Coupled Pitch Links for Multi-Harmonic Isolation Using Fluidic Circuits

2012 ◽  
Author(s):  
Lloyd H. Scarborough ◽  
Christopher D. Rahn ◽  
Edward C. Smith ◽  
Kevin L. Koudela
Keyword(s):  
Analytical Models ◽  
Main Rotor ◽  
Fluidic Devices ◽  
Simulation Results ◽  
Fluidic Circuits ◽  
Blade Loads ◽  
Even Harmonics

Replacing rigid pitch links on rotorcraft with coupled fluidic devices has the potential to reduce the aerodynamic blade loads transmitted through the pitch links. Analytical models of two fluidic devices coupled with three different fluidic circuits are derived. These passive fluidlastic systems are tuned, by varying the fluid inertances and capacitances of each fluidic circuit, to reduce the transmitted pitch-link loads for up to three main-rotor harmonics. The simulation results show loads reduction at the targeted odd and even harmonics of at least 95% and 72%, respectively.

Coupled Pitch Links for Multiharmonic Isolation Using Fluidic Circuits

2014 ◽  
Vol 59 (4) ◽  
pp. 1-11
Author(s):  
Lloyd H. Scarborough III ◽  
Christopher D. Rahn ◽  
Edward C. Smith ◽  
Kevin L. Koudela
Keyword(s):  
Experimental Validation ◽  
Analytical Models ◽  
Main Rotor ◽  
Fluidic Devices ◽  
Simulation Results ◽  
Fluidic Circuits ◽  
Blade Loads

Replacing stiff pitch links on rotorcraft with coupled fluidic devices has the potential to reduce the aerodynamic blade loads transmitted through the pitch links to the swashplate. Analytical models of two fluidic devices coupled with three different fluidic circuits are derived. These passive fluidlastic systems are tuned, by varying the fluid inertances and capacitances of each fluidic circuit, to reduce the transmitted pitch-link loads. The different circuit designs result in transmitted pitch-link loads reduction at up to three main rotor harmonics. The simulation results show loads reduction at the targeted out-of-phase and in-phase harmonics of up to 88% and 93%, respectively. Experimental validation of two of the fluidic circuits demonstrates loads reduction of up to 89% at the out-of-phase isolation frequencies and up to 81% at the in-phase isolation frequencies.

scholarly journals Kinematic Analysis of Three-Wire-Driven Parallel (TWDP) Robot

2011 ◽  
Vol 2-3 ◽  
pp. 302-307 ◽  
Author(s):  
Tao Yu ◽  
Qing Kai Han
Keyword(s):  
Static Analysis ◽  
Parallel Robot ◽  
Analytical Models ◽  
Kinematics Analysis ◽  
Mechanism Model ◽  
Good Movement ◽  
Dynamics And Control ◽  
Movement Stability ◽  
Simulation Results ◽  
And Control

In the paper, a novel new gravity-constrained (GC) three-wire-driven (TWD) parallel robot is proposed. With its mechanism model, three typical kinematics analytical models, including horizontal up-down motion, pitching motion and heeling motion and their corresponding simulations are given in detail. In static analysis, the change of tensions in the wires is calculated based on previous kinematics analysis. The simulation results show the robot has good movement stability. The paper can provide useful materials to study of dynamics and control on wire-driven robot.

A Unified Analytical Framework for Ship Domains

2009 ◽  
Vol 62 (4) ◽  
pp. 643-655 ◽  
Author(s):  
Ning Wang ◽  
Xianyao Meng ◽  
Qingyang Xu ◽  
Zuwen Wang
Keyword(s):  
Collision Avoidance ◽  
Traffic Engineering ◽  
Analytical Framework ◽  
Domain Model ◽  
Analytical Models ◽  
Collision Risk ◽  
Marine Traffic ◽  
Different Types ◽  
Domain Models ◽  
Simulation Results

Most of the existing typical ship domains have been comprehensively reviewed and classified. Most of these ship domains are described in a geometrical manner that is difficult to apply to practices and simulations in marine traffic engineering. According to different types of geometrical ship domains, we have proposed mathematical models, based on which a unified analytical framework has been established. It is feasible and practical for the analytical models to be applied to the assessment of navigational safety, collision avoidance and trajectory planning, etc. Finally, some computer simulations and comparative studies of the proposed domain model have been presented and the simulation results show that the uniform analytical framework for ship domains is effective and identical to the original geometrical ones. It should be noted that the analytical domain models could be directly applied in any collision risk, collision avoidance or VTS system while the geometrical ones would be more illustrative but less practical or analytical.

