce the life of the wind turbine or its components. The study includes power system simulations, control simulations, and actual field tests using turbines at NREL's National Wind Technology Center (NWTC). The study focuses on synthetic inertial control, primary frequency control, and automatic generation control, and analyzes timeframes ranging from milliseconds to minutes to the lifetime of wind turbines, locational scope ranging from components of turbines to large wind plants to entire synchronous interconnections, and additional topics ranging from economics to power system engineering to control design.

  19. The Tevatron bunch by bunch longitudinal dampers

    SciTech Connect

    Cheng-Yang Tan and James Steimel

    2002-09-25

    We describe in this paper the Tevatron bunch by bunch dampers. The goal of the dampers is to stop the spontaneous longitudinal beam size blowup of the protons during a store. We will go through the theory and also show the measured results during the commissioning of this system. The system is currently operational and have stopped the beam blowups during a store.

  20. Damper mechanism for nuclear reactor control elements

    DOEpatents

    Taft, William Elwood

    1976-01-01

    A damper mechanism which provides a nuclear reactor control element decelerating function at the end of the scram stroke. The total damping function is produced by the combination of two assemblies, which operate in sequence. First, a tapered dashram assembly decelerates the control element to a lower velocity, after which a spring hydraulic damper assembly takes over to complete the final damping.

  1. Semi-active vibration control in cable-stayed bridges under the condition of random wind load

    NASA Astrophysics Data System (ADS)

    Heo, G.; Joonryong, Jeon

    2014-07-01

    This paper aims at an experimental study on the real-time vibration control of bridge structures using a semi-active vibration control method that has been in the spotlight recently. As structures are becoming larger and larger, structural harmful vibration caused by unspecified external forces such as earthquakes, gusts of wind, and collisions has been brought to attention as an important issue. These harmful vibrations can cause not only user anxiety but also severe structural damage or even complete failure of structures. Therefore, in view of structural safety and economical long-term maintenance, real-time control technology of the harmful structural vibration is urgently required. In this paper, a laboratory-scale model of a cable-stayed bridge was built, and a shear-type MR damper and a semi-active vibration control algorithm (Lyapunov and clipped optimal) were applied for the control of harmful vibration of the model bridge, in real time. On the basis of the test results, each semi-active control algorithm was verified quantitatively.

  2. Counterspin nutation damper analysis and design

    NASA Astrophysics Data System (ADS)

    Clements, R. R.; Reece, G. J.; Tonkin, S. W.; Wright, J. H.

    1982-08-01

    A suitable counterspun nutation damping system was designed for IRIS, a combined spacecraft destined for geostationary orbit, and the perigee motor to put it into orbit after shuttle launch. A procedure is described for choosing a damper size, together with the number required, for any vehicle. For IRIS it is shown that two dampers, each with an angular momentum of 5 Nms, are sufficient, and that performance is adequate if one damper fails. Each damper would weigh just under 3 kg and require about 0.5 kg of batteries. The system can be operated immediately on ejection from the shuttle. Extensive computer simulations of damper performances show close agreement with predictions (for restricted cases) and reveal the effects of non-axisymmetry of the spacecraft, drive axle misalignment and Coulomb friction in the bearings.

  3. Galactic Winds in Galaxies with Active Black Holes

    NASA Astrophysics Data System (ADS)

    Lee, Lin; Yesuf, Hassen Mohammed

    2017-01-01

    Post-starbursts galaxies are in a rapid transition from star-forming to quiescent, and are excellent candidates to test Active galactic nuclei (AGN) feedback models. A key physical manifestation of AGN feedback is predicted to be galactic-scale powerful winds. We study winds in stacked spectra of 375 post-starburst AGN and of a control sample of star-forming (non-AGN) galaxies, both taken from the Sloan Digital Sky Survey (SDSS). Using a two component (ISM+wind) absorption line model of the Na I 5890,5896 A doublet, after accounting for the stellar photospheric absorption, we find that the post-starburst AGN have a centroid wind velocity shift of -174 +/- 24 km/s and a wind velocity dispersion of 148 +/- 10 km/s. In comparison, the control sample, matched in redshift, stellar mass, axis-ratio, and the 4000 angstrom break index, has a centroid wind velocity shift of -132 +/- 7 km/s and a wind velocity dispersion of 86 +/- 5 km/s. The equivalent widths due to the winds are slightly higher in post-starburst AGN (0.25 +/- 0.03 A) than in the control sample (0.14 +/- 0.01 A) while the ISM contribution to the total equivalent widths is much higher in the AGN (0.62 +/- 0.05 A) than in the control sample (0.15 +/- 0.01 A). The observed winds in the post-starburst AGN are not powerful enough to sweep significant amount gas out of the halos of the host galaxies, thereby cause rapid and permanent quenching of star-formation.

  4. Experimental study of a self-powered and sensing MR-damper-based vibration control system

    NASA Astrophysics Data System (ADS)

    Sapiński, Bogdan

    2011-10-01

    The paper deals with a semi-active vibration control system based on a magnetorheological (MR) damper. The study outlines the model and the structure of the system, and describes its experimental investigation. The conceptual design of this system involves harvesting energy from structural vibrations using an energy extractor based on an electromagnetic transduction mechanism (Faraday's law). The system consists of an electromagnetic induction device (EMI) prototype and an MR damper of RD-1005 series manufactured by Lord Corporation. The energy extracted is applied to control the damping characteristics of the MR damper. The model of the system was used to prove that the proposed vibration control system is feasible. The system was realized in the semi-active control strategy with energy recovery and examined through experiments in the cases where the control coil of the MR damper was voltage-supplied directly from the EMI or voltage-supplied via the rectifier, or supplied with a current control system with two feedback loops. The external loop used the sky-hook algorithm whilst the internal loop used the algorithm switching the photorelay, at the output from the rectifier. Experimental results of the proposed vibration control system were compared with those obtained for the passive system (MR damper is off-state) and for the system with an external power source (conventional system) when the control coil of the MR damper was supplied by a DC power supply and analogue voltage amplifier or a DC power supply and a photorelay. It was demonstrated that the system is able to power-supply the MR damper and can adjust itself to structural vibrations. It was also found that, since the signal of induced voltage from the EMI agrees well with that of the relative velocity signal across the damper, the device can act as a 'velocity-sign' sensor.

  5. Dynamic performance of a disk-type magnetorheological fluid damper under AC excitation

    NASA Astrophysics Data System (ADS)

    Zhu, Changsheng

    2005-02-01

    It is shown that the dynamic behaviour of a disk-type magnetorheological (MR) fluid damper developed on shear mode for rotational machinery can be controlled by application of an external DC magnetic field produced by a low voltage electromagnetic coil and that the disk-type MR fluid damper can effectively attenuate the rotor vibration. In this paper, the dynamic behaviour of the disk-type MR fluid damper for attenuating rotor vibration under AC sinusoidal magnetic field is experimentally studied on a flexible rotor. It is shown that as the frequency of applied AC sinusoidal magnetic field increases, the capability of the disk-type MR fluid damper to attenuate rotor vibration significantly reduces. There is a maximum frequency of AC sinusoidal magnetic field for a given applied magnetic field strength to realize the MR effect. When the frequency of AC sinusoidal magnetic field is over the maximum frequency, the MR activity almost completely disappears and the dynamic behaviour of the disk-type MR fluid dampers under a high frequency AC magnetic field is the same as that without magnetic field. For a given sinusoidal magnetic field frequency, there is also a minimum AC sinusoidal magnetic field to active the MR effect. In the rotor vibration control of view, it is not necessary to use the AC power supply for disk-type MR fluid dampers.

  6. Dynamic response time of a metal foam magneto-rheological damper

    NASA Astrophysics Data System (ADS)

    Yan, Yao X.; Hui, Liu X.; M, Yu; J, Fu; Dong, Liao H.

    2013-02-01

    Magneto-rheological (MR) dampers are a promising type of semi-active control device for various dynamic systems. Recently, low-cost MR dampers without any sealing structure have been required. Motivated by the desire to overcome the need for the costly dynamic seals of conventional MR dampers, a new type of metal foam MR damper is proposed in this study and the dynamic response performance is also investigated. The metal foam is firmly adhered to a working cylinder to store the unexcited MR fluids. In the action of a magnetic field, MR fluids will be extracted from the metal foam and fill up the shear gap to produce the MR effect. Three time parameters related to response time are introduced to further describe the dynamic response process. The results show that, due to the period required for extracting the MR fluids out from the metal foam, the time to produce the damper force of the metal foam MR damper is longer than for conventional fluid-filled MR dampers. The response time of the metal foam MR damper will change with different currents and shear rates. Given a constant shear rate, in a small range of currents (0-1.5 A), the response time decreases rapidly as the operating current increases; however, there is a slower change rate in larger ranges. To evaluate the effect of shear rate on response time, shear rates ranging from 2 to 10 s-1 are tested, and the results demonstrate that with increasing shear rates the response time decreases.

  7. Experimental analysis of large capacity MR dampers with short- and long-stroke

    NASA Astrophysics Data System (ADS)

    Zemp, René; de la Llera, Juan Carlos; Weber, Felix

    2014-12-01

    The purpose of this article is to study and characterize experimentally two magneto-rheological dampers with short- and long-stroke, denoted hereafter as MRD-S and MRD-L. The latter was designed to improve the Earthquake performance of a 21-story reinforced concrete building equipped with two 160 ton tuned pendular masses. The MRD-L has a nominal force capacity of 300 kN and a stroke of ±1 m; the MRD-S has a nominal force capacity of 150 kN, and a stroke of ±0.1 m. The MRD-S was tested with two different magneto-rheological and one viscous fluid. Due to the presence of Eddy currents, both dampers show a time lag between current intensity and damper force as the magnetization on the damper changes in time. Experimental results from the MRD-L show a force drop-off behavior. A decrease in active-mode forces due to temperature increase is also analyzed for the MRD-S and the different fluids. Moreover, the observed increase in internal damper pressure due to energy dissipation is evaluated for the different fluids in both dampers. An analytical model to predict internal pressure increase in the damper is proposed that includes as a parameter the concentration of magnetic particles inside the fluid. Analytical dynamic pressure results are validated using the experimental tests. Finally, an extended Bingham fluid model, which considers compressibility of the fluid, is also proposed and validated using damper tests.

  8. Cast XD{trademark} gamma titanium aluminide turbine blade dampers

    SciTech Connect

    Pettersson, B.; Axelsson, P.; Andersson, M.; Holmquist, M.

    1995-12-31

    This paper presents results from engine testing of cast XD{trademark} gamma titanium aluminide turbine blade dampers. The dampers were manufactured from the XD{trademark} gamma alloy Ti-47Al-2Nb-2Mn + 0.8vol%TiB{sub 2} using investment casting. In the engine tests reported here the new low weight titanium aluminide dampers replaced the original Ni-base superalloy dampers and the titanium aluminide dampers ability to reduce HPT-blade dynamic stresses at different excitation levels was measured. The results showed that the new damper could reduce the blade dynamic stresses with up to 50% at lower excitations. At higher excitation levels the new gamma dampers showed no improvement over Ni-dampers. To qualify the new damper for engine use endurance tests were run for a total accumulated time of 214 hours. Blades and dampers were inspected after endurance testing and the friction surfaces on blades and dampers showed only normal signs of wear while unacceptable wear marks caused by the gamma damper appeared at the contact points between blade and damper on the blade root neck. The overall appearance of the dampers was still good. They were slightly oxidized but had otherwise only normal signs of wear. Changes of the gamma dampers geometry are believed to have potential to both improve their damping characteristics at high excitation levels as well as to reduce the wear problems.

  9. Waveguide harmonic damper for klystron amplifier.

    SciTech Connect

    Kang, Y.

    1998-10-27

    A waveguide harmonic damper was designed for removing the harmonic frequency power from the klystron amplifiers of the APS linac. Straight coaxial probe antennas are used in a rectangular waveguide to form a damper. A linear array of the probe antennas is used on a narrow wall of the rectangular waveguide for damping klystron harmonics while decoupling the fundamental frequency in dominent TE{sub 01} mode. The klystron harmonics can exist in the waveguide as waveguide higher-order modes above cutoff. Computer simulations are made to investigate the waveguide harmonic damping characteristics of the damper.

  10. Digital control system for space structural dampers

    NASA Technical Reports Server (NTRS)

    Haviland, J. K.

    1984-01-01

    A recently developed concept for a damper was improved by adding a small taper to the proof-mass, and using a proximeter to determine position. Also, an experimental damper was built using a three-inch stroke in place of the standard one-inch stroke. The analog controller initially used was replaced by an independent digital controller slaved to a TRS-80 Model I computer, which also serves as a highly effective, low-cost development system. An overall system concept for the use of proof-mass dampers is presented.

  11. Analysis of Train Suspension System Using MR dampers

    NASA Astrophysics Data System (ADS)

    RamaSastry, DVA; Ramana, K. V.; Mohan Rao, N.; Siva Kumar, SVR; Priyanka, T. G. L.

    2016-09-01

    This paper deals with introducing MR dampers to the Train Suspension System for improving the ride comfort of the passengers. This type of suspension system comes under Semi-active suspension system which utilizes the properties of MR fluid to damp the vibrations. In case of high speed trains, the coach body is subjected to vibrations due to vertical displacement, yaw and pitch movements. When the body receives these disturbances from the ground,the transmission of vibrations to the passenger increases which affect the ride comfort. In this work, the equations of motion of suspension system are developed for both conventional passive system and semi-active system and are modelled in Matlab/Simulink and analysis has been carried out. The passive suspension system analysis shows that it is taking more time to damp the vibrations and at the same time the transmissibility of vibrations is more.Introducing MR dampers,vertical and angular displacements of the body are computed and compared. The results show that the introduction of MR dampers into the train suspension system improves ride comfort.

  12. Wind in the Willows--Theatre Activity Packet.

    ERIC Educational Resources Information Center

    New York City Board of Education, Brooklyn, NY. Div. of Curriculum and Instruction.

    Part of the New York City Board of Education's Early Stages program, and intended for elementary and secondary school teachers who wish to include a unit on theater in their classes, this guide offers suggestions for lessons and activities to accompany viewing a performance of "Wind in the Willows" at the Nederlander Theater. Part one of…

  13. Fermilab Recycler damper requirements and design

    SciTech Connect

    Crisp, J.; Hu, M.; Tupikov, V.; /Fermilab

    2005-05-01

    The design of transverse dampers for the Fermilab Recycler storage ring is described. An observed instability and analysis of subsequent measurements where used to identify the requirements. The digital approach being implemented is presented.

  14. Squeeze-film dampers for turbomachinery stabilization

    NASA Technical Reports Server (NTRS)

    Mclean, L. J.; Hahn, E. J.

    1984-01-01

    A technique for investigating the stability and damping present in centrally preloaded radially symmetric multi-mass flexible rotor bearing systems is presented. In general, one needs to find the eigenvalues of the linearized perturbation equations, though zero frequency stability maps may be found by solving as many simultaneous non-linear equations as there are dampers; and in the case of a single damper, such maps may be found directly, regardless of the number of degrees of freedom. The technique is illustrated for a simple symmetric four degree of freedom flexible rotor with an unpressurized damper. This example shows that whereas zero frequency stability maps are likely to prove to be a simple way to delineate multiple solution possibilities, they do not provide full stability information. Further, particularly for low bearing parameters, the introduction of an unpressurized squeeze film damper may promote instability in an otherwise stable system.

  15. Dampers for Natural Draft Heaters: Technical Report

    SciTech Connect

    Lutz, James D.; Biermayer, Peter; King, Derek

    2008-10-27

    Energy required for water heating accounts for approximately 40percent of national residential natural gas consumption in California. With water heating contributing such a substantial portion of natural gas consumption, it is important to pay attention to water heater efficiencies. This paper reports on an investigation of a patented, buoyancy-operated flue damper. It is an add-on design to a standard atmospherically vented natural-draft gas-fired storage water heater. The flue damper was expected to reduce off-cycle standby losses, which would lead to improvements in the efficiency of the water heater. The test results showed that the Energy Factor of the baseline water heater was 0.576. The recovery efficiency was 0.768. The standby heat loss coefficient was 10.619 (BTU/hr-oF). After the damper was installed, the test results show an Energy Factor for the baseline water heater of 0.605. The recovery efficiency was 0.786. The standby heat loss coefficient was 9.135 (BTU/hr-oF). The recovery efficiency increased 2.3percent and the standby heat loss coefficient decreased 14percent. When the burner was on, the baseline water heater caused 28.0 CFM of air to flow from the room. During standby, the flow was 12.4 CFM. The addition of the damper reduced the flow when the burner was on to 23.5 CFM. During standby, flow with the damper was reduced to 11.1 CFM. The flue damper reduced off-cycle standby losses, and improved the efficiency of the water heater. The flue damper also improved the recovery efficiency of the water heater by restricting on-cycle air flows through the flue.With or without the flue damper, off-cycle air flow upthe stack is nearly half the air flow rate as when the burner is firing.

  16. SHM of wind turbine blades using piezoelectric active-sensors

    SciTech Connect

    Park, Gyuhae; Taylor, Stuart G; Farinholt, Kevin M; Farrar, Charles R

    2010-01-01

    This paper presents a variety of structural health monitoring (SHM) techniques, based on the use of piezoelectric active-sensors, used to determine the structural integrity of wind turbine blades. Specifically, Lamb wave propagations, frequency response functions, and time series based methods are utilized to estimate the condition of wind turbine blades. For experiments, a 1m section of a 9m CX100 blade is used. Overall, these three methods yielded a sufficient damage detection capability to warrant further investigation into field deployment. A full-scale fatigue test of a CX-100 wind turbine blade is also conducted. This paper summarizes considerations needed to design such SHM systems, experimental procedures and results, and practical implementation issues that can be used as guidelines for future investigations.

  17. Structural vibration control by tuned mass damper using central pattern generator

    NASA Astrophysics Data System (ADS)

    Iba, Daisuke; Hongu, Junichi

    2011-04-01

    This paper proposes a new control method for active mass dampers using a Central Pattern Generator in vibration mitigation. The active mass dampers (or active dynamic absorbers) have been applied to structural vibration control of high-rise buildings, bridges and so on. In this case, the mass of the active mass damper must oscillate in an appropriate phase in relation to the control object, and generally, the damper has been designed by linear control theory as pole placement method, optimal control method or H infinity control method, and all the rest. On the other hand, on walking of animate beings like mammals or insects, both side feet have appropriate phase relations; moreover, it is possible to keep moving on irregular ground. That is, algorithms for the walking would be embedded into the animate beings to control the complicated and redundant bodies with ease and robustness. In biological study, the Central Pattern Generators in bodies playing a significant role in the walking have been learned over the last few decades, and some studies said that some animate beings are able to control their feet by using the generators without their brains in the walking. Moreover, mathematical models of the pattern generators have been proposed, and some researchers have been studying to realize walking of biped-robots using the pattern generators embedded in a computer. In this study, the algorithm is installed into a controller for the active mass damper; furthermore, validation of the controller is performed by numerical simulation.

  18. Free vibration analysis of linear particle chain impact damper

    NASA Astrophysics Data System (ADS)

    Gharib, Mohamed; Ghani, Saud

    2013-11-01

    Impact dampers have gained much research interest over the past decades that resulted in several analytical and experimental studies being conducted in that area. The main emphasis of such research was on developing and enhancing these popular passive control devices with an objective of decreasing the three parameters of contact forces, accelerations, and noise levels. To that end, the authors of this paper have developed a novel impact damper, called the Linear Particle Chain (LPC) impact damper, which mainly consists of a linear chain of spherical balls of varying sizes. The LPC impact damper was designed utilizing the kinetic energy of the primary system through placing, in the chain arrangement, a small-sized ball between each two large-sized balls. The concept of the LPC impact damper revolves around causing the small-sized ball to collide multiple times with the larger ones upon exciting the primary system. This action is believed to lead to the dissipation of part of the kinetic energy at each collision with the large balls. This paper focuses on the outcome of studying the free vibration of a single degree freedom system that is equipped with the LPC impact damper. The proposed LPC impact damper is validated by means of comparing the responses of a single unit conventional impact damper with those resulting from the LPC impact damper. The results indicated that the latter is considerably more efficient than the former impact damper. In order to further investigate the LPC impact damper effective number of balls and efficient geometry when used in a specific available space in the primary system, a parametric study was conducted and its result is also explained herein. Single unit impact damper [14-16]. Multiunit impact damper [17,18]. Bean bag impact damper [19,20]. Particle/granular impact damper [21,23,22]. Resilient impact damper [24]. Buffered impact damper [25-27]. Multiunit impact damper consists of multiple masses instead of a single mass. This

  19. Impact of active and break wind spells on the demand-supply balance in wind energy in India

    NASA Astrophysics Data System (ADS)

    Kulkarni, Sumeet; Deo, M. C.; Ghosh, Subimal

    2017-01-01

    With an installed capacity of over 19,000 MW, the wind power currently accounts for almost 70% of the total installed capacity among the renewable energy sector in India. The extraction of wind power mainly depends on prevailing meteorology which is strongly influenced by monsoon variability. The monsoon season is characterized by significant fluctuations in between periods of wet and dry spells. During the dry spells, the demand for power from agriculture and cooling equipment increases, whereas during the wet periods, such demand reduces, although, at the same time, the power supply increases because of strong westerly winds contributing to an enhanced production of wind energy. At this backdrop, we aim to assess the impact of intra-seasonal wind variability on the balance of energy supply and demand during monsoon seasons in India. Further, we explore the probable cause of wind variability by relating it to El Nino events. It is observed that the active and break phases in wind significantly impact the overall wind potential output. Although the dry spells are generally found to reduce the overall wind potential, their impact on the potential seems to have declined after the year 2000. The impact of meteorological changes on variations in wind power studied in this work should find applications typically in taking investment decisions on conventional generation facilities, like thermal, which are currently used to maintain the balance of power supply and demand.

  20. Dusty Winds in Active Galactic Nuclei: Reconciling Observations with Models

    NASA Astrophysics Data System (ADS)

    Hönig, Sebastian F.; Kishimoto, Makoto

    2017-04-01

    This Letter presents a revised radiative transfer model for the infrared (IR) emission of active galactic nuclei (AGNs). While current models assume that the IR is emitted from a dusty torus in the equatorial plane of the AGNs, spatially resolved observations indicate that the majority of the IR emission from ≲100 pc in many AGNs originates from the polar region, contradicting classical torus models. The new model CAT3D-WIND builds upon the suggestion that the dusty gas around the AGNs consists of an inflowing disk and an outflowing wind. Here, it is demonstrated that (1) such disk+wind models cover overall a similar parameter range of observed spectral features in the IR as classical clumpy torus models, e.g., the silicate feature strengths and mid-IR spectral slopes, (2) they reproduce the 3–5 μm bump observed in many type 1 AGNs unlike torus models, and (3) they are able to explain polar emission features seen in IR interferometry, even for type 1 AGNs at relatively low inclination, as demonstrated for NGC3783. These characteristics make it possible to reconcile radiative transfer models with observations and provide further evidence of a two-component parsec-scale dusty medium around AGNs: the disk gives rise to the 3–5 μm near-IR component, while the wind produces the mid-IR emission. The model SEDs will be made available for download.

  1. Wind Tunnel Test of the SMART Active Flap Rotor

    NASA Technical Reports Server (NTRS)

    Straub, Friedrich K.; Anand, Vaidyanthan R.; Birchette, Terrence S.; Lau, Benton H.

    2009-01-01

    Boeing and a team from Air Force, NASA, Army, DARPA, MIT, UCLA, and U. of Maryland have successfully completed a wind-tunnel test of the smart material actuated rotor technology (SMART) rotor in the 40- by 80-foot wind-tunnel of the National Full-Scale Aerodynamic Complex at NASA Ames Research Center. The Boeing SMART rotor is a full-scale, five-bladed bearingless MD 900 helicopter rotor modified with a piezoelectric-actuated trailing edge flap on each blade. The eleven-week test program evaluated the forward flight characteristics of the active-flap rotor at speeds up to 155 knots, gathered data to validate state-of-the-art codes for rotor aero-acoustic analysis, and quantified the effects of open and closed loop active flap control on rotor loads, noise, and performance. The test demonstrated on-blade smart material control of flaps on a full-scale rotor for the first time in a wind tunnel. The effectiveness of the active flap control on noise and vibration was conclusively demonstrated. Results showed significant reductions up to 6dB in blade-vortex-interaction and in-plane noise, as well as reductions in vibratory hub loads up to 80%. Trailing-edge flap deflections were controlled within 0.1 degrees of the commanded value. The impact of the active flap on control power, rotor smoothing, and performance was also demonstrated. Finally, the reliability of the flap actuation system was successfully proven in more than 60 hours of wind-tunnel testing.

  2. Martian wind activity detected by a seismometer at Viking lander 2 site

    NASA Technical Reports Server (NTRS)

    Nakamura, Y.; Anderson, D. L.

    1979-01-01

    Since the Viking lander 2 seismometer (Anderson et al., 1977) located on top of the lander is extremely sensitive to Martian winds, it can provide a record of Martian wind activity. The seismograph continuously samples the wind-induced lander vibration, and its output complements meteorological data. Some pertinent seismic data are presented along with results of a preliminary spectral analysis of the data. Attention is given to wind speed/seismic noise correlation, and to long-term variation and periodicity. The results indicate that wind variations on Mars are very regular in the summer and winter seasons. Winds are light in summer and exhibit a strong diurnal periodicity, the strongest winds occurring in the early afternoon. Winds become stronger and more irregular in autumn. In all seasons nighttime conditions are usually very quiet. The high wind season correlates with the global dust storm duration. Spring is characterized by very strong though variable wind activity. Other details are also presented.

  3. Robust control of seismically excited cable stayed bridges with MR dampers

    NASA Astrophysics Data System (ADS)

    YeganehFallah, Arash; Khajeh Ahamd Attari, Nader

    2017-03-01

    In recent decades active and semi-active structural control are becoming attractive alternatives for enhancing performance of civil infrastructures subjected to seismic and winds loads. However, in order to have reliable active and semi-active control, there is a need to include information of uncertainties in design of the controller. In real world for civil structures, parameters such as loading places, stiffness, mass and damping are time variant and uncertain. These uncertainties in many cases model as parametric uncertainties. The motivation of this research is to design a robust controller for attenuating the vibrational responses of civil infrastructures, regarding their dynamical uncertainties. Uncertainties in structural dynamic’s parameters are modeled as affine uncertainties in state space modeling. These uncertainties are decoupled from the system through Linear Fractional Transformation (LFT) and are assumed to be unknown input to the system but norm bounded. The robust H ∞ controller is designed for the decoupled system to regulate the evaluation outputs and it is robust to effects of uncertainties, disturbance and sensors noise. The cable stayed bridge benchmark which is equipped with MR damper is considered for the numerical simulation. The simulated results show that the proposed robust controller can effectively mitigate undesired uncertainties effects on systems’ responds under seismic loading.

  4. Wind Tunnel Testing of Microtabs and Microjets for Active Load Control of Wind Turbine Blades

    NASA Astrophysics Data System (ADS)

    Cooperman, Aubryn Murray

    Increases in wind turbine size have made controlling loads on the blades an important consideration for future turbine designs. One approach that could reduce extreme loads and minimize load variation is to incorporate active control devices into the blades that are able to change the aerodynamic forces acting on the turbine. A wind tunnel model has been constructed to allow testing of different active aerodynamic load control devices. Two such devices have been tested in the UC Davis Aeronautical Wind Tunnel: microtabs and microjets. Microtabs are small surfaces oriented perpendicular to an airfoil surface that can be deployed and retracted to alter the lift coefficient of the airfoil. Microjets produce similar effects using air blown perpendicular to the airfoil surface. Results are presented here for both static and dynamic performance of the two devices. Microtabs, located at 95% chord on the lower surface and 90% chord on the upper surface, with a height of 1% chord, produce a change in the lift coefficient of 0.18, increasing lift when deployed on the lower surface and decreasing lift when deployed on the upper surface. Microjets with a momentum coefficient of 0.006 at the same locations produce a change in the lift coefficient of 0.19. The activation time for both devices is less than 0.3 s, which is rapid compared to typical gust rise times. The potential of active device to mitigate changes in loads was tested using simulated gusts. The gusts were produced in the wind tunnel by accelerating the test section air speed at rates of up to 7 ft/s 2. Open-loop control of microtabs was tested in two modes: simultaneous and sequential tab deployment. Activating all tabs along the model span simultaneously was found to produce a change in the loads that occurred more rapidly than a gust. Sequential tab deployment more closely matched the rates of change due to gusts and tab deployment. A closed-loop control system was developed for the microtabs using a simple

  5. Nuclear winds and the narrow-line emission from active galaxies

    NASA Technical Reports Server (NTRS)

    Smith, Steven J.

    1993-01-01

    This paper discusses active galaxy narrow-line emission in the context of a supersonic wind generated by the active nucleus, a nuclear wind. Wind acceleration can naturally produce the inferred narrow-line cloud velocities as well as those of the broad-line and broad absorption line clouds with only a weak dependence on the parameters of the active nucleus. The primary obstacle to wind acceleration of emission-line clouds is the destructive effect of instabilities; however, the stability and structure of wind-confined clouds remain areas of future research. Observations, particularly of the Seyfert galaxy NGC 1068, are interpreted in the context of nuclear winds.

  6. Analytical and experimental investigation on a multiple-mass-element pendulum impact damper for vibration mitigation

    NASA Astrophysics Data System (ADS)

    Egger, Philipp; Caracoglia, Luca

    2015-09-01

    Impact dampers are often used in the field of civil, mechanical and aerospace engineering for reducing structural vibrations. The behavior of this type of passive control device has been investigated for several decades. In this research a distributed-mass impact damper, similar to the "chain damper" used in wind engineering, has been examined and applied to the vibration reduction on a slender line-like structural element (stay-cable). This study is motivated by a practical problem and describes the derivation of a reduced-order model for explaining the behavior, observed during a field experiment on a prototype system. In its simplest form, the dynamics of the apparatus is modeled as a "resilient damper", composed of mass-spring-dashpot secondary elements, attached to the primary structure. Various sources of excitation are analyzed: free vibration, external harmonic force and random excitation. The proposed model is general and potentially applicable to the analysis of several structural systems. The study also shows that the model can adequately describe and explain the experimentally observed behavior.

  7. The physics of galactic winds driven by active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Faucher-Giguère, Claude-André; Quataert, Eliot

    2012-09-01

    Active galactic nuclei (AGN) drive fast winds in the interstellar medium of their host galaxies. It is commonly assumed that the high ambient densities and intense radiation fields in galactic nuclei imply short cooling times, thus making the outflows momentum conserving. We show that cooling of high-velocity shocked winds in AGN is in fact inefficient in a wide range of circumstances, including conditions relevant to ultraluminous infrared galaxies (ULIRGs), resulting in energy-conserving outflows. We further show that fast energy-conserving outflows can tolerate a large amount of mixing with cooler gas before radiative losses become important. For winds with initial velocity vin ≳ 10 000 km s-1, as observed in ultraviolet and X-ray absorption, the shocked wind develops a two-temperature structure. While most of the thermal pressure support is provided by the protons, the cooling processes operate directly only on the electrons. This significantly slows down inverse Compton cooling, while free-free cooling is negligible. Slower winds with vin ˜ 1000 km s-1, such as may be driven by radiation pressure on dust, can also experience energy-conserving phases but under more restrictive conditions. During the energy-conserving phase, the momentum flux of an outflow is boosted by a factor ˜vin/2vs by work done by the hot post-shock gas, where vs is the velocity of the swept-up material. Energy-conserving outflows driven by fast AGN winds (vin ˜ 0.1c) may therefore explain the momentum fluxes Ṗ≫LAGN/c of galaxy-scale outflows recently measured in luminous quasars and ULIRGs. Shocked wind bubbles expanding normal to galactic discs may also explain the large-scale bipolar structures observed in some systems, including around the Galactic Centre, and can produce significant radio, X-ray and γ-ray emission. The analytic solutions presented here will inform implementations of AGN feedback in numerical simulations, which typically do not include all the important

  8. 46 CFR 78.47-53 - Automatic ventilation dampers.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 3 2010-10-01 2010-10-01 false Automatic ventilation dampers. 78.47-53 Section 78.47-53... Fire and Emergency Equipment, Etc. § 78.47-53 Automatic ventilation dampers. (a) The manual operating positions for automatic fire dampers in ventilation ducts passing through main vertical zone bulkheads...

  9. 46 CFR 78.47-53 - Automatic ventilation dampers.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 3 2013-10-01 2013-10-01 false Automatic ventilation dampers. 78.47-53 Section 78.47-53... Fire and Emergency Equipment, Etc. § 78.47-53 Automatic ventilation dampers. (a) The manual operating positions for automatic fire dampers in ventilation ducts passing through main vertical zone bulkheads...

  10. 46 CFR 78.47-53 - Automatic ventilation dampers.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 3 2011-10-01 2011-10-01 false Automatic ventilation dampers. 78.47-53 Section 78.47-53... Fire and Emergency Equipment, Etc. § 78.47-53 Automatic ventilation dampers. (a) The manual operating positions for automatic fire dampers in ventilation ducts passing through main vertical zone bulkheads...

  11. 46 CFR 78.47-53 - Automatic ventilation dampers.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 3 2014-10-01 2014-10-01 false Automatic ventilation dampers. 78.47-53 Section 78.47-53... Fire and Emergency Equipment, Etc. § 78.47-53 Automatic ventilation dampers. (a) The manual operating positions for automatic fire dampers in ventilation ducts passing through main vertical zone bulkheads...

  12. 46 CFR 78.47-53 - Automatic ventilation dampers.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 3 2012-10-01 2012-10-01 false Automatic ventilation dampers. 78.47-53 Section 78.47-53... Fire and Emergency Equipment, Etc. § 78.47-53 Automatic ventilation dampers. (a) The manual operating positions for automatic fire dampers in ventilation ducts passing through main vertical zone bulkheads...

  13. Experimental study of uncentralized squeeze film dampers

    NASA Technical Reports Server (NTRS)

    Quinn, R. D.

    1983-01-01

    The vibration response of a rotor system supported by a squeeze film damper (SFD) was experimentally investigated in order to provide experimental data in support of the Rotor/Stator Interactive Finite Element theoretical development. Part of the investigation required the designing and building of a rotor/SFD system that could operate with or without end seals in order to accommodate different SFD lengths. SFD variables investigated included clearance, eccentricity mass, fluid pressure, and viscosity and temperature. The results show inlet pressure, viscosity and clearance have significant influence on the damper performance and accompanying rotor response.

  14. Optimal Design of Damper Layer for Static Elastography

    NASA Astrophysics Data System (ADS)

    Sato, Takayuki; Watanabe, Yasuaki; Sekimoto, Hitoshi

    2012-07-01

    An effective method in static elastography for improving the nonuniformity of stress applied by the shape of a transducer head is to insert a damper between the tissue being analyzed and the transducer head. We previously demonstrated the effectiveness of inserting a damper through computer simulations of structural and acoustic analyses on tissue models with flat surfaces. In this study, the optimal values were obtained for two parameters of the damper: Young's modulus and damper thickness. An effective damper shape was also determined through structural analyses.

  15. Analysis of Diurnal, Planetary and Mean Wind Activity using TIMED, MF and Meteor Radar Winds

    NASA Technical Reports Server (NTRS)

    Lieberman, Ruth S.; Riggin, Dennis R.

    2003-01-01

    The goals of this research are: 1) To validate TIMED Doppler Interferometer (TIDI) winds using ground-based MF and meteor winds; and 2) To examine short-term (i. e., day-to-day and week-to-week) variability of the diurnal tide. This objective was to have originally been met using comparisons of short-term diurnal tidal determinations from ground-based (GB) winds with planetary-scale diurnal nonmigrating tidal definitions from TIDI winds.

  16. Mass-spring-damper modelling of the human body to study running and hopping--an overview.

    PubMed

    Nikooyan, A A; Zadpoor, A A

    2011-12-01

    Several mass-spring-damper models have been developed to study the response of the human body to the collision with the ground during hopping, trotting, or running. The mass, spring, and damper elements represent the masses, stiffness properties, and damping properties of hard and soft tissues. The masses that models are composed of are connected to each other via springs and dampers. The present paper reviews the various types of mass-spring-damper models including one-body and multi-body models. The models are further categorized as being either passive or active. In passive models, the mechanical properties (stiffness and damping) of soft tissues remain constant regardless of the type of footwear, ground stiffness, etc. In active models, the mechanical properties adapt to external loads. The governing equations of motion of all models as well as their parameters are presented. The specific ways that the models take account of the shoe-ground interactions are discussed as well. The methods used for determination of different modelling parameters are briefly surveyed. The advantages and disadvantages of the different types of mass-spring-damper models are also discussed. The paper concludes with a brief discussion of possible future research trends in the area of mass-spring-damper modelling.

  17. Design and modeling of energy generated magneto rheological damper

    NASA Astrophysics Data System (ADS)

    Ahamed, Raju; Rashid, Muhammad Mahbubur; Ferdaus, Md Meftahul; Yusof, Hazlina Md.

    2016-02-01

    In this paper an energy generated mono tube MR damper model has been developed for vehicle suspension systems. A 3D model of energy generated MR damper is developed in Solid Works electromagnetic simulator (EMS) where it is analyzed extensively by finite element method. This dynamic simulation clearly illustrates the power generation ability of the damper. Two magnetic fields are induced inside this damper. One is in the outer coil of the power generator and another is in the piston head coils. The complete magnetic isolation between these two fields is accomplished here, which can be seen in the finite element analysis. The induced magnetic flux densities, magnetic field intensities of this damper are analyzed for characterizing the damper's power generation ability. Finally, the proposed MR damper's energy generation ability was studied experimentally.

  18. The active flexible wing aeroservoelastic wind-tunnel test program

    NASA Technical Reports Server (NTRS)

    Noll, Thomas; Perry, Boyd

    1989-01-01

    For a specific application of aeroservoelastic technology, Rockwell International Corporation developed a concept known as the Active Flexible Wing (AFW). The concept incorporates multiple active leading-and trailing-edge control surfaces with a very flexible wing such that wing shape is varied in an optimum manner resulting in improved performance and reduced weight. As a result of a cooperative program between the AFWAL's Flight Dynamics Laboratory, Rockwell, and NASA LaRC, a scaled aeroelastic wind-tunnel model of an advanced fighter was designed, fabricated, and tested in the NASA LaRC Transonic Dynamics Tunnel (TDT) to validate the AFW concept. Besides conducting the wind-tunnel tests NASA provided a design of an Active Roll Control (ARC) System that was implemented and evaluated during the tests. The ARC system used a concept referred to as Control Law Parameterization which involves maintaining constant performance, robustness, and stability while using different combinations of multiple control surface displacements. Since the ARC system used measured control surface stability derivatives during the design, the predicted performance and stability results correlated very well with test measurements.

  19. Investigation on modeling and controability of a magnetorheological gun recoil damper

    NASA Astrophysics Data System (ADS)

    Hu, Hongsheng; Wang, Juan; Wang, Jiong; Qian, Suxiang; Li, Yancheng

    2009-07-01

    Magnetorheological (MR) fluid as a new smart material has done well in the vibration and impact control engineering fields because of its good electromechanical coupling characteristics, preferable dynamic performance and higher sensitivity. And success of MRF has been apparent in many engineering applied fields, such as semi-active suspension, civil engineering, etc. So far, little research has been done about MR damper applied into the weapon system. Its primary purpose of this study is to identify its dynamic performance and controability of the artillery recoil mechanism equipped with MR damper. Firstly, based on the traditional artillery recoil mechanism, a recoil dynamic model is developed in order to obtain an ideal rule between recoil force and its stroke. Then, its effects of recoil resistance on the stability and firing accuracy of artillery are explored. Because MR gun recoil damper under high impact load shows a typical nonlinear character and there exists a shear-thinning phenomenon, to establish an accurate dynamic model has been a seeking aim of its design and application for MR damper under high impact load. Secondly, in this paper, considering its actual bearing load, an inertia factor was introduced to Herschel-Bulkley model, and some factor's effect on damping force are simulated and analyzed by using numerical simulation, including its dynamic performance under different flow coefficients and input currents. Finally, both of tests with the fixed current and different On-Off control algorithms have been done to confirm its controability of MR gun recoil damper under high impact load. Experimental results show its dynamic performances of the large-scale single-ended MR gun recoil damper can be changed by altering the applied currents and it has a good controllability.

  20. 77 FR 5830 - Commercial Wind Leasing and Site Assessment Activities on the Atlantic Outer Continental Shelf...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-06

    ... Bureau of Ocean Energy Management Commercial Wind Leasing and Site Assessment Activities on the Atlantic... of involving Federal agencies, states, tribes, local governments, offshore wind energy developers, and the public in the Department of the Interior's (DOI) ``Smart from the Start'' wind...

  1. 78 FR 31517 - Notification of Proposed Production Activity; Vestas Nacelles America, Inc.; Subzone 123E (Wind...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-24

    ... Proposed Production Activity; Vestas Nacelles America, Inc.; Subzone 123E (Wind Turbines); Brighton, Denver... wind turbines and related products (nacelles, hubs, blades, and towers) under FTZ procedures using... during customs entry procedures that apply to wind turbines, nacelles, hubs, blades, and towers (free,...

  2. 77 FR 74218 - Commercial Wind Leasing and Site Assessment Activities on the Atlantic Outer Continental Shelf...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-13

    ... identified in the document entitled, Commercial Leasing for Wind Power on the Outer Continental Shelf... Bureau of Ocean Energy Management Commercial Wind Leasing and Site Assessment Activities on the Atlantic... agencies, states, tribes, local governments, offshore wind energy developers, and the public in...

  3. Numerical modeling of pendulum dampers in torsional systems

    SciTech Connect

    Johnston, P.R.; Shusto, L.M.

    1986-01-01

    Centrifugal pendulum-design dampers are utilized in torsional systems to reduce the vibration amplitude at certain objectionable torsional speeds. The damper is tuned by proper design of its mass, dimensions, and position on a carrier disk, which is rigidly attached to the torsional system. The effects of the pendulum damper on the response of the torsional system may be included by modifying the structural model to include a separate damper element representing each order of the pendulum damper. The stiffness and mass matrices for a damper element are dependent upon the order of vibration being dampened, the mass, and the geometry of the damper. A general form of the mass and stiffness equations for a simple centrifugal pendulum damper are derived from first principles using Lagrange's equations of motion. The analysis of torsional systems with pendulum dampers utilizing the mass and stiffness properties developed is included in the program SHAMS. SHAMS calculates the steady-state response of a system of springs and masses to harmonic loads using modal superposition. The response of a crankshaft system with and without the pendulum dampers are included as a case study.

  4. A fully dynamic magneto-rheological fluid damper model

    NASA Astrophysics Data System (ADS)

    Jiang, Z.; Christenson, R. E.

    2012-06-01

    Control devices can be used to dissipate the energy of a civil structure subjected to dynamic loading, thus reducing structural damage and preventing failure. Semiactive control devices have received significant attention in recent years. The magneto-rheological (MR) fluid damper is a promising type of semiactive device for civil structures due to its mechanical simplicity, inherent stability, high dynamic range, large temperature operating range, robust performance, and low power requirements. The MR damper is intrinsically nonlinear and rate-dependent, both as a function of the displacement across the MR damper and the command current being supplied to the MR damper. As such, to develop control algorithms that take maximum advantage of the unique features of the MR damper, accurate models must be developed to describe its behavior for both displacement and current. In this paper, a new MR damper model that includes a model of the pulse-width modulated (PWM) power amplifier providing current to the damper, a proposed model of the time varying inductance of the large-scale 200 kN MR dampers coils and surrounding MR fluid—a dynamic behavior that is not typically modeled—and a hyperbolic tangent model of the controllable force behavior of the MR damper is presented. Validation experimental tests are conducted with two 200 kN large-scale MR dampers located at the Smart Structures Technology Laboratory (SSTL) at the University of Illinois at Urbana-Champaign and the Lehigh University Network for Earthquake Engineering Simulation (NEES) facility. Comparison with experimental test results for both prescribed motion and current and real-time hybrid simulation of semiactive control of the MR damper shows that the proposed MR damper model can accurately predict the fully dynamic behavior of the large-scale 200 kN MR damper.

  5. Computational Fluid Dynamics Simulation Study of Active Power Control in Wind Plants

    SciTech Connect

    Fleming, Paul; Aho, Jake; Gebraad, Pieter; Pao, Lucy; Zhang, Yingchen

    2016-08-01

    This paper presents an analysis performed on a wind plant's ability to provide active power control services using a high-fidelity computational fluid dynamics-based wind plant simulator. This approach allows examination of the impact on wind turbine wake interactions within a wind plant on performance of the wind plant controller. The paper investigates several control methods for improving performance in waked conditions. One method uses wind plant wake controls, an active field of research in which wind turbine control systems are coordinated to account for their wakes, to improve the overall performance. Results demonstrate the challenge of providing active power control in waked conditions but also the potential methods for improving this performance.

  6. Influence of playing wind instruments on activity of masticatory muscles.

    PubMed

    Gotouda, A; Yamaguchi, T; Okada, K; Matsuki, T; Gotouda, S; Inoue, N

    2007-09-01

    The aim of this study was to elucidate the influence of change in sound tone of playing wind instruments on activity of jaw-closing muscles and the effect of sustained playing for a long time on fatigue of jaw-closing muscles. Electromyograms (EMG) of 19 brass instrument players and 14 woodwind instrument players were measured while playing instruments in tuning tone and high tone and under other conditions. Nine brass instrument players and nine woodwind instrument players played instruments for 90 min. Before and after the exercise, power spectral analyses of EMG from masseter muscles at 50% of maximum voluntary clenching level were performed and mean power frequency (MPF) were calculated. Root mean square (RMS) of EMG in masseter and temporal muscles while playing were slightly larger than those at rest but extremely small in comparison with those during maximum clenching. Root mean square in orbicularis oris and digastric muscles were relatively large when playing instruments. In the brass instrument group, RMS in high tone was significantly higher than that in tuning tone in all muscles examined. In the woodwind instrument group, RMS in high tone was not significantly higher than that in tuning tone in those muscles. Mean power frequency was not decreased after sustained playing in both instrument groups. These findings indicate that contractive load to jaw-closing muscles when playing a wind instrument in both medium and high tone is very small and playing an instrument for a long time does not obviously induce fatigue of jaw-closing muscles.

  7. Geomagnetic responses to the solar wind and the solar activity

    NASA Technical Reports Server (NTRS)

    Svalgaard, L.

    1975-01-01

    Following some historical notes, the formation of the magnetosphere and the magnetospheric tail is discussed. The importance of electric fields is stressed and the magnetospheric convection of plasma and magnetic field lines under the influence of large-scale magnetospheric electric fields is outlined. Ionospheric electric fields and currents are intimately related to electric fields and currents in the magnetosphere and the strong coupling between the two regions is discussed. The energy input of the solar wind to the magnetosphere and upper atmosphere is discussed in terms of the reconnection model where interplanetary magnetic field lines merge or connect with the terrestrial field on the sunward side of the magnetosphere. The merged field lines are then stretched behind earth to form the magnetotail so that kinetic energy from the solar wind is converted into magnetic energy in the field lines in the tail. Localized collapses of the crosstail current, which is driven by the large-scale dawn/dusk electric field in the magnetosphere, divert part of this current along geomagnetic field lines to the ionosphere, causing substorms with auroral activity and magnetic disturbances. The collapses also inject plasma into the radiation belts and build up a ring current. Frequent collapses in rapid succession constitute the geomagnetic storm.

  8. Floating Offshore WTG Integrated Load Analysis & Optimization Employing a Tuned Mass Damper

    SciTech Connect

    Rodriguez Tsouroukdissian, Arturo; Lackner, Matt; Cross-Whiter, John; Ackers, Ben; Arora, Dhiraj; Park, Semiung

    2015-09-25

    Floating offshore wind turbines (FOWTs) present complex design challenges due to the coupled dynamics of the platform motion, mooring system, and turbine control systems, in response to wind and wave loading. This can lead to higher extreme and fatigue loads than a comparable fixed bottom or onshore system. Previous research[1] has shown the potential to reduced extreme and fatigue loads on FOWT using tuned mass dampers (TMD) for structural control. This project aims to reduce maximum loads using passive TMDs located at the tower top during extreme storm events, when grid supplied power for other controls systems may not be available. The Alstom Haliade 6MW wind turbine is modelled on the Glosten Pelastar tension-leg platform (TLP). The primary objectives of this project are to provide a preliminary assessment of the load reduction potential of passive TMDs on real wind turbine and TLP designs.

  9. Basic Wind Tech Course - Lesson Plans and Activities

    SciTech Connect

    Swapp, Andy

    2011-07-01

    The funds from this project were used to purchase tools and instrumentation to help replicate actual on-the-job wind energy scenarios which provided the students with the practical or applied components of wind energy jobs. This project enhanced the educational experiences provided for the students in terms of engineering and science components of wind energy by using electronics, control systems, and electro-mechanical instrumentation to help students learn standardized wind-specific craftsman skills. In addition the tools and instrumentation helped the students learn the safety necessary to work in the wind industry.

  10. DOE/NREL supported wind energy activities in Indonesia

    SciTech Connect

    Drouilhet, S.

    1997-12-01

    This paper describes three wind energy related projects which are underway in Indonesia. The first is a USAID/Winrock Wind for Island and Nongovernmental Development (WIND) project. The objectives of this project are to train local nongovernmental organizations (NGOs) in the siting, installation, operation, and maintenance of small wind turbines. Then to install up to 20 wind systems to provide electric power for productive end uses while creating micro-enterprises which will generate enough revenue to sustain the wind energy systems. The second project is a joint Community Power Corporation/PLN (Indonesian National Electric Utility) case study of hybrid power systems in village settings. The objective is to evaluate the economic viability of various hybrid power options for several different situations involving wind/photovoltaics/batteries/diesel. The third project is a World Bank/PLN preliminary market assessment for wind/diesel hybrid systems. The objective is to estimate the size of the total potential market for wind/diesel hybrid power systems in Indonesia. The study will examine both wind retrofits to existing diesel mini-grids and new wind-diesel plants in currently unelectrified villages.

  11. Study on coupled shock absorber system using four electromagnetic dampers

    NASA Astrophysics Data System (ADS)

    Fukumori, Y.; Hayashi, R.; Okano, H.; Suda, Y.; Nakano, K.

    2016-09-01

    Recently, the electromagnetic damper, which is composed of an electric motor, a ball screw, and a nut, was proposed. The electromagnetic damper has high responsiveness, controllability, and energy saving performance. It has been reported that it improved ride comfort and drivability. In addition, the authors have proposed a coupling method of two electromagnetic dampers. The method enables the characteristics of bouncing and rolling or pitching motion of a vehicle to be tuned independently. In this study, the authors increase the number of coupling of electromagnetic dampers from two to four, and propose a method to couple four electromagnetic dampers. The proposed method enables the characteristics of bouncing, rolling and pitching motion of a vehicle to be tuned independently. Basic experiments using proposed circuit and motors and numerical simulations of an automobile equipped with the proposed coupling electromagnetic damper are carried out. The results indicate the proposed method is effective.

  12. DOE/NREL supported wind energy activities in Alaska

    SciTech Connect

    Drouilhet, S.

    1997-12-01

    This paper describes three wind energy projects implemented in Alaska. The first, a sustainable technology energy partnerships (STEP) wind energy deployment project in Kotzebue will install 6 AOC 15/50 wind turbines and connect to the existing village diesel grid, consisting of approximately 1 MW average load. It seeks to develop solutions to the problems of arctic wind energy installations (transport, foundations, erection, operation, and maintenance), to establish a wind turbine test site, and to establish the Kotzebue Electric Association as a training and deployment center for wind/diesel technology in rural Alaska. The second project, a large village medium-penetration wind/diesel system, also in Kotzebue, will install a 1-2 MW windfarm, which will supplement the AOC turbines of the STEP project. The program will investigate the impact of medium penetration wind energy on power quality and system stability. The third project, the Alaska high-penetration wind/diesel village power pilot project in Wales will install a high penetration (80-100%) wind/diesel system in a remote Alaskan village. The system will include about 180 kW installed wind capacity, meeting an average village load of about 60 kW. This program will provide a model for high penetration wind retrofits to village diesel power systems and build the capability in Alaska to operate, maintain, and replicate wind/diesel technology. The program will also address problems of: effective use of excess wind energy; reliable diesel-off operation; and the role of energy storage.

  13. Atmospheric wind field conditions generated by active grids

    NASA Astrophysics Data System (ADS)

    Knebel, Pascal; Kittel, Achim; Peinke, Joachim

    2011-08-01

    An active grid for turbulence generation of several rotatable axes with surmounted vanes that can be driven via stepper or servo motors is presented. We investigate the impact of different excitation protocols for the grid. Using such protocols that already have the intermittent structure of turbulence, higher intermittent flows can be achieved. This concept can also be used to generate turbulent flows of high turbulence intensities (>25%) exhibiting integral length scales beyond the typical size of the test section of the wind tunnel. Similar two-point correlations measured by the intermittent statistics of velocity increments that are characteristic for flows of high Reynolds number, i.e. in the atmospheric boundary layer, can be reproduced.

  14. The solar wind effect on cosmic rays and solar activity

    NASA Technical Reports Server (NTRS)

    Fujimoto, K.; Kojima, H.; Murakami, K.

    1985-01-01

    The relation of cosmic ray intensity to solar wind velocity is investigated, using neutron monitor data from Kiel and Deep River. The analysis shows that the regression coefficient of the average intensity for a time interval to the corresponding average velocity is negative and that the absolute effect increases monotonously with the interval of averaging, tau, that is, from -0.5% per 100km/s for tau = 1 day to -1.1% per 100km/s for tau = 27 days. For tau 27 days the coefficient becomes almost constant independently of the value of tau. The analysis also shows that this tau-dependence of the regression coefficiently is varying with the solar activity.

  15. Squeeze film dampers with oil hole feed

    NASA Astrophysics Data System (ADS)

    Chen, P. Y. P.; Hahn, E. J.

    1994-01-01

    To improve the damping capability of squeeze film dampers, oil hole feed rather than circumferential groove feed is a practical proposition. However, circular orbit response can no longer be assumed, significantly complicating the design analysis. This paper details a feasible transient solution procedure for such dampers, with particular emphasis on the additional difficulties due to the introduction of oil holes. It is shown how a cosine power series solution may be utilized to evaluate the oil hole pressure contributions, enabling appropriate tabular data to be compiled. The solution procedure is shown to be applicable even in the presence of flow restrictors, albeit at the expense of introducing an iteration at each time step. Though not of primary interest, the procedure is also applicable to dynamically loaded journal bearings with oil hole feed.

