Makino, Yoshikazu; Ohira, Keisuke; Makimoto, Takuya; Mitomo, Toshiteru; 牧野, 好和; 大平, 啓介; 牧本, 卓也; 三友, 俊輝
2011-01-01
Effects of static aeroelastic deformation of a wind-tunnel test model on the aerodynamic characteristics are discussed in wind-tunnel tests in the preliminary design phase of the silent supersonic technology demonstrator (S3TD). The static aeroelastic deformation of the main wing is estimated for JAXA 2m x 2m transonic wind-tunnel and 1m x 1m supersonic wind-tunnel by a finite element method (FEM) structural analysis in which its structural model is tuned with the model deformation calibratio...
Static Aeroelastic Analysis with an Inviscid Cartesian Method
Rodriguez, David L.; Aftosmis, Michael J.; Nemec, Marian; Smith, Stephen C.
2014-01-01
An embedded-boundary, Cartesian-mesh flow solver is coupled with a three degree-of-freedom structural model to perform static, aeroelastic analysis of complex aircraft geometries. The approach solves a nonlinear, aerostructural system of equations using a loosely-coupled strategy. An open-source, 3-D discrete-geometry engine is utilized to deform a triangulated surface geometry according to the shape predicted by the structural model under the computed aerodynamic loads. The deformation scheme is capable of modeling large deflections and is applicable to the design of modern, very-flexible transport wings. The coupling interface is modular so that aerodynamic or structural analysis methods can be easily swapped or enhanced. After verifying the structural model with comparisons to Euler beam theory, two applications of the analysis method are presented as validation. The first is a relatively stiff, transport wing model which was a subject of a recent workshop on aeroelasticity. The second is a very flexible model recently tested in a low speed wind tunnel. Both cases show that the aeroelastic analysis method produces results in excellent agreement with experimental data.
Static Aeroelastic Scaling and Analysis of a Sub-Scale Flexible Wing Wind Tunnel Model
Ting, Eric; Lebofsky, Sonia; Nguyen, Nhan; Trinh, Khanh
2014-01-01
This paper presents an approach to the development of a scaled wind tunnel model for static aeroelastic similarity with a full-scale wing model. The full-scale aircraft model is based on the NASA Generic Transport Model (GTM) with flexible wing structures referred to as the Elastically Shaped Aircraft Concept (ESAC). The baseline stiffness of the ESAC wing represents a conventionally stiff wing model. Static aeroelastic scaling is conducted on the stiff wing configuration to develop the wind tunnel model, but additional tailoring is also conducted such that the wind tunnel model achieves a 10% wing tip deflection at the wind tunnel test condition. An aeroelastic scaling procedure and analysis is conducted, and a sub-scale flexible wind tunnel model based on the full-scale's undeformed jig-shape is developed. Optimization of the flexible wind tunnel model's undeflected twist along the span, or pre-twist or wash-out, is then conducted for the design test condition. The resulting wind tunnel model is an aeroelastic model designed for the wind tunnel test condition.
Static Aeroelastic Effects of Formation Flight for Slender Unswept Wings
Hanson, Curtis E.
2009-01-01
The static aeroelastic equilibrium equations for slender, straight wings are modified to incorporate the effects of aerodynamically-coupled formation flight. A system of equations is developed by applying trim constraints and is solved for component lift distribution, trim angle-of-attack, and trim aileron deflection. The trim values are then used to calculate the elastic twist distribution of the wing box. This system of equations is applied to a formation of two gliders in trimmed flight. Structural and aerodynamic properties are assumed for the gliders, and solutions are calculated for flexible and rigid wings in solo and formation flight. It is shown for a sample application of two gliders in formation flight, that formation disturbances produce greater twist in the wingtip immersed in the vortex than for either the opposing wingtip or the wings of a similar airplane in solo flight. Changes in the lift distribution, resulting from wing twist, increase the performance benefits of formation flight. A flexible wing in formation flight will require greater aileron deflection to achieve roll trim than a rigid wing.
Static aeroelastic analysis including geometric nonlinearities based on reduced order model
Directory of Open Access Journals (Sweden)
Changchuan Xie
2017-04-01
Full Text Available This paper describes a method proposed for modeling large deflection of aircraft in nonlinear aeroelastic analysis by developing reduced order model (ROM. The method is applied for solving the static aeroelastic and static aeroelastic trim problems of flexible aircraft containing geometric nonlinearities; meanwhile, the non-planar effects of aerodynamics and follower force effect have been considered. ROMs are computational inexpensive mathematical representations compared to traditional nonlinear finite element method (FEM especially in aeroelastic solutions. The approach for structure modeling presented here is on the basis of combined modal/finite element (MFE method that characterizes the stiffness nonlinearities and we apply that structure modeling method as ROM to aeroelastic analysis. Moreover, the non-planar aerodynamic force is computed by the non-planar vortex lattice method (VLM. Structure and aerodynamics can be coupled with the surface spline method. The results show that both of the static aeroelastic analysis and trim analysis of aircraft based on structure ROM can achieve a good agreement compared to analysis based on the FEM and experimental result.
Quasi-Static Condensation of Aeroelastic Suspension Bridge Model
DEFF Research Database (Denmark)
Møller, Randi N.; Krenk, Steen; N. Svendsen, Martin
2017-01-01
for turbulence when considering the stability limit and further it is not possible to account for non-linear effects. These limitations suggest to do simulations of the aeroelastic response of long span bridges in the time domain. For this it is of interest to have an efficient model while still maintaining...
Static Aeroelastic Analysis of Flexible Wings via NASTRAN, Part I.
1982-12-01
recommended steps in designing and testing a NASTRAN module are: 1. Recognition of the Need. In designing a new DMAP sequence or running an extensive DMAP ...operate without the module then that course of action is recommended. In con- sidering a DMAP to solve his problem the user might compare MSC NASTRAN to...COSMIC NASTRAN . The MSC version contains many more modules and might have the proper DMAP modules where the COSMIC version did not. 2. Development of
Numerical studies of static aeroelastic effects on grid fin aerodynamic performances
Directory of Open Access Journals (Sweden)
Chengde HUANG
2017-08-01
Full Text Available The grid fin is an unconventional control surface used on missiles and rockets. Although aerodynamics of grid fin has been studied by many researchers, few considers the aeroelastic effects. In this paper, the static aeroelastic simulations are performed by the coupled viscous computational fluid dynamics with structural flexibility method in transonic and supersonic regimes. The developed coupling strategy including fluid–structure interpolation and volume mesh motion schemes is based on radial basis functions. Results are presented for a vertical and a horizontal grid fin mounted on a body. Horizontal fin results show that the deformed fin is swept backward and the axial force is increased. The deformations also induce the movement of center of pressure, causing the reduction and reversal in hinge moment for the transonic flow and the supersonic flow, respectively. For the vertical fin, the local effective incidences are increased due to the deformations so that the deformed normal force is greater than the original one. At high angles of attack, both the deformed and original normal forces experience a sudden reduction due to the interference of leeward separated vortices on the fin. Additionally, the increment in axial force is shown to correlate strongly with the increment in the square of normal force.
Ting, Eric; Nguyen, Nhan; Trinh, Khanh
2014-01-01
This paper presents a static aeroelastic model and longitudinal trim model for the analysis of a flexible wing transport aircraft. The static aeroelastic model is built using a structural model based on finite-element modeling and coupled to an aerodynamic model that uses vortex-lattice solution. An automatic geometry generation tool is used to close the loop between the structural and aerodynamic models. The aeroelastic model is extended for the development of a three degree-of-freedom longitudinal trim model for an aircraft with flexible wings. The resulting flexible aircraft longitudinal trim model is used to simultaneously compute the static aeroelastic shape for the aircraft model and the longitudinal state inputs to maintain an aircraft trim state. The framework is applied to an aircraft model based on the NASA Generic Transport Model (GTM) with wing structures allowed to flexibly deformed referred to as the Elastically Shaped Aircraft Concept (ESAC). The ESAC wing mass and stiffness properties are based on a baseline "stiff" values representative of current generation transport aircraft.
Kukreja, Sunil L.; Brenner, Martin J.
2006-01-01
This viewgraph presentation reviews the applicability of NARMAX structure detection to aeroelastic systems. In conclusion, the simulation results demonstrate bootstrap approach for structure computation of aircraft structural stiffness provided a high rate of true model selection: 1. T-test and stepwise regression methods had difficulty providing accurate results 2. Work contributes to understanding of the use of structure detection for modelling and identification of aerospace systems. 3. Limitation of model complexity that can be studied with these structure computation techniques 4. Result of the large number of candidate terms, for a given model order, and the data length required to guarantee convergence 5. Another approach to structure computation problem uses a least absolute shrinkage and selection operator (LASSO)
Kukreja, Sunil L.; Brenner, martin J.
2006-01-01
This viewgraph presentation reviews the 1. Motivation for the study 2. Nonlinear Model Form 3. Structure Detection 4. Least Absolute Shrinkage and Selection Operator (LASSO) 5. Objectives 6. Results 7. Assess LASSO as a Structure Detection Tool: Simulated Nonlinear Models 8. Applicability to Complex Systems: F/A-18 Active Aeroelastic Wing Flight Test Data. The authors conclude that 1. this is a novel approach for detecting the structure of highly over-parameterised nonlinear models in situations where other methods may be inadequate 2. that it is a practical significance in the analysis of aircraft dynamics during envelope expansion and could lead to more efficient control strategies and 3. this could allow greater insight into the functionality of various systems dynamics, by providing a quantitative model which is easily interpretable
Design and testing of an aeroelastically tailored wing under manoeuvre loading
Werter, N.P.M.; Sodja, J.; De Breuker, R.
2015-01-01
The design methodology and testing of an aeroelastically tailored wing subjected to manoeuvre loads is presented in this paper. The wing is designed using an aeroelastic analysis tool that is composed of a closely coupled nonlinear beam model and a vortex lattice aerodynamic model. The globally
Design and Testing of Aeroelastically Tailored Wings Under Maneuver Loading
Werter, N.P.M.; Sodja, J.; De Breuker, R.
2016-01-01
The goal of the present paper is to provide experimental validation data for the aeroelastic analysis of composite aeroelastically tailored wings with a closed-cell cross-sectional structure. Several rectangular wings with differ- ent skin thicknesses and composite layups are designed in order to
Federal Laboratory Consortium — FUNCTION: Provides the capability to perform large-scale structural loads testing on spacecraft and other structures. Results from these tests can be used to verify...
Ivanco, Thomas G.
2013-01-01
NASA Langley Research Center's Transonic Dynamics Tunnel (TDT) is the world's most capable aeroelastic test facility. Its large size, transonic speed range, variable pressure capability, and use of either air or R-134a heavy gas as a test medium enable unparalleled manipulation of flow-dependent scaling quantities. Matching these scaling quantities enables dynamic similitude of a full-scale vehicle with a sub-scale model, a requirement for proper characterization of any dynamic phenomenon, and many static elastic phenomena. Select scaling parameters are presented in order to quantify the scaling advantages of TDT and the consequence of testing in other facilities. In addition to dynamic testing, the TDT is uniquely well-suited for high risk testing or for those tests that require unusual model mount or support systems. Examples of recently conducted dynamic tests requiring unusual model support are presented. In addition to its unique dynamic test capabilities, the TDT is also evaluated in its capability to conduct aerodynamic performance tests as a result of its flow quality. Results of flow quality studies and a comparison to a many other transonic facilities are presented. Finally, the ability of the TDT to support future NASA research thrusts and likely vehicle designs is discussed.
NUMERICAL APPROACH IN AEROELASTICITY
Directory of Open Access Journals (Sweden)
Oskar SLOBODA
2016-12-01
Full Text Available Aircraft wing design processes should comprise specific analyses oriented towards aeroelasticity, which is one of the essential factors determining flight envelope boundaries. For such cases, static or dynamic aeroelastic phenomena can be simulated using CFD simulation software. ANSYS software offers the fluid structure interaction (FSI method for solving this multiphysics problem
Predicting the aeroelastic behavior of a wind-tunnel model using transonic small disturbance theory
Silva, Walter A.; Bennett, Robert M.
1990-01-01
The CAP-TSD (Computational Aeroelasticity Program - Transonic Small Disturbance) code, developed at the NASA-Langley Research Center, is applied to the Active Flexible Wing (AFW) wind-tunnel model for prediction of the model's transonic aeroelastic behavior. Static aeroelastic solutions using CAP-TSD are computed. Dynamic (flutter) analyses are then performed as perturbations about the static aeroelastic deformations of the AFW. The accuracy of the static aeroelastic procedure is investigated by comparing analytical results to those from AFW wind-tunnel experiments. Dynamic results are presented in the form of root loci at different Mach numbers for a heavy gas and for air test mediums. The resultant flutter boundaries for both gases, and the effects of viscous damping and angle of attack on the flutter boundary in air, are also presented.
Nonlinear aeroelastic behavior of compliant airfoils
International Nuclear Information System (INIS)
Thwapiah, G; Campanile, L F
2010-01-01
Since the beginning of aviation and up to the present time, airfoils have always been built as rigid structures. They are designed to fly under their divergence speed in order to avoid static aeroelastic instabilities and the resulting large deformations, which are not compatible with the typically low compliance of such airfoils. In recent years, research on airfoil morphing has generated interest in innovative ideas like the use of compliant systems, i.e. systems built to allow for large deformations without failure, in airfoil construction. Such systems can operate in the neighborhood of divergence and take advantage of large aeroelastic servo-effects. This, in turn, allows compact, advanced actuators to control the airfoil's deformation and loads, and hence complement or even replace conventional flaps. In order to analyze and design such compliant, active aeroelastic structures a nonlinear approach to static aeroelasticity is needed, which takes into account the effect of large deformations on aerodynamics and structure. Such an analytical approach is presented in this paper and applied to a compliant passive airfoil as the preliminary step in the realization of a piezoelectrically driven, active aeroelastic airfoil. Wind tunnel test results are also presented and compared with the analytic prediction. The good agreement and the observed behavior in the wind tunnel give confidence in the potential of this innovative idea
Nonlinear aeroelastic behavior of compliant airfoils
Thwapiah, G.; Campanile, L. F.
2010-03-01
Since the beginning of aviation and up to the present time, airfoils have always been built as rigid structures. They are designed to fly under their divergence speed in order to avoid static aeroelastic instabilities and the resulting large deformations, which are not compatible with the typically low compliance of such airfoils. In recent years, research on airfoil morphing has generated interest in innovative ideas like the use of compliant systems, i.e. systems built to allow for large deformations without failure, in airfoil construction. Such systems can operate in the neighborhood of divergence and take advantage of large aeroelastic servo-effects. This, in turn, allows compact, advanced actuators to control the airfoil's deformation and loads, and hence complement or even replace conventional flaps. In order to analyze and design such compliant, active aeroelastic structures a nonlinear approach to static aeroelasticity is needed, which takes into account the effect of large deformations on aerodynamics and structure. Such an analytical approach is presented in this paper and applied to a compliant passive airfoil as the preliminary step in the realization of a piezoelectrically driven, active aeroelastic airfoil. Wind tunnel test results are also presented and compared with the analytic prediction. The good agreement and the observed behavior in the wind tunnel give confidence in the potential of this innovative idea.
Curry, R. E.; Sim, A. G.
1984-01-01
A low-speed flight investigation has provided total force and moment coefficients and aeroelastic effects for the AD-1 oblique-wing research airplane. The results were interpreted and compared with predictions that were based on wind tunnel data. An assessment has been made of the aeroelastic wing bending design criteria. Lateral-directional trim requirements caused by asymmetry were determined. At angles of attack near stall, flow visualization indicated viscous flow separation and spanwise vortex flow. These effects were also apparent in the force and moment data.
Mourey, D. J.
1979-01-01
The aspects of flight testing an aeroelastically tailored forward swept research wing on a BQM-34F drone vehicle are examined. The geometry of a forward swept wing, which is incorporated into the BQM-34F to maintain satisfactory flight performance, stability, and control is defined. A preliminary design of the aeroelastically tailored forward swept wing is presented.
40 CFR 53.64 - Test procedure: Static fractionator test.
2010-07-01
... 40 Protection of Environment 5 2010-07-01 2010-07-01 false Test procedure: Static fractionator test. 53.64 Section 53.64 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Performance Characteristics of Class II Equivalent Methods for PM2.5 § 53.64 Test procedure: Static...
Flight Test of the F/A-18 Active Aeroelastic Wing Airplane
Voracek, David
2007-01-01
A viewgraph presentation of flight tests performed on the F/A active aeroelastic wing airplane is shown. The topics include: 1) F/A-18 AAW Airplane; 2) F/A-18 AAW Control Surfaces; 3) Flight Test Background; 4) Roll Control Effectiveness Regions; 5) AAW Design Test Points; 6) AAW Phase I Test Maneuvers; 7) OBES Pitch Doublets; 8) OBES Roll Doublets; 9) AAW Aileron Flexibility; 10) Phase I - Lessons Learned; 11) Control Law Development and Verification & Validation Testing; 12) AAW Phase II RFCS Envelopes; 13) AAW 1-g Phase II Flight Test; 14) Region I - Subsonic 1-g Rolls; 15) Region I - Subsonic 1-g 360 Roll; 16) Region II - Supersonic 1-g Rolls; 17) Region II - Supersonic 1-g 360 Roll; 18) Region III - Subsonic 1-g Rolls; 19) Roll Axis HOS/LOS Comparison Region II - Supersonic (open-loop); 20) Roll Axis HOS/LOS Comparison Region II - Supersonic (closed-loop); 21) AAW Phase II Elevated-g Flight Test; 22) Region I - Subsonic 4-g RPO; and 23) Phase II - Lessons Learned
Bartels, Robert E.; Funk, Christie; Scott, Robert C.
2015-01-01
Research focus in recent years has been given to the design of aircraft that provide significant reductions in emissions, noise and fuel usage. Increases in fuel efficiency have also generally been attended by overall increased wing flexibility. The truss-braced wing (TBW) configuration has been forwarded as one that increases fuel efficiency. The Boeing company recently tested the Subsonic Ultra Green Aircraft Research (SUGAR) Truss-Braced Wing (TBW) wind-tunnel model in the NASA Langley Research Center Transonic Dynamics Tunnel (TDT). This test resulted in a wealth of accelerometer data. Other publications have presented details of the construction of that model, the test itself, and a few of the results of the test. This paper aims to provide a much more detailed look at what the accelerometer data says about the onset of aeroelastic instability, usually known as flutter onset. Every flight vehicle has a location in the flight envelope of flutter onset, and the TBW vehicle is not different. For the TBW model test, the flutter onset generally occurred at the conditions that the Boeing company analysis said it should. What was not known until the test is that, over a large area of the Mach number dynamic pressure map, the model displayed wing/engine nacelle aeroelastic limit cycle oscillation (LCO). This paper dissects that LCO data in order to provide additional insights into the aeroelastic behavior of the model.
Peterson, R. L.; Warmbrodt, W.
1984-01-01
A hover test of a full-scale, hingeless rotor system was conducted in the NASA Ames 40- by 80-foot wind tunnel. The rotor was tested on the Ames rotor test apparatus. Rotor aeroelastic stability, performance, and loads at various rotational speeds and thrust coefficients were investigated. The primary objective was to determine the inplane stability characteristics of the rotor system. Rotor inplane damping data were obtained for operation between 350 and 425 rpm (design speed), and for thurst coefficients between 0.0 and 0.12. The rotor was stable for all conditions tested. At constant rotor rotational speed, a minimum inplane dampling level was obtained at a thrust coefficient approximately = 0.02. At constant rotor lift, a minimum in rotor inplane damping was measured at 400 rpm.
DEFF Research Database (Denmark)
Acampora, Antonio; Georgakis, Christos T.; Macdonald, J.H.G.
2014-01-01
and excitation from the deck and/or towers. Although there have been many observations of large cable vibrations on bridges, there are relatively few cases of direct full-scale cable vibration and wind measurements, and most research has been based on wind tunnel tests and theoretical modelling.This paper...... presents results from full-scale measurements on the special arrangement of twin cables adopted for the Øresund Bridge. The monitoring system records wind and weather conditions, as well as accelerations of certain cables and a few locations on the deck and tower. Using the Eigenvalue Realization Algorithm...... (ERA), the damping and stiffness matrices are identified for different vibration modes of the cables, with sufficient accuracy to identify changes in the total effective damping and stiffness matrices due to the aeroelastic forces acting on the cables. The damping matrices identified from the full-scale...
30 CFR 18.67 - Static-pressure tests.
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Static-pressure tests. 18.67 Section 18.67....67 Static-pressure tests. Static-pressure tests shall be conducted by the applicant on each enclosure... pressure to be applied shall be 150 pounds per square inch (gage) or one and one-half times the maximum...
Static Test Compaction As A Minimum Covering Problem | Boateng ...
African Journals Online (AJOL)
Large numbers of test stimuli impact on the time and cost of test application. Hence there is the need to keep numbers of test stimuli low while maintaining as high fault coverage as possible. In this paper, static compaction of test stimuli is seen as a minimization problem. The task of static compaction of a set of test stimuli ...
STATIC TEST COMPACTION AS A MINIMUM COVERING PROBLEM
African Journals Online (AJOL)
DEPT OF AGRICULTURAL ENGINEERING
ABSTRACT. Large numbers of test stimuli impact on the time and cost of test application. Hence there is the need to keep numbers of test stimuli low while maintaining as high fault coverage as possible. In this paper, static compaction of test stimuli is seen as a minimization problem. The task of static compaction of a set of ...
14 CFR 25.681 - Limit load static tests.
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Limit load static tests. 25.681 Section 25.681 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... load static tests. (a) Compliance with the limit load requirements of this Part must be shown by tests...
14 CFR 27.681 - Limit load static tests.
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Limit load static tests. 27.681 Section 27.681 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... static tests. (a) Compliance with the limit load requirements of this part must be shown by tests in...
14 CFR 29.681 - Limit load static tests.
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Limit load static tests. 29.681 Section 29.681 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... load static tests. (a) Compliance with the limit load requirements of this part must be shown by tests...
Aeroelastic Optimization Design for High-Aspect-Ratio Wings with Large Deformation
Directory of Open Access Journals (Sweden)
Changchuan Xie
2017-01-01
Full Text Available This paper presents a framework of aeroelastic optimization design for high-aspect-ratio wing with large deformation. A highly flexible wing model for wind tunnel test is optimized subjected to multiple aeroelastic constraints. Static aeroelastic analysis is carried out for the beamlike wing model, using a geometrically nonlinear beam formulation coupled with the nonplanar vortex lattice method. The flutter solutions are obtained using the P-K method based on the static equilibrium configuration. The corresponding unsteady aerodynamic forces are calculated by nonplanar doublet-lattice method. This paper obtains linear and nonlinear aeroelastic optimum results, respectively, by the ISIGHT optimization platform. In this optimization problem, parameters of beam cross section are chosen as the design variables to satisfy the displacement, flutter, and strength requirements, while minimizing wing weight. The results indicate that it is necessary to consider geometrical nonlinearity in aeroelastic optimization design. In addition, optimization strategies are explored to simplify the complex optimization process and reduce the computing time. Different criterion values are selected and studied for judging the effects of the simplified method on the computing time and the accuracy of results. In this way, the computing time is reduced by more than 30% on the premise of ensuring the accuracy.