The improvement of stress correction in post-necking tension of cylindrical specimen

2019 ◽  
Vol 54 (3) ◽  
pp. 209-222 ◽  
Author(s):  
Junfu Chen ◽  
Zhiping Guan ◽  
Pinkui Ma ◽  
Zhigang Li ◽  
Xiangrui Meng
Keyword(s):  
Cross Section ◽  
Strain Distribution ◽  
Prediction Accuracy ◽  
Inverse Method ◽  
Cylindrical Specimen ◽  
Analytical Models ◽  
Large Strains ◽  
Stress And Strain ◽  
Simulation Results ◽  
Prediction Capability

In post-necking tension of cylindrical specimen, the stress corrections based on the current analytical models have relatively significant errors at large strains. In this study, the prediction capability of these models involving Bridgman model, Siebel model and Chen model is evaluated by performing a series of finite element simulations of uniaxial tension of cylindrical specimen with different hardening exponents varied from 0.05 to 0.3. Numerical analysis of stress and strain distributions on the necking cross section indicates that the considerable errors of the corrected stresses corresponding to large strains might be mainly attributed to the assumption of uniform strain distribution on the necking cross section in these analytical models. The modification strategies of these models are presented in order to improve their prediction accuracy of post-necking stresses, taking geometrical configuration of neck and material properties into consideration. Accordingly, the modification formulas are proposed based on simulation results, involving the radius of cross section of neck and the hardening exponent. Finally, these formulas are used to correct the stresses in the post-necking tension of Q345 cylindrical specimen, which are compared with the stresses identified through inverse method. The results indicate that the modified models significantly improve the prediction accuracy of post-necking stresses at large strains.

Coupled Fluidic Vibration Isolators for Rotorcraft Pitch Link Loads Reduction

2012 ◽  
Author(s):  
Nicolas A. Kurczewski ◽  
Lloyd H. Scarborough ◽  
Christopher D. Rahn ◽  
Edward C. Smith
Keyword(s):  
Harmonic Excitation ◽  
Wide Frequency Range ◽  
Rotor Speed ◽  
Frequency Range ◽  
Vibration Isolators ◽  
Transmitted Force ◽  
Fluidic Devices ◽  
Fluidic Device ◽  
Multiple Frequencies ◽  
Blade Loads

Replacing rigid pitch links on rotorcraft with coupled fluidic devices has the potential to reduce the aerodynamic blade loads transmitted from the blade root to the swashplate. An analytical model of two coupled fluidic isolators is derived and experimentally validated for even and odd harmonic pitch link loads. The system consists of two elastomeric pumpers with fluid chambers that are coupled by an inertia track. This passive fluidic device can be tuned to reduce the transmitted force at a particular odd harmonic of the rotor speed by tailoring the fluid inertance in the inertia track. Benchtop experimental results agree with theory, demonstrating a reduction in odd harmonic pitch link loads of up to 90% compared to the system without fluid. The coupled fluidic isolators also significantly reduce transmitted loads relative to a rigid pitch link over a wide frequency range. Simulation of a UH-60 Blackhawk retrofit example shows potential for targeted odd harmonic excitation loads reduction up to 94% for multiple frequencies without affecting the even harmonic excitation response.

Pitch Control for Wind Turbine in Yawed Inflow Condition

2014 ◽  
Author(s):  
Irving Paul Girsang ◽  
Jaspreet Singh Dhupia
Keyword(s):  
Wind Turbine ◽  
Bending Moments ◽  
Misalignment Angle ◽  
Operating Condition ◽  
Pitch Control ◽  
Angle Correction ◽  
Inflow Condition ◽  
Simulation Results ◽  
Blade Loads ◽  
Inflow Conditions

A wind turbine can experience yawed inflow with large yaw misalignment angle during faulty cases, such as faults in the yaw controller/drives, or during extreme atmospheric cases, such as thunderstorm downbursts. In such cases, it is risky for the turbine to continue operation because it is being exposed to large loads. Instead, it is recommended for the turbine to be transited to parking conditions. Currently, most turbine pitch controllers are designed without considering the yaw misalignment angle, correction of which is normally assigned to the yaw controller. This paper investigates the contribution of both a baseline and a proposed collective pitch controllers under yawed inflow conditions. The baseline controller tries to maintain the rated operating condition at an expense of large blade loads. On the contrary, simulation results show that the proposed controller slows down the turbine under the presence of yawed inflow, which helps to park the turbine and reduces the average blade root bending moments.

scholarly journals Aerodynamic and acoustic analysis of helicopter main rotor blade tips in hover

2016 ◽  
Vol 26 (7) ◽  
pp. 2101-2118 ◽  
Author(s):  
Lyaysan Ildusovna Garipova ◽  
Andrei Sergeevich Batrakov ◽  
Alexander Nikolaevich Kusyumov ◽  
Sergey Anatolievich Mikhaylov ◽  
George Barakos
Keyword(s):  
Rotor Blade ◽  
Acoustic Analysis ◽  
Main Rotor ◽  
Content Type ◽  
Helicopter Blades ◽  
Blade Tip ◽  
Helicopter Main Rotor ◽  
Main Rotor Blade ◽  
Blade Loads ◽  
Blade Tips

Purpose The design of main rotor blade tips is of interest to helicopter manufactures since the tip details affect the performance and acoustics of the rotor. The paper aims to discuss this issue. Design/methodology/approach In this paper, computation fluid dynamics is used to simulate the flow around hovering helicopter blades with different tip designs. For each type of blade tip a parametric study on the shape is also conducted for comparison calculations were performed the constant rotor thrust condition. The collective pitch and the cone angles of the blades were determined by at an iterative trimming process. Findings Analysis of the distributed blade loads shows that the tip geometry has a significant influence on aerodynamics and aeroacoustics especially for stations where blade loading is high. Originality/value The aeroacoustic characteristics of the rotors were obtained using Ffowcs Williams-Hawkings equations.