  16. BNL 56 MHz HOM damper prototype fabrication at JLAB

    SciTech Connect

    Huque, N.; McIntyre, G.; Daly, E. F.; Clemens, W.; Wu, Q.; Seberg, S.; Bellavia, S.

    2015-05-03

    A prototype Higher-Order Mode (HOM) Damper was fabricated at JLab for the Relativistic Heavy-Ion Collider’s (RHIC) 56 MHz cavity at Brookhaven National Laboratory (BNL). Primarily constructed from high RRR Niobium and Sapphire, the coaxial damper presented significant challenges in electron-beam welding (EBW), brazing and machining via acid etching. The results of the prototype operation brought about changes in the damper design, due to overheating braze alloys and possible multi-pacting. Five production HOM dampers are currently being fabricated at JLab. This paper outlines the challenges faced in the fabrication process, and the solutions put in place.

  17. BNL 56 MHz HOM Damper Prototype Fabrication at JLab

    SciTech Connect

    Huque, Naeem A.; Daly, Edward F.; Clemens, William A.; McIntyre, Gary T.; Wu, Qiong; Seberg, Scott; Bellavia, Steve

    2015-09-01

    A prototype Higher-Order Mode (HOM) Damper was fabricated at JLab for the Relativistic Heavy-Ion Collider's (RHIC) 56 MHz cavity at Brookhaven National Laboratory (BNL). Primarily constructed from high RRR Niobium and Sapphire, the coaxial damper presented significant challenges in electron-beam welding (EBW), brazing and machining via acid etching. The results of the prototype operation brought about changes in the damper design, due to overheating braze alloys and possible multi-pacting. Five production HOM dampers are currently being fabricated at JLab. This paper outlines the challenges faced in the fabrication process, and the solutions put in place.

  18. Stochastic seismic response of building with super-elastic damper

    NASA Astrophysics Data System (ADS)

    Gur, Sourav; Mishra, Sudib Kumar; Roy, Koushik

    2016-05-01

    Hysteretic yield dampers are widely employed for seismic vibration control of buildings. An improved version of such damper has been proposed recently by exploiting the superelastic force-deformation characteristics of the Shape-Memory-Alloy (SMA). Although a number of studies have illustrated the performance of such damper, precise estimate of the optimal parameters and performances, along with the comparison with the conventional yield damper is lacking. Presently, the optimal parameters for the superelastic damper are proposed by conducting systematic design optimization, in which, the stochastic response serves as the objective function, evaluated through nonlinear random vibration analysis. These optimal parameters can be employed to establish an initial design for the SMA-damper. Further, a comparison among the optimal responses is also presented in order to assess the improvement that can be achieved by the superelastic damper over the yield damper. The consistency of the improvements is also checked by considering the anticipated variation in the system parameters as well as seismic loading condition. In spite of the improved performance of super-elastic damper, the available variant of SMA(s) is quite expensive to limit their applicability. However, recently developed ferrous SMA are expected to offer even superior performance along with improved cost effectiveness, that can be studied through a life cycle cost analysis in future work.

  19. Non-linear identification of a squeeze-film damper

    NASA Technical Reports Server (NTRS)

    Stanway, Roger; Mottershead, John; Firoozian, Riaz

    1987-01-01

    Described is an experimental study to identify the damping laws associated with a squeeze-film vibration damper. This is achieved by using a non-linear filtering algorithm to process displacement responses of the damper ring to synchronous excitation and thus to estimate the parameters in an nth-power velocity model. The experimental facility is described in detail and a representative selection of results is included. The identified models are validated through the prediction of damper-ring orbits and comparison with observed responses.

  20. Study of the response time of MR dampers

    NASA Astrophysics Data System (ADS)

    Guan, Xinchun; Guo, Pengfei; Ou, Jinping

    2009-07-01

    Response time is an important parameter which determines the applied fields and practical vibration reduction effects of magnetorheological (MR) dampers. However, up to now, only a few papers discuss the test and analysis of response times. In this paper, the response time of a large-scale MR damper at different velocities and currents was firstly tested. Then, the transient magnetic field excited by the time-variant excitation current was simulated by finite element method (FEM). Based on the variation of the shear yield stress of magnetorheological fluids in the gap between the cylinder and the piston, the response time of the MR damper was investigated. Influences of eddy current and excitation current response time on the damper's response were also explored. Results show that by utilizing finite elements method, the calculated average effective shear yield strength can be used to predict the response time of a MR damper. Electromagnetic response is the predominant factor influencing the response time of a MR damper, and reducing eddy currents is the key to accelerate the response of a MR damper. Moreover, influence of eddy currents is much larger under stepping down excitation currents than stepping up currents, and with a same magnitude of step, no matter when the current increases or decreases, the smaller the initial current, the greater the eddy current affects a damper's response and the longer the response time of damping force is. A fast response excitation current may induce large eddy currents which reduce the response of the damper instead.

  1. Tutorial of Wind Turbine Control for Supporting Grid Frequency through Active Power Control: Preprint

    SciTech Connect

    Aho, J.; Buckspan, A.; Laks, J.; Fleming, P.; Jeong, Y.; Dunne, F.; Churchfield, M.; Pao, L.; Johnson, K.

    2012-03-01

    As wind energy becomes a larger portion of the world's energy portfolio and wind turbines become larger and more expensive, wind turbine control systems play an ever more prominent role in the design and deployment of wind turbines. The goals of traditional wind turbine control systems are maximizing energy production while protecting the wind turbine components. As more wind generation is installed there is an increasing interest in wind turbines actively controlling their power output in order to meet power setpoints and to participate in frequency regulation for the utility grid. This capability will be beneficial for grid operators, as it seems possible that wind turbines can be more effective at providing some of these services than traditional power plants. Furthermore, establishing an ancillary market for such regulation can be beneficial for wind plant owner/operators and manufacturers that provide such services. In this tutorial paper we provide an overview of basic wind turbine control systems and highlight recent industry trends and research in wind turbine control systems for grid integration and frequency stability.

  2. a Method for Preview Vibration Control of Systems Having Forcing Inputs and Rapidly-Switched Dampers

    NASA Astrophysics Data System (ADS)

    ElBeheiry, E. M.

    1998-07-01

    In a variety of applications, especially in large scale dynamic systems, the mechanization of different vibration control elements in different locations would be decided by limitations placed on the modal vibration of the system and the inherent dynamic coupling between its modes. Also, the quality of vibration control to the economy of producing the whole system would be another trade-off leading to a mix of passive, active and semi-active vibration control elements in one system. This termactiveis limited to externally powered vibration control inputs and the termsemi-activeis limited to rapidly switched dampers. In this article, an optimal preview control method is developed for application to dynamic systems having active and semi-active vibration control elements mechanized at different locations in one system. The system is then a piecewise (bilinear) controller in which two independent sets of control inputs appear additively and multiplicatively. Calculus of variations along with the Hamiltonian approach are employed for the derivation of this method. In essence, it requires the active elements to be ideal force generators and the switched dampers to have the property of on-line variation of the damping characteristics to pre-determined limits. As the dampers switch during operation the whole system's structure differs, and then values of the active forcing inputs are adapted to match these rapid changes. Strictly speaking, each rapidly switched damper has pre-known upper and lower damping levels and it can take on any in-between value. This in-between value is to be determined by the method as long as the damper tracks a pre-known fully active control demand. In every damping state of each semi-active damper the method provides the optimal matching values of the active forcing inputs. The method is shown to have the feature of solving simple standard matrix equations to obtain closed form solutions. A comprehensive 9-DOF tractor semi-trailer model is used

  3. A magnetic damper for first mode vibration reduction in multimass flexible rotors

    NASA Technical Reports Server (NTRS)

    Kasarda, M. E. F.; Allaire, P. E.; Humphris, R. R.; Barrett, L. E.

    1989-01-01

    Many rotating machines such as compressors, turbines and pumps have long thin shafts with resulting vibration problems, and would benefit from additional damping near the center of the shaft. Magnetic dampers have the potential to be employed in these machines because they can operate in the working fluid environment unlike conventional bearings. An experimental test rig is described which was set up with a long thin shaft and several masses to represent a flexible shaft machine. An active magnetic damper was placed in three locations: near the midspan, near one end disk, and close to the bearing. With typical control parameter settings, the midspan location reduced the first mode vibration 82 percent, the disk location reduced it 75 percent and the bearing location attained a 74 percent reduction. Magnetic damper stiffness and damping values used to obtain these reductions were only a few percent of the bearing stiffness and damping values. A theoretical model of both the rotor and the damper was developed and compared to the measured results. The agreement was good.

  4. Dynamic analogy between an electromagnetic shunt damper and a tuned mass damper

    NASA Astrophysics Data System (ADS)

    Zhu, Songye; Shen, Wenai; Qian, Xin

    2013-11-01

    An electromagnetic shunt damper (EMSD) is composed of an electromagnetic damper connected to one or more RLC shunt circuits. Through a theoretical comparison, this paper reveals the similarity and difference between an EMSD and a tuned mass damper (TMD), both of which are resonant-type vibration absorbers. The equivalent mass, stiffness and damping coefficient of the EMSD are derived based on the transfer functions of structures with a TMD or an EMSD, and the functions of circuit capacitance and inductance are discussed accordingly. The optimal parameters of the RLC circuit in the EMSD are obtained through H∞ optimization. Despite their different optimal parameters, the EMSD and TMD exhibit comparable control performance with the same equivalent mass ratio. The dynamic analogy between these two types of dampers offers a new perspective for understanding novel EMSDs, given that TMDs have previously been extensively studied. The potentials and constraints of the EMSD are further discussed through numerical case studies in which EMSD control performance is examined in different situations.

  5. Solar activity variations of nocturnal thermospheric meridional winds over Indian longitude sector

    NASA Astrophysics Data System (ADS)

    Madhav Haridas, M. K.; Manju, G.; Arunamani, T.

    2016-09-01

    The night time F-layer base height information from ionosondes located at two equatorial stations Trivandrum (TRV 8.5°N, 77°E) and Sriharikota (SHAR 13.7°N, 80.2°E) spanning over two decades are used to derive the climatology of equatorial nocturnal Thermospheric Meridional Winds (TMWs) prevailing during High Solar Activity (HSA) and Low Solar Activity (LSA) epochs. The important inferences from the analysis are 1) Increase in mean equatorward winds observed during LSA compared to HSA during pre midnight hours; 25 m/s for VE (Vernal Equinox) and 20 m/s for SS (Summer Solstice), AE (autumnal Equinox) and WS (Winter Solstice). 2) Mean wind response to Solar Flux Unit (SFU) is established quantitatively for all seasons for pre-midnight hours; rate of increase is 0.25 m/s/SFU for VE, 0.2 m/s/SFU for SS and WS and 0.08 m/s/SFU for AE. 3) Theoretical estimates of winds for the two epochs are performed and indicate the role of ion drag forcing as a major factor influencing TMWs. 4) Observed magnitude of winds and rate of flux dependencies are compared to thermospheric wind models. 5) Equinoctial asymmetry in TMWs is observed for HSA at certain times, with more equatorward winds during AE. These observations lend a potential to parameterize the wind components and effectively model the winds, catering to solar activity variations.

  6. Inelastic Seismic Response of Building with Friction Damper

    NASA Astrophysics Data System (ADS)

    Banerjee, Susanta; Patro, Sanjaya K.

    2016-12-01

    Dampers are used to control response of structure in recent years. Seismic response is reduced by adding energy dissipation capacity to the building. Dampers are provided to dissipate energy to reduce the damages on buildings. Relative displacement of two floors are opposed by damper elements. Dampers dissipate energy with no or little degradation in strength and stiffness. This work presents the response of structure with energy dissipation device i.e. friction damper built on soft soil when the structure is subjected to a ground motion. Parameters that influence strength and stiffness of structure and energy dissipating device are studied. Response of structure with energy dissipating device is analyzed and it is shown that building with damper shows better performance during earthquake. Building structures are designed using results from elastic analysis, though inelastic behavior well observed during the earthquake. Actual response of the structure can be estimated in the inelastic range by using nonlinear structural analysis programs. Inelastic Damage indices of structural component, overall building are computed by formulating Modified Park and Ang model. Nonlinear analysis program IDARC 2D is used for modeling and analysis. Modeling of friction damper is done using a Wen-Bouc model without stiffness and strength or strength degradation. These devices are modeled with an axial diagonal element. Pseudo force approach is introduced to consider the forces in damper elements, that is, forces in damper elements are subtracted from external load vector. Smooth hysteretic model is used to model response of friction dampers. Nonlinear dynamic analysis is carried out using Newmark-Beta integration method and the pseudo-force method. Damaged state of structure is obtained to observe whether elements are cracked, yielded or failed during analysis. Response parameters such as lateral floor displacement, storey drift, base shear are also computed.

  7. An adaptive tuned mass damper based on the emulation of positive and negative stiffness with an MR damper

    NASA Astrophysics Data System (ADS)

    Weber, F.; Boston, C.; Maślanka, M.

    2011-01-01

    This paper presents a new adaptive tuned mass damper (TMD) whose stiffness and damping can be tuned in real-time to changing frequencies of a target structure. The adaptive TMD consists of a tuned mass, a tuned passive spring and a magnetorheological (MR) damper. The MR damper is used to emulate controlled friction-viscous damping and controlled stiffness. The controlled positive or negative stiffness emulated by the MR damper works in parallel to the stiffness of the passive TMD spring. The resulting overall TMD stiffness can therefore be varied around the passive spring stiffness using the MR damper. Both the emulated stiffness and friction-viscous damping in the MR damper are controlled such that the resulting overall TMD stiffness and damping are adjusted according to Den Hartog's formulae. Simulations demonstrate that the adaptive TMD with a controlled MR damper provides the same reduction of steady state vibration amplitudes in the target structure as a passive TMD if the target structure vibrates at the nominal frequency. However, if the target structure vibrates at different frequencies, e.g. due to changed service loads, the adaptive TMD with a controlled MR damper outperforms the passive TMD by up to several 100% depending on the frequency change.

  8. A prosthetic knee using magnetorhelogical fluid damper for above-knee amputees

    NASA Astrophysics Data System (ADS)

    Park, Jinhyuk; Choi, Seung-Bok

    2015-04-01

    A prosthetic knee for above-knee (AK) amputees is categorized into two types; namely a passive and an active type. The passive prosthetic knee is generally made by elastic materials such as carbon fiber reinforced composite material, titanium and etc. The passive prosthetic knee easy to walk. But, it has disadvantages such that a knee joint motion is not similar to ordinary people. On the other hand, the active prosthetic knee can control the knee joint angle effectively because of mechanical actuator and microprocessor. The actuator should generate large damping force to support the weight of human body. But, generating the large torque using small actuator is difficult. To solve this problem, a semi-active type prosthetic knee has been researched. This paper proposes a semi-active prosthetic knee using a flow mode magneto-rheological (MR) damper for AK amputees. The proposed semi-active type prosthetic knee consists of the flow mode MR damper, hinge and prosthetic knee body. In order to support weight of human body, the required energy of MR damper is smaller than actuator of active prosthetic leg. And it can control the knee joint angle by inducing the magnetic field during the stance phase.

  9. 78 FR 8190 - Commercial Wind Leasing and Site Assessment Activities on the Atlantic Outer Continental Shelf...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-05

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF THE INTERIOR Bureau of Ocean Energy Management Commercial Wind Leasing and Site Assessment Activities on the Atlantic... Notice of Intent to Prepare an Environmental Assessment (EA) for Commercial Wind Leasing and...

  10. Seismic Risk Mitigation of Historical Minarets Using SMA Wire Dampers

    SciTech Connect

    El-Attar, Adel G.; Saleh, Ahmed M.; El-Habbal, Islam R.

    2008-07-08

    This paper presents the results of a research program sponsored by the European Commission through project WIND-CHIME (Wide Range Non-INtrusive Devices toward Conservation of HIstorical Monuments in the MEditerranean Area), in which the possibility of using advanced seismic protection technologies to preserve historical monuments in the Mediterranean area is investigated. In the current research, two outstanding Egyptian Mamluk-Style minarets, are investigated. The first is the southern minaret of Al-Sultaniya (1340 A.D, 739 Hijri Date (H.D.)), the second is the minaret of Qusun minaret (1337 A.D, 736 H.D.), both located within the city of Cairo. Based on previous studies on the minarets by the authors, a seismic retrofit technique is proposed. The technique utilizes shape memory alloy (SMA) wires as dampers for the upper, more flexible, parts of the minarets in addition to vertical pre-stressing of the lower parts found to be prone to tensile cracking under ground excitation. The effectiveness of the proposed technique is numerically evaluated via nonlinear transient dynamic analyses. The results indicate the effectiveness of the technique in mitigating the seismic hazard, demonstrated by the effective reduction in stresses and in dynamic response.

  11. Seismic Risk Mitigation of Historical Minarets Using SMA Wire Dampers

    NASA Astrophysics Data System (ADS)

    El-Attar, Adel G.; Saleh, Ahmed M.; El-Habbal, Islam R.

    2008-07-01

    This paper presents the results of a research program sponsored by the European Commission through project WIND-CHIME (Wide Range Non-INtrusive Devices toward Conservation of HIstorical Monuments in the MEditerranean Area), in which the possibility of using advanced seismic protection technologies to preserve historical monuments in the Mediterranean area is investigated. In the current research, two outstanding Egyptian Mamluk-Style minarets, are investigated. The first is the southern minaret of Al-Sultaniya (1340 A.D, 739 Hijri Date (H.D.)), the second is the minaret of Qusun minaret (1337 A.D, 736 H.D.), both located within the city of Cairo. Based on previous studies on the minarets by the authors, a seismic retrofit technique is proposed. The technique utilizes shape memory alloy (SMA) wires as dampers for the upper, more flexible, parts of the minarets in addition to vertical pre-stressing of the lower parts found to be prone to tensile cracking under ground excitation. The effectiveness of the proposed technique is numerically evaluated via nonlinear transient dynamic analyses. The results indicate the effectiveness of the technique in mitigating the seismic hazard, demonstrated by the effective reduction in stresses and in dynamic response.

  12. On a Self-Tuning Impact Vibration Damper for Rotating Turbomachinery

    NASA Technical Reports Server (NTRS)

    Duffy, Kirsten P.; Bagley, Ronald L.; Mehmed, Oral; Choi, Ben (Technical Monitor)

    2000-01-01

    A self-tuning impact damper is investigated analytically and experimentally as a device to inhibit vibration and increase the fatigue life of rotating components in turbomachinery. High centrifugal loads in rotors can inactivate traditional impact dampers because of friction or misalignment of the damper in the g-field. Giving an impact damper characteristics of an acceleration tuned-mass damper enables the resulting device to maintain damper mass motion and effectiveness during high-g loading. Experimental results presented here verify that this self-tuning impact damper can be designed to follow an engine order line. damping rotor component resonance crossings.

  13. Extended Kalman filter for modal identification of structures equipped with a pendulum tuned mass damper

    NASA Astrophysics Data System (ADS)

    Roffel, A. J.; Narasimhan, S.

    2014-11-01

    Pendulum tuned mass dampers (PTMDs) have been employed in several full-scale applications to attenuate excessive structural motions, which are mostly due to wind. Conducting periodic condition assessments of the devices to ascertain their health is necessary to ensure their continued optimal performance, which involves identifying the modal parameters of the underlying (bare) structure to which they are tuned to. Such an identification is also necessary for the design of control systems such as adaptive tuned mass dampers. Existing methods of arresting the motion of the damper to estimate the modal properties are expensive, time-consuming, and not suitable for online tuning. Instead, in this paper, parameter estimation using the Extended Kalman Filter (EKF) is proposed to undertake this task. The central task accomplished here is to estimate the dynamic characteristics of the bare structure (structure without the PTMD) from response measurements of the coupled main structure and PTMD system. The proposed methodology relies on ambient acceleration measurements of TMD-attenuated responses to estimate the bare structural modal frequencies, damping, and mode shapes, which can then be used either for condition assessment or for control. The application of EKF to modal parameter estimation is not new. However, a methodology to address the problem in wind engineering arising from stochastic disturbances present in both the measurement and state equations, and unknown process and noise covariances arising due to ambient excitations, is presented for the first time. Extensively studied for synthetic data, these two challenges have limited thus far the application of Kalman filtering to practical wind engineering parameter estimation problems using experimentally obtained measurements. In this paper, a detailed methodology is presented to address these challenges by using a modified form of the standard EKF equations, together with an algorithm to estimate the unknown

  14. Tunable damper for an acoustic wave guide

    DOEpatents

    Rogers, Samuel C.

    1984-01-01

    A damper for tunably damping acoustic waves in an ultrasonic waveguide is provided which may be used in a hostile environment such as a nuclear reactor. The area of the waveguide, which may be a selected size metal rod in which acoustic waves are to be damped, is wrapped, or surrounded, by a mass of stainless steel wool. The wool wrapped portion is then sandwiched between tuning plates, which may also be stainless steel, by means of clamping screws which may be adjusted to change the clamping force of the sandwiched assembly along the waveguide section. The plates are preformed along their length in a sinusoidally bent pattern with a period approximately equal to the acoustic wavelength which is to be damped. The bent pattern of the opposing plates are in phase along their length relative to their sinusoidal patterns so that as the clamping screws are tightened a bending stress is applied to the waveguide at 180.degree. intervals along the damping section to oppose the acoustic wave motions in the waveguide and provide good coupling of the wool to the guide. The damper is tuned by selectively tightening the clamping screws while monitoring the amplitude of the acoustic waves launched in the waveguide. It may be selectively tuned to damp particular acoustic wave modes (torsional or extensional, for example) and/or frequencies while allowing others to pass unattenuated.

  15. The effect of friction in coulombian damper

    NASA Astrophysics Data System (ADS)

    Wahad, H. S.; Tudor, A.; Vlase, M.; Cerbu, N.; Subhi, K. A.

    2017-02-01

    The study aimed to analyze the damping phenomenon in a system with variable friction, Stribeck type. Shock absorbers with limit and dry friction, is called coulombian shock-absorbers. The physical damping vibration phenomenon, in equipment, is based on friction between the cushioning gasket and the output regulator of the shock-absorber. Friction between them can be dry, limit, mixture or fluid. The friction is depending on the contact pressure and lubricant presence. It is defined dimensionless form for the Striebeck curve (µ friction coefficient - sliding speed v). The friction may damp a vibratory movement or can maintain it (self-vibration), depending on the µ with v (it can increase / decrease or it can be relative constant). The solutions of differential equation of movement are obtained for some work condition of one damper for automatic washing machine. The friction force can transfer partial or total energy or generates excitation energy in damper. The damping efficiency is defined and is determined analytical for the constant friction coefficient and for the parabolic friction coefficient.

  16. Tunable damper for an acoustic wave guide

    DOEpatents

    Rogers, S.C.

    1982-10-21

    A damper for tunably damping acoustic waves in an ultrasonic waveguide is provided which may be used in a hostile environment such as a nuclear reactor. The area of the waveguide, which may be a selected size metal rod in which acoustic waves are to be damped, is wrapped, or surrounded, by a mass of stainless steel wool. The wool wrapped portion is then sandwiched between tuning plates, which may also be stainless steel, by means of clamping screws which may be adjusted to change the clamping force of the sandwiched assembly along the waveguide section. The plates are preformed along their length in a sinusoidally bent pattern with a period approximately equal to the acoustic wavelength which is to be damped. The bent pattern of the opposing plates are in phase along their length relative to their sinusoidal patterns so that as the clamping screws are tightened a bending stress is applied to the waveguide at 180/sup 0/ intervals along the damping section to oppose the acoustic wave motions in the waveguide and provide good coupling of the wool to the guide. The damper is tuned by selectively tightening the clamping screws while monitoring the amplitude of the acoustic waves launched in the waveguide. It may be selectively tuned to damp particular acoustic wave modes (torsional or extensional, for example) and/or frequencies while allowing others to pass unattenuated.

  17. Design and test of a squeeze-film damper for a flexible power transmission shaft

    NASA Technical Reports Server (NTRS)

    Darlow, M. S.; Smalley, A. J.

    1978-01-01

    For a flexible shaft designed to pass through a number of bending critical speeds, a squeeze-film damper has been designed and tested. The damper properties were selected to provide control of all critical speeds, while meeting additional constraints of high power transmission requirements and damper simplicity. The damper was fabricated and installed and its ability to control flexible shaft vibrations was demonstrated by the comparison of vibration amplitudes both with and without the damper.

  18. Combining Droop Curve Concepts with Control Systems for Wind Turbine Active Power Control: Preprint

    SciTech Connect

    Buckspan, A.; Aho, J.; Pao, L.; Fleming, P.; Jeong, Y.

    2012-06-01

    Wind energy is becoming a larger portion of the global energy portfolio and wind penetration has increased dramatically in certain regions of the world. This increasing wind penetration has driven the need for wind turbines to provide active power control (APC) services to the local utility grid, as wind turbines do not intrinsically provide frequency regulation services that are common with traditional generators. It is common for large scale wind turbines to be decoupled from the utility grid via power electronics, which allows the turbine to synthesize APC commands via control of the generator torque and blade pitch commands. Consequently, the APC services provided by a wind turbine can be more flexible than those provided by conventional generators. This paper focuses on the development and implementation of both static and dynamic droop curves to measure grid frequency and output delta power reference signals to a novel power set point tracking control system. The combined droop curve and power tracking controller is simulated and comparisons are made between simulations using various droop curve parameters and stochastic wind conditions. The tradeoffs involved with aggressive response to frequency events are analyzed. At the turbine level, simulations are performed to analyze induced structural loads. At the grid level, simulations test a wind plant's response to a dip in grid frequency.

  19. Response of ventilation dampers to large airflow pulses

    SciTech Connect

    Gregory, W.S.; Smith, P.R.

    1985-04-01

    The results of an experiment program to evaluate the response of ventilation system dampers to simulated tornado transients are reported. Relevant data, such as damper response time, flow rate and pressure drop, and flow/pressure vs blade angle, were obtained, and the response of one tornado protective damper to simulated tornado transients was evaluated. Empirical relationships that will allow the data to be integrated into flow dynamics codes were developed. These flow dynamics codes can be used by safety analysts to predict the response of nuclear facility ventilation systems to tornado depressurization. 3 refs., 21 figs., 6 tabs.

  20. Flux-tube geometry and solar wind speed during an activity cycle

    NASA Astrophysics Data System (ADS)

    Pinto, R. F.; Brun, A. S.; Rouillard, A. P.

    2016-07-01

    Context. The solar wind speed at 1 AU shows cyclic variations in latitude and in time which reflect the evolution of the global background magnetic field during the activity cycle. It is commonly accepted that the terminal (asymptotic) wind speed in a given magnetic flux-tube is generally anti-correlated with its total expansion ratio, which motivated the definition of widely used semi-empirical scaling laws relating one to the other. In practice, such scaling laws require ad hoc corrections (especially for the slow wind in the vicinities of streamer/coronal hole boundaries) and empirical fits to in situ spacecraft data. A predictive law based solely on physical principles is still missing. Aims: We test whether the flux-tube expansion is the controlling factor of the wind speed at all phases of the cycle and at all latitudes (close to and far from streamer boundaries) using a very large sample of wind-carrying open magnetic flux-tubes. We furthermore search for additional physical parameters based on the geometry of the coronal magnetic field which have an influence on the terminal wind flow speed. Methods: We use numerical magneto-hydrodynamical simulations of the corona and wind coupled to a dynamo model to determine the properties of the coronal magnetic field and of the wind velocity (as a function of time and latitude) during a whole 11-yr activity cycle. These simulations provide a large statistical ensemble of open flux-tubes which we analyse conjointly in order to identify relations of dependence between the wind speed and geometrical parameters of the flux-tubes which are valid globally (for all latitudes and moments of the cycle). Results: Our study confirms that the terminal (asymptotic) speed of the solar wind depends very strongly on the geometry of the open magnetic flux-tubes through which it flows. The total flux-tube expansion is more clearly anti-correlated with the wind speed for fast rather than for slow wind flows, and effectively controls the

  1. Design and verification of a negative resistance electromagnetic shunt damper for spacecraft micro-vibration

    NASA Astrophysics Data System (ADS)

    Stabile, Alessandro; Aglietti, Guglielmo S.; Richardson, Guy; Smet, Geert

    2017-01-01

    Active control techniques are often required to mitigate the micro-vibration environment existing on board spacecraft. However, reliability issues and high power consumption are major drawbacks of active isolation systems that have limited their use for space applications. In the present study, an electromagnetic shunt damper (EMSD) connected to a negative-resistance circuit is designed, modelled and analysed. The negative resistance produces an overall reduction of the circuit resistance that results in an increase of the induced current in the closed circuit and thus the damping performance. This damper can be classified as a semi-active damper since the shunt does not require any control algorithm to operate. Additionally, the proposed EMSD is characterised by low required power, simplified electronics and small device mass, allowing it to be comfortably integrated on a satellite. This work demonstrates, both analytically and experimentally, that this technology is capable of effectively isolating typical satellite micro-vibration sources over the whole temperature range of interest.

  2. Low-force magneto-rheological damper design for small-scale structural control experimentation

    NASA Astrophysics Data System (ADS)

    Winter, Benjamin D.; Velazquez, Antonio; Swartz, R. Andrew

    2015-03-01

    Experimental validation of novel structural control algorithms is a vital step in both developing and building acceptance for this technology. Small-scale experimental test-beds fulfill an important role in the validation of multiple-degree-offreedom (MDOF) and distributed semi-active control systems, allowing researchers to test the control algorithms, communication topologies, and timing-critical aspects of structural control systems that do not require full-scale specimens. In addition, small-scale building specimens can be useful in combined structural health monitoring (SHM) and LQG control studies, diminishing safety concerns during experiments by using benchtop-scale rather than largescale specimens. Development of such small-scale test-beds is hampered by difficulties in actuator construction. In order to be a useful analog to full-scale structures, actuators for small-scale test-beds should exhibit similar features and limitations as their full-scale counterparts. In particular, semi-active devices, such as magneto-rheological (MR) fluid dampers, with limited authority (versus active mass dampers) and nonlinear behavior are difficult to mimic over small force scales due to issues related to fluid containment and friction. In this study, a novel extraction-type small-force (0- 10 N) MR-fluid damper which exhibits nonlinear hysteresis similar to a full-scale, MR-device is proposed. This actuator is a key development to enable the function of a small-scale structural control test-bed intended for wireless control validation studies. Experimental validation of this prototype is conducted using a 3-story scale structure subjected to simulated single-axis seismic excitation. The actuator affects the structural response commanded by a control computer that executes an LQG state feedback control law and a modified Bouc-Wen lookup table that was previously developed for full-scale MR-applications. In addition, damper dynamic limitations are characterized and

  3. Frequency and damping adaptation of a TMD with controlled MR damper

    NASA Astrophysics Data System (ADS)

    Weber, F.; Maślanka, M.

    2012-05-01

    This paper describes the new concept of a semi-active tuned mass damper with magnetorheological damper (MR-STMD). The real-time controlled MR damper force emulates controlled damping and a superimposed controllable stiffness force to augment or diminish the force of the passive spring stiffness which enables us to control the MR-STMD natural frequency. Both the damping and natural frequency are tuned according to Den Hartog’s formulae to the actual dominant frequency of the main structure irrespective of whether it is a resonance or a forced frequency. The MR-STMD is experimentally validated on the Empa bridge with a 15.6 m main span for different added masses to shift its resonance frequency -12.2% and +10.4% away from its nominal value. The experimental results are compared to those obtained when the MR-STMD is operated as a passive TMD that is precisely tuned to the nominal bridge. The comparison shows that the MR-STMD outperforms the TMD both in the tuned and all de-tuned cases by up to 63%. Simulations of the MR-STMD concept point out that the proposed semi-active control algorithm is most suitable for MR-STMDs due to the small amount of clipped active forces. A sensitivity analysis demonstrates that the real MR-STMD could be even more powerful if the force tracking errors in the MR damper force due to the current driver and MR fluid dynamics and remanent magnetization effects could be further reduced. The MR-STMD under consideration represents the prototype of the 12 MR-STMDs that have been running on the Volgograd Bridge since late fall 2011.

  4. A Study on the Active Induction Control of Upstream Wind Turbines for total power increases

    NASA Astrophysics Data System (ADS)

    Kim, Hyungyu; Kim, Kwansoo; Paek, Insu; Bottasso, Carlo L.; Campagnolo, Filippo

    2016-09-01

    In this study, the effect of active induction control of upstream wind turbines is investigated. Two scaled wind turbines having a rotor diameter of 1 m with a spacing of four times of the rotor diameter were used to experimentally validate the concept. Also, an in-house c code was used to simulate the same two wind turbines and see if the experimental observations can be obtained. From the experiment, approximately 0.81% increase of total power could be observed. Although the simulation results were not exactly the same as the experimental results but the shape was similar and the maximum power increase of 0.27% was predicted. Also from further simulation using NREL 5MW wind turbines instead of scaled wind turbines with realistic ambient turbulence intensity, it was found that the power increase could become more than 1%.

  5. Observations of the effect of wind on the cooling of active lava flows

    USGS Publications Warehouse

    Keszthelyi, L.; Harris, A.J.L.; Dehn, J.

    2003-01-01

    We present the first direct observations of the cooling of active lava flows by the wind. We confirm that atmospheric convective cooling processes (i.e., the wind) dominate heat loss over the lifetime of a typical pahochoe lava flow. In fact, the heat extracted by convection is greater than predicted, especially at wind speeds less than 5 m/s and surface temperatures less than 400??C. We currently estimate that the atmospheric heat transfer coefficient is about 45-50 W m-2 K-1 for a 10 m/s wind and a surface temperature ???500??C. Further field experiments and theoretical studies should expand these results to a broader range of surface temperatures and wind speeds.

  6. Signatures of Slow Solar Wind Streams from Active Regions in the Inner Corona

    NASA Astrophysics Data System (ADS)

    Slemzin, V.; Harra, L.; Urnov, A.; Kuzin, S.; Goryaev, F.; Berghmans, D.

    2013-08-01

    The identification of solar-wind sources is an important question in solar physics. The existing solar-wind models ( e.g., the Wang-Sheeley-Arge model) provide the approximate locations of the solar wind sources based on magnetic field extrapolations. It has been suggested recently that plasma outflows observed at the edges of active regions may be a source of the slow solar wind. To explore this we analyze an isolated active region (AR) adjacent to small coronal hole (CH) in July/August 2009. On 1 August, Hinode/EUV Imaging Spectrometer observations showed two compact outflow regions in the corona. Coronal rays were observed above the active-region coronal hole (ARCH) region on the eastern limb on 31 July by STEREO-A/EUVI and at the western limb on 7 August by CORONAS- Photon/TESIS telescopes. In both cases the coronal rays were co-aligned with open magnetic-field lines given by the potential field source surface model, which expanded into the streamer. The solar-wind parameters measured by STEREO-B, ACE, Wind, and STEREO-A confirmed the identification of the ARCH as a source region of the slow solar wind. The results of the study support the suggestion that coronal rays can represent signatures of outflows from ARs propagating in the inner corona along open field lines into the heliosphere.

  7. Sliding mode control of wind-induced vibrations using fuzzy sliding surface and gain adaptation

    NASA Astrophysics Data System (ADS)

    Thenozhi, Suresh; Yu, Wen

    2016-04-01

    Although fuzzy/adaptive sliding mode control can reduce the chattering problem in structural vibration control applications, they require the equivalent control and the upper bounds of the system uncertainties. In this paper, we used fuzzy logic to approximate the standard sliding surface and designed a dead-zone adaptive law for tuning the switching gain of the sliding mode control. The stability of the proposed controller is established using Lyapunov stability theory. A six-storey building prototype equipped with an active mass damper has been used to demonstrate the effectiveness of the proposed controller towards the wind-induced vibrations.

  8. A comparison of 200 kN magneto-rheological damper models for use in real-time hybrid simulation pretesting

    NASA Astrophysics Data System (ADS)

    Jiang, Z.; Christenson, R.

    2011-06-01

    Control devices can be used to dissipate the energy of a civil structure subjected to dynamic loading, such as earthquake, wave and wind excitation, thus reducing structural damage and preventing failure. The magneto-rheological (MR) fluid damper is a promising device for use in civil structures due to its mechanical simplicity, inherent stability, high dynamic range, large temperature operating range, robust performance, and low power requirements. The MR damper is intrinsically nonlinear and rate dependent. Thus a challenging aspect of applying this technology is the development of accurate models to describe the behavior of such dampers for control design and evaluation purposes. In particular, a new type of experimental testing called real-time hybrid simulation (RTHS) combines numerical simulation with laboratory testing of physical components. As with any laboratory testing, safety is of critical importance. For RTHS in particular the feedback and dynamic interaction of physical and numerical components can result in potentially unstable behavior. For safety purposes, it is desired to conduct pretest simulations where the physical specimen is replaced with an appropriate numerical model yet the numerical RTHS component is left unchanged. These pretest simulations require a MR damper model that can exhibit stability and convergence at larger fixed integration time steps, and provide computational efficiency, speed of calculation, and accuracy during pretest verification of the experimental setup. Several models for MR dampers have been proposed, including the hyperbolic tangent, Bouc-Wen, viscous plus Dahl and algebraic models. This paper examines the relative performance of four MR damper models of large-scale 200 kN MR dampers as needed for pretest simulations of RTHS. Experimental tests are conducted on two large-scale MR dampers located at two RTHS test facilities at the Smart Structures Technology Laboratory at the University of Illinois at Urbana

  9. Performance and robustness of hybrid model predictive control for controllable dampers in building models

    NASA Astrophysics Data System (ADS)

    Johnson, Erik A.; Elhaddad, Wael M.; Wojtkiewicz, Steven F.

    2016-04-01

    A variety of strategies have been developed over the past few decades to determine controllable damping device forces to mitigate the response of structures and mechanical systems to natural hazards and other excitations. These "smart" damping devices produce forces through passive means but have properties that can be controlled in real time, based on sensor measurements of response across the structure, to dramatically reduce structural motion by exploiting more than the local "information" that is available to purely passive devices. A common strategy is to design optimal damping forces using active control approaches and then try to reproduce those forces with the smart damper. However, these design forces, for some structures and performance objectives, may achieve high performance by selectively adding energy, which cannot be replicated by a controllable damping device, causing the smart damper performance to fall far short of what an active system would provide. The authors have recently demonstrated that a model predictive control strategy using hybrid system models, which utilize both continuous and binary states (the latter to capture the switching behavior between dissipative and non-dissipative forces), can provide reductions in structural response on the order of 50% relative to the conventional clipped-optimal design strategy. This paper explores the robustness of this newly proposed control strategy through evaluating controllable damper performance when the structure model differs from the nominal one used to design the damping strategy. Results from the application to a two-degree-of-freedom structure model confirms the robustness of the proposed strategy.

  10. 66. INTERIOR VIEW OF THE COOLING BUILDING, LOOKING AM DAMPERS, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    66. INTERIOR VIEW OF THE COOLING BUILDING, LOOKING AM DAMPERS, HIGH TEMPERATURE AND LOW TEMPERATURE COOLERS. APRIL 11, 1919. - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

  11. Active Circulation Control for Horizontal Axis Wind Turbine

    NASA Astrophysics Data System (ADS)

    Dumitrache, Alexandru; Dumitrescu, Horia; Preotu, Octavian

    2011-09-01

    A based method for modeling the aerodynamics of horizontal axis wind turbine has been developed. Circulation control is implemented by tangentially blowing a small high-velocity jet over a highly curved surface, such as a rounded trailing edge. This causes the boundary layer and the jet sheet to remain attached along the curved surface due to the Coanda effect and causing the jet to turn without separation. This analysis has been validated for the experimental data of a rotor tested at NASA Ames Research Center. Comparisons have been done against measurements for surface pressure distribution, force coefficients normal and tangential to the chord line, torque and root bending moments. This approach for enhancing the circulation around the airfoil sections (and hence L/D and power production) has been examined and found to produce useful increases in power at low wind speeds.

  12. Seismic response reduction of a three-story building by an MR grease damper

    NASA Astrophysics Data System (ADS)

    Sakurai, Tomoki; Morishita, Shin

    2017-01-01

    This paper describes an application of magneto- rheological (MR) grease dampers as seismic dampers for a three-story steel structure. MR fluid is widely known as a smart material with rheological properties that can be varied by magnetic field strength. This material has been applied to various types of devices, such as dampers, clutches, and engine mounts. However, the ferromagnetic particles dispersed in MR fluid settle out of the suspension after a certain interval because of the density difference between the particles and their carrier fluid. To overcome this defect, we developed a new type of controllable working fluid using grease as the carrier of magnetic particles. MR grease was introduced into a cylindrical damper, and the seismic performance of the damper was subsequently studied via numerical analysis. The analysis results of the MR grease damper were compared with those of other seismic dampers. We confirmed that the MR grease damper is an effective seismic damper.

  13. Wind climatology of Toronto based on the NCEP/NCAR reanalysis 1 data and its potential relation to solar activity

    NASA Astrophysics Data System (ADS)

    Romanic, Djordje; Hangan, Horia; Ćurić, Mladjen

    2016-12-01

    This study represents a comprehensive analysis of the wind climatology for the Toronto area based on the daily National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis 1 data extracted for the period 1948-2014. The research is focused on investigating wind speed and wind direction distributions, long-term wind trends, and low-frequency wind spectrum. The results are given at the sigma-995 level. Westerlies are active in about 50% of the time in year. The strongest winds are coming in from 240° direction and the windiest seasons are winter and fall, followed by spring. A trend analysis shows that statistically significant and positive wind speed trends are present for both the omnidirectional mean annual wind speeds as well as for the winds associated with the most prevailing wind directions. Winter and fall winds had positive trends whereas negative wind speed trends in the summer and spring seasons are negligible. The spectral analysis of wind speed time series shows three distinguished peaks: (1) 2-4.5 days, (2) yearly, and (3) 11-year peak. The lowest frequency peak in the wind speed spectra is linked to the solar activity through the cross-correlation analysis and the relationship is discussed in details.

  14. Estimation of oceanic rainfall using passive and active measurements from SeaWinds spaceborne microwave sensor

    NASA Astrophysics Data System (ADS)

    Ahmad, Khalil Ali

    The Ku band microwave remote sensor, SeaWinds, was developed at the National Aeronautics and Space Administration (NASA) Jet Propulsion Laboratory (JPL). Two identical SeaWinds instruments were launched into space. The first was flown onboard NASA QuikSCAT satellite which has been orbiting the Earth since June 1999, and the second instrument flew onboard the Japanese Advanced Earth Observing Satellite II (ADEOS-II) from December 2002 till October 2003 when an irrecoverable solar panel failure caused a premature end to the ADEOS-II satellite mission. SeaWinds operates at a frequency of 13.4 GHz, and was originally designed to measure the speed and direction of the ocean surface wind vector by relating the normalized radar backscatter measurements to the near surface wind vector through a geophysical model function (GMF). In addition to the backscatter measurement capability, SeaWinds simultaneously measures the polarized radiometric emission from the surface and atmosphere, utilizing a ground signal processing algorithm known as the QuikSCAT/ SeaWinds Radiometer (QRad/SRad). This dissertation presents the development and validation of a mathematical inversion algorithm that combines the simultaneous active radar backscatter and the passive microwave brightness temperatures observed by the SeaWinds sensor to retrieve the oceanic rainfall. The retrieval algorithm is statistically based, and has been developed using collocated measurements from SeaWinds, the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) rain rates, and Numerical Weather Prediction (NWP) wind fields from the National Centers for Environmental Prediction (NCEP). The oceanic rain is retrieved on a spacecraft wind vector cell (WVC) measurement grid that has a spatial resolution of 25 km. To evaluate the accuracy of the retrievals, examples of the passive-only, as well as the combined active/passive rain estimates from SeaWinds are presented, and comparisons are made with the standard

  15. On the Relationship Between Solar Wind Speed, Geomagnetic Activity, and the Solar Cycle Using Annual Values

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.; Hathaway, David H.

    2008-01-01

    The aa index can be decomposed into two separate components: the leading sporadic component due to solar activity as measured by sunspot number and the residual or recurrent component due to interplanetary disturbances, such as coronal holes. For the interval 1964-2006, a highly statistically important correlation (r = 0.749) is found between annual averages of the aa index and the solar wind speed (especially between the residual component of aa and the solar wind speed, r = 0.865). Because cyclic averages of aa (and the residual component) have trended upward during cycles 11-23, cyclic averages of solar wind speed are inferred to have also trended upward.

  16. Determining the solar wind speed above active regions using remote radio-wave observations.

    PubMed

    Bougeret, J L; Fainberg, J; Stone, R G

    1983-11-04

    A new technique has made it possible to measure the velocity of portions of the solar wind during its flow outward from the sun. This analysis utilizes spacecraft (ISEE-3) observations of radio emission generated in regions of the solar wind associated with solar active regions. By tracking the source of these radio waves over periods of days, it is possible to measure the motion of the emission regions. Evidence of solar wind acceleration during this outward flow, consistent with theoretical models, has also been obtained.

  17. Wind tunnel productivity status and improvement activities at NASA Langley Research Center

    NASA Technical Reports Server (NTRS)

    Putnam, Lawrence E.

    1996-01-01

    Over the last three years, a major effort has been underway to re-engineering the way wind tunnel testing is accomplished at the NASA Langley Research Center. This effort began with the reorganization of the LaRC and the consolidation of the management of the wind tunnels in the Aerodynamics Division under one operations branch. This paper provides an overview of the re-engineering activities and gives the status of the improvements in the wind tunnel productivity and customer satisfaction that have resulted from the new ways of working.

  18. Determining the solar wind speed above active regions using remote radio-wave observations

    NASA Technical Reports Server (NTRS)

    Fainberg, J.; Stone, R. G.; Bougeret, J.-L.

    1983-01-01

    A new technique has made it possible to measure the velocity of portions of the solar wind during its flow outward from the sun. This analysis utilizes spacecraft (ISEE-3) observations of radio emission generated in regions of the solar wind associated with solar active regions. By tracking the source of these radio waves over periods of days, it is possible to measure the motion of the emission regions. Evidence of solar wind acceleration during this outward flow, consistent with theoretical models, has also been obtained.

  19. Final Report 02-ERD-056 Active Load Control& Mitigation Using Microtabs: A Wind Energy Application

    SciTech Connect

    Nakafuji, D Y

    2003-02-24

    With public concern over the security and reliability of our existing electricity infrastructure and the resurgence of wind energy, the wind industry offers an immediate, first point of entry for the application and demonstration of an active load control technology. An innovative microtab approach is being investigated and demonstrated for active aerodynamic load control applications under the mid-year LDRD (June-Sept. 2002) effort. With many of these million dollar turbines failing at only half the design lifespans, conventional techniques for stiffening rotors, enlarging generators and gearboxes, and reinforcing towers are insufficient to accommodate the demands for bigger, taller and more powerful turbines. The DOE through the National Renewable Energy Laboratory (NREL) supports R&D efforts to develop lighter, more efficient and longer lasting wind turbines and advance turbine components. However, as wind turbine systems continue to increase in size and complexity, fundamental research and technology development has not kept pace with needs. New technologies to increase turbine life spans and to reduce costs are needed to realize wind electricity generation potentials. It is becoming quite evident that without a better understanding of static and dynamic response to normal and abnormal operating loads coupled with sophisticated flow analysis and control techniques, large turbine operating life and component life will be severely limited. Promising technologies include active load control and load alleviation systems to mitigate peak loads from damaging key components. This project addresses science and engineering challenges of developing enabling technologies for active load control for turbine applications using an innovative, translational microtab approach. Figure 1.1 illustrates the microtabs as applied on a wind turbine system. Extending wind turbine operating life is a crucial component for reducing the cost of wind-generated electricity, enabling wind

  20. Workshop on Solar Activity, Solar Wind, Terrestrial Effects, and Solar Acceleration

    NASA Technical Reports Server (NTRS)

    1992-01-01

    A summary of the proceedings from the workshop are presented. The areas covered were solar activity, solar wind, terrestrial effects, and solar acceleration. Specific topics addressed include: (1) solar cycle manifestations, both large and small scale, as well as long-term and short-term changes, including transients such as flares; (2) sources of solar wind, as identified by interplanetary observations including coronal mass ejections (CME's) or x-ray bright points, and the theory for and evolution of large-scale and small-scale structures; (3) magnetosphere responses, as observed by spacecraft, to variable solar wind and transient energetic particle emissions; and (4) origin and propagation of solar cosmic rays as related to solar activity and terrestrial effects, and solar wind coronal-hole relationships and dynamics.

  1. Dynamic response of structure with tuned mass friction damper

    NASA Astrophysics Data System (ADS)

    Pisal, Alka Y.; Jangid, R. S.

    2016-12-01

    The effectiveness of tuned mass friction damper (TMFD) in suppressing the dynamic response of the structure is investigated. The TMFD is a damper which consists of a tuned mass damper (TMD) with linear stiffness and pure friction damper and exhibits non-linear behavior. The response of the single-degree-of-freedom (SDOF) structure with TMFD is investigated under harmonic and seismic ground excitations. The governing equations of motion of the system are derived. The response of the system is obtained by solving the equations of motion, numerically using the state-space method. A parametric study is also conducted to investigate the effects of important parameters such as mass ratio, tuning frequency ratio and slip force on the performance of TMFD. The response of system with TMFD is compared with the response of the system without TMFD. It was found that at a given level of excitation, an optimum value of mass ratio, tuning frequency ratio and damper slip force exist at which the peak displacement of primary structure attains its minimum value. It is also observed that, if the slip force of the damper is appropriately selected, the TMFD can be a more effective and potential device to control undesirable response of the system.

  2. Experimental study of improved HAWT performance in simulated natural wind by an active controlled multi-fan wind tunnel

    NASA Astrophysics Data System (ADS)

    Toshimitsu, Kazuhiko; Narihara, Takahiko; Kikugawa, Hironori; Akiyoshi, Arata; Kawazu, Yuuya

    2017-04-01

    The effects of turbulent intensity and vortex scale of simulated natural wind on performance of a horizontal axis wind turbine (HAWT) are mainly investigated in this paper. In particular, the unsteadiness and turbulence of wind in Japan are stronger than ones in Europe and North America in general. Hence, Japanese engineers should take account of the velocity unsteadiness of natural wind at installed open-air location to design a higher performance wind turbine. Using the originally designed five wind turbines on the basis of NACA and MEL blades, the dependencies of the wind frequency and vortex scale of the simulated natural wind are presented. As the results, the power coefficient of the newly designed MEL3-type rotor in the simulated natural wind is 130% larger than one in steady wind.

  3. Investigation of an energy harvesting MR damper in a vibration control system

    NASA Astrophysics Data System (ADS)

    Sapiński, Bogdan; Rosół, Maciej; Węgrzynowski, Marcin

    2016-12-01

    In this paper the authors investigate the performance of an energy harvesting MR damper (EH-MRD) employed in a semi-active vibration control system (SVCS) and used in a single DOF mechanical structure configuration. Main components of the newly proposed SCVS include the MR damper and an electromagnetic vibration energy harvester based on the Faraday’s law (EVEH) that converts vibration energy into electrical energy and delivers electrical power supplying the MR damper. The main objective of the study is to indicate that the SVCS, controlled by the specially designed embedded system, is feasible and presents good performance at the present stage of the research. The work describes investigation the unique features of the EH-MRD, i.e. its self-powering and self-sensing capabilities. Two cases were considered and the testing was done accordingly. In the case 1, only the self-powered capability was investigated. It was found out that harvested energy is sufficient to power the EH-MRD damper and to adjust it to structural vibration. The results confirmed the adequacy of the SVCS and demonstrated a significant reduction of the resonance peak. In the case 2, both the self-powering and self-sensing capabilities were investigated. Due to the self-sensing capability, the SCVS does not require any sensor. It appeared that thus harvested energy is sufficient to power the EH-MRD and enables self-sensing action since the signal of voltage induced by EVEH agrees with the relative velocity signal across the device. Similar to case 1, the resonance peak is significantly reduced.

  4. NASA Common Research Model Test Envelope Extension With Active Sting Damping at NTF

    NASA Technical Reports Server (NTRS)

    Rivers, Melissa B.; Balakrishna, S.

    2014-01-01

    The NASA Common Research Model (CRM) high Reynolds number transonic wind tunnel testing program was established to generate an experimental database for applied Computational Fluid Dynamics (CFD) validation studies. During transonic wind tunnel tests, the CRM encounters large sting vibrations when the angle of attack approaches the second pitching moment break, which can sometimes become divergent. CRM transonic test data analysis suggests that sting divergent oscillations are related to negative net sting damping episodes associated with flow separation instability. The National Transonic Facility (NTF) has been addressing remedies to extend polar testing up to and beyond the second pitching moment break point of the test articles using an active piezoceramic damper system for both ambient and cryogenic temperatures. This paper reviews CRM test results to gain understanding of sting dynamics with a simple model describing the mechanics of a sting-model system and presents the performance of the damper under cryogenic conditions.

  5. Outdoor temperature, precipitation, and wind speed affect physical activity levels in children: a longitudinal cohort study

    PubMed Central

    Edwards, Nicholas M.; Myer, Gregory D.; Kalkwarf, Heidi J.; Woo, Jessica G.; Khoury, Philip R.; Hewett, Timothy E.; Daniels, Stephen R.