14 CFR 23.681 - Limit load static tests.
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Limit load static tests. 23.681 Section 23.681 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION AIRCRAFT... Control Systems § 23.681 Limit load static tests. (a) Compliance with the limit load requirements of this...
Experimental set-up for advanced aeroelastic tests on sectional models
Czech Academy of Sciences Publication Activity Database
Král, Radomil; Pospíšil, Stanislav; Náprstek, Jiří
2016-01-01
Roč. 40, č. 1 (2016), s. 3-13 ISSN 0732-8818 R&D Projects: GA ČR GA103/09/0094; GA AV ČR IAA200710902; GA MŠk(CZ) ED1.1.00/02.0060 Institutional support: RVO:68378297 Keywords : bridge aeroelasticity * wind tunnel * experimental set-up * non-linear response Subject RIV: JM - Building Engineering Impact factor: 0.932, year: 2016 http://link.springer.com/article/10.1007%2Fs40799-015-0004-6
Huy, N.Q.
2010-01-01
Pile testing, which plays an importance role in the field of deep foundation design, is performed by static and non-static methods to provide information about the following issues: (Poulos, 1998) - The ultimate capacity of a single pile. - The load-displacement behavior of a pile. - The performance
30 CFR 7.307 - Static pressure test.
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Static pressure test. 7.307 Section 7.307... pressure test. (a) Test procedure. (1) The enclosure shall be internally pressurized to a minimum of 150 psig and the pressure maintained for a minimum of 10 seconds. (2) Following the pressure hold, the...
Multiaxial pedicle screw designs: static and dynamic mechanical testing.
Stanford, Ralph Edward; Loefler, Andreas Herman; Stanford, Philip Mark; Walsh, William R
2004-02-15
Randomized investigation of multiaxial pedicle screw mechanical properties. Measure static yield and ultimate strengths, yield stiffness, and fatigue resistance according to an established model. Compare these measured properties with expected loads in vivo. Multiaxial pedicle screws provide surgical versatility, but the complexity of their design may reduce their strength and fatigue resistance. There is no published data on the mechanical properties of such screws. Screws were assembled according to a vertebrectomy model for destructive mechanical testing. Groups of five assemblies were tested in static tension and compression and subject to three cyclical loads. Modes of failure, yield, and ultimate strength, yield stiffness, and cycles to failure were determined for six designs of screw. Static compression yield loads ranged from 217.1 to 388.0 N and yield stiffness from 23.7 to 38.0 N/mm. Cycles to failure ranged from 42 x 10(3) to 4,719 x 10(3) at 75% of static ultimate load. There were significant differences between designs in all modes of testing. Failure occurred at the multiaxial link in static and cyclical compression. Bending yield strengths just exceeded loads expected in vivo. Multiaxial designs had lower static bending yield strength than fixed screw designs. Five out of six multiaxial screw designs achieved one million cycles at 200 N in compression bending. "Ball-in-cup" multiaxial locking mechanisms were vulnerable to fatigue failure. Smooth surfaces and thicker material appeared to be protective against fatigue failure.
Aeroelasticity Benchmark Assessment: Subsonic Fixed Wing Program
Florance, Jennifer P.; Chwalowski, Pawel; Wieseman, Carol D.
2010-01-01
The fundamental technical challenge in computational aeroelasticity is the accurate prediction of unsteady aerodynamic phenomena and the effect on the aeroelastic response of a vehicle. Currently, a benchmarking standard for use in validating the accuracy of computational aeroelasticity codes does not exist. Many aeroelastic data sets have been obtained in wind-tunnel and flight testing throughout the world; however, none have been globally presented or accepted as an ideal data set. There are numerous reasons for this. One reason is that often, such aeroelastic data sets focus on the aeroelastic phenomena alone (flutter, for example) and do not contain associated information such as unsteady pressures and time-correlated structural dynamic deflections. Other available data sets focus solely on the unsteady pressures and do not address the aeroelastic phenomena. Other discrepancies can include omission of relevant data, such as flutter frequency and / or the acquisition of only qualitative deflection data. In addition to these content deficiencies, all of the available data sets present both experimental and computational technical challenges. Experimental issues include facility influences, nonlinearities beyond those being modeled, and data processing. From the computational perspective, technical challenges include modeling geometric complexities, coupling between the flow and the structure, grid issues, and boundary conditions. The Aeroelasticity Benchmark Assessment task seeks to examine the existing potential experimental data sets and ultimately choose the one that is viewed as the most suitable for computational benchmarking. An initial computational evaluation of that configuration will then be performed using the Langley-developed computational fluid dynamics (CFD) software FUN3D1 as part of its code validation process. In addition to the benchmarking activity, this task also includes an examination of future research directions. Researchers within the
Energy Technology Data Exchange (ETDEWEB)
Soederberg, M.
1990-01-01
The GAROS system for general analysis of rotating aeroelastic structures is used to analyse the behaviour of the WTS 3 Maglarp wind turbine, situated in Maglarp, Sweden. The GAROS method is based on a branch mode technique and modal reduction. Stability analyses of the total tower-rotor system as well as numerical time integration analyses are performed within the GAROS system. The FE-model made by Anders Henoch, AIMS, for FFA is used as a base for this investigation. Some modifications concerning center of gravity of the rotor and teeter bearing/hinge have been made in the finite element model. In this report simulated values of loads in the blades are compaed to measured data. The unstable yaw behaviour of the WTS 3 was also found in the behaviour of the model. The amount of yaw-angle rotation in the model was also found to be according to measured values when induced velocities were accounted for in the aerodynamic force calculations. The analyses in general show good agreement between simulated and measured values. This paper was presented at the European Wind Energy Conference in Glasgow, 10-13 July, 1989.
A New Static and Fatigue Compression Test Method for Composites
DEFF Research Database (Denmark)
Bech, Jakob Ilsted; Goutianos, Stergios; Løgstrup Andersen, Tom
2011-01-01
A new test method to determine the compressive properties of composite materials under both static and fatigue loading was developed. The novel fixture is based on the concept of transmitting the load by a fixed ratio of end-to-shear loading. The end-to-shear load ratio is kept fixed during...... the test through a mechanical mechanism, which automatically maintains the gripping pressure. The combined loading method has proven very efficient in static loading and is used in the new fixture which is specially designed for fatigue testing. Optimum gripping (shear loading) and alignment of the test...... coupon are achieved throughout the fatigue life. The fatigue strength obtained is more reliable because bending of the specimen due to poor gripping and alignment is minimised. The application of the new fixture to static and fatigue compression is demonstrated by using unidirectional carbon...
Static and Dynamic Handgrip Strength Endurance: Test-Retest Reproducibility.
Gerodimos, Vassilis; Karatrantou, Konstantina; Psychou, Dimitra; Vasilopoulou, Theodora; Zafeiridis, Andreas
2017-03-01
This study investigated the reliability of static and dynamic handgrip strength endurance using different protocols and indicators for the assessment of strength endurance. Forty young, healthy men and women (age, 18-22 years) performed 2 handgrip strength endurance protocols: a static protocol (sustained submaximal contraction at 50% of maximal voluntary contraction) and a dynamic one (8, 10, and 12 maximal repetitions). The participants executed each protocol twice to assess the test-retest reproducibility. Total work and total time were used as indicators of strength endurance in the static protocol; the strength recorded at each maximal repetition, the percentage change, and fatigue index were used as indicators of strength endurance in the dynamic protocol. The static protocol showed high reliability irrespective of sex and hand for total time and work. The 12-repetition dynamic protocol exhibited moderate-high reliability for repeated maximal repetitions and percentage change; the 8- and 10-repetition protocols demonstrated lower reliability irrespective of sex and hand. The fatigue index was not a reliable indicator for the assessment of dynamic handgrip endurance. Static handgrip endurance can be measured reliably using the total time and total work as indicators of strength endurance. For the evaluation of dynamic handgrip endurance, the 12-repetition protocol is recommended, using the repeated maximal repetitions and percentage change as indicators of strength endurance. Practitioners should consider the static (50% maximal voluntary contraction) and dynamic (12 repeated maximal repetitions) protocols as reliable for the assessment of handgrip strength endurance. The evaluation of static endurance in conjunction with dynamic endurance would provide more complete information about hand function. Copyright © 2017 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.
Design, construction and testing of a base driven static inverter ...
African Journals Online (AJOL)
Based on the active circuit of a 50Hz astable multivibrator, a base driven static inverter has been designed, constructed and tested. Design is able to convert small amounts of dc current to their amplified ac equivalents. A conversion of 12V dc input to the usual domestic range of 220-240V ac is also derivable from the ...
Testing static tradeoff theory against pecking order models of capital ...
African Journals Online (AJOL)
We test two models with the purpose of finding the best empirical explanation for corporate financing choice of a cross section of 27 Nigerian quoted companies. The models were developed to represent the Static tradeoff Theory and the Pecking order Theory of capital structure with a view to make comparison between ...
Testing static tradeoff theiry against pecking order models of capital ...
African Journals Online (AJOL)
We test two models with the purpose of finding the best empirical explanation for corporate financing choice of a cross section of 27 Nigerian quoted companies. The models were developed to represent the Static tradeoff Theory and the Pecking order Theory of capital structure with a view to make comparison between ...
Test chambers for cell culture in static magnetic field
Energy Technology Data Exchange (ETDEWEB)
Glinka, Marek, E-mail: mag@iq.pl [Research and Development Centre of Electrical Machines. 188 Rozdzienskiego Street, 40-203 Katowice (Poland); Gawron, Stanisław, E-mail: s.gawron@komel.katowice.pl [Research and Development Centre of Electrical Machines. 188 Rozdzienskiego Street, 40-203 Katowice (Poland); Sieroń, Aleksander, E-mail: sieron1@tlen.pl [Department of Internal Diseases, Angiology and Physical Medicine in Bytom. Medical University of Silesia in Katowice. 15 Batorego Street, 41-902 Bytom (Poland); Pawłowska–Góral, Katarzyna, E-mail: kgoral@sum.edu.pl [Department of Food and Nutrition in Sosnowiec. Medical University of Silesia in Katowice. 8 Jednosci Street, 41-200 Sosnowiec (Poland); Cieślar, Grzegorz, E-mail: cieslar1@tlen.pl [Department of Internal Diseases, Angiology and Physical Medicine in Bytom. Medical University of Silesia in Katowice. 15 Batorego Street, 41-902 Bytom (Poland); Sieroń–Stołtny, Karolina [Department of Internal Diseases, Angiology and Physical Medicine in Bytom. Medical University of Silesia in Katowice. 15 Batorego Street, 41-902 Bytom (Poland)
2013-04-15
Article presents a test chamber intended to be used for in vitro cell culture in homogenous constant magnetic field with parametrically variable magnitude. We constructed test chambers with constant parameters of control homeostasis of cell culture for the different parameters of static magnetic field. The next step was the computer calculation of 2D and 3D simulation of the static magnetic field distribution in the chamber. The analysis of 2D and 3D calculations of magnetic induction in the cells' exposition plane reveals, in comparison to the detection results, the greater accuracy of 2D calculations (Figs. 9 and 10). The divergence in 2D method was 2–4% and 8 to 10% in 3D method (reaching 10% only out of the cells′ cultures margins). -- Highlights: ► We present test chamber to be used for in vitro cell culture in static magnetic field. ► The technical data of the chamber construction was presented. ► 2D versus 3D simulation of static magnetic field distribution in chamber was reported. ► We report the accuracy of 2D calculation than 3D.
Self-Testing Static Random-Access Memory
Chau, Savio; Rennels, David
1991-01-01
Proposed static random-access memory for computer features improved error-detecting and -correcting capabilities. New self-testing scheme provides for detection and correction of errors at any time during normal operation - even while data being written into memory. Faults in equipment causing errors in output data detected by repeatedly testing every memory cell to determine whether it can still store both "one" and "zero", without destroying data stored in memory.
Static Tension Tests on Axially Loaded Pile Segments in Sand
DEFF Research Database (Denmark)
Thomassen, Kristina; Andersen, Lars Vabbersgaard; Ibsen, Lars Bo
This paper provides laboratory test results of static axially loaded piles in sand. With a newly developed test setup, the pile-soil interface friction was investigated by using an open-ended steel pile segment with a diameter of 0.5 m. Use of a pile length of 1 m enabled the pile-soil interface...... friction to be analyzed at a given soil horizon while increasing the vertical effective stress in the sand. Test results obtained by this approach can be analyzed as single t-z curves and compared to predictions of unit shaft friction from current design methods for offshore foundations. The test results...
A Comparison of Quasi-Static Indentation Testing to Low Velocity Impact Testing
Nettles, Alan T.; Douglas, Michael J.
2001-01-01
The need for a static test method for modeling low-velocity foreign object impact events to composites would prove to be very beneficial to researchers since much more data can be obtained from a static test than from an impact test. In order to examine if this is feasible, a series of static indentation and low velocity impact tests were carried out and compared. Square specimens of many sizes and thickness were utilized to cover the array of types of low velocity impact events. Laminates with a n/4 stacking sequence were employed since this is by the most common type of engineering laminate. Three distinct flexural rigidities under two different boundary conditions were tested in order to obtain damage due to large deflections, contact stresses and both to examine if the static indentation-impact comparisons are valid under the spectrum of damage modes that can be experienced. Comparisons between static indentation and low velocity impact tests were based on the maximum applied transverse load. The dependent parameters examined included dent depth, back surface crack length, delamination area and to a limited extent, load-deflection behavior. Results showed that no distinct differences could be seen between the static indentation tests and the low velocity impact tests, indicating that static indentation can be used to represent a low velocity impact event.
FEM simulation of static loading test of the Omega beam
Bílý, Petr; Kohoutková, Alena; Jedlinský, Petr
2017-09-01
The paper deals with a FEM simulation of static loading test of the Omega beam. Omega beam is a precast prestressed high-performance concrete element with the shape of Greek letter omega. Omega beam was designed as a self-supporting permanent formwork member for construction of girder bridges. FEM program ATENA Science was exploited for simulation of load-bearing test of the beam. The numerical model was calibrated using the data from both static loading test and tests of material properties. Comparison of load-displacement diagrams obtained from the experiment and the model was conducted. Development of cracks and crack patterns were compared. Very good agreement of experimental data and the FEM model was reached. The calibrated model can be used for design of optimized Omega beams in the future without the need of expensive loading tests. The calibrated material model can be also exploited in other types of FEM analyses of bridges constructed with the use of Omega beams, such as limit state analysis, optimization of shear connectors, prediction of long-term deflections or prediction of crack development.
STATIC TESTS OF UNCONVENTIONAL PROPULSION UNITS FOR ULTRALIGHT AIRPLANES
Directory of Open Access Journals (Sweden)
Martin Helmich
2014-06-01
Full Text Available This paper presents static tests of a new unconventional propulsion unit for small aviation airplanes. Our laboratory stand – a fan drive demonstrator – enables us to compare various design options. We performed experiments to verify the propulsion functionality and a measurement procedure to determine the available thrust of the propulsion unit and its dependence on engine speed. The results used for subsequent optimization include the operating parameters of the propulsion unit, and the temperature and velocity fields in parts of the air duct.
AEROTAXI ground static test and finite element model validation
Directory of Open Access Journals (Sweden)
Radu BISCA
2011-06-01
Full Text Available In this presentation, we will concentrate on typical Ground Static Test (GST and Finite Element (FE software comparisons. It is necessary to note, that standard GST are obligatory for any new aircraft configuration. We can mention here the investigations of the AeroTAXITM, a small aircraft configuration, using PRODERA® equipment. A Finite Element Model (FEM of the AeroTAXITM has been developed in PATRAN/NASTRAN®, partly from a previous ANSYS® model. FEM can be used to investigate potential structural modifications or changes with realistic component corrections. Model validation should be part of every modern engineering analysis and quality assurance procedure.
A modern course in aeroelasticity
Dowell, Earl H
2015-01-01
This book cover the basics of aeroelasticity or the dynamics of fluid-structure interaction. While the field began in response to the rapid development of aviation, it has now expanded into many branches of engineering and scientific disciplines and treat physical phenomena from aerospace engineering, bioengineering, civil engineering, and mechanical engineering in addition to drawing the attention of mathematicians and physicists. The basic questions addressed are dynamic stability and response of fluid structural systems as revealed by both linear and nonlinear mathematical models and correlation with experiment. The use of scaled models and full scale experiments and tests play a key role where theory is not considered sufficiently reliable. In this new edition the more recent literature on nonlinear aeroelasticity has been brought up to date and the opportunity has been taken to correct the inevitable typographical errors that the authors and our readers have found to date. The early chapters of t...
Aerodynamic Tests on a Static California Sea Lion Flipper
Kulkarni, Aditya A.; Leftwich, Megan C.
2017-11-01
Unlike most biological swimmers that use BCF swimming, the California sea lion relies on its foreflippers for thrust production. This unique swimming style, which lacks a characteristic oscillation frequency, allows the sea lion to leave less traceable wake while also producing high amounts of thrust. While the swimming energetics of the animal have been studied, almost nothing is known about the fluid dynamics of the system. To overcome this lack of basic understanding, a three-dimensional model of the flipper was developed using structured light-based scanners. Cross sections of the flipper model resemble the shape of the airfoils typically found in wings with thickness ratios, 11% - 37%. Wind tunnel testing conducted on static flipper revealed that positive lift was being generated at negative angles of attack. This is hypothesized to help the sea lions considerably in perform tight maneuvers with a small turning radius. The wake structure downstream of the flipper was captured using Particle Image Velocimetry (PIV).
Methods and advances in the study of aeroelasticity with uncertainties
Directory of Open Access Journals (Sweden)
Dai Yuting
2014-06-01
Full Text Available Uncertainties denote the operators which describe data error, numerical error and model error in the mathematical methods. The study of aeroelasticity with uncertainty embedded in the subsystems, such as the uncertainty in the modeling of structures and aerodynamics, has been a hot topic in the last decades. In this paper, advances of the analysis and design in aeroelasticity with uncertainty are summarized in detail. According to the non-probabilistic or probabilistic uncertainty, the developments of theories, methods and experiments with application to both robust and probabilistic aeroelasticity analysis are presented, respectively. In addition, the advances in aeroelastic design considering either probabilistic or non-probabilistic uncertainties are introduced along with aeroelastic analysis. This review focuses on the robust aeroelasticity study based on the structured singular value method, namely the μ method. It covers the numerical calculation algorithm of the structured singular value, uncertainty model construction, robust aeroelastic stability analysis algorithms, uncertainty level verification, and robust flutter boundary prediction in the flight test, etc. The key results and conclusions are explored. Finally, several promising problems on aeroelasticity with uncertainty are proposed for future investigation.
Cox, T. H.; Gilyard, G. B.
1986-01-01
The drones for aerodynamic and structural testing (DAST) project was designed to control flutter actively at high subsonic speeds. Accurate knowledge of the structural model was critical for the successful design of the control system. A ground vibration test was conducted on the DAST vehicle to determine the structural model characteristics. This report presents and discusses the vibration and test equipment, the test setup and procedures, and the antisymmetric and symmetric mode shape results. The modal characteristics were subsequently used to update the structural model employed in the control law design process.
Aeroelastic Analysis of Modern Complex Wings Using ENSAERO and NASTRAN
Bhardwaj, Manoj
1995-01-01
A process is presented by which static aeroelastic analysis is performed using Euler flow equations in conjunction with an advanced structural analysis tool, NASTRAN. The process deals with the interfacing of two separate codes in the fields of computational fluid dynamics (CFD) and computational structural dynamics (CSD). The process is demonstrated successfully on an F/A-18 Stabilator (horizontal tail).
Static Aeroelastic Effects on High Performance Aircraft
1987-06-01
0 -Non lintaritA de servo coemmande (saturation, non lin~arite du nod~le" hydraulique dynemnique). On prochde A la condensation en "rigiditA" di probl...llencastranantDe-Iaete"oteet 3. Axe de transmission 5o8 4I. Encastr’ement "int’ini M ,7 5. Systlme de flector q3 A Tnaer~cer 6. V~rin hydraulique agericu...fonction de .1 ’ncidance. Mesure impows.ble = fOttement 11-6 S Tangage MA =0.78 01. 60 reactsur’ Least rbacteui’.4ba Vitr ri.n hydraulique 0g 0-0 2.0
Aeroelasticity of morphing wings using neural networks
Natarajan, Anand
In this dissertation, neural networks are designed to effectively model static non-linear aeroelastic problems in adaptive structures and linear dynamic aeroelastic systems with time varying stiffness. The use of adaptive materials in aircraft wings allows for the change of the contour or the configuration of a wing (morphing) in flight. The use of smart materials, to accomplish these deformations, can imply that the stiffness of the wing with a morphing contour changes as the contour changes. For a rapidly oscillating body in a fluid field, continuously adapting structural parameters may render the wing to behave as a time variant system. Even the internal spars/ribs of the aircraft wing which define the wing stiffness can be made adaptive, that is, their stiffness can be made to vary with time. The immediate effect on the structural dynamics of the wing, is that, the wing motion is governed by a differential equation with time varying coefficients. The study of this concept of a time varying torsional stiffness, made possible by the use of active materials and adaptive spars, in the dynamic aeroelastic behavior of an adaptable airfoil is performed here. Another type of aeroelastic problem of an adaptive structure that is investigated here, is the shape control of an adaptive bump situated on the leading edge of an airfoil. Such a bump is useful in achieving flow separation control for lateral directional maneuverability of the aircraft. Since actuators are being used to create this bump on the wing surface, the energy required to do so needs to be minimized. The adverse pressure drag as a result of this bump needs to be controlled so that the loss in lift over the wing is made minimal. The design of such a "spoiler bump" on the surface of the airfoil is an optimization problem of maximizing pressure drag due to flow separation while minimizing the loss in lift and energy required to deform the bump. One neural network is trained using the CFD code FLUENT to
Generator dynamics in aeroelastic analysis and simulations
Energy Technology Data Exchange (ETDEWEB)
Larsen, T.J.; Hansen, M.H.; Iov, F.
2003-05-01
This report contains a description of a dynamic model for a doubly-fed induction generator implemented in the aeroelastic code HAWC. The model has physical input parameters (resistance, reactance etc.) and input variables (stator and rotor voltage and rotor speed). The model can be used to simulate the generator torque as well as the rotor and stator currents, active and reactive power. A perturbation method has been used to reduce the original generator model equations to a set of equations which can be solved with the same time steps as a typical aeroelastic code. The method is used to separate the fast transients of the model from the slow variations and deduce a reduced order expression for the slow part. Dynamic effects of the first order terms in the model as well as the influence on drive train eigenfrequencies and damping has been investigated. Load response during time simulation of wind turbine response have been compared to simulations with a linear static generator model originally implemented i HAWC. A 2 MW turbine has been modelled in the aeroelastic code HAWC. When using the new dynamic generator model there is an interesting coupling between the generator dynamics and a global turbine vibration mode at 4.5 Hz, which only occurs when a dynamic formulation of the generator equations is applied. This frequency can especially be seen in the electrical power of the generator and the rotational speed of the generator, but also as torque variations in the drive train. (au)
Aeroelastic Tailoring of a Plate Wing with Functionally Graded Materials
Dunning, Peter D.; Stanford, Bret K.; Kim, H. Alicia; Jutte, Christine V.