scholarly journals Improved Steamflood Analytical Model

2007 ◽  
Vol 10 (06) ◽  
pp. 638-643
Author(s):  
Suandy Chandra ◽  
Daulat Debataraja Mamora
Keyword(s):  
Analytical Model ◽  
Performance Prediction ◽  
Numerical Models ◽  
Production Performance ◽  
Analytical Models ◽  
Rock Properties ◽  
Oil Viscosity ◽  
Modified Model ◽  
Jones Model ◽  
Simulation Results

Summary The Jones (1981) steamflood model incorporates oil displacement by steam as described by Myhill and Stegemeier (1978), and a three-component capture factor based on empirical correlations. The main drawback of the model, however, is the unsatisfactory prediction of the oil production peak: It is usually significantly lower than the observed value. Our study focuses on improving this aspect of the Jones model. In our study, we simulated the production performance of a five-spot-steamflood-pattern unit and compared the results against those based on the Jones model (1981). To obtain a satisfactory match between simulation and Jones-analytical-model results, at the start and height of the production peak, the following refinements to the Jones model were necessary. First, the dimensionless steam-zone size AcD was modified to account for the decrease in oil viscosity during steamflood and its dependence on the steam injection rate. Second, the dimensionless volume of displaced oil produced VoD was modified from its square-root format to an exponential form. The modified model gave very satisfactory results for production performance for up to 20 years of simulated steamflood, compared to the original Jones model. Engineers will find the modified model an improved and useful tool for the prediction of steamflood-production performance. Introduction Steamflooding is a major enhanced-oil recovery (EOR) process applied to heavy oil reservoirs. A steamflood typically proceeds through four development phases: reservoir screening, pilot tests, fieldwide implementation, and reservoir management (Hong 1994). Steamflood-performance prediction is essential to provide information for the proper execution of each development phase. Three mathematical models (statistical, numerical, and analytical models) are often used to predict steamflood performance. Statistical models are based on the historical data of steamflood performance from other reservoirs which have similar oil and rock properties. A statistical model, however, does not include all the flow parameters, and thus may be inaccurate for a particular reservoir. Numerical models usually require a large amount of data input with lengthy calculations using computers; and they are usually CPU-, manpower- and time-consuming and also expensive. They may be extremely comprehensive and better serve as tools for research or advanced reservoir analysis. Meanwhile, analytical models are more economical, but at the expense of accuracy and flexibility. They serve as tools for engineering screening of possible reservoir candidates for field testing (Hong 1994). For many years, attempts have been made to provide analytical models for steamflood-production-performance prediction (Marx and Langenheim 1959; Boberg 1966; Mandl and Volek 1969; Neuman 1975; Myhill and Stegemeier 1978; Gomaa 1980; Jones 1981; van Lookeren 1977; Farouq Ali 1970; Miller and Leung 1985; Rhee et al. 1978; Aydelotte et al. 1982). None of these analytical models gives a comparison with simulation results. Miller and Leung (1985) presented comparison between their analytical model and simulation results for cumulative production vs time, but the comparison for production rate vs time is not available.

scholarly journals Development of a Model for Stormwater Runoff Prediction on Vertical Test Panels Coated with Plaster and Mortar

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2593
Author(s):  
Pablo Vega-Garcia ◽  
Regina Schwerd ◽  
Christian Scherer ◽  
Christoph Schwitalla ◽  
Brigitte Helmreich
Keyword(s):  
Stormwater Runoff ◽  
Construction Materials ◽  
Sampling Period ◽  
Analytical Models ◽  
New Model ◽  
Fraunhofer Institute ◽  
Building Facades ◽  
Simulation Results ◽  
Building Physics ◽  
Vertical Test

Leaching outdoor tests (LOT) are commonly used to assess the leaching of substances from construction materials. In this context, the amount of stormwater in contact with the surface material is of special interest for analyzing the runoff loads of substances from building façades. A numerical model was developed in MATLAB on the basis of previous analytical models to calculate the collected stormwater runoff volumes from the vertical test panels (VTP) during LOT. In the model, wind-driven rain (WDR) is considered to be the main mechanism for determining the amount of water impinging on the VTP, so it is a crucial factor in the modeling for the façade runoff. The new model makes it possible to simulate the runoff volumes from VTP that are covered with a wide variety of plaster and mortar. Using the new model, it was possible to relate the VTP runoff volumes obtained during an 18-month sampling period for LOTs performed at the Fraunhofer Institute for Building Physics in Valley, Germany. When comparing the simulation results with the field test accumulated runoffs, the model exhibited a difference of no more than 3.5% for each of the analyzed materials. The simulation results are satisfying, and the paper demonstrates the feasibility of the modelling approach for the runoff assessment of VTP covered with a variety of plaster and mortar.

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