    2015-01-01

    Objective Evaluate effects of local weather conditions on physical activity in early childhood. Methods Longitudinal prospective cohort study of 372 children, 3 years old at enrollment, drawn from a major US metropolitan community. Accelerometer-measured (RT3) physical activity was collected every 4 months over 5 years and matched with daily weather measures: day length, heating/cooling degrees (degrees mean temperature < 65°F or ≥ 65°F, respectively), wind, and precipitation. Mixed regression analyses, adjusted for repeated measures, were used to test the relationship between weather and physical activity. Results Precipitation and wind speed were negatively associated with total physical activity and moderate-vigorous physical activity (P<0.0001). Heating and cooling degrees were negatively associated with total physical activity and moderate-vigorous physical activity and positively associated with inactivity (all P<0.0001), independent of age, sex, race, BMI, day length, wind, and precipitation. For every 10 additional heating degrees there was a five-minute daily reduction in moderate-vigorous physical activity. For every additional 10 cooling degrees there was a 17-minute reduction in moderate-vigorous physical activity. Conclusions Inclement weather (higher/lower temperature, greater wind speed, more rain/snow) is associated with less physical activity in young children. These deleterious effects should be considered when planning physical activity research, interventions, and policies. PMID:25423667

  6. Modeling friction phenomena and elastomeric dampers in multibody dynamics analysis

    NASA Astrophysics Data System (ADS)

    Ju, Changkuan

    The first part of this dissertation focuses on the development, implementation and validation of models that capture the behavior of joints in a realistic manner. These models are presented within the framework of finite element based, nonlinear multibody dynamics formulations that ensure unconditional nonlinear stability of the computation for complex systems of arbitrary topology. The proposed approach can be divided into three parts. First, the joint configuration: this purely kinematic part deals with the description of the configuration of the joint and the evaluation of the relative distance and relative tangential velocity between the contacting bodies. Second, the contact conditions: in most cases, contact at the joint is of an intermittent nature. The enforcement of the unilateral contact condition is a critical aspect of the computational procedure. And finally, the contact forces: this last part deals with the evaluation of the forces that arise at the interface between contacting bodies. The advantage of the proposed approach is that the three parts of the problem can be formulated and implemented independently. Many articulated rotor helicopters use hydraulic dampers, which provide high levels of damping but are also associated with high maintenance costs and difficulties in evaluating their conditions due to the presence of seals, lubricants and numerous moving parts, all operating in a rotating frame. To avoid problems associated with hydraulic dampers, the industry is now switching to elastomeric lead-lag dampers that feature simpler mechanical design, lower part count, and result in "dry" rotors. However, the design of robust elastomeric dampers is hampered by the lack of reliable analytical tools that can be used to predict their damping behavior in the presence of large multi-frequency motions experienced by the rotor and thus the damper. The second part of this dissertation focuses on the development of an elastomeric damper model which predicts

  7. Reverberation Mapping of Accretion Disk Winds in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Mangham, S.

    2015-09-01

    Reverberation mapping is commonly used for determining black holes masses in AGN from the delayed response of the Broad Line Region (BLR) to fluctuations in the intensity of the AGN continuum source. However, it can also be an effective tool for investigating the structure and kinematics of the BLR itself. Much prior work has been performed to simulate the transfer functions associated with a range of basic geometries (e.g. Keplerian disks, Hubble-like outflows, etc). One promising model for the BLR is that the emission lines are formed in an equatorial accretion disk wind. Here, we predict the reverberation signatures expected from such a model, by modifying the radiative transfer and ionisation code Python that has previously been used to model broad absorption line quasars. This allows to account self-consistently for ionization and radiative transfer effects in the predicted BLR response, which are normally ignored in such calculations. We discuss the agreement between our results and prior work and consider the possibility of detecting the signature of rotating equatorial disk winds in observations obtained by velocity-resolved reverberation mapping campaigns.

  8. Hot-bench simulation of the active flexible wing wind-tunnel model

    NASA Technical Reports Server (NTRS)

    Buttrill, Carey S.; Houck, Jacob A.

    1990-01-01

    Two simulations, one batch and one real-time, of an aeroelastically-scaled wind-tunnel model were developed. The wind-tunnel model was a full-span, free-to-roll model of an advanced fighter concept. The batch simulation was used to generate and verify the real-time simulation and to test candidate control laws prior to implementation. The real-time simulation supported hot-bench testing of a digital controller, which was developed to actively control the elastic deformation of the wind-tunnel model. Time scaling was required for hot-bench testing. The wind-tunnel model, the mathematical models for the simulations, the techniques employed to reduce the hot-bench time-scale factors, and the verification procedures are described.

  9. Transitions to chaos in squeeze-film dampers

    NASA Astrophysics Data System (ADS)

    Inayat-Hussain, Jawaid I.; Mureithi, Njuki W.

    2006-09-01

    This work reports on a numerical study undertaken to investigate the imbalance response of a rigid rotor supported by squeeze-film dampers. Two types of damper configurations were considered, namely, dampers without centering springs, and eccentrically operated dampers with centering springs. For a rotor fitted with squeeze-film dampers without centering springs, the study revealed the existence of three regimes of chaotic motion. The route to chaos in the first regime was attributed to a sequence of period-doubling bifurcations of the period-1 (synchronous) rotor response. A period-3 (one-third subharmonic) rotor whirl orbit, which was born from a saddle-node bifurcation, was found to co-exist with the chaotic attractor. The period-3 orbit was also observed to undergo a sequence of period-doubling bifurcations resulting in chaotic vibrations of the rotor. The route to chaos in the third regime of chaotic rotor response, which occurred immediately after the disappearance of the period-3 orbit due to a saddle-node bifurcation, was attributed to a possible boundary crisis. The transitions to chaotic vibrations in the rotor supported by eccentric squeeze-film dampers with centering springs were via the period-doubling cascade and type 3 intermittency routes. The type 3 intermittency transition to chaos was due to an inverse period-doubling bifurcation of the period-2 (one-half subharmonic) rotor response. The unbalance response of the squeeze-film-damper supported rotor presented in this work leads to unique non-synchronous and chaotic vibration signatures. The latter provide some useful insights into the design and development of fault diagnostic tools for rotating machinery that operate in highly nonlinear regimes.

  10. Bumblebees minimize control challenges by combining active and passive modes in unsteady winds

    NASA Astrophysics Data System (ADS)

    Ravi, Sridhar; Kolomenskiy, Dmitry; Engels, Thomas; Schneider, Kai; Wang, Chun; Sesterhenn, Jörn; Liu, Hao

    2016-10-01

    The natural wind environment that volant insects encounter is unsteady and highly complex, posing significant flight-control and stability challenges. It is critical to understand the strategies insects employ to safely navigate in natural environments. We combined experiments on free flying bumblebees with high-fidelity numerical simulations and lower-order modeling to identify the mechanics that mediate insect flight in unsteady winds. We trained bumblebees to fly upwind towards an artificial flower in a wind tunnel under steady wind and in a von Kármán street formed in the wake of a cylinder. Analysis revealed that at lower frequencies in both steady and unsteady winds the bees mediated lateral movement with body roll - typical casting motion. Numerical simulations of a bumblebee in similar conditions permitted the separation of the passive and active components of the flight trajectories. Consequently, we derived simple mathematical models that describe these two motion components. Comparison between the free-flying live and modeled bees revealed a novel mechanism that enables bees to passively ride out high-frequency perturbations while performing active maneuvers at lower frequencies. The capacity of maintaining stability by combining passive and active modes at different timescales provides a viable means for animals and machines to tackle the challenges posed by complex airflows.

  11. Bumblebees minimize control challenges by combining active and passive modes in unsteady winds

    PubMed Central

    Ravi, Sridhar; Kolomenskiy, Dmitry; Engels, Thomas; Schneider, Kai; Wang, Chun; Sesterhenn, Jörn; Liu, Hao

    2016-01-01

    The natural wind environment that volant insects encounter is unsteady and highly complex, posing significant flight-control and stability challenges. It is critical to understand the strategies insects employ to safely navigate in natural environments. We combined experiments on free flying bumblebees with high-fidelity numerical simulations and lower-order modeling to identify the mechanics that mediate insect flight in unsteady winds. We trained bumblebees to fly upwind towards an artificial flower in a wind tunnel under steady wind and in a von Kármán street formed in the wake of a cylinder. Analysis revealed that at lower frequencies in both steady and unsteady winds the bees mediated lateral movement with body roll - typical casting motion. Numerical simulations of a bumblebee in similar conditions permitted the separation of the passive and active components of the flight trajectories. Consequently, we derived simple mathematical models that describe these two motion components. Comparison between the free-flying live and modeled bees revealed a novel mechanism that enables bees to passively ride out high-frequency perturbations while performing active maneuvers at lower frequencies. The capacity of maintaining stability by combining passive and active modes at different timescales provides a viable means for animals and machines to tackle the challenges posed by complex airflows. PMID:27752047

  12. Optimizing of the higher order mode dampers in the 56MHz SRF cavity

    SciTech Connect

    Wu, Q.; Ben-Zvi, I.

    2010-01-27

    Earlier, we reported that a 56 MHz cavity was designed for a luminosity upgrade of the RHIC, and presented the requirements for Higher Order Mode (HOM) damping, the design of the HOM dampers, along with measurements and simulations of the HOM dampers. In this report, we describe our optimization of the dampers performance, and the modifications we made to their original design. We also optimized the number of the HOM dampers, and tested different configurations of locations for them.

  13. Force-electrical characteristics of a novel mini-damper

    NASA Astrophysics Data System (ADS)

    Li, Junhui; Li, Fei; Tian, Qing; Zhou, Can; Xiao, Chengdi; Huang, Liutian; Wang, Wei; Zhu, Wenhui

    2016-10-01

    In order to develop small loading and small damping, a small magneto-rheological fluid (MRF) damper with built-in magnetic coils is researched, and the dynamics model of new mini-damper is established based on testing the mechanical properties of the damper. It is found that the damping landing force adjustable range will be best when the damping gap is 1.5 mm. The loading force of the mini-damper is only 1.95 N-8.25 N by adjusting the coil current from 0 A-0.8 A. The smooth damping force is the third-order function with the current by polynomial fitting of the experimental data. The result of dynamics tests shows hysteresis damping characteristics, and an improved nonlinear dynamic model is proposed by combining with the structure characteristics. The parameters of the improved dynamic model are identified by using parameter identification and regression fitting. It will provide the basis for the application of the mini-MRF damper.

  14. Significant Attenuation of Lightly Damped Resonances Using Particle Dampers

    NASA Technical Reports Server (NTRS)

    Smith, Andrew; LaVerde, Bruce; Hunt, Ron; Knight, Joseph Brent

    2015-01-01

    When equipment designs must perform in a broad band vibration environment it can be difficult to avoid resonances that affect life and performance. This is especially true when an organization seeks to employ an asset from a heritage design in a new, more demanding vibration environment. Particle dampers may be used to provide significant attenuation of lightly damped resonances to assist with such a deployment of assets by including only a very minor set of modifications. This solution may be easier to implement than more traditional attenuation schemes. Furthermore, the cost in additional weight to the equipment can be very small. Complexity may also be kept to a minimum, because the particle dampers do not require tuning. Attenuating the vibratory response with particle dampers may therefore be simpler (in a set it and forget it kind of way) than tuned mass dampers. The paper will illustrate the use of an "equivalent resonance test jig" that can assist designers in verifying the potential resonance attenuation that may be available to them during the early trade stages of the design. An approach is suggested for transforming observed attenuation in the jig to estimated performance in the actual service design. KEY WORDS: Particle Damper, Performance in Vibration Environment, Damping, Resonance, Attenuation, Mitigation of Vibration Response, Response Estimate, Response Verification.

  15. Does it pay to have a damper in a powered ankle prosthesis? A power-energy perspective.

    PubMed

    Eslamy, Mahdy; Grimmer, Martin; Rinderknecht, Stephan; Seyfarth, Andre

    2013-06-01

    In this paper we investigated on peak power (PP) and energy (ER) requirements for different active ankle actuation concepts that can have both elasticity and damping characteristics. A lower PP or ER requirement is an important issue because it will lead to a smaller motor or battery. In addition to spring, these actuation concepts are assumed to have (passive) damper in series (series elastic-damper actuator SEDA) or parallel (parallel elastic-damper actuator PEDA) to the motor. For SEA (series elastic actuator), SEDA and PEDA, we calculated the required minimum motor PP and ER in different human gaits: normal level walking, ascending and descending the stairs. We found that for level walking and ascending the stairs, the SEA concept, and for descending, the SEDA, were the favorable concepts to reduce required minimum PP and ER in comparison to a DD (direct drive) concept. In SEDA concept, the minimum PP could be reduced to half of what SEA would require. Nevertheless, it was found that spring was always required, however damper showed 'task specific' advantages. As a result, if a simple design perspective is in mind, from PP-ER viewpoint, SEA could be the best compromise to be used for different above-mentioned gaits. For SEDA or PEDA concepts, a controllable damper should be used. In addition, our results show that it is beneficial to select spring stiffness in SEA, based on level walking gait. The PP and ER requirements would increase very slightly for stairs ascending, and to some extent (10.5%) for descending as a consequence of this selection. In contrast, stiffness selection based on stair ascending or descending, increases the PP requirements of level walking more noticeably (17-24%).

  16. Mechanical design handbook for elastomers. [the design of elastomer dampers for application in rotating machinery

    NASA Technical Reports Server (NTRS)

    Darlow, M.; Zorzi, E.

    1981-01-01

    A comprehensive guide for the design of elastomer dampers for application in rotating machinery is presented. Theoretical discussions, a step by step procedure for the design of elastomer dampers, and detailed examples of actual elastomer damper applications are included. Dynamic and general physical properties of elastomers are discussed along with measurement techniques.

  17. Design, manufacturing and characterization of aero-elastically scaled wind turbine blades for testing active and passive load alleviation techniques within a ABL wind tunnel

    NASA Astrophysics Data System (ADS)

    Campagnolo, Filippo; Bottasso, Carlo L.; Bettini, Paolo

    2014-06-01

    In the research described in this paper, a scaled wind turbine model featuring individual pitch control (IPC) capabilities, and equipped with aero-elastically scaled blades featuring passive load reduction capabilities (bend-twist coupling, BTC), was constructed to investigate, by means of wind tunnel testing, the load alleviation potential of BTC and its synergy with active load reduction techniques. The paper mainly focus on the design of the aero-elastic blades and their dynamic and static structural characterization. The experimental results highlight that manufactured blades show desired bend-twist coupling behavior and are a first milestone toward their testing in the wind tunnel.

  18. Estimating Sea Surface Salinity and Wind Using Combined Passive and Active L-Band Microwave Observations

    NASA Technical Reports Server (NTRS)

    Yueh, Simon H.; Chaubell, Mario J.

    2012-01-01

    Several L-band microwave radiometer and radar missions have been, or will be, operating in space for land and ocean observations. These include the NASA Aquarius mission and the Soil Moisture Active Passive (SMAP) mission, both of which use combined passive/ active L-band instruments. Aquarius s passive/active L-band microwave sensor has been designed to map the salinity field at the surface of the ocean from space. SMAP s primary objectives are for soil moisture and freeze/thaw detection, but it will operate continuously over the ocean, and hence will have significant potential for ocean surface research. In this innovation, an algorithm has been developed to retrieve simultaneously ocean surface salinity and wind from combined passive/active L-band microwave observations of sea surfaces. The algorithm takes advantage of the differing response of brightness temperatures and radar backscatter to salinity, wind speed, and direction, thus minimizing the least squares error (LSE) measure, which signifies the difference between measurements and model functions of brightness temperatures and radar backscatter. The algorithm uses the conjugate gradient method to search for the local minima of the LSE. Three LSE measures with different measurement combinations have been tested. The first LSE measure uses passive microwave data only with retrieval errors reaching 1 to 2 psu (practical salinity units) for salinity, and 1 to 2 m/s for wind speed. The second LSE measure uses both passive and active microwave data for vertical and horizontal polarizations. The addition of active microwave data significantly improves the retrieval accuracy by about a factor of five. To mitigate the impact of Faraday rotation on satellite observations, the third LSE measure uses measurement combinations invariant under the Faraday rotation. For Aquarius, the expected RMS SSS (sea surface salinity) error will be less than about 0.2 psu for low winds, and increases to 0.3 psu at 25 m/s wind speed

  19. The design of the fundamental mode damper and the HOM dampers for the 56 MHz SRF cavity

    SciTech Connect

    Choi,E.M.; Hahn, H.; Bellavia, S.; Ben-Zvi, I.

    2009-05-04

    A 56 MHz Superconducting RF cavity is under development for the Relativistic Heavy Ion Collider (RHIC) aiming at luminosity enhancement The 56 MHz SRF cavity can adiabatically rebucket the beam from the 28 MHz accelerating cavities, provide shorter bunches and significantly enhance the luminosity. The 56 MHz SRF cavity will be turned on at store, therefore, the fundamental mode should be damped while the beam is injected and accelerated. The feature requires a fundamental mode damper (FD). The mechanical design of the FD is challenging since the fundamental mode damper has to be physically withdrawn while the cavity is turned on. This motion introduces a frequency change of the cavity. Since for stability the cavity frequency must be kept below the beam frequency in this phase, we chose a judicious axial placement of the FD to minimize the frequency shift. Various studies of the FD were done with prototype cavity tests and numerical simulations. The engineering issues were addressed. Higher-order mode (HOM) dampers are necessary for stable operation of RHIC with the 56 MHz SRF cavity. The physics study of the HOM dampers will be presented in the paper. Based on the stability criteria of the cavity, the HOMs are properly damped by having two HOM dampers. The fundamental mode is filtered out by a 5 element high pass filter. The HOMs were identified and the external Q factors were obtained from tests of the prototype cavity and compared to simulations with the CST Microwave Studio{reg_sign} program.

  20. Study on eliminating fire dampers to maintain process confinement

    SciTech Connect

    Walling, R.C.; Patel, J.B.; Strunk, A.J.

    1991-01-01

    The DOE General Design Criteria for the Defense Waste Processing Facility (DWPF) at the Westinghouse Savannah River Site (WSRS) requires the NFPA National Fire Codes to be incorporated into the design and simultaneously maintain process confinement integrity to prevent the release of radioactivity. Although the NFPA Standard for the Installation of Air Conditioning and Ventilation Systems, NFPA 90, requires fire dampers (FD) in HVAC duct penetrations of two hour rated fire barriers, closure of fire dampers at DWPF may compromise the integrity of the process confinement system. This leads to the need for an overall risk assessment to determine the value of 39 fire dampers that are identified later in the study as capable of a confinement system upset.

  1. Study on eliminating fire dampers to maintain process confinement

    SciTech Connect

    Walling, R.C.; Patel, J.B.; Strunk, A.J.

    1991-12-31

    The DOE General Design Criteria for the Defense Waste Processing Facility (DWPF) at the Westinghouse Savannah River Site (WSRS) requires the NFPA National Fire Codes to be incorporated into the design and simultaneously maintain process confinement integrity to prevent the release of radioactivity. Although the NFPA Standard for the Installation of Air Conditioning and Ventilation Systems, NFPA 90, requires fire dampers (FD) in HVAC duct penetrations of two hour rated fire barriers, closure of fire dampers at DWPF may compromise the integrity of the process confinement system. This leads to the need for an overall risk assessment to determine the value of 39 fire dampers that are identified later in the study as capable of a confinement system upset.

  2. A nonlinear auxetic structural vibration damper with metal rubber particles

    NASA Astrophysics Data System (ADS)

    Ma, Yanhong; Scarpa, Fabrizio; Zhang, Dayi; Zhu, Bin; Chen, Lulu; Hong, Jie

    2013-08-01

    The work describes the mechanical performance of a metal rubber particles (MRP) damper design based on an auxetic (negative Poisson’s ratio) cellular configuration. The auxetic damper configuration is constituted by an anti-tetrachiral honeycomb, where the cylinders are filled with the MRP material. The MRP samples have been subjected to quasi-static loading to measure the stiffness and loss factor from the static hysteresis curve. A parametric experimental analysis has been carried out to investigate the effect of relative density and filling percentage on the static performance of the MRP, and to identify design guidelines for best use of MRP devices. An experimental assessment of the integrated auxetic-MRP damper concept has been provided through static and dynamic force response techniques.

  3. Suppression of transverse instability by a digital damper

    SciTech Connect

    Burov, A.; Lebedev, V.; /Fermilab

    2006-06-01

    With cooling, beam phase space density increases, which makes the beam motion intrinsically unstable. To suppress instabilities, dampers are required. With a progress of digital technology, digital dampers are getting to be more and more preferable. Conversion of an analog signal into digital one is described by a linear operator with explicit time dependence. Thus, the analog-digital converter (ADC) does not preserve a signal frequency. Instead, a monochromatic input signal is transformed into a mixture of all possible frequencies, combining the input one with multiples of the sampling frequency. Stability analysis has to include a cross-talk between all these combined frequencies. In this paper, we are analyzing a problem of stability for beam transverse microwave oscillations in a presence of digital damper; the impedance and the space charge are taken into account. The developed formalism is applied for antiproton beam in the Recycler Ring (RR) at Fermilab.

  4. Design and application of squeeze film dampers for turbomachinery stabilization

    NASA Technical Reports Server (NTRS)

    Gunter, E. J.; Barrett, L. E.; Allaire, P. E.

    1975-01-01

    The steady-state transient response of the squeeze film damper bearing was investigated. Both the steady-state and transient equations for the hydrodynamic bearing forces are derived; the steady-state equations were used to determine the damper equivalent stiffness and damping coefficients. These coefficients are used to find the damper configuration which will provide the optimum support characteristics based on a stability analysis of the rotor-bearing system. The effects of end seals and cavitated fluid film are included. The transient analysis of rotor-bearing systems was conducted by coupling the damping and rotor equations and integrating forward in time. The effects of unbalance, cavitation, and retainer springs are included. Methods of determining the stability of a rotor-bearing system under the influence of aerodynamic forces and internal shaft friction are discussed.

  5. Use of inerter devices for weight reduction of tuned mass-dampers for seismic protection of multi-story building: the Tuned Mass-Damper-Interter (TMDI)

    NASA Astrophysics Data System (ADS)

    Giaralis, Agathoklis; Marian, Laurentiu

    2016-04-01

    This paper explores the practical benefits of the recently proposed by the authors tuned mass-damper-inerter (TMDI) visà- vis the classical tuned mass-damper (TMD) for the passive vibration control of seismically excited linearly building structures assumed to respond linearly. Special attention is focused on showcasing that the TMDI requires considerably reduced attached mass/weight to achieve the same vibration suppression level as the classical TMD by exploiting the mass amplification effect of the ideal inerter device. The latter allows for increasing the inertial property of the TMDI without a significant increase to its physical weight. To this end, novel numerical results pertaining to a seismically excited 3-storey frame building equipped with optimally designed TMDIs for various values of attached mass and inertance (i.e., constant of proportionality of the inerter resisting force in mass units) are furnished. The seismic action is modelled by a non-stationary stochastic process compatible with the elastic acceleration response spectrum of the European seismic code (Eurocode 8), while the TMDIs are tuned to minimize the mean square top floor displacement. It is shown that the TMDI achieves the same level of performance as an unconventional "large mass" TMD for seismic protection (i.e., more than 10% of attached mass of the total building mass), by incorporating attached masses similar to the ones used for controlling wind-induced vibrations via TMDs (i.e., 1%-5% of the total building mass). Moreover, numerical data from response history analyses for a suite of Eurocode 8 compatible recorded ground motions further demonstrate that optimally tuned TMDIs for top floor displacement minimization achieve considerable reductions in terms of top floor acceleration and attached mass displacement (stroke) compared to the classical TMD with the same attached mass.

  6. DARHT-II Injector Transients and the Ferrite Damper

    SciTech Connect

    Waldron, Will; Reginato, Lou; Chow, Ken; Houck, Tim; Henestroza, Enrique; Yu, Simon; Kang, Michael; Briggs, Richard

    2006-08-04

    This report summarizes the transient response of the DARHT-II Injector and the design of the ferrite damper. Initial commissioning of the injector revealed a rise time excited 7.8 MHz oscillation on the diode voltage and stalk current leading to a 7.8 MHz modulation of the beam current, position, and energy. Commissioning also revealed that the use of the crowbar to decrease the voltage fall time excited a spectrum of radio frequency modes which caused concern that there might be significant transient RF electric field stresses imposed on the high voltage column insulators. Based on the experience of damping the induction cell RF modes with ferrite, the concept of a ferrite damper was developed to address the crowbar-excited oscillations as well as the rise-time-excited 7.8 MHz oscillations. After the Project decided to discontinue the use of the crowbar, further development of the concept focused exclusively on damping the oscillations excited by the rise time. The design was completed and the ferrite damper was installed in the DARHT-II Injector in February 2006. The organization of this report is as follows. The suite of injector diagnostics are described in Section 2. The data and modeling of the injector transients excited on the rise-time and also by the crowbar are discussed in Section 3; the objective is a concise summary of the present state of understanding. The design of the ferrite damper, and the small scale circuit simulations used to evaluate the ferrite material options and select the key design parameters like the cross sectional area and the optimum gap width, are presented in Section 4. The details of the mechanical design and the installation of the ferrite damper are covered in Section 5. A brief summary of the performance of the ferrite damper following its installation in the injector is presented in Section 6.

  7. Nutation damper for the AMPTE-IRM satellite: Final Report

    NASA Technical Reports Server (NTRS)

    Truckenbrodt, A.; Schultysik, B.; Mehltretter, J. P.

    1983-01-01

    The design, computations, and testing of the nutation damper for the AMPTE-IRM satellite are described. The nutation motions of the satellite excite fluid oscillations in the closed tube system; kinetic energy is destroyed (converted to heat) through tube/fluid friction, constriction of the stream by cross sectional change, and formation of turbulence by stream enlargement. This energy is extracted from the satellite such that nutation is reduced. Tests were carried out in a pendulum testing device and the time constants were calculated. Findings showed that the damper remained within the originally specified values and provided for good dynamic behavior of the satellite.

  8. The "wind of 120 days" and dust storm activity over the Sistan Basin

    NASA Astrophysics Data System (ADS)

    Alizadeh-Choobari, O.; Zawar-Reza, P.; Sturman, A.

    2014-06-01

    Mesoscale features play a critical role in creating the strong "wind of 120 days" common in eastern Iran and western Afghanistan. The Weather Research and Forecasting with Chemistry (WRF/Chem) model is used with the available observations to investigate the "wind of 120 days", dust storm activity over the Sistan Basin, and major sources of dust influencing Iran. The winds are strong from mid-May to mid-September when a persistent high-pressure system over the high mountains of the Hindu Kush in northern Afghanistan, combined with a summertime thermal low over desert lands of eastern Iran and western Afghanistan, produce a strong pressure gradient. The winds become accelerated by the channeling effect of the surrounding orography. A northerly low level jet (LLJ) along the Iran-Afghanistan border has a peak at 300-500 m and is strongest in July with the nighttime monthly averaged wind speed of 20 m s- 1, and extends across a broad latitudinal area along the Iran-Afghanistan border. The strong near-surface wind speed along with the LLJ results in substantial dust emission from the Sistan Basin and subsequent long-range meridional transport. Dried Hamoun Lake in the Sistan Basin contains large amounts of erodible sediment that is required for dust entrainment. The LLJ is persistent throughout the night, but is weakened during the day. A pronounced diurnal cycle in the near-surface wind speed has been identified with a peak in the mid-morning in association with momentum transfer from the jet level down to the surface as the daytime mixed layer evolves.

  9. An Axisymmetric, Hydrodynamical Model for the Torus Wind in Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Dorodnitsyn, A.; Kallman, T.; Proga, D.

    2008-01-01

    We report on time-dependent axisymmetric simulations of an X-ray-excited flow from a parsec-scale, rotating, cold torus around an active galactic nucleus. Our simulations account for radiative heating and cooling and radiation pressure force. The simulations follow the development of a broad biconical outflow induced mainly by X-ray heating. We compute synthetic spectra predicted by our simulations. The wind characteristics and the spectra support the hypothesis that a rotationally supported torus can serve as the source of a wind which is responsible for the warm absorber gas observed in the X-ray spectra of many Seyfert galaxies.

  10. Invention of a tunable damper for use with an acoustic waveguide in hostile environments

    SciTech Connect

    Rogers, S.C.

    1984-06-01

    A damper was invented to remove undesirable stress pulses from an acoustic waveguide. Designed to be tunable, the damper was constructed to withstand a corrosive or otherwise hostile environment. It serves to simplify the design and enhance the performance of a water-level measurement system, of which the damper and acoustic waveguide are integral parts. An experimental damper was constructed and applied to an existing level probe and measurement system. The resulting damper, properly tuned, causes acoustic stress pulses that pass into it along the waveguide to be attenuated.

  11. Magneto-rheological (MR) damper for landing gear system

    NASA Astrophysics Data System (ADS)

    Khani, Mahboubeh

    2010-11-01

    Depending on the different sink speeds, angles of attack and masses; aircraft landing gears could face a wide range of impact conditions which may possibly cause structural damage or failure. Thus, in hard landing scenarios, the landing gear must absorb sufficient energy in order to minimize dynamic stress on the aircraft airframe. Semi-active control systems are the recent potential solutions to overcome these limitations. Among semi-active control strategies, those based on smart fluids such as magneto-rheological (MR) fluids have received recent attraction as their rheological properties can be continuously controlled using magnetic or electric field and they are not sensitive to the contaminants and the temperature variation and also require lower powers. This thesis focuses on modeling of a MR damper for landing gear system and analysis of semi-active controller to attenuate dynamic load and landing impact. First, passive landing gear of a Navy aircraft is modeled and the forces associated with the shock strut are formulated. The passive shock strut is then integrated with a MR valve to design MR shock strut. Here, MR shock strut is integrated with the landing gear system modeled as the 2DOF system and governing equations of motion are derived in order to simulate the dynamics of the system under different impact conditions. Subsequently the inverse model of the MR shock strut relating MR yield stress to the MR shock strut force and strut velocity is formulated. Using the developed governing equations and inverse model, a PID controller is formulated to reduce the acceleration of the system. Controlled performance of the simulated MR landing gear system is demonstrated and compared with that of passive system.

  12. The duelling wind model for the emission line region of active nuclei

    NASA Astrophysics Data System (ADS)

    Smith, M. D.; Raine, D. J.

    1988-09-01

    The consequences of the duelling wind model for the nuclear properties of active galaxies and quasars and for the origins of both nuclear and disk winds are explored. The model predicts a relatively small number of cloud systems with individual clouds having column densities of the order of 10 to the 23rd/sq cm. The line profiles are found to be approximately logarithmic, with both spherical and disk-like radial outflows being possible. Cloud velocities of the order of 10 to the 9th lambda exp 1/2 cm/s are reached, independent of the properties of the nuclear wind which accelerates the clouds. The model also predicts covering factors in the 0.1-1 range.

  13. Structural damage identification in wind turbine blades using piezoelectric active sensing with ultrasonic validation

    SciTech Connect

    Claytor, Thomas N; Ammerman, Curtt N; Park, Gyu Hae; Farinholt, Kevin M; Farrar, Charles R; Atterbury, Marie K

    2010-01-01

    This paper gives a brief overview of a new project at LANL in structural damage identification for wind turbines. This project makes use of modeling capabilities and sensing technology to understand realistic blade loading on large turbine blades, with the goal of developing the technology needed to automatically detect early damage. Several structural health monitoring (SHM) techniques using piezoelectric active materials are being investigated for the development of wireless, low power sensors that interrogate sections of the wind turbine blade using Lamb wave propagation data, frequency response functions (FRFs), and time-series analysis methods. The modeling and sensor research will be compared with extensive experimental testing, including wind tunnel experiments, load and fatigue tests, and ultrasonic scans - on small- to mid-scale turbine blades. Furthermore, this study will investigate the effect of local damage on the global response of the blade by monitoring low-frequency response changes.

  14. Charge States and FIP Bias of the Solar Wind from Coronal Holes, Active Regions, and Quiet Sun

    NASA Astrophysics Data System (ADS)

    Fu, Hui; Madjarska, Maria S.; Xia, LiDong; Li, Bo; Huang, ZhengHua; Wangguan, Zhipeng

    2017-02-01

    Connecting in situ measured solar-wind plasma properties with typical regions on the Sun can provide an effective constraint and test to various solar wind models. We examine the statistical characteristics of the solar wind with an origin in different types of source regions. We find that the speed distribution of coronal-hole (CH) wind is bimodal with the slow wind peaking at ∼400 km s‑1 and the fast at ∼600 km s‑1. An anti-correlation between the solar wind speeds and the O7+/O6+ ion ratio remains valid in all three types of solar wind as well during the three studied solar cycle activity phases, i.e., solar maximum, decline, and minimum. The {N}{Fe}/{N}{{O}} range and its average values all decrease with the increasing solar wind speed in different types of solar wind. The {N}{Fe}/{N}{{O}} range (0.06–0.40, first ionization potential (FIP) bias range 1–7) for active region wind is wider than for CH wind (0.06–0.20, FIP bias range 1–3), while the minimum value of {N}{Fe}/{N}{{O}} (∼ 0.06) does not change with the variation of speed, and it is similar for all source regions. The two-peak distribution of CH wind and the anti-correlation between the speed and O7+/O6+ in all three types of solar wind can be explained qualitatively by both the wave-turbulence-driven and reconnection-loop-opening (RLO) models, whereas the distribution features of {N}{Fe}/{N}{{O}} in different source regions of solar wind can be explained more reasonably by the RLO models.

  15. Analysis of the partially filled viscous ring damper. [application as nutation damper for spinning satellite

    NASA Technical Reports Server (NTRS)

    Alfriend, K. T.

    1973-01-01

    A ring partially filled with a viscous fluid has been analyzed as a nutation damper for a spinning satellite. The fluid has been modelled as a rigid slug of finite length moving in a tube and resisted by a linear viscous force. It is shown that there are two distinct modes of motion, called the spin synchronous mode and the nutation synchronous mode. Time constants for each mode are obtained for both the symmetric and asymmetric satellite. The effects of a stop in the tube and an offset of the ring from the spin axis are also investigated. An analysis of test results is also given including a determination of the effect of gravity on the time constants in the two modes.

  16. Modeling and control of an off-road truck using electrorheological dampers

    NASA Astrophysics Data System (ADS)

    Holzmann, K.; Kemmetmüller, W.; Kugi, A.; Stork, M.; Rosenfeldt, H.; Schneider, S.

    2009-02-01

    This work deals with the mathematical modeling and control of the semi-active suspension of an MAN off-road truck with a payload of 5 tons which comprises electrorheological dampers. Thereby, a cascaded control structure with four controllers for the control of a quarter-car in the inner control loop and a superimposed control strategy for the overall vehicle is used. The main goal of the control strategy is to reduce the motion of the chassis (especially roll, pitch and vertical movement) while increasing driving stability. The capability of the overall control strategy is demonstrated by means of simulation studies and measurement results.

  17. Avoidance of wind farms by harbour seals is limited to pile driving activities.

    PubMed

    Russell, Debbie J F; Hastie, Gordon D; Thompson, David; Janik, Vincent M; Hammond, Philip S; Scott-Hayward, Lindesay A S; Matthiopoulos, Jason; Jones, Esther L; McConnell, Bernie J

    2016-12-01

    As part of global efforts to reduce dependence on carbon-based energy sources there has been a rapid increase in the installation of renewable energy devices. The installation and operation of these devices can result in conflicts with wildlife. In the marine environment, mammals may avoid wind farms that are under construction or operating. Such avoidance may lead to more time spent travelling or displacement from key habitats. A paucity of data on at-sea movements of marine mammals around wind farms limits our understanding of the nature of their potential impacts.Here, we present the results of a telemetry study on harbour seals Phoca vitulina in The Wash, south-east England, an area where wind farms are being constructed using impact pile driving. We investigated whether seals avoid wind farms during operation, construction in its entirety, or during piling activity. The study was carried out using historical telemetry data collected prior to any wind farm development and telemetry data collected in 2012 during the construction of one wind farm and the operation of another.Within an operational wind farm, there was a close-to-significant increase in seal usage compared to prior to wind farm development. However, the wind farm was at the edge of a large area of increased usage, so the presence of the wind farm was unlikely to be the cause.There was no significant displacement during construction as a whole. However, during piling, seal usage (abundance) was significantly reduced up to 25 km from the piling activity; within 25 km of the centre of the wind farm, there was a 19 to 83% (95% confidence intervals) decrease in usage compared to during breaks in piling, equating to a mean estimated displacement of 440 individuals. This amounts to significant displacement starting from predicted received levels of between 166 and 178 dB re 1 μPa(p-p). Displacement was limited to piling activity; within 2 h of cessation of pile driving, seals were distributed as per

  18. Wind from the black-hole accretion disk driving a molecular outflow in an active galaxy.

    PubMed

    Tombesi, F; Meléndez, M; Veilleux, S; Reeves, J N; González-Alfonso, E; Reynolds, C S

    2015-03-26

    Powerful winds driven by active galactic nuclei are often thought to affect the evolution of both supermassive black holes and their host galaxies, quenching star formation and explaining the close relationship between black holes and galaxies. Recent observations of large-scale molecular outflows in ultraluminous infrared galaxies support this quasar-feedback idea, because they directly trace the gas from which stars form. Theoretical models suggest that these outflows originate as energy-conserving flows driven by fast accretion-disk winds. Proposed connections between large-scale molecular outflows and accretion-disk activity in ultraluminous galaxies were incomplete because no accretion-disk wind had been detected. Conversely, studies of powerful accretion-disk winds have until now focused only on X-ray observations of local Seyfert galaxies and a few higher-redshift quasars. Here we report observations of a powerful accretion-disk wind with a mildly relativistic velocity (a quarter that of light) in the X-ray spectrum of IRAS F11119+3257, a nearby (redshift 0.189) optically classified type 1 ultraluminous infrared galaxy hosting a powerful molecular outflow. The active galactic nucleus is responsible for about 80 per cent of the emission, with a quasar-like luminosity of 1.5 × 10(46) ergs per second. The energetics of these two types of wide-angle outflows is consistent with the energy-conserving mechanism that is the basis of the quasar feedback in active galactic nuclei that lack powerful radio jets (such jets are an alternative way to drive molecular outflows).

  19. Seismic design of steel structures with lead-extrusion dampers as knee braces

    SciTech Connect

    Monir, Habib Saeed; Naser, Ali

    2008-07-08

    One of the effective methods in decreasing the seismic response of structure against dynamic loads due to earthquake is using energy dissipating systems. Lead-extrusion dampers (LED) are one of these systems that dissipate energy in to one lead sleeve because of steel rod movement. Hysteresis loops of these dampers are approximately rectangular and acts independent from velocity in frequencies that are in the seismic frequency rang. In this paper lead dampers are considered as knee brace in steel frames and are studied in an economical view. Considering that lead dampers don't clog structural panels, so this characteristic can solve brace problems from architectural view. The behavior of these dampers is compared with the other kind of dampers such as XADAS and TADAS. The results indicate that lead dampers act properly in absorbing the induced energy due to earthquake and good function in controlling seismic movements of multi-story structures.

  20. Passive control of piping vibration by ``Houde damper`` using magnetic damping

    SciTech Connect

    Kobayashi, H.; Aida, S.; Sato, T.

    1995-12-01

    This paper presents the experimental results that demonstrate the vibration suppression effectiveness of a Houde damper. The Houde damper was applied to the actual 3-D piping system to suppress its vibration caused by internal fluid flow, and the amplitude of the vibration was reduced to 1/2 {approximately} 1/10. The Houde damper is a type of dynamic vibration absorber that contains an auxiliary mass and a damping element. The damper that was developed uses an eddy current brake consisting of a pair of permanent magnets and a copper plate which acts as a conductor. A vibration test using a straight piping model was conducted to show that the Houde damper is effective not only in reducing small amplitude vibrations, but large amplitude vibrations as well. Analytical calculations were used to establish that the precise tuning required for effective vibration suppression using a conventional dynamic absorber (that is, a passively tuned mass damper) is not necessary for the Houde damper.

  1. Seismic design of steel structures with lead-extrusion dampers as knee braces

    NASA Astrophysics Data System (ADS)

    monir, Habib Saeed; Naser, Ali

    2008-07-01

    One of the effective methods in decreasing the seismic response of structure against dynamic loads due to earthquake is using energy dissipating systems. Lead-extrusion dampers (LED)are one of these systems that dissipate energy in to one lead sleeve because of steel rod movement. Hysteresis loops of these dampers are approximately rectangular and acts independent from velocity in frequencies that are in the seismic frequency rang. In this paper lead dampers are considered as knee brace in steel frames and are studied in an economical view. Considering that lead dampers don't clog structural panels, so this characteristic can solve brace problems from architectural view. The behavior of these dampers is compared with the other kind of dampers such as XADAS and TADAS. The results indicate that lead dampers act properly in absorbing the induced energy due to earthquake and good function in controlling seismic movements of multi-story structures

  2. Experimental Study on a Tuned-Mass Damper of Offshore for Vibration Reduction

    NASA Astrophysics Data System (ADS)

    Wu, Qiong; Zhao, Xilu; Zheng, Rencheng

    2016-09-01

    With the development of industry, oceanic oil production is one of the most important energy resources. Normally, offshore platform, located in the hostile environment, is easily subjected to unstable environmental loading, such as wind, wave, ice, and earthquake, and it becomes a critical problem to ensure the stability of offshore platform for safely engineering operations. In recent years, tuned-mass damper (TMD) technology has been adopted to reduce vibrations from wind and earthquake influences. Due to the complexity of earthquake excitations, most of researchers were focused on controlling response of structures under wind loads; however, less attention has been put on controlling earthquake response. Therefore, this study concentrates on the seismic reduction of offshore platform by application of a TMD system, and a comprehensively experimental study was processed to validate its effectiveness exposed to different earthquake. A 4-column offshore platform was built according to the actual size of approximately 1:200 ratios, and a TMD system was prepared for the experiment. By the different performance analyses, experimental results indicated that the proposed TMD system can effectively suppress the earthquake stimulus and keep the stability of offshore platform.

  3. The Solar Wind and Geomagnetic Activity as a Function of Time Relative to Corotating Interaction Regions

    NASA Technical Reports Server (NTRS)

    McPherron, Robert L.; Weygand, James

    2006-01-01

    Corotating interaction regions during the declining phase of the solar cycle are the cause of recurrent geomagnetic storms and are responsible for the generation of high fluxes of relativistic electrons. These regions are produced by the collision of a high-speed stream of solar wind with a slow-speed stream. The interface between the two streams is easily identified with plasma and field data from a solar wind monitor upstream of the Earth. The properties of the solar wind and interplanetary magnetic field are systematic functions of time relative to the stream interface. Consequently the coupling of the solar wind to the Earth's magnetosphere produces a predictable sequence of events. Because the streams persist for many solar rotations it should be possible to use terrestrial observations of past magnetic activity to predict future activity. Also the high-speed streams are produced by large unipolar magnetic regions on the Sun so that empirical models can be used to predict the velocity profile of a stream expected at the Earth. In either case knowledge of the statistical properties of the solar wind and geomagnetic activity as a function of time relative to a stream interface provides the basis for medium term forecasting of geomagnetic activity. In this report we use lists of stream interfaces identified in solar wind data during the years 1995 and 2004 to develop probability distribution functions for a variety of different variables as a function of time relative to the interface. The results are presented as temporal profiles of the quartiles of the cumulative probability distributions of these variables. We demonstrate that the storms produced by these interaction regions are generally very weak. Despite this the fluxes of relativistic electrons produced during those storms are the highest seen in the solar cycle. We attribute this to the specific sequence of events produced by the organization of the solar wind relative to the stream interfaces. We also

  4. Superelastic viscous dampers for seismically resilient steel frame structures

    NASA Astrophysics Data System (ADS)

    Ozbulut, O. E.; Meguira, B.

    2014-04-01

    This study proposes a passive control device based on superelastic behavior of shape memory alloys (SMAs) and investigates the device performance for improving response of steel frame structures subjected to multi-level seismic hazards. The device, named as Superelastic Viscous Damper (SVD), exhibits both re-centering and energy-dissipating capabilities and consists of SMA elements and a viscoelastic (VE) damper. SMA elements are mainly used as recentering unit and the viscoelastic damper is employed as energy dissipation unit. The VE damper consists of two layers of VE material bonded with three steel plates. Energy is dissipated through the shear deformation of VE material. Each SMA element forms a continuous loop; wrapping the loops around the outer two plates improves compactness and efficiency. An analytical model of a three-story benchmark steel building with the installed SVDs is developed to determine the response of the structure under a ground motion input. A neuro-fuzzy model is used to capture nonlinear behavior of the SMA elements of the SVD. Nonlinear response history analyses are conducted at MCE level seismic hazard. A suite of 22 ground motion records is employed in dynamic analysis. Peak interstory drift, peak absolute floor acceleration, and residual story drift are selected as the primary demand parameters. Results shows that SVDs can effectively mitigate dynamic response of steel frame structures under strong ground motions and enhance their post-earthquake functionality.

  5. A gun recoil system employing a magnetorheological fluid damper

    NASA Astrophysics Data System (ADS)

    Li, Z. C.; Wang, J.

    2012-10-01

    This research aims to design and control a full scale gun recoil buffering system which works under real firing impact loading conditions. A conventional gun recoil absorber is replaced with a controllable magnetorheological (MR) fluid damper. Through dynamic analysis of the gun recoil system, a theoretical model for optimal design and control of the MR fluid damper for impact loadings is derived. The optimal displacement, velocity and optimal design rules are obtained. By applying the optimal design theory to protect against impact loadings, an MR fluid damper for a full scale gun recoil system is designed and manufactured. An experimental study is carried out on a firing test rig which consists of a 30 mm caliber, multi-action automatic gun with an MR damper mounted to the fixed base through a sliding guide. Experimental buffering results under passive control and optimal control are obtained. By comparison, optimal control is better than passive control, because it produces smaller variation in the recoil force while achieving less displacement of the recoil body. The optimal control strategy presented in this paper is open-loop with no feedback system needed. This means that the control process is sensor-free. This is a great benefit for a buffering system under impact loading, especially for a gun recoil system which usually works in a harsh environment.

  6. Tuned mass damper for integrally bladed turbine rotor

    NASA Technical Reports Server (NTRS)

    Marra, John J. (Inventor)

    1994-01-01

    The invention is directed to a damper ring for damping the natural vibration of the rotor blades of an integrally bladed rocket turbine rotor. The invention consists of an integral damper ring which is fixed to the underside of the rotor blade platform of a turbine rotor. The damper ring includes integral supports which extend radially outwardly therefrom. The supports are located adjacent to the base portion and directly under each blade of the rotor. Vibration damping is accomplished by action of tuned mass damper beams attached at each end to the supports. These beams vibrate at a predetermined frequency during operation. The vibration of the beams enforce a local node of zero vibratory amplitude at the interface between the supports and the beam. The vibration of the beams create forces upon the supports which forces are transmitted through the rotor blade mounting platform to the base of each rotor blade. When these forces attain a predetermined design frequency and magnitude and are directed to the base of the rotor blades, vibration of the rotor blades is effectively counteracted.

  7. Semi Active Control of Civil Structures, Analytical and Numerical Studies

    NASA Astrophysics Data System (ADS)

    Kerboua, M.; Benguediab, M.; Megnounif, A.; Benrahou, K. H.; Kaoulala, F.

    Structural control for civil structures was born out of a need to provide safer and more efficient designs with the reality of limited resources. The purpose of structural control is to absorb and to reflect the energy introduced by dynamic loads such as winds, waves, earthquakes, and traffic. Today, the protection of civil structures from severe dynamic loading is typically achieved by allowing the structures to be damaged. Semi-active control devices, also called "smart" control devices, assume the positive aspects of both the passive and active control devices. A semi-active control strategy is similar to the active control strategy. Only here, the control actuator does not directly apply force to the structure, but instead it is used to control the properties of a passive energy device, a controllable passive damper. Semi-active control strategies can be used in many of the same civil applications as passive and active control. One method of operating smart cable dampers is in a purely passive capacity, supplying the dampers with constant optimal voltage. The advantages to this strategy are the relative simplicity of implementing the control strategy as compared to a smart or active control strategy and that the dampers are more easily optimally tuned in- place, eliminating the need to have passive dampers with unique optimal damping coefficients. This research investigated semi-active control of civil structures for natural hazard mitigation. The research has two components, the seismic protection of buildings and the mitigation of wind-induced vibration in structures. An ideal semi-active motion equation of a composite beam that consists of a cantilever beam bonded with a PZT patch using Hamilton's principle and Galerkin's method was treated. A series R-L and a parallel R-L shunt circuits are coupled into the motion equation respectively by means of the constitutive relation of piezoelectric material and Kirchhoff's law to control the beam vibration. A

  8. Influence of piston and magnetic coils on the field-dependent damping performance of a mixed-mode magnetorheological damper

    NASA Astrophysics Data System (ADS)

    Zeinali, Mohammadjavad; Amri Mazlan, Saiful; Choi, Seung-Bok; Imaduddin, Fitrian; Hamidah Hamdan, Lailatul

    2016-05-01

    This work presents a 2D simulation study of a mixed-mode magnetorheological (MR) damper in which the influence of the geometric elements of the piston and magnetic coil on the MR damper’s performance is investigated by using the Ansoft Maxwell software tool. Four results of the simulation, which are magnetic flux density (B), MR fluid yield stress (τ 0), {τ }0{L}a and W{τ }0{L}a, are used to compare the performance of the MR damper. Multiplication of the yield stress by the active operating mode length ({τ }0{L}a) represents the variable portion of the active (on-state) damping force of the flow mode motion, while the value of W{τ }0{L}a represents the active damping force of the shear mode motion. The contribution of each operating mode (shear and flow) is related to the mixed-mode geometry and piston velocity. Therefore, each operating mode is evaluated separately. In this work, a total of 154 simulations are done in which 74, 20 and 60 simulations are conducted to analyse the effect of the piston radius, coil dimensions (width and length) and coil boundary lengths, respectively, on the performance of the MR damper. The simulation results show that increasing the piston radius can increase the W{τ }0{L}a value and reduce the value. For a given area of magnetic coil housing, a greater housing length in the axial direction of the piston can increase the achieved yield stress of the MR fluid and hence consequently the performance of the MR damper. A minimum boundary length is needed around the magnetic coil in order to attain a supreme magnetic field distribution. However, there is an optimised value for axial coil boundary lengths, which are the lengths of the upper and lower mixed-mode areas.

  9. Self-similar signature of the active solar corona within the inertial range of solar-wind turbulence.

    PubMed

    Kiyani, K; Chapman, S C; Hnat, B; Nicol, R M

    2007-05-25

    We quantify the scaling of magnetic energy density in the inertial range of solar-wind turbulence seen in situ at 1 AU with respect to solar activity. At solar maximum, when the coronal magnetic field is dynamic and topologically complex, we find self-similar scaling in the solar wind, whereas at solar minimum, when the coronal fields are more ordered, we find multifractality. This quantifies the solar-wind signature that is of direct coronal origin and distinguishes it from that of local MHD turbulence, with quantitative implications for coronal heating of the solar wind.

  10. Disk-driven hydromagnetic winds as a key ingredient of active galactic nuclei unification schemes

    NASA Technical Reports Server (NTRS)

    Konigl, Arieh; Kartje, John F.

    1994-01-01

    Centrifugally driven winds from the surfaces of magnetized accretion disks have been recognized as an attractive mechanism of removing the angular momentum of the accreted matter and of producing the bipolar outflows and jets that are often associated with compact astronomical objects. As previously suggested in the context of young stellar objects, such winds have unique observational manifestations stemming from their highly stratified density and velocity structure and from their exposure to the strong continuum radiation field of the compact object. We have applied this scenario to active galactic nuclei (AGNs) and investigated the properties of hydromagnetic outflows that originate within approximately 10(M(sub 8)) pc of the central 10(exp 8)(M(sub 8)) solar mass black hole. On the basis of our results, we propose that hydromagnetic disk-driven winds may underlie the classification of broad-line and narrow-line AGNs (e.g., the Seyfert 1/Seyfert 2 dichotomy) as well as the apparent dearth of luminous Seyfert 2 galaxies. More generally, we demonstrate that such winds could strongly influence the spectral characteristics of Seyfert galaxies, QSOs, and BL Lac objects (BLOs). In our picture, the torus is identified with the outer regions of the wind where dust uplifted from the disk surfaces by gas-grain collisions is embedded in the outflow. Using an efficient radiative transfer code, we show that the infrared emission of Seyfert galaxies and QSOs can be attributed to the reprocessing of the UV/soft X-ray AGN continuum by the dust in the wind and the disk. We demonstrate that the radiation pressure force flattens the dust distribution in objects with comparatively high (but possibly sub-Eddington) bolometric luminosities, and we propose this as one likely reason for the apparent paucity of narrow-line objects among certain high-luminosity AGNs. Using the XSTAR photoionization code, we show that the inner regions of the wind could naturally account for the warm

  11. Generation of reproducible turbulent inflows for wind tunnel applications using active grids

    NASA Astrophysics Data System (ADS)

    Kroeger, Lars; Guelker, Gerd; Peinke, Joachim

    2016-11-01

    Turbulent flows are omnipresent in nature. In the case of wind energy applications, reproducible measurements in situ are quite difficult, therefore research in turbulence demands for experimental setups with reproducible turbulent flow fields. To simulate the situation from the outside in a wind tunnel an active grid can be used. It consists of horizontal and vertical rotating axes with attached square flaps which could be moved individually. This dynamically driven setup and the possibility to repeat the motions of the active grid axes permits to generate reproducible, statistically well defined turbulence with a wide range of statistical behavior. The objective of this work is to create turbulence with two active grids of different dimensions, to establish comparable setups in our available wind tunnel facilities. In this study the wake of the active grids was investigated by high speed PIV and hotwire measurements. To determine the similarities and limitations between the setups of different dimensions the hotwire data is compared using higher order statistics, increment analysis and the power spectra. The PIV data is used to observe spatial correlations and the prevailing length scales in the turbulent wakes. First results regarding this comparison are shown.

  12. Active region plasma outflows as sources of slow/intermediate solar wind

    NASA Astrophysics Data System (ADS)

    van Driel-Gesztelyi, Lidia M.

    2015-08-01

    L. van Driel-Gesztelyi (1,2,3), D. Baker (1), P. Démoulin (2), Culhane, J.L. (1), M.L. DeRosa (4) C.H. Mandrini (5,6), D.H. Brooks (7), A.N. Fazakerley (1), L.K. Harra (1), L. Zhao (7), T.H. Zurbuchen (7), F.A. Nuevo (5,6), A.M. Vásquez (5,6), G.D. Cristiani (5,6) M. Pick (2)1) UCL/MSSL, UK, (2) Paris Observatory, LESIA, CNRS, France, (3) Konkoly Observatory, Hungary, (4) Lockheed Martin Solar and Astrophysics Laboratory, USA, (5) IAFE, CONICET-UBA, Argentina (6) FCEN, UBA, Argentina (7) Dept. of Atmospheric, Oceanic and Earth Sciences, Univ. of Michigan, USAWe analyse plasma upflows of tens of km/s from the edges of solar active regions discovered by Hinode/EIS and investigate whether or not they become outflows, i.e. find their way into the solar wind. We analyse two magnetic configurations: bipolar and quadrupolar and find that the active region plasma may be directly channeled into the solar wind via interchange reconnection at a high-altitude null point above the active region especially when active regions are located besides coronal holes or in a more complex way via multiple reconnections even from under a closed helmet streamer. We relate the solar observations to in-situ slow/intermediate solar wind streams.

  13. Wind for Schools: A National Data and Curricula Development Activity for Schools (Poster)

    SciTech Connect

    Baring-Gould, I.