2014-01-01
This work explores the use of functionally graded materials for the aeroelastic tailoring of a metallic cantilevered plate-like wing. Pareto trade-off curves between dynamic stability (flutter) and static aeroelastic stresses are obtained for a variety of grading strategies. A key comparison is between the effectiveness of material grading, geometric grading (i.e., plate thickness variations), and using both simultaneously. The introduction of material grading does, in some cases, improve the aeroelastic performance. This improvement, and the physical mechanism upon which it is based, depends on numerous factors: the two sets of metallic material parameters used for grading, the sweep of the plate, the aspect ratio of the plate, and whether the material is graded continuously or discretely.
Chaotic Patterns in Aeroelastic Signals
Directory of Open Access Journals (Sweden)
F. D. Marques
2009-01-01
patterns. With the reconstructed state spaces, qualitative analyses may be done, and the attractors evolutions with parametric variation are presented. Overall results reveal complex system dynamics associated with highly separated flow effects together with nonlinear coupling between aeroelastic modes. Bifurcations to the nonlinear aeroelastic system are observed for two investigations, that is, considering oscillations-induced aeroelastic evolutions with varying freestream speed, and aeroelastic evolutions at constant freestream speed and varying oscillations. Finally, Lyapunov exponent calculation is proceeded in order to infer on chaotic behavior. Poincaré mappings also suggest bifurcations and chaos, reinforced by the attainment of maximum positive Lyapunov exponents.
Energy Technology Data Exchange (ETDEWEB)
Visser, B. [Stork Product Eng., Amsterdam (Netherlands)
1996-09-01
To support the discussion on aeroelastic codes, a description of the code FLEXLAST was given and experiences within benchmarks and measurement programmes were summarized. The code FLEXLAST has been developed since 1982 at Stork Product Engineering (SPE). Since 1992 FLEXLAST has been used by Dutch industries for wind turbine and rotor design. Based on the comparison with measurements, it can be concluded that the main shortcomings of wind turbine modelling lie in the field of aerodynamics, wind field and wake modelling. (au)
Analysis of operational limit of an aircraft: An aeroelastic approach
Hasan, Md. Mehedi; Hassan, M. D. Mehedi; Sarrowar, S. M. Bayazid; Faisal, Kh. Md.; Ahmed, Sheikh Reaz, Dr.
2017-06-01
In classical theory of elasticity, external loading acting on the body is independent of deformation of the body. But, in aeroelasticity, aerodynamic forces depend on the attitude of the body relative to the flow. Aircraft's are subjected to a range of static loads resulting from equilibrium or steady flight maneuvers such as coordinated level turn, steady pitch and bank rate, steady and level flight. Interaction of these loads with elastic forces of aircraft structure creates some aeroelastic phenomena. In this paper, we have summarized recent developments in the area of aeroelasticity. A numerical approach has been applied for finding divergence speed, a static aeroelastic phenomena, of a typical aircraft. This paper also involves graphical representations of constraints on load factor and bank angle during different steady flight maneuvers taking flexibility into account and comparing it with the value without flexibility. Effect of wing skin thickness, spar web thickness and position of flexural axis of wing on this divergence speed as well as load factor and bank angle has also been observed using MATLAB.
Adaptive neural control of aeroelastic response
Lichtenwalner, Peter F.; Little, Gerald R.; Scott, Robert C.
1996-05-01
The Adaptive Neural Control of Aeroelastic Response (ANCAR) program is a joint research and development effort conducted by McDonnell Douglas Aerospace (MDA) and the National Aeronautics and Space Administration, Langley Research Center (NASA LaRC) under a Memorandum of Agreement (MOA). The purpose of the MOA is to cooperatively develop the smart structure technologies necessary for alleviating undesirable vibration and aeroelastic response associated with highly flexible structures. Adaptive control can reduce aeroelastic response associated with buffet and atmospheric turbulence, it can increase flutter margins, and it may be able to reduce response associated with nonlinear phenomenon like limit cycle oscillations. By reducing vibration levels and loads, aircraft structures can have lower acquisition cost, reduced maintenance, and extended lifetimes. Phase I of the ANCAR program involved development and demonstration of a neural network-based semi-adaptive flutter suppression system which used a neural network for scheduling control laws as a function of Mach number and dynamic pressure. This controller was tested along with a robust fixed-gain control law in NASA's Transonic Dynamics Tunnel (TDT) utilizing the Benchmark Active Controls Testing (BACT) wing. During Phase II, a fully adaptive on-line learning neural network control system has been developed for flutter suppression which will be tested in 1996. This paper presents the results of Phase I testing as well as the development progress of Phase II.
Recent advance in nonlinear aeroelastic analysis and control of the aircraft
Directory of Open Access Journals (Sweden)
Xiang Jinwu
2014-02-01
Full Text Available A review on the recent advance in nonlinear aeroelasticity of the aircraft is presented in this paper. The nonlinear aeroelastic problems are divided into three types based on different research objects, namely the two dimensional airfoil, the wing, and the full aircraft. Different nonlinearities encountered in aeroelastic systems are discussed firstly, where the emphases is placed on new nonlinear model to describe tested nonlinear relationship. Research techniques, especially new theoretical methods and aeroelastic flutter control methods are investigated in detail. The route to chaos and the cause of chaotic motion of two-dimensional aeroelastic system are summarized. Various structural modeling methods for the high-aspect-ratio wing with geometric nonlinearity are discussed. Accordingly, aerodynamic modeling approaches have been developed for the aeroelastic modeling of nonlinear high-aspect-ratio wings. Nonlinear aeroelasticity about high-altitude long-endurance (HALE and fight aircrafts are studied separately. Finally, conclusions and the challenges of the development in nonlinear aeroelasticity are concluded. Nonlinear aeroelastic problems of morphing wing, energy harvesting, and flapping aircrafts are proposed as new directions in the future.
STATIC AND DYNAMIC IN VITRO TEST OF BIOACTIVITY OF GLASS CERAMICS
Directory of Open Access Journals (Sweden)
JANA KOZÁNKOVÁ
2011-06-01
Full Text Available The bioactivity of glass ceramics from Li2O–SiO2–CaO–P2O5–CaF2 system, with different amount of fluorapatite expressed as P2O5 content, has been tested in vitro under static and dynamic regime. The paper reports the results of bioactivity test of glass ceramics in static and dynamic regime. XRD, SEM and EPMA analysis were used to characterise the sample as well as to detect the presence of new phase onto the surface of glass ceramics. The bioactivity, as demonstrated by the formation of new apatite layer, depends on P2O5 content and testing regime. In static regime, one can observe a fine microstructure of hydroxyapatite layer on the surface on glass ceramics samples. In dynamic regime, the formation rate of this layer seems to be retarded in comparison with that of static regime.
New aeroelastic studies for a morphing wing
Directory of Open Access Journals (Sweden)
Ruxandra Mihaela BOTEZ*
2012-06-01
Full Text Available For this study, the upper surface of a rectangular finite aspect ratio wing, with a laminar airfoil cross-section, was made of a carbon-Kevlar composite material flexible skin. This flexible skin was morphed by use of Shape Memory Alloy actuators for 35 test cases characterized by combinations of Mach numbers, Reynolds numbers and angles of attack. The Mach numbers varied from 0.2 to 0.3 and the angles of attack ranged between -1° and 2°. The optimized airfoils were determined by use of the CFD XFoil code. The purpose of this aeroelastic study was to determine the flutter conditions to be avoided during wind tunnel tests. These studies show that aeroelastic instabilities for the morphing configurations considered appeared at Mach number 0.55, which was higher than the wind tunnel Mach number limit speed of 0.3. The wind tunnel tests could thus be performed safely in the 6’×9’ wind tunnel at the Institute for Aerospace Research at the National Research Council Canada (IAR/NRC, where the new aeroelastic studies, applied on morphing wings, were validated.
STATIC TEST COMPACTION AS A MINIMUM COVERING PROBLEM
African Journals Online (AJOL)
DEPT OF AGRICULTURAL ENGINEERING
Department of Computer Engineering,. Kwame Nkrumah University of Science and technology,. Kumasi, Ghana. ABSTRACT. Large numbers of test stimuli impact on the time and cost of test application. Hence there is the need to keep numbers of test stimuli low while maintaining as high fault coverage as possible. In.
30 CFR 7.104 - Internal static pressure test.
2010-07-01
..., AND APPROVAL OF MINING PRODUCTS TESTING BY APPLICANT OR THIRD PARTY Diesel Power Packages Intended for Use in Areas of Underground Coal Mines Where Permissible Electric Equipment is Required § 7.104...
Unstructed Navier-Stokes Analysis of Wind-Tunnel Aeroelastic Effects on TCA Model 2
Frink, Neal T.; Allison, Dennis O.; Parikh, Paresh C.
1999-01-01
The aim of this work is to demonstrate a simple technique which accounts for aeroelastic deformations experienced by HSR wind-tunnel models within CFD computations. With improved correlations, CFD can become a more effective tool for augmenting the post-test understanding of experimental data. The present technique involves the loose coupling of a low-level structural representation within the ELAPS code, to an unstructured Navier-Stokes flow solver, USM3Dns. The ELAPS model is initially calibrated against bending characteristics of the wind-tunnel model. The strength of this method is that, with a single point calibration of a simple structural representation, the static aeroelastic effects can be accounted for in CFD calculations across a range of test conditions. No prior knowledge of the model deformation during the wind-on test is required. This approach has been successfully applied to the high aspect-ratio planforms of subsonic transports. The current challenge is to adapt the procedure to low aspect-ratio planforms typical of HSR configurations.
Analysis of Static Load Test of a Masonry Arch Bridge
Shi, Jing-xian; Fang, Tian-tian; Luo, Sheng
2018-03-01
In order to know whether the carrying capacity of the masonry arch bridge built in the 1980s on the shipping channel entering and coming out of the factory of a cement company can meet the current requirements of Level II Load of highway, through the equivalent load distribution of the test vehicle according to the current design specifications, this paper conducted the load test, evaluated the bearing capacity of the in-service stone arch bridge, and made theoretical analysis combined with Midas Civil. The results showed that under the most unfavorable load conditions the measured strain and deflection of the test sections were less than the calculated values, the bridge was in the elastic stage under the design load; the structural strength and stiffness of the bridge had a certain degree of prosperity, and under the in the current conditions of Level II load of highway, the bridge structure was in a safe state.
Mesoscopic analyses of porous concrete under static compression and drop weight impact tests
DEFF Research Database (Denmark)
Agar Ozbek, A.S.; Pedersen, R.R.; Weerheijm, J.
2008-01-01
was considered as a four-phase material incorporating aggregates, bulk cement paste, interfacial transition zones and meso-size air pores. The stress-displacement relations obtained from static compression tests, the stress values, and the corresponding damage levels provided by the drop weight impact tests were......The failure process in highly porous concrete was analyzed experimentally and numerically. A triaxial visco-plastic damage model and a mesoscale representation of the material composition were considered to reproduce static compression and drop weight impact tests. In the mesoscopic model, concrete...
Comparison of the outcomes of dynamic/static tests and palpation tests in TMD-pain patients.
Osiewicz, M A; Manfredini, D; Loster, B W; van Selms, M K A; Lobbezoo, F
2018-03-01
In addition to palpation tests, dynamic/static tests have been proposed to complement temporomandibular disorders (TMD) patients' evaluation in the clinical setting. The aim of this study was to assess the intra- and inter-observer reliability of the palpation tests and of the dynamic/static tests, and to determine whether those tests would yield comparable outcomes in terms of pain diagnoses. Ninety-eight (N = 98) consecutive adult patients were examined during 2 clinical sessions by 2 independent examiners, based on muscle and joint palpation techniques described in the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). They also underwent dynamic/static tests. The intra-observer reliability of palpation tests was generally poor, with fair-to-good to excellent ICC values only for the superior masseter and intra-oral sites. The inter-observer reliability of palpation was fair-to-good for muscles, but it was poor for the TMJ lateral pole. Both intra- and inter-observer reliability for the dynamic/static tests varied from fair-to-good to excellent. The intra-observer reliability for muscle pain diagnoses based on palpation tests was between poor and fair-to-good, whereas the inter-observer reliability was excellent. The intra-observer reliability for pain diagnoses based on dynamic/static tests was fair-to-good, and the inter-observer reliability varied from fair-to-good to excellent. Some features of the dynamic/static tests make them potentially more useful than palpation tests for selected clinical purposes, such as discriminating between joint and muscle pain as well as monitoring symptoms course. Thus, findings from this investigation suggest that both tests should be included in the TMD diagnostic algorithms. © 2018 John Wiley & Sons Ltd.
The Aluminum Ship Evaluation Model (ASEM) Static Test Results
1983-12-01
At each load frame, one starboard hydraulic acuator or jack and one or two keel jacks (coupled with closed-loop, feedback system load cells) were used...zero, system lock and unlock, and lateral offset. Each test was performed enough times to establish repeatable linear strain response with load. A...to obtain the strain readings. The linearity in load versus strain response and, thus, the basic stress sensitivities (numbers of pounds per square
Pilot Study: Foam Wedge Chin Support Static Tolerance Testing
2017-10-24
Government. The fact that the Government formulated or supplied the drawings, specifications, or other data does not license the holder or any other...regarding the comfort, fit, and positive benefits that could potentially come from the use of the foam wedge to mitigate neck pain. Overall, testing showed... benefit to pilots that choose to use the foam wedge, and therefore feel that the device should be made available to aviators. From the results of this
Murrow, H. N.
1981-01-01
Results from flight tests of the ARW-1 research wing are presented. Preliminary loads data and experiences with the active control system for flutter suppression are included along with comparative results of test and prediction for the flutter boundary of the supercritical research wing and on performance of the flutter suppression system. The status of the ARW-2 research wing is given.
THERMAL VACUUM TEST OF ORBITAL STATIC MOISTURE-REMOVAL FUEL CELL.
The report presents the results of a thermal vacuum chamber test of an orbital fuel cell of advanced design. The fuel cell package used a static moisture-removal system. The fuel cell , tested in the thermal vacuum chamber at Wright-Patterson AFB, gave satisfactory results. This test constituted the second and final ground qualification of this orbital fuel cell prior to orbital test. (Author)
Generator dynamics in aeroelastic analysis and simulations
DEFF Research Database (Denmark)
Larsen, Torben J.; Hansen, Morten Hartvig; Iov, F.
2003-01-01
This report contains a description of a dynamic model for a doubly-fed induction generator. The model has physical input parameters (voltage, resistance, reactance etc.) and can be used to calculate rotor and stator currents, hence active and reactivepower. A perturbation method has been used...... to reduce the original generator model equations to a set of equations which can be solved with the same time steps as a typical aeroelastic code. The method is used to separate the fast transients of the modelfrom the slow variations and deduce a reduced order expression for the slow part. Dynamic effects...... of the first order terms in the model as well as the influence on drive train eigenfrequencies and damping has been investigated. Load response during timesimulation of wind turbine response have been compared to simulations with a traditional static generator model based entirely on the slip angle. A 2 MW...
Static Pull Testing of a New Type of Large Deformation Cable with Constant Resistance
Directory of Open Access Journals (Sweden)
Zhigang Tao
2017-01-01
Full Text Available A new type of energy-absorbing cable, Constant-Resistance Large Deformation cable (CRLD cable with three different specifications, has been recently developed and tested. An effective cable should occupy the ability of absorbing deformation energy from these geodisaster loads and additionally must be able to yield with the sliding mass movements and plastic deformation over large distances at high displacement rates. The new cable mainly consists of constant-resistance casing tube and frictional cone unit that transfers the load from the slope. When experiencing a static or dynamic load and especially the load exceeding the constant resistance force (CR-F, a static friction force derived from the movement of frictional cone unit in casing tube of CRLD cable, the frictional cone unit will move in the casing tube along the axis and absorb deformation energy, accordingly. In order to assess the performance of three different specified cables in situ, a series of field static pull tests have been performed. The results showed that the first type of CRLD cable can yield 2000 mm displacement while acting 850 kN static pull load, which is superior to that of other two types, analyzing based on the length of the displacement and the level of static pull load.
Level-Set Topology Optimization with Aeroelastic Constraints
Dunning, Peter D.; Stanford, Bret K.; Kim, H. Alicia
2015-01-01
Level-set topology optimization is used to design a wing considering skin buckling under static aeroelastic trim loading, as well as dynamic aeroelastic stability (flutter). The level-set function is defined over the entire 3D volume of a transport aircraft wing box. Therefore, the approach is not limited by any predefined structure and can explore novel configurations. The Sequential Linear Programming (SLP) level-set method is used to solve the constrained optimization problems. The proposed method is demonstrated using three problems with mass, linear buckling and flutter objective and/or constraints. A constraint aggregation method is used to handle multiple buckling constraints in the wing skins. A continuous flutter constraint formulation is used to handle difficulties arising from discontinuities in the design space caused by a switching of the critical flutter mode.
Aeroelastic Wingbox Stiffener Topology Optimization
Stanford, Bret K.
2017-01-01
This work considers an aeroelastic wingbox model seeded with run-out blade stiffeners along the skins. Topology optimization is conducted within the shell webs of the stiffeners, in order to add cutouts and holes for mass reduction. This optimization is done with a global-local approach in order to moderate the computational cost: aeroelastic loads are computed at the wing-level, but the topology and sizing optimization is conducted at the panel-level. Each panel is optimized separately under stress, buckling, and adjacency constraints, and periodically reassembled to update the trimmed aeroelastic loads. The resulting topology is baselined against a design with standard full-depth solid stiffener blades, and found to weigh 7.43% less.
In-flight and ground testing of single event upset sensitivity in static RAMs
International Nuclear Information System (INIS)
Johansson, K.; Dyreklev, P.; Granbom, B.; Calvet, C.; Fourtine, S.; Feuillatre, O.
1998-01-01
This paper presents the results from in-flight measurements of single event upsets (SEU) in static random access memories (SRAM) caused by the atmospheric radiation environment at aircraft altitudes. The memory devices were carried on commercial airlines at high altitude and mainly high latitudes. The SEUs were monitored by a Component Upset Test Equipment (CUTE), designed for this experiment. The in flight results are compared to ground based testing with neutrons from three different sources
Testing Static Trade-off Against Pecking Order Models of Capital Structure
Lakshmi Shyam-Sunder; Stewart C. Myers
1994-01-01
This paper tests traditional capital structure models against the alternative of a pecking order model of corporate financing. The basic pecking order model, which predicts external debt financing driven by the internal financial deficit, has much greater explanatory power than a static trade-off model which predicts that each firm adjusts toward an optimal debt ratio. We show that the power of some usual tests of the trade-off model is virtually nil. We question whether the available empiric...
Triboelectret-based aeroelastic flutter energy harvesters
Perez, Matthias; Boisseau, Sebastien; Geisler, Matthias; Despesse, Ghislain; Reboud, Jean Luc
2016-11-01
This paper highlights some experimental results on several electrostatic membranes tested in a wind tunnel between 0 and 20m.s-1 for airflow energy harvesting. The main idea is to use the aeroelastic behavior of thin flexible films to induce simultaneously the capacitance variations and the polarization required by the triboelectric/electrostatic conversion. This technology provides thin and flexible devices and avoids the issue of electrets discharge. Our prototypes (energy harvesting chain, we have used a wireless sensor with temperature and acceleration measures coupled to a low power transmission (Bluetooth Low Energy) with reception on a smartphone.
Definition of the linearity loss of the surface temperature in static tensile tests
Directory of Open Access Journals (Sweden)
A. Risitano
2014-10-01
Full Text Available Static tensile tests on material for mechanical constructions have pointed out the linearity loss of the surface temperature with the application of load. This phenomenon is due to the heat generation caused by the local microplasticizations which carry the material to deviate from its completely thermoelastic behavior,. The identification of the static load which determines the loss of linearity of the temperature under stress, becomes extremely important to define a first dynamic characterization of the material. The temperature variations that can be recorded during the static test are often very limited (a few tenths of degree for every 100 MPa in steels and they require the use of special sensors able to measure very low temperature variations. The experience acquired in such analysis highlighted that, dealing with highly accurate sensors or with particular materials, the identification of the first linearity loss (often by eye in the temperature curves, can be influenced by the sensibility of the investigator himself and can lead to incorrect estimates. The aim of this work is to validate the above mentioned observations on different steels, by applying the autocorrelation function to the data collected during the application of a static load. This, in order to make the results of the thermal analysis free from the sensitivity of the operator and to make the results as objective as possible, for defining the closest time of the linearity loss in the temperature-time function.
Evaluation of feasibility of static tests applied to Küre VMS ore deposits
Demirel, Cansu; Çelik Balci, Nurgül; Şeref Sönmez, M.
2015-04-01
Küre volcanogenic massive sulfide (VMS) ore deposits have been mined for its copper content for over centuries. However, there is no published data on AMD around Küre VMS ore deposits. This study investigates the sources of acid producing mechanisms in Küre, using field and laboratorial approaches. Geochemical static tests to predict AMD generation are widely applied to mining sites for assessing potential environmental consequences. However, there are well known limitations of these methods particularly resulting from assumptions used for calculations. To test the feasibility of the methods to predict potential of AMD generation of Küre (VMS) copper deposits, for the first time, acid production and neutralization potential of various mine wastes of Küre (VMS) copper deposits were determined. To test our static test results, in situ and laboratory geochemical data were also obtained from the groundwater discharges from Bakibaba underground mining tunnels. Feasibility study showed that, despite a few inconsistencies, static tests were suitable for predicting generation of AMD around Küre copper mining site and reflected well the site conditions. The current study revealed that pulp density, defined as solid/liquid ratio and used for static tests, is an important limiting factor to predict reliable data for AMD generation. In this study, we also determined surface waters affected by AMD are predicted to have a pH value between 3 and 5, with an average of pH 4. Excessive concentrations of manganese, copper, cobalt and sulfate are also noted with considerable amounts of iron and zinc, which can reach to toxic levels. Moreover, iron and zinc were found to be the controlling the fate of metals by precipitation and co-precipitation, due to their relatively depleted concentrations at redox shifting zones. Key words: Küre pyritic copper ore, Bakibaba mining tunnels, volcanogenic massive sulfide ore deposits, acid production potential, neutralization potential
Suzuki, Makoto; Fujisawa, Hiroyuki; Machida, Yooichiro; Minakata, Shin
2013-01-01
[Purpose] The purpose of this study was to analyze the relationship between results of the Berg Balance Scale (BBS) and Static Balance Test (SBT) in hemiplegic patients with stroke. [Subjects] The subjects were 39 hemiplegic patients (25 men, 14 women; mean age, 69.4 ? 11.0?years) with stroke that had occurred within the preceding 6 months and who had good understanding of verbal instructions. [Methods] The SBT consists of five posture-holding tasks (sitting, stride standing, close standing, ...
Safety prediction for basic components of safety-critical software based on static testing
International Nuclear Information System (INIS)
Son, H.S.; Seong, P.H.
2000-01-01
The purpose of this work is to develop a safety prediction method, with which we can predict the risk of software components based on static testing results at the early development stage. The predictive model combines the major factor with the quality factor for the components, which are calculated based on the measures proposed in this work. The application to a safety-critical software system demonstrates the feasibility of the safety prediction method. (authors)
Safety prediction for basic components of safety critical software based on static testing
International Nuclear Information System (INIS)
Son, H.S.; Seong, P.H.
2001-01-01
The purpose of this work is to develop a safety prediction method, with which we can predict the risk of software components based on static testing results at the early development stage. The predictive model combines the major factor with the quality factor for the components, both of which are calculated based on the measures proposed in this work. The application to a safety-critical software system demonstrates the feasibility of the safety prediction method. (authors)
Gravo-Aeroelastic Scaling for Extreme-Scale Wind Turbines
Energy Technology Data Exchange (ETDEWEB)
Fingersh, Lee J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Loth, Eric [University of Virginia; Kaminski, Meghan [University of Virginia; Qin, Chao [University of Virginia; Griffith, D. Todd [Sandia National Laboratories
2017-06-09
A scaling methodology is described in the present paper for extreme-scale wind turbines (rated at 10 MW or more) that allow their sub-scale turbines to capture their key blade dynamics and aeroelastic deflections. For extreme-scale turbines, such deflections and dynamics can be substantial and are primarily driven by centrifugal, thrust and gravity forces as well as the net torque. Each of these are in turn a function of various wind conditions, including turbulence levels that cause shear, veer, and gust loads. The 13.2 MW rated SNL100-03 rotor design, having a blade length of 100-meters, is herein scaled to the CART3 wind turbine at NREL using 25% geometric scaling and blade mass and wind speed scaled by gravo-aeroelastic constraints. In order to mimic the ultralight structure on the advanced concept extreme-scale design the scaling results indicate that the gravo-aeroelastically scaled blades for the CART3 are be three times lighter and 25% longer than the current CART3 blades. A benefit of this scaling approach is that the scaled wind speeds needed for testing are reduced (in this case by a factor of two), allowing testing under extreme gust conditions to be much more easily achieved. Most importantly, this scaling approach can investigate extreme-scale concepts including dynamic behaviors and aeroelastic deflections (including flutter) at an extremely small fraction of the full-scale cost.
Aeroelastic Modeling of a Nozzle Startup Transient
Wang, Ten-See; Zhao, Xiang; Zhang, Sijun; Chen, Yen-Sen
2014-01-01
Lateral nozzle forces are known to cause severe structural damage to any new rocket engine in development during test. While three-dimensional, transient, turbulent, chemically reacting computational fluid dynamics methodology has been demonstrated to capture major side load physics with rigid nozzles, hot-fire tests often show nozzle structure deformation during major side load events, leading to structural damages if structural strengthening measures were not taken. The modeling picture is incomplete without the capability to address the two-way responses between the structure and fluid. The objective of this study is to develop a tightly coupled aeroelastic modeling algorithm by implementing the necessary structural dynamics component into an anchored computational fluid dynamics methodology. The computational fluid dynamics component is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, while the computational structural dynamics component is developed under the framework of modal analysis. Transient aeroelastic nozzle startup analyses at sea level were performed, and the computed transient nozzle fluid-structure interaction physics presented,
Radovcich, N. A.
1984-01-01
The design experience associated with a benchmark aeroelastic design of an out of production transport aircraft is discussed. Current work being performed on a high aspect ratio wing design is reported. The Preliminary Aeroelastic Design of Structures (PADS) system is briefly summarized and some operational aspects of generating the design in an automated aeroelastic design environment are discussed.
Aeroelastic Tailoring of Transport Wings Including Transonic Flutter Constraints
Stanford, Bret K.; Wieseman, Carol D.; Jutte, Christine V.
2015-01-01
Several minimum-mass optimization problems are solved to evaluate the effectiveness of a variety of novel tailoring schemes for subsonic transport wings. Aeroelastic stress and panel buckling constraints are imposed across several trimmed static maneuver loads, in addition to a transonic flutter margin constraint, captured with aerodynamic influence coefficient-based tools. Tailoring with metallic thickness variations, functionally graded materials, balanced or unbalanced composite laminates, curvilinear tow steering, and distributed trailing edge control effectors are all found to provide reductions in structural wing mass with varying degrees of success. The question as to whether this wing mass reduction will offset the increased manufacturing cost is left unresolved for each case.
Kotani, Y; Cunningham, B W; Parker, L M; Kanayama, M; McAfee, P C
1999-07-15
A mechanical testing standard for anterior thoracolumbar instrumentation systems was introduced, using a synthetic model. Twelve recent instrumentation systems were tested in static and fatigue modes. To establish the testing standard for anterior thoracolumbar instrumentation systems using a synthetic model and to evaluate the static and fatigue biomechanical properties of 12 anterior thoracolumbar instrumentation systems. Although numerous studies have been performed to evaluate the biomechanics of anterior spinal instrumentation using a cadaveric or animal tissue, problems of specimen variation, lack of reproducibility, and inability to perform fatigue testing have been pointed out. In no studies has a precise synthetic testing standard for anterior thoracolumbar instrumentation systems been described. An ultra-high-molecular-weight polyethylene cylinder was designed according to the anatomic dimensions of the vertebral body. Two cylinders spanned by spinal instrumentation simulated a total corpectomy defect, and a compressive lateral bending load was applied. The instrumentation assembly was precisely standardized. The static destructive and fatigue tests up to 2 million cycles at three load levels were conducted, followed by the failure mode analysis. Twelve anterior instrumentation systems, consisting of five plate and seven rod systems were compared in stiffness, bending strength, and cycles to failure. Static and fatigue test parameters both demonstrated highly significant differences between devices. The stiffness ranged from 280.5 kN/m in the Synthes plate (Synthes, Paoli, PA) to 67.9 kN/m in the Z-plate ATL (SofamorDanek, Memphis, TN). The Synthes plate and Kaneda SR titanium (AcroMed, Cleveland, OH) formed the highest subset in bending strength of 1516.1 N and 1209.9 N, respectively, whereas the Z-plate showed the lowest value of 407.3 N. There were no substantial differences between plate and rod devices. In fatigue, only three systems: Synthes plate
Arroyo, B.; Álvarez, J. A.; Lacalle, R.; González, P.; Gutiérrez-Solana, F.
2017-12-01
In this paper, the response of three medium and high-strength steels to hydrogen embrittlement is analyzed by means of the quasi-non-destructive test known as the Small Punch Test (SPT). SPT tests on notched specimens under static load are carried out, applying Lacaclle’s methodology to estimate the fracture toughness for crack initiation, comparing the results to KIEAC fracture toughness obtained from C(T) precracked specimens tested in the same environment; SPT showed good correlation to standard tests. A novel expression was proposed to define the parameter KIEAC-SP as the suitable one to estimate the fracture toughness for crack initiation in hydrogen embrittlement conditions by Small Punch means, obtaining good accuracy in its estimations. Finally, Slow Rate Small Punch Tests (SRSPT) are proposed as a more efficient alternative, introducing an order of magnitude for the adequate rate to be employed.
FUN3D Analyses in Support of the Second Aeroelastic Prediction Workshop
Chwalowski, Pawel; Heeg, Jennifer
2016-01-01
This paper presents the computational aeroelastic results generated in support of the second Aeroelastic Prediction Workshop for the Benchmark Supercritical Wing (BSCW) configurations and compares them to the experimental data. The computational results are obtained using FUN3D, an unstructured grid Reynolds- Averaged Navier-Stokes solver developed at NASA Langley Research Center. The analysis results include aerodynamic coefficients and surface pressures obtained for steady-state, static aeroelastic equilibrium, and unsteady flow due to a pitching wing or flutter prediction. Frequency response functions of the pressure coefficients with respect to the angular displacement are computed and compared with the experimental data. The effects of spatial and temporal convergence on the computational results are examined.
The influence of turbulence on the aero-elastic instability of wind turbines
DEFF Research Database (Denmark)
Zhang, Zili; Nielsen, Søren R.K.
2014-01-01
Modern multi-megawatt wind turbines are designed with longer and slender blades using new composite materials and advanced fabrication methods. The trend towards lighter and more flexible blades may lead to aeroelastic instability of wind turbines under certain circumstances, thus resulting...... aerodynamic damping. A 13-degree-of-freedom (13-DOF) wind turbine model is developed using Euler-Lagrange equations, which includes the couplings of the tower-blade-drivetrain vibration, the quasi-static aeroelasticity and a collective pitch controller. Numerical simulations are carried out using data...... turbine shifts from a stable state into an instable state, is determined in different cases. Results show that turbulence intensity has significant influence on the aeroelastic stability of high-performance wind turbines operating close to stall, and the stability of the wind turbine might be changed due...
Erickson, Gary E.
2013-01-01
A video-based photogrammetric model deformation system was established as a dedicated optical measurement technique at supersonic speeds in the NASA Langley Research Center Unitary Plan Wind Tunnel. This system was used to measure the wing twist due to aerodynamic loads of two supersonic commercial transport airplane models with identical outer mold lines but different aeroelastic properties. One model featured wings with deflectable leading- and trailing-edge flaps and internal channels to accommodate static pressure tube instrumentation. The wings of the second model were of single-piece construction without flaps or internal channels. The testing was performed at Mach numbers from 1.6 to 2.7, unit Reynolds numbers of 1.0 million to 5.0 million, and angles of attack from -4 degrees to +10 degrees. The video model deformation system quantified the wing aeroelastic response to changes in the Mach number, Reynolds number concurrent with dynamic pressure, and angle of attack and effectively captured the differences in the wing twist characteristics between the two test articles.
Non-Contacting Finger Seals Static Performance Test Results at Ambient and High Temperatures
Proctor, Margaret P.
2016-01-01
The non-contacting finger seal is an advanced seal concept with potential to reduce specific fuel consumption in gas turbine engines by 2 to 3 with little to no wear of the seal or rotor. Static performance tests and bind-up tests of eight different non-contacting finger seal configurations were conducted in air at pressure differentials up to 689.4 kPa and temperatures up to 922 K. Four of the seals tested were designed to have lift pads concentric to a herringbone-grooved rotor which generates hydrodynamic lift when rotating. The remaining seals were tested with a smooth rotor; one seal had a circumferential taper and one had an axial taper on the lift pad inner diameter to create hydrodynamic lift during rotation. The effects of the aft finger axial thickness and of the forward finger inner diameter on leakage performance were investigated as well and compared to analytical predictions.
Experimental test of static and dynamic characteristics of tilting-pad thrust bearings
Directory of Open Access Journals (Sweden)
Annan Guo
2015-07-01
Full Text Available The axial vibration in turbine machine has attracted more and more interest. Tilting-pad thrust bearings are widely used in turbine machines to support the axial load. The dynamic properties generated by oil film of the thrust pad have important effects on the axial vibration of the rotor-bearing system. It is necessary to develop the method to test the dynamic characteristics of thrust bearings. A new rig has been developed. The facility allows a complete set of bearing operating parameters to be measured. Parameters measured include oil temperatures, oil-film thickness, and pressure. The static load and dynamic load can be added on the thrust bearing in the vertical direction at the same time. The relative and absolute displacement vibrations of the test experimental bearing with the changes of dynamic force are measured, and the dynamic characteristics of the test bearing are obtained. The experimental results show clearly that the operating conditions influence largely on the pad static and dynamic characteristics.
Standard test method for static leaching of monolithic waste forms for disposal of radioactive waste
American Society for Testing and Materials. Philadelphia
2010-01-01
1.1 This test method provides a measure of the chemical durability of a simulated or radioactive monolithic waste form, such as a glass, ceramic, cement (grout), or cermet, in a test solution at temperatures <100°C under low specimen surface- area-to-leachant volume (S/V) ratio conditions. 1.2 This test method can be used to characterize the dissolution or leaching behaviors of various simulated or radioactive waste forms in various leachants under the specific conditions of the test based on analysis of the test solution. Data from this test are used to calculate normalized elemental mass loss values from specimens exposed to aqueous solutions at temperatures <100°C. 1.3 The test is conducted under static conditions in a constant solution volume and at a constant temperature. The reactivity of the test specimen is determined from the amounts of components released and accumulated in the solution over the test duration. A wide range of test conditions can be used to study material behavior, includin...
Low-speed static and dynamic force tests of a generic supersonic cruise fighter configuration
Hahne, David E.
1989-01-01
Static and dynamic force tests of a generic fighter configuration designed for sustained supersonic flight were conducted in the Langley 30- by 60-foot tunnel. The baseline configuration had a 65 deg arrow wing, twin wing mounted vertical tails and a canard. Results showed that control was available up to C sub L,max (maximum lift coefficient) from aerodynamic controls about all axes but control in the pitch and yaw axes decreased rapidly in the post-stall angle-of-attack region. The baseline configuration showed stable lateral-directional characteristics at low angles of attack but directional stability occurred near alpha = 25 deg as the wing shielded the vertical tails. The configuration showed positive effective dihedral throughout the test angle-of-attack range. Forced oscillation tests indicated that the baseline configuration had stable damping characteristics about the lateral-directional axes.
Aeroelastic Airworthiness Assesment of the Adaptive Compliant Trailing Edge Flaps
Herrera, Claudia Y.; Spivey, Natalie D.; Lung, Shun-fat; Ervin, Gregory; Flick, Peter
2015-01-01
The Adaptive Compliant Trailing Edge (ACTE) demonstrator is a joint task under the National Aeronautics and Space Administration Environmentally Responsible Aviation Project in partnership with the Air Force Research Laboratory and FlexSys, Inc. (Ann Arbor, Michigan). The project goal is to develop advanced technologies that enable environmentally friendly aircraft, such as adaptive compliant technologies. The ACTE demonstrator flight-test program encompassed replacing the Fowler flaps on the SubsoniC Aircraft Testbed, a modified Gulfstream III (Gulfstream Aerospace, Savannah, Georgia) aircraft, with control surfaces developed by FlexSys. The control surfaces developed by FlexSys are a pair of uniquely-designed unconventional flaps to be used as lifting surfaces during flight-testing to validate their structural effectiveness. The unconventional flaps required a multidisciplinary airworthiness assessment to prove they could withstand the prescribed flight envelope. Several challenges were posed due to the large deflections experienced by the structure, requiring non-linear analysis methods. The aeroelastic assessment necessitated both conventional and extensive testing and analysis methods. A series of ground vibration tests (GVTs) were conducted to provide modal characteristics to validate and update finite element models (FEMs) used for the flutter analyses for a subset of the various flight configurations. Numerous FEMs were developed using data from FlexSys and the ground tests. The flap FEMs were then attached to the aircraft model to generate a combined FEM that could be analyzed for aeroelastic instabilities. The aeroelastic analysis results showed the combined system of aircraft and flaps were predicted to have the required flutter margin to successfully demonstrate the adaptive compliant technology. This paper documents the details of the aeroelastic airworthiness assessment described, including the ground testing and analyses, and subsequent flight-testing
Kvaternik, Raymond G.; Juang, Jer-Nan; Bennett, Richard L.
2000-01-01
The Aeroelasticity Branch at NASA Langley Research Center has a long and substantive history of tiltrotor aeroelastic research. That research has included a broad range of experimental investigations in the Langley Transonic Dynamics Tunnel (TDT) using a variety of scale models and the development of essential analyses. Since 1994, the tiltrotor research program has been using a 1/5-scale, semispan aeroelastic model of the V-22 designed and built by Bell Helicopter Textron Inc. (BHTI) in 1981. That model has been refurbished to form a tiltrotor research testbed called the Wing and Rotor Aeroelastic Test System (WRATS) for use in the TDT. In collaboration with BHTI, studies under the current tiltrotor research program are focused on aeroelastic technology areas having the potential for enhancing the commercial and military viability of tiltrotor aircraft. Among the areas being addressed, considerable emphasis is being directed to the evaluation of modern adaptive multi-input multi- output (MIMO) control techniques for active stability augmentation and vibration control of tiltrotor aircraft. As part of this investigation, a predictive control technique known as Generalized Predictive Control (GPC) is being studied to assess its potential for actively controlling the swashplate of tiltrotor aircraft to enhance aeroelastic stability in both helicopter and airplane modes of flight. This paper summarizes the exploratory numerical and experimental studies that were conducted as part of that investigation.
Static Test for a Gravitational Force Coupled to Type 2 YBCO Superconductors
Li, Ning; Noever, David; Robertson, Tony; Koczor, Ron; Brantley, Whitt
1997-01-01
As a Bose condensate, superconductors provide novel conditions for revisiting previously proposed couplings between electromagnetism and gravity. Strong variations in Cooper pair density, large conductivity and low magnetic permeability define superconductive and degenerate condensates without the traditional density limits imposed by the Fermi energy (approx. 10(exp -6) g cc. Recent experiments have reported anomalous weight loss for a test mass suspended above a rotating type II, YBCO superconductor, with the percentage change (0.05 - 2.1 %) independent of the test mass' chemical composition and diamagnetic properties. A variation of 5 parts per 10' was reported above a stationary (non-rotating) superconductor. In experiments using a sensitive gravimeter, bulk YBCO superconductors were stably levitated in a DC magnetic field. Changes in acceleration were measured to be less than 2 parts in 108 of the normal gravitational acceleration. This result puts new limits on the strength and range of the proposed coupling between static superconductors and gravity.
Lyle, Karen H.
2015-01-01
Acceptance of new spacecraft structural architectures and concepts requires validated design methods to minimize the expense involved with technology demonstration via flight-testing. Hypersonic Inflatable Aerodynamic Decelerator (HIAD) architectures are attractive for spacecraft deceleration because they are lightweight, store compactly, and utilize the atmosphere to decelerate a spacecraft during entry. However, designers are hesitant to include these inflatable approaches for large payloads or spacecraft because of the lack of flight validation. This publication summarizes results comparing analytical results with test data for two concepts subjected to representative entry, static loading. The level of agreement and ability to predict the load distribution is considered sufficient to enable analytical predictions to be used in the design process.
Energy Technology Data Exchange (ETDEWEB)
Fuentes Miquel, V. S.; Iglesias Rey, P. L.; Perez Garcia, R.; Martinez Solano, F. J. [Universidad Politecnica de Valencia (Spain)
2003-07-01
The presence of air in water supply systems is, in many cases, unavoidable. The air develops into the pipes due to very different reasons and causes a big number of problems, which can become even catastrophic for the installations. A good solution for avoiding these problems is the use of air valves. Most manufacturers provide the graphic behaviour of their air valves by means of curves representing heal losses vs. air flow through the valve. In the Polytechnic University of Valencia static tests for a big number of these valves have been performed. When comparing the results from these tests with the data provided by the manufactures, important differences have been found. This fact can have dramatic consequences. (Author) 4 refs.
Research in aeroelasticity[Wind turbines
Energy Technology Data Exchange (ETDEWEB)
Bak, C.
2006-05-15
In the Energy Research Project 'Program for Research in Applied Aeroelasticity' (EFP2005), Risoe National Laboratory (Risoe) and the Technical University of Denmark (DTU) have applied and further developed the tools in the aeroelastic design complex. The main results from the project are: 1) Adding a winglet to a wind turbine blade for minimizing the induced drag of the blade led to the biggest increase in power of 1.4%. 2) Transient wind loads during pitch motion are determined using CFD. Compared to the NREL/NASA Ames test, reasonably good agreement is seen. 3) A general method was developed for the determination of 3D angle of attack for rotating blades from either measurements or numerical computations using CFD. 4) A model of the far wake behind wind turbines was developed for stability studies of the tip vortices in the far wake. 5) Investigating the blade root region showed that the power efficiency, CP, locally can be increased significantly beyond the Betz limit, but that the global CP for the rotor cannot exceed the Betz limit. When including tip losses and a minimum blade drag coefficient, a maximum rotor CP in the range of 0.51-0.52 was obtained. 6) A new airfoil family was designed and a 3D airfoil design tool was developed. Compared to the Risoe-B1 family, the new airfoil family showed similar or improved aerodynamic and structural characteristics. 7) Four different airfoils were analyzed to reveal the differences between 2D and 3D CFD. The major conclusions are the dependency of computational results to transition modelling, and the ability of 3D DES calculations to realistically simulate the turbulent wake of an airfoil in stall. 8) The capability of a theory for simulation of Gaussian turbulence driven gust events was demonstrated by emulating a violent shear gust event from a complex site. An asymptotic model for the PDF of the largest excursion from the mean level, during an arbitrary recurrence period, has been derived for a stochastic
Aeroelastic stability analysis of a Darrieus wind turbine
Energy Technology Data Exchange (ETDEWEB)
Popelka, D.
1982-02-01
An aeroelastic stability analysis has been developed for predicting flutter instabilities on vertical axis wind turbines. The analytical model and mathematical formulation of the problem are described as well as the physical mechanism that creates flutter in Darrieus turbines. Theoretical results are compared with measured experimental data from flutter tests of the Sandia 2 Meter turbine. Based on this comparison, the analysis appears to be an adequate design evaluation tool.
Design and Demonstration of a Test-Rig for Static Performance-Studies of Permanent Magnet Couplings
DEFF Research Database (Denmark)
Högberg, Stig; Jensen, Bogi Bech; Bendixen, Flemming Buus
2013-01-01
The design and construction of an easy-to-use test-rig for permanent magnet couplings is presented. Static torque of permanent magnet couplings as a function of angular displacement is measured of permanent magnet couplings through an semi-automated test system. The test-rig is capable of measuring...
Large-Scale Multiobjective Static Test Generation for Web-Based Testing with Integer Programming
Nguyen, M. L.; Hui, Siu Cheung; Fong, A. C. M.
2013-01-01
Web-based testing has become a ubiquitous self-assessment method for online learning. One useful feature that is missing from today's web-based testing systems is the reliable capability to fulfill different assessment requirements of students based on a large-scale question data set. A promising approach for supporting large-scale web-based…
Development, function and test of a static test bench for UHF-RFID ear tags
Directory of Open Access Journals (Sweden)
Felix Adrion
2015-05-01
Full Text Available Ultra-high-frequency radio frequency identification systems (UHF-RFID systems offer multiple application possibilities for animal identification. In a present joint project, UHF transponder ear tags and readers are currently being developed especially for use with cattle and pigs. An automatic test bench was developed for measuring the detection area and signal strength of various transponders, the aim being to enable with this test bench comparison of different types of UHF-transponder ear tags in different orientations to reader antennas. Described in this paper is the constructional development and functionality of the test bench as well as trials to determine reproducibility, influence of two trial parameters and suitability of the test bench for the required purpose. The results demonstrate that the test bench fulfilled all the stipulated requirements and enabled a preliminary selection of suitable types of UHF ear tags for use in practice.