    2011-05-01

    As the United States dramatically expands wind energy deployment, the industry is challenged with developing a skilled workforce and addressing public resistance. Wind Powering America?s Wind for Schools project addresses these issues by: 1) Developing Wind Application Centers (WACs) at universities; WAC students assist in implementing school wind turbines and participate in wind courses. 2) Installing small wind turbines at community 'host' schools. 3) Implementing teacher training with interactive curricula at each host school.

  14. Active Galaxy Winds from X-ray, Ultraviolet, and Optical Studies of Nearby Seyfert 1s

    NASA Astrophysics Data System (ADS)

    Winter, Lisa M.

    2012-01-01

    Mass outflows or winds from active galaxies may profoundly affect the evolution of their host galaxies by blowing away gas from star forming regions and recycling metals from near-nuclear supernovae into the galaxy disk. Such fundamental properties as the covering fraction, total energy, variability, and distance of these outflows are still unknown. We present new results in an effort to better understand the properties of active galaxy winds based on X-ray, optical, and UV observations of local Seyfert 1s. We show that the covering fraction, indicated through X-ray and optical spectroscopy, is higher than previous studies suggest. We also show new observations in the UV with the Hubble Space Telescope's Cosmic Origins Spectrograph (COS), showing that the UV variability is at a much lower level than X-ray variability. The COS observations also reveal weak Ly-alpha outflows, which were difficult/impossible to detect in previous generations of UV spectrographs.

  15. Aeroservoelastic wind-tunnel investigations using the active flexible wing model - Status and recent accomplishments

    NASA Technical Reports Server (NTRS)

    Noll, Thomas; Perry, Boyd, III; Tiffany, Sherwood; Cole, Stanley; Buttrill, Carey; Adams, William, Jr.; Houck, Jacob; Srinathkumar, S.

    1989-01-01

    This paper describes the status of the joint NASA/Rockwell Active Flexible Wing Wind-Tunnel Test Program. The objectives of the program are to develop and validate the analysis, design and test methodologies required to apply multifunction active control technology for improving aircraft performance and stability. Major tasks of the program include designing digital multiinput/multioutput flutter-suppression and rolling-maneuver-load-alleviation concepts for a flexible full-span wind-tunnel model, obtaining an experimental data base for the basic model and each control concept, and providing comparisons between experimental and analytical results to validate the methodologies. This program is also providing the opportunity to improve real-time simulation techniques and to gain practical experience with digital control law implementation procedures.

  16. Aeroservoelastic wind-tunnel investigations using the Active Flexible Wing Model: Status and recent accomplishments

    NASA Technical Reports Server (NTRS)

    Noll, Thomas E.; Perry, Boyd, III; Tiffany, Sherwood H.; Cole, Stanley R.; Buttrill, Carey S.; Adams, William M., Jr.; Houck, Jacob A.; Srinathkumar, S.; Mukhopadhyay, Vivek; Pototzky, Anthony S.

    1989-01-01

    The status of the joint NASA/Rockwell Active Flexible Wing Wind-Tunnel Test Program is described. The objectives are to develop and validate the analysis, design, and test methodologies required to apply multifunction active control technology for improving aircraft performance and stability. Major tasks include designing digital multi-input/multi-output flutter-suppression and rolling-maneuver-load alleviation concepts for a flexible full-span wind-tunnel model, obtaining an experimental data base for the basic model and each control concept and providing comparisons between experimental and analytical results to validate the methodologies. The opportunity is provided to improve real-time simulation techniques and to gain practical experience with digital control law implementation procedures.

  17. Experimental Results from the Active Aeroelastic Wing Wind Tunnel Test Program

    NASA Technical Reports Server (NTRS)

    Heeg, Jennifer; Spain, Charles V.; Florance, James R.; Wieseman, Carol D.; Ivanco, Thomas G.; DeMoss, Joshua; Silva, Walter A.; Panetta, Andrew; Lively, Peter; Tumwa, Vic

    2005-01-01

    The Active Aeroelastic Wing (AAW) program is a cooperative effort among NASA, the Air Force Research Laboratory and the Boeing Company, encompassing flight testing, wind tunnel testing and analyses. The objective of the AAW program is to investigate the improvements that can be realized by exploiting aeroelastic characteristics, rather than viewing them as a detriment to vehicle performance and stability. To meet this objective, a wind tunnel model was crafted to duplicate the static aeroelastic behavior of the AAW flight vehicle. The model was tested in the NASA Langley Transonic Dynamics Tunnel in July and August 2004. The wind tunnel investigation served the program goal in three ways. First, the wind tunnel provided a benchmark for comparison with the flight vehicle and various levels of theoretical analyses. Second, it provided detailed insight highlighting the effects of individual parameters upon the aeroelastic response of the AAW vehicle. This parameter identification can then be used for future aeroelastic vehicle design guidance. Third, it provided data to validate scaling laws and their applicability with respect to statically scaled aeroelastic models.

  18. Aquarius geophysical model function and combined active passive algorithm for ocean surface salinity and wind retrieval

    NASA Astrophysics Data System (ADS)

    Yueh, Simon; Tang, Wenqing; Fore, Alexander; Hayashi, Akiko; Song, Yuhe T.; Lagerloef, Gary

    2014-08-01

    This paper describes the updated Combined Active-Passive (CAP) retrieval algorithm for simultaneous retrieval of surface salinity and wind from Aquarius' brightness temperature and radar backscatter. Unlike the algorithm developed by Remote Sensing Systems (RSS), implemented in the Aquarius Data Processing System (ADPS) to produce Aquarius standard products, the Jet Propulsion Laboratory's CAP algorithm does not require monthly climatology SSS maps for the salinity retrieval. Furthermore, the ADPS-RSS algorithm fully uses the National Center for Environmental Predictions (NCEP) wind for data correction, while the CAP algorithm uses the NCEP wind only as a constraint. The major updates to the CAP algorithm include the galactic reflection correction, Faraday rotation, Antenna Pattern Correction, and geophysical model functions of wind or wave impacts. Recognizing the limitation of geometric optics scattering, we improve the modeling of the reflection of galactic radiation; the results are better salinity accuracy and significantly reduced ascending-descending bias. We assess the accuracy of CAP's salinity by comparison with ARGO monthly gridded salinity products provided by the Asia-Pacific Data-Research Center (APDRC) and Japan Agency for Marine-Earth Science and Technology (JAMSTEC). The RMS differences between Aquarius CAP and APDRC's or JAMSTEC's ARGO salinities are less than 0.2 psu for most parts of the ocean, except for the regions in the Intertropical Convergence Zone, near the outflow of major rivers and at high latitudes.

  19. Optimum Dynamic Characteristics of Stockbridge Dampers for Dead-End Spans

    NASA Astrophysics Data System (ADS)

    Markiewicz, M.

    1995-11-01

    Stockbridge dampers are commonly used to protect conductors of overhead transmission lines from aeolian vibrations. Standard Stockbridge dampers are designed so that their mechanical impedance matches as closely as possible the optimum damper impedance determined for the cable to be protected. Since the optimum impedance is evaluated assuming that the cable is clamped at its extremity, the optimally tuned standard dampers will work efficiently only when they are mounted near suspension clamps. In some spans, however, conductors are connected to the tower by means of special tension equipment which may influence the efficiency of the mounted standard damper. The present analysis shows that the optimum damper impedance required for such spans (called dead-end spans) differs significantly from the optimum impedance of the standard damper. The reason for this is the dynamic interaction between the tension insulator assembly and the damper itself. This interaction cannot be neglected for vibration frequencies which are close to the resonance frequencies of the tension insulator assembly. This paper presents a method and computational model for the evaluation of the optimum dynamic characteristics of Stockbridge dampers to be mounted near tension insulator assemblies. It also shows how the efficiency of a standard damper used in such spans may be improved by its proper location on a cable.

  20. Performance of RC Structures Equipped with Steel and Aluminium X-Plate Dampers

    NASA Astrophysics Data System (ADS)

    Manchalwar, A.; Bakre, S. V.

    2016-12-01

    The supplementary energy dissipation using dampers represents an efficient technique for the seismic protection of structural system. Also, the optimal damper location in the building helps in reducing damper cost along with maximum response reduction. In this work, an effort has been made to use the X-plate metallic damper made of steel and aluminium for seismic response control. In the first phase of work, the building has been analysed without and with full dampers under real earthquake ground motion. The response quantities such as maximum displacement, max interstory drift, axial force, shear force and bending moment are compared. The results obtained after the analysis shows that the response quantities are reduced significantly thus establishing the effectiveness of damper to dissipate the input seismic energy. It is important to find out the optimal damper location format in the building to improve its efficiency and reduce total cost of dampers to accomplish the max reduction in the response of the building. Therefore, the second phase of work focuses on the optimal location of the damper in the building. To obtain the optimal damper location, the concept of genetic algorithm is used.

  1. Optimal design of a magnetorheological damper used in smart prosthetic knees

    NASA Astrophysics Data System (ADS)

    Gao, Fei; Liu, Yan-Nan; Liao, Wei-Hsin

    2017-03-01

    In this paper, a magnetorheological (MR) damper is optimally designed for use in smart prosthetic knees. The objective of optimization is to minimize the total energy consumption during one gait cycle and weight of the MR damper. Firstly, a smart prosthetic knee employing a DC motor, MR damper and springs is developed based on the kinetics characteristics of human knee during walking. Then the function of the MR damper is analyzed. In the initial stance phase and swing phase, the MR damper is powered off (off-state). While during the late stance phase, the MR damper is powered on to work as a clutch (on-state). Based on the MR damper model as well as the prosthetic knee model, the instantaneous energy consumption of the MR damper is derived in the two working states. Then by integrating in one gait cycle, the total energy consumption is obtained. Particle swarm optimization algorithm is used to optimize the geometric dimensions of MR damper. Finally, a prototype of the optimized MR damper is fabricated and tested with comparison to simulation.

  2. Aeroelastic modeling of the active flexible wing wind-tunnel model

    NASA Technical Reports Server (NTRS)

    Silva, Walter A.; Heeg, Jennifer; Bennett, Robert M.

    1991-01-01

    The primary issues involved in the generation of linear, state-space equations of motion of a flexible wind tunnel model, the Active Flexible Wing (AFW), are discussed. The codes that were used and their inherent assumptions and limitations are also briefly discussed. The application of the CAP-TSD code to the AFW for determination of the model's transonic flutter boundary is included as well.

  3. Vibration mitigation for wind-induced jitter for the Giant Magellan Telescope

    NASA Astrophysics Data System (ADS)

    Glaese, Roger M.; Sheehan, Michael

    2012-09-01

    The Giant Magellan Telescope (GMT) is a planned large terrestrial telescope with a segmented primary mirror with a 24.5 meter overall diameter. Like most terrestrial telescopes, the GMT resides within an enclosure designed to protect the telescope from the elements and to reduce the effects of wind on the optical performance of the telescope. Wind impingement on the telescope causes static deformation and vibration in the telescope structure that affects the alignment and image jitter performance of the telescope. Actively controlled primary mirror segments and a secondary mirror can correct for the static and low frequency portions of the wind effects, but typically the actuators do not have the bandwidth to address higher frequency components of the wind environment. Preliminary analyses on the GMT indicate that the image jitter associated with wind effects meets budgeted allowances but without much margin. Preliminary models show that the bulk of the residual jitter arises from excitation of a small number of modes in the 9 to 12 Hz range. Therefore, as a risk mitigation effort to increase the margin on the wind induced jitter, passive and active vibration mitigation approaches have been examined for the GMT, which will be the focus of this paper. Using a finite element model of the GMT along with wind loading load cases, several passive and active vibration mitigation approaches were analyzed. These approaches include passive approaches such as tuned mass dampers targeting the worst offending modes, and constrained layer damping targeting all of the modes within the troublesome frequency range. Active approaches evaluated include two active damping approaches, one using several reaction mass actuators and the other using active strut type actuators. The results of the study show that although all approaches are successful in reducing the jitter, the active damping approach using reaction mass actuators offers the lightest weight, least implementation impact

  4. The Damper Spring Unit of the Sentinel 1 Solar Array

    NASA Technical Reports Server (NTRS)

    Doejaaren, Frans; Ellenbroek, Marcel

    2012-01-01

    The Damper Spring Unit (DSU, see Figure 1) has been designed to provide the damping required to control the deployment speed of the spring driven solar array deployment in an ARA Mk3 or FRED based Solar Array in situations where the standard application of a damper at the root-hinge is not feasible. The unit consists of four major parts: a main bracket, an eddy current damper, a spring unit, an actuation pulley which is coupled via Kevlar cables to a synchro-pulley of a hinge. The damper slows down the deployment speed and prevents deployment shocks at deployment completion. The spring unit includes 4 springs which overcome the resistances of the damper and the specific DSU control cable loop. This means it can be added to any spring driven deployment system without major modifications of that system. Engineering models of the Sentinel 1 solar array wing have been built to identify the deployment behavior, and to help to determine the optimal pulley ratios of the solar array and to finalize the DSU design. During the functional tests, the behavior proved to be very sensitive for the alignment of the DSU. This was therefore monitored carefully during the qualification program, especially prior to the TV cold testing. During TV "Cold" testing the measured retarding torque exceeded the max. required value: 284 N-mm versus the required 247 N-mm. Although this requirement was not met, the torque balance analysis shows that the 284 N-mm can be accepted, because the spring unit can provide 1.5 times more torque than required. Some functional tests of the DSU have been performed without the eddy current damper attached. It provided input data for the ADAMS solar array wing model. Simulation of the Sentinel-1 deployment (including DSU) in ADAMS allowed the actual wing deployment tests to be limited in both complexity and number of tests. The DSU for the Sentinel-1 solar array was successfully qualified and the flight models are in production.

  5. Parameters influencing the behavior of a new friction damper device

    NASA Astrophysics Data System (ADS)

    Mualla, Imad H.

    2000-04-01

    This work presents a study on the parameters that govern the performance of a new Friction Damper Device (FDD) The device was designed to dissipate seismic input energy and protect buildings from structural and nonstructural damage during moderate and severe earthquakes. The device consists of 3 steel plates that rotate against each other in different directions, and in between these plates, friction pad material discs are inserted. The damper is attached to structures by using inverted Chevron bracing system and in this work pre- stress bars were used as bracing members. The clamping force in the pretensioned bolt controls the frictional moment at the onset of sliding. The device has been tested intensively in order to verify its performance. The experimental program included two phases: (1) Testing the damper alone with Instron machine, examining three different friction-pad materials. (2) Testing a scaled steel frame model with inserted damper device. In both phases the following parameters were tested: forcing frequencies, normal forces, displacement amplitudes, pre-stressing forces and degradation under long-term cyclic excitation. The tests proved that the damper performance is: (1) Independent of forcing frequency within the range of 2 - 7 Hz; (2) Linearly dependent on displacement amplitudes; (3) Linearly dependent on normal forces; (4) Very stable over many cycles. The new device is characterized by the use of special friction pad material, which has been tested for up to 400 and 500 cycles without showing degradation of friction forces more than 5%. Besides, the steel plates were not damaged or scratched so that they can be used for many times. The comparison of results obtained from the experimental and numerical models showed a good agreement. The parameters influencing the frame with FDD were identified in advance by studying the frame's response to static and dynamic loading. The numerical studies demonstrated that the overall frame response was

  6. On the virialization of disk winds: Implications for the black hole mass estimates in active galactic nuclei

    SciTech Connect

    Kashi, Amit; Proga, Daniel; Nagamine, Kentaro; Greene, Jenny; Barth, Aaron J.

    2013-11-20

    Estimating the mass of a supermassive black hole in an active galactic nucleus usually relies on the assumption that the broad line region (BLR) is virialized. However, this assumption seems to be invalid in BLR models that consist of an accretion disk and its wind. The disk is likely Keplerian and therefore virialized. However, beyond a certain point, the wind material must be dominated by an outward force that is stronger than gravity. Here, we analyze hydrodynamic simulations of four different disk winds: an isothermal wind, a thermal wind from an X-ray-heated disk, and two line-driven winds, one with and the other without X-ray heating and cooling. For each model, we determine whether gravity governs the flow properties by computing and analyzing the volume-integrated quantities that appear in the virial theorem: internal, kinetic, and gravitational energies. We find that in the first two models, the winds are non-virialized, whereas the two line-driven disk winds are virialized up to a relatively large distance. The line-driven winds are virialized because they accelerate slowly so that the rotational velocity is dominant and the wind base is very dense. For the two virialized winds, the so-called projected virial factor scales with inclination angle as 1/sin {sup 2} i. Finally, we demonstrate that an outflow from a Keplerian disk becomes unvirialized more slowly when it conserves the gas specific angular momentum, as in the models considered here, than when it conserves the angular velocity, as in the so-called magneto-centrifugal winds.

  7. Computational studies of the effects of active and passive circulation enhancement concepts on wind turbine performance

    NASA Astrophysics Data System (ADS)

    Tongchitpakdee, Chanin

    With the advantage of modern high speed computers, there has been an increased interest in the use of first-principles based computational approaches for the aerodynamic modeling of horizontal axis wind turbine (HAWT). Since these approaches are based on the laws of conservation (mass, momentum, and energy), they can capture much of the physics in great detail. The ability to accurately predict the airloads and power output can greatly aid the designers in tailoring the aerodynamic and aeroelastic features of the configuration. First-principles based analyses are also valuable for developing active means (e.g., circulation control), and passive means (e.g., Gurney flaps) of reducing unsteady blade loads, mitigating stall, and for efficient capture of wind energy leading to more electrical power generation. In this present study, the aerodynamic performance of a wind turbine rotor equipped with circulation enhancement technology (trailing edge blowing or Gurney flaps) is investigated using a three-dimensional unsteady viscous flow analysis. The National Renewable Energy Laboratory (NREL) Phase VI horizontal axis wind turbine is chosen as the baseline configuration. Prior to its use in exploring these concepts, the flow solver is validated with the experimental data for the baseline case under yawed flow conditions. Results presented include radial distribution of normal and tangential forces, shaft torque, root flap moment, surface pressure distributions at selected radial locations, and power output. Results show that good agreement has been for a range of wind speeds and yaw angles, where the flow is attached. At high wind speeds, however, where the flow is fully separated, it was found that the fundamental assumptions behind this present methodology breaks down for the baseline turbulence model (Spalart-Allmaras model), giving less accurate results. With the implementation of advanced turbulence model, Spalart-Allmaras Detached Eddy Simulation (SA-DES), the

  8. Application of piezoelectric active-sensors for SHM of wind turbine blades

    SciTech Connect

    Park, Gyuhae; Taylor, Stuart G.; Farinholt, Kevin M; Farrar, Charles R

    2010-10-04

    The goal of this study is to characterize the dynamic response of a CX-100 wind blade and the design parameters of SHM techniques as they apply to wind turbine blades, and to investigate the performance of high-frequency active-sensing SHM techniques, including lamb wave and frequency response functions, as a way to monitor the health of a wind turbine blade. The results of the dynamic characterization will be used to validate a numerical model and understand the effect of structural damage on the performance of the blades. The focus of SHM study is to assess and compare the performance of each method in identifying incipient damage, with a special consideration given to field deployability. For experiments, a 9-m CX-100 blade was used. Overall, the methods yielded sufficient damage detection to warrant further investigation into field deployment. This paper also summarizes the SHM results of a full-scale fatigue test of 9-m CX-100 blade using piezoelectric active-sensors.

  9. Health monitoring of fluid dampers for vibration control of structures: experimental investigation

    NASA Astrophysics Data System (ADS)

    Konstantinidis, Dimitrios; Makris, Nicos; Kelly, James M.

    2014-03-01

    This paper presents results from a comprehensive experimental program on medium-size and large-size fluid dampers in an effort to extract their force output during cyclic loading by simply measuring the strain on the damper housing and the end-spacer. The paper first discusses the stress path within the damper and subsequently via the use of linear elasticity shows that the experimental data obtained with commercially available strain gauges yield a force output of the damper that is in good agreement with the readings from the load cell. The paper then examines the performance of a portable data acquisition system that can be used to collect and transmit data from a damper installed on a bridge to a nearby location. The data show that the proposed arrangement is promising for monitoring in-situ the force output of fluid dampers and detecting possible loss of their energy dissipation capability.

  10. Performance of two-stage fan with larger dampers on first-stage rotor

    NASA Technical Reports Server (NTRS)

    Urasek, D. C.; Cunnan, W. S.; Stevans, W.

    1979-01-01

    The performance of a two stage, high pressure-ratio fan, having large, part-span vibration dampers on the first stage rotor is presented and compared with an identical aerodynamically designed fan having smaller dampers. Comparisons of the data for the two damper configurations show that with increased damper size: (1) very high losses in the damper region reduced overall efficiency of first stage rotor by approximately 3 points, (2) the overall performance of each blade row, downstream of the damper was not significantly altered, although appreciable differences in the radial distributions of various performance parameters were noted, and (3) the lower performance of the first stage rotor decreased the overall fan efficiency more than 1 percentage point.

  11. Implementation of Active Noise Control in a Closed-Circuit Wind Tunnel

    NASA Astrophysics Data System (ADS)

    Kuester, Matthew; White, Edward

    2010-11-01

    Closed return wind tunnels, such as the Klebanoff--Saric Wind Tunnel (KSWT) at Texas A&M University, can provide relatively low freestream turbulence levels but include noise sources that do not exist in flight. This background noise, such as fan and motor noise, can adversely affect boundary-layer transition experiments if the frequencies are in the range of unstable Tollmien-- Schlicting waves. Passive acoustic treatments eliminate most noise propagating downstream from the fan to test section in the KSWT, but measurements showed upstream-traveling tonal noise propagating from the fan into the test section. To eliminate this, an active noise control system utilizing an adaptive filter algorithm was implemented targeting frequencies in the TS band below the planar duct mode cut off. Multiple microphones are used to detect and cancel upstream traveling sound without affecting downstream traveling sound. Microphone measurements are used to document the noise reduction at multiple locations in the test section.

  12. Some experiences using wind-tunnel models in active control studies. [minimization of aeroelastic response

    NASA Technical Reports Server (NTRS)

    Doggett, R. V., Jr.; Abel, I.; Ruhlin, C. L.

    1976-01-01

    A status report and review of wind tunnel model experimental techniques that have been developed to study and validate the use of active control technology for the minimization of aeroelastic response are presented. Modeling techniques, test procedures, and data analysis methods used in three model studies are described. The studies include flutter mode suppression on a delta-wing model, flutter mode suppression and ride quality control on a 1/30-size model of the B-52 CCV airplane, and an active lift distribution control system on a 1/22 size C-5A model.

  13. A nonlinear kinematic and dynamic modeling of Macpherson suspension systems with a magneto-rheological damper

    NASA Astrophysics Data System (ADS)

    Dutta, Saikat; Choi, Seung-Bok

    2016-03-01

    It is well known that Macpherson strut suspension systems are widely used in light and medium weight vehicles. The performance of these suspension systems can be enriched by incorporating magneto-rheological (MR) dampers and an appropriate dynamic model is required in order to find out the ride comfort and other performances properly in the sense of practical environment conditions. Therefore, in this work the kinematic and dynamic modeling of Macpherson strut suspension system with MR damper is presented and its responses are evaluated. The governing equations are formulated using the kinematic properties of the suspension system and adopting Lagrange’s equation. In the formulation of the model, both the rotation of the wheel assembly and the lateral stiffness of the tire are considered to represent the nonlinear characteristic of Macpherson type suspension system. The formulated mathematical model is then compared with equivalent conventional quarter car suspension model and the different dynamic responses such as the displacement of the sprung mass are compared to emphasize the effectiveness of the proposed model. Additionally, in this work the important kinematic properties of suspension system such as camber angle, king-pin angle and track width alteration, which cannot be obtained from conventional quarter car suspension model, are evaluated in time and frequency domains. Finally, vibration control responses of the proposed suspension system are presented in time and frequency domains which are achieved from the semi-active sky-hook controller.

  14. Polar low-speed solar wind at the solar activity maximum

    NASA Astrophysics Data System (ADS)

    Ohmi, T.; Kojima, M.; Yokobe, A.; Tokumaru, M.; Fujiki, K.; Hakamada, K.

    2001-11-01

    The tomographic analysis of interplanetary scintillation (IPS) showed that low-speed winds (<= 370 kms-1) emanated out from the polar region at the last solar activity maximum. In order to investigate the origin of those low-speed winds, we compared the velocity distribution derived from the IPS tomographic analysis to the magnetic field structure derived from the potential field analysis. We found that the polar low-speed winds appeared for a short period just before and after the disappearance of polar open fields. When the polar coronal hole shrank very small before its disappearance, the coronal polar open field was encircled by large-scale closed loops and became super radially diverging field into the interplanetary space. A low-speed region appeared in this diverging polar magnetic field region. This situation is a condition very similar to the compact low-speed streams associated with equatorial active regions, which were found by Kojima et al. [1999]. After the open field regions had disappeared from the pole, the polar regions were occupied with closed loops. These closed loops were overlapped by the magnetic field which fanned out from the midlatitudes. A low-speed streamer located above these closed loops even after the polar open field had disappeared. The velocities of polar low-speed streams before polar hole disappearance were much lower than those after disappearance. This result suggests that the physical conditions to generate much lower speed streams are closely associated with large expansion from small open field regions encircled by large-scale closed loops. Finally, a reliability of the IPS measurement of polar low-speed wind was examined by simulating synthetic IPS observations in hypothetical model polar streams.

  15. Evaluation of Magnetostrictive Shunt Damper Performance Using Iron (Fe)-Gallium (Ga) Alloy

    DTIC Science & Technology

    2013-09-01

    Evaluation of Magnetostrictive Shunt Damper Performance Using Iron (Fe)-Gallium (Ga) Alloy by Andrew James Murray and Dr. JinHyeong Yoo...Aberdeen Proving Ground, MD 21005 ARL-TN-0566 September 2013 Evaluation of Magnetostrictive Shunt Damper Performance Using Iron (Fe... Magnetostrictive Shunt Damper Performance Using Iron (Fe)- Gallium (Ga) Alloy 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6

  16. Higher Order Mode Damper Study of the 56 MHz SRF Cavity

    SciTech Connect

    Choi,E.; Hahn, H.

    2008-08-01

    This report summarizes the study on the higher order mode (HOM) damper for the 56 MHz SRF cavity. The Q factors and frequencies of the HOMs with the HOM damper are measured and compared to the simulation. The high pass filter prototype for rejecting the fundamental mode is designed and tested. The filter measurement is also compared to the simulation. Based on the measurement, a new location of the HOM damper is chosen.

  17. A novel form of damper for turbo-machinery

    NASA Technical Reports Server (NTRS)

    Brown, R. D.; Hart, J. A.

    1987-01-01

    Anti-swirl vanes are used by some manufacturers to delay the full development of half speed circulation in annular clearance spaces. The objective is to reduce the aerodynamic cross-coupling in the forward direction. The novel feature of a jet damper is a number of tangential nozzles discharging against the rotor surface speed. Some preliminary results on a 33.9 Kg rotor demonstrate that significant reductions in amplitude are obtained at the synchronous critical speeds.

  18. Development of Magnetorheological Fluid Elastomeric Dampers for Helicopter Stability Augmentation

    DTIC Science & Technology

    2005-01-01

    Philosophy, 2005 Dissertation directed by: Professor Norman M. Wereley Department of Aerospace Engineering Conventional lag dampers use passive... Engineering at the University of Maryland. A special word of thanks to Dr. Gang Wang, Dr. Jinsong Bao, Dr. Y.T. Choi, Dr. J.H. Yoo, Dr. V.T. Nagaraj...condition, the system response will be easily solved. Using the same ODE solver, the RDES model can also be applied in the MATLAB Simulink program such that

  19. Dynamic behavior of an inherently compensated air squeeze film damper

    NASA Technical Reports Server (NTRS)

    Cunningham, R. E.

    1975-01-01

    Experimental values of damping and stiffness were determined for an externally pressurized, inherently compensated, compressible squeeze-film damper up to excitation frequencies of 36,000 cycles/min. Experimental values of damping were higher than predicted by a small pressure perturbation theory at low squeeze numbers and less than predicted at high squeeze numbers. Experimental values of air film stiffness were less than the theory predicted at low squeeze numbers and much greater at higher squeeze numbers.

  20. Design and experiments of a novel magneto-rheological damper featuring bifold flow mode

    NASA Astrophysics Data System (ADS)

    Kim, Kyongsol; Chen, Zhaobo; Yu, Dong; Rim, Changhyon

    2016-07-01

    This study presents design and fabrication of a novel magneto-rheological (MR) damper with bifold flow mode gap to improve damping performance. The proposed MR damper is featured by inner flow mode gap connected to the outer flow mode gap through the feedback hole. A mathematical model of the damping force is established for the proposed MR damper and the magnetic circuit has been analyzed with the finite element method, which is used to validate the principle of the proposed MR damper. A conventional MR damper is fabricated with the same dimensions (radius, length) of the piston and is experimentally compared to confirm advantages of the proposed MR damper. The mechanical performance of the proposed MR damper is experimentally investigated and compared with the results by mathematical model and finite element analysis. The research results show that the controllable damping force and equivalent damping of the MR damper with bifold flow mode gap are much larger than those of the conventional MR damper.

  1. Sound reduction at a target point inside an enclosed cavity using particle dampers

    NASA Astrophysics Data System (ADS)

    Hu, Li; Shi, Yaogui; Yang, Qiliang; Song, Gangbing

    2016-12-01

    The purpose of this paper is to develop a novel structural damping approach to reduce the sound pressure at a target point inside an enclosed cavity. In this approach, particle dampers filled with either metal or nonmetal particles are used. The dissipation mechanisms of such dampers are primarily related to the friction and collision of particle-wall and particle-particle contacts. In this research, each panel contribution was first analyzed to identify the panel that contributes the most to the target point. The proposed particle dampers were then attached to this panel for sound reduction. In the numerical process, a Particle Dampers Cyclic Iterative Method (PDCIM) was proposed for extracting the damping loss factor of the particle dampers to compute the sound pressure of a target point in the cavity with the particle dampers. For further comparative studies, simulation experiments are conducted for three cases: a case with the particle dampers, a case with the empty particle containers and a case with the equivalent mass. The numerical study found that the case with the particle dampers had the best sound reduction effect. Later, model tests were carried out to validate the numerical results. Experimental test results revealed that the particle dampers are remarkably effective for reducing the sound inside the enclosed cavity.

  2. Seismic performance of RC shear wall structure with novel shape memory alloy dampers in coupling beams

    NASA Astrophysics Data System (ADS)

    Mao, Chenxi; Dong, Jinzhi; Li, Hui; Ou, Jinping

    2012-04-01

    Shear wall system is widely adopted in high rise buildings because of its high lateral stiffness in resisting earthquakes. According to the concept of ductility seismic design, coupling beams in shear wall structure are required to yield prior to the damage of wall limb. However, damage in coupling beams results in repair cost post earthquake and even in some cases it is difficult to repair the coupling beams if the damage is severe. In order to solve this problem, a novel passive SMA damper was proposed in this study. The coupling beams connecting wall limbs are split in the middle, and the dampers are installed between the ends of the two cantilevers. Then the relative flexural deformation of the wall limbs is transferred to the ends of coupling beams and then to the SMA dampers. After earthquakes the deformation of the dampers can recover automatically because of the pseudoelasticity of austenite SMA material. In order to verify the validity of the proposed dampers, seismic responses of a 12-story coupled shear wall with such passive SMA dampers in coupling beams was investigated. The additional stiffness and yielding deformation of the dampers and their ratios to the lateral stiffness and yielding displacements of the wall limbs are key design parameters and were addressed. Analytical results indicate that the displacement responses of the shear wall structure with such dampers are reduced remarkably. The deformation of the structure is concentrated in the dampers and the damage of coupling beams is reduced.

  3. A comparative analysis of passive twin tube and skyhook MRF dampers for motorcycle front suspensions

    NASA Astrophysics Data System (ADS)

    Ahmadian, Mehdi; Gravatt, John

    2004-07-01

    A comparative analysis between conventional passive twin tube dampers and skyhook-controlled magneto-rheological fluid (MRF) dampers for motorcycle front suspensions is provided, based on single axis testing in a damper test rig and suspension performance testing in road trials. Performance motorcycles, while boasting extremely light suspension components and competition-ready performance, have an inherent weakness in comfort, as the suspension systems are designed primarily for racing purposes. Front suspension acceleration and shock loading transmit directly through the front suspension triple clamp into the rider's arms and shoulders, causing rapid fatigue in shoulder muscles. Magneto-rheological fluid dampers and skyhook control systems offer an alternative to conventional sport motorcycle suspensions - both performance and comfort can be combined in the same package. Prototype MRF dampers designed and manufactured specifically for this application require no more space than conventional twin tube designs while adding only 1.7 pounds total weight to the system. The MRF dampers were designed for high controllability and low power consumption, two vital considerations for a motorcycle application. The tests conducted include the dampers' force-velocity curve testing in a damper test rig and suspension performance based on damper position, velocity, and acceleration measurement. Damper test rig results show the MRF dampers have a far greater range of adjustability than the test vehicle's OEM dampers. Combined with a modified sky-hook control system, the MRF dampers can greatly decrease the acceleration and shock loading transmitted to the rider through the handlebars while contributing performance in manners such as anti-dive under braking. Triple clamp acceleration measurements from a variety of staged road conditions, such as sinusoidal wave inputs, will be compared to subjective test-rider field reports to establish a correlation between rider fatigue and the

  4. Transient flows of the solar wind associated with small-scale solar activity in solar minimum

    NASA Astrophysics Data System (ADS)

    Slemzin, Vladimir; Veselovsky, Igor; Kuzin, Sergey; Gburek, Szymon; Ulyanov, Artyom; Kirichenko, Alexey; Shugay, Yulia; Goryaev, Farid

    The data obtained by the modern high sensitive EUV-XUV telescopes and photometers such as CORONAS-Photon/TESIS and SPHINX, STEREO/EUVI, PROBA2/SWAP, SDO/AIA provide good possibilities for studying small-scale solar activity (SSA), which is supposed to play an important role in heating of the corona and producing transient flows of the solar wind. During the recent unusually weak solar minimum, a large number of SSA events, such as week solar flares, small CMEs and CME-like flows were observed and recorded in the databases of flares (STEREO, SWAP, SPHINX) and CMEs (LASCO, CACTUS). On the other hand, the solar wind data obtained in this period by ACE, Wind, STEREO contain signatures of transient ICME-like structures which have shorter duration (<10h), weaker magnetic field strength (<10 nT) and lower proton temperature than usual ICMEs. To verify the assumption that ICME-like transients may be associated with the SSA events we investigated the number of weak flares of C-class and lower detected by SPHINX in 2009 and STEREO/EUVI in 2010. The flares were classified on temperature and emission measure using the diagnostic means of SPHINX and Hinode/EIS and were confronted with the parameters of the solar wind (velocity, density, ion composition and temperature, magnetic field, pitch angle distribution of the suprathermal electrons). The outflows of plasma associated with the flares were identified by their coronal signatures - CMEs (only in few cases) and dimmings. It was found that the mean parameters of the solar wind projected to the source surface for the times of the studied flares were typical for the ICME-like transients. The results support the suggestion that weak flares can be indicators of sources of transient plasma flows contributing to the slow solar wind at solar minimum, although these flows may be too weak to be considered as separate CMEs and ICMEs. The research leading to these results has received funding from the European Union’s Seventh Programme

  5. A novel magnetorheological damper based parallel planar manipulator design

    NASA Astrophysics Data System (ADS)

    Hoyle, A.; Arzanpour, S.; Shen, Y.

    2010-05-01

    This paper presents a novel parallel planar robot design which is low cost and simple in structure. The design addresses some of the problems, such as concentration of excessive load on the links and joints, due to wrong commanding signals being given by the controller. In this application two of the conventional actuators are replaced by magnetorheological (MR) dampers, and only one actuator is used to generate motion. The design paradigm is based on the concept that a moving object 'intuitively' follows the path with minimum resistance to its motion. This implies that virtual adoptable constraints can be used effectively to define motion trajectories. In fact, motion generation and adaptive constraints are two elements essential to implementing this strategy. In this paper, MR dampers are used to provide adjustable constraints and to guide the platform that is moved by the linear motor. The model of the MR dampers is derived using the Bouc-Wen model. This model is then used for manipulator simulation and controller design. Two controllers are developed for this manipulator: (1) a closed loop on/off one and (2) a proportional-derivative controller. Also, three different trajectories are defined and used for both the simulations and experiments. The results indicate a good agreement between the simulations and experiments. The experimental results also demonstrate the capability of the manipulator for following sophisticated trajectories.

  6. Evidence of a Connection Between Active Region Outflows and the Solar Wind

    NASA Astrophysics Data System (ADS)

    Brooks, D. H.; Warren, H. P.

    2012-05-01

    We present new evidence of a connection between active region (AR) outflows and the slow speed solar wind from chemical composition measurements made by the EUV Imaging Spectrometer (EIS) on Hinode. By combining the differential emission measure (DEM) distribution derived using low First Ionization Potential (FIP) elements (Fe and Si) with the modeling of the high FIP element S, we are able to measure the degree of FIP bias in an observed region. We have applied this analysis to the outflow areas of AR 10978 observed in December 2007. Since the results of our study have already been presented by Brooks & Warren (2011), we use this short conference proceeding to show one illustrative example and the methodology in detail. We focus on the western outflow from AR 10978 observed on December 11 and show that the FIP bias of 3.4 matches the value of 3.5 measured in situ three days later at Earth by the Solar Wind Ion Composition Spectrometer (SWICS) on the ACE spacecraft. We consider this to be compelling evidence that the plasma in the outflow region really travels to the slow wind at Earth.

  7. Combined High-Resolution Active and Passive Imaging of Ocean Surface Winds from Aircraft

    NASA Technical Reports Server (NTRS)

    Gasiewski, A. J.; Piepmeier, J. R.; McIntosh, R. E.; Swift, C. T.; Carswell, J. R.; Donnelly, W. J.; Knapp, E.; Westwater, E. R.; Irisov, V. I.; Fedor, L. S.; Vandemark, D. C.

    1997-01-01

    A unique complement of passive and active microwave imaging and sensing instruments for observing ocean surface emission and scattering signatures were integrated onto the NASA Wallops Flight Facility's Orion P-3B aircraft (N426NA) for the purpose of studying the signature of ocean surface winds. The complement included: (1) a, four-band (X, K, Ka, and W) tri-polarimetric scanning radiometer (PSR), (2) a C-band ocean surface scatterometer (CSCAT), (3) a Ka-band conical-scanning polarimetric radiometer (KASPR), (4) a nadir-viewing Ka-band polarimetric radiometer, (KAPOL), (5) a 21- and 31-GHz zenith-viewing cloud and water vapor radiometer (CWVR), and (6) a radar ocean wave spectrometer (ROWS). The above Ocean Winds Imaging (OWI) complement was flown during January-March, 1997 over the Labrador Sea. Conically-scanned brightness temperature and backscatter imagery were observed over open ocean for a variety of wind speeds and cloud conditions. Presented herein are the results of a preliminary intercomparison of data from several of the OWI instruments.

  8. Line-driven disc wind model for ultrafast outflows in active galactic nuclei - scaling with luminosity

    NASA Astrophysics Data System (ADS)

    Nomura, M.; Ohsuga, K.

    2017-03-01

    In order to reveal the origin of the ultrafast outflows (UFOs) that are frequently observed in active galactic nuclei (AGNs), we perform two-dimensional radiation hydrodynamics simulations of the line-driven disc winds, which are accelerated by the radiation force due to the spectral lines. The line-driven winds are successfully launched for the range of MBH = 106-9 M⊙ and ε = 0.1-0.5, and the resulting mass outflow rate (dot{M_w}), momentum flux (dot{p_w}), and kinetic luminosity (dot{E_w}) are in the region containing 90 per cent of the posterior probability distribution in the dot{M}_w-Lbol plane, dot{p}_w-Lbol plane, and dot{E}_w-Lbol plane shown in Gofford et al., where MBH is the black hole mass, ε is the Eddington ratio, and Lbol is the bolometric luminosity. The best-fitting relations in Gofford et al., d log dot{M_w}/d log {L_bol}˜ 0.9, d log dot{p_w}/d log {L_bol}˜ 1.2, and d log dot{E_w}/d log {L_bol}˜ 1.5, are roughly consistent with our results, d log dot{M_w}/d log {L_bol}˜ 9/8, d log dot{p_w}/d log {L_bol}˜ 10/8, and d log dot{E_w}/d log {L_bol}˜ 11/8. In addition, our model predicts that no UFO features are detected for the AGNs with ε ≲ 0.01, since the winds do not appear. Also, only AGNs with MBH ≲ 108 M⊙ exhibit the UFOs when ε ∼ 0.025. These predictions nicely agree with the X-ray observations. These results support that the line-driven disc wind is the origin of the UFOs.

  9. Retrieval of Sea Surface Salinity and Wind from The NASA Soil Moisture Active Passive Mission Data

    NASA Astrophysics Data System (ADS)

    Yueh, S. H.; Fore, A.; Tang, W.; Hayashi, A.

    2015-12-01

    NASA's Soil Moisture Active Passive (SMAP) mission, the first Earth Science Decadal Survey mission, was launched January 31, 2015 to provide high-resolution, frequent-revisit global mapping of soil moisture. SMAP has two instruments, a polarimetric radiometer and a multi-polarization synthetic aperture radar. Both instruments operate at L-band frequencies (~ 1GHz) and share a single 6-m rotating mesh antenna, producing a fixed incidence angle conical scan at 40⁰ across a 1000-km swath and a 2-3 day global revisit. The SMAP SSS and ocean surface wind retrieval algorithm developed at the Jet Propulsion Laboratory leverages the QuikSCAT and Aquarius algorithms to account for the two-look geometry (fore and aft looks from the conical scan) and dual-polarization observations for simultaneous retrieval of SSS and wind speed. The retrieval algorithm has been applied to more than three months of SMAP radiometer data. Comparison with the European Center for Medium-Range Weather Forecasting (ECMWF) wind speed suggests that the SMAP wind speed reaches an accuracy of about 0.7 ms-1. The preliminary assessment of the SMAP SSS products gridded at 50 km spatial resolution and weekly intervals is promising. The spatial patterns of the SSS agree well with climatological distributions, but exhibit several unique spatial and temporal features. The temporal evolutions of freshwater plumes from several major rivers, such as the Amazon, Niger, Congo, Ganges, and Mississippi, are all consistent with the timing of rainy and dry seasons, indicated in the SMAP's soil moisture products. Rigorous accuracy assessment will be performed by comparison with in situ SSS data from buoys and ARGO floats. The SMAP evaluation products will be released to the public prior to November 2015.

  10. Performance of viscoelastic dampers (VED) under various temperatures and application of magnetorheological dampers (MRD) for seismic control of structures

    NASA Astrophysics Data System (ADS)

    Bhatti, Abdul Qadir

    2013-08-01

    A number of studies have been carried out to investigate the performance of viscoelastic dampers (VEDs) and magnetorheological dampers (MRDs) in controlling the seismic response of buildings, but very few of them regarding the effect of temperature on the behavior of those dampers. The energy absorption properties of the VEDs are dependent on the ambient temperature, excitation frequency and strain amplitude. Several mathematical models have been investigated for reproducing the experimental behavior of single degree of freedom VEDs and MEDs. Of these, only the fractional derivative model can reflect the influence of temperature which is, however, so complex that it is difficult to apply in structural analysis. In order to verify the effect of temperature, two case studies of structural element have been conducted: once using VED and once using MRD. Kelvin-Voigt mathematical model applied, they were investigated and after analyzing the results, the force vs. displacement showed that MRD achieved a high force capacity and a better performance than VED. Furthermore, the effect of the temperature in case of VED observed via plotting the dissipated energy hysteresis at different temperatures. These results validate the effect of the temperature as the lower the temperature the more viscous the dashpot element becomes, hence improving damping, but this is up to a specific low temperature.

  11. Digital-flutter-suppression-system investigations for the active flexible wing wind-tunnel model

    NASA Technical Reports Server (NTRS)

    Perry, Boyd, III; Mukhopadhyay, Vivek; Hoadley, Sherwood Tiffany; Cole, Stanley R.; Buttrill, Carey S.

    1990-01-01

    Active flutter suppression control laws were designed, implemented, and tested on an aeroelastically-scaled wind-tunnel model in the NASA Langley Transonic Dynamics Tunnel. One of the control laws was successful in stabilizing the model while the dynamic pressure was increased to 24 percent greater than the measured open-loop flutter boundary. Other accomplishments included the design, implementation, and successful operation of a one-of-a-kind digital controller, the design and use of two simulation methods to support the project, and the development and successful use of a methodology for online controller performance evaluation.

  12. Digital-flutter-suppression-system investigations for the active flexible wing wind-tunnel model

    NASA Technical Reports Server (NTRS)

    Perry, Boyd, III; Mukhopadhyay, Vivek; Hoadley, Sherwood T.; Cole, Stanley R.; Buttrill, Carey S.; Houck, Jacob A.

    1990-01-01

    Active flutter suppression control laws were designed, implemented, and tested on an aeroelastically-scaled wind tunnel model in the NASA Langley Transonic Dynamics Tunnel. One of the control laws was successful in stabilizing the model while the dynamic pressure was increased to 24 percent greater than the measured open-loop flutter boundary. Other accomplishments included the design, implementation, and successful operation of a one-of-a-kind digital controller, the design and use of two simulation methods to support the project, and the development and successful use of a methodology for on-line controller performance evaluation.

  13. Field Test Results from a 10 kW Wind Turbine with Active Flow Control

    NASA Astrophysics Data System (ADS)

    Rice, Thomas; Bychkova, Veronika; Taylor, Keith; Clingman, Dan; Amitay, Michael

    2015-11-01

    Active flow control devices including synthetic jets and dynamic vortex generators were tested on a 10 kW wind turbine at RPI. Previous work has shown that load oscillations caused by dynamic stall could be modified through the use of active flow control by injecting momentum into the flow field near the leading edge of a dynamically pitching model. In this study, this work has been extended to its logical conclusion, field-testing active flow control on a real wind turbine. The blades in the current study have a 0.28m chord and 3.05m span, no twist or taper, and were retrofitted with six synthetic jets on one blade and ten dynamic vortex generators on a second blade. The third blade of this turbine was not modified, in order to serve as a control. Strain gauges were installed on each blade to measure blades' deflection. A simple closed loop control was demonstrated and preliminary results indicate reduced vibrational amplitude. Future testing will be conducted on a larger scale, 600kW machine at NREL, incorporating information collected during this study.

  14. Continuous plasma outflows from the edge of a solar active region as a possible source of solar wind.

    PubMed

    Sakao, Taro; Kano, Ryouhei; Narukage, Noriyuki; Kotoku, Jun'ichi; Bando, Takamasa; Deluca, Edward E; Lundquist, Loraine L; Tsuneta, Saku; Harra, Louise K; Katsukawa, Yukio; Kubo, Masahito; Hara, Hirohisa; Matsuzaki, Keiichi; Shimojo, Masumi; Bookbinder, Jay A; Golub, Leon; Korreck, Kelly E; Su, Yingna; Shibasaki, Kiyoto; Shimizu, Toshifumi; Nakatani, Ichiro

    2007-12-07

    The Sun continuously expels a huge amount of ionized material into interplanetary space as the solar wind. Despite its influence on the heliospheric environment, the origin of the solar wind has yet to be well identified. In this paper, we report Hinode X-ray Telescope observations of a solar active region. At the edge of the active region, located adjacent to a coronal hole, a pattern of continuous outflow of soft-x-ray-emitting plasmas was identified emanating along apparently open magnetic field lines and into the upper corona. Estimates of temperature and density for the outflowing plasmas suggest a mass loss rate that amounts to approximately 1/4 of the total mass loss rate of the solar wind. These outflows may be indicative of one of the solar wind sources at the Sun.

  15. Development of an Active Twist Rotor for Wind: Tunnel Testing (NLPN97-310

    NASA Technical Reports Server (NTRS)

    Cesnik, Carlos E. S.; Shin, SangJoon; Hagood, Nesbitt W., IV

    1998-01-01

    The development of the Active Twist Rotor prototype blade for hub vibration and noise reduction studies is presented in this report. Details of the modeling, design, and manufacturing are explored. The rotor blade is integrally twisted by direct strain actuation. This is accomplished by distributing embedded piezoelectric fiber composites along the span of the blade. The development of the analysis framework for this type of active blade is presented. The requirements for the prototype blade, along with the final design results are also presented. A detail discussion on the manufacturing aspects of the prototype blade is described. Experimental structural characteristics of the prototype blade compare well with design goals, and preliminary bench actuation tests show lower performance than originally predicted. Electrical difficulties with the actuators are also discussed. The presented prototype blade is leading to a complete fully articulated four-blade active twist rotor system for future wind tunnel tests.

  16. Radar observations of magnetospheric activity during extremely quiet solar wind conditions

    NASA Astrophysics Data System (ADS)

    Walker, A. D. M.; Baker, K. B.; Pinnock, M.; Dudeney, J. R.; Rash, J. P. S.

    2002-04-01

    During a period of extremely quiet solar wind conditions from 8 to 10 March 1997, strong activity was observed by the Southern Hemisphere Auroral Radar Experiment Super Dual Auroral Radar Network radars in the Antarctic premidnight ionosphere. This activity took the form of quasiperiodic flow bursts with ionospheric drift velocities exceeding 2 km s-1. Data from the Satellite Experiments Simultaneous with Antarctic Measurements (SESAME) automated geophysical observatories in Antarctica and Defense Meteorological Satellite Program and Polar satellites are used with the radar data to study the convection flow in the southern polar ionosphere at the time of these flow bursts. The study shows that the bursts occurred with an approximate period of 12 min. Their direction was westward, and they were superimposed on a background westward flow. In the premidnight sector this is interpreted as a flow associated with dipolarization of the magnetotail tail field. There is a band of strong particle precipitation associated with the flow bursts. The location suggests that they occur deep in the magnetotail and cannot be associated with any lobe reconnection. They are at a latitude near the region where a viscously driven convection cell is expected to exist, and their sense is that of the return convection flow in such a cell. The results suggest that there is an internal magnetospheric mechanism for sporadic energy release in the magnetotail that need not be associated with changes in solar wind reconnection on the magnetopause.

  17. Could a change in magnetic field geometry cause the break in the wind-activity relation?

    NASA Astrophysics Data System (ADS)

    Vidotto, A. A.; Donati, J.-F.; Jardine, M.; See, V.; Petit, P.; Boisse, I.; Boro Saikia, S.; Hébrard, E.; Jeffers, S. V.; Marsden, S. C.; Morin, J.

    2016-01-01

    Wood et al. suggested that mass-loss rate is a function of X-ray flux (dot{M}∝ F_x^{1.34}) for dwarf stars with Fx ≲ Fx,6 ≡ 106 erg cm-2 s-1. However, more active stars do not obey this relation. These authors suggested that the break at Fx,6 could be caused by significant changes in magnetic field topology that would inhibit stellar wind generation. Here, we investigate this hypothesis by analysing the stars in Wood et al. sample that had their surface magnetic fields reconstructed through Zeeman-Doppler Imaging (ZDI). Although the solar-like outliers in the dot{M} - Fx relation have higher fractional toroidal magnetic energy, we do not find evidence of a sharp transition in magnetic topology at Fx,6. To confirm this, further wind measurements and ZDI observations at both sides of the break are required. As active stars can jump between states with highly toroidal to highly poloidal fields, we expect significant scatter in magnetic field topology to exist for stars with Fx ≳ Fx,6. This strengthens the importance of multi-epoch ZDI observations. Finally, we show that there is a correlation between Fx and magnetic energy, which implies that dot{M} - magnetic energy relation has the same qualitative behaviour as the original dot{M} - Fx relation. No break is seen in any of the Fx - magnetic energy relations.

  18. ERS-1 scatterometer calibration and validation activities at ECMWF. B: From radar backscatter characteristics to wind vector solutions

    NASA Technical Reports Server (NTRS)

    Stoffelen, AD; Anderson, David L. T.; Woiceshyn, Peter M.

    1992-01-01

    Calibration and validation activities for the ERS-1 scatterometer were carried out at ECMWF (European Center for Medium range Weather Forecast) complementary to the 'Haltenbanken' field campaign off the coast of Norway. At a Numerical Weather Prediction (NWP) center a wealth of verifying data is available both in time and space. This data is used to redefine the wind retrieval procedure given the instrumental characteristics. It was found that a maximum likelihood estimation procedure to obtain the coefficients of a reformulated sigma deg to wind relationship should use radar measurements in logarithmic rather than physical space, and use winds as the wind components rather than wind speed and direction. Doing this, a much more accurate transfer function than the one currently operated by ESA was derived. Sigma deg measurement space shows no signature of a separation in an upwind solution cone and a downwind solution cone. As such signature was anticipated in ESA's wind direction ambiguity removal algorithm, reconsideration of the procedure is necessary. Despite the fact that revisions have to be made in the process of wind retrieval; a grid potential is shown for scatterometry in meteorology and climatology.

  19. Recent wind resource characterization activities at the National Renewable Energy Laboratory

    SciTech Connect

    Elliott, D L; Schwartz, M N

    1997-07-01

    The wind resource characterization team at the National Renewable Energy Laboratory (NREL) is working to improve the characterization of the wind resource in many key regions of the world. Tasks undertaken in the past year include: updates to the comprehensive meteorological and geographic data bases used in resource assessments in the US and abroad; development and validation of an automated wind resource mapping procedure; support in producing wind forecasting tools useful to utilities involved in wind energy generation; continued support for recently established wind measurement and assessment programs in the US.