Static and dynamic testing of a damaged post tensioned concrete beam
Directory of Open Access Journals (Sweden)
Limongelli M.P.
2015-01-01
Full Text Available In this paper are reported the results of an experimental campaign carried out on a post tensioned concrete beam with the aim of investigating the possibility to detect early warning signs of deterioration basing on static and/or dynamic tests. The beam was tested in several configurations aimed to reproduce several different phases of the ‘life’ of the beam: the original undamaged state, increasing loss of tension in the post tensioning cables, a strengthening intervention carried out by means of a second tension cable, formation of further cracks on the strengthened beam. Responses of the beam were measured by an extensive set of instruments consisting of accelerometers, inclinometers, displacement transducers, strain gauges and optical fibres. The paper discusses the tests program and the dynamic characterization of the beam in the different damage scenarios. The modal properties of the beam in the different phases were recovered basing on the responses recorded on the beam during sine-sweep and impact hammer tests. The variation of the first modal frequency was studied to investigate the sensitivity of this parameter to both the cracking of the concrete section and the tension in the cables and also to compare results given by different types of experimental tests.
Research in aeroelasticity EFP-2006
DEFF Research Database (Denmark)
This report contains the results from the Energy Research Project ”Program for Research in Applied Aeroelasticity, EFP-2006” covering the period from 1. April 2006 to 31. March 2007. A summary of the main results from the project is given in the following. The aerodynamics for rotors incl. spinner...... that they can be used successfully, but that downwind and short winglets are most efficient. Investigating a strategy for reduction of loads and vibrations at extreme wind speeds showed that there are considerably uncertainties in the numerical models and that the main concluding remark is that measurements...
Resistance factors for 100% dynamic testing, with and without static load tests.
2011-05-01
Current department of transportation (DOT) and Federal Highway Administration (FHWA) practice has highly : variable load and resistance factor design (LRFD) resistance factors, , for driven piles from design (e.g., Standard : Penetration Tests (SPT...
Harmonic Balance Computations of Fan Aeroelastic Stability
Bakhle, Milind A.; Reddy, T. S. R.
2010-01-01
A harmonic balance (HB) aeroelastic analysis, which has been recently developed, was used to determine the aeroelastic stability (flutter) characteristics of an experimental fan. To assess the numerical accuracy of this HB aeroelastic analysis, a time-domain aeroelastic analysis was also used to determine the aeroelastic stability characteristics of the same fan. Both of these three-dimensional analysis codes model the unsteady flowfield due to blade vibrations using the Reynolds-averaged Navier-Stokes (RANS) equations. In the HB analysis, the unsteady flow equations are converted to a HB form and solved using a pseudo-time marching method. In the time-domain analysis, the unsteady flow equations are solved using an implicit time-marching approach. Steady and unsteady computations for two vibration modes were carried out at two rotational speeds: 100 percent (design) and 70 percent (part-speed). The steady and unsteady results obtained from the two analysis methods compare well, thus verifying the recently developed HB aeroelastic analysis. Based on the results, the experimental fan was found to have no aeroelastic instability (flutter) at the conditions examined in this study.
American Society for Testing and Materials. Philadelphia
2008-01-01
1.1 This standard describes three test methods for determining the modulus of elasticity in bending and the bending strength of metallic strips or sheets intended for the use in flat springs: 1.1.1 Test Method A—a cantilever beam, 1.1.2 Test Method B—a three-point loaded beam (that is, a beam resting on two supports and centrally loaded), and 1.1.3 Test Method C—a four-point loaded beam (that is, a beam resting on two supports and loaded at two points equally spaced from each support). 1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 6.1 This test me...
Bijon, Charles; Diaz, Juan José Hidalgo; Pizza, Chiara; Facca, Sybille; Pereira, Alexis; Liverneaux, Philippe
2017-11-01
When examining lacerations to the volar aspect of the hand a gauze test may usually be performed to detect nerve injuries. However, published literature suggests that its sensitivity and specificity are lower than 100%. The aim of this study was to determine whether a Weber static (main hypothesis) and dynamic test or a Semmes-Weinstein test (secondary hypotheses) could be a more reliable test than the gauze test to rule out any nerve injury and avoid unnecessary wound explorations. Our case series included a total of 102 patients presenting with 123 palmar lacerations and 158 nerve injuries. On arrival at the emergency department, every patient was tested for epicritic sensation at the pulp of the injured and contralateral fingers with the Weber static and dynamic tests and the Semmes-Weinstein monofilament test. All lacerations underwent exploration under anesthetic to rule out nerve injury. The sensitivities of the gauze test, the Weber static test, the Weber dynamic test and the Semmes Weinstein monofilament test were proven to be 82.5%, 98.6%, 97.9% and 86.7% respectively. The specificities of the gauze test, the Weber static test, the Weber dynamic test and the Semmes Weinstein monofilament test were 79%, 79%, 79% and 78.9% respectively. Examination of lacerations to the volar aspect of the hand to rule out any nerve injuries should include a Weber static test instead of a gauze test. A negative Weber static test should not however discourage a surgical exploration of the laceration to rule out tendinous or vascular injury. Copyright © 2017 Elsevier Ltd. All rights reserved.
Cramer, J. M.; Marshall, W. M.; Pal, S.; Santoro, R. J.
2003-01-01
Twin thruster tests have been conducted with the Penn State RBCC test article operating at sea- level static conditions. Significant differences were observed in the performance characteristics for two different thruster centerline spacings. Changing the thruster spacing from 2.50 to 1.75 in. reduced the entrained air velocity (-17%) and the thrust (-7%) for tests at a thruster chamber pressure of 200 psia and MR = 8. In addition, significant differences were seen in the static pressure profiles, the Raman spectroscopy profiles, and the acoustic power spectrum for these two configurations.
Developing a press for static and dynamic testing of orthopedic devices and biological tissue
Directory of Open Access Journals (Sweden)
Arlex Leyton Virgen
2008-09-01
Full Text Available This paper describes designing and constructing a test machine having a 1,800 N capacity and maximum 3 Hz frequency which will be used in static and dynamic testing of biological tissues and orthopedic devices such as external fixers. It consists of an oc-tagonal base with 500 mm distance between faces and a crosshead which slides between two columns (useful 350 mm opening thus allowing changing the height (maximum 600 mm according to the size of the specimen to be tested. A ball screw actuator is mounted over the crosshead which transforms a servomotor’s rotating movement into a lineal movement (maximum 150 mm stroke. First validations indicated that the machine performed within the design parameters. This project shows that the techno-logy required for supporting research is possible in developing countries thereby avoiding dependence on foreign companies for supporting, maintaining and updating equipment. Some conditions were also produced for the evolution of mechanical engi-neering in Colombia.
Static and Dynamic Aeroelastic Tailoring With Variable Camber Control
Stanford, Bret K.
2016-01-01
This paper examines the use of a Variable Camber Continuous Trailing Edge Flap (VCCTEF) system for aeroservoelastic optimization of a transport wingbox. The quasisteady and unsteady motions of the flap system are utilized as design variables, along with patch-level structural variables, towards minimizing wingbox weight via maneuver load alleviation and active flutter suppression. The resulting system is, in general, very successful at removing structural weight in a feasible manner. Limitations to this success are imposed by including load cases where the VCCTEF system is not active (open-loop) in the optimization process, and also by including actuator operating cost constraints.
Static Aeroelastic Optimization of Composite Wings with Variable Stiffness Laminates
Dillinger, J.K.S.
2014-01-01
The application of composite material in load carrying structural components of an aircraft is rapidly gaining momentum. While part of the reason for this can certainly be attributed to an increasing confidence of designers in the new material as a result of growing experience, two other crucial
Smiley, Robert F; Horne, Walter B
1957-01-01
The vertical force-deflection characteristics were experimentally determined for a pair of 56-inch-diameter tires under static and drop-test conditions with and without prerotation. For increasing force, the tires were found to be least stiff for static tests, almost the same as for the static case for prerotation drop tests as long as the tires remain rotating, and appreciably stiffer for drop tests without prerotation.
Multifidelity Robust Aeroelastic Design, Phase I
National Aeronautics and Space Administration — Nielsen Engineering & Research (NEAR) proposes a new method to generate mathematical models of wind-tunnel models and flight vehicles for robust aeroelastic...
Adjustable Fidelity Computational Aeroelasticity Procedure (AFCAP) Project
National Aeronautics and Space Administration — NextGen proposes an approach to significantly enhance aeroelastic analysis capabilities over what is commonly available in linear analysis environments such as...
Computer-assisted static/dynamic renal imaging: a screening test for renovascular hypertension
International Nuclear Information System (INIS)
Keim, H.J.; Johnson, P.M.; Vaughan, E.D. Jr.; Beg, K.; Follett, D.A.; Freeman, L.M.; Laragh, J.H.
1979-01-01
Computer-assisted static/dynamic renal imaging with [ 197 Hg] chlormerodrin and [/sup 99m/Tc] pertechnetate was evaluated prospectively as a screening test for renovascular hypertension. Results are reported for 51 patients: 33 with benign essential hypertension and 18 with renovascular hypertension, and for 21 normal controls. All patients underwent renal arteriography. Patients with significant obesity, renal insufficiency, or renoparenchymal disease were excluded from this study. Independent visual analyses of renal gamma images and time-activity transit curves identified 17 of the 18 patients with renovascular hypertension; one study was equivocal. There were five equivocal and three false-positive results in the essential hypertension and normal control groups. The sensitivity of the method was 94% and the specificity 85%. Since the prevalence of the renovascular subset of hypertension is approximately 5%, the predictive value is only 25%. Inclusion of computer-generated data did not improve this result. Accordingly, this method is not recommended as a primary screening test for renovascular hypertension
Quasi-static characterisation and impact testing of auxetic foam for sports safety applications
International Nuclear Information System (INIS)
Duncan, Olly; Alderson, Andrew; Foster, Leon; Senior, Terry; Allen, Tom
2016-01-01
This study compared low strain rate material properties and impact force attenuation of auxetic foam and the conventional open-cell polyurethane counterpart. This furthers our knowledge with regards to how best to apply these highly conformable and breathable auxetic foams to protective sports equipment. Cubes of auxetic foam measuring 150 × 150 × 150 mm were fabricated using a thermo–mechanical conversion process. Quasi-static compression confirmed the converted foam to be auxetic, prior to being sliced into 20 mm thick cuboid samples for further testing. Density, Poisson’s ratio and the stress–strain curve were all found to be dependent on the position of each cuboid from within the cube. Impact tests with a hemispherical drop hammer were performed for energies up to 6 J, on foams covered with a polypropylene sheet between 1 and 2 mm thick. Auxetic samples reduced peak force by ∼10 times in comparison to the conventional foam. This work has shown further potential for auxetic foam to be applied to protective equipment, while identifying that improved fabrication methods are required. (paper)
Silva, Walter A.; Bennett, Robert M.
1992-01-01
The Computational Aeroelasticity Program-Transonic Small Disturbance (CAP-TSD) code, developed at LaRC, is applied to the active flexible wing wind-tunnel model for prediction of transonic aeroelastic behavior. A semi-span computational model is used for evaluation of symmetric motions, and a full-span model is used for evaluation of antisymmetric motions, and a full-span model is used for evaluation of antisymmetric motions. Static aeroelastic solutions using CAP-TSD are computed. Dynamic deformations are presented as flutter boundaries in terms of Mach number and dynamic pressure. Flutter boundaries that take into account modal refinements, vorticity and entropy corrections, antisymmetric motion, and sensitivity to the modeling of the wing tip ballast stores are also presented with experimental flutter results.
Pittman, J. L.; Giles, G. L.
1986-01-01
An iterative procedure for the static aeroelastic design of a flexible wing at supersonic speeds has been developed. The procedure combines a nonlinear, full-potential solver (NCOREL) with an equivalent plate structural analysis method. The NCOREL method yields significantly improved aerodynamic estimates compared to linear theory. The equivalent plate structural analysis method demonstrates an order of magnitude reduction in computer memory and execution time compared to finite-element methods. A highly swept wing is analyzed at high lift using this aeroelastic procedure. The results indicate that the wing deforms favorably due to aerodynamic loading and, consequently, that the inviscid drag levels do not vary at the required lift coefficient although the angle of attack varies significantly. A sensitivity analysis of the type required for optimization studies was also performed with the aeroelastic design procedure.
Directory of Open Access Journals (Sweden)
Mohsen Rostami
2012-06-01
Full Text Available The pathophysiology of primary benign exertional headache (EH is not still clearly defined. Some researchers have suggested an impaired vascular response as the etiology of this disorder. In this study we investigated whether there are any differences in blood pressure (BP and heart rate (HR of the subjects in course of the static and dynamic exercises and the treadmill stress test between those with and without EH. From university students, 22 patients with EH (mean age: 19.8 ± 2.10, Female to Male: 7:15 and 20 normal subjects (mean age: 19.3 ± 1.97, Female: Male: 8:12 were recruited. All the subjects performed the static and dynamic exercises at 30 and 20 percent of the maximal voluntary contraction (MVC and Bruce treadmill stress test according to the standard protocols. HR and BP of all the cases at the baseline and during and immediately after each test were measured. No significant difference was found between the mean rise of HR, systolic and diastolic BP of the subjects with and without EH in static and dynamic exercises and also treadmill stress test. It seems that between those with and without EH, there is no significant difference in rise of HR and BP response to static and dynamic exercises and treadmill stress test. Further studies are required to find the pathophysiology and risk factors of EH.
Non-linear aeroelastic prediction for aircraft applications
de C. Henshaw, M. J.; Badcock, K. J.; Vio, G. A.; Allen, C. B.; Chamberlain, J.; Kaynes, I.; Dimitriadis, G.; Cooper, J. E.; Woodgate, M. A.; Rampurawala, A. M.; Jones, D.; Fenwick, C.; Gaitonde, A. L.; Taylor, N. V.; Amor, D. S.; Eccles, T. A.; Denley, C. J.
2007-05-01
in this domain. This is set within the context of a generic industrial process and the requirements of UK and US aeroelastic qualification. A range of test cases, from simple small DOF cases to full aircraft, have been used to evaluate and validate the non-linear methods developed and to make comparison with the linear methods in everyday use. These have focused mainly on aerodynamic non-linearity, although some results for structural non-linearity are also presented. The challenges associated with time domain (coupled computational fluid dynamics-computational structural model (CFD-CSM)) methods have been addressed through the development of grid movement, fluid-structure coupling, and control surface movement technologies. Conclusions regarding the accuracy and computational cost of these are presented. The computational cost of time-domain methods, despite substantial improvements in efficiency, remains high. However, significant advances have been made in reduced order methods, that allow non-linear behaviour to be modelled, but at a cost comparable with that of the regular linear methods. Of particular note is a method based on Hopf bifurcation that has reached an appropriate maturity for deployment on real aircraft configurations, though only limited results are presented herein. Results are also presented for dynamically linearised CFD approaches that hold out the possibility of non-linear results at a fraction of the cost of time coupled CFD-CSM methods. Local linearisation approaches (higher order harmonic balance and continuation method) are also presented; these have the advantage that no prior assumption of the nature of the aeroelastic instability is required, but currently these methods are limited to low DOF problems and it is thought that these will not reach a level of maturity appropriate to real aircraft problems for some years to come. Nevertheless, guidance on the most likely approaches has been derived and this forms the basis for ongoing
Results from the First Two Flights of the Static Computer Memory Integrity Testing Experiment
Hancock, Thomas M., III
1999-01-01
This paper details the scientific objectives, experiment design, data collection method, and post flight analysis following the first two flights of the Static Computer Memory Integrity Testing (SCMIT) experiment. SCMIT is designed to detect soft-event upsets in passive magnetic memory. A soft-event upset is a change in the logic state of active or passive forms of magnetic memory, commonly referred to as a "Bitflip". In its mildest form a soft-event upset can cause software exceptions, unexpected events, start spacecraft safeing (ending data collection) or corrupted fault protection and error recovery capabilities. In it's most severe form loss of mission or spacecraft can occur. Analysis after the first flight (in 1991 during STS-40) identified possible soft-event upsets to 25% of the experiment detectors. Post flight analysis after the second flight (in 1997 on STS-87) failed to find any evidence of soft-event upsets. The SCMIT experiment is currently scheduled for a third flight in December 1999 on STS-101.
Comparison of Numerical Analyses with a Static Load Test of a Continuous Flight Auger Pile
Hoľko, Michal; Stacho, Jakub
2014-12-01
The article deals with numerical analyses of a Continuous Flight Auger (CFA) pile. The analyses include a comparison of calculated and measured load-settlement curves as well as a comparison of the load distribution over a pile's length. The numerical analyses were executed using two types of software, i.e., Ansys and Plaxis, which are based on FEM calculations. Both types of software are different from each other in the way they create numerical models, model the interface between the pile and soil, and use constitutive material models. The analyses have been prepared in the form of a parametric study, where the method of modelling the interface and the material models of the soil are compared and analysed. Our analyses show that both types of software permit the modelling of pile foundations. The Plaxis software uses advanced material models as well as the modelling of the impact of groundwater or overconsolidation. The load-settlement curve calculated using Plaxis is equal to the results of a static load test with a more than 95 % degree of accuracy. In comparison, the load-settlement curve calculated using Ansys allows for the obtaining of only an approximate estimate, but the software allows for the common modelling of large structure systems together with a foundation system.
Some experiences with active control of aeroelastic response
Newsom, J. R.; Abel, I.
1981-01-01
Flight and wind tunnel tests were conducted and multidiscipline computer programs were developed as part of investigations of active control technology conducted at the NASA Langley Research Center. Unsteady aerodynamics approximation, optimal control theory, optimal controller design, and the Delta wing and DC-10 models are described. The drones for aerodynamics and structural testing (DAST program) for evaluating procedures for aerodynamic loads prediction and the design of active control systems on wings with significant aeroelastic effects is described as well as the DAST model used in the wind tunnel tests.
Controlled aeroelastic response and airfoil shaping using adaptive materials and integrated systems
Pinkerton, Jennifer L.; McGowan, Anna-Maria R.; Moses, Robert W.; Scott, Robert C.; Heeg, Jennifer
1996-05-01
This paper presents an overview of several activities of the Aeroelasticity Branch at the NASA Langley Research Center in the area of applying adaptive materials and integrated systems for controlling both aircraft aeroelastic response and airfoil shape. The experimental results of four programs are discussed: the Piezoelectric Aeroelastic Response Tailoring Investigation (PARTI); the adaptive neural control of aeroelastic response (ANCAR) program; the actively controlled response of buffet affected tails (ACROBAT) program; and the Airfoil THUNDER Testing to ascertain charcteristics (ATTACH) project. The PARTI program demonstrated active flutter control and significant reductions in aeroelastic response at dynamic pressures below flutter using piezoelectric actuators. The ANCAR program seeks to demonstrate the effectiveness of using neural networks to schedule flutter suppression control laws. The ACROBAT program studied the effectiveness of a number of candidate actuators, including a rudder and piezoelectric actuators, to alleviate vertical tail buffeting. In the ATTACH project, the feasibility of using thin-layer composite-unimorph piezoelectric driver and sensor (THUNDER) wafers to control airfoil aerodynamic characteristics was investigated. Plans for future applications are also discussed.
Dynamics and control of hypersonic aeropropulsive/aeroelastic vehicles
Schmidt, David K.
1992-01-01
The guidance and control of hypersonic vehicles is examined by studying the airframe/engine/structural-dynamic interactions of a generic vehicle with scramjet propulsion. The pitch-attitude dynamics are described for the vehicle configuration that can sustain hypersonic flight at near-orbital altitudes. These aerospacecraft have strong airframe/engine/elastic coupling in attitude dynamics and engine responses with static instability with respect to pitch. An integrated airframe-engine control system is presented for the control of the system's strong aeropropulsive/aeroelastic coupling. The control methodology utilizes feedback of measured/synthesized values of angle of attack, blended pitch rate, thrust, and combustor-inlet pressure. The multiinput/multioutput engine controller requires high-bandwidth actuation of the fuel-flow control and the effective diffuser ratio. The proposed control laws do not provide optimized performance in terms of pitch response suggesting that additional control crossfeeds and filtering is needed.
Energy Technology Data Exchange (ETDEWEB)
Goff, D. R.; Cutright, R. L.; Griffith, R. A.; Loomis, R. B.; Maxfield, D. A.; Moritz, R. S.
1981-10-01
METC Prototype Test Valve No. F-1 is a hybrid design, based on a segmented ball termed a visor valve, developed and manufactured by Fairchild Stratos Division under contract to the Department of Energy. The valve uses a visor arm that rotates into position and then translates to seal. This valve conditionally completed static testing at METC with clean gas to pressures of 1600 psig and internal valve temperatures to 600/sup 0/F. External leakage was excessive due to leakage through the stuffing box, purge fittings, external bolts, and other assemblies. The stuffing box was repacked several times and redesigned midway through the testing, but external leakage was still excessive. Internal leakage through the seats, except for a few anomalies, was very low throughout the 2409 cycles of testing. As shown by the low internal leakage, the visor valve concept appears to have potential for lock-hopper valve applications. The problems that are present with METC Prototype Test Valve No. F-1 are in the seals, which are equivalent to the shaft and bonnet seals in standard valve designs. The operating conditions at these seals are well within the capabilities of available seal designs and materials. Further engineering and minor modifications should be able to resolve the problems identified during static testing.
Energy Technology Data Exchange (ETDEWEB)
Chin, Eric Brian [Sandia National Lab. (SNL-CA), Livermore, CA (United States); English, Shawn Allen [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Briggs, Timothy [Sandia National Lab. (SNL-CA), Livermore, CA (United States)
2015-09-01
V arious phenomenological delamination initiation criteria are analyzed in quasi - static punch - shear tests conducted on six different geometries. These six geometries are modeled and analyzed using elastic, large - deformation finite element analysis. Analysis output is post - processed to assess different delamination initiation criteria, and their applicability to each of the geometries. These criteria are compared to test results to assess whether or not they are appropriate based on what occurred in testing. Further, examinations of CT scans and ultrasonic images o f test specimens are conducted in the appendix to determine the sequence of failure in each test geometry.
Material and Thickness Grading for Aeroelastic Tailoring of the Common Research Model Wing Box
Stanford, Bret K.; Jutte, Christine V.
2014-01-01
This work quantifies the potential aeroelastic benefits of tailoring a full-scale wing box structure using tailored thickness distributions, material distributions, or both simultaneously. These tailoring schemes are considered for the wing skins, the spars, and the ribs. Material grading utilizes a spatially-continuous blend of two metals: Al and Al+SiC. Thicknesses and material fraction variables are specified at the 4 corners of the wing box, and a bilinear interpolation is used to compute these parameters for the interior of the planform. Pareto fronts detailing the conflict between static aeroelastic stresses and dynamic flutter boundaries are computed with a genetic algorithm. In some cases, a true material grading is found to be superior to a single-material structure.
Wu, Bitao; Lu, Huaxi; Chen, Bo; Gao, Zhicheng
2017-07-19
A finite model updating method that combines dynamic-static long-gauge strain responses is proposed for highway bridge static loading tests. For this method, the objective function consisting of static long-gauge stains and the first order modal macro-strain parameter (frequency) is established, wherein the local bending stiffness, density and boundary conditions of the structures are selected as the design variables. The relationship between the macro-strain and local element stiffness was studied first. It is revealed that the macro-strain is inversely proportional to the local stiffness covered by the long-gauge strain sensor. This corresponding relation is important for the modification of the local stiffness based on the macro-strain. The local and global parameters can be simultaneously updated. Then, a series of numerical simulation and experiments were conducted to verify the effectiveness of the proposed method. The results show that the static deformation, macro-strain and macro-strain modal can be predicted well by using the proposed updating model.
KNOW-BLADE task-4 report: Navier-Stokes aeroelasticity
DEFF Research Database (Denmark)
Politis, E.S.; Nikolaou, I.G.; Chaviaropoulos, P.K.
2004-01-01
The problem of the aeroelastic stability of wind turbine blades is addressed in this report by advancing the aerodynamic modelling in the beam element type codes from the engineering-type empirical models to unsteady, 2D or 3D, Navier-Stokes solvers. Inthis project, structural models for the full...... wind turbine blade have been combined with 2D and 3D unsteady Navier-Stokes solvers. The relative disadvantage of the quasi-3D approach (where the elastic solver is coupled with a 2D Navier-Stokes solver) isits inability to model induced flow. The lack of a validation test case did not allow...
Influence of stationary vehicles on bridge aerodynamic and aeroelastic coefficients
Czech Academy of Sciences Publication Activity Database
Pospíšil, Stanislav; Buljac, A.; Kozmar, H.; Kuznetsov, Sergeii; Macháček, Michael; Král, Radomil
2017-01-01
Roč. 22, č. 4 (2017), č. článku 05016012. ISSN 1084-0702 R&D Projects: GA ČR(CZ) GA15-01035S; GA MŠk(CZ) LO1219 Keywords : wind- vehicle -bridge system * cable-supported bridge * bridge aerodynamics and aeroelasticity * stationary vehicle s * wind tunnel tests Subject RIV: JM - Building Engineering OBOR OECD: Construction engineering, Municipal and structural engineering Impact factor: 1.476, year: 2016 http://ascelibrary.org/doi/full/10.1061/%28ASCE%29BE.1943-5592.0001017
Bower, Kelly J; McGinley, Jennifer L; Miller, Kimberly J; Clark, Ross A
2014-01-01
The Wii Balance Board (WBB) is a globally accessible device that shows promise as a clinically useful balance assessment tool. Although the WBB has been found to be comparable to a laboratory-grade force platform for obtaining centre of pressure data, it has not been comprehensively studied in clinical populations. The aim of this study was to investigate the measurement properties of tests utilising the WBB in people after stroke. Thirty individuals who were more than three months post-stroke and able to stand unsupported were recruited from a single outpatient rehabilitation facility. Participants performed standardised assessments incorporating the WBB and customised software (static stance with eyes open and closed, static weight-bearing asymmetry, dynamic mediolateral weight shifting and dynamic sit-to-stand) in addition to commonly employed clinical tests (10 Metre Walk Test, Timed Up and Go, Step Test and Functional Reach) on two testing occasions one week apart. Test-retest reliability and construct validity of the WBB tests were investigated. All WBB-based outcomes were found to be highly reliable between testing occasions (ICC = 0.82 to 0.98). Correlations were poor to moderate between WBB variables and clinical tests, with the strongest associations observed between task-related activities, such as WBB mediolateral weight shifting and the Step Test. The WBB, used with customised software, is a reliable and potentially useful tool for the assessment of balance and weight-bearing asymmetry following stroke. Future research is recommended to further investigate validity and responsiveness.
Chłopek, Zdzisław; Darkowski, Andrzej
2002-01-01
The paper presents a proposition of simulation studies of nitrogen oxide catalytic reduction. The method enables estimating the influence of catalytic reactors on ecological properties of engines in static bench tests (e.g., ECE R49, United Nations Economic Commission for Europe [UN/ECE], 2000; Standard No. ISO 8178-4:1996, International Organization for Standardization [ISO], 1996; Merkisz (1998). An algorithm of simulation studies is shown. A model catalytic reactor for selective catalytic reduction is described. Silver aluminate deposited on steel substrate covered with aluminium phosphate is used as a catalyst. Propene is used as a reductant. The results of reactor studies in a chemical lab are presented. A simulation of the influence of catalytic reactor properties on ecological properties of an engine was done. Unitary emission conversion coefficients of nitrogen oxide in a static test ECE R49 were determined.
Stranzinger, S; Faulhammer, E; Scheibelhofer, O; Calzolari, V; Biserni, S; Paudel, A; Khinast, J G
2018-04-05
Precise filling of capsules with doses in the mg-range requires a good understanding of the filling process. Therefore, we investigated the various process steps of the filling process by dynamic and static mode tests. Dynamic tests refer to filling of capsules in a regular laboratory dosator filling machine. Static tests were conducted using a novel filling system developed by us. Three grades of lactose excipients were filled into size 3 capsules with different dosing chamber lengths, nozzle diameters and powder bed heights, and, in the dynamic mode, with two filling speeds (500, 3000 caps/h). The influence of the gap at the bottom of the powder container on the fill weight and variability was assessed. Different gaps resulted in a change in fill weight in all materials, although in different ways. In all cases, the fill weight of highly cohesive Lactohale 220 increased when decreasing the gap. Furthermore, experiments with the stand-alone static test tool indicated that this very challenging powder could successfully be filled without any pre-compression in the range of 5 mg-20 mg with acceptable RSDs. This finding is of great importance since for very fine lactose powders high compression ratios (dosing-chamber-length-to-powder-bed height compression ratios) may result in jamming of the piston. Moreover, it shows that the static mode setup is suitable for studying fill weight and variability. Since cohesive powders, such as Lactohale 220, are hard to fill, we investigated the impact of vibration on the process. Interestingly, we found no correlation between the reported fill weight changes in dynamic mode at 3000 cph and static mode using similar vibration. However, we could show that vibrations during sampling in the static mode dramatically reduced fill weight variability. Overall, our results indicate that by fine-tuning instrumental settings even very challenging powders can be filled with a low-dose dosator capsule filling machine. This study is a
Renaissance of Aeroelasticity and Its Future
Friedmann, Peretz P.
1999-01-01
The primary objective of this paper is to demonstrate that the field of aeroelasticity continues to play a critical role in the design of modern aerospace vehicles, and several important problems are still far from being well understood. Furthermore, the emergence of new technologies, such as the use of adaptive materials (sometimes denoted as smart structures technology), providing new actuator and sensor capabilities, has invigorated aeroelasticity, and generated a host of new and challenging research topics that can have a major impact on the design of a new generation of aerospace vehicles.
Empirical Tests and Preliminary Results with the Krakatoa Tool for Full Static Program Verification
Ramírez-de León Edgar Darío; Chávez-Bosquez Oscar; Francisco-León Julián Javier
2014-01-01
XJML (Ramírez et al., 2012) is a modular external platform for Verification and Validation of Java classes using the Java Modeling Language (JML) through contracts written in XML. One problem faced in the XJML development was how to integrate Full Static Program Verification (FSPV). This paper presents the experiments and results that allowed us to define what tool to embed in XJML to execute FSPV.
Empirical Tests and Preliminary Results with the Krakatoa Tool for Full Static Program Verification
Directory of Open Access Journals (Sweden)
Ramírez-de León Edgar Darío
2014-10-01
Full Text Available XJML (Ramírez et al., 2012 is a modular external platform for Verification and Validation of Java classes using the Java Modeling Language (JML through contracts written in XML. One problem faced in the XJML development was how to integrate Full Static Program Verification (FSPV. This paper presents the experiments and results that allowed us to define what tool to embed in XJML to execute FSPV.
Aeroelastic Dynamics Simulation of Two BaffleBased Connected Shells
Directory of Open Access Journals (Sweden)
G. A. Shcheglov
2015-01-01
Full Text Available The present work is an extention study of aeroelastic vibrations of thin-walled structures with a spatial subsonic flow. An original algorithm for solving complex conjugated aeroelasticity problem, allowing to carry out direct numerical simulation of structural oscillations in the spatial flow of an incompressible medium are developed and tested. On the basis of this simulation study of the spectrum comes the driving forces acting on the flow in a spatial component elastic structure mounted on an impenetrable screen.Currently, updating the mathematical models of unsteady loads that act on the spacepurpose elastic designs such as launch vehicles, service tower installed on the launch pad is a challenge. We consider two thin-walled cantilevered rotating shells connected by a system of elastic couplings, installed next to the impenetrable baffle so that the axes of rotation are perpendicular to the baffle. Dynamics of elastic system is investigated numerically, using the vortex element method with the spatial separated flow of an incompressible medium. A feature of the algorithm is the common commercial complex MSC Patran / Nastran which is used in preparing data to calculate the shell dynamics thereby allowing to consider very complex dynamic schemes.The work performs the first calculations of the model problem concerning the forced oscillations of two coupled cylindrical shells in the flow of an incompressible medium. Comparing the load spectra for the elastic and absolutely rigid structure has shown that the frequency spectra vary slightly. Further calculations are required in which it will be necessary to increase the duration of the calculations, sampling in construction of design scheme, and given the large number of vibration modes that require increasing computing power.Experience in calculating aeroelastic dynamics of complex elastic structures taking into account the screen proved to be successful as a whole, thereby allowing to turn to
Aeroelastic Stability of Suspension Bridges using CFD
DEFF Research Database (Denmark)
Stærdahl, Jesper Winther; Sørensen, Niels; Nielsen, Søren R.K.
2007-01-01
In recent years large span suspension bridges with very thin and slender profiles have been built without proportional increasing torsional and bending stiffness. As a consequence large deformations at the mid-span can occur with risk of aeroelastic instability and structural failure. Analysis of...
Internal Structural Design of the Common Research Model Wing Box for Aeroelastic Tailoring
Jutte, Christine V.; Stanford, Bret K.; Wieseman, Carol D.
2015-01-01
This work explores the use of alternative internal structural designs within a full-scale wing box structure for aeroelastic tailoring, with a focus on curvilinear spars, ribs, and stringers. The baseline wing model is a fully-populated, cantilevered wing box structure of the Common Research Model (CRM). Metrics of interest include the wing weight, the onset of dynamic flutter, and the static aeroelastic stresses. Twelve parametric studies alter the number of internal structural members along with their location, orientation, and curvature. Additional evaluation metrics are considered to identify design trends that lead to lighter-weight, aeroelastically stable wing designs. The best designs of the individual studies are compared and discussed, with a focus on weight reduction and flutter resistance. The largest weight reductions were obtained by removing the inner spar, and performance was maintained by shifting stringers forward and/or using curvilinear ribs: 5.6% weight reduction, a 13.9% improvement in flutter speed, but a 3.0% increase in stress levels. Flutter resistance was also maintained using straight-rotated ribs although the design had a 4.2% lower flutter speed than the curved ribs of similar weight and stress levels were higher. For some configurations, the differences between curved and straight ribs were smaller, which provides motivation for future optimization-based studies to fully exploit the trade-offs.
High-speed imaging on static tensile test for unidirectional CFRP
Kusano, Hideaki; Aoki, Yuichiro; Hirano, Yoshiyasu; Kondo, Yasushi; Nagao, Yosuke
2008-11-01
The objective of this study is to clarify the fracture mechanism of unidirectional CFRP (Carbon Fiber Reinforced Plastics) under static tensile loading. The advantages of CFRP are higher specific stiffness and strength than the metal material. The use of CFRP is increasing in not only the aerospace and rapid transit railway industries but also the sports, leisure and automotive industries. The tensile fracture mechanism of unidirectional CFRP has not been experimentally made clear because the fracture speed of unidirectional CFRP is quite high. We selected the intermediate modulus and high strength unidirectional CFRP laminate which is a typical material used in the aerospace field. The fracture process under static tensile loading was captured by a conventional high-speed camera and a new type High-Speed Video Camera HPV-1. It was found that the duration of fracture is 200 microseconds or less, then images taken by a conventional camera doesn't have enough temporal-resolution. On the other hand, results obtained by HPV-1 have higher quality where the fracture process can be clearly observed.
Directory of Open Access Journals (Sweden)
Kelly J Bower
Full Text Available The Wii Balance Board (WBB is a globally accessible device that shows promise as a clinically useful balance assessment tool. Although the WBB has been found to be comparable to a laboratory-grade force platform for obtaining centre of pressure data, it has not been comprehensively studied in clinical populations. The aim of this study was to investigate the measurement properties of tests utilising the WBB in people after stroke.Thirty individuals who were more than three months post-stroke and able to stand unsupported were recruited from a single outpatient rehabilitation facility. Participants performed standardised assessments incorporating the WBB and customised software (static stance with eyes open and closed, static weight-bearing asymmetry, dynamic mediolateral weight shifting and dynamic sit-to-stand in addition to commonly employed clinical tests (10 Metre Walk Test, Timed Up and Go, Step Test and Functional Reach on two testing occasions one week apart. Test-retest reliability and construct validity of the WBB tests were investigated.All WBB-based outcomes were found to be highly reliable between testing occasions (ICC = 0.82 to 0.98. Correlations were poor to moderate between WBB variables and clinical tests, with the strongest associations observed between task-related activities, such as WBB mediolateral weight shifting and the Step Test.The WBB, used with customised software, is a reliable and potentially useful tool for the assessment of balance and weight-bearing asymmetry following stroke. Future research is recommended to further investigate validity and responsiveness.
Research in aeroelasticity EFP-2007
Energy Technology Data Exchange (ETDEWEB)
Bak, C.
2008-07-15
This report contains results from the EFP2007 project 'Program for Research in Applied Aeroelasticity'. The main results from this project are: 1) The rotor aerodynamics were computed using different types of models with focus on the flow around the tip. The results showed similar trend for all models. 2) Comparison of 3D CFD computations with and without inflow shear showed that the integrated rotor thrust and power were largely identical in the two situations. 3) The influence of tower shadow with and without inflow shear showed significant differences compared to BEMcomputations, which gives cause for further investigation. 4) 3D CFD computations showed that the flow in the region of the nacelle anemometer measured the flow angle in the wake with errors up to as much as 7 deg. relative to the freestream flow angle. 5) As long as the flow over a blade remains attached there is little difference between 2-D and 3-D flow. However, at separation an increased lift is observed close to the rotational axis. 6) A correlation based transition model has been implemented in the incompressible EllipSys2D/3D Navier-Stokes solver. Computations on airfoils and rotors showed good agreement and distinct improvement in the drag predictions compared to using fully turbulent computations. 7) Comparing the method of Dynamic Wake Meandering (DWM) and IEC, the IECmodel seems conservative regarding fatigue and extreme loads for the yaw, driving torque and flapwise bending, whereas the loads on tower and blade torsion are non-conservative. 8) An experimental method for measuring transition point and energy spectra in airfoil boundary layers using microphones has been developed. 9) A robust and automatic method for detecting transition based on microphone measurement on airfoil surfaces has been developed. 10) Transition points and the corresponding instabilities have clearly been observed in airfoil boundary layers. 11) Predictions of the transition points on airfoils using
Nguyen, Nhan; Kaul, Upender; Lebofsky, Sonia; Ting, Eric; Chaparro, Daniel; Urnes, James
2015-01-01
This paper summarizes the recent development of an adaptive aeroelastic wing shaping control technology called variable camber continuous trailing edge flap (VCCTEF). As wing flexibility increases, aeroelastic interactions with aerodynamic forces and moments become an increasingly important consideration in aircraft design and aerodynamic performance. Furthermore, aeroelastic interactions with flight dynamics can result in issues with vehicle stability and control. The initial VCCTEF concept was developed in 2010 by NASA under a NASA Innovation Fund study entitled "Elastically Shaped Future Air Vehicle Concept," which showed that highly flexible wing aerodynamic surfaces can be elastically shaped in-flight by active control of wing twist and bending deflection in order to optimize the spanwise lift distribution for drag reduction. A collaboration between NASA and Boeing Research & Technology was subsequently funded by NASA from 2012 to 2014 to further develop the VCCTEF concept. This paper summarizes some of the key research areas conducted by NASA during the collaboration with Boeing Research and Technology. These research areas include VCCTEF design concepts, aerodynamic analysis of VCCTEF camber shapes, aerodynamic optimization of lift distribution for drag minimization, wind tunnel test results for cruise and high-lift configurations, flutter analysis and suppression control of flexible wing aircraft, and multi-objective flight control for adaptive aeroelastic wing shaping control.
Non-Linear Aeroelastic Analyses and Testing,
1981-07-01
systems in modern air- craft can be observed, see Ref.f]. These control systems can greatly affect the dynamic behavior of the aircraft. Especially...Refs.[2,3,4]), which are introduced into modern aircraft design in order to pro- voke a desired change of the aircraft’s dynamic behavior, requires...the following notations ( Gothic letters refer to Laplace transformed variables): _G,JK : displacement of the power cylinder block and of the power
Computational Models for Nonlinear Aeroelastic Systems, Phase II
National Aeronautics and Space Administration — Clear Science Corp. and Duke University propose to develop and demonstrate new and efficient computational methods of modeling nonlinear aeroelastic systems. The...
Variable Fidelity Aeroelastic Toolkit - Structural Model, Phase I
National Aeronautics and Space Administration — The proposed innovation is a methodology to incorporate variable fidelity structural models into steady and unsteady aeroelastic and aeroservoelastic analyses in...
Goldman, Benjamin D.; Scott, Robert C,; Dowell, Earl H.
2014-01-01
The purpose of this work is to develop a set of theoretical and experimental techniques to characterize the aeroelasticity of the thermal protection system (TPS) on the NASA Hypersonic Inflatable Aerodynamic Decelerator (HIAD). A square TPS coupon experiences trailing edge oscillatory behavior during experimental testing in the 8' High Temperature Tunnel (HTT), which may indicate the presence of aeroelastic flutter. Several theoretical aeroelastic models have been developed, each corresponding to a different experimental test configuration. Von Karman large deflection theory is used for the plate-like components of the TPS, along with piston theory for the aerodynamics. The constraints between the individual TPS layers and the presence of a unidirectional foundation at the back of the coupon are included by developing the necessary energy expressions and using the Rayleigh Ritz method to derive the nonlinear equations of motion. Free vibrations and limit cycle oscillations are computed and the frequencies and amplitudes are compared with accelerometer and photogrammetry data from the experiments.
Directory of Open Access Journals (Sweden)
M.G. Bara Filho
2008-01-01
Full Text Available Strength and flexibility are common components of a training program and their maximal values are obtained through specific tests. However, little information about the damage effect of these training procedures in a skeletal muscle is known. Objective: To verify a serum CK changes 24 h after a sub maximal stretching routine and after the static flexibility and maximal strength tests. Methods: the sample was composed by 14 subjects (man and women, 28 ± 6 yr. physical education students. The volunteers were divided in a control group (CG and experimental group (EG that was submitted in a stretching routine (EG-ST, in a maximal flexibility static test (EG-FLEX and in 1-RM test (EG-1-RM, with one week interval among tests. The anthropometrics characteristics were obtained by digital scale with stadiometer (Filizola, São Paulo, Brasil, 2002. The blood samples were obtained using the IFCC method with reference values 26-155 U/L. The De Lorme and Watkins technique was used to access maximal maximal strength through bench press and leg press. The maximal flexibility test consisted in three 20 seconds sets until the point of maximal discomfort. The stretching was done in normal movement amplitude during 6 secons. Results: The basal and post 24 h CK values in CG and EG (ST; Flex and 1 RM were respectively 195,0 ± 129,5 vs. 202,1 ± 124,2; 213,3 ± 133,2 vs. 174,7 ± 115,8; 213,3 ± 133,2 vs. 226,6 ± 126,7 e 213,3 ± 133,2 vs. 275,9 ± 157,2. It was only observed a significant difference (p = 0,02 in the pre and post values inGE-1RM. Conclusion: only maximal strength dynamic exercise was capable to cause skeletal muscle damage.
Comparison between ground tests and flight data for two static 32 KB memories
International Nuclear Information System (INIS)
Cheynet, Ph.; Velazco, R.; Cheynet, Ph.; Ecoffet, R.; Duzellier, S.; David, J.P.; Loquet, J.G.
1999-01-01
The study concerns two 32 K-byte static memories, one from Hitachi (HM62256) and the other (HM65756) from Matra-MHS. The results correspond to around one year of measurement in high radiation orbit and a total of 268 upsets were detected. As a preliminary conclusion it can be stated that the MHS SRAM is probably at least 4 times more sensitive to SEU (single event upset) than the Hitachi SRAM. The Hitachi memory has exhibited what we call ''stuck-at'' bit errors. This kind of event is identified when the same address and data is found in error (fixed read data) for several consecutive read cycles. A confrontation of SEU rates derived from predictions to those measured in flight has shown that: - error rate is underestimated for HM62256 using standard prediction models, - error rate can be under or over-estimated for HM65756 but the dispersion on heavy-ion ground results does not allow us to conclude. (A.C.)
Small Engine Technology (Set) Task 8 Aeroelastic Prediction Methods
Eick, Chris D.; Liu, Jong-Shang
1998-01-01
AlliedSignal Engines, in cooperation with NASA LeRC, completed an evaluation of recently developed aeroelastic computer codes using test cases from the AlliedSignal Engines fan blisk database. Test data for this task includes strain gage, light probe, performance, and steady-state pressure information obtained for conditions where synchronous or flutter vibratory conditions were found to occur. Aeroelastic codes evaluated include the quasi 3-D UNSFLO (developed at MIT and modified to include blade motion by AlliedSignal), the 2-D FREPS (developed by NASA LeRC), and the 3-D TURBO-AE (under development at NASA LeRC). Six test cases each where flutter and synchronous vibrations were found to occur were used for evaluation of UNSFLO and FREPS. In addition, one of the flutter cases was evaluated using TURBO-AE. The UNSFLO flutter evaluations were completed for 75 percent radial span and provided good agreement with the experimental test data. Synchronous evaluations were completed for UNSFLO but further enhancement needs to be added to the code before the unsteady pressures can be used to predict forced response vibratory stresses. The FREPS evaluations were hindered as the steady flow solver (SFLOW) was unable to converge to a solution for the transonic flow conditions in the fan blisk. This situation resulted in all FREPS test cases being attempted but no results were obtained during the present program. Currently, AlliedSignal is evaluating integrating FREPS with our existing steady flow solvers to bypass the SFLOW difficulties. ne TURBO-AE steady flow solution provided an excellent match with the AlliedSignal Engines calibrated DAWES 3-D viscous solver. Finally, the TURBO-AE unsteady analyses also matched experimental observations by predicting flutter for the single test case evaluated.