  20. Design and Performance Evaluation of a Rotary Magnetorheological Damper for Unmanned Vehicle Suspension Systems

    PubMed Central

    Lee, Jae-Hoon; Han, Changwan; Ahn, Dongsu; Lee, Jin Kyoo; Park, Sang-Hu; Park, Seonghun

    2013-01-01

    We designed and validated a rotary magnetorheological (MR) damper with a specified damping torque capacity, an unsaturated magnetic flux density (MFD), and a high magnetic field intensity (MFI) for unmanned vehicle suspension systems. In this study, for the rotary type MR damper to have these satisfactory performances, the roles of the sealing location and the cover case curvature of the MR damper were investigated by using the detailed 3D finite element model to reflect asymmetrical shapes and sealing components. The current study also optimized the damper cover case curvature based on the MFD, the MFI, and the weight of the MR damper components. The damping torques, which were computed using the characteristic equation of the MR fluid and the MFI of the MR damper, were 239.2, 436.95, and 576.78 N·m at currents of 0.5, 1, and 1.5 A, respectively, at a disk rotating speed of 10 RPM. These predicted damping torques satisfied the specified damping torque of 475 N·m at 1.5 A and showed errors of less than 5% when compared to experimental measurements from the MR damper manufactured by the proposed design. The current study could play an important role in improving the performance of rotary type MR dampers. PMID:23533366

  1. Design and performance evaluation of a rotary magnetorheological damper for unmanned vehicle suspension systems.

    PubMed

    Lee, Jae-Hoon; Han, Changwan; Ahn, Dongsu; Lee, Jin Kyoo; Park, Sang-Hu; Park, Seonghun

    2013-01-01

    We designed and validated a rotary magnetorheological (MR) damper with a specified damping torque capacity, an unsaturated magnetic flux density (MFD), and a high magnetic field intensity (MFI) for unmanned vehicle suspension systems. In this study, for the rotary type MR damper to have these satisfactory performances, the roles of the sealing location and the cover case curvature of the MR damper were investigated by using the detailed 3D finite element model to reflect asymmetrical shapes and sealing components. The current study also optimized the damper cover case curvature based on the MFD, the MFI, and the weight of the MR damper components. The damping torques, which were computed using the characteristic equation of the MR fluid and the MFI of the MR damper, were 239.2, 436.95, and 576.78 N·m at currents of 0.5, 1, and 1.5 A, respectively, at a disk rotating speed of 10 RPM. These predicted damping torques satisfied the specified damping torque of 475 N·m at 1.5 A and showed errors of less than 5% when compared to experimental measurements from the MR damper manufactured by the proposed design. The current study could play an important role in improving the performance of rotary type MR dampers.

  2. Measurement of the kinematics of two underplatform dampers with different geometry and comparison with numerical simulation

    NASA Astrophysics Data System (ADS)

    Firrone, Christian M.

    2009-06-01

    Underplatform dampers are used as friction damping devices in order to reduce the amplitude of vibrations of blades in turbine rotors. In this paper a study was performed on the forced response of a mock up system which simulates the flexural behaviour of two turbine blades with an interposed underplatform damper. Two different geometries are tested for two different deflection shapes and the dynamic response of the whole system is explained with respect to the damper kinematics. The originality of the work consists in the measurement of the damper displacements by means of a laser Doppler vibrometers (LDV) equipment and in the comparison with the displacements obtained by numerical predictions of a numerical code used for damper design. The strong influence of the rotation of the underplatform damper on the dynamic response is analysed in particular for the in-phase vibration of the two dummy blades. Comparison between calculations and experiments shows that the damper model allows simulating the damper kinematics with good accuracy.

  3. Development of Optimal Viscous Dampers for RC Structures in Near Field Ground Motions

    SciTech Connect

    Puthanpurayil, Arun M.; Reynolds, Paul

    2008-07-08

    Recent researches show that more than 50% of the economic loss in earthquakes is due to damage of non-structural elements: $8 billion loss in the 1989 Loma Prieta earthquake and $18.5 billion in the 1994 Northridge earthquake. An approach to reduce the economic loss during a seismic event without compromising the structural safety aspect is to incorporate special mechanical devices like fluid viscous dampers in the parent structural system. A recent study carried out to assess the efficacy of viscous dampers in reducing nonstructural damage of low, medium and high rise structures shows that; linear dampers are well suited for low rise category whereas the medium and high rise category requires nonlinear dampers. In this paper an analytical approach is adopted to derive the optimal combination of damper design parameters for all the three categories of structure subjected to near field ground motion. Linear time history analysis by direct time integration was carried out for the linear viscous dampers, while the parameters of the nonlinear viscous dampers were obtained using nonlinear modal time history analysis (Fast Nonlinear analysis). The results of the study are presented in the form of a set of design curves which can be used for the initial selection of parameters for Damper design.

  4. Performance evaluation of a novel rotational damper for structural reinforcement steel frames subjected to lateral excitations

    NASA Astrophysics Data System (ADS)

    Sanati, M.; Khadem, S. E.; Mirzabagheri, S.; Sanati, H.; Khosravieh, M. Y.

    2014-03-01

    In this study, a novel rotational damper called a Rotational Friction Viscoelastic Damper (RFVD) is introduced. Some viscoelastic pads are added to the Rotational Friction Damper (RFD) in addition to the friction discs used in this conventional device. Consequently, the amount of energy dissipated by the damper increases in low excitation frequencies. In fact, the input energy to the structure is simultaneously dissipated in the form of friction and heat by frictional discs and viscoelastic pads. In order to compare the performance of this novel damper with the earlier types, a set of experiments were carried out. According to the test results, the RFVD showed a better performance in dissipating input energy to the structure when compared to the RFD. The seismic behavior of steel frames equipped with these dampers was also numerically evaluated based on a nonlinear time history analysis. The numerical results verified the performance of the dampers in increasing the energy dissipation and decreasing the energy input to the structural elements. In order to achieve the maximum dissipated energy, the dampers need to be installed in certain places called critical points in the structure. An appropriate approach is presented to properly find these points. Finally, the performance of the RFVDs installed at these critical points was investigated in comparison to some other configurations and the validity of the suggested method in increasing the energy dissipation was confirmed.

  5. Analytical modeling of a simple passive electromagnetic eddy current friction damper

    NASA Astrophysics Data System (ADS)

    Amjadian, Mohsen; Agrawal, Anil K.

    2016-04-01

    This paper presents analytical modeling of a novel type of passive friction damper for seismic hazard mitigation of structural systems. This seismic protective device, which is termed as Passive Electromagnetic Eddy Current Friction Damper (PEMECFD), utilizes a solid-friction mechanism in parallel with an eddy current damping system to dissipate a larger amount of input seismic energy than that by a device with based on solid friction only. In this passive damper, friction force is produced through a magnetic repulsive action between two permanent magnets (PMs) magnetized in the direction normal to the friction surface. The eddy current damping force in the damper is generated because of the motion of the PMS in the vicinity of a conductor. Friction and eddy current damping parts of the damper are able to produce ideal rectangular and elliptical hysteresis loops individually. Seismic hazard mitigation effectiveness of the proposed damper has been demonstrated through an implementation on a two-degree-of-freedom frame building structure. Numerical results show that the proposed damper is more efficient in dissipating input seismic energy than a Passive Linear Viscous Damper (PLVD) with same force capacity.

  6. Lumped negative stiffness damper for absorption of flexural waves in a rod

    NASA Astrophysics Data System (ADS)

    Balch, Samuel P.; Lakes, Roderic S.

    2017-04-01

    A damper based on negative stiffness from column tilt buckling was used to achieve enhanced mechanical damping of bending vibration of a rod. Damping increased by a factor of three, via a damper column that was only about 0.2% of the mass of the aluminum alloy rod to be damped.

  7. Nonlinear modeling of adaptive magnetorheological landing gear dampers under impact conditions

    NASA Astrophysics Data System (ADS)

    Ahuré Powell, Louise A.; Choi, Young T.; Hu, Wei; Wereley, Norman M.

    2016-11-01

    Adaptive landing gear dampers that can continuously adjust their stroking load in response to various operating conditions have been investigated for improving the landing performance of a lightweight helicopter. In prior work, adaptive magnetorheological (MR) landing gear dampers that maintained a constant peak stroking force of 4000 lbf across sink rates ranging from 6 to 12 ft s-1 were designed, fabricated and successfully tested. In this follow-on effort, it is desired to expand the high end of the sink rate range to hold the peak stroking load constant for sink rates ranging from 6 to 26 ft s-1, thus extending the high end of the speed range from 12 (in the first study) to 26 ft s-1. To achieve this increase, a spring-based relief valve MR landing gear damper was developed. In order to better understand the MR landing gear damper behavior, a modified nonlinear Bingham Plastic model was formulated, and it incorporates Darcy friction, viscous forces across the MR and relief valves to better account for the damper force behavior at higher speeds. In addition, gas pressure inside the MR damper piston is considered so the total damper force includes a gas force. The MR landing gear damper performance is characterized using drop tests, and the experiments are used to validate model predictions data at low and high nominal impact speeds up to 26 ft s-1 (shaft velocity of 9.6 ft s-1).

  8. Bat mortality and activity at a Northern Iowa wind resource area

    USGS Publications Warehouse

    Jain, A.A.; Koford, Rolf R.; Hancock, A.W.; Zenner, G.G.

    2011-01-01

    We examined bat collision mortality, activity and species composition at an 89-turbine wind resource area in farmland of north-central Iowa from mid-Apr. to mid-Dec., 2003 and mid-Mar. to mid-Dec., 2004. We found 30 bats beneath turbines on cleared ground and gravel access areas in 2003 and 45 bats in 2004. After adjusting for search probability, search efficiency and scavenging rate, we estimated total bat mortality at 396 ?? 72 (95 ci) in 2003 and 636 ?? 112 (95 ci) in 2004. Although carcasses were mostly migratory tree bats, we found a considerable proportion of little brown bats (Myotis lucifugus). We recorded 1465 bat echolocation call files at turbine sites ( 34.88 call files/detector-night) and 1536 bat call files at adjacent non-turbine sites ( 36.57 call files/detector-night). Bat activity did not differ significantly between turbine and non-turbine sites. A large proportion of recorded call files were made by Myotis sp. but this may be because we detected activity at ground level only. There was no relationship between types of turbine lights and either collision mortality or echolocation activity. The highest levels of bat echolocation activity and collision mortality were recorded during Jul. and Aug. during the autumn dispersal and migration period. The fatality rates for bats in general and little brown bats in particular were higher at the Top of Iowa Wind Resource Area than at other, comparable studies in the region. Future efforts to study behavior of bats in flight around turbines as well as cumulative impact studies should not ignore non-tree dwelling bats, generally regarded as minimally affected. ?? 2011, American Midland Naturalist.

  9. Observation of Weak Low-ionization Winds in Host Galaxies of Low Luminosity Active Galactic Nuclei at z ~1

    NASA Astrophysics Data System (ADS)

    Yesuf, Hassen; David C. Koo, S. M. Faber, J. Xavier Prochaska, Yicheng Guo, F. S. Liu, Emily C. Cunningham, Alison L. Coil, Puragra Guhathakurta

    2017-01-01

    A key physical manifestation of active galactic nuclei (AGN) feedback is predicted to be powerful galactic winds. However, the relative roles between AGN activity and star formation in driving such winds remain largely unexplored at high redshifts, near the peak of cosmic activity for both. We study winds in 12 X-ray AGN host galaxies at z ~ 1 in the CANDELS fields using deep Keck rest-frame UV spectroscopy. We find, using the low-ionization Fe II 2586 absorption in the stacked spectra, that the AGN show a median centroid velocity shift of -137 km/s and a median velocity dispersion of 103 km/ s. The centroid velocity and the velocity dispersions are obtained from a two component (ISM+wind) absorption line model. For comparison, a star-forming and X-ray undetected galaxies at a similar redshift, matched roughly in stellar mass and galaxy inclination, show the outflows to have a median centroid velocity of -135 km/s and a median velocity dispersion of 140 km/s. Thus, winds in the AGN are similar in velocities to those found in star-formation-driven winds, and are weak to escape and expel substantial cool gas from galaxies. A joint reanalysis of the z ~ 0.5 AGN sample and our sample yields a centroid velocity of -139 (+48, -87) km/s and a velocity dispersion of 82 (+47,-37) km/s. For the combined sample, about half the total equivalent width of the Fe II 2586 absorption is due to the wind. We do not observe winds with bulk velocities greater than 500 km/s predicted by some AGN feedback models.

  10. Wind for Schools (Poster)

    SciTech Connect

    Baring-Gould, I.

    2010-05-01

    As the United States dramatically expands wind energy deployment, the industry is challenged with developing a skilled workforce and addressing public resistance. Wind Powering America's Wind for Schools project addresses these issues by developing Wind Application Centers (WACs) at universities; WAC students assist in implementing school wind turbines and participate in wind courses, by installing small wind turbines at community "host" schools, by implementing teacher training with interactive curricula at each host school. This poster provides an overview of the first two years of the Wind for Schools project, primarily supporting activities in Colorado, Kansas, Nebraska, South Dakota, Montana, and Idaho.

  11. The advantage of linear viscoelastic material behavior in passive damper design-with application in broad-banded resonance dampers for industrial high-precision motion stages

    NASA Astrophysics Data System (ADS)

    Verbaan, Cornelis A. M.; Peters, Gerrit W. M.; Steinbuch, Maarten

    2017-01-01

    In this paper we demonstrate the advantage of applying viscoelastic materials instead of purely viscous materials as damping medium in mechanical dampers. Although the loss modulus decreases as function of frequency in case of viscoelastic behavior, which can be interpreted as a decrease of damping, the viscoelastic behavior still leads to an increased modal damping for mechanical structures. This advantage holds for inertial-mass-type dampers that are tuned for broad-banded resonance damping. It turns out that an increase of the storage modulus as function of frequency contributes to the effectiveness of mechanical dampers with respect to energy dissipation at different mechanical resonance frequencies. It is shown that this phenomenon is medium specific and is independent of the amount of damper mass.

  12. A new magnetorheological damper with improved displacement differential self-induced ability

    NASA Astrophysics Data System (ADS)

    Hu, Guoliang; Zhou, Wei; Li, Weihua

    2015-08-01

    This work is an extension of our previous study on the development of a linear variable differential sensor (LVDS)-based magnetorheological (MR) damper with self-sensing capability, where a new MR damper integrated with LVDS technology was developed and prototyped, then its self-induced performance under static and dynamic working conditions was experimentally evaluated. The results of the static and dynamic experiments indicated that the self-induced voltage was proportional to the displacement of the damper. Moreover, the damping performance of this new MR damper was also evaluated through an experimental study. Compared with our previous study, the new MR damper performed better in terms of its self-induced sensing ability and damping capacity.

  13. Fuzzy control of shear-mode MR damper under impact force

    NASA Astrophysics Data System (ADS)

    Cho, Jeongmok; Kim, Hyoun Young; Jung, Taegeun; Joh, Joongseon

    2007-01-01

    Recently, a number of researches about linear magnetorheological(MR) damper using valve-mode characteristics of MR fluid have sufficiently undertaken, but researches about rotary MR damper using shear-mode characteristics of MR fluid are not enough. In this paper, we performed vibration control of shear-mode MR damper for unlimited rotating actuator of mobile robot. Also fuzzy logic based vibration control for shear-mode MR damper is suggested. The parameters, like scaling factor of input/output and center of the triangular membership functions associated with the different linguistic variables, are tuned by genetic algorithm. Experimental results demonstrate the effectiveness of the fuzzy-skyhook controller for vibration control of shear-mode MR damper under impact force.

  14. Advancement in energy harvesting magneto-rheological fluid damper: A review

    NASA Astrophysics Data System (ADS)

    Ahamed, Raju; Ferdaus, Md Meftahul; Li, Yancheng

    2016-11-01

    In this paper, a comprehensive review of the present literature on energy generated magnetorheological (MR) fluid based damper, modeling and applications of the MR damper are presented. The review starts with an introduction of the basic of MR fluid and their different modes, consequences with different types of MR fluids based devices, and their relevant applications. Besides, various forms of MR damper and its applications are presented. Following this, the modeling of the MR fluids and the modeling of the MR fluid based damper are deliberated according to arrangement and configurations. Finally, the review ends with the design and advancement issues, performance analysis matters, and analytical modeling of energy generated magnetorheological fluid damper systems.

  15. Study of magnetic activity effects on the thermospheric winds in the low ionosphere. Master`s thesis

    SciTech Connect

    Davila, R.C.

    1994-09-01

    The purpose of this thesis is to examine the effects of magnetic activity on the low latitude F-region thermospheric winds. The F-region (120-1600 km) is a partially ionized medium where O+ and O are the major ion and neutral species, respectively. The thermospheric winds at these altitudes are driven primarily by pressure gradient forces resulting from the solar heating during the day and cooling at night. For this study, the author used measured Fabry-Perot Interferometer (FPI) winds at Arequipa (16.5 deg S, 71.5 deg W) and measured FPI and incoherent Scatter Radar (ISR) winds at Arecibo (18.6 deg N, 66.8 deg W).

  16. COUPLING THE SOLAR DYNAMO AND THE CORONA: WIND PROPERTIES, MASS, AND MOMENTUM LOSSES DURING AN ACTIVITY CYCLE

    SciTech Connect

    Pinto, Rui F.; Brun, Allan Sacha; Grappin, Roland

    2011-08-20

    We study the connections between the Sun's convection zone and the evolution of the solar wind and corona. We let the magnetic fields generated by a 2.5-dimensional (2.5D) axisymmetric kinematic dynamo code (STELEM) evolve in a 2.5D axisymmetric coronal isothermal magnetohydrodynamic code (DIP). The computations cover an 11 year activity cycle. The solar wind's asymptotic velocity varies in latitude and in time in good agreement with the available observations. The magnetic polarity reversal happens at different paces at different coronal heights. Overall the Sun's mass-loss rate, momentum flux, and magnetic braking torque vary considerably throughout the cycle. This cyclic modulation is determined by the latitudinal distribution of the sources of open flux and solar wind and the geometry of the Alfven surface. Wind sources and braking torque application zones also vary accordingly.

  17. Enriched Imperialist Competitive Algorithm for system identification of magneto-rheological dampers

    NASA Astrophysics Data System (ADS)

    Talatahari, Siamak; Rahbari, Nima Mohajer

    2015-10-01

    In the current research, the imperialist competitive algorithm is dramatically enhanced and a new optimization method dubbed as Enriched Imperialist Competitive Algorithm (EICA) is effectively introduced to deal with high non-linear optimization problems. To conduct a close examination of its functionality and efficacy, the proposed metaheuristic optimization approach is actively employed to sort out the parameter identification of two different types of hysteretic Bouc-Wen models which are simulating the non-linear behavior of MR dampers. Two types of experimental data are used for the optimization problems to minutely examine the robustness of the proposed EICA. The obtained results self-evidently demonstrate the high adaptability of EICA to suitably get to the bottom of such non-linear and hysteretic problems.

  18. Simultaneous optimization of force and placement of friction dampers under seismic loading

    NASA Astrophysics Data System (ADS)

    Fleck Fadel Miguel, Letícia; Fleck Fadel Miguel, Leandro; Holdorf Lopez, Rafael

    2016-04-01

    It is known that the use of passive energy-dissipation devices, such as friction dampers, reduces considerably the dynamic response of a structure subjected to earthquake ground motions. Nevertheless, the parameters of each damper and the best placement of these devices remain difficult to determine. Some articles on optimum design of tuned mass dampers and viscous dampers have been published; however, there is a lack of studies on optimization of friction dampers. The main contribution of this article is to propose a methodology to simultaneously optimize the location of friction dampers and their friction forces in structures subjected to seismic loading, to achieve a desired level of reduction in the response. For this purpose, the recently developed backtracking search optimization algorithm (BSA) is employed, which can deal with optimization problems involving mixed discrete and continuous variables. For illustration purposes, two different structures are presented. The first is a six-storey shear building and the second is a transmission line tower. In both cases, the forces and positions of friction dampers are the design variables, while the objective functions are to minimize the interstorey drift for the first case and to minimize the maximum displacement at the top of the tower for the second example. The results show that the proposed method was able to reduce the interstorey drift of the shear building by more than 65% and the maximum displacement at the top of the tower by approximately 55%, with only three friction dampers. The proposed methodology is quite general and it could be recommended as an effective tool for optimum design of friction dampers for structural response control. Thus, this article shows that friction dampers can be designed in a safe and economic way.

  19. Investigation of earthquake factor for optimum tuned mass dampers

    NASA Astrophysics Data System (ADS)

    Nigdeli, Sinan Melih; Bekdaş, Gebrail

    2012-09-01

    In this study the optimum parameters of tuned mass dampers (TMD) are investigated under earthquake excitations. An optimization strategy was carried out by using the Harmony Search (HS) algorithm. HS is a metaheuristic method which is inspired from the nature of musical performances. In addition to the HS algorithm, the results of the optimization objective are compared with the results of the other documented method and the corresponding results are eliminated. In that case, the best optimum results are obtained. During the optimization, the optimum TMD parameters were searched for single degree of freedom (SDOF) structure models with different periods. The optimization was done for different earthquakes separately and the results were compared.

  20. Optimal member damper controller design for large space structures

    NASA Technical Reports Server (NTRS)

    Joshi, S. M.; Groom, N. J.

    1980-01-01

    Consideration is given to the selection of velocity feedback gains for individual dampers for the members of a structurally controlled large flexible space structure. The problem is formulated as an optimal output feedback regulator problem, and necessary conditions are derived for minimizing a quadratic performance function. The diagonal nature of the gain matrix is taken into account, along with knowledge of noise covariances. It is pointed out that the method presented offers a systematic approach to the design of a class of controllers for enhancing structural damping, which have significant potential if used in conjunction with a reduced-order optimal controller for rigid-body modes and selected structural modes.

  1. Dynamic vibration absorber using magnetic spring and damper

    SciTech Connect

    Aida, Y.; Niwa, H.; Miyano, H.; Ozaki, O.; Kitada, Y.

    1995-12-31

    This paper describes a dynamic vibration absorber based on a magnetic spring and damper system. A pair of double cylindrical magnets face each other across a gap, with one magnet fixed to the target structure and the other to the moving mass of the dynamic vibration absorber. The magnetic restoring force characteristics of the proposed system are examined through static loading tests and analysis. The dynamic characteristics are also tested in vibration tests. Furthermore, application of the proposed dynamic vibration absorber to a rotating machinery model demonstrates that the system gives effective two-dimensional vibration control.

  2. 2014 Wind Technologies Market Report

    SciTech Connect

    Wiser, Ryan; Bolinger, Mark; Barbose, Galen; Daghouth, Naim; Hoen, Ben; Mills, Andrew; Hamachi LaCommare, Kristina; Millstein, Dev; Hansen, Dana; Porter, Kevin; Widiss, Rebecca; Buckley, Michael; Oteri, Frank; Smith, Aaron; Tegen, Suzanne

    2015-08-06

    Wind power capacity additions in the United States rebounded in 2014, and continued growth through 2016 is anticipated. Recent and projected near-term growth is supported by the industry’s primary federal incentive—the production tax credit (PTC)—which is available for projects that began construction by the end of 2014. Wind additions are also being driven by recent improvements in the cost and performance of wind power technologies, which have resulted in the lowest power sales prices ever seen in the U.S. wind sector. Growing corporate demand for wind energy and state-level policies play important roles as well. Expectations for continued technological advancements and cost reductions may further boost future growth. At the same time, the prospects for growth beyond 2016 are uncertain. The PTC has expired, and its renewal remains in question. Continued low natural gas prices, modest electricity demand growth, and limited near-term demand from state renewables portfolio standards (RPS) have also put a damper on growth expectations. These trends, in combination with increasingly global supply chains, have limited the growth of domestic manufacturing of wind equipment. What they mean for wind power additions through the end of the decade and beyond will be dictated in part by future natural gas prices, fossil plant retirements, and policy decisions.

  3. Pc3 activity at low geomagnetic latitudes - A comparison with solar wind observations

    NASA Astrophysics Data System (ADS)

    Villante, U.; Lepidi, S.; Vellante, M.; Lazarus, A. J.; Lepping, R. P.

    1992-10-01

    On an hourly time-scale the different roles of the solar wind and interplanetary magnetic field (IMF) parameters on ground micropulsation activity can be better investigated than at longer time-scales. A long-term comparison between ground measurements made at L'Aquila and IMP 8 observations confirms the solar wind speed as the key parameter for the onset of pulsations even at low latitudes, although additional control of the energy transfer from the interplanetary medium to the earth's magnetosphere is clearly exerted by the cone angle. Above about 20 mHz the frequency of pulsations is confirmed to be closely related to the IMF magnitude while, in agreement with model predictions, the IMF magnitude is related to the amplitude of the local fundamental resonant mode. We provide an interesting example in which high resolution measurements simultaneously obtained in the foreshock region and on the ground show that external transversal fluctuations do not penetrate deep into the low latitude magnetosphere.

  4. Pc3 activity at low geomagnetic latitudes - A comparison with solar wind observations

    NASA Technical Reports Server (NTRS)

    Villante, U.; Lepidi, S.; Vellante, M.; Lazarus, A. J.; Lepping, R. P.

    1992-01-01

    On an hourly time-scale the different roles of the solar wind and interplanetary magnetic field (IMF) parameters on ground micropulsation activity can be better investigated than at longer time-scales. A long-term comparison between ground measurements made at L'Aquila and IMP 8 observations confirms the solar wind speed as the key parameter for the onset of pulsations even at low latitudes, although additional control of the energy transfer from the interplanetary medium to the earth's magnetosphere is clearly exerted by the cone angle. Above about 20 mHz the frequency of pulsations is confirmed to be closely related to the IMF magnitude while, in agreement with model predictions, the IMF magnitude is related to the amplitude of the local fundamental resonant mode. We provide an interesting example in which high resolution measurements simultaneously obtained in the foreshock region and on the ground show that external transversal fluctuations do not penetrate deep into the low latitude magnetosphere.

  5. Control Surface Interaction Effects of the Active Aeroelastic Wing Wind Tunnel Model

    NASA Technical Reports Server (NTRS)

    Heeg, Jennifer

    2006-01-01

    This paper presents results from testing the Active Aeroelastic Wing wind tunnel model in NASA Langley s Transonic Dynamics Tunnel. The wind tunnel test provided an opportunity to study aeroelastic system behavior under combined control surface deflections, testing for control surface interaction effects. Control surface interactions were observed in both static control surface actuation testing and dynamic control surface oscillation testing. The primary method of evaluating interactions was examination of the goodness of the linear superposition assumptions. Responses produced by independently actuating single control surfaces were combined and compared with those produced by simultaneously actuating and oscillating multiple control surfaces. Adjustments to the data were required to isolate the control surface influences. Using dynamic data, the task increases, as both the amplitude and phase have to be considered in the data corrections. The goodness of static linear superposition was examined and analysis of variance was used to evaluate significant factors influencing that goodness. The dynamic data showed interaction effects in both the aerodynamic measurements and the structural measurements.

  6. High-resolution wind speed measurements using actively heated fiber optics

    NASA Astrophysics Data System (ADS)

    Sayde, Chadi; Thomas, Christoph K.; Wagner, James; Selker, John

    2015-11-01

    We present a novel technique to simultaneously measure wind speed (U) at thousands of locations continuously in time based on measurement of velocity-dependent heat transfer from a heated surface. Measuring temperature differences between paired passive and actively heated fiber-optic (AHFO) cables with a distributed temperature sensing system allowed estimation of U at over 2000 sections along the 230 m transect (resolution of 0.375 m and 5.5 s). The underlying concept is similar to that of a hot wire anemometer extended in space. The correlation coefficient between U measured by two colocated sonic anemometers and the AHFO were 0.91 during the day and 0.87 at night. The combination of classical passive and novel AHFO provides unprecedented dynamic observations of both air temperature and wind speed spanning 4 orders of magnitude in spatial scale (0.1-1000 m) while resolving individual turbulent motions, opening new opportunities for testing basic theories for near-surface geophysical flows.

  7. Integrated design method of MR damper and electromagnetic induction system for structural control

    NASA Astrophysics Data System (ADS)

    Lee, Heon-Jae; Moon, Seok-Jun; Jung, Hyung-Jo; Huh, Young-Cheol; Jang, Dong-Doo

    2008-03-01

    Magnetorheological (MR) dampers are one of the most advantageous control devices for civil engineering applications to natural hazard mitigation due to many good features such as small power requirement, reliability, and low price to manufacture. To reduce the responses of a structural system by using MR dampers, a control system including a power supply, control algorithm, and sensors is needed. The control system becomes complex, however, when a lot of MR dampers are applied to large-scale civil structures, such as cable-stayed bridges and high-rise buildings. Thus, it is difficult to install and/or maintain the MR damper-based control system. To overcome the above difficulties, a smart passive system was proposed, which is based on an MR damper system. The smart passive system consists of an MR damper and an electromagnetic induction (EMI) system that uses a permanent magnet and a coil. According to the Faraday law of induction, the EMI system that is attached to the MR damper can produce electric energy and the produced energy is applied to the MR damper to vary the damping characteristics of the damper. Thus, the smart passive system does not require any power at all. Besides the output of electric energy is proportional to input loads such as earthquakes, which means the smart passive system has adaptability by itself without any controller or sensors. In this paper, the integrated design method of a large-scale MR damper and Electromagnetic Induction (EMI) system is presented. Since the force of an MR damper is controllable by altering the input current generated from an EMI part, it is necessary to design an MR damper and an EMI part simultaneously. To do this, design parameters of an EMI part consisting of permanent magnet and coil as well as those of an MR damper consisting of a hydraulic-type cylinder and a magnetic circuit that controls the magnetic flux density in a fluid-flow path are considered in the integrated design procedure. As an example, a

  8. WIND1 Promotes Shoot Regeneration through Transcriptional Activation of ENHANCER OF SHOOT REGENERATION1 in Arabidopsis[OPEN

    PubMed Central

    Ohnuma, Mariko; Kurata, Tetsuya; Nakata, Masaru; Ohme-Takagi, Masaru

    2017-01-01

    Many plant species display remarkable developmental plasticity and regenerate new organs after injury. Local signals produced by wounding are thought to trigger organ regeneration but molecular mechanisms underlying this control remain largely unknown. We previously identified an AP2/ERF transcription factor WOUND INDUCED DEDIFFERENTIATION1 (WIND1) as a central regulator of wound-induced cellular reprogramming in plants. In this study, we demonstrate that WIND1 promotes callus formation and shoot regeneration by upregulating the expression of the ENHANCER OF SHOOT REGENERATION1 (ESR1) gene, which encodes another AP2/ERF transcription factor in Arabidopsis thaliana. The esr1 mutants are defective in callus formation and shoot regeneration; conversely, its overexpression promotes both of these processes, indicating that ESR1 functions as a critical driver of cellular reprogramming. Our data show that WIND1 directly binds the vascular system-specific and wound-responsive cis-element-like motifs within the ESR1 promoter and activates its expression. The expression of ESR1 is strongly reduced in WIND1-SRDX dominant repressors, and ectopic overexpression of ESR1 bypasses defects in callus formation and shoot regeneration in WIND1-SRDX plants, supporting the notion that ESR1 acts downstream of WIND1. Together, our findings uncover a key molecular pathway that links wound signaling to shoot regeneration in plants. PMID:28011694

  9. Wind as an abiotic factor of Colorado potato beetle (Coleoptera: Chrysomelidae) flight take-off activity under field conditions.

    PubMed

    Boiteau, G; Mccarthy, P C; MacKinley, P D

    2010-10-01

    The flight take-off activity of Colorado potato beetles, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), was significantly higher at a landscape-protected than at semiexposed and exposed sites in a 2-yr field study. In both years, mean daylight temperature, solar radiation, and relative humidity were generally similar at all sites, but wind speed was lower at the protected site than at the exposed sites. Results suggest that wind was the limiting abiotic factor for flight take-off at the exposed site. Caged beetles exposed to constant wind speeds of 3.4, 4.7, and 7.0 m/s showed a significant corresponding decrease in number of flight take-off. There was no cumulative effect of wind exposure on the readiness of the beetles to fly, suggesting that wind acts as a physical barrier to flight take-off. It should be possible to reduce Colorado potato beetle flight dispersal by selecting fields most exposed to wind over landscape-protected fields when rotating potato, Solanum tuberosum L., crops.

  10. Near-Earth Solar Wind Flows and Related Geomagnetic Activity During more than Four Solar Cycles (1963-2011)

    NASA Technical Reports Server (NTRS)

    Richardson, Ian G.; Cane, Hilary V.

    2012-01-01

    In past studies, we classified the near-Earth solar wind into three basic flow types based on inspection of solar wind plasma and magnetic field parameters in the OMNI database and additional data (e.g., geomagnetic indices, energetic particle, and cosmic ray observations). These flow types are: (1) High-speed streams associated with coronal holes at the Sun, (2) Slow, interstream solar wind, and (3) Transient flows originating with coronal mass ejections at the Sun, including interplanetary coronal mass ejections and the associated upstream shocks and post-shock regions. The solar wind classification in these previous studies commenced with observations in 1972. In the present study, as well as updating this classification to the end of 2011, we have extended the classification back to 1963, the beginning of near-Earth solar wind observations, thereby encompassing the complete solar cycles 20 to 23 and the ascending phase of cycle 24. We discuss the cycle-to-cycle variations in near-Earth solar wind structures and l1e related geomagnetic activity over more than four solar cycles, updating some of the results of our earlier studies.

  11. Coupled CFD/CSD Analysis of an Active-Twist Rotor in a Wind Tunnel with Experimental Validation

    NASA Technical Reports Server (NTRS)

    Massey, Steven J.; Kreshock, Andrew R.; Sekula, Martin K.

    2015-01-01

    An unsteady Reynolds averaged Navier-Stokes analysis loosely coupled with a comprehensive rotorcraft code is presented for a second-generation active-twist rotor. High fidelity Navier-Stokes results for three configurations: an isolated rotor, a rotor with fuselage, and a rotor with fuselage mounted in a wind tunnel, are compared to lifting-line theory based comprehensive rotorcraft code calculations and wind tunnel data. Results indicate that CFD/CSD predictions of flapwise bending moments are in good agreement with wind tunnel measurements for configurations with a fuselage, and that modeling the wind tunnel environment does not significantly enhance computed results. Actuated rotor results for the rotor with fuselage configuration are also validated for predictions of vibratory blade loads and fixed-system vibratory loads. Varying levels of agreement with wind tunnel measurements are observed for blade vibratory loads, depending on the load component (flap, lag, or torsion) and the harmonic being examined. Predicted trends in fixed-system vibratory loads are in good agreement with wind tunnel measurements.

  12. Solar Wind-Magnetosphere Coupling Influences on Pseudo-Breakup Activity

    NASA Technical Reports Server (NTRS)

    Fillingim, M. O.; Brittnacher, M.; Parks, G. K.; Germany, G. A.; Spann, J. F.

    1998-01-01

    Pseudo-breakups are brief, localized aurora[ arc brightening, which do not lead to a global expansion, are historically observed during the growth phase of substorms. Previous studies have demonstrated that phenomenologically there is very little difference between substorm onsets and pseudo-breakups except for the degree of localization and the absence of a global expansion phase. A key open question is what physical mechanism prevents a pseudo-breakup form expanding globally. Using Polar Ultraviolet Imager (UVI) images, we identify periods of pseudo-breakup activity. Foe the data analyzed we find that most pseudo-breakups occur near local midnight, between magnetic local times of 21 and 03, at magnetic latitudes near 70 degrees, through this value may change by several degrees. While often discussed in the context of substorm growth phase events, pseudo-breakups are also shown to occur during prolonged relatively inactive periods. These quiet time pseudo-breakups can occur over a period of several hours without the development of a significant substorm for at least an hour after pseudo-breakup activity stops. In an attempt to understand the cause of quiet time pseudo-breakups, we compute the epsilon parameter as a measure of the efficiency of solar wind-magnetosphere coupling. It is noted that quiet time pseudo-breakups occur typically when epsilon is low; less than about 50 GW. We suggest that quiet time pseudo-breakups are driven by relatively small amounts of energy transferred to the magnetosphere by the solar wind insufficient to initiate a substorm expansion onset.

  13. Evaluation of Sloped Bottom Tuned Liquid Damper for Reduction of Seismic Response of Tall Buildings

    NASA Astrophysics Data System (ADS)

    Patil, G. R.; Singh, K. D.

    2016-12-01

    Due to migration of people to urban area, high land costs and use of light weight materials modern buildings tend to be taller, lighter and flexible. These buildings possess low damping. This increases the possibility of failure during earthquake ground motion and also affect the serviceability during wind vibrations. Out of many available techniques today, to reduce the response of structure under dynamic loading, Tuned Liquid Damper (TLD) is a recent technique to mitigate seismic response. However TLD has been used to mitigate the wind induced structural vibrations. Flat bottom TLD gives energy back to the structure after event of dynamic loading and it is termed as beating. Beating affects the performance of TLD. Study attempts to analyze the effectiveness of sloped bottom TLD for reducing seismic vibrations of structure. Concept of equivalent flat bottom LD has been used to analyze sloped bottom TLD. Finite element method (EM) is used to model the structure and the liquid in the TLD. MATLAB code is developed to study the response of structure, the liquid sloshing in the tank and the coupled fluid-structure interaction. A ten storey two bay RC frame is analyzed for few inputs of ground motion. A sinusoidal ground motion corresponding to resonance condition with fundamental frequency of frame is analyzed. In the analysis the inherent damping of structure is not considered. Observations from the study shows that sloped bottom TLD uses less amount of liquid than flat bottom TLD. Also observed that efficiency of sloped bottom TLD can be improved if it is properly tuned.

  14. A seat suspension with a rotary magnetorheological damper for heavy duty vehicles

    NASA Astrophysics Data System (ADS)

    Sun, S. S.; Ning, D. H.; Yang, J.; Du, H.; Zhang, S. W.; Li, W. H.

    2016-10-01

    This paper presents the development of an innovative seat suspension working with a rotary magnetorheological (MR) fluid damper. Compared with a conventional linear MR damper, the well-designed rotary MR damper possesses several advantages such as usage reduction of magnetorheological fluid, low sealing requirements and lower costs. This research starts with the introduction of the seat suspension structure and the damper design, followed by the property test of the seat suspension using an MTS machine. The field-dependent property, amplitude-dependent performance, and the frequency-dependent performance of the new seat suspension are measured and evaluated. This research puts emphasis on the evaluation of the vibration reduction capability of the rotary MR damper by using both simulation and experimental methods. Fuzzy logic is chosen to control the rotary MR damper in real time and two different input signals are considered as vibration excitations. The experimental results show that the rotary MR damper under fuzzy logic control is effective in reducing the vibrations.

  15. Medium to long term behavior of MR dampers for structural control

    NASA Astrophysics Data System (ADS)

    Caterino, N.; Azmoodeh, B. M.; Occhiuzzi, A.

    2014-10-01

    The medium to long term behavior of a prototype magnetorheological (MR) damper for structural control of earthquake induced vibrations is investigated herein. Unlike some applications for which MR devices experience frequent dynamic loads, seismic dampers might not be used for most of their life, staying dormant for a long period until an earthquake hits the hosting structure. This work aims to evaluate the effectiveness of a MR damper after years of inactivity. A MR device has been tested twice, first in 2008 and then in 2013, after five years of absolute inactivity. The comparison between the results of the two tests is made in terms of force-displacement loops. It is shown that, after a 5-year rest, only part of the first stroke of the damper is characterized by an unexpected response of the damper. After half a stroke, the damper quickly returned to behave like in 2008, even if a slight non-reversible decrease of the reacting force has been recorded. The latter is found to be more evident (5-7%) for larger currents, less visible in the case of zero magnetic field. From the point of view of civil engineering, this decay of performance is definitely acceptable, being largely bounded within the limits of the uncertainties typically involved and taken into account in the structural design. Finally, starting from a literature review, the paper discusses the possible causes of the observed changes in the mechanical response of the damper over time.

  16. A mechanical energy harvested magnetorheological damper with linear-rotary motion converter

    NASA Astrophysics Data System (ADS)

    Chu, Ki Sum; Zou, Li; Liao, Wei-Hsin

    2016-04-01

    Magnetorheological (MR) dampers are promising to substitute traditional oil dampers because of adaptive properties of MR fluids. During vibration, significant energy is wasted due to the energy dissipation in the damper. Meanwhile, for conventional MR damping systems, extra power supply is needed. In this paper, a new energy harvester is designed in an MR damper that integrates controllable damping and energy harvesting functions into one device. The energy harvesting part of this MR damper has a unique mechanism converting linear motion to rotary motion that would be more stable and cost effective when compared to other mechanical transmissions. A Maxon motor is used as a power generator to convert the mechanical energy into electrical energy to supply power for the MR damping system. Compared to conventional approaches, there are several advantages in such an integrated device, including weight reduction, ease in installation with less maintenance. A mechanical energy harvested MR damper with linear-rotary motion converter and motion rectifier is designed, fabricated, and tested. Experimental studies on controllable damping force and harvested energy are performed with different transmissions. This energy harvesting MR damper would be suitable to vehicle suspensions, civil structures, and smart prostheses.

  17. Spring-fall asymmetry of substorm strength, geomagnetic activity and solar wind: Implications for semiannual variation and solar hemispheric asymmetry

    USGS Publications Warehouse

    Mursula, K.; Tanskanen, E.; Love, J.J.

    2011-01-01

    We study the seasonal variation of substorms, geomagnetic activity and their solar wind drivers in 1993-2008. The number of substorms and substorm mean duration depict an annual variation with maxima in Winter and Summer, respectively, reflecting the annual change of the local ionosphere. In contradiction, substorm mean amplitude, substorm total efficiency and global geomagnetic activity show a dominant annual variation, with equinoctial maxima alternating between Spring in solar cycle 22 and Fall in cycle 23. The largest annual variations were found in 1994 and 2003, in the declining phase of the two cycles when high-speed streams dominate the solar wind. A similar, large annual variation is found in the solar wind driver of substorms and geomagnetic activity, which implies that the annual variation of substorm strength, substorm efficiency and geomagnetic activity is not due to ionospheric conditions but to a hemispherically asymmetric distribution of solar wind which varies from one cycle to another. Our results imply that the overall semiannual variation in global geomagnetic activity has been seriously overestimated, and is largely an artifact of the dominant annual variation with maxima alternating between Spring and Fall. The results also suggest an intimate connection between the asymmetry of solar magnetic fields and some of the largest geomagnetic disturbances, offering interesting new pathways for forecasting disturbances with a longer lead time to the future. Copyright ?? 2011 by the American Geophysical Union.

  18. Spring-fall asymmetry of substorm strength, geomagnetic activity and solar wind: Implications for semiannual variation and solar hemispheric asymmetry

    USGS Publications Warehouse

    Marsula, K.; Tanskanen, E.; Love, J.J.

    2011-01-01

    We study the seasonal variation of substorms, geomagnetic activity and their solar wind drivers in 1993–2008. The number of substorms and substorm mean duration depict an annual variation with maxima in Winter and Summer, respectively, reflecting the annual change of the local ionosphere. In contradiction, substorm mean amplitude, substorm total efficiency and global geomagnetic activity show a dominant annual variation, with equinoctial maxima alternating between Spring in solar cycle 22 and Fall in cycle 23. The largest annual variations were found in 1994 and 2003, in the declining phase of the two cycles when high-speed streams dominate the solar wind. A similar, large annual variation is found in the solar wind driver of substorms and geomagnetic activity, which implies that the annual variation of substorm strength, substorm efficiency and geomagnetic activity is not due to ionospheric conditions but to a hemispherically asymmetric distribution of solar wind which varies from one cycle to another. Our results imply that the overall semiannual variation in global geomagnetic activity has been seriously overestimated, and is largely an artifact of the dominant annual variation with maxima alternating between Spring and Fall. The results also suggest an intimate connection between the asymmetry of solar magnetic fields and some of the largest geomagnetic disturbances, offering interesting new pathways for forecasting disturbances with a longer lead time to the future.

  19. Whirl Motion of a Seal Test Rig with Squeeze-Film Dampers

    NASA Technical Reports Server (NTRS)

    Proctor, Margaret P.; Gunter, Edgar J.

    2007-01-01

    This paper presents the experimental behavior and dynamic analysis of a high speed test rig with rolling element bearings mounted in squeeze film oil damper bearings. The test rotor is a double overhung configuration with rolling element ball bearings mounted in uncentered squeeze-film oil dampers. The damper design is similar to that employed with various high-speed aircraft HP gas turbines. The dynamic performance of the test rig with the originally installed dampers with an effective damper length of length 0.23-inch was unacceptable. The design speed of 40,000 RPM could not be safely achieved as nonsynchronous whirling at the overhung seal test disk and high amplitude critical speed response at the drive spline section occurred at 32,000 RPM. In addition to the self excited stability and critical speed problems, it was later seen from FFT data analysis, that a region of supersynchronous dead band whirling occurs between 10,000 to 15,000 RPM which can lead to bearing distress and wear. The system was analyzed using both linear and nonlinear techniques. The extended length damper design resulting from the analysis eliminated the rotor subsynchronous whirling, high amplitude critical speed, and the dead band whirling region allowing the system to achieve a speed of 45,000 RPM. However, nonlinear analysis shows that damper lockup could occur with high rotor unbalance at 33,000 RPM, even with the extended squeeze-film dampers. The control of damper lockup will be addressed in a future paper.

  20. A new design strategy for optimal distribution of dampers in smart building structures

    NASA Astrophysics Data System (ADS)

    Kazama, Hiroki; Mita, Akira

    2005-05-01

    A new strategy for structural control systems using viscous dampers is proposed. When we use some energy absorption devices, such as viscous dampers, in a building structure, the devices are uniformly distributed over the building so that the input energy should not concentrate in a specific story. However, this design strategy is not always the optimum one. A unique strategy that does not utilize the uniform distribution of dampers is presented here. Many advantages exist in the system that does not have uniformly distributed dampers. First, in the stories which do not require dampers, more freedom for using the floor space is possible. In addition, this fact results in lowering the cost as well by allocating the dampers to limited stories. By simplifying the flow of energy absorption, the structural reliability is significantly improved. The simplified energy flow in the structure will enhance the feasibility of the structural health monitoring system. In this paper, it is also shown that by softening appropriately the stiffness of the story to which dampers are installed, it is possible to raise the energy absorption efficiency without causing concentration of the drift. We define the modal concentration ratio using complex modal vectors to obtain optimal story stiffness and the capacity of viscous dampers for achieving the desired damping ratio. The performances of the systems were carefully evaluated by conducting nonlinear dynamic response analyses subject to several large earthquakes. The analysis models for the structures were the lumped mass models considering shear deformation. The dampers attached to the structure were modeled as Maxwell models to incorporate the stiffness of the supporting members.

  1. Active Galactic Nucleus Obscuration from Winds: From Dusty Infrared-Driven to Warm and X-Ray Photoionized

    NASA Technical Reports Server (NTRS)

    Dorodnitsyn, Anton V.; Kallman, Timothy R.

    2012-01-01

    We present calculations of active galactic nucleus winds at approx.parsec scales along with the associated obscuration. We take into account the pressure of infrared radiation on dust grains and the interaction of X-rays from a central black hole with hot and cold plasma. Infrared radiation (IR) is incorporated in radiation-hydrodynamic simulations adopting the flux-limited diffusion approximation. We find that in the range of X-ray luminosities L = 0.05-0.6 L(sub Edd), the Compton-thick part of the flow (aka torus) has an opening angle of approximately 72deg - 75deg regardless of the luminosity. At L > or approx. 0.1, the outflowing dusty wind provides the obscuration with IR pressure playing a major role. The global flow consists of two phases: the cold flow at inclinations (theta) > or approx.70deg and a hot, ionized wind of lower density at lower inclinations. The dynamical pressure of the hot wind is important in shaping the denser IR-supported flow. At luminosities < or = 0.1 L(sub Edd) episodes of outflow are followed by extended periods when the wind switches to slow accretion. Key words: acceleration of particles . galaxies: active . hydrodynamics . methods: numerical Online-only material: color figures

  2. Suspended chains damp wind-induced oscillations of tall flexible structures

    NASA Technical Reports Server (NTRS)

    Reed, W. H., III

    1968-01-01

    Hanging-chain system, which is a form of impact damper, suppresses wind-induced bending oscillations of tall cylindrical antenna masts. A cluster of chains enclosed in a neoprene shroud is suspended inside the tip of the antenna mast, forming a simple method of damping structural vibrations.

  3. Active Vertical Tail Buffeting Alleviation on an F/A-18 Model in a Wind Tunnel

    NASA Technical Reports Server (NTRS)

    Moses, Robert W.

    1999-01-01

    A 1/6-scale F-18 wind-tunnel model was tested in the Transonic Dynamics Tunnel at the NASA Langley Research Center as part of the Actively Controlled Response Of Buffet-Affected Tails (ACROBAT) program to assess the use of active controls in reducing vertical tail buffeting. The starboard vertical tail was equipped with an active rudder and other aerodynamic devices, and the port vertical tail was equipped with piezoelectric actuators. The tunnel conditions were atmospheric air at a dynamic pressure of 14 psf. By using single-input-single-output control laws at gains well below the physical limits of the control effectors, the power spectral density of the root strains at the frequency of the first bending mode of the vertical tail was reduced by as much as 60 percent up to angles of attack of 37 degrees. Root mean square (RMS) values of root strain were reduced by as much as 19 percent. Stability margins indicate that a constant gain setting in the control law may be used throughout the range of angle of attack tested.

  4. Active Vertical Tail Buffeting Alleviation on a Twin-Tail Fighter Configuration in a Wind Tunnel

    NASA Technical Reports Server (NTRS)

    Moses, Robert W.

    1997-01-01

    A 1/6-scale F-18 wind-tunnel model was tested in the Transonic Dynamics Tunnel at the NASA Langley Research Center as part of the Actively Controlled Response Of Buffet-Affected Tails (ACROBAT) program to assess the use of active controls in reducing vertical tail buffeting. The starboard vertical tail was equipped with an active rudder and other aerodynamic devices, and the port vertical tail was equipped with piezoelectric actuators. The tunnel conditions were atmospheric air at a dynamic pressure of 14 psf. By using single-input-single-output control laws at gains well below the physical limits of the control effectors, the power spectral density of the root strains at the frequency of the first bending mode of the vertical tail was reduced by as much as 60 percent up to angles of attack of 37 degrees. Root mean square (RMS) values of root strain were reduced by as much as 19 percent. Stability margins indicate that a constant gain setting in the control law may be used throughout the range of angle of attack tested.

  5. Some observed effects of part-span dampers on rotating blade row performance near design point

    NASA Technical Reports Server (NTRS)

    Esgar, G. M.; Sandercock, D. M.

    1973-01-01

    Detailed measured radial distributions of flow parameters for eight rotors with part-span dampers are used to study the effects of dampers on rotor performance and flow parameters at near design operation. All rotors had a blade tip diameter of about 20 in. and operated at a blade tip speed of about 1400 ft/sec. Several examples demonstrate that, when the local loss variations in the damper flow region are included in an aerodynamic design or analysis procedure, the computed spanwise distributions of flow parameters compare closely with measured distributions.

  6. Spin Testing for Durability Began on a Self-Tuning Impact Damper for Turbomachinery Blades

    NASA Technical Reports Server (NTRS)

    Duffy, Kirsten; Mehmed, Oral

    2003-01-01

    NASA and Pratt & Whitney will collaborate under a Space Act Agreement to perform spin testing of the impact damper to verify damping effectiveness and durability. Pratt & Whitney will provide the turbine blade and damper hardware for the tests. NASA will provide the facility and perform the tests. Effectiveness and durability will be investigated during and after sustained sweeps of rotor speed through resonance. Tests of a platform wedge damper are also planned to compare its effectiveness with that of the impact damper. Results from baseline tests without dampers will be used to measure damping effectiveness. The self-tuning impact damper combines two damping methods-the tuned mass damper and the impact damper. It consists of a ball located within a cavity in the blade. This ball rolls back and forth on a spherical trough under centrifugal load (tuned mass damper) and can strike the walls of the cavity (impact damper). The ball s rolling natural frequency is proportional to the rotor speed and can be designed to follow an engine-order line (integer multiple of rotor speed). Aerodynamic forcing frequencies typically follow these engineorder lines, and a damper tuned to the engine order will most effectively reduce blade vibrations when the resonant frequency equals the engine-order forcing frequency. This damper has been tested in flat plates and turbine blades in the Dynamic Spin Facility. During testing, a pair of plates or blades rotates in vacuum. Excitation is provided by one of three methods--eddy-current engine-order excitation (ECE), electromechanical shakers, and magnetic bearing excitation. The eddy-current system consists of magnets located circumferentially around the rotor. As a blade passes a magnet, a force is imparted on the blade. The number of magnets used can be varied to change the desired engine order of the excitation. The magnets are remotely raised or lowered to change the magnitude of the force on the blades. The other two methods apply

  7. Off-design correlation for losses due to part-span dampers on transonic rotors

    NASA Technical Reports Server (NTRS)

    Roberts, W. B.; Crouse, J. E.; Sandercock, D. M.

    1980-01-01

    Experimental data from 10 transonic fan rotors were used to correlate losses created by part-span dampers located near the midchord position on the rotor blades. The design tip speed of these rotors varied from 419 to 425 m/sec, and the design pressure ratio varied from 1.6 to 2.0. Additional loss caused by the dampers for operating conditions between 50 and 100 percent of design speed were correlated with relevant aerodynamic and geometric parameters. The resulting correlation predicts the variation of total-pressure-loss coefficient in the damper region to a good approximation.

  8. Correlation of part-span damper losses through transonic rotors operating near design point

    NASA Technical Reports Server (NTRS)

    Roberts, W. B.

    1977-01-01

    The design-point losses caused by part-span dampers (PSD) were correlated for 21 transonic axial flow fan rotors that had tip speeds varying from 350 to 488 meters per second and design pressure ratios of 1.5 to 2.0. For these rotors a correlation using mean inlet Mach number at the damper location, along with relevant geometric and aerodynamic loading parameters, predicts the variation of total pressure loss coefficient in the region of the damper to a good approximation.

  9. Optimization of a nutation damper attached to a spin-stabilized satellite

    NASA Astrophysics Data System (ADS)

    Hauboldt, Brady P.

    1994-12-01

    This study uses linearized equations of motion for a rigid body with an attached spring-mass-damper to maximize the decay rate of a satellite's coning motion. An analysis of the numerical eigenvalues is presented which leads to an optimal relationship between relevant parameters: damper placement, spring constant, damping coefficient, system moments of inertia, and damper mass fraction. The coupled system's eigenvalues do not provide true critical damping, thus the real eigenvalue parts are minimized in order to achieve damping which requires the minimum amount of time. A comparison between this optimal design method and a classical method concludes with a noticeable improvement in damping performance for the optimized systems.

  10. Elasticity effects on cavitation in a squeeze film damper undergoing noncentered circular whirl

    NASA Technical Reports Server (NTRS)

    Brewe, David E.

    1988-01-01

    Elasticity of the liner and its effects on cavitation were numerically determined for a squeeze film damper subjected to dynamic loading. The loading was manifested as a prescribed motion of the rotor undergoing noncentered circular whirl. The boundary conditions were implemented using Elrod's algorithm which conserves lineal mass flux through the moving cavitation bubble as well as the oil film region of the damper. Computational movies were used to analyze the rapidly changing pressures and vapor bubble dynamics throughout the dynamic cycle for various flexibilities in the damper liner. The effects of liner elasticity on cavitation were only noticeable for the intermediate and high values of viscosity used in this study.