Investigations on precursor measures for aeroelastic flutter
Venkatramani, J.; Sarkar, Sunetra; Gupta, Sayan
2018-04-01
Wind tunnel experiments carried out on a pitch-plunge aeroelastic system in the presence of fluctuating flows reveal that flutter instability is presaged by a regime of intermittency. It is observed that as the flow speed gradually increases towards the flutter speed, there appears intermittent bursts of periodic oscillations which become more frequent as the wind speed increases and eventually the dynamics transition into fully developed limit cycle oscillations, marking the onset of flutter. The signature from these intermittent oscillations are exploited to develop measures that forewarn a transition to flutter and can serve as precursors. This study investigates a suite of measures that are obtained directly from the time history of measurements and are hence model independent. The dependence of these precursors on the size of the measured data set and the time required for their computation is investigated. These measures can be useful in structural health monitoring of aeroelastic structures.
Development of an aeroelastic vibration power harvester
Bryant, Matthew; Garcia, Ephrahim
2009-03-01
Aeroelastic vibration of structures represents a novel energy harvesting opportunity that may offer significant advantages over traditional wind power devices in many applications. Such a system could complement existing alternative energy sources by allowing for distributed power generation and placement in urban areas. The device configuration of a simple two degree aeroelastic system suitable for piezoelectric power harvesting is presented. The mechanical, electromechanical, and aerodynamic equations of motion governing the dynamics and electrical output of the system as a function of incident wind speed are derived. The response and current output of one design for a bench top scale harvester are simulated and presented. Finally, a strategy for expanding the operating envelope of the power harvester is proposed and discussed.
Aeroelastic Analysis of Modern Complex Wings
Kapania, Rakesh K.; Bhardwaj, Manoj K.; Reichenbach, Eric; Guruswamy, Guru P.
1996-01-01
A process is presented by which aeroelastic analysis is performed by using an advanced computational fluid dynamics (CFD) code coupled with an advanced computational structural dynamics (CSD) code. The process is demonstrated on an F/A-18 Stabilator using NASTD (an in-house McDonnell Douglas Aerospace East CFD code) coupled with NASTRAN. The process is also demonstrated on an aeroelastic research wing (ARW-2) using ENSAERO (an in-house NASA Ames Research Center CFD code) coupled with a finite element wing-box structures code. Good results have been obtained for the F/A-18 Stabilator while results for the ARW-2 supercritical wing are still being obtained.
Geometrical Nonlinear Aeroelastic Stability Analysis of a Composite High-Aspect-Ratio Wing
Directory of Open Access Journals (Sweden)
Chang Chuan Xie
2008-01-01
Full Text Available A composite high-aspect-ratio wing of a high-altitude long-endurance (HALE aircraft was modeled with FEM by MSC/NASTRAN, and the nonlinear static equilibrium state is calculated under design load with follower force effect, but without load redistribution. Assuming the little vibration amplitude of the wing around the static equilibrium state, the system is linearized and the natural frequencies and mode shapes of the deformed structure are obtained. Planar doublet lattice method is used to calculate unsteady aerodynamics in frequency domain ignoring the bending effect of the deflected wing. And then, the aeroelastic stability analysis of the system under a given load condition is successively carried out. Comparing with the linear results, the nonlinear displacement of the wing tip is higher. The results indicate that the critical nonlinear flutter is of the flap/chordwise bending type because of the chordwise bending having quite a large torsion component, with low critical speed and slowly growing damping, which dose not appear in the linear analysis. Furthermore, it is shown that the variation of the nonlinear flutter speed depends on the scale of the load and on the chordwise bending frequency. The research work indicates that, for the very flexible HALE aircraft, the nonlinear aeroelastic stability is very important, and should be considered in the design progress. Using present FEM software as the structure solver (e.g. MSC/NASTRAN, and the unsteady aerodynamic code, the nonlinear aeroelastic stability margin of a complex system other than a simple beam model can be determined.
Jutte, Christine V.; Stanford, Bret K.; Wieseman, Carol D.; Moore, James B.
2014-01-01
This work explores the use of tow steered composite laminates, functionally graded metals (FGM), thickness distributions, and curvilinear rib/spar/stringer topologies for aeroelastic tailoring. Parameterized models of the Common Research Model (CRM) wing box have been developed for passive aeroelastic tailoring trade studies. Metrics of interest include the wing weight, the onset of dynamic flutter, and the static aeroelastic stresses. Compared to a baseline structure, the lowest aggregate static wing stresses could be obtained with tow steered skins (47% improvement), and many of these designs could reduce weight as well (up to 14%). For these structures, the trade-off between flutter speed and weight is generally strong, although one case showed both a 100% flutter improvement and a 3.5% weight reduction. Material grading showed no benefit in the skins, but moderate flutter speed improvements (with no weight or stress increase) could be obtained by grading the spars (4.8%) or ribs (3.2%), where the best flutter results were obtained by grading both thickness and material. For the topology work, large weight reductions were obtained by removing an inner spar, and performance was maintained by shifting stringers forward and/or using curvilinear ribs: 5.6% weight reduction, a 13.9% improvement in flutter speed, but a 3.0% increase in stress levels. Flutter resistance was also maintained using straightrotated ribs although the design had a 4.2% lower flutter speed than the curved ribs of similar weight and stress levels were higher. These results will guide the development of a future design optimization scheme established to exploit and combine the individual attributes of these technologies.
A Test-Bench for Measurement of Electrical Static Parameters of Strip Silicon Detectors
Golutvin, I A; Danilevich, V G; Dmitriev, A Yu; Elsha, V V; Zamiatin, Y I; Zubarev, E V; Ziaziulia, F E; Kozus, V I; Lomako, V M; Stepankov, D V; Khomich, A P; Shumeiko, N M; Cheremuhin, A E
2003-01-01
An automated test-bench for electrical parameters input control of the strip silicon detectors, used in the End-Cap Preshower detector of the CMS experiment, is described. The test-bench application allows one to solve a problem of silicon detectors input control in conditions of mass production - 1800 detectors over 2 years. The test-bench software is realized in Delphi environment and contains a user-friendly operator interface for measurement data processing and visualization as well as up-to-date facilities for MS-Windows used for the network database. High operating characteristics and reliability of the test-bench were confirmed while more than 800 detectors were tested. Some technical solutions applied to the test-bench could be useful for design and construction of automated facilities for electrical parameters measurements of the microstrip detectors input control.
A test-bench for measurement of electrical static parameters of strip silicon detectors
International Nuclear Information System (INIS)
Golutvin, I.A.; Dmitriev, A.Yu.; Elsha, V.V.
2003-01-01
An automated test-bench for electrical parameters input control of the strip silicon detectors, used in the End-Cap Preshower detector of the CMS experiment, is described. The test-bench application allows one to solve a problem of silicon detectors input control in conditions of mass production - 1800 detectors over 2 years. The test-bench software is realized in Delphi environment and contains a user-friendly operator interface for data processing and visualization as well as up-to-date facilities for MS-Windows used for the network database. High operating characteristics and reliability of the test-bench were confirmed while more than 800 detectors were tested. Some technical solutions applied to the test-bench could be useful for design and construction of automated facilities for electrical parameters measurements of the microstrip detectors input control. (author)
Static bending test after proximal femoral nail (PFN) removal - in vitro analysis
Paiva, Leonardo Morais; Macedo Neto, Sílvio Leite de; Souto, Diogo Ranier de Macedo; Ferreira, George Neri Barros; Costa, Hélio Ismael da; Freitas, Anderson
2017-01-01
Abstract Objective To evaluate, through biomechanical testing, the resistance to and energy required for the occurrence of proximal femoral fracture in synthetic bone after removal of a proximal femoral nail model (PFN), comparing the results obtained with a reinforcement technique using polymethylmethacrylate (PMMA). Methods Fifteen synthetic bones were used: five units for the control group (CG), five for the test group without reinforcement (TGNR), and five for the test group with reinfo...
Aeroelastic Response of the Adaptive Compliant Trailing Edge Transtition Section
Herrera, Claudia Y.; Spivey, Natalie D.; Lung, Shun-fat
2016-01-01
The Adaptive Compliant Trailing Edge demonstrator was a joint task under the Environmentally Responsible Aviation Project in partnership with the Air Force Research Laboratory and FlexSys, Inc. (Ann Arbor, Michigan), chartered by the National Aeronautics and Space Administration to develop advanced technologies that enable environmentally friendly aircraft, such as continuous mold-line technologies. The Adaptive Compliant Trailing Edge demonstrator encompassed replacing the Fowler flaps on the SubsoniC Aircraft Testbed, a Gulfstream III (Gulfstream Aerospace, Savannah, Georgia) aircraft, with control surfaces developed by FlexSys, Inc., a pair of uniquely-designed, unconventional flaps to be used as lifting surfaces during flight-testing to substantiate their structural effectiveness. The unconventional flaps consisted of a main flap section and two transition sections, inboard and outboard, which demonstrated the continuous mold-line technology. Unique characteristics of the transition sections provided a challenge to the airworthiness assessment for this part of the structure. A series of build-up tests and analyses were conducted to ensure the data required to support the airworthiness assessment were acquired and applied accurately. The transition sections were analyzed both as individual components and as part of the flight-test article assembly. Instrumentation was installed in the transition sections based on the analysis to best capture the in-flight aeroelastic response. Flight-testing was conducted and flight data were acquired to validate the analyses. This paper documents the details of the aeroelastic assessment and in-flight response of the transition sections of the unconventional Adaptive Compliant Trailing Edge flaps.
40 CFR Appendix 1 to Subpart A of... - Static Sheen Test
2010-07-01
... Subpart A of Part 435 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT... spatula used to mix the sample will be the principal sources of contamination problems. These problems... inhibit the spreading of 0.05 mL of diesel fuel added to the lined test container under the test...
Mark Alexander Butler; Joseph Dahlen; Finto Antony; Michael Kane; Thomas L. Eberhardt; Huizhe Jin; Kim Love-Myers; John Paul McTague
2016-01-01
Prior to the 1980s, the allowable stresses for lumber in North America were derived from testing of small clear specimens. However, the procedures were changed because these models were found to be inaccurate. Nevertheless, small clear testing continues to be used around the world for allowable stress determinations and in studies that examine forest management impacts...
PV inverter test setup for European efficiency, static and dynamic MPPT efficiency evaluation
DEFF Research Database (Denmark)
Sera, Dezso; Teodorescu, Remus; Valentini, Massimo
2008-01-01
(Denmark) on a commercial transformerless PV inverter. Thanks to the available experimental test setups, that provide the required high measuring accuracy, and the developed PV simulator, which is required for MPPT performance evaluation, PV Inverters can be pretested before being tested by accredited...
Parameter estimation of an aeroelastic aircraft using neural networks
Indian Academy of Sciences (India)
https://www.ias.ac.in/article/fulltext/sadh/025/02/0181-0191. Keywords. Parameter estimation; modelling; aeroelastic aircraft; neural networks; system identification. Abstract. Application of neural networks to the problem of aerodynamic modelling and parameter estimation for aeroelastic aircraft is addressed. A neural model ...
Proposal for Static Test of B-36B and B-36C Fuselages
1948-05-01
and the VDT engine installation. The truss tubes, the side shear panels , and the lower longerons have been considered individually in order to...test will be made of’ the forvmard vertical shear pavel in the turret bay. On this basis it app)-ears des-Irable to test the forw~ ardl portic’J-n and...bomb ractks will be set -up mnd tci;tnd for design load:s on a separate jig. (0) up rttryshear tests, x-:11i 1w run on t~he, shear panel skins to
Quasi-Static and Dynamic Sled Testing of Prototype Commuter Rail Passenger Seats
2008-04-22
In support of the Federal Railroad Administration?s (FRA) Railroad Equipment Safety Program, tests have been conducted on prototype commuter rail passenger seats which have been designed for improved occupant protection during commuter train accident...
Nguyen, Nhan; Ting, Eric; Chaparro, Daniel
2017-01-01
This paper investigates the effect of nonlinear large deflection bending on the aerodynamic performance of a high aspect ratio flexible wing. A set of nonlinear static aeroelastic equations are derived for the large bending deflection of a high aspect ratio wing structure. An analysis is conducted to compare the nonlinear bending theory with the linear bending theory. The results show that the nonlinear bending theory is length-preserving whereas the linear bending theory causes a non-physical effect of lengthening the wing structure under the no axial load condition. A modified lifting line theory is developed to compute the lift and drag coefficients of a wing structure undergoing a large bending deflection. The lift and drag coefficients are more accurately estimated by the nonlinear bending theory due to its length-preserving property. The nonlinear bending theory yields lower lift and span efficiency than the linear bending theory. A coupled aerodynamic-nonlinear finite element model is developed to implement the nonlinear bending theory for a Common Research Model (CRM) flexible wing wind tunnel model to be tested in the University of Washington Aeronautical Laboratory (UWAL). The structural stiffness of the model is designed to give about 10% wing tip deflection which is large enough that could cause the nonlinear deflection effect to become significant. The computational results show that the nonlinear bending theory yields slightly less lift than the linear bending theory for this wind tunnel model. As a result, the linear bending theory is deemed adequate for the CRM wind tunnel model.
Mechanical tests, static and modal finite element analysis for MWCNT composite materials
Directory of Open Access Journals (Sweden)
Daniela BARAN
2015-03-01
Full Text Available The main purpose of this paper is to develop some numerical experiences based on mechanical tests performed on MWCNT (Multi-wall carbon nanotubes composites created in our Material compartment using finite element commercial codes (here NASTRAN. The results of numerical simulations are consistent with the laboratory tests and encourage us to continue to improve the models using NASTRAN capabilities in order to obtain a realistic simulation of aeronautical structures made of such composites, considering their special properties.
ORNL Interim Progress Report on Static CIRFT Testing Curvature Data Update
Energy Technology Data Exchange (ETDEWEB)
Wang, Jy-An John [ORNL; Wang, Hong [ORNL
2016-10-10
Since the CIRFT tests reported in NUREG-7198 were generated, a number of factors that influence the recorded curvature measurement data were identified. In 2016, a data reanalysis task was undertaken to implement the lessons learned. This letter report provides the revised results of previous CIRFT tests, after implementing the following data reanalysis procedures: (A) experimental data smoothing and LVDT reset, (B) LVDT probe contact and sensor spacing correction for curvature data, and (C) LVDT probe dynamic vibration adjustment procedure development.
Aeroelastic effects on stability and control of hingeless rotor helicopters
Celi, Roberto
1988-01-01
The combined effect of torsional flexibility and offset of the aerodynamic center relative to the elastic axis on the stability and control of a hingeless rotor helicopter in forward flight is studied in this paper. The aeroelastic model of the blade is based on fully coupled flap-lag-torsion equations of motion, which include kinematic nonlinearities due to moderate deflections. The equations are discretized using a finite element Galerkin method in space, and a classical Galerkin method in time. The vehicle trim calculations are coupled to the blade aeroelastic response calculations. Quasilinearization is used to compute aeroelastic stability. Reducing torsional stiffness and moving the elastic axis ahead of the aerodynamic center strongly stabilizes the phugoid mode without reducing control sensitivity. Aeroelastic stability calculations must accompany flight dynamics calculations to prevent aeroelastic instabilities that might easily go undetected.
Aeroelastic modelling without the need for excessive computing power
Energy Technology Data Exchange (ETDEWEB)
Infield, D. [Loughborough Univ., Centre for Renewable Energy Systems Technology, Dept. of Electronic and Electrical Engineering, Loughborough (United Kingdom)
1996-09-01
The aeroelastic model presented here was developed specifically to represent a wind turbine manufactured by Northern Power Systems which features a passive pitch control mechanism. It was considered that this particular turbine, which also has low solidity flexible blades, and is free yawing, would provide a stringent test of modelling approaches. It was believed that blade element aerodynamic modelling would not be adequate to properly describe the combination of yawed flow, dynamic inflow and unsteady aerodynamics; consequently a wake modelling approach was adopted. In order to keep computation time limited, a highly simplified, semi-free wake approach (developed in previous work) was used. a similarly simple structural model was adopted with up to only six degrees of freedom in total. In order to take account of blade (flapwise) flexibility a simple finite element sub-model is used. Good quality data from the turbine has recently been collected and it is hoped to undertake model validation in the near future. (au)
Aeroelastic tailoring and structural optimisation using an advanced dynamic aeroelastic framework
Werter, N.P.M.; De Breuker, R.
2015-01-01
Driven by a need to improve the efficiency of aircraft and reduce the fuel consumption, composite materials are applied extensively in the design of aircraft. A dynamic aeroelastic framework for the conceptual design of a generic composite wing structure is presented. The wing is discretized in
Static, Fire and Fatigue Tests of Ultra High-Strength Fibre Reinforced Concrete and Ribbed Bars
DEFF Research Database (Denmark)
Hansen, Lars Pilegaard; Heshe, Gert
2001-01-01
A new building system has been developed during the last 10 years. This new system consists of a column / slab system with 6 x 6 m distance between the columns. The slabs are precast concrete elements of size 2.9 x 5.9 m connected through joints of ultra high strength fibre reinforced concrete...... tests of tensile specimens consisting of reinforcing bars embedded in Densit Joint Cast ®. The objective of these fatigue tests is to show that the system / connection can presumably also be used in structures subjected to dominant time- varying loads and thus for example in earthquake regions....
The manufacture of system for testing static random access memory radiation effect
International Nuclear Information System (INIS)
Chen Rui; Yang Chen
2008-01-01
Space radiation effects will lead to single event upset, event latch up and other phenomena in SRAM devices. This paper introduces the hardware, software composition and related testing technology of SRAM radiation effect testing device. Through to the SRAM chip current detection and power protection, it has solved the SRAM chip damage question in the SRAM experiment. It has accessed to the expected experimental data by using the device in different source of radiation conducted on SRAM Experimental study of radiation effects. It provides important references in the assessment of operational life and reinforcement of the memory carried in the satellites. (authors)
A stochastic model for the simulation of wind turbine blades in static stall
DEFF Research Database (Denmark)
Bertagnolio, Franck; Rasmussen, Flemming; Sørensen, Niels N.
2010-01-01
The aim of this work is to improve aeroelastic simulation codes by accounting for the unsteady aerodynamic forces that a blade experiences in static stall. A model based on a spectral representation of the aerodynamic lift force is defined. The drag and pitching moment are derived using...
USCG/MARAD Static Tests of the GPS Navigation Set-Z (Low Cost).
1980-03-01
c-eoverang hsrprilst rslsfr.t"e et Wneno sinape cNvigatins aretsu, ~hie reve CA fo- selfi tacuracyb andvailablit chichses was srblydette thate se...as a unit being tested for individual acceptance but as a tool to learn about and infer potential performance of the GPS system, as well as practical
Static bending test after proximal femoral nail (PFN removal - in vitro analysis
Directory of Open Access Journals (Sweden)
Leonardo Morais Paiva
Full Text Available Abstract Objective To evaluate, through biomechanical testing, the resistance to and energy required for the occurrence of proximal femoral fracture in synthetic bone after removal of a proximal femoral nail model (PFN, comparing the results obtained with a reinforcement technique using polymethylmethacrylate (PMMA. Methods Fifteen synthetic bones were used: five units for the control group (CG, five for the test group without reinforcement (TGNR, and five for the test group with reinforcement (TGR. The biomechanical analysis was performed simulating a fall on the trochanter using a servo-hydraulic machine. In the GC, the assay was performed with the PFN intact. In the TGNR and TGR groups, a model of PFN was introduced and the tests were performed in the TGNR, after simple removal of the synthesis material, and in the TGR, after removal of the same PFN model and filling of the cavity in the femoral neck with PMMA. Results All groups presented a basicervical fracture. The CG presented a mean of 1427.39 Newtons (N of maximum load and 10.14 Joules (J of energy for the occurrence of the fracture. The TGNR and TGR presented 892.14 N and 1477.80 N of maximum load, and 6.71 J and 11.99 J of energy, respectively. According to the Kruskal-Wallis ANOVA, there was a significant difference in the maximum load (p = 0.009 and energy (p = 0.007 between these groups. Conclusion The simple removal of a PFN in synthetic bone showed a significant reduction of the maximum load and energy for the occurrence of fracture, which were re-established with a reinforcement technique using PMMA.
Mechanical properties of reactor pressure vessel steels studied by static and dynamic torsion tests
International Nuclear Information System (INIS)
Munier, A.; Maamouri, M.; Schaller, R.; Mercier, O.
1993-01-01
Internal friction measurements and torsional plastic deformation tests have been performed in reactor pressure vessel steels (unirradiated, irradiated and irradiated/annealed specimens). The results of these experiments have been interpreted with help of transmission electron microscopy observations (conventional and in situ). It is shown how the interactions between screw dislocations and obstacles (Peierls valleys, impurities and precipitates) could explain the low temperature hardening and the irradiation embrittlement of ferritic steels. In addition, it appears that the nondestructive internal friction technique could be used advantageously to follow the evolution of the material properties under irradiation, as for instance the irradiation embrittlement of the reactor pressure vessel steels. (orig.)
Development of an aeroelastic methodology for surface morphing rotors
Cook, James R.
transmission of force and deflection information to achieve an aeroelastic coupling updated at each time step. The method is validated first by comparing the integrated aerodynamic work at CFD and CSD nodes to verify work conservation across the interface. Second, the method is verified by comparing the sectional blade loads and deflections of a rotor in hover and in forward flight with experimental data. Finally, stability analyses for pitch/plunge flutter and camber flutter are performed with comprehensive CSD/low-order-aerodynamics and tightly coupled CFD/CSD simulations and compared to analytical solutions of Peters' thin airfoil theory to verify proper aeroelastic behavior. The effects of simple harmonic camber actuation are examined and compared to the response predicted by Peters' finite-state (F-S) theory. In anticipation of active rotor experiments inside enclosed facilities, computational simulations are performed to evaluate the capability of CFD for accurately simulating flow inside enclosed volumes. A computational methodology for accurately simulating a rotor inside a test chamber is developed to determine the influence of test facility components and turbulence modeling and performance predictions. A number of factors that influence the physical accuracy of the simulation, such as temporal resolution, grid resolution, and aeroelasticity are also evaluated.
Research in Aeroelasticity EFP-2007-II
DEFF Research Database (Denmark)
shadow models implemented in the aeroelastic code HAWC2. • Using a streamlined tower reduces the tower shadow by 50% compared to a cylindrical tower. Similar reductions can be achieved using a four legged lattice tower. • The application of laminar/turbulent transition in CFD computations for airfoils...... the aerodynamic characteristics, but with reduced noise in the order of up to 3dB in total sound power level and up to 1dB with A-weighting. • 2D CFD simulations are performed to verify their capability in predicting multi element airfoil configurations. The present computations show good agreement with measured...
Research in Aeroelasticity EFP-2006[Wind turbines
Energy Technology Data Exchange (ETDEWEB)
Bak, C.