  11. Damping of rotating beams with particle dampers: Discrete element method analysis

    NASA Astrophysics Data System (ADS)

    Els, D. N. J.

    2013-06-01

    The performance of particle dampers (PDs) under centrifugal loads was investigated. A test bench consisting of a rotating cantilever beam with a particle damper at the tip was developed (D. N. J. Els, AIAA Journal 49, 2228-2238 (2011)). Equal mass containers with different depths, filled with a range of uniform-sized steel ball bearings, were used as particle dampers. The experiments were duplicated numerically with a discrete element method (DEM) model, calibrated against the experimental data. The DEM model of the rotating beam with a PD at the tip captured the performance of the PD very well over a wide range of tests with different configurations and rotation velocities.

  12. Experimental evidence for the effect of small wind turbine proximity and operation on bird and bat activity.

    PubMed

    Minderman, Jeroen; Pendlebury, Chris J; Pearce-Higgins, James W; Park, Kirsty J

    2012-01-01

    The development of renewable energy technologies such as wind turbines forms a vital part of strategies to reduce greenhouse gas emissions worldwide. Although large wind farms generate the majority of wind energy, the small wind turbine (SWT, units generating <50 kW) sector is growing rapidly. In spite of evidence of effects of large wind farms on birds and bats, effects of SWTs on wildlife have not been studied and are likely to be different due to their potential siting in a wider range of habitats. We present the first study to quantify the effects of SWTs on birds and bats. Using a field experiment, we show that bird activity is similar in two distance bands surrounding a sample of SWTs (between 6-18 m hub height) and is not affected by SWT operation at the fine scale studied. At shorter distances from operating turbines (0-5 m), bat activity (measured as the probability of a bat "pass" per hour) decreases from 84% (71-91%) to 28% (11-54%) as wind speed increases from 0 to 14 m/s. This effect is weaker at greater distances (20-25 m) from operating turbines (activity decreases from 80% (65-89%) to 59% (32-81%)), and absent when they are braked. We conclude that bats avoid operating SWTs but that this effect diminishes within 20 m. Such displacement effects may have important consequences especially in landscapes where suitable habitat is limiting. Planning guidance for SWTs is currently lacking. Based on our results we recommend that they are sited at least 20 m away from potentially valuable bat habitat.

  13. Experimental Evidence for the Effect of Small Wind Turbine Proximity and Operation on Bird and Bat Activity

    PubMed Central

    Minderman, Jeroen; Pendlebury, Chris J.; Pearce-Higgins, James W.; Park, Kirsty J.

    2012-01-01

    The development of renewable energy technologies such as wind turbines forms a vital part of strategies to reduce greenhouse gas emissions worldwide. Although large wind farms generate the majority of wind energy, the small wind turbine (SWT, units generating <50 kW) sector is growing rapidly. In spite of evidence of effects of large wind farms on birds and bats, effects of SWTs on wildlife have not been studied and are likely to be different due to their potential siting in a wider range of habitats. We present the first study to quantify the effects of SWTs on birds and bats. Using a field experiment, we show that bird activity is similar in two distance bands surrounding a sample of SWTs (between 6–18 m hub height) and is not affected by SWT operation at the fine scale studied. At shorter distances from operating turbines (0–5 m), bat activity (measured as the probability of a bat “pass” per hour) decreases from 84% (71–91%) to 28% (11–54%) as wind speed increases from 0 to 14 m/s. This effect is weaker at greater distances (20–25 m) from operating turbines (activity decreases from 80% (65–89%) to 59% (32–81%)), and absent when they are braked. We conclude that bats avoid operating SWTs but that this effect diminishes within 20 m. Such displacement effects may have important consequences especially in landscapes where suitable habitat is limiting. Planning guidance for SWTs is currently lacking. Based on our results we recommend that they are sited at least 20 m away from potentially valuable bat habitat. PMID:22859969

  14. Line-driven disk winds in active galactic nuclei: The critical importance of ionization and radiative transfer

    SciTech Connect

    Higginbottom, Nick; Knigge, Christian; Matthews, James H.; Proga, Daniel; Long, Knox S.; Sim, Stuart A.

    2014-07-01

    Accretion disk winds are thought to produce many of the characteristic features seen in the spectra of active galactic nuclei (AGNs) and quasi-stellar objects (QSOs). These outflows also represent a natural form of feedback between the central supermassive black hole and its host galaxy. The mechanism for driving this mass loss remains unknown, although radiation pressure mediated by spectral lines is a leading candidate. Here, we calculate the ionization state of, and emergent spectra for, the hydrodynamic simulation of a line-driven disk wind previously presented by Proga and Kallman. To achieve this, we carry out a comprehensive Monte Carlo simulation of the radiative transfer through, and energy exchange within, the predicted outflow. We find that the wind is much more ionized than originally estimated. This is in part because it is much more difficult to shield any wind regions effectively when the outflow itself is allowed to reprocess and redirect ionizing photons. As a result, the calculated spectrum that would be observed from this particular outflow solution would not contain the ultraviolet spectral lines that are observed in many AGN/QSOs. Furthermore, the wind is so highly ionized that line driving would not actually be efficient. This does not necessarily mean that line-driven winds are not viable. However, our work does illustrate that in order to arrive at a self-consistent model of line-driven disk winds in AGN/QSO, it will be critical to include a more detailed treatment of radiative transfer and ionization in the next generation of hydrodynamic simulations.

  15. A parametric sensitivity and optimization study for the active flexible wing wind-tunnel model flutter characteristics

    NASA Technical Reports Server (NTRS)

    Rais-Rohani, Masoud

    1991-01-01

    In this paper an effort is made to improve the analytical open-loop flutter predictions for the Active Flexible Wing wind-tunnel model using a sensitivity based optimization approach. The sensitivity derivatives of the flutter frequency and dynamic pressure of the model with respect to the lag terms appearing in the Roger's unsteady aerodynamics approximations are evaluated both analytical and by finite differences. Then, the Levenberg-Marquardt method is used to find the optimum values for these lag-terms. The results obtained here agree much better with the experimental (wind tunnel) results than those found in the previous studies.

  16. Radar observations of high-latitude lower-thermospheric and upper-mesospheric winds and their response to geomagnetic activity

    SciTech Connect

    Johnson, R.M.

    1987-01-01

    Observations made by the Chatanika, Alaska, incoherent scatter radar during the summer months of 1976 to 1081 are analyzed to obtain high resolution lower-thermospheric neutral winds. Average winds and their tidal components are presented and compared to previous observational and model results. Upper-mesospheric neutral-wind observations obtained by the Poke Flat, Alaska Mesosphere-Stratosphere-Troposphere (MST) radar during the summer months of 1980 to 1982 are investigated statistically for evidence of variations due to geomagnetic activity. Observation of upper-mesospheric neutral winds made during two energetic Solar Proton Events (SPEs) by the Poker Flat, MST radar are presented. These results allow the low-altitude limits of magnetospheric coupling to the neutral atmosphere to be determined. Lower-thermospheric neutral winds are coupled to the ion convection driven by typical magnetospheric forcing above about 100 km. Coupling to lower atmospheric levels does not occur except during intervals of extreme disturbance of the magnetosphere-ionosphere-thermosphere system which are also accompanied by dramatically increased ionization in the high-latitude mesosphere, such as SPEs.

  17. ACTIVE GALACTIC NUCLEUS OBSCURATION FROM WINDS: FROM DUSTY INFRARED-DRIVEN TO WARM AND X-RAY PHOTOIONIZED

    SciTech Connect

    Dorodnitsyn, A.; Kallman, T.

    2012-12-10

    We present calculations of active galactic nucleus winds at {approx}parsec scales along with the associated obscuration. We take into account the pressure of infrared radiation on dust grains and the interaction of X-rays from a central black hole with hot and cold plasma. Infrared radiation (IR) is incorporated in radiation-hydrodynamic simulations adopting the flux-limited diffusion approximation. We find that in the range of X-ray luminosities L = 0.05-0.6 L{sub Edd}, the Compton-thick part of the flow (aka torus) has an opening angle of approximately 72 Degree-Sign -75 Degree-Sign regardless of the luminosity. At L {approx}> 0.1, the outflowing dusty wind provides the obscuration with IR pressure playing a major role. The global flow consists of two phases: the cold flow at inclinations {theta} {approx}> 70 Degree-Sign and a hot, ionized wind of lower density at lower inclinations. The dynamical pressure of the hot wind is important in shaping the denser IR-supported flow. At luminosities {<=}0.1 L{sub Edd} episodes of outflow are followed by extended periods when the wind switches to slow accretion.

  18. The vertical propagation and extent of stratospheric temperature and wind anomalies related to enhanced geomagnetic activity

    NASA Astrophysics Data System (ADS)

    Seppälä, A. M.; Baumgaertner, A. J.; Jöckel, P.; Clilverd, M.

    2010-12-01

    Model studies have suggested that Odd Nitrogen, NOx, created by Energetic Particle Precipitation (EPP) and the consequent ozone loss through catalytic loss cycles could have an effect on stratospheric and tropospheric (e.g. surface level) temperatures. These effects can potentially be comparable to the effects induced by the solar cycle at high latitudes. Significant mesospheric and stratospheric NOx enhancements have been observed during times of high solar activity (e.g. during Solar Proton Events). NOx can also be, through dynamics, transported from high altitudes (mesosphere-lower thermosphere), where it's created by EPP, down to the stratosphere. Once the NOx reaches the the stratosphere, ozone loss reactions involving NOx provide a link to the general stratospheric ozone balance. Surface temperature effects similar to those reported in the model studies were recently found in re-analysis meteorological data sets, but the mechanism connecting the high altitude NOx production to the surface level remained unclear. In this work, using meteorological re-analysis and operational data sets from the European Centre for Medium Range Weather Forecast and the UK Met Office from 1957 to 2009, we examine the vertical propagation and extent, particularly in the stratosphere, of temperature and wind anomalies related to enhanced geomagnetic activity (i.e. enhanced EPP into the atmosphere), to provide better understanding of the linking mechanism. Furthermore we discuss results from the atmospheric chemistry general circulation model ECHAM5/MESSy, which provides a more comprehensive view of the variation in atmospheric parameters as a result of varying EPP input.

  19. High spatial resolution monitoring of the activity of BA supergiant winds

    NASA Astrophysics Data System (ADS)

    Chesneau, Olivier; Dessart, Luc; Kaufer, Andreas; Mourard, Denis; Stahl, Otmar; Prinja, Raman K.; Owocki, Stan P.

    2011-07-01

    There are currently two optical interferometry recombiners that can provide spectral resolutions better than 10000, AMBER/VLTI operating in the H-K bands, and VEGA/CHARA, recently commissioned, operating in the visible. These instruments are well suited to study the wind activity of the brightest AB supergiants in our vicinity, in lines such as Hα or Brγ. We present here the first observations of this kind, performed on Rigel (B8Ia) and Deneb (A2Ia). Rigel was monitored by AMBER in two campaigns, in 2006-2007 and 2009-2010, and observed in 2009 by VEGA; whereas Deneb was monitored in 2008-2009 by VEGA. The extension of the Hα and Brγ line forming regions were accurately measured and compared with CMFGEN models of both stars. Moreover, clear signs of activity were observed in the differential visibility and phases. These pioneer observations are still limited, but show the path for a better understanding of the spatial structure and temporal evolution of localized ejections using optical interferometry.

  20. The stellar wind as a key to the understanding of the spectral activity of IN Com

    NASA Astrophysics Data System (ADS)

    Kozlova, O. V.; Alekseev, I. Yu.

    2014-06-01

    We present long-term spectral observations ( R = 20000) of IN Com in the region of the Hα, Hβ, and He I 5876 lines. One distinguishing characteristic of the stellar spectrum is the presence in the Hα line of an extended two-component emission with limits up to ±400 km/s. Emission parameters show the rotation modulation with the stellar rotation period and a significant variability on the long-term scale. Similar emissions are also observed in the Hβ and He I 5876 lines. Our results allow us to conclude that observational emission profiles are formed in an optically thin hot gas. This is a result of the presence of a circumstellar gas disk around IN Com. Its size does not exceed several stellar radii. The material for the disk is supported by the stellar wind from IN Com. The detected variability of Hα-emission parameters shows a clear connection with the photopolarimetric activity of the star. This fact allows us to associate the long-term spectral variability with cycles of stellar activity of IN Com.

  1. Active stall control for large offshore horizontal axis wind turbines; a conceptual study considering different actuation methods

    NASA Astrophysics Data System (ADS)

    Pereira, R.; van Bussel, G. J. W.; Timmer, W. A.

    2014-12-01

    The increasing size of Horizontal Axis Wind Turbines and the trend to install wind farms further offshore demand more robust design options. If the pitch system could be eliminated, the availability of Horizontal Axis Wind Turbines should increase. This research investigates the use of active stall control to regulate power production in replacement of the pitch system. A feasibility study is conducted using a blade element momentum code and taking the National Renewable Energy Laboratory 5 MW turbine as baseline case. Considering half of the blade span is equipped with actuators, the required change in the lift coefficient to regulate power was estimated in ΔCl = 0.7. Three actuation technologies are investigated, namely Boundary Layer Transpiration, Trailing Edge Jets and Dielectric Barrier Discharge actuators. Results indicate the authority of the actuators considered is not sufficient to regulate power, since the change in the lift coefficient is not large enough. Active stall control of Horizontal Axis Wind Turbines appears feasible only if the rotor is re-designed from the start to incorporate active-stall devices.

  2. Active Power Control Testing at the U.S. National Wind Technology Center (NWTC) (Presentation)

    SciTech Connect

    Ela, E.

    2011-01-01

    In order to keep the electricity grid stable and the lights on, the power system relies on certain responses from its generating fleet. This presentation evaluates the potential for wind turbines and wind power plants to provide these services and assist the grid during critical times.

  3. Variable force, eddy-current or magnetic damper

    NASA Technical Reports Server (NTRS)

    Cunningham, R. E. (Inventor)

    1985-01-01

    An object of the invention is to provide variable damping for resonant vibrations which may occur at different rotational speeds in the range of rpms in which a rotating machine is operated. A variable force damper in accordance with the invention includes a rotating mass carried on a shaft which is supported by a bearing in a resilient cage. The cage is attached to a support plate whose rim extends into an annular groove in a housing. Variable damping is effected by tabs of electrically conducting nonmagnetic material which extend radially from the cage. The tabs at an index position lie between the pole face of respective C shaped magnets. The magnets are attached by cantilever spring members to the housing.

  4. Timoshenko beam with tuned mass dampers and its design curves

    NASA Astrophysics Data System (ADS)

    Chen, Yung-Hsiang; Huang, Yen-Hui

    2004-12-01

    The structural analysis and design of a Timoshenko beam with tuned mass dampers (or TMDs) under a harmonic excitation are presented. The dynamic-stiffness matrix of a Timoshenko-beam element is employed to study the dynamic responses for the whole frequency range. A proposed simplified two-degree-of-freedom system and Hartog's method are employed to study the dynamic characteristics of TMDs. Some important formulas for the design parameters (such as the mass ratio and stiffness ratio at the tuned frequency, the optimal damping ratio of TMDs, and their upper limits) and a series of the design charts are presented for practical applications, if the beam-own damping is absent and all TMDs are identical.

  5. Interhourly Variability Index of Geomagnetic Activity and Its Use in Deriving the Long-Term Variation of Solar Wind Speed

    DTIC Science & Technology

    2007-10-31

    CONTRACT NUMBER Interhourly variability index of geomagnetic activity and its use in deriving the long-term variation of solar wind speed 5b...detailed derivation of the interhourly variability (IHP) index of geomagnetic activity. The LHV index for a given geomagnetic element is mechanically... index is derived separately for stations in both hemispheres within six longitude sectors spanning the Earth using only local night hours. It is

  6. A new placement optimization method for viscoelastic dampers: Energy dissipation method

    NASA Astrophysics Data System (ADS)

    Qu, Ji-Ting

    2012-09-01

    A new mathematic model of location optimization for viscoelastic dampers is established through energy analysis based on force analogy method. Three working conditions (three lower limits of the new location index) as well as four ground motions are considered in this study, using MATLAB and SAP2000 in programming and verifying. This paper deals with the optimal placement of viscoelastic dampers and step-by-step time history analyses are carried out. Numerical analysis is illustrated to verify the effectiveness and feasibility of the new mathematic model for structural control. In addition, not only the optimal placement method using force analogy method can confirm dampers' locations all at once and be accurate to each span, but also it is without circular calculating. At last, a few helpful conclusions on viscoelastic dampers' optimal placement are made.

  7. Experimental evaluation of a tuned electromagnetic damper for vibration control of cryogenic turbopump rotors

    NASA Technical Reports Server (NTRS)

    Dirusso, Eliseo; Brown, Gerald V.

    1990-01-01

    Experiments were performed on a passive tuned electromagnetic damper that could be used for damping rotor vibrations in cryogenic turbopumps for rocket engines. The tests were performed in a rig that used liquid nitrogen to produce cryogenic turbopump temperatures. This damper is most effective at cryogenic temperatures and is not a viable damper at room temperature. The unbalanced amplitude response of the rotor shaft was measured for undamped (baseline) and damped conditions at the critical speeds of the rotor (approx. 5900 to 6400 rpm) and the data were compared. The tests were performed for a speed range between 900 and 10 000 rpm. The tests revealed that the damper is very effective for damping single-mode narrow bandwidth amplitude response but is less effective in damping broadband response or multimode amplitude response.

  8. Modeling and control of an ER long-stroke vibration damper

    NASA Astrophysics Data System (ADS)

    Peel, David J.; Stanway, Roger; Bullough, William A.

    1998-07-01

    Electrically-structured (ES) fluids offer a potentially elegant means of introducing greater flexibility into a range of industrial machines and structures, and are especially suited to controllable vibration damping. The authors have developed a technique for characterizing ES fluids, leading to a mathematical model and practical device design procedure, the principles of which are verified by testing with an industrial scale, long-stroke electro- rheological damper, suited to the needs of a rail vehicle lateral suspension. In this paper, the model is applied to predict the effect on the test damper steady state performance, and performance envelope, of the principle variables of operating temperature, mechanical displacement amplitude and frequency, and control field excitation, which influence the controllability and control requirements of the damper, and to show that the test damper should achieve the desired range of control.

  9. Membrane-type resonator as an effective miniaturized tuned vibration mass damper

    NASA Astrophysics Data System (ADS)

    Sun, Liang; Au-Yeung, Ka Yan; Yang, Min; Tang, Suet To; Yang, Zhiyu; Sheng, Ping

    2016-08-01

    Damping of low frequency vibration by lightweight and compact devices has been a serious challenge in various areas of engineering science. Here we report the experimental realization of a type of miniature low frequency vibration dampers based on decorated membrane resonators. At frequency around 150 Hz, two dampers, each with outer dimensions of 28 mm in diameter and 5 mm in height, and a total mass of 1.78 g which is less than 0.6% of the host structure (a nearly free-standing aluminum beam), can reduce its vibrational amplitude by a factor of 1400, or limit its maximum resonance quality factor to 18. Furthermore, the conceptual design of the dampers lays the foundation and demonstrates the potential of further miniaturization of low frequency dampers.

  10. Damping performance of bean bag dampers in zero gravity environments

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Chen, Tianning; Wang, Xiaopeng

    2016-06-01

    Bean bag dampers (BBDs), developed from impact damping technology, have been widely applied in engineering field to attenuate the vibration of a structural system. The damping effect of a BBD on vibration control in ground gravity environments is good, but its performance in zero gravity environments is not clear, and there are few studies on it. Therefore, the damping effect of BBDs in zero gravity environments was investigated based on the discrete element method (DEM) in this paper. Firstly, a three-dimensional DEM model of a BBD was established, and the damping effects of the single degree of freedom (SDOF) systems with BBDs and non-obstructive particle dampers (NOPDs) in zero gravity environments were compared. Moreover, the influences of the diameter of the inner ball, the tightness of BBD, the vibration frequency of SDOF system and the gap between BBD and cavity on the vibration reduction effect of BBD in zero gravity environments were also studied, and the results were compared with the system with BBD in ground gravity environments. There are optimum ranges of the diameter of the inner ball, tightness and gap for BBD, and the effects of these parameters on the damping performances of BBD in gravity and zero gravity environments are similar in evolving trends, and the values are without big differences in the optimum ranges. Thereby the parameter selection in BBD design in zero gravity environments is similar to that in gravity environments. However, the diameter of BBD should be a slightly larger than the size of the cavity when the structures with BBD work in zero gravity environments. The BBD is supposed to be picked tightly when the vibration frequency is high, and the BBD has better to be picked more tightly in zero gravity environments. These results can be used as a guide in the design of BBDs in zero gravity environments.

  11. Damper-controlled switch for SMA motion smoothing

    NASA Astrophysics Data System (ADS)

    Aguayo, Clover; Utter, Brent; Luntz, Jonathan; Gonzalez, Richard; Brei, Diann; Johnson, Nancy L.; Alexander, Paul W.

    2014-04-01

    While the use of SMA-actuated devices continues to grow in many industries, current device limitations pose a challenge to successful adoption for certain classes of applications. SMA-actuated devices typically demonstrate motion with non-constant velocity due to the non-linear thermo-mechanically coupled behavior of SMA material transformation, and motion sensitivity to external factors such as voltage and load. This variation in motion can lead to the perception of poor device quality, limiting SMA-actuated devices to applications hidden from the sight of the product user, or requiring them to be augmented with higher cost controls to improve the motion quality. Therefore, a need exists for simple, passive, low-cost device technologies that enable the designer to prescribe desired motion characteristics with relative insensitivity to fluctuation in operating conditions. This paper presents a Damper Controlled Switch (DCS) mechanism that delivers constant velocity and relative insensitivity to operating conditions when combined with a standard SMA wire actuator. The DCS includes a damper that acts against a spring to open a switch when the velocity exceeds a tunable threshold. To validate the ability of the DCS to provide the desired motion quality, experiments were conducted comparing the normal motion of the SMA actuator to the motion produced when the same actuator was fitted with a DCS prototype. The addition of the DCS produced nearly constant actuator velocity, performing significantly better than the SMA actuator alone. The tunability of the DCS was demonstrated producing a wide range of attainable constant velocities. Finally, a set of experiments explored the DCS's sensitivity to voltage and load, indicating a low sensitivity to a wide range of operating parameters for which the operating limits were identified. The DCS represents a simple, compact technology based on passive, low-cost components, providing a very practical solution that will enable

  12. Failure Criticality Analysis for Type B and Type F Wind Measuring and Indicating Equipment,

    DTIC Science & Technology

    1980-10-01

    is used in the servo system of thu Type F wind dire it ionaWr, irI wiig sped tssemhlios( in) I i o of the so] d-stat t servo amp 1 aae r u!;w3 it: ’ ht...and indicating equipment include the following: defective bearings that are either seized or exhibit high friction, a binding or seized inertia damper ...to defective bearings or a binding inertia damper involve seizure or sluggishness of response by the synchro. Symptoms resulting from an open or

  13. MR damper-based semiactive control system using electromagnetic induction device

    NASA Astrophysics Data System (ADS)

    Jung, Hyung-Jo; Jang, Dong-Doo; Koo, Jeong-Hoi

    2009-03-01

    Magnetorheological (MR) damper-based semiactive control systems can be considered as one of the most advantageous control systems for natural hazard mitigation in the field of civil engineering because MR dampers have many good features such as small power requirement, reliability, and low price to manufacture. Those systems require feedback control and power supply parts to efficiently reduce the structural responses. The control system becomes complex when a lot of MR dampers are applied to large-scale civil structures, such as cable-stayed bridges and high-rise buildings, resulting in difficulties in its implementation and maintenance. To overcome the above difficulties, a new-class MR damper-based control system was recently proposed by replacing feedback control and power supply parts with an electromagnetic induction (EMI) part consisting of permanent magnets and a coil. According to the Faraday's law of electromagnetic induction, an EMI part produces electrical energy (i.e., electromotive force or induced voltage) from mechanical energy (i.e., reciprocal motions of an MR damper), which is proportional to the rate of the change of the movement of a damper. From this characteristic of an EMI part, it might be used as a response sensing device as well as an alternative power supply. In addition, some control algorithms used in the MR damper-based semiactive control systems require the measurement information on the response related to the relative velocity of the damper. In this study, the sensing capability of an EMI part is preliminarily examined for an application to the MR damper-based semiactive control system. To this end, experimental tests are carried out using the real-scale stay cable employing an MR damper with an EMI part. It is demonstrated from the tests that an EMI part could exactly extract the dynamic characteristics of the stay cable so that it might be used as a sensing device for estimating the tension force of the stay cable. In addition

  14. Elasticity Effects on Cavitation in a Squeeze Film Damper Undergoing Noncentered Circular Whirl

    DTIC Science & Technology

    1989-06-01

    numerically determined for a squeeze film damper subjected to dynamic loading. The loading was manifested as a prescribed motion of the rotot undergoing...cavitation bubble as well as the oil film region of the damper. Computational L movies were used to analyze the rapidly changing pressures and vapor bubble...and B.J. Hamrock, "High-Speed Motion Picture Camera Experiments of Cavitation in Dynamically Loaded Journal Bearings," J. Lubr. Technol., 105 (1983

  15. The Effects of Manufacturing Tolerances on the Vibration of Aero-engine Rotor-damper Assemblies

    NASA Technical Reports Server (NTRS)

    Sykes, J. E. H.; Holmes, R.

    1991-01-01

    A range of rotor assemblies incorporating one and two squeeze film dampers with various static misalignments is investigated. Waterfall diagrams are constructed which demonstrate the effects of such misalignment and damper support flexibility on the nature and severity of subsynchronous resonance and jump phenomena. Vibration signatures of similar rotor-bearing assemblies are shown to contrast strongly due to different accumulations of tolerances during manufacture, fitting, and operation.

  16. Cavitation effects on the pressure distribution of a squeeze film damper bearing

    NASA Technical Reports Server (NTRS)

    Zeidan, Fouad Y.; Vance, John M.

    1989-01-01

    High speed motion pictures have revealed several operating regimes in a squeeze film damper. Pressure measurements corresponding to these distinct regimes were made to examine their effect on the performance of such dampers. Visual observation also revealed the means by which the pressure in the feed groove showed higher amplitudes than the theory predicts. Comparison between vapor and gaseous cavitation are made based on their characteristic pressure wave, and the effect this has on the total force and its phase.

  17. Study, Development, and Design of Replaceable Shear Yielding Steel Panel Damper

    SciTech Connect

    Murakami, Katsuhide; Keii, Michio

    2008-07-08

    For middle-high rise buildings, vibration controlled structures to reduce the damage of main frames are recently becoming general in Japan. A steel material damper is low price and excellent in the energy absorption efficiency at a large earthquake. Though the exchange of the dampers are necessary when an excessive accumulation of plasticity deformation occurs, a steel material damping system, which received an excessive accumulation of plasticity deformation after a large earthquake, can recover a seismic-proof performance and property value of the building after the replacement. In the paper, shear yielding steel panel dampers installed in the web of a beam connected with high tension bolt joint is introduced. This damper is made of low-yield point steel, and the advantages of this system are low cost, easy-production and easy-replacement. For this steel panel damper, the finite element method (FEM) analysis using the shell element model adjusted to 1/2 of 6.4 m beam span is executed to make the design most effective. Yielding property of the beam installing this damper, shape of the splice plate and the bolt orientation for the connecting are examined in this analysis. As a result, we found that the plastic strain extends uniformly to the entire damping panel when making the splice plate a trapezoidal shape. The basic performance confirmation examination was also done using the real scale examination model besides the FEM analysis, and the performance of the system was confirmed. In addition, design of a high rise building in which the steel shear-yielding panel dampers and oil dampers were adopted without disturbing an architectural plan is also introduced.

  18. Recent US Activities Toward Development of a Global Tropospheric 3D Wind Profiling System

    NASA Astrophysics Data System (ADS)

    Gentry, B. M.; Atlas, R.; Baker, W.; Emmitt, G. D.; Hardesty, R. M.; Kakar, R. K.; Kavaya, M. J.; Mango, S.; Miller, K.; Riishojgaard, L. P.

    2008-12-01

    The wind field plays a unique dynamical role in forcing the mass field to adjust to it at all scales in the tropics, and at small scales in the extra-tropics. Because of this unique role, knowledge of the wind field is required to accurately specify the global initial conditions for numerical weather forecasting. In addition to improving numerical weather prediction, there is also a need for improved accuracy of wind fields to assess long term sensitivity of the general circulation to climate change and to improve horizontal and vertical transport estimates of important atmospheric constituents. In spite of the significance, the 3-D structure of the wind field remains largely unobserved on a global scale. A new satellite mission to accurately measure the global wind field would fill this important gap in the Global Observing System. Space-based Doppler wind lidar has been identified as the key technology necessary to meet the global wind profiling requirement. The 2007 NRC Decadal Survey for Earth Science lists a Global Tropospheric 3-D Wind mission as one of the 15 priority missions recommended for NASA in the next decade. The NRC survey recommended a two phase approach to achieving an operational global wind measurement capability. The first recommended step is for NASA to develop the technology and fly a pre-operational mission to demonstrate the technology and measurement concept and establish the performance standards for an operational wind mission. Phase two would be to develop and fly an operational wind system in the 2025 timeframe. The technology approach recommended is a hybrid Doppler wind lidar (HDWL). The HDWL takes advantage of the complementary capabilities of two Doppler lidar technologies, a coherent Doppler lidar sensing winds from the aerosol backscattered laser signal at a wavelength of 2 microns and a direct detection Doppler lidar sensing winds from the molecular backscattered laser signal at 355 nm. The direct detection Doppler system

  19. Development of a long-stroke MR damper for a building with tuned masses

    NASA Astrophysics Data System (ADS)

    Zemp, René; de la Llera, Juan Carlos; Saldias, Hernaldo; Weber, Felix

    2016-10-01

    This article deals with the development of a long-stroke MR-damper aimed to control, by reacting on a tuned mass (TM), the earthquake performance of an existing 21-story office building located in Santiago, Chile. The ±1 m stroke MR-damper was designed using the nominal response of the building equipped with two 160 ton pendular masses tuned to the fundamental lateral vibration mode of the structure. An extended physical on-off controller, a special current driver, a new real-time structural displacement sensor, and an MR-damper force sensor were all developed for this application. The physical damper and control were experimentally validated using a suite of cyclic and seismic signals. The real-time displacement sensor developed was validated by first using a scaled down building prototype subjected to shaking table tests, and then a real-scale free vibration test on the sensor installed horizontally at the foundation level of a building. It is concluded that the proposed TM and MR-damper solution is technically feasible, and for an equivalent key performance index also defined herein, more economical than a solution based on passive viscous dampers.

  20. Performance-based Design of RC Frame Buildings with Metallic and Friction Dampers

    NASA Astrophysics Data System (ADS)

    Chaudhury, Deepsikha; Singh, Yogendra

    2014-12-01

    Supplemental energy dissipation is a technique of earthquake resistant design and for improving the seismic performance of existing buildings. In the present study, a comprehensive design methodology for performance based design of frame buildings with metallic and friction dampers has been proposed. In this study, the target performance level is aimed to achieve both in terms of inter-storey drift and plastic hinge rotation. A non-iterative step-by-step design procedure is proposed to achieve the target performance level. The methodology provides the design yield forces in case of metallic dampers, and slip forces in case of friction dampers. A satisfactory distribution of both types of dampers along the height of the building is also provided in the methodology. The efficiency of the proposed design methodology is validated by applying to a ten storey building and performing nonlinear time history analysis. The building, with and without dampers, is subjected to five spectrum compatible time histories with peak ground acceleration of 0.24 g and the relative performance of the building with the two types of dampers is studied.

  1. Research on seismic performance of slotted RC walls with replaceable damper

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Ou, Jinping; Huo, Lianfeng

    2015-04-01

    Structural walls are important components of resisting the lateral loads for high-rise structures. However, the traditional walls are difficult to repair or replace in post-earthquake events. Hence, over the past few years, a research was made of several kinds of replaceable structures such as replaceable coupling beam and replaceable wall toe. In this paper, a new seismic energy dissipation wall structure is proposed. The new wall is one with purposely build-in vertical slits within the wall panel, and metallic dampers are installed on the vertical slits so that the seismic performance of the structure can be controlled. Moreover, the metallic damper is easy to be replaced in post-earthquake events. The proposed metallic damper is with a serial of diamond-shaped holes and designed based on the lateral deformation of the wall. The yielding scheme of the metallic damper is proposed in order to achieve the ductility and energy dissipation demand of the walls. The mechanical model of the metallic damper is established. Finally, the numerical simulations of the metallic damper based on the finite element software ABAQUS are presented to validate the effectiveness of the proposed mathematic model.

  2. Weathering a Dynamic Seascape: Influences of Wind and Rain on a Seabird's Year-Round Activity Budgets.

    PubMed

    Pistorius, Pierre A; Hindell, Mark A; Tremblay, Yann; Rishworth, Gavin M

    2015-01-01

    How animals respond to varying environmental conditions is fundamental to ecology and is a question that has gained impetus due to mounting evidence indicating negative effects of global change on biodiversity. Behavioural plasticity is one mechanism that enables individuals and species to deal with environmental changes, yet for many taxa information on behavioural parameters and their capacity to change are lacking or restricted to certain periods within the annual cycle. This is particularly true for seabirds where year-round behavioural information is intrinsically challenging to acquire due to their reliance on the marine environment where they are difficult to study. Using data from over 13,000 foraging trips throughout the annual cycle, acquired using new-generation automated VHF technology, we described sex-specific, year-round activity budgets in Cape gannets. Using these data we investigated the role of weather (wind and rain) on foraging activity and time allocated to nest attendance. Foraging activity was clearly influenced by wind speed, wind direction and rainfall during and outside the breeding season. Generally, strong wind conditions throughout the year resulted in relatively short foraging trips. Birds spent longer periods foraging when rainfall was moderate. Nest attendance, which was sex-specific outside of the breeding season, was also influenced by meteorological conditions. Large amounts of rainfall (> 2.5 mm per hour) and strong winds (> 13 m s-1) resulted in gannets spending shorter amounts of time at their nests. We discuss these findings in terms of life history strategies and implications for the use of seabirds as bio-indicators.

  3. High Lift Common Research Model for Wind Tunnel Testing: An Active Flow Control Perspective

    NASA Technical Reports Server (NTRS)

    Lin, John C.; Melton, Latunia P.; Viken, Sally A.; Andino, Marlyn Y.; Koklu, Mehti; Hannon, Judith A.; Vatsa, Veer N.

    2017-01-01

    This paper provides an overview of a research and development effort sponsored by the NASA Advanced Air Transport Technology Project to achieve the required high-lift performance using active flow control (AFC) on simple hinged flaps while reducing the cruise drag associated with the external mechanisms on slotted flaps of a generic modern transport aircraft. The removal of the external fairings for the Fowler flap mechanism could help to reduce drag by 3.3 counts. The main challenge is to develop an AFC system that can provide the necessary lift recovery on a simple hinged flap high-lift system while using the limited pneumatic power available on the aircraft. Innovative low-power AFC concepts will be investigated in the flap shoulder region. The AFC concepts being explored include steady blowing and unsteady blowing operating in the spatial and/or temporal domain. Both conventional and AFC-enabled high-lift configurations were designed for the current effort. The high-lift configurations share the cruise geometry that is based on the NASA Common Research Model, and therefore, are also open geometries. A 10%-scale High Lift Common Research Model (HL-CRM) is being designed for testing at the NASA Langley Research Center 14- by 22-Foot Subsonic Tunnel during fiscal year 2018. The overall project plan, status, HL-CRM configurations, and AFC objectives for the wind tunnel test are described.

  4. Solar flare acceleration of solar wind: influence of active region magnetic field.

    PubMed

    Lundstedt, H; Wilcox, J M; Scherrer, P H

    1981-06-26

    The direction of the photospheric magnetic field at the site of a solar flare is a good predictor of whether the flare will accelerate solar wind plasma. If the field has a southward component, high-speed solar wind plasma is usually observed near the earth about 4 days later. If the field has a northward component, such high-speed solar wind is almost never observed. Southward-field flares may then be expected to have much larger terrestrial effects than northward flares.

  5. A Long Neglected Damper in the El Niño--Typhoon Relationship: a 'Gaia-Like' Process.

    PubMed

    Zheng, Zhe-Wen; Lin, I-I; Wang, Bin; Huang, Hsiao-Ching; Chen, Chi-Hong

    2015-07-21

    Proposed in the early 1970's, the Gaia hypothesis suggests that our planet earth has a self-regulating ability to maintain a stable condition for life. Tropical cyclone (TC) is one of the earth's most hazardous disasters; it is intriguing to explore whether 'Gaia-like' processes may exist in nature to regulate TC activities. El Niño can shift the forming position of the Western Pacific typhoons away from land. This shift enables typhoons to travel longer distances over ocean and is known to be a positive process to promote TCs to achieve higher intensity. What is neglected, however, is that there co-exists a negative process. Here we show that during El Niño, typhoons intensify over region undergoing strong ocean subsurface shoaling where upper ocean heat content can drop by 20-50%. This 'worsen' ocean pre-condition can effectively reduce ocean's energy supply for typhoon intensification during typhoon-ocean interaction. We find this an elegant, 'Gaia-like' process demonstrating nature's self-regulating ability. Though during El Niño, typhoons can take advantage of the longer travelling distance over ocean to achieve higher intensity, nature is also providing a damper to partially cancel this positive impact. Without the damper, the situation could be even worse.

  6. Wind power today

    SciTech Connect

    1998-04-01

    This publication highlights initiatives of the US DOE`s Wind Energy Program. 1997 yearly activities are also very briefly summarized. The first article describes a 6-megawatt wind power plant installed in Vermont. Another article summarizes technical advances in wind turbine technology, and describes next-generation utility and small wind turbines in the planning stages. A village power project in Alaska using three 50-kilowatt turbines is described. Very brief summaries of the Federal Wind Energy Program and the National Wind Technology Center are also included in the publication.

  7. A modelling framework to predict bat activity patterns on wind farms: An outline of possible applications on mountain ridges of North Portugal.

    PubMed

    Silva, Carmen; Cabral, João Alexandre; Hughes, Samantha Jane; Santos, Mário

    2017-03-01

    Worldwide ecological impact assessments of wind farms have gathered relevant information on bat activity patterns. Since conventional bat study methods require intensive field work, the prediction of bat activity might prove useful by anticipating activity patterns and estimating attractiveness concomitant with the wind farm location. A novel framework was developed, based on the stochastic dynamic methodology (StDM) principles, to predict bat activity on mountain ridges with wind farms. We illustrate the framework application using regional data from North Portugal by merging information from several environmental monitoring programmes associated with diverse wind energy facilities that enable integrating the multifactorial influences of meteorological conditions, land cover and geographical variables on bat activity patterns. Output from this innovative methodology can anticipate episodes of exceptional bat activity, which, if correlated with collision probability, can be used to guide wind farm management strategy such as halting wind turbines during hazardous periods. If properly calibrated with regional gradients of environmental variables from mountain ridges with windfarms, the proposed methodology can be used as a complementary tool in environmental impact assessments and ecological monitoring, using predicted bat activity to assist decision making concerning the future location of wind farms and the implementation of effective mitigation measures.

  8. Statistical study of the effect of wind characteristics on the main shaft loadings of an active-stall controlled wind turbine

    NASA Astrophysics Data System (ADS)

    Oh, Sho

    2016-09-01

    The dynamic loadings of the wind turbine main shafts are important for drivetrain components as external excitation force, and the evaluation of their dependence on wind characteristics is necessary for both the understanding of the drivetrain bahavior and the extrapolation of the loadings at different sites. In this study, the load measurements of the wind turbine main shafts were performed along with the wind field measurement. Next the multivariate regression analysis was utilized to identify the influential wind parameters that affect the statistics of the dynamic loadings of the shaft. Finally, the dependence of the load statistics on the identified wind parameters was evaluated qualitatively using the observed data. Obtained regression results showed that there were more effects of wind field parameters on shaft loadings at low and middle wind speed regions than at the high wind speed region. Among the identified parameters, the incline angle and the vertical turbulence were found to be dominant for most of the shaft loadings, though the turbulence intensity is the parameter that is generally used for characterization of a wind field. For the mean tilt bending moment and the standard deviation of the torque, which are recognized as the influential factors for the loadings of drivetrain component, the differences the identified parameters caused were about 15% and 100% respectively.

  9. Design and characterization of axial flux permanent magnet energy harvester for vehicle magnetorheological damper

    NASA Astrophysics Data System (ADS)

    Dong, Xiaomin

    2016-01-01

    An axial flux permanent magnet energy harvester (AFPMEH) is proposed and analyzed for a vehicle magneto-rheological (MR) damper. The relationship between the output voltage and the input excitations are analytically developed. Under different constant rotation speeds and sinusoidal excitations, the harvesting energy is numerically computed for different loads of pure resistance and coil in the MR damper. To check the performance of the proposed AFPMEH for the MR damper, the AFPMEH and MR damper are fabricated individually. Experiments are performed to measure the harvesting energy of the AFPMEH and the damping characteristics of the MR damper under different excited conditions. The excited conditions include three constant rotation speeds and sinusoidal inputs. Load inputs of the pure resistance and the coil of the MR damper are considered. The results show that the time history of the generated voltage of the AFPMEH in experiment is agreed well with that of the AFPMEH in simulation. Under constant rotation speeds, the root mean square (rms) of loaded voltage will increase with the increment of load, whereas the rms of power will be affected by the amplitude of load. The MR damper powered by the AFPMEH can almost obtain the similar damping characteristics of that external power supply. Under sinusoidal inputs, the rms of loaded voltage will increase with the increment of external loads, whereas the rms of power will be almost kept as a constant. The damping range of the MR damper can also be enlarged over 30% comparing to off-state damping force. A quarter car model with an MR damper powered by the AFPMEH is developed to investigate the control performance. The on-off skyhook control is adopted to tune the input current of the MR damper. The vibration performance of the MR suspension is investigated under different roads and vehicle speeds. The numerical results show that the MR suspension with the AFPMEH under on-off skyhook control can achieve better ride comfort

  10. The influence of solar active region evolution on solar wind streams, coronal hole boundaries and geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Gold, R. E.; Dodson-Prince, H. W.; Hedeman, E. R.; Roelof, E. C.

    Solar and interplanetary data are examined, taking into account the identification of the heliographic longitudes of the coronal source regions of high speed solar wind (SW) streams by Nolte and Roelof (1973). Nolte and Roelof have 'mapped' the velocities measured near earth back to the sun using the approximation of constant radial velocity. The 'Carrington carpet' for rotations 1597-1616 is shown in a graph. Coronal sources of high speed streams appear in the form of solid black areas. The contours of the stream sources are laid on 'evolutionary charts' of solar active region histories for the Southern and Northern Hemispheres. Questions regarding the interplay of active regions and solar wind are investigated, giving attention to developments during the years 1973, 1974, and 1975.

  11. Active Power Control of Wind Turbines for Ancillary Services: A Comparison of Pitch and Torque Control Methodologies

    SciTech Connect

    Aho, Jacob; Fleming, Paul; Pao, Lucy Y.

    2016-08-01

    As wind energy generation becomes more prevalent in some regions, there is increased demand for wind power plants to provide ancillary services, which are essential for grid reliability. This paper compares two different wind turbine control methodologies to provide active power control (APC) ancillary services, which include derating or curtailing power generation, providing automatic generation control (AGC), and providing primary frequency control (PFC). The torque APC controller provides all power control through the power electronics whereas the pitch APC controller uses the blade pitch actuators as the primary means of power control. These controllers are simulated under various wind conditions with different derating set points and AGC participation levels. The metrics used to compare their performance are the damage equivalent loads (DELs) induced on the structural components and AGC performance metrics, which are used to determine the payments for AGC services by system operators in the United States. The simulation results show that derating the turbine reduces structural loads for both control methods, with the APC pitch control providing larger reductions in DELs, lower AGC performance scores, and higher root-mean-square pitch rates. Providing AGC increases the structural loads when compared to only derating the turbine, but even the AGC DELs are generally lower than those of the baseline control system. The torque APC control methodology also allows for more sustained PFC responses under certain derating conditions.

  12. Upper Thermosphere Winds and Temperatures in the Geomagnetic Polar Cap: Solar Cycle, Geomagnetic Activity, and Interplanetary Magnetic Field Dependencies

    NASA Technical Reports Server (NTRS)

    Killeen, T. L.; Won, Y.-I.; Niciejewski, R. J.; Burns, A. G.

    1995-01-01

    Ground-based Fabry-Perot interferometers located at Thule, Greenland (76.5 deg. N, 69.0 deg. W, lambda = 86 deg.) and at Sondre Stromfjord, Greenland (67.0 deg. N, 50.9 deg. W, lambda = 74 deg.) have monitored the upper thermospheric (approx. 240-km altitude) neutral wind and temperature over the northern hemisphere geomagnetic polar cap since 1983 and 1985, respectively. The thermospheric observations are obtained by determining the Doppler characteristics of the (OI) 15,867-K (630.0-nm) emission of atomic oxygen. The instruments operate on a routine, automatic, (mostly) untended basis during the winter observing seasons, with data coverage limited only by cloud cover and (occasional) instrument failures. This unique database of geomagnetic polar cap measurements now extends over the complete range of solar activity. We present an analysis of the measurements made between 1985 (near solar minimum) and 1991 (near solar maximum), as part of a long-term study of geomagnetic polar cap thermospheric climatology. The measurements from a total of 902 nights of observations are compared with the predictions of two semiempirical models: the Vector Spherical Harmonic (VSH) model of Killeen et al. (1987) and the Horizontal Wind Model (HWM) of Hedin et al. (1991). The results are also analyzed using calculations of thermospheric momentum forcing terms from the Thermosphere-ionosphere General Circulation Model TGCM) of the National Center for Atmospheric Research (NCAR). The experimental results show that upper thermospheric winds in the geomagnetic polar cap have a fundamental diurnal character, with typical wind speeds of about 200 m/s at solar minimum, rising to up to about 800 m/s at solar maximum, depending on geomagnetic activity level. These winds generally blow in the antisunward direction, but are interrupted by episodes of modified wind velocity and altered direction often associated with changes in the orientation of the Interplanetary Magnetic Field (IMF). The

  13. Large wind turbine generators

    NASA Technical Reports Server (NTRS)

    Thomas, R. L.; Donovon, R. M.

    1978-01-01

    The development associated with large wind turbine systems is briefly described. The scope of this activity includes the development of several large wind turbines ranging in size from 100 kW to several megawatt levels. A description of the wind turbine systems, their programmatic status and a summary of their potential costs is included.

  14. Wind River watershed restoration: Annual report of U.S. Geological Survey activities November 2010 – October 2011

    USGS Publications Warehouse

    Jezorek, Ian G.; Connolly, Patrick J.; Munz, Carrie S.

    2012-01-01

    This report summarizes work completed by U.S. Geological Survey’s Columbia River Research Laboratory (USGS-CRRL) in the Wind River subbasin during November 2010 through October 2011 under Bonneville Power Administration (BPA) contract 40481. The primary focus of USGS activities during this contract was on tagging of juvenile steelhead Oncorhynchus mykiss with Passive Integrated Transponder (PIT) tags, and working toward a network of instream PIT tag detection systems to monitor movements and life histories of these fish.

  15. Galactic Winds

    NASA Astrophysics Data System (ADS)

    Veilleux, Sylvain

    Galactic winds have become arguably one of the hottest topics in extragalactic astronomy. This enthusiasm for galactic winds is due in part to the detection of winds in many, if not most, high-redshift galaxies. Galactic winds have also been invoked by theorists to (1) suppress the number of visible dwarf galaxies and avoid the "cooling catastrophe" at high redshift that results in the overproduction of massive luminous galaxies, (2) remove material with low specific angular momentum early on and help enlarge gas disks in CDM + baryons simulations, (3) reduce the dark mass concentrations in galaxies, (4) explain the mass-metallicity relation of galaxies from selective loss of metal-enriched gas from smaller galaxies, (5) enrich and "preheat" the ICM, (6) enrich the IGM without disturbing the Lyαforest significantly, and (7) inhibit cooling flows in galaxy clusters with active cD galaxies. The present paper highlights a few key aspects of galactic winds taken from a recent ARAA review by Veilleux, Cecil, &Bland-Hawthorn (2005; herafter VCBH). Readers interested in a more detailed discussion of this topic are encouraged to refer to the original ARAA article.

  16. Rheological controllability of double-ended MR dampers subjected to impact loading

    NASA Astrophysics Data System (ADS)

    Ahmadian, Mehdi; Norris, James A.

    2004-07-01

    The vast majorities of the applications of MR dampers have been for transportation applications-mainly shock absorbers for automobile suspensions, heavy truck seats, and racecar suspensions-where the MR device is not subjected to very high velocities. For these applications, as well as many others, although the MR device is most often subjected to relatively low velocities, the MR fluid which passes through a narrow piston gap can experience very high velocities and shear rates. Yet, there is very little known about the dynamics of MR fluids at these very high shear rates. This study will provide some of the results from an extensive experimental study that was conducted on the impact dynamics of MR dampers, at the Advanced Vehicle Dynamics Laboratory of Virginia Tech. For brevity, the results that are included in this paper are limited to those for a double-ended MR damper, which is most suitable for impact applications. For an impact velocity of 160 in/s and drop mass of 55 lb, the results indicate that the double-ended MR damper transmits relatively large forces, which are hypothesized to be due to the large size of the damper and the large amount of MR fluid that needs to be accelerated in the damper. For all of the tests on the double-ended MR damper, the fluid became controllable once the piston velocity dropped below a threshold value. The relationship between the threshold value and fluid characteristics showed that the transition to controllable tended to occur at about the same point as the transitioning of the fluid flow from turbulent to laminar.

  17. Passive Acoustic Detection of Wind Turbine In-Flow Conditions for Active Control and Optimization

    SciTech Connect

    Murray, Nathan E.

    2012-03-12

    Wind is a significant source of energy; however, the human capability to produce electrical energy still has many hurdles to overcome. One of these is the unpredictability of the winds in the atmospheric boundary layer (ABL). The ABL is highly turbulent in both stable and unstable conditions (based on the vertical temperature profile) and the resulting fluctuations can have a dramatic impact on wind turbine operation. Any method by which these fluctuations could be observed, estimated, or predicted could provide a benefit to the wind energy industry as a whole. Based on the fundamental coupling of velocity fluctuations to pressure fluctuations in the nearly incompressible flow in the ABL, This work hypothesizes that a ground-based array of infrasonic pressure transducers could be employed to estimate the vertical wind profile over a height relevant for wind turbines. To analyze this hypothesis, experiments and field deployments were conducted. Wind tunnel experiments were performed for a thick turbulent boundary layer over a neutral or heated surface. Surface pressure and velocity probe measurements were acquired simultaneously. Two field deployments yielded surface pressure data from a 49 element array. The second deployment at the Reese Technology Center in Lubbock, TX, also included data from a smaller aperture, 96-element array and a 200-meter tall meteorological tower. Analysis of the data successfully demonstrated the ability to estimate the vertical velocity profile using coherence data from the pressure array. Also, dynamical systems analysis methods were successful in identifying and tracking a gust type event. In addition to the passive acoustic profiling method, this program also investigated a rapid response Doppler SODAR system, the optimization of wind turbine blades for enhanced power with reduced aeroacoustic noise production, and the implementation of a wireless health monitoring system for the wind turbine blades. Each of these other objectives

  18. Lightning activity and its relationship with typhoon intensity and vertical wind shear for Super Typhoon Haiyan (1330)

    NASA Astrophysics Data System (ADS)

    Wang, Fang; Qie, Xiushu; Liu, Dongxia; Shi, Haifeng; Srivastava, Abhay

    2016-02-01

    Super Typhoon Haiyan (1330), which occurred in 2013, is the most powerful typhoon during landfall in the meteorological record. In this study, the temporal and spatial distributions of lightning activity of Haiyan were analyzed by using the lightning data from the World Wide Lightning Location Network, typhoon intensity and position data from the China Meteorological Administration, and horizontal wind data from the ECMWF. Three distinct regions were identified in the spatial distribution of daily average lightning density, with the maxima in the inner core and the minima in the inner rainband. The lightning density in the intensifying stage of Haiyan was greater than that in its weakening stage. During the time when the typhoon intensity measured with maximum sustained wind speed was between 32.7 and 41.4 ms-1, the storm had the largest lightning density in the inner core, compared with other intensity stages. In contrast to earlier typhoon studies, the eyewall lightning burst out three times. The first two eyewall lightning outbreaks occurred during the period of rapid intensification and before the maximum intensity of the storm, suggesting that the eyewall lightning activity could be used to identify the change in tropical cyclone intensity. The flashes frequently occurred in the inner core, and in the outer rainbands with the black body temperature below 220 K. Combined with the ECMWF wind data, the influences of vertical wind shear (VWS) on the azimuthal distribution of flashes were also analyzed, showing that strong VWS produced downshear left asymmetry of lightning activity in the inner core and downshear right asymmetry in the rainbands.

  19. Application of two passive strategies on the load mitigation of large offshore wind turbines

    NASA Astrophysics Data System (ADS)

    Shirzadeh, Rasoul; Kühn, Martin

    2016-09-01

    This study presents the numerical results of two passive strategies to reduce the support structure loads of a large offshore wind turbine. In the first approach, an omnidirectional tuned mass damper is designed and implemented in the tower top to alleviate the structural vibrations. In the second approach, a viscous fluid damper model which is diagonally attached to the tower at two points is developed. Aeroelastic simulations are performed for the offshore 10MW INNWIND.EU reference wind turbine mounted on a jacket structure. Lifetime damage equivalent loads are evaluated at the tower base and compared with those for the reference wind turbine. The results show that the integrated design can extend the lifetime of the support structure.

  20. 2012 wind technologies market report

    SciTech Connect

    Wiser, Ryan; Bolinger, Mark; Barbose, Galen; Darghouth, Naim; Hoen, Ben; Mills, Andrew; Weaver, Samantha; Porter, Kevin; Buckley, Michael; Fink, Sari; Oteri, Frank; Tegen, Suzanne

    2013-07-01

    Annual wind power capacity additions in the United States achieved record levels in 2012, motivated by the then-planned expiration of federal tax incentives at the end of 2012 and recent improvements in the cost and performance of wind power technology. At the same time, even with a short-term extension of federal tax incentives now in place, the U.S. wind power industry is facing uncertain times. It will take time to rebuild the project pipeline, ensuring a slow year for new capacity additions in 2013. Continued low natural gas prices, modest electricity demand growth, and limited near-term demand from state renewables portfolio standards (RPS) have also put a damper on industry growth expectations. In combination with global competition within the sector, these trends continue to impact the manufacturing supply chain. What these trends mean for the medium to longer term remains to be seen, dictated in part by future natural gas prices, fossil plant retirements, and policy decisions, although recent declines in the price of wind energy have boost ed the prospects for future growth

  1. Contributions to modeling functionality of a high frequency damper system

    NASA Astrophysics Data System (ADS)

    Sirbu, E. A.; Horga, S.; Vrabioiu, G.

    2016-08-01

    Due to the necessity of improving the handling performances of a motor vehicle, it is imperative to understand the suspensions properties that affects ride and directional respons.The construction of a fero-magnetic shock absorber is based on two bellows interconnected by a pipe-line. Through this pipe-line the fero-magnetic fluid is carried between the two bellows. The damping characteristic of the shock absorber is affected by the viscosity of the fero-magnetic fluid. The viscosity of the fluid, is controlled through a electric coil mounted on the bellows connecting pipe-line. Modifying the electrical field of the coil, the viscosity of the fluid will change, finally affecting the damping characteristic of the shock absorber. A recent system called „CCD Pothole Suspension” is implemented on Ford vehicles. By modifying the dampning characteristic of the shock absorbers, vehicle daynamics can be improved; also the risk of damaging the suspension will be decreased. The approach of this paper is to analyze the behaviour of the fero magnetic damper, thus determining how it will affect the performances of the vehicle suspensions. The experimental research will provide a better understanding of the behavior of the fero-magnetic shock absorber, and the possible advantages of using this system.

  2. Innovative modeling of Tuned Liquid Column Damper motion

    NASA Astrophysics Data System (ADS)

    Di Matteo, A.; Lo Iacono, F.; Navarra, G.; Pirrotta, A.

    2015-06-01

    In this paper a new model for the liquid motion within a Tuned Liquid Column Damper (TLCD) device is developed, based on the mathematical tool of fractional calculus. Although the increasing use of these devices for structural vibration control, it is shown that existing model does not always lead to accurate prediction of the liquid motion. A better model is then needed for accurate simulation of the behavior of TLCD systems. As regards, it has been demonstrated how correctly including the first linear liquid sloshing mode, through the equivalent mechanical analogy well established in literature, produces numerical results that highly match the corresponding experimental ones. Since the apparent effect of sloshing is the deviation of the natural frequency from the theoretical one, the authors propose a fractional differential equation of motion. The latter choice is supported by the fact that the introduction a fractional derivative of order α alters simultaneously both the resonant frequency and the degree of damping of the system. It will be shown, through an extensive experimental analysis, how the proposed model accurately describes liquid surface displacements.

  3. Dynamic characteristics of Non Newtonian fluid Squeeze film damper

    NASA Astrophysics Data System (ADS)

    Palaksha, C. P.; Shivaprakash, S.; Jagadish, H. P.

    2016-09-01

    The fluids which do not follow linear relationship between rate of strain and shear stress are termed as non-Newtonian fluid. The non-Newtonian fluids are usually categorized as those in which shear stress depends on the rates of shear only, fluids for which relation between shear stress and rate of shear depends on time and the visco inelastic fluids which possess both elastic and viscous properties. It is quite difficult to provide a single constitutive relation that can be used to define a non-Newtonian fluid due to a great diversity found in its physical structure. Non-Newtonian fluids can present a complex rheological behaviour involving shear-thinning, viscoelastic or thixotropic effects. The rheological characterization of complex fluids is an important issue in many areas. The paper analyses the damping and stiffness characteristics of non-Newtonian fluids (waxy crude oil) used in squeeze film dampers using the available literature for viscosity characterization. Damping and stiffness characteristic will be evaluated as a function of shear strain rate, temperature and percentage wax concentration etc.

  4. Rheological properties of bi-dispersed magnetorheological fluids based on plate-like iron particles with application to a small-sized damper

    NASA Astrophysics Data System (ADS)

    Shah, Kruti; Xuan Phu, Do; Choi, Seung-Bok

    2014-05-01

    In this study, the rheological properties and an application of bi-dispersed magnetorheological fluid (MRF) based on plate-like iron particles are experimentally investigated. A bi-dispersed MR Fluid is prepared using two different micron-scale sizes of plate-like iron particles. In the absence of a magnetic field, the properties of the fluid are isotropic. Upon the application of a magnetic field, the magnetized particles form a chain aligned in the direction of the field, which promotes the appearance of a yield stress. The reversible transition from solid to liquid is the basic requirement of MR applications. Due to the anisotropy in the shape and formation of a less compact structure in the iron plate-like particles, weak sedimentation and good redispersibility of the proposed MR fluid are created. The physical properties of the proposed MR fluids are evaluated and applied to the design of a small-sized controllable MR vibration damper, which can be used for vibration control of a washing machine. The MR damper is a semi-active device that dissipates energy during vibration motion to increase the stability of the application system. Three different weight fractions of the bi-dispersed MR fluids are prepared, and their rheological properties are presented and discussed. Based on their rheological properties, the figures of merit of the proposed MR fluids are derived. A comparison of these figures of merit gives the nominal behavior of the MR fluids, which are important in the design of the application device. A stability test is also performed to check the settling rate of MR fluids per day. The change in damping force due to the problem of particles settling in the MRF and the field-dependent damping force are measured with the MR damper operated just after filling the MRF and with the MR damper operated after waiting for 48 h after filling. With basic rheological properties and outstanding mechanical properties, it is clearly demonstrated that the proposed MR

  5. Modelling the nonlinear behaviour of an underplatform damper test rig for turbine applications

    NASA Astrophysics Data System (ADS)

    Pesaresi, L.; Salles, L.; Jones, A.; Green, J. S.; Schwingshackl, C. W.

    2017-02-01

    Underplatform dampers (UPD) are commonly used in aircraft engines to mitigate the risk of high-cycle fatigue failure of turbine blades. The energy dissipated at the friction contact interface of the damper reduces the vibration amplitude significantly, and the couplings of the blades can also lead to significant shifts of the resonance frequencies of the bladed disk. The highly nonlinear behaviour of bladed discs constrained by UPDs requires an advanced modelling approach to ensure that the correct damper geometry is selected during the design of the turbine, and that no unexpected resonance frequencies and amplitudes will occur in operation. Approaches based on an explicit model of the damper in combination with multi-harmonic balance solvers have emerged as a promising way to predict the nonlinear behaviour of UPDs correctly, however rigorous experimental validations are required before approaches of this type can be used with confidence. In this study, a nonlinear analysis based on an updated explicit damper model having different levels of detail is performed, and the results are evaluated against a newly-developed UPD test rig. Detailed linear finite element models are used as input for the nonlinear analysis, allowing the inclusion of damper flexibility and inertia effects. The nonlinear friction interface between the blades and the damper is described with a dense grid of 3D friction contact elements which allow accurate capturing of the underlying nonlinear mechanism that drives the global nonlinear behaviour. The introduced explicit damper model showed a great dependence on the correct contact pressure distribution. The use of an accurate, measurement based, distribution, better matched the nonlinear dynamic behaviour of the test rig. Good agreement with the measured frequency response data could only be reached when the zero harmonic term (constant term) was included in the multi-harmonic expansion of the nonlinear problem, highlighting its importance

  6. The distant future of solar activity: A case study of Beta Hydri. III - Transition region, corona, and stellar wind

    NASA Technical Reports Server (NTRS)

    Dravins, D.; Linde, P.; Ayres, T. R.; Linsky, J. L.; Monsignori-Fossi, B.; Simon, T.; Wallinder, F.

    1993-01-01

    The paper investigates the secular decay of solar-type activity through a detailed comparison of the present sun with the very old solar-type star, Beta Hyi, taken as a proxy of the future sun. Analyses of successive atmospheric layers are presented, with emphasis of the outermost parts. The FUV emission lines for the transition zone are among the faintest so far seen in any solar-type star. The coronal soft X-ray spectrum was measured through different filters on EXOSAT and compared to simulated X-ray observations of the sun seen as a star. The flux from Beta Hyi is weaker than that from the solar corona and has a different spectrum. It is inferred that a thermally driven stellar wind can no longer be supported, which removes the mechanism from further rotational braking of the star through a magnetic stellar wind.

  7. Development and performance evaluation of an MR squeeze-mode damper

    NASA Astrophysics Data System (ADS)

    Sapiński, Bogdan; Gołdasz, Janusz

    2015-11-01

    In this paper the authors present results of a magnetorheological (MR) damper prototype development and performance evaluation study. The damper is a device functioning in the so-called squeeze-mode of MR fluid flow regime of operation. By principle, in a squeeze-mode damper the control (working) gap height varies according to the prescribed displacement or force input profile. Such hardware has been claimed to be well suited to small-amplitude vibration damping applications. However, it is still in its infancy. Its potential seems appealing yet unclear. Accordingly, the authors reveal performance figures of the damper complemented by numerical finite-element simulations of the electro-magnetic circuit of the device. The numerical results are presented in the form of maps of averaged magnetic flux density versus coil current and gap height as well as magnetic flux, inductance, and cogging force calculations, respectively. The simulated data are followed by experimental evaluation of the damper performance incorporating plots of force versus piston displacement (velocity) across a prescribed range of excitation inputs. Moreover, some insight into transient (unsteady) characteristics of the device is provided through testing results involving transient currents.

  8. Optimal Design of Spring Characteristics of Damper for Subharmonic Vibration in Automatic Transmission Powertrain

    NASA Astrophysics Data System (ADS)

    Nakae, T.; Ryu, T.; Matsuzaki, K.; Rosbi, S.; Sueoka, A.; Takikawa, Y.; Ooi, Y.

    2016-09-01

    In the torque converter, the damper of the lock-up clutch is used to effectively absorb the torsional vibration. The damper is designed using a piecewise-linear spring with three stiffness stages. However, a nonlinear vibration, referred to as a subharmonic vibration of order 1/2, occurred around the switching point in the piecewise-linear restoring torque characteristics because of the nonlinearity. In the present study, we analyze vibration reduction for subharmonic vibration. The model used herein includes the torque converter, the gear train, and the differential gear. The damper is modeled by a nonlinear rotational spring of the piecewise-linear spring. We focus on the optimum design of the spring characteristics of the damper in order to suppress the subharmonic vibration. A piecewise-linear spring with five stiffness stages is proposed, and the effect of the distance between switching points on the subharmonic vibration is investigated. The results of our analysis indicate that the subharmonic vibration can be suppressed by designing a damper with five stiffness stages to have a small spring constant ratio between the neighboring springs. The distances between switching points must be designed to be large enough that the amplitude of the main frequency component of the systems does not reach the neighboring switching point.

  9. Leak testing of bubble-tight dampers using tracer gas techniques

    SciTech Connect

    Lagus, P.L.; DuBois, L.J.; Fleming, K.M.

    1995-02-01

    Recently tracer gas techniques have been applied to the problem of measuring the leakage across an installed bubble-tight damper. A significant advantage of using a tracer gas technique is that quantitative leakage data are obtained under actual operating differential pressure conditions. Another advantage is that leakage data can be obtained using relatively simple test setups that utilize inexpensive materials without the need to tear ducts apart, fabricate expensive blank-off plates, and install test connections. Also, a tracer gas technique can be used to provide an accurate field evaluation of the performance of installed bubble-tight dampers on a periodic basis. Actual leakage flowrates were obtained at Zion Generating Station on four installed bubble-tight dampers using a tracer gas technique. Measured leakage rates ranged from 0.01 CFM to 21 CFM. After adjustment and subsequent retesting, the 21 CFM damper leakage was reduced to a leakage of 3.8 CFM. In light of the current regulatory climate and the interest in Control Room Habitability issues, imprecise estimates of critical air boundary leakage rates--such as through bubble-tight dampers--are not acceptable. These imprecise estimates can skew radioactive dose assessments as well as chemical contaminant exposure calculations. Using a tracer gas technique, the actual leakage rate can be determined. This knowledge eliminates a significant source of uncertainty in both radioactive dose and/or chemical exposure assessments.

  10. A review of acoustic dampers applied to combustion chambers in aerospace industry

    NASA Astrophysics Data System (ADS)

    Zhao, Dan; Li, X. Y.

    2015-04-01

    In engine combustion systems such as rockets, aero-engines and gas turbines, pressure fluctuations are always present, even during normal operation. One of design prerequisites for the engine combustors is stable operation, since large-amplitude self-sustained pressure fluctuations (also known as combustion instability) have the potential to cause serious structural damage and catastrophic engine failure. To dampen pressure fluctuations and to reduce noise, acoustic dampers are widely applied as a passive control means to stabilize combustion/engine systems. However, they cannot respond to the dynamic changes of operating conditions and tend to be effective over certain narrow range of frequencies. To maintain their optimum damping performance over a broad frequency range, extensive researches have been conducted during the past four decades. The present work is to summarize the status, challenges and progress of implementing such acoustic dampers on engine systems. The damping effect and mechanism of various acoustic dampers, such as Helmholtz resonators, perforated liners, baffles, half- and quarter-wave tube are introduced first. A summary of numerical, experimental and theoretical studies are then presented to review the progress made so far. Finally, as an alternative means, ';tunable acoustic dampers' are discussed. Potential, challenges and issues associated with the dampers practical implementation are highlighted.

  11. Vibration Reduction of Helicopter Blade Using Variable Dampers: A Feasibility Study

    NASA Technical Reports Server (NTRS)

    Lee, George C.; Liang, Zach; Gan, Quan; Niu, Tiecheng

    2002-01-01

    In the report, the investigation of controlling helicopter-blade lead-lag vibration is described. Current practice of adding passive damping may be improved to handle large dynamic range of the blade with several peaks of vibration resonance. To minimize extra-large damping forces that may damage the control system of blade, passive dampers should have relatively small damping coefficients, which in turn limit the effectiveness. By providing variable damping, a much larger damping coefficient to suppress the vibration can be realized. If the damping force reaches the maximum allowed threshold, the damper will be automatically switched into the mode with smaller damping coefficient to maintain near-constant damping force. Furthermore, the proposed control system will also have a fail-safe feature to guarantee the basic performation of a typical passive damper. The proposed control strategy to avoid resonant regions in the frequency domain is to generate variable damping force in combination with the supporting stiffness to manipulate the restoring force and conservative energy of the controlled blade system. Two control algorithms are developed and verified by a prototype variable damper, a digital controller and corresponding algorithms. Primary experiments show good potentials for the proposed variable damper: about 66% and 82% reductions in displacement at 1/3 length and the root of the blade respectively.

  12. Collective Response of Leaf-Cutting Ants to the Effects of Wind on Foraging Activity.

    PubMed

    Alma, Andrea Marina; Farji-Brener, Alejandro G; Elizalde, Luciana

    2016-11-01

    One advantage of sociality is to mitigate environmental restrictions through collective behavior. Here we document a colony-level response of leaf-cutting ants to wind, an environmental factor that impedes foraging. Given that larger ants adhere more strongly to the substrate, increasing forager size in windy conditions should reduce the negative effect of wind. We tested this idea for Acromyrmex lobicornis in windy regions of Patagonia. We examined (1) whether the fraction of larger ants versus smaller ants increased in windy conditions and (2) whether the effect of wind on the ants' movement was lower for larger ants. The size-frequency distribution of foragers was skewed more toward larger ants in nature under more windy conditions. Under windy conditions in the field, the mobility of smaller ants was more reduced than that of larger ants. The change toward larger foragers in windy conditions reduced the negative effect of wind by 32%, illustrating how a social organism can collectively mitigate the adverse effects of the environment.

  13. Solar wind quasi-invariant as a heliospheric index of solar activity

    NASA Astrophysics Data System (ADS)

    Fainberg, J.; Osherovich, V. A.

    2002-12-01

    Interplanetary magnetic field strength B, solar wind speed v and plasma density ρ all vary with sunspot numbers (SSN). The corresponding correlation coefficients (cc) are not high enough to establish any of these parameters as a close proxy for SSN. In contrast, the solar wind quasi-invariant [QI ≡ (B2/8π)/(ρv2/2)] recently suggested by Osherovich, Fainberg and Stone [1999] has a high cc = 0.98 for the median yearly value for the 28 year period measured in the solar wind near the Earth (1 AU). For the period 1978-1989, Voyager 2 measured B, v and ρ from 2 AU to 27 AU. In this paper we show that in spite of the orders of magnitude change of B and ρ at large heliospheric distances, QI measured by Voyager 2 stayed in the same range and followed SSN similar to QI measured near the Earth and near Venus. These results supply an observational test for any MHD model of the solar wind throughout the heliosphere that attempts to include the effects of solar cycle variability.

  14. Solar Wind Entry into the magnetosphere lobes and its Related Auroral activities

    NASA Astrophysics Data System (ADS)

    Shi, Q.; Gou, X.; Mailyan, B. G.; Maggiolo, R.; Zhang, Y.; Fu, S.; Zong, Q.; Parks, G. K.; Pu, Z.; Dunlop, M. W.

    2014-12-01

    Using Cluster multi-spacecrafts observation between August to October each year from 2002 to 2004, Shi, et al. [2013] have reported an unexpected discovery of regions of solar wind entry into the Earth's high-latitude magnetospheric lobes where the solar wind plasmas may penetrate into magnetosphere through high-latitude magnetic reconnection when the interplanetary magnetic field (IMF) is northward. From statistical analysis, they found that the IMF Bx component may influence the solar wind entry into the magnetosphere by changing the occurring conditions of high-latitude magnetic reconnection. Based on their studies, in this paper we use another period of Cluster data which is between January to April each year from 2001 to 2006 to do a further study. As a result, the influence of the IMF Bx component is consistent with the results from [Shi, et al. 2013]. We find that the IMF By component affects the events along with the IMF Bx component, which is consistent with the Parker Spiral of the IMF. We have also studied some transpolar arc observations in correlation with the solar wind entry events. The properties of entry plasma, electron and ion properties associated with aurorae are examined using multiple spacecraft data (Cluster, TIMED, DMSP, IMAGE and POLAR etc) , as can be seen from another work presented this meeting by Mailyan et al.

  15. 76 FR 80891 - Small Takes of Marine Mammals Incidental to Specified Activities; Cape Wind's High Resolution...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-27

    ... that NOAA ask the Department of the Interior (DOI) to defer further action on offshore wind leasing... expects some animals to avoid areas around the airgun array ensonified at the level of the exclusion zone... frequency range that takes place during a time when the animal is traveling through the open ocean,...

  16. 76 FR 40925 - Commercial Wind Lease Issuance and Site Characterization Activities on the Atlantic Outer...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-12

    ... CONTACT: Michelle Morin, BOEMRE Office of Offshore Alternative Energy Programs, 381 Elden Street, MS 4090... Offshore Alternative Energy Programs (MS 4090), Bureau of Ocean Energy Management, Regulation and... Bureau of Ocean Energy Management, Regulation and Enforcement Commercial Wind Lease Issuance and...

  17. Modernization and Activation of the NASA Ames 11- by 11-Foot Transonic Wind Tunnel

    NASA Technical Reports Server (NTRS)

    Kmak, Frank J.

    2000-01-01

    The Unitary Plan Wind Tunnel (UPWT) was modernized to improve performance, capability, productivity, and reliability. Automation systems were installed in all three UPWT tunnel legs and the Auxiliaries facility. Major improvements were made to the four control rooms, model support systems, main drive motors, and main drive speed control. Pressure vessel repairs and refurbishment to the electrical distribution system were also completed. Significant changes were made to improve test section flow quality in the 11-by 11-Foot Transonic leg. After the completion of the construction phase of the project, acceptance and checkout testing was performed to demonstrate the capabilities of the modernized facility. A pneumatic test of the tunnel circuit was performed to verify the structural integrity of the pressure vessel before wind-on operations. Test section turbulence, flow angularity, and acoustic parameters were measured throughout the tunnel envelope to determine the effects of the tunnel flow quality improvements. The new control system processes were thoroughly checked during wind-off and wind-on operations. Manual subsystem modes and automated supervisory modes of tunnel operation were validated. The aerodynamic and structural performance of both the new composite compressor rotor blades and the old aluminum rotor blades was measured. The entire subsonic and supersonic envelope of the 11-by 11-Foot Transonic leg was defined up to the maximum total pressure.

  18. An aeroelastician's perspective of wind tunnel and flight experiences with active control of structural response and stability

    NASA Technical Reports Server (NTRS)

    Hanson, P. W.

    1984-01-01

    Active controls technology is assessed based on a review of most of the wind-tunnel and flight tests and actual applications of active control concepts since the late sixties. The distinction is made between so-called ""rigid-body'' active control functions and those that involve significant modification of structural elastic response or stability. Both areas are reviewed although the focus is on the latter area. The basic goals and major results of the various studies or applications are summarized, and the anticipated use of active controls on current and near-future research and demonstration aircraft is discussed. Some of the ""holes'' remaining in the feasbility/benefits demonstration of active controls technology are examined.

  19. Interplanetary proton flux and solar wind conditions for different solar activities interacting with spacecraft and astronauts in space

    NASA Astrophysics Data System (ADS)

    Nejat, Cyrus

    2014-01-01

    The goal of this research is to determine the interplanetary proton flux and solar wind conditions by using data from several satellites such as Advanced Composition Explorer (ACE), Geostationary Operational Environmental Satellites (GOES) in particular GOES 9, GOES 11, GOES 12, GOES 13, and Solar Heliospheric Observatory (SOHO) to determine proton flux in different solar wind conditions. The data from above satellites were used to determine space weather conditions in which the goals are to evaluate proton fluxes for four periods of solar cycle activity: a solar cycle 23/24 minimum (2008), close to a solar cycle 22/23 minimum (1997), with intermediate activity (2011) and for about maximum activity for the cycle 23 (2003), to compare data of two period of solar cycle in 2003 and 2008 (Max vs. Min), to compare data of two period of solar cycle in 1997 and 2008 (Min vs. Min), to compare soft X-ray flux from SOHO with proton 1-10 MeV flux from GOES 9 for strong flare in 1997. To conclude the above evaluations are being used to determine the interaction between the space weather conditions and the following consequences of these conditions important for astronautics and everyday human activity: 1- Satellite and Spacecraft charging, 2-Dangerous conditions for onboard electronics and astronauts during strong solar flare events, and 3- Total Electron Content (TEC), Global Positioning System (GPS), and radio communication problems related to solar activity.

  20. A calculation method for torsional vibration of a crankshafting system with a conventional rubber damper by considering rubber form

    SciTech Connect

    Kodama, Tomoaki; Honda, Yasuhiro; Wakabayashi, Katsuhiko; Iwamoto, Shoichi

    1996-09-01

    The cheap and compact rubber dampers of shear-type have been widely employed as the torsional vibration control of the crankshaft system of high-speed, automobile diesel engines. The conventional rubber dampers have various rubber forms owing to the thorough investigation of optimum dampers in the design stage. Their rubber forms can be generally grouped into three classes such as the disk type, the bush type and the composite type. The disk type and the bush type rubber dampers are called the basic-pattern rubber dampers hereafter. The composite type rubber part is supposed to consist of the disk type and the bush type parts, regarded respectively as the basic patterns of the rubber part, at large. The dynamic characteristics of the vibration isolator rubber depend generally on temperature, frequency, strain amplitude, shape and size effect,s so it is difficult to estimate accurately their characteristics. With the present technical level, it is also difficult to determine the suitable rubber geometry which optimizes the vibration control effect. The study refers to the calculation method of the torsional vibration of a crankshaft system with a shear-type rubber damper having various rubber forms in order to offer the useful method for optimum design. In this method, the rheological formula of the three-element Maxwell model, from which the torsional stiffness and the damping coefficient of the damper rubber part in the equivalent vibration system are obtained, are adopted in order to decide the dynamic characteristics of the damper rubber part.

  1. Longitudinal variations of the solar activity influence on the annual and semiannual oscillations of the prevailing wind in the middle atmosphere

    NASA Astrophysics Data System (ADS)

    Guryanov, Vladimir

    The study is based on daily Northern and Southern Hemisphere UK Met Office data of zonal and meridional winds at 25 pressure levels for the period 1992-2013 (pressure range 1000-0.316 hPa). For each year of the period, (two solar cycles) set the amplitude of annual and semiannual oscillations of the zonal and meridional winds. The amplitude was used to determine correlations with Wolf numbers. Significant positive and negative correlations were found. Character correlations for zonal and meridional wind differ and depend on the period of oscillations, geographical location and altitude. Found steady negative correlation of solar activity with semiannual oscillations of zonal wind in the tropical zone both hemispheres in the upper stratosphere. For the meridional wind there are positive correlations in the extra-tropical latitudes in the lower and middle stratosphere, especially in the Southern Hemisphere.

  2. Optimum Parameters of Tuned Liquid Column Damper for Suppressing Pitching Vibration of AN Undamped Structure

    NASA Astrophysics Data System (ADS)

    XUE, S. D.; KO, J. M.; XU, Y. L.

    2000-08-01

    In order to evaluate the control performance of the tuned liquid column damper in suppressing pitching vibration of structures, an optimal parametric study of the damper is carried out for an undamped structure. The structure is assumed to be subjected to harmonic excitation in the analysis. The optimum tuning ratio (or the optimum liquid length) and the optimum head loss coefficient of the damper are determined using Den Hartog's method. Theanalytical formulas of the optimum TLCD parameters for the undamped structure are derived. The optimum peak amplitudes for the structure and the liquid are also obtained. Based on the developed analytical formulas, the practical solution procedures for finding the optimum parameters are proposed. The presented example indicates that the optimum TLCD parameters can be easily calculated from the developed formulas. With the help of this study, the understanding of TLCD behavior with respect to its optimum parameters is enhanced.

  3. Mathematical model of a novel small magnetorheological damper by using outer magnetic field

    NASA Astrophysics Data System (ADS)

    Huang, Liutian; Li, Junhui; Zhu, Wenhui

    2017-03-01

    In order to realize small loading and small damping, a mini Magneto-rheological fluid (MRF) damper is suggested by using new method of outer coils, and its physical model is established firstly. It was found that the landing force is only 1.74˜8N, the landing force is the third-order function with the current by polynomial fitting of the experimental data, which shows a force-current model. The results of force-displacement and force-velocity indicate that it has nonlinear hysteretic damping characteristics. Based on the new mini-mode principle and the damping characteristics, an improved nonlinear dynamics model is proposed, and its parameter expressions are obtained by parameter identification and regression fitting. Model curves fit well with experimental curves, and the improved model has fully demonstrated the dynamic characteristics of the mini-MRF damper. It will provide scientific method and physical model for the small MRF damper development.

  4. Dynamics of a spacecraft with large flexible appendage constrained by multi-strut passive damper

    NASA Astrophysics Data System (ADS)

    Jia, Ying-Hong; Xu, Shi-Jie; Hu, Quan

    2013-04-01

    This paper is concerned with the dynamics of a spacecraft with multi-strut passive damper for large flexible appendage. The damper platform is connected to the spacecraft by a spheric hinge, multiple damping struts and a rigid strut. The damping struts provide damping forces while the rigid strut produces a motion constraint of the multibody system. The exact nonlinear dynamical equations in reducedorder form are firstly derived by using Kane's equation in matrix form. Based on the assumptions of small velocity and small displacement, the nonlinear equations are reduced to a set of linear second-order differential equations in terms of independent generalized displacements with constant stiffness matrix and damping matrix related to the damping strut parameters. Numerical simulation results demonstrate the damping effectiveness of the damper for both the motion of the spacecraft and the vibration of the flexible appendage, and verify the accuracy of the linear equations against the exact nonlinear ones.

  5. Study of seismic response and vibration control of High voltage electrical equipment damper based on TMD

    NASA Astrophysics Data System (ADS)

    Liu, Chuncheng; Wang, Chongyang; Mao, Long; Zha, Chuanming

    2016-11-01

    Substation high voltage electrical equipment such as mutual inductor, circuit interrupter, disconnecting switch, etc., has played a key role in maintaining the normal operation of the power system. When the earthquake disaster, the electrical equipment of the porcelain in the transformer substation is the most easily to damage, causing great economic losses. In this paper, using the method of numerical analysis, the establishment of a typical high voltage electrical equipment of three dimensional finite element model, to study the seismic response of a typical SF6 circuit breaker, at the same time, analysis and contrast the installation ring tuned mass damper (TMD damper for short), by changing the damper damping coefficient and the mass block, install annular TMD vibration control effect is studied. The results of the study for guiding the seismic design of high voltage electrical equipment to provide valuable reference.

  6. Semiactive Control Using MR Dampers of a Frame Structure under Seismic Excitation

    NASA Astrophysics Data System (ADS)

    Gattulli, Vincenzo; Lepidi, Marco; Potenza, Francesco; Carneiro, Rùbia

    2008-07-01

    The paper approaches the multifaceted task of semiactively controlling the seismic response of a prototypal building model, through interstorey bracings embedding magnetorheological dampers. The control strategy is based on a synthetic discrete model, purposely formulated in a reduced space of significant dynamic variables, and consistently updated to match the modal properties identified from the experimental response of the modeled physical structure. The occurrence of a known eccentricity in the mass distribution, breaking the structural symmetry, is also considered. The dissipative action of two magnetorheological dampers is governed by a clipped-optimal control strategy. The dampers are positioned in order to deliver two eccentric and independent forces, acting on the first-storey displacements. This set-up allows the mitigation of the three-dimensional motion arising when monodirectional ground motion is imposed on the non-symmetric structure. Numerical investigations on the model response to natural accelerograms are presented. The effectiveness of the control strategy is discussed through synthetic performance indexes.

  7. Evaluation of seismic performance and effectiveness of multiple slim-type damper system for seismic response control of building structures.

    PubMed

    Kim, David; Sung, Eun Hee; Park, Kwan-Soon; Park, Jaegyun

    2014-01-01

    This paper presents the evaluation of seismic performance and cost-effectiveness of a multiple slim-type damper system developed for the vibration control of earthquake excited buildings. The multiple slim-type damper (MSD) that consists of several small slim-type dampers and linkage units can control damping capacity easily by changing the number of small dampers. To evaluate the performance of the MSD, dynamic loading tests are performed with three slim-type dampers manufactured at a real scale. Numerical simulations are also carried out by nonlinear time history analysis with a ten-story earthquake excited building structure. The seismic performance and cost-effectiveness of the MSD system are investigated according to the various installation configurations of the MSD system. From the results of numerical simulation and cost-effectiveness evaluation, it is shown that combinations of the MSD systems can effectively improve the seismic performance of earthquake excited building structures.

  8. Evaluation of Seismic Performance and Effectiveness of Multiple Slim-Type Damper System for Seismic Response Control of Building Structures

    PubMed Central

    Kim, David; Sung, Eun Hee; Park, Kwan-Soon; Park, Jaegyun

    2014-01-01

    This paper presents the evaluation of seismic performance and cost-effectiveness of a multiple slim-type damper system developed for the vibration control of earthquake excited buildings. The multiple slim-type damper (MSD) that consists of several small slim-type dampers and linkage units can control damping capacity easily by changing the number of small dampers. To evaluate the performance of the MSD, dynamic loading tests are performed with three slim-type dampers manufactured at a real scale. Numerical simulations are also carried out by nonlinear time history analysis with a ten-story earthquake excited building structure. The seismic performance and cost-effectiveness of the MSD system are investigated according to the various installation configurations of the MSD system. From the results of numerical simulation and cost-effectiveness evaluation, it is shown that combinations of the MSD systems can effectively improve the seismic performance of earthquake excited building structures. PMID:25301387

  9. Sensitivity of the Earth Magnetosphere to the Solar Wind Activity: 3D Macroparticle Model

    NASA Astrophysics Data System (ADS)

    Baraka, S. M.; Ben Jaffel, L.

    2006-05-01

    A new approach is proposed to study the sensitivity of the Earth Magnetosphere to the variability of the Solar Wind bulk velocity. A numerical particles in cell (PIC) method initially proposed by Buneman (1993) has been adopted and modified to carry out the study. Space was stretched as cubic boxes of dimension 155x105x105 Re filled with 2 million of Solar Wind particles, with Earth is located at 60x52x53 Re. The magnetic field of Earth was hypothetically set to zero, and then switched on. The formation of the magnetospheric cavity and its elongation around the planet was observed to evolve with time until a steady state topology of the system is attained with the classical structure of a magnetosphere. We also found that the cavity is repopulated by clouds of particles from the Solar Wind, producing the current sheet-- a thin plasma sheet that stands at the equatorial plane. The study was carried out with the very basic elements of the interaction processes as described by Maxwell and Lorentz equations. IMF was then included as a steady southward magnetic field. Drift velocity of the Solar Wind was changed to simulate compression/depression of the system. 3-D analysis of the response of the magnetosphere dayside to that variation was studied, and the corresponding relaxation time of the magnetopause interface was measured. In response to the Solar Wind drift velocity imposed drop-off, a ~ 15 Re gap in the incoming Solar Wind plasma appeared moving toward Earth. As soon as the gap hit the initial shock of the steady magnetosphere, a reconnection between the Earth magnetic field and IMF was noticed at the dayside magnetopause when IMF was included. Injection of nightside of the magnetosphere by energetic particles due to magnetic erosion and reconnection is observed. During the expansion phase of the disturbance, the outer boundary of the dayside magnetopause broke up during the absence of the IMF as it responded to the reduction of the ram pressure, whilst

  10. A NARX damper model for virtual tuning of automotive suspension systems with high-frequency loading

    NASA Astrophysics Data System (ADS)

    Alghafir, M. N.; Dunne, J. F.

    2012-02-01

    A computationally efficient NARX-type neural network model is developed to characterise highly nonlinear frequency-dependent thermally sensitive hydraulic dampers for use in the virtual tuning of passive suspension systems with high-frequency loading. Three input variables are chosen to account for high-frequency kinematics and temperature variations arising from continuous vehicle operation over non-smooth surfaces such as stone-covered streets, rough or off-road conditions. Two additional input variables are chosen to represent tuneable valve parameters. To assist in the development of the NARX model, a highly accurate but computationally excessive physical damper model [originally proposed by S. Duym and K. Reybrouck, Physical characterization of non-linear shock absorber dynamics, Eur. J. Mech. Eng. M 43(4) (1998), pp. 181-188] is extended to allow for high-frequency input kinematics. Experimental verification of this extended version uses measured damper data obtained from an industrial damper test machine under near-isothermal conditions for fixed valve settings, with input kinematics corresponding to harmonic and random road profiles. The extended model is then used only for simulating data for training and testing the NARX model with specified temperature profiles and different valve parameters, both in isolation and within quarter-car vehicle simulations. A heat generation and dissipation model is also developed and experimentally verified for use within the simulations. Virtual tuning using the quarter-car simulation model then exploits the NARX damper to achieve a compromise between ride and handling under transient thermal conditions with harmonic and random road profiles. For quarter-car simulations, the paper shows that a single tuneable NARX damper makes virtual tuning computationally very attractive.

  11. Deep Solar Activity Minimum 2007-2009: Solar Wind Properties and Major Effects on the Terrestrial Magnetosphere

    NASA Astrophysics Data System (ADS)

    Farrugia, C. J.; Harris, B.; Leitner, M.; Möstl, C.; Galvin, A. B.; Simunac, K. D. C.; Torbert, R. B.; Temmer, M. B.; Veronig, A. M.; Erkaev, N. V.; Szabo, A.; Ogilvie, K. W.; Luhmann, J. G.; Osherovich, V. A.

    2012-04-01

    We discuss the temporal variations and frequency distributions of solar wind and interplanetary magnetic field parameters during the solar minimum of 2007- 2009 from measurements returned by the IMPACT and PLASTIC instruments on STEREO-A. We find that the density and total field strength were considerably weaker than in the previous minimum. The Alfvén Mach number was higher than typical. This reflects the weakness of magnetohydrodynamic (MHD) forces, and has a direct effect on the solar wind-magnetosphere interactions. We then discuss two major aspects that this weak solar activity had on the magnetosphere using data from Wind and ground-based observations: (a) the level of solar wind driving and the associated dayside contribution to the crosspolar cap potential (CPCP), and (b) the shapes of the magnetopause and bow shock. For (a) we find very weak interplanetary electric field (V xBz = -0.05 ± 0.83 mV/m) and a CPCP of 36.6 ± 18.2 kV. The auroral activity is closely correlated to the prevalent stream-stream interactions.We argue that the Alfvén waves in the fast streams and Kelvin-Helmholtz instability were the predominant agents mediating the transfer of solar wind momentum and energy to the magnetosphere during this 3-year period. For (b) we determine 328 magnetopause and 271 bow shock crossings made by the Cluster 1, Themis B and C spacecraft during a 3-month interval when the daily averages of the magnetic and kinetic energy densities attained their lowest value during the 3 years under survey. We use the same numerical approach as in Fairfield's (1971) empirical model and compare our findings with his classic result. The stand-off distance of the subsolar magnetopause and bow shock were 11.8 RE and 14.35 RE, respectively, making the subsolar magnetosheath thinner by ≈ 1RE. This is mainly due to the low dynamic pressure which result in a sunward shift of the magnetopause The magnetopause is more flared than Fairfield's result. By contrast the bow shock

  12. Application of two design methods for active flutter suppression and wind-tunnel test results

    NASA Technical Reports Server (NTRS)

    Newsom, J. R.; Abel, I.; Dunn, H. J.

    1980-01-01

    The synthesis, implementation, and wind tunnel test of two flutter suppression control laws for an aeroelastic model equipped with a trailing edge control surface are presented. One control law is based on the aerodynamic energy method, and the other is based on results of optimal control theory. Analytical methods used to design the control laws and evaluate their performance are described. At Mach 0.6, 0.8, and 0.9, increases in flutter dynamic pressure were obtained but the full 44 percent increase was not achieved. However at Mach 0.95, the 44 percent increase was achieved with both control laws. Experimental results indicate that the performance of the systems is not so effective as that predicted by analysis, and that wind tunnel turbulence plays an important role in both control law synthesis and demonstration of system performance.

  13. Non-linear performance of a three-bearing rotor incorporating a squeeze-film damper

    NASA Technical Reports Server (NTRS)

    Holmes, R.; Dede, M.

    1987-01-01

    This paper is concerned with the non-linear vibration performance of a rigid rotor supported on three bearings, one being surrounded by a squeeze-film damper. This damper relies on the pressure built up in the squeeze film to help counter-act external forces arising from unbalance and other effects. As a result a vibration orbit of a certain magnetude results. Such vibration orbits illustrate features found in other non-linear systems, in particular sub-harmonic resonances and jump phenomena. Comparisons between theoretical prediction and experimental observations of these phenomena are made.

  14. An Unsteady Long Bearing Squeeze Film Damper Model. Part 1; Circular Centered Orbits

    NASA Technical Reports Server (NTRS)

    Schallhorn, P. A.; Elrod, D. A.; Goggin, D. G.; Majumdar, A. K.

    2000-01-01

    This paper, the first of a two-part series, presents results of an unsteady rotordynamic analysis of a long-bearing squeeze film damper executing circular centered orbits using a fluid circuit approach. A series of nodes and branches represent the geometry of the flow circuit. The mass and momentum conservation equations are solved to predict the pressure distribution in the squeeze film. The motion of the bearing is simulated by the variation of geometry within the flow path. The modeling methodology is benchmarked against published experimental long-bearing squeeze film damper test results. The model provides good agreement with the experimental damping coefficient.

  15. Experimentally determined stiffness and damping of an inherently compensated air squeeze-film damper

    NASA Technical Reports Server (NTRS)

    Cunningham, R. E.

    1975-01-01

    Values of damping and stiffness were determined experimentally for an externally pressurized, inherently compensated, compressible squeeze-film damper up to excitation frequencies of 36,000 cycles per minute. Experimental damping values were higher than theory predicted at low squeeze numbers and less than predicted at high squeeze numbers. Experimental values of air film stiffness were less than theory predicted at low squeeze numbers and much greater at higher squeeze numbers. Results also indicate sufficient damping to attenuate amplitudes and forces at the critical speed when using three dampers in the flexible support system of a small, lightweight turborotor.

  16. Design of a squeeze-film damper for a multi-mass flexible rotor

    NASA Technical Reports Server (NTRS)

    Cunningham, R. E.; Fleming, D. P.; Gunter, E. J.

    1975-01-01

    A single mass flexible rotor analysis was used to optimize the stiffness and damping of a flexible support for a symmetric five-mass rotor. The flexible support attenuates the rotor motions and forces transmitted to the support bearings when the rotor operates through and above its first bending critical speed. An oil squeeze-film damper was designed based on short bearing lubrication theory. The damper design was verified by an unbalance response computer program. Rotor amplitudes were reduced by a factor of 16 and loads reduced by a factor of 36 compared with the same rotor on rigid bearing supports.

  17. Design of an oil squeeze film damper bearing for a multimass flexible-rotor bearing system

    NASA Technical Reports Server (NTRS)

    Cunningham, R. E.; Gunter, E. J., Jr.; Fleming, D. P.

    1975-01-01

    A single-mass flexible-rotor analysis was used to optimize the stiffness and damping of a flexible support for a symmetric five-mass rotor. The flexible, damped support attenuates the amplitudes of motions and forces transmitted to the support bearings when the rotor operates through and above its first bending critical speed. An oil squeeze film damper was designed based on short bearing lubrication theory. The damper design was verified by an unbalance response computer program. Rotor amplitudes were reduced by a factor of 16 and loads reduced by a factor of 36 compared with the same rotor with rigid bearing supports.

  18. Tidal wind as a possible link of coupling between atmospheric waves activity and sporadic E formation

    NASA Astrophysics Data System (ADS)

    Dalakishvili, Giorgi; Didebulidze, Goderdzi G.; Matiashvili, Giorgi

    2016-04-01

    The horizontal tidal wind in the mesosphere lower thermosphere region (MLT) is considered as a source of atmospheric gravity waves (AGWs) and vortical type perturbations generation. It is shown that at mid-latitude these atmospheric waves, evolving in the tidal wind, can lead to vertical convergence of heavy metallic ions of this region and Formation of sporadic E (Es) layer. The process of sporadic E formation by short-period AGWs (close to Bunt-Vaisala period) and by the stationary type vortical perturbations with the same spatial scale, excited in the horizontal shear flow is demonstrated using numerical simulations. The possibility of oscillation of Es layers electron/ions density by period less than BV period under influence of short-period AGWs is shown and the possible coupling of these processes with quasi-periodic echoes is also noted. In our numerical experiment the mid-latitude nighttime Es layers formed under influence of these atmospheric waves, which are possibly generated by horizontal tidal wind, mostly move downward, this is an observed phenomena. It is noted that investigation of sporadic E formation by atmospheric waves evolving in the tidal wind is important for study of the in situ developing processes in the lower thermosphere determining atmosphere-ionosphere dynamical coupling as well as for revealing their possible dynamical coupling with lower atmosphere. Acknowledgements: This work has been supported by Shota Rustaveli National Science Foundation grant No 31/81 and the Shota Rustaveli National Science Foundation grant No FR/51/6-300/14.

  19. OVATION Prime -2013: Solar Wind Driven Precipitation Model Extended to Higher Geomagnetic Activity Levels (Invited)

    NASA Astrophysics Data System (ADS)

    Newell, P. T.; Liou, K.; Zhang, Y.; Paxton, L.; Sotirelis, T.; Mitchell, E. J.

    2013-12-01

    OVATION Prime is an auroral precipitation model parameterized by solar wind driving. Distinguishing features of the model include an optimized solar wind-magnetosphere coupling function (dΦMP/dt) which predicts auroral power far better than Kp or other traditional parameters, the separation of aurora into categories (diffuse aurora, monoenergetic, broadband, and ion), the inclusion of seasonal variations, and separate parameter fits for each MLATxMLT bin, thus permitting each type of aurora and each location to have differing responses to season and solar wind input (as indeed they do). We here introduce OVATION Prime-2013, an upgrade to the 2008 version currently widely available. The most notable advantage of OP-2013 is that it uses UV images from the GUVI instrument on the satellite TIMED for high disturbance levels (dΦMP/dt > 12,000 (nT2/3 (km/s)4/3 which roughly corresponds to Kp = 5+ or 6-). The range of validity is thought to be about 0 < dΦMP/dt = 30000 (say Kp = 8 or 8+). Other upgrades include a reduced susceptibility to salt and pepper noise, and smoother interpolation across the postmidnight data gap. We will also provide a comparison of the advantages and disadvantages of other current precipitation models, especially OVATION-SuperMAG, which produces particularly good estimates for total auroral power, at the expense of working best on an historical basis. OVATION Prime-2013, for high solar wind driving, as TIMED GUVI data takes over from DMSP

  20. Numerical Investigation of Active Flow Control on Wind Turbines under Yaw Misalignment

    NASA Astrophysics Data System (ADS)

    Tran, Steven; Corson, David; Sahni, Onkar

    2012-11-01

    Yaw misalignment dramatically increases unsteady aerodynamic loading on wind turbine blades over each revolution. The resulting fluctuating loads on each blade cause fatigue in the system and subsequently, failure leading to increased maintenance costs and unnecessary downtime. In this study we numerically analyze the effects of yaw misalignment on complete rotating wind turbines with blades of O(5m) in length. We consider two wind speeds at rated and above-rated regimes, where the effect of yaw misalignment is more pronounced. For the baseline configuration comparisons are made with the existing experimental data. To mitigate the resulting unsteady aerodynamic loading, we apply synthetic-jet based fluidic actuation in order to achieve fast-time response (in contrast to traditional yaw control strategies). O(5-10) jets are placed along the outer half of blade span. Along the chord two jet locations (x/c = 0.05 and 0.40) are considered. Actuation strategies for jets are based on partial loop control with pulse modulation. All simulations are based on unsteady Reynolds-averaged Navier-Stokes (URANS) equations. NYSERDA.

  1. Design, implementation, simulation, and testing of digital flutter suppression systems for the active flexible wing wind-tunnel model

    NASA Technical Reports Server (NTRS)

    Perry, Boyd, III; Mukhopadhyay, Vivek; Hoadley, Sherwood Tiffany; Cole, Stanley R.; Buttrill, Carey S.; Houck, Jacob A.

    1990-01-01

    Active flutter suppression control laws were designed, implemented, and tested on an aeroelastically-scaled wind-tunnel model in the NASA Langley Transonic Dynamics Tunnel. One of the control laws was successful in stabilizing the model while the dynamic pressure was increased to 24 percent greater than the measured open-loop flutter boundary. Other accomplishments included the design, implementation, and successful operation of a one-of-a-kind digital controller, the design and use of two simulation methods to support the projet, and the development and successful use of a methodology for online controller performance evaluation.

  2. Topside ionosphere bubbles, seen as He+ density depletions: connection with ESF, vertical plasma drift, thermosphere wind and solar activity

    NASA Astrophysics Data System (ADS)

    Sidorova, Larissa

    He+ density depletions, considered as originating from equatorial plasma bubbles (PB), or as possible fossil bubble signatures, were involved in this study. He+ density depletions were observed during a high solar activity (1978-79, F10.7 200) at the topside ionosphere altitudes deeply inside the plasmasphere (L 1.3-3) (Karpachev and Sidorova, ASR, 2002; Sidorova, ASR, 2004, 2007). It is suggested that the equatorial F region irregularities, their post sunset development, evolution, and decay processes are controlled by the sunset electrodynamics of the equatorial region. The He+ density depletion peculiarities were considered in connection with equatorial F-spread (ESF) and vertical plasma drift. The depletion values as function of local time (evening-night hours) were compared with the vertical plasma drift velocity variations, obtained for the same periods (1978-79, F10.7 200; AE-E, IS radar, Jicamarca). Striking similarity in development dynamics was revealed for the different seasons. The monthly mean PB occurrence probability, plotted in local time versus month, was compared with the similar plots for global ESF occurrence probability, derived from ISS-b data (1978-79). Good seasonal correlation (R=0.6) was obtained. Moreover, the comparison of the regional maps, derived from ground-based ionograms, obtained over Brazilian regions (Abdu et al., ASR, 2000) for period with the similar solar activity (1980-81, F10.7 230), shows very well correlation (R=0.67). It is also suggested, that the PBs, produced by Rayleigh-Taylor (R-T) instability at the bottomside of ionosphere and transported up to the topside ionosphere/plasmasphere, could be strong affected by meridional wind during a generation due to inhibiting the growth of R-T instability and flux tube integrated conductivity. For better understanding competing/complementary roles of thermospheric winds in the development of PBs, seen as He+ density depletions, the evaluation of the possible influence of the

  3. A new algorithm quantifies the roles of wind and midge flight activity in the bluetongue epizootic in northwest Europe.

    PubMed

    Sedda, Luigi; Brown, Heidi E; Purse, Bethan V; Burgin, Laura; Gloster, John; Rogers, David J

    2012-06-22

    The 2006 bluetongue (BT) outbreak in northwestern Europe had devastating effects on cattle and sheep in that intensively farmed area. The role of wind in disease spread, through its effect on Culicoides dispersal, is still uncertain, and remains unquantified. We examine here the relationship between farm-level infection dates and wind speed and direction within the framework of a novel model involving both mechanistic and stochastic steps. We consider wind as both a carrier of host semio-chemicals, to which midges might respond by upwind flight, and as a transporter of the midges themselves, in a more or less downwind direction. For completeness, we also consider midge movement independent of wind and various combinations of upwind, downwind and random movements. Using stochastic simulation, we are able to explain infection onset at 94 per cent of the 2025 affected farms. We conclude that 54 per cent of outbreaks occurred through (presumably midge) movement of infections over distances of no more than 5 km, 92 per cent over distances of no more than 31 km and only 2 per cent over any greater distances. The modal value for all infections combined is less than 1 km. Our analysis suggests that previous claims for a higher frequency of long-distance infections are unfounded. We suggest that many apparent long-distance infections resulted from sequences of shorter-range infections; a 'stepping stone' effect. Our analysis also found that downwind movement (the only sort so far considered in explanations of BT epidemics) is responsible for only 39 per cent of all infections, and highlights the effective contribution to disease spread of upwind midge movement, which accounted for 38 per cent of all infections. The importance of midge flight speed is also investigated. Within the same model framework, lower midge active flight speed (of 0.13 rather than 0.5 m s(-1)) reduced virtually to zero the role of upwind movement, mainly because modelled wind speeds in the area

  4. Wind Simulation

    SciTech Connect

    Walker, Howard Andrew

    2008-12-31

    The Software consists of a spreadsheet written in Microsoft Excel that provides an hourly simulation of a wind energy system, which includes a calculation of wind turbine output as a power-curve fit of wind speed.

  5. Wind turbine/generator set having a stator cooling system located between stator frame and active coils

    DOEpatents

    Bevington, Christopher M.; Bywaters, Garrett L.; Coleman, Clint C.; Costin, Daniel P.; Danforth, William L.; Lynch, Jonathan A.; Rolland, Robert H.

    2012-11-13

    A wind turbine comprising an electrical generator that includes a rotor assembly. A wind rotor that includes a wind rotor hub is directly coupled to the rotor assembly via a simplified connection. The wind rotor and generator rotor assembly are rotatably mounted on a central spindle via a bearing assembly. The wind rotor hub includes an opening having a diameter larger than the outside diameter of the central spindle adjacent the bearing assembly so as to allow access to the bearing assembly from a cavity inside the wind rotor hub. The spindle is attached to a turret supported by a tower. Each of the spindle, turret and tower has an interior cavity that permits personnel to traverse therethrough to the cavity of the wind rotor hub. The wind turbine further includes a frictional braking system for slowing, stopping or keeping stopped the rotation of the wind rotor and rotor assembly.

  6. Broad emission lines in the duelling wind model of active galaxies

    NASA Astrophysics Data System (ADS)

    Mobasher, B.; Raine, D. J.

    1989-04-01

    The broad-line emission from clouds formed by the interaction of a nuclear mass outflow and a disk wind is investigated in the context of a quasar model. The line ratios and profiles are shown to be in general agreement with observations. Particular results include: (1) a density range compatible with suggested solutions to the Ly-alpha/H-beta problem which nevertheless yields the correct C III 1909-A flux; (2) broader lines from the inner higher density region despite an accelerated outflow; (3) compatibility between broad-line-region sizes from variability arguments and ionization parameters; and (4) blueshifted line-peaks apparently uncorrelated with line asymmetry.

  7. Langley Research Center's Unitary Plan Wind Tunnel: Testing Capabilities and Recent Modernization Activities

    NASA Technical Reports Server (NTRS)

    Micol, John R.

    2001-01-01

    Description, capabilities, initiatives, and utilization of the NASA Langley Research Center's Unitary Plan Wind Tunnel are presented. A brief overview of the facility's operational capabilities and testing techniques is provided. A recent Construction of Facilities (Car) project to improve facility productivity and efficiency through facility automation has been completed and is discussed. Several new and maturing thrusts are underway that include systematic efforts to provide credible assessment for data quality, modifications to the new automation control system for increased compatibility with the Modern Design of Experiments (MDOE) testing methodology, and process improvements for better test coordination, planning, and execution.

  8. Langley Research Center's Unitary Plan Wind Tunnel: Testing Capabilities and Recent Modernization Activities

    NASA Technical Reports Server (NTRS)

    Micol, John R.

    2001-01-01

    Description, capabilities, initiatives, and utilization of the NASA Langley Research Center's Unitary Plan Wind Tunnel are presented. A brief overview of the facility's operational capabilities and testing techniques is provided. A recent Construction of Facilities (CoF) project to improve facility productivity and efficiency through facility automation has been completed and is discussed. Several new and maturing thrusts are underway that include systematic efforts to provide credible assessment for data quality, modifications to the new automation control system for increased compatibility with the Modern Design Of Experiments (MDOE) testing methodology, and process improvements for better test coordination, planning, and execution.

  9. A new energy-harvesting device system for wireless sensors, adaptable to on-site monitoring of MR damper motion

    NASA Astrophysics Data System (ADS)

    Yu, Miao; Peng, Youxiang; Wang, Siqi; Fu, Jie; Choi, S. B.

    2014-07-01

    Under extreme service conditions in vehicle suspension systems, some defects exist in the hardening, bodying, and poor temperature stability of magnetorheological (MR) fluid. These defects can cause weak and even invalid performance in the MR fluid damper (MR damper for short). To ensure the effective validity of the practical applicability of the MR damper, one must implement an online state-monitoring sensor to monitor several performance factors, such as acceleration. In this empirical work, we propose a new energy-harvesting device system for the wireless sensor system of an MR damper. The monitoring sensor system consists of several components, such as an energy-harvesting device, energy-management circuit, and wireless sensor node. The electrical energy harvested from the kinetic energy of the MR fluid that flows within the MR damper can be automatically charged and discharged with the help of an energy-management circuit for the wireless sensor node. After verifying good performance from each component, an experimental apparatus is built to evaluate the feasibility of the proposed self-powered wireless sensor system. The measured results of pressure, temperature, and acceleration data within the MR damper clearly demonstrate the practical applicability of monitoring the operating work states of the MR damper when it is subjected to sinusoidal excitation.

  10. The influence of wind and locomotor activity on surface temperature and energy expenditure of the Eastern house finch (Carpodacus mexicanus) during cold stress.

    PubMed

    Zerba, E; Dana, A N; Lucia, M A

    1999-01-01

    We investigated the extent to which exercise-generated heat compensates for regulatory thermogenesis of Eastern house finches (Carpodacus mexicanus Müller) exposed to ambient temperatures (Ta) and convective conditions typical of that which birds experience in nature while perched in the open or foraging on the ground. We addressed the hypothesis that resting and active birds exposed to similar net convective conditions will exhibit similar surface temperatures (Ts) and metabolic energy expenditures. To test this hypothesis, resting birds were exposed to a wind speed equivalent to the treadmill speed (0.5 m s-1) for a hopping bird (active). Ts of resting birds in no wind, resting birds exposed to wind, and active birds were measured with infrared thermography at Ta between 0 degrees and 25 degrees C. Metabolic heat production was estimated from measures of respiratory gases at Ta between -5 degrees and 25 degrees C. For resting birds in no wind, resting birds in wind, and active birds, Ts decreased with decreasing Ta. The effects of variation in Ta on Ts depended on activity level (F=3.91, df=2,40, P=0.0280). The regression relationship of Ts on Ta, however, did not differ significantly between resting birds exposed to wind and active birds (F=0.12, df=2,40, P=0.8865), whereas the slope was lower and intercept higher for resting birds in no wind compared with those of resting birds exposed to wind and active birds combined (F=20.96, df=2,42, P<0.0001). Metabolic heat production for resting birds exposed to wind and active birds increased with decreasing Ta. Average metabolic heat production of resting (46.01 mW g-1+/-10.60 SD) and active birds (47.63 mW g-1+/-8.76 SD) exposed to similar net convective conditions did not differ significantly (F=3.87, df=1,44, P=0.0556). These results support our hypothesis and provide evidence that exercise generated compensates for thermostatic requirements at Ta just below thermoneutrality, which resembles conditions under which

  11. Response of the PC index to the solar wind influence and it's availability for nowcasting of storm and substorm activity

    NASA Astrophysics Data System (ADS)

    Troshichev, O. A.

    2003-04-01

    The PC index has been put forward with a general aim to find a key parameter that (1) would estimate the current state of the global magnetospheric activity, and (2) would be readily calculated from routine ground-based measurements. The PC index has been derived as the dimensionless quantity parameterized by season, UT, and hemisphere, and calculated for interplanetary electric field coupling with the magnetosphere (Em). Response of the PC index to the solar wind influence is examined using the data on solar wind parameters observed by ACE spacecraft in the point of libration L1. It is shown that the PC index in range PC=0-12 is proportional to value of the interplanetary electric field Em and, correspondingly, to the polar cap voltage and the polar cap ionospheric electric field Ei. If the magnetic activity within the polar cap is extremely high (PC>12), the interplanetary and ionospheric electric fields tend to approach an asymptotic (effect of electric field saturation). In these conditions, apart from the interplanetary electric field Em determining the regular level of the antisunward convection in the polar cap, the PC index is affected either by (1) unusual enhancement of the ionospheric conductivity in the polar cap in association with bombardment of the ionosphere by solar protons (E=1-10 MeV) in time of strong polar cap absorption events, or by (2) the solar wind pressure pulses those strongly enhance the antisunward convection (positive PC) under Bz<0, and sunward convection (negative PC) under Bz>0. It means that the PC index adequately estimates the solar wind energy coming into the high-latitude magnetosphere and, therefore, can be used to evaluate the current state of the magnetosphere. It is shown that sharp increase of the PC index indicates conclusively that the auroral substorm will be developed in a matter of minutes. Correlation between the PC index and AE indices turned out to be much higher in absence of Dst variation (R=0.74) than in course

  12. Deep Solar Activity Minimum 2007-2009: Solar Wind Properties and Major Effects on the Terrestrial Magnetosphere

    NASA Technical Reports Server (NTRS)

    Farrugia, C. J.; Harris, B.; Leitner, M.; Moestl, C.; Galvin, A. B.; Simunac, K. D. C.; Torbert, R. B.; Temmer, M. B.; Veronig, A. M.; Erkaev, N. V.; Szabo, A.; Ogilvie, K. W.; Luhman, J. G.; Osherovich, V. A.

    2012-01-01

    We discuss the temporal variations and frequency distributions of solar wind and interplanetary magnetic field parameters during the solar minimum of 2007 - 2009 from measurements returned by the IMPACT and PLASTIC instruments on STEREO-A.We find that the density and total field strength were significantly weaker than in the previous minimum. The Alfven Mach number was higher than typical. This reflects the weakness of magnetohydrodynamic (MHD) forces, and has a direct effect on the solar wind-magnetosphere interactions.We then discuss two major aspects that this weak solar activity had on the magnetosphere, using data from Wind and ground-based observations: i) the dayside contribution to the cross-polar cap potential (CPCP), and ii) the shapes of the magnetopause and bow shock. For i) we find a low interplanetary electric field of 1.3+/-0.9 mV/m and a CPCP of 37.3+/-20.2 kV. The auroral activity is closely correlated to the prevalent stream-stream interactions. We suggest that the Alfven wave trains in the fast streams and Kelvin-Helmholtz instability were the predominant agents mediating the transfer of solar wind momentum and energy to the magnetosphere during this three-year period. For ii) we determine 328 magnetopause and 271 bow shock crossings made by Geotail, Cluster 1, and the THEMIS B and C spacecraft during a three-month interval when the daily averages of the magnetic and kinetic energy densities attained their lowest value during the three years under survey.We use the same numerical approach as in Fairfield's empirical model and compare our findings with three magnetopause models. The stand-off distance of the subsolar magnetopause and bow shock were 11.8 R(sub E) and 14.35 R(sub E), respectively. When comparing with Fairfield's classic result, we find that the subsolar magnetosheath is thinner by approx. 1 R(sub E). This is mainly due to the low dynamic pressure which results in a sunward shift of the magnetopause. The magnetopause is more flared

  13. Deep Solar Activity Minimum 2007-2009: Solar Wind Properties and Major Effects on the Terrestrial Magnetosphere

    NASA Astrophysics Data System (ADS)

    Farrugia, C. J.; Harris, B. S.; Leitner, M.; Moestl, C.; Galvin, A. B.; Simunac, K.; Torbert, R. B.; Temmer, M.; Veronig, A.; Erkaev, N.; Szabo, A.; Ogilvie, K. W.; Luhmann, J. G.; Osherovich, V.

    2012-12-01

    We discuss the temporal variations and frequency distributions of solar wind and IMF parameters during the solar minimum of 2007-2009 from measurements returned by the IMPACT and PLASTIC instruments on STEREO-A. We find that the density and total field strength were significantly weaker than in the previous minimum. The Alfvén Mach number was higher than typical.This reflects the weakness of magnetohydrodynamic (MHD) forces, and has a direct effect on the solar wind-magnetosphere interactions. We then discuss two major aspects that this weak solar activity had on the magnetosphere, using data from textit{Wind} and ground-based observations: (a) the dayside contribution to the cross-polar cap potential (CPCP), and (b) the shapes of the magnetopause and bow shock. For (a) we find a low interplanetary electric field of 1.3 ± 0.9 mV m-1 and a CPCP of 37.3 ± 20.2 kV. The auroral activity is closely correlated to the prevalent stream-stream interactions. We suggest that the Alfvén wave trains in the fast streams and Kelvin-Helmholtz instability were the predominant agents mediating the transfer of solar wind momentum and energy to the magnetosphere during this three-year period. For (b) we determine 328 magnetopause and 271 bow shock crossings made by textit{Geotail, Cluster 1}, and the THEMIS B and C spacecraft during a three-month interval when the daily averages of the magnetic and kinetic energy densities attained their lowest value during the three years under survey. We use the same numerical approach as in Fairfield's (textit{J. Geophys. Res.} 76, 7600, 1971) empirical model and compare our findings with three magnetopause models. The stand-off distance of the subsolar magnetopause and bow shock were 11.8 RE and 14.35 RE, respectively. When comparing with Fairfield's (1971) classic result, we find that the subsolar magnetosheath is thinner by ˜1 RE. This is mainly due to the low dynamic pressure which results in a sunward shift of the magnetopause The

  14. Transverse digital damper system for the Fermilab anti-proton recycler

    SciTech Connect

    Eddy, N.; Crisp, J.; /Fermilab

    2006-05-01

    A transverse damping system is used in the Recycler at Fermilab to damp beam instabilities which arise from large beam intensities with electron cooling. Initial tests of electron cooling demonstrated beam loss due to transverse beam motion when the beam was cooled past the beam density threshold. The transverse damper system consists of two horizontal and two vertical pickups whose signals are amplified and passed into an analog hybrid to generate a difference signal from each pickup. The difference signals are input to a custom digital damper board which digitizes the analog signals at 212mhz, performs digital processing of the signals inside a large Altera Stratix II FPGA, then provides analog output at 212mhz via digital to analog converters. The digital damper output is sent to amplifiers which drive one horizontal and one vertical kicker. An initial prototype digital damper board has been successfully used in the Recycler for over six months. Currently, work is underway to replace the prototype board with an upgraded VME version.

  15. Prototyping design and experimental validation of membranous dual-cavity based amplitude selective damper

    NASA Astrophysics Data System (ADS)

    Zhang, Yuxin; Guo, Konghui; Li, Shengbo Eben; Shao, Xiong; Zheng, Meiyu

    2016-08-01

    This paper designs a membranous dual-cavity based amplitude sensitive damper (shorted as MASD) for road vehicle suspension to better compromise ride comfort and driving safety. A specially designed sleeve, separated into two cavities by a rubber membrane, is centrally placed along the main piston of conventional twin-tube damper. The volume change of dual-cavity caused by membrane deformation accommodates partial oil flow in the condition of small piston displacement, which results in a reduced damping ratio. Due to the attached rubber embossments on both sides of rubber membrane, this MASD can switch smoothly between low and high damping forces at the final stage of membrane deformation. This design prevents the damper from additional impact when switching between higher damping ratio to lower one. After elaborating the working principle of MASD, its dynamic model is derived by combining first-principle modeling of hydraulic components and empirical modeling of membranous valve. A prototyping MASD is finally developed and tested on a damper test rig to demonstrate its effectiveness.

  16. Numerical investigation of effectiveness of two seismic dampers on a benchmark structure

    NASA Astrophysics Data System (ADS)

    Qu, J. T.; Yang, W. L.

    2011-07-01

    The passive energy dissipation devices have been widely applied in seismic control of new constructions and reinforcement of seismic damage structures. The technique of passive energy dissipation has been written into the China Seismic Code for Buildings, which can give an impulse to the use and development of this technique. With the international common performance evaluation platform of structural vibration control - the third stage of benchmark, using three models and some performance evaluation indices of nonlinear vibration control, the control results of buildings with displacement-based and velocity-based dampers were compared. Combining the passive control of structures with the modern control theory, using MATLAB/SIMULINK to establish simulation models of the structures with displacement-based and velocity-based dampers, the responses of three benchmark structure models were calculated under far- and near-field earthquakes. Control effect is compared for different types of dampers on different structures through different evaluation indices, which can provide a certain criterion of reference for the application and design of the passive energy dissipation dampers.

  17. Smart damper using the combination of magnetic friction and pre-compressed rubber springs

    NASA Astrophysics Data System (ADS)

    Choi, Eunsoo; Choi, Gyuchan; Kim, Hong-Taek; Youn, Heejung

    2015-09-01

    This paper proposes a new concept of a smart damper using the combination of magnetic friction and rubber springs. The magnet provides energy dissipation, and the rubber springs with precompression contribute to increasing the recentering capacity of the damper. To verify their performance, dynamic tests of magnet frictional dampers and precompressed rubber springs were conducted. For this purpose, hexahedron neodymium (NdFeB) magnets and polyurethane rubber cylinders were used. In the dynamic tests, the loading frequency was varied from 0.1 to 2.0 Hz. The magnets showed almost perfect rectangular behavior in the force-deformation curve, and the frictional coefficient of the magnets was estimated through averaging and regression. The rubber springs were tested with and without precompression. The rubber springs showed different loading path from the second cycle and residual deformation that was not recovered immediately. The rubber springs showed greater rigid force with increasing precompression. Finally, this paper discusses the combination of rigid-elastic behavior and friction to generate 'flag-shaped' behavior for a smart damper and suggests how to combine magnets and rubber springs to obtain flag-shaped behavior. The performance of the magnets and precompressed rubber springs was verified through analytical models.

  18. A passive pendulum wobble damper for a low spin rate Jupiter flyby spacecraft

    NASA Technical Reports Server (NTRS)

    Fowler, R. C.

    1972-01-01

    When the spacecraft has a low spin rate and precise pointing requirements, the wobble angle must be damped in a time period equivalent to a very few wobble cycles. The design, analysis, and test of a passive pendulum wobble damper are described.

  19. New waveguide-type HOM damper for ALS storage ring cavities.

    SciTech Connect

    Kwiatkowski, Slawomir; Baptiste, Kenneth; Julian, James

    2004-06-28

    The ALS storage ring 500 MHz RF system uses two re-entrant accelerating cavities powered by a single 320kW PHILLIPS YK1305 klystron. During several years of initial operation, the RF cavities were not equipped with effective passive HOM damper systems. Longitudinal beam stability was achieved through cavity temperature control and the longitudinal feedback system (LFB), which was often operating at the edge of its capabilities. As a result, longitudinal beam stability was a significant operations issue at the ALS. During two consecutive shutdown periods (April 2002 and 2003) we installed E-type HOM dampers on the main and third harmonic cavities. These devices dramatically decreased the Q-values of the longitudinal anti-symmetric HOM modes. The next step is to damp the rest of the longitudinal HOM modes in the main cavities below the synchrotron radiation damping level. This will hopefully eliminate the need for the LFB and set the stage for a possible increase in beam current. The ''waveguide'' type of HOM damper was the only option that didn't significantly compromise the vacuum performance of the RF cavity. The design process and the results of the low level measurements of the new waveguide dampers are presented in this paper.

  20. Investigation of oscillations of the elastic bodies with joined a mass-spring-damper systems

    NASA Astrophysics Data System (ADS)

    Sultanov, L. U.

    2016-11-01

    The problem of free oscillations of elastic systems joined with a simple mechanical system consisting of mass, springs and dampers is considered. The differential equation is obtained. The solution of the received equation is based on series. The oscillation of rectangular plate is considered.

  1. Use of piezoelectric dampers for improving the feel of golf clubs

    NASA Astrophysics Data System (ADS)

    Bianchini, Emanuele; Spangler, Ronald L., Jr.; Pandell, Tracy

    1999-06-01

    Several sports are based upon a tool (club, bat, stick) striking an object (ball, puck) across a field of play. Anytime two structures collide, vibration is created by the impact of the two. The impact of the objects excites the structural modes of the tool, creating a vibration that can be felt by the player, especially if the hit is not at a `sweet spot'. Vibration adversely affects both feel and performance. This paper explains how piezoelectric dampers were developed to reduce vibration and improve the feel of ball-impact sporting goods such as golf clubs. The paper describes how the dynamic characteristics of a golf club were calculated, at first in the free-free condition, and then during its operation conditions (the swing of the club, and the impact with the ball). The dynamic characteristics were used to develop a damper that addressed a specific, or multiple, modes of interest. The damper development and testing are detailed in this paper. Both objective laboratory tests and subjective player tests were performed to evaluate the effectiveness of the piezoelectric dampers. The results of the tests, along with published medical data on the sensitivity of the human body, were used to draw a correlation between human feel and vibration reduction.

  2. Hysteretic Performance Identification for a Frame Structure with MR Damper under Limited Excitations

    NASA Astrophysics Data System (ADS)

    Xu, Bin; Zhou, Ren; He, Jia; Masri, Sami F.

    2010-05-01

    Nonlinearity exists widely in engineering structures and may arise in damaged structures, but the identification theory for nonlinear dynamic systems is far less established than that for linear systems. Most of the currently available vibration-based identification approaches for structural damage detection are based on eigenvalues and mode shapes extraction which are suitable for linear systems. For the purpose of early warning and damage prognosis, it is crucial to develop efficient and reliable identification methods for nonlinear hysteretic performance because the restoring force is the direct indicator of damage initiation and development. In this paper, a general time series data-based approach was employed to identify the nonlinear behavior of a multi-degree-of-freedom frame structure equipped with a MR damper only using the excitation force applied on limited locations and the corresponding structural response measurement. The performance of the proposed methodology was validated for a 4-story frame model structure with and without a MR damper. The system matrices of the linear frame model structure were identified firstly with a least-squares techniques and the equivalent system of the frame structure with MR damper were identified. Then the location and the hysteretic performance of the MR damper were identified and compared with the test measurements. Results show that the proposed data-based approach is efficient for nonlinear behavior identification of engineering structures.

  3. Optimal design of a tuned liquid damper using a magnetic fluid with one electromagnet.

    PubMed

    Ohno, K; Shimoda, M; Sawada, T

    2008-05-21

    Characteristics of a tuned magnetic fluid damper are examined. The optimal depth of a magnetic fluid in a cylindrical container is calculated using a linear analysis of a magnetic fluid sloshing. In order to avoid swirling in lower depth fluids, several experiments using greater fluid depths are carried out and a good damping range is obtained.

  4. Life Cycle Testing of Viscoelastic Material for Hubble Space Telescope Solar Array 3 Damper

    NASA Technical Reports Server (NTRS)

    Maly, Joseph R.; Reed, Benjamin B.; Viens, Michael J.; Parker, Bradford H.; Pendleton, Scott C.

    2003-01-01

    During the March 2002 Servicing Mission by Space Shuttle (STS 109), the Hubble Space Telescope (HST) was refurbished with two new solar arrays that now provide all of its power. These arrays were built with viscoelastic/titanium dampers, integral to the supporting masts, which reduce the interaction of the wing bending modes with the Telescope. Damping of over 3% of critical was achieved. To assess the damper s ability to maintain nominal performance over the 10-year on-orbit design goal, material specimens were subjected to an accelerated life test. The test matrix consisted of scheduled events to expose the specimens to pre-determined combinations of temperatures, frequencies, displacement levels, and numbers of cycles. These exposure events were designed to replicate the life environment of the damper from fabrication through testing to launch and life on-orbit. To determine whether material degradation occurred during the exposure sequence, material performance was evaluated before and after the accelerated aging with complex stiffness measurements. Based on comparison of pre- and post-life-cycle measurements, the material is expected to maintain nominal performance through end of life on-orbit. Recent telemetry from the Telescope indicates that the dampers are performing nominally.

  5. Wind Program Newsletter: October 2014 Edition (Newsletter)

    SciTech Connect

    Not Available

    2014-10-01

    The U.S. Department of Energy's Wind Program Newsletter, supported by the EERE Wind and Water Power Technologies office, highlights the Wind Program's key activities, events, and funding opportunities.

  6. Events draw attention of operators to activity in the Wind River Basin

    SciTech Connect

    Leach, W.H. Jr.

    1995-07-01

    New sour-gas capacity, 3-D seismic and a play-opening discovery have drawn the attention of Rocky Mountain operators to the Wind River Basin. In mid-1994, Tom Brown Inc. (TBI), Midland, announced an option agreement had been finalized with the Shoshone and Arapahoe Indian tribes covering some 400,000 acres within the Wind River Indian Reservation in Fremont County, Wyoming. The gross acreage covered by the agreement consists of four separate 100,000-acre packages in townships 1s to 5n and ranges 1w to 2w and le to 6e, with Boysen Reservoir as the eastern boundary. Terms of the TBI option call for TBI to acquire 40 square miles of 3-D seismic data on the acreage over a two-year period. TBI then has five years, from signing date, to drill four wells. To date, 25 square miles of 3-D seismic data have been gathered and are being processed and interpreted. All seismic work on these blocks should be completed this year, and the company expects to drill at least one well before year`s end. A fifth 100,000-acre option has been negotiated between TBI and the Indian tribes along the same lines as the previous four, and agreements have been signed. A 3-D seismic program will start soon.

  7. Correlated studies at activity maximum: The Sun and the solar wind

    NASA Technical Reports Server (NTRS)

    Hudson, H. S.; Galvin, A. B.

    1997-01-01

    The breadth and power of the set of solar and heliospheric observatories presently in space is unprecedented. Their observations generally began at solar minimum or in the declining phase of the past maximum, but it is anticipated that most of the instruments will be able to observe the rise to the next maximum and that the events will happen then. The second orbit of Ulysses will be especially interesting and the Yokhoh orbital decay is not projected until 2002. New spacecraft, including TRACE, HESSI, and SOLAR-B, may also become available. The current remote sensing and in situ measurements are characterized by a much stronger understanding of how the solar and interplanetary phenomena match. The novel discoveries from the current data are reviewed, and speculations are expressed on how to take advantage of the future data, emphasizing the use of heliospheric observations to help probe the connectivity of the corona/solar wind interface region. It is suggested that there now exists a possibility of understanding the heliospheric structure empirically in new ways: by using particles as tracers of the field, and by correlating multi-point measurements of structures in the solar wind with solar images.

  8. Nonlinear Whirl Response of a High-Speed Seal Test Rotor With Marginal and Extended Squeeze-Film Dampers

    NASA Technical Reports Server (NTRS)

    Proctor, Margaret P.; Gunter, Edgar J.

    2005-01-01

    Synchronous and nonsynchronous whirl response analysis of a double overhung, high-speed seal test rotor with ball bearings supported in 5.84- and 12.7-mm-long, un-centered squeeze-film oil dampers is presented. Test performance with the original damper of length 5.84 mm was marginal, with nonsynchronous whirling at the overhung seal test disk and high amplitude synchronous response above 32,000 rpm near the drive spline section occurring. A system critical speed analysis of the drive system and the high-speed seal test rotor indicated that the first two critical speeds are associated with the seal test rotor. Nonlinear synchronous unbalance and time transient whirl studies were conducted on the seal test rotor with the original and extended damper lengths. With the original damper design, the nonlinear synchronous response showed that unbalance could cause damper lockup at 33,000 rpm. Alford cross-coupling forces were also included at the overhung seal test disk for the whirl analysis. Sub-synchronous whirling at the seal test disk was observed in the nonlinear time transient analysis. With the extended damper length of 12.7 mm, the sub-synchronous motion was eliminated and the rotor unbalance response was acceptable to 45,000 rpm with moderate rotor unbalance. However, with high rotor unbalance, damper lockup could still occur at 33,000 rpm, even with the extended squeeze-film dampers. Therefore, the test rotor must be reasonably balanced in order for the un-centered dampers to be effective.

  9. The spectral analysis of an aero-engine assembly incorporating a squeeze-film damper

    NASA Technical Reports Server (NTRS)

    Holmes, R.; Dede, M. M.

    1989-01-01

    Aero-engine structures have very low inherent damping and so artificial damping is often introduced by pumping oil into annular gaps between the casings and the outer races of some or all of the rolling-element bearings supporting the rotors. The thin oil films so formed are called squeeze film dampers and they can be beneficial in reducing rotor vibration due to unbalance and keeping to reasonable limits the forces transmitted to the engine casing. However, squeeze-film dampers are notoriously non-linear and as a result can introduce into the assembly such phenomena as subharmonic oscillations, jumps and combination frequencies. The purpose of the research is to investigate such phenomena both theoretically and experimentally on a test facility reproducing the essential features of a medium-size aero engine. The forerunner of this work was published. It was concerned with the examination of a squeeze-film damper in series with housing flexibility when supporting a rotor. The structure represented to a limited extent the essentials of the projected Rolls Royce RB401 engine. That research demonstrated the ability to calculate the oil-film forces arising from the squeeze film from known motions of the bearing components and showed that the dynamics of a shaft fitted with a squeeze film bearing can be predicted reasonably accurately. An aero-engine will normally have at least two shafts and so in addition to the excitation forces which are synchronous with the rotation of one shaft, there will also be forces at other frequencies from other shafts operating on the squeeze-film damper. Theoretical and experimental work to consider severe loading of squeeze-film dampers and to include these additional effects are examined.

  10. Technology Learning Activities. Design Brief--Measuring Inaccessible Distances. Alternative Energy Sources: Designing a Wind Powered Generator. Alternative Energy Sources: Designing a Hot Dog Heater Using Solar Energy.

    ERIC Educational Resources Information Center

    Technology Teacher, 1991

    1991-01-01

    These three learning activities are on measuring accessible distances, designing a wind powered generator, and designing a hot dog heater using solar energy. Each activity includes description of context, objectives, list of materials and equipment, challenge to students, and evaluation questions. (SK)

  11. Active Control of Wind-Tunnel Model Aeroelastic Response Using Neural Networks

    NASA Technical Reports Server (NTRS)

    Scott, Robert C.

    2000-01-01

    NASA Langley Research Center, Hampton, VA 23681 Under a joint research and development effort conducted by the National Aeronautics and Space Administration and The Boeing Company (formerly McDonnell Douglas) three neural-network based control systems were developed and tested. The control systems were experimentally evaluated using a transonic wind-tunnel model in the Langley Transonic Dynamics Tunnel. One system used a neural network to schedule flutter suppression control laws, another employed a neural network in a predictive control scheme, and the third employed a neural network in an inverse model control scheme. All three of these control schemes successfully suppressed flutter to or near the limits of the testing apparatus, and represent the first experimental applications of neural networks to flutter suppression. This paper will summarize the findings of this project.

  12. Erosion: Wind

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wind erosion refers to the detachment, transport and deposition of sediment by wind. It is a dynamic, physical process where loose, dry, bare soils are transported by strong winds. Wind erosion is a soil degrading process that affects over 500 million ha of land worldwide and creates between 500 an...

  13. Meteorology (Wind)

    Atmospheric Science Data Center

    2014-09-25

    Wind speed at 50 m (m/s) The average and percent difference minimum and ... are given.   Percent of time for ranges of wind speed at 50 m (percent) Percentage [frequency] of time that wind ... be adjusted to heights from 10 to 300 meters using the Gipe power law. Wind speeds may be adjusted for different terrain by selecting from ...

  14. Improved clipped periodic optimal control for semi-active harmonic disturbance rejection

    NASA Astrophysics Data System (ADS)

    Couillard, Maxime; Micheau, Philippe; Masson, Patrice

    2008-12-01

    This paper presents a new approach for harmonic disturbance rejection using semi-active vibration control. The approach is illustrated through application to the problem of maximizing the energy dissipated by a semi-active damper under harmonic excitation. In order to establish a baseline for the evaluation of the performance of the semi-active damper, the effectiveness of the optimal passive and active cases are first presented. The study then examines the ability of the clipped optimal control (or clipping control) approach to improve the energy dissipation capacity of the semi-active damper over the optimal passive damper. An approximate solution to the nonlinear dynamic problem, obtained using the method of averaging, and a time integration based numerical method indicate that this approach improves the energy dissipated by the semi-active damper over the optimal passive damper. The approach presented in this paper intends to further "improve", or "fine tune", the control parameters given by the clipped optimal control approach. This is done using an approximated solution of the problem and an appropriate optimization algorithm. Results clearly indicate that this new approach provides significant improvement on energy dissipation over the clipped optimal control approach for the semi-active damper.

  15. Written on the Wind.

    ERIC Educational Resources Information Center

    Adams, Steve

    1990-01-01

    The study of aerodynamics using a wind tunnel helps students develop an understanding of the basic scientific concepts of lift, drag, and stability and their applications. Directions for building a wind tunnel in the classroom and activities for using the tunnel are provided. (KR)

  16. Using the transverse digital damper as a real-time tune monitor for the Booster synchrotron at Fermilab

    SciTech Connect

    Eddy, N.; Lysenko, O.; /FERMILAB

    2011-08-01

    The Fermilab Booster is a fast ramping (15Hz) synchrotron which accelerates protons from 400MeV to 8GeV. During commissioning of a transverse digital damper system, it was shown that the damper could provide a measurement of the machine tune throughout the cycle by exciting just 1 of the 84 bunches with minimal impact on the machine operation. The algorithms used to make the measurement have been incorporated into the damper FPGA firmware allowing for real-time tune monitoring of all Booster cycles. A new Booster tune monitor was implemented in the digital damper which has minimal impact on the Booster operation. The tune measures the tunes in two planes over the energy ramping cycle with an accuracy of 0.01 in real time.

  17. On the uniqueness of linear moving-average filters for the solar wind-auroral geomagnetic activity coupling

    NASA Technical Reports Server (NTRS)

    Vassiliadis, D.; Klimas, A. J.

    1995-01-01

    The relation between the solar wind input to the magetosphere, VB(sub South), and the auroral geomagnetic index AL is modeled with two linear moving-average filtering methods: linear prediction filters and a driven harmonic oscillator in the form of an electric circuit. Although the response of the three-parameter oscillator is simpler than the filter's, the methods yield similar linear timescales and values of the prediction-observation correlation and the prediction Chi(exp 2). Further the filter responses obtained by the two methods are similar in their long-term features. In these aspects the circuit model is equivalent to linear prediction filtering. This poses the question of uniqueness and proper interpretation of detailed features of the filters such as response peaks. Finally, the variation of timescales and filter responses with the AL activity level is discussed.

  18. Bibliography of Literature for Avian Issues in Solar and Wind Energy and Other Activities

    SciTech Connect

    Walston, Leroy J.; White, Ellen M.; Meyers, Stephanie A.; Turchi, Craig; Sinclair, Karin

    2015-04-01

    Utility-scale solar energy has been a rapidly expanding energy sector in the United States in recent years and is expected to continue to grow. In 2014, concerns were raised over the risk of avian fatalities associated with utility-scale solar plants. With funding from the U.S. Department of Energy SunShot Program, Argonne National Laboratory and the National Renewable Energy Laboratory studied the issue and released A Review of Avian Monitoring and Mitigation Information at Existing Utility-Scale Solar Facilities (ANL/EVS-15/2, March 2015). A comprehensive literature review included peer-reviewed journal articles on avian fatalities from solar energy facilities and other sources (e.g., wind energy, building collisions, etc.), project-specific technical reports on avian monitoring and fatality at solar facilities, information on mitigation measures and best management practices, and literature pertaining to avian behavioral patterns and habitat use. The source citations are listed in this bibliography; they are current through December 2014.

  19. The Disk Wind Model of the Broad Line Regions in Active Galactic Nuclei and Cataclysmic Variables

    NASA Technical Reports Server (NTRS)

    Begelman, Mitchell

    2002-01-01

    This is the final progress report for our Astrophysics Theory Program (NRA 97-OSS12) grant NAG5-7723. We have made considerable progress on incorporating photoionization calculations with a 2.5D hydrodynamical code to model disk winds in AGNs. Following up on our simultaneous broad band monitoring campaign of the type I Seyfert galaxy NGC 5548, we have investigated the constraints imposed on models of accretion in Seyfert galaxies by their optical, UV, and X-ray spectral energy distributions (SEDs). Using results from thermal Comptonization models that relate the physical properties of the hot inner accretion flow to the thermal reprocessing that occurs in the surrounding colder thin disk, we find that we can constrain the central black hole mass, accretion rate and size scale of the hot central flow. We have applied our model to observations of Seyfert galaxies NGC 3516, NGC 7469 and NGC 5548. Our mass and accretion rate estimates for these objects roughly agree with those found using other methods.

  20. Optimization of Higher Order Mode Dampers in the 56MHz SRF Cavity for RHIC

    SciTech Connect

    Wu, Q.; Ben-Zvi, I.

    2010-05-23

    A 56 MHz superconducting RF cavity was designed for a luminosity upgrade of the Relativistic Heavy Ion Collider (RHIC), including requirements for Higher Order Mode (HOM) damping. In this paper, we describe our optimization of the damper's performance, and modifications made to its original design. We also show the effects of the damper geometry on the cavity's HOM impedance. To reduce the likelihood of magnetic breakdown, we lowered the magnetic field enhancement at the ports to a value less than the highest field in the cavity. We simulated all monopole and dipole HOMs up to 1GHz with their frequencies, mode configurations, R/Qs, and shunt impedances, verifying that all modes are well-damped with the optimized design and configuration. The 56 MHz superconducting RF cavity is a quarterwave resonator designed to have a gap voltage of 2.5 MV. Our plans are to place this beam-driven resonator at a common section of RHIC to provide a storage RF potential for both rings. The large bucket of the cavity will reduce spill due to Intra-Beam Scattering (IBS), and thus increase the luminosity for the detectors. It is very important to damp all the cavity's Higher Order Modes (HOMs) to avoid beam instabilities. The design chosen for the HOM damper is a magnetically coupled loop located at the rear end of the cavity. The loop and its port geometry must be optimized to assure sufficient damping, avoid a large enhancement of the local magnetic field. A high-pass filter is included in the circuit to reduce the power extraction from the fundamental mode. The number of HOM dampers used and their configuration also are important factors for the damping and cooling system. A small loop area will couple out less power from the cavity's fundamental mode, thus reducing the voltage and power dissipation in the damper's filter circuit; however, it might not be sufficient for HOM damping. This problem is resolved by increasing the number of the HOM dampers and carefully choosing their

  1. The effect of solar activity on the evolution of solar wind parameters during the rise of the 24th cycle

    NASA Astrophysics Data System (ADS)

    Rod'kin, D. G.; Shugay, Yu. S.; Slemzin, V. A.; Veselovskii, I. S.

    2016-01-01

    The dynamics of parameters of the near-Earth solar wind (SW) and the effect of solar activity on the parameters of three SW components (fast SW from large-scale coronal holes (CHs); slow SW from active regions, streamers, and other sources; and transient flows related to sporadic solar activity) at the beginning of the 24th solar cycle (2009-2011) are analyzed. It is demonstrated that temperaturedependent parameters of ionic composition (C+6/C+5 and O+7/O+6) of the transient SW component in the profound minimum of solar activity in 2009 were correlated with the variation of the rate of weak (type C and weaker) flares. This verifies the presence of a hot component associated with these flares in the SW. The variations in the velocity and the kinetic temperature of fast SW from CHs with an increase in activity are more pronounced in the bulk of the high-speed stream, and the variations of O+7/O+6 and Fe/O ratios and the magnitude of the interplanetary magnetic field are the most prominent in the region of interaction between fast and slow SW streams. The analysis reveals that a value of O+7/O+6 = 0.1 serves as the criterion to distinguish between fast SW streams and interplanetary coronal mass ejections in the 2009 activity minimum. This value is lower than the one (0.145) determined earlier based on the data on the 23rd cycle (Zhao et al., 2009). Therefore, the distinguishing criterion is not an absolute one and depends on the solar activity level.

  2. Dynamics of a passive micro-vibration isolator based on a pretensioned plane cable net structure and fluid damper

    NASA Astrophysics Data System (ADS)

    Chen, Yanhao; Lu, Qi; Jing, Bo; Zhang, Zhiyi

    2016-09-01

    This paper addresses dynamic modelling and experiments on a passive vibration isolator for application in the space environment. The isolator is composed of a pretensioned plane cable net structure and a fluid damper in parallel. Firstly, the frequency response function (FRF) of a single cable is analysed according to the string theory, and the FRF synthesis method is adopted to establish a dynamic model of the plane cable net structure. Secondly, the equivalent damping coefficient of the fluid damper is analysed. Thirdly, experiments are carried out to compare the plane cable net structure, the fluid damper and the vibration isolator formed by the net and the damper, respectively. It is shown that the plane cable net structure can achieve substantial vibration attenuation but has a great amplification at its resonance frequency due to the light damping of cables. The damping effect of fluid damper is acceptable without taking the poor carrying capacity into consideration. Compared to the plane cable net structure and the fluid damper, the isolator has an acceptable resonance amplification as well as vibration attenuation.

  3. Modelling the effect of rail dampers on wheel-rail interaction forces and rail roughness growth rates

    NASA Astrophysics Data System (ADS)

    Croft, B. E.; Jones, C. J. C.; Thompson, D. J.

    2009-06-01

    Trains generate rolling noise because of the roughness of the wheel and rail running surfaces. Special acoustic grinding programmes have been introduced on some railways specifically to control rolling noise. Rail dampers are also used to reduce rolling noise; this paper studies rail damping as a possible mechanism to slow the rate of development of roughness on the surface of rails. This would reduce noise further over time or reduce the required frequency of grinding. High roughness growth on the rail occurs in situations with stiff vertical structural dynamics of the track. In particular the antiresonance above a sleeper at the pinned-pinned frequency has been identified as a wavelength fixing mechanism for short pitch corrugation. Rail dampers change the dynamic response of the rail, shifting the pinned-pinned frequency and smoothing the track receptance. Here, a simple time-stepping model is applied to calculate the interaction forces between wheel and rail for a track with and without rail dampers. The calculations show that rail dampers reduce dynamic interaction forces and shift the force spectrum to longer wavelengths. The interaction forces are used as input to an abrasive wear model to predict the roughness growth rate and the change in roughness after many wheel passages. Track without rail dampers is predicted to develop corrugation at the wavelength corresponding to the pinned-pinned frequency. With rail dampers the corrugation growth is reduced and shifted to a longer wavelength where its significance is diminished.

  4. Comparison of the effect of two damper sizes on the performance of a low-solidity axial-flow transonic compressor rotor

    NASA Technical Reports Server (NTRS)

    Lewis, G. W., Jr.; Urasek, D. C.

    1972-01-01

    The experimental performance of a 20-inch-diameter axial-flow transonic compressor rotor with small dampers is presented. The compressor rotor was tested earlier with large dampers which were twice in size, and comparisons of overall performance and radial distributions of selected flow and performance parameters are made. The rotor with small dampers experienced lower losses in the damper region which resulted in locally higher values of temperature rise efficiency and total pressure ratio. However, there was no appreciable effect on overall efficiency and pressure ratio. A greater stall margin was measured for the rotor with small dampers at design speed, but at 70 and 90 percent of design speed the rotor with large dampers had somewhat greater flow range.

  5. Winter Activity of Coastal Plain Populations of Bat Species Affected by White-Nose Syndrome and Wind Energy Facilities.

    PubMed

    Grider, John F; Larsen, Angela L; Homyack, Jessica A; Kalcounis-Rueppell, Matina C

    2016-01-01

    Across the entire distribution of a species, populations may have variable responses to environmental perturbations. Many bat species experience mortality in large portions of their range during hibernation and along migratory paths to and from wintering grounds, from White-nose syndrome (WNS) and wind energy development, respectively. In some areas, warm temperatures may allow bats to remain active through winter, thus decreasing their susceptibility to WNS and/or mortality associated with migration to wintering grounds. These areas could act as a refugia and be important for the persistence of local populations. To determine if warmer temperatures affect bat activity, we compared year-round activity of bat populations in the Coastal Plain and Piedmont of North Carolina, USA, two regions that differ in winter temperature. We established six recording stations, four along a 295-kilometer north-south transect in the Coastal Plain, and two in the Piedmont of North Carolina. We recorded bat activity over two years. We supplemented our recordings with mist-net data. Although bat activity was lower during winter at all sites, the odds of recording a bat during winter were higher at Coastal Plain sites when compared with Piedmont sites. Further, bats in the Piedmont had a lower level of winter activity compared to summer activity than bats in the Coastal Plain that had more similar levels of activity in the winter and summer. We found high bat species richness on the Coastal Plain in winter, with winter-active species including those known to hibernate throughout most of their range and others known to be long distance migrants. In particular, two species impacted by WNS, the northern long-eared bat (Myotis septentrionalis) and tricolored bat (Perimyotis subflavus), were present year round in the Coastal Plain. The tricolored bat was also present year-round in the Piedmont. In the Coastal Plain, the long distance migratory hoary bat (Lasiurus cinereus) was active in the

  6. Winter Activity of Coastal Plain Populations of Bat Species Affected by White-Nose Syndrome and Wind Energy Facilities

    PubMed Central

    Larsen, Angela L.; Homyack, Jessica A.; Kalcounis-Rueppell, Matina C.

    2016-01-01

    Across the entire distribution of a species, populations may have variable responses to environmental perturbations. Many bat species experience mortality in large portions of their range during hibernation and along migratory paths to and from wintering grounds, from White-nose syndrome (WNS) and wind energy development, respectively. In some areas, warm temperatures may allow bats to remain active through winter, thus decreasing their susceptibility to WNS and/or mortality associated with migration to wintering grounds. These areas could act as a refugia and be important for the persistence of local populations. To determine if warmer temperatures affect bat activity, we compared year-round activity of bat populations in the Coastal Plain and Piedmont of North Carolina, USA, two regions that differ in winter temperature. We established six recording stations, four along a 295-kilometer north-south transect in the Coastal Plain, and two in the Piedmont of North Carolina. We recorded bat activity over two years. We supplemented our recordings with mist-net data. Although bat activity was lower during winter at all sites, the odds of recording a bat during winter were higher at Coastal Plain sites when compared with Piedmont sites. Further, bats in the Piedmont had a lower level of winter activity compared to summer activity than bats in the Coastal Plain that had more similar levels of activity in the winter and summer. We found high bat species richness on the Coastal Plain in winter, with winter-active species including those known to hibernate throughout most of their range and others known to be long distance migrants. In particular, two species impacted by WNS, the northern long-eared bat (Myotis septentrionalis) and tricolored bat (Perimyotis subflavus), were present year round in the Coastal Plain. The tricolored bat was also present year-round in the Piedmont. In the Coastal Plain, the long distance migratory hoary bat (Lasiurus cinereus) was active in the

  7. Development and demonstration of a flutter-suppression system using active controls. [wind tunnel tests

    NASA Technical Reports Server (NTRS)

    Sandford, M. C.; Abel, I.; Gray, D. L.

    1975-01-01

    The application of active control technology to suppress flutter was demonstrated successfully in the transonic dynamics tunnel with a delta-wing model. The model was a simplified version of a proposed supersonic transport wing design. An active flutter suppression method based on an aerodynamic energy criterion was verified by using three different control laws. The first two control laws utilized both leading-edge and trailing-edge active control surfaces, whereas the third control law required only a single trailing-edge active control surface. At a Mach number of 0.9 the experimental results demonstrated increases in the flutter dynamic pressure from 12.5 percent to 30 percent with active controls. Analytical methods were developed to predict both open-loop and closed-loop stability, and the results agreed reasonably well with the experimental results.

  8. SSME seal test program: Test results for hole-pattern damper seals

    NASA Technical Reports Server (NTRS)

    Childs, D. W.

    1985-01-01

    The results consisting of direct and transverse force coefficients are presented for thirteen, hole-pattern, damper-seal configurations. The designation damper seal refers to a seal which uses a deliberately roughened stator nd smooth rotor, to increase the net damping force developed by a seal. The designation hole-pattern refers to a stator roughness pattern which is developed by a pattern of round holes while are milled into the stator. All seals tested use the same smooth rotor and have the same constant minimum clearance. The seal tests examined the following major design options: (1) hole-area density, i.e., the proportion of stator surface area consumed by holes; and (2) hole depth, particularly the ratio of hole depth to minimum clearance. In addition, limited data were taken to examine the influence of in-line versus staggered hole patterns and flat-bottomed versus spherical-bottomed holes.

  9. Damping Estimation from Free Decay Responses of Cables with MR Dampers

    PubMed Central

    Weber, Felix; Distl, Hans

    2015-01-01

    This paper discusses the damping measurements on cables with real-time controlled MR dampers that were performed on a laboratory scale single strand cable and on cables of the Sutong Bridge, China. The control approach aims at producing amplitude and frequency independent cable damping which is confirmed by the tests. The experimentally obtained cable damping in comparison to the theoretical value due to optimal linear viscous damping reveals that support conditions of the cable anchors, force tracking errors in the actual MR damper force, energy spillover to higher modes, and excitation and sensor cables hanging on the stay cable must be taken into consideration for the interpretation of the identified cable damping values. PMID:26167537

  10. Theoretical prediction of the damping of a railway wheel with sandwich-type dampers

    NASA Astrophysics Data System (ADS)

    Merideno, Inaki; Nieto, Javier; Gil-Negrete, Nere; Giménez Ortiz, José Germán; Landaberea, Aitor; Iartza, Jon

    2014-09-01

    This paper presents a procedure for predicting the damping added to a railway wheel when sandwich-type dampers are installed. Although there are different ways to reduce the noise generated by a railway wheel, most devices are based on the mechanism of increasing wheel damping. This is why modal damping ratios are a clear indicator of the efficiency of the damping device and essential when a vibro-acoustic study of a railway wheel is carried out. Based on a number of output variables extracted from the wheel and damper models, the strategy explained herein provides the final damping ratios of the damped wheel. Several different configurations are designed and experimentally tested. Theoretical and experimental results agree adequately, and it is demonstrated that this procedure is a good tool for qualitative comparison between different solutions in the design stages.

  11. Development of an Estimation Method for Damper Design in Static Elastography

    NASA Astrophysics Data System (ADS)

    Sato, Takayuki; Sato, Shizuka; Watanabe, Yasuaki; Goka, Shigeyoshi; Sekimoto, Hitoshi

    2010-07-01

    The estimation of elasticity distribution in static elastography methods strongly depends on the shape of the transducer head. It is known that the insertion of a damper layer is effective in improving the spatial nonuniformity of an applied strain distribution. We have developed a new estimation method for assessing the effectiveness of this technique through structural analysis using the finite element method and acoustic analysis using the finite-difference time-domain method with multilayered tissues. From the results, the strain flatness inside the compressed tissue is markedly improved, especially near the tissue surface, by inserting a damper layer between the transducer and the tissue surface. The elasticity of an inclusion and the deeper region of a three-layer tissue are also adequately imaged.

  12. Optimization of Magneto-Rheological Damper for Maximizing Magnetic Flux Density in the Fluid Flow Gap Through FEA and GA Approaches

    NASA Astrophysics Data System (ADS)

    Krishna, Hemanth; Kumar, Hemantha; Gangadharan, Kalluvalappil

    2016-06-01

    A magneto rheological (MR) fluid damper offers cost effective solution for semiactive vibration control in an automobile suspension. The performance of MR damper is significantly depends on the electromagnetic circuit incorporated into it. The force developed by MR fluid damper is highly influenced by the magnetic flux density induced in the fluid flow gap. In the present work, optimization of electromagnetic circuit of an MR damper is discussed in order to maximize the magnetic flux density. The optimization procedure was proposed by genetic algorithm and design of experiments techniques. The result shows that the fluid flow gap size less than 1.12 mm cause significant increase of magnetic flux density.

  13. Direct-Drive Motor System with Particle-Type ER Fluid Damper

    NASA Astrophysics Data System (ADS)

    Koyanagi, Ken'ichi; Furusho, Junji

    In most of robotic systems in industrial applications, vibratory problems occur at high-speed motion, because of elasticity of drive systems like reduction gear units and mechanical structures. Also friction and backlash in the drive systems cause serious problems. On the other hand, since direct-drive (DD) motor systems do not use reduction gears, those are effective for high-speed and high-precision control. In DD motor systems, however, low damping ratio, or large time delays of computers and amplifiers causes another type of problem at precise positioning phase. In this study, a particle type ER fluid damper was introduced to a DD motor system to compensate damping ratio mechanically. Because controlling viscosity of ER damper according to status of motion did not disturb advantage of the DD system that can move fast, the performance of the DD system was improved. The effectiveness of the proposed system was confirmed experimentally. The method of our study can contribute to expansion of usability of ER fluid dampers on industrial applications not limited to DD systems.

  14. Modeling and experimental investigation of a novel arc-surfaced frictional damper

    NASA Astrophysics Data System (ADS)

    Wang, Gongxian; Wang, Yangyang; Yuan, Jianming; Yang, Yi; Wang, Dong

    2017-02-01

    In this investigation, an innovative type of frictional damper called Arc-surfaced Frictional Damper (AFD) is introduced. The damping force of such damper is secured by pre-compression of Polyurethane Elastomer (PUE). The major advantage of AFD is that its frictional surfaces are curved so that the damping force varies with displacement. The mathematical model for AFD is established to predict its hysteretic behavior and analyze its mechanism. Then the hysteretic behavior of AFD was studied by experimental means. Experiment program included tests with various pre-compressions at quasi-static loading and dynamic loading with various frequencies was conducted. The results show a saddle-shaped behavior in the force-displacement relation. Furthermore, it is verified that AFD does have the hysteretic property of variable frictional force and the proposed mathematical model can be used to predict the hysteretic behavior of AFD. Hysteretic characteristics of AFD such as slip load, energy dissipation capacity, the effective stiffness and damping per cycle of loading are calculated.

  15. Shake table tests and analytical simulations of a steel structure with shape memory alloy dampers

    NASA Astrophysics Data System (ADS)

    Parulekar, Y. M.; Kiran, A. Ravi; Reddy, G. R.; Singh, R. K.; Vaze, K. K.

    2014-12-01

    This study uses the pseudoelastic properties of Ni-Ti shape memory alloy wires for attenuation of the seismic response of a steel structure and evaluates its effectiveness and applicability in seismic response control. In this paper, shake table tests, carried out on a model of a steel structure with and without wire-based shape memory alloy dampers, are discussed in detail. Shake table tests, comprised of free vibration tests and spectrum compatible time history tests, were carried out. The former were used for the evaluation of the frequency and damping, and the later were used to prove the efficacy of the shape memory alloy dampers. Further analytical simulations are carried out using detailed time history analysis utilizing a thermomechanical model of an SMA and taking into account the residual martensite accumulation, which is irreversibly due to cyclic forward/reverse martensitic transformation. Moreover, a simple iterative response spectrum (IRS) method with equivalent damping and stiffness is also used to evaluate the response of the structure with SMA dampers, and it is proved that the method can be conservatively used by designers.

  16. A novel self-powered MR damper: theoretical and experimental analysis

    NASA Astrophysics Data System (ADS)

    Xinchun, Guan; Yonghu, Huang; Yi, Ru; Hui, Li; Jinping, Ou

    2015-10-01

    This paper presents a novel magnetorheological (MR) damper with a self-powered capability, which is proposed to have energy harvesting and MR damping technologies integrated into a single device. Vibration energy harvesting mechanisms were adopted, based on ball-screw mechanisms and a rotary permanent magnet dc generator, to convert the external vibration energy into electrical energy to power the MR damping unit. The configuration and operating principles of the proposed self-powered MR damper were presented. Considering the core loss effect on the magnetic field, a theoretical analysis of the proposed MR damper was carried out and a mechanical model was developed. Finally, a prototype with a capacity of 10 kN was fabricated and experimentally investigated in both the direct-supply mode and the supply-with-rectifier mode. The results indicated that the proposed configuration is feasible and that both modes can realize good self-adaptability of the MR damping force. However, the direct-supply mode has a sag effect in the force-displacement curve and provides a lower energy-dissipating capacity than the direct-supply mode does under the same conditions.

  17. Partial Surface Damper to Suppress Vibration for Thin Walled Plate Milling

    NASA Astrophysics Data System (ADS)

    SHI, Jiahao; SONG, Qinghua; LIU, Zhanqiang; AI, Xing

    2017-03-01

    The material removal rate and required workpiece surface quality of thin-walled structure milling are greatly limited due to its severe vibration, which is directly associated with the dynamic characteristics of the system. Therefore, the suppression of vibration is an unavoidable problem during milling. A novel partial surface damping method is proposed to modify the mode of the thin walled cantilever plate and to suppress vibration during milling. Based on classical plate theory, the design criterion is analyzed and configuration of the partial surface damper is introduced, in which viscoelastic plate and constraining plate are attached to the surface of the plate to increase the system's natural frequency and loss factor. In order to obtain the energy expression of the cutting system, the Ritz method is used to describe the unknown displacements. Then, with Lagrange's equation, the natural frequency and loss factor are calculated. In addition, the plate is divided into a finite number of square elements, and the regulation of treated position is studied based on theoretic and experimental analysis. The milling tests are conducted to verify its damping performance and the experimental results show that with treatment of partial surface damper, the deformation of the bare plate is reduced from 0.27 mm to 0.1 mm, while the vibration amplitude of the bare plate is reduced from 0.08 mm to 0.01 mm. The proposed research provides the instruction to design partial surface damper.

  18. Wind Streaks

    NASA Technical Reports Server (NTRS)

    2004-01-01

    [figure removed for brevity, see original site]

    Released 12 July 2004 The atmosphere of Mars is a dynamic system. Water-ice clouds, fog, and hazes can make imaging the surface from space difficult. Dust storms can grow from local disturbances to global sizes, through which imaging is impossible. Seasonal temperature changes are the usual drivers in cloud and dust storm development and growth.

    Eons of atmospheric dust storm activity has left its mark on the surface of Mars. Dust carried aloft by the wind has settled out on every available surface; sand dunes have been created and moved by centuries of wind; and the effect of continual sand-blasting has modified many regions of Mars, creating yardangs and other unusual surface forms.

    Windstreaks are features caused by the interaction of wind and topographic landforms. The raised rims and bowls of impact craters causes a complex interaction such that the wind vortex in the lee of the crater can both scour away the surface dust and deposit it back in the center of the lee. If you look closely, you will see evidence of this in a darker 'rim' enclosing a brighter interior.

    Image information: VIS instrument. Latitude 6.9, Longitude 69.4 East (290.6 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon

  19. 78 FR 7402 - Small Takes of Marine Mammals Incidental to Specified Activities; Cape Wind's High Resolution...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-01

    ... boating activity in Nantucket Sound (MMS, 2009). NMFS expects that acoustic stimuli resulting from the... recorded with two Autonomous Multichannel Acoustic Recorders, deployed 100 m apart, in the vicinity of the... of the scale means that each 10-dB increase is a 10-fold increase in acoustic power (and a...

  20. Illinois Wind Workers Group

    SciTech Connect

    David G. Loomis

    2012-05-28

    The Illinois Wind Working Group (IWWG) was founded in 2006 with about 15 members. It has grown to over 200 members today representing all aspects of the wind industry across the State of Illinois. In 2008, the IWWG developed a strategic plan to give direction to the group and its activities. The strategic plan identifies ways to address critical market barriers to the further penetration of wind. The key to addressing these market barriers is public education and outreach. Since Illinois has a restructured electricity market, utilities no longer have a strong control over the addition of new capacity within the state. Instead, market acceptance depends on willing landowners to lease land and willing county officials to site wind farms. Many times these groups are uninformed about the benefits of wind energy and unfamiliar with the process. Therefore, many of the project objectives focus on conferences, forum, databases and research that will allow these stakeholders to make well-educated decisions.