2007-07-15
This report contains the results from the Energy Research Project 'Program for Research in Applied Aeroelasticity, EFP-2006' covering the period from 1. April 2006 to 31. March 2007. A summary of the main results from the project is given in the following. The aerodynamics for rotors incl. spinner and winglets were clarified and the needed premises for an optimal rotor were explained. Also, the influence of viscous effects on rotor blades was investigated and the results indicated a range of optimum tip speed ratios. The use of winglets for wind turbine rotor was investigated and it was found that they can be used successfully, but that downwind and short winglets are most efficient. Investigating a strategy for reduction of loads and vibrations at extreme wind speeds showed that there are considerably uncertainties in the numerical models and that the main concluding remark is that measurements on a real blade or a real turbine are needed to further conclude the investigation. In the study of flutter and other torsional vibrations of blades at large deflections, modeling and analysis of the dynamics of a hydraulic pitch system for a 5 MW wind turbine was carried out. It was shown that the compressibility of the hydraulic oil introduced a dynamic mode in the pitch bearing degree of freedom. Also, investigating flutter for blades at large deflections showed that the flutter limit for a 5MW blade was moved significantly compared to blades without large deflections. The influence of modeling nacelle components was investigated by developing a generalized method to interface dynamic systems to the aeroelastic program HAWC2 and by exemplify by modeling the nacelle of an aeroelastic wind turbine model in a more detailed way by including a single planet stage of a gearbox. This simplified gearbox model captures in essence the splitting of the driving torque from the rotor shaft to the frame of the nacelle and to the generator. Investigating the influence of wind
A wind turbine hybrid simulation framework considering aeroelastic effects
Song, Wei; Su, Weihua
2015-04-01
In performing an effective structural analysis for wind turbine, the simulation of turbine aerodynamic loads is of great importance. The interaction between the wake flow and the blades may impact turbine blades loading condition, energy yield and operational behavior. Direct experimental measurement of wind flow field and wind profiles around wind turbines is very helpful to support the wind turbine design. However, with the growth of the size of wind turbines for higher energy output, it is not convenient to obtain all the desired data in wind-tunnel and field tests. In this paper, firstly the modeling of dynamic responses of large-span wind turbine blades will consider nonlinear aeroelastic effects. A strain-based geometrically nonlinear beam formulation will be used for the basic structural dynamic modeling, which will be coupled with unsteady aerodynamic equations and rigid-body rotations of the rotor. Full wind turbines can be modeled by using the multi-connected beams. Then, a hybrid simulation experimental framework is proposed to potentially address this issue. The aerodynamic-dominant components, such as the turbine blades and rotor, are simulated as numerical components using the nonlinear aeroelastic model; while the turbine tower, where the collapse of failure may occur under high level of wind load, is simulated separately as the physical component. With the proposed framework, dynamic behavior of NREL's 5MW wind turbine blades will be studied and correlated with available numerical data. The current work will be the basis of the authors' further studies on flow control and hazard mitigation on wind turbine blades and towers.
LERAT, P; FABRE, C; BALAY, JM
2003-01-01
The paper describes several experimentations on rigid pavements at Toulouse Blagnac airport, tested with heavy aircraft landing gear simulator developed by Airbus S.A.S. The main contributors of this program are Airbus, the French Civil Aviation Administration (STBA) and the French Road and Bridges Laboratory (LCPC). The first part of the program (1998 2000) deals with bituminous pavement. In 2001-2002-2003 the program has focused on Rigid tests. The main aim has been therefore to improve th...
Presentations from the Aeroelastic Workshop - latest results from AeroOpt
Energy Technology Data Exchange (ETDEWEB)
Hartvig Hansen, M. (ed.)
2011-10-15
This report contains the slides of the presentations at the Aeroelastic Workshop held at Risoe-DTU for the wind energy industry in Denmark on October 27, 2011. The scientific part of the agenda at this workshop was 1) Detailed and reduced models of dynamic mooring system (Anders M. Hansen). 2) Bend-twist coupling investigation in HAWC2 (Taeseong Kim). 3) Q3UIC - A new aerodynamic airfoil tool including rotational effects (Nestor R. Garcia). 4) Influence of up-scaling on loads, control and aerodynamic modeling (Helge Aa. Madsen). 5) Aerodynamic damping of lateral tower vibrations (Bjarne S. Kallesoee). 6) Open- and closed-loop aeroservoelastic analysis with HAWCStab2 (Morten H. Hansen). 7) Design and test of a thick, flatback, high-lift multielement airfoil (Frederik Zahle). The presented results are mainly obtained in the EUDP project ''Aeroelastic Optimization of MW Wind Turbines (AeroOpt)''. (Author)
Development and testing of a double-focusing, static, axisymmetric mass spectrometer
International Nuclear Information System (INIS)
Ritter, G.
1979-04-01
The developed mass spectrometer affords very high acceptance (cm 2 sr) compared with conventional mass spectrometers owing to its large solid angle of 0.178 sr. The ion optical properties of the instrument were tested by bombarding various targets (Al, Ni, Ti, Cu, Si) with potassium or caesium ions from a thermionic ion source with energies of 1, 2 and 3 keV and recording mass spectra of positive and negative sputtered ions. The ion optical beam path was calculated analytically (magnet system) in part and numerically in part (energy analyzer, einzel lenses and detector system) and represented in graph form. The results obtained from the mass spectra showed that the magnet system with its twelve permanent magnets is too irregular to produce mass linses with good resolution. Furthermore, it was found that the maximum primary energy of the alkali ions that was possible in this mass spectrometer owing to the breakdown strength was not sufficient to record surface-specific mass spectra since the target surface was covered within a very short time with an at least monatomic layer of alkali ions from the thermionic ion source. (orig./HP) [de
Static analysis of material testing reactor cores:critical core calculations
International Nuclear Information System (INIS)
Nawaz, A. A.; Khan, R. F. H.; Ahmad, N.
1999-01-01
A methodology has been described to study the effect of number of fuel plates per fuel element on critical cores of Material Testing Reactors (MTR). When the number of fuel plates are varied in a fuel element by keeping the fuel loading per fuel element constant, the fuel density in the fuel plates varies. Due to this variation, the water channel width needs to be recalculated. For a given number of fuel plates, water channel width was determined by optimizing k i nfinity using a transport theory lattice code WIMS-D/4. The dimensions of fuel element and control fuel element were determined using this optimized water channel width. For the calculated dimensions, the critical cores were determined for the given number of fuel plates per fuel element by using three dimensional diffusion theory code CITATION. The optimization of water channel width gives rise to a channel width of 2.1 mm when the number of fuel plates is 23 with 290 g ''2''3''5U fuel loading which is the same as in the case of Pakistan Reactor-1 (PARR-1). Although the decrease in number of fuel element results in an increase in optimal water channel width but the thickness of standard fuel element (SFE) and control fuel element (CFE) decreases and it gives rise to compact critical and equilibrium cores. The criticality studies of PARR-1 are in good agreement with the predictions
International Nuclear Information System (INIS)
Ise, Takeharu
1976-12-01
Review studies have been made on algorithms of numerical analysis and benchmark tests on point kinetics and quasistatic approximate kinetics computer codes to perform efficiently benchmark tests on space-dependent neutron kinetics codes. Point kinetics methods have now been improved since they can be directly applied to the factorization procedures. Methods based on Pade rational function give numerically stable solutions and methods on matrix-splitting are interested in the fact that they are applicable to the direct integration methods. An improved quasistatic (IQ) approximation is the best and the most practical method; it is numerically shown that the IQ method has a high stability and precision and the computation time which is about one tenth of that of the direct method. IQ method is applicable to thermal reactors as well as fast reactors and especially fitted for fast reactors to which many time steps are necessary. Two-dimensional diffusion kinetics codes are most practicable though there exist also three-dimensional diffusion kinetics code as well as two-dimensional transport kinetics code. On developing a space-dependent kinetics code, in any case, it is desirable to improve the method so as to have a high computing speed for solving static diffusion and transport equations. (auth.)
Aeroelastic simulation of higher harmonic control
Robinson, Lawson H.; Friedmann, Peretz P.
1994-01-01
This report describes the development of an aeroelastic analysis of a helicopter rotor and its application to the simulation of helicopter vibration reduction through higher harmonic control (HHC). An improved finite-state, time-domain model of unsteady aerodynamics is developed to capture high frequency aerodynamic effects. An improved trim procedure is implemented which accounts for flap, lead-lag, and torsional deformations of the blade. The effect of unsteady aerodynamics is studied and it is found that its impact on blade aeroelastic stability and low frequency response is small, but it has a significant influence on rotor hub vibrations. Several different HHC algorithms are implemented on a hingeless rotor and their effectiveness in reducing hub vibratory shears is compared. All the controllers are found to be quite effective, but very differing HHC inputs are required depending on the aerodynamic model used. Effects of HHC on rotor stability and power requirements are found to be quite small. Simulations of roughly equivalent articulated and hingeless rotors are carried out, and it is found that hingeless rotors can require considerably larger HHC inputs to reduce vibratory shears. This implies that the practical implementation of HHC on hingeless rotors might be considerably more difficult than on articulated rotors.
Transonic aeroelastic numerical simulation in aeronautical engineering
International Nuclear Information System (INIS)
Yang, G.
2005-01-01
An LU-SGS (lower-upper symmetric Gauss-Seidel) subiteration scheme is constructed for time-marching of the fluid equations. The HLLEW (Harten-Lax-van Leer-Einfeldt-Wada) scheme is used for the spatial discretization. The same subiteration formulation is applied directly to the structural equations of motion in generalized coordinates. Through subiteration between the fluid and structural equations, a fully implicit aeroelastic solver is obtained for the numerical simulation of fluid/structure interaction. To improve the ability for application to complex configurations, a multiblock grid is used for the flow field calculation and Transfinite Interpolation (TFI) is employed for the adaptive moving grid deformation. The infinite plate spline (IPS) and the principal of virtual work are utilized for the data transformation between the fluid and structure. The developed code was first validated through the comparison of experimental and computational results for the AGARD 445.6 standard aeroelastic wing. Then the flutter character of a tail wing with control surface was analyzed. Finally, flutter boundaries of a complex aircraft configuration were predicted. (author)
International Nuclear Information System (INIS)
Lipa, M.; Blanchet, J.; Cellier, F.
2007-01-01
Following experiences obtained with steam generator tubes of nuclear power plants, a cooling water quality of AVT (all volatile treatment) has been defined based on demineralised water with adjustment of the pH value to about 9.0/7.0 (25 C/200 C) by addiction of ammoniac, and hydrazine in order to absorb oxygen dissolved in water. At that time, a simplified water corrosion test program has been performed using static (no circulation) test cell samples made of above mentioned TS metal combinations. All test cell samples, prepared and filled with AVT water, were performed at 280 C and 65 bars in an autoclave during 3000 hours. The test cell water temperature has been chosen to be sufficient above the TS component working temperature, in order to accelerate an eventual corrosion process. Generally all above mentioned metal combinations survived the test campaign without stress corrosion cracking, with the exception of the memory metal junction (creep in Cu) and the bellows made of St-St 316L and Inconel 625 while 316 Ti bellows survived. In contrary to the vacuum brazed Cu-LSTP to St-St samples, some of flame brazed Cu to St-St samples failed either in the braze joint or in the copper structure itself. For comparison, a spot weld of an inflated 316L panel sample, filled voluntary with a caustic solution of pH 11.5 (25 C), failed after 90 h of testing (intergranular cracking at the spot weld), while an identical sample containing AVT water of pH 9.0 (25 C) survived without damage. The results of these tests, performed during 1986 and 1997, have never been published and therefore are presented more in detail in this paper since corrosion in hydraulic circuits is also an issue of ITER. Up to day, the TS cooling water plant operates with an above mentioned water treatment and no water leaks have been detected on in-vessel components originating from water corrosion at high temperature and high pressure. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Lipa, M. [CEA/DSM/DRFC Centre de Cadarache, 13 - Saint-Paul lez Durance (France); Blanchet, J.; Cellier, F. [Framatome, 71 - Saint Marcel (France). Centre Technique
2007-07-01
Following experiences obtained with steam generator tubes of nuclear power plants, a cooling water quality of AVT (all volatile treatment) has been defined based on demineralised water with adjustment of the pH value to about 9.0/7.0 (25 C/200 C) by addiction of ammoniac, and hydrazine in order to absorb oxygen dissolved in water. At that time, a simplified water corrosion test program has been performed using static (no circulation) test cell samples made of above mentioned TS metal combinations. All test cell samples, prepared and filled with AVT water, were performed at 280 C and 65 bars in an autoclave during 3000 hours. The test cell water temperature has been chosen to be sufficient above the TS component working temperature, in order to accelerate an eventual corrosion process. Generally all above mentioned metal combinations survived the test campaign without stress corrosion cracking, with the exception of the memory metal junction (creep in Cu) and the bellows made of St-St 316L and Inconel 625 while 316 Ti bellows survived. In contrary to the vacuum brazed Cu-LSTP to St-St samples, some of flame brazed Cu to St-St samples failed either in the braze joint or in the copper structure itself. For comparison, a spot weld of an inflated 316L panel sample, filled voluntary with a caustic solution of pH 11.5 (25 C), failed after 90 h of testing (intergranular cracking at the spot weld), while an identical sample containing AVT water of pH 9.0 (25 C) survived without damage. The results of these tests, performed during 1986 and 1997, have never been published and therefore are presented more in detail in this paper since corrosion in hydraulic circuits is also an issue of ITER. Up to day, the TS cooling water plant operates with an above mentioned water treatment and no water leaks have been detected on in-vessel components originating from water corrosion at high temperature and high pressure. (orig.)
LINFLUX-AE: A Turbomachinery Aeroelastic Code Based on a 3-D Linearized Euler Solver
Reddy, T. S. R.; Bakhle, M. A.; Trudell, J. J.; Mehmed, O.; Stefko, G. L.
2004-01-01
This report describes the development and validation of LINFLUX-AE, a turbomachinery aeroelastic code based on the linearized unsteady 3-D Euler solver, LINFLUX. A helical fan with flat plate geometry is selected as the test case for numerical validation. The steady solution required by LINFLUX is obtained from the nonlinear Euler/Navier Stokes solver TURBO-AE. The report briefly describes the salient features of LINFLUX and the details of the aeroelastic extension. The aeroelastic formulation is based on a modal approach. An eigenvalue formulation is used for flutter analysis. The unsteady aerodynamic forces required for flutter are obtained by running LINFLUX for each mode, interblade phase angle and frequency of interest. The unsteady aerodynamic forces for forced response analysis are obtained from LINFLUX for the prescribed excitation, interblade phase angle, and frequency. The forced response amplitude is calculated from the modal summation of the generalized displacements. The unsteady pressures, work done per cycle, eigenvalues and forced response amplitudes obtained from LINFLUX are compared with those obtained from LINSUB, TURBO-AE, ASTROP2, and ANSYS.
Computational Models for Nonlinear Aeroelastic Systems, Phase I
National Aeronautics and Space Administration — Clear Science Corp. and Duke University propose to develop and demonstrate a new and efficient computational method of modeling nonlinear aeroelastic systems. The...
Unsteady Design Optimization for Aeroelasticity Applications, Phase I
National Aeronautics and Space Administration — Aeroelasticity plays an important role in the design and development of highly flexible flight vehicles and blended wing body configurations. The operating margins...
Sensitivity Analysis and Error Control for Computational Aeroelasticity, Phase I
National Aeronautics and Space Administration — The objective of this proposal is the development of a next-generation computational aeroelasticity code, suitable for real-world complex geometries, and...
Aeroelastic Simulation Tool for Inflatable Ballute Aerocapture, Phase II
National Aeronautics and Space Administration — This project will develop a much-needed multidisciplinary analysis tool for predicting the impact of aeroelastic effects on the functionality of inflatable...
Unified Nonlinear Flight Dynamics and Aeroelastic Simulator Tool, Phase I
National Aeronautics and Space Administration — ZONA Technology, Inc. (ZONA) proposes a R&D effort to develop a Unified Nonlinear Flight Dynamics and Aeroelastic Simulator (UNFDAS) Tool that will combine...
Aeroelastic Simulation Tool for Inflatable Ballute Aerocapture, Phase I
National Aeronautics and Space Administration — This project will develop a much-needed multidisciplinary analysis tool for predicting the impact of aeroelastic effects on the functionality of inflatable...
Nguyen, Nhan; Ting, Eric; Nguyen, Daniel; Dao, Tung; Trinh, Khanh
2013-01-01
This paper presents a coupled vortex-lattice flight dynamic model with an aeroelastic finite-element model to predict dynamic characteristics of a flexible wing transport aircraft. The aircraft model is based on NASA Generic Transport Model (GTM) with representative mass and stiffness properties to achieve a wing tip deflection about twice that of a conventional transport aircraft (10% versus 5%). This flexible wing transport aircraft is referred to as an Elastically Shaped Aircraft Concept (ESAC) which is equipped with a Variable Camber Continuous Trailing Edge Flap (VCCTEF) system for active wing shaping control for drag reduction. A vortex-lattice aerodynamic model of the ESAC is developed and is coupled with an aeroelastic finite-element model via an automated geometry modeler. This coupled model is used to compute static and dynamic aeroelastic solutions. The deflection information from the finite-element model and the vortex-lattice model is used to compute unsteady contributions to the aerodynamic force and moment coefficients. A coupled aeroelastic-longitudinal flight dynamic model is developed by coupling the finite-element model with the rigid-body flight dynamic model of the GTM.
Numerical Wake Visualization for Airfoils Undergoing Forced and Aeroelastic Motions
Jones, K.D.; Center, K.B.
1996-01-01
AIAA Paper No. 96-0055, 34th AIAA Aerospace Sciences Meeting, Reno, Nevada, Jan. 1996. A virtual wind tunnel is developed by combining a fast, time-stepping flow solver with an interactive animation interface. Inviscid, incompressible flow solutions are provided by an unsteady, potential-flow code with arbitrary airfoils undergoing forced or aeroelastic motions. Aeroelastic response is predicted by a two-degree-of-freedom spring/mass system modeling the structural dynamics of a flexible wi...
Directory of Open Access Journals (Sweden)
Ion DIMA
2017-03-01
Full Text Available This article aims to provide a quick methodology to determine the critical values of the forces, displacements and stress function of frequency, under a combined linear static (101 Solution - Linear Static and dynamic load in frequency response (108 Solution - Frequency Response, Direct Method, applied to a micro launcher engine test bench, using NASTRAN 400 Solution - Implicit Nonlinear. NASTRAN/PATRAN software is used. Practically in PATRAN the preprocessor has to define a linear or nonlinear static load at step 1 and a dynamic in frequency response load (time dependent at step 2. In Analyze the following options are chosen: for Solution Type Implicit Nonlinear Solution (SOL 400 is selected, for Subcases Static Load and Transient Dynamic is chosen and for Subcase Select the two cases static and dynamic will be selected. NASTRAN solver will overlap results from static analysis with the dynamic analysis. The running time will be reduced three times if using Krylov solver. NASTRAN SYSTEM (387 = -1 instruction is used in order to activate Krylov option. Also, in Analysis the OP2 Output Format shall be selected, meaning that in bdf NASTRAN input file the PARAM POST 1 instruction shall be written. The structural damping can be defined in two different ways: either at the material card or using the PARAM, G, 0.05 instruction (in this example a damping coefficient by 5% was used. The SDAMPING instruction in pair with TABDMP1 work only for dynamic in frequency response, modal method, or in direct method with viscoelastic material, not for dynamic in frequency response, direct method (DFREQ, with linear elastic material. The Direct method – DFREQ used in this example is more accurate. A set in translation of boundary conditions was used and defined at the base of the test bench.
DEFF Research Database (Denmark)
Corfitzen, Charlotte B.; Arvin, Erik; Albrechtsen, Hans-Jørgen
/V-ratio), corresponding to lower bioavailable migration at smaller pipe diameters. Under sterile conditions gentle shaking of the water phase reduced the thickness of the boundary layer resulting in an increased bioavailable migration from the surfaces. The presence of bacteria together with the material overruled....../V-ratios had any effect on the bioavailable migration in the biotic tests. Not to underestimate growth potential of polymers, investigations should thus be performed in the presence of a diverse microbial population with paired measurements of biomass in the water phase and on the material surfaces....
Aeroelastic tailoring of composite aircraft wings
Mihaila-Andres, Mihai; Larco, Ciprian; Rosu, Paul-Virgil; Rotaru, Constantin
2017-07-01
The need of a continuously increasing size and performance of aerospace structures has settled the composite materials as the preferred materials in aircraft structures. Apart from the clear capacity to reduce the structural weight and with it the manufacture cost and the fuel consumption while preserving proper airworthiness, the prospect of tailoring a structure using the unique directional stiffness properties of composite materials allows an aerospace engineer to optimize aircraft structures to achieve particular design objectives. This paper presents a brief review of what is known as the aeroelastic tailoring of airframes with the intent of understanding the evolution of this research topic and at the same time providing useful references for further studies.
Aeroelastic optimization of MW wind turbines
Energy Technology Data Exchange (ETDEWEB)
Hartvig Hansen, M.; Zahle, F.
2011-12-15
This report contains the results from the Energy Development and Demonstration Project ''Aeroelastic Optimization of MW wind turbine'' (AeroOpt). The project has had the following five Work Packages: 1. Geometric non-linear, anisotropic beam element for HAWC2. 2. Closed-loop eigenvalue analysis of controlled wind turbines. 3. Resonant wave excitation of lateral tower bending modes. 4. Development of next generation aerodynamic design tools. 5. Advanced design and verification of airfoils. The purposes of these Work Packages are briefly described in the Preface and a summary of the results are given in Section 2. Thereafter, the results from each Work Package are described in eight subsequent chapters. (Author)
International Nuclear Information System (INIS)
Lipa, M.; Blanchet, J.
2007-01-01
Full text of publication follows: Tore supra (TS) has used from the beginning of operation in 1989 actively cooled plasma facing components. Since the operation and baking temperature of all in vessel components has been defined to be up to 230 deg. C at 40 bars, a special water chemistry of the cooling water plant was suggested in order to avoid eventual water leaks due to corrosion (general corrosion, galvanic corrosion, stress corrosion, etc.) at relative high temperatures and pressures in tubes, pipes, bellows, water boxes, coils, etc. From the beginning of TS operation, in vessel components (e.g. wall protection panels, limiters, ergodic divertor coils, neutralisers and diagnostics) represented a unique combination of metals in the hydraulic circuit mainly such as stainless steel, Inconel, CuCrZr, Nickel and Copper. These different materials were joined together by welding (St to St, Inconel to Inconel, CuCrZr to CuCrZr and CuCrZr to St-St via a Ni sleeve adapter), brazing (St-St to Cu and Cu-LSTP), friction (CuCrZr and Cu to St-St), explosion (CuCrZr to St-St) and memory metal junction (Cryo-fit to Cu - only test sample). Following experiences obtained with steam generator tubes of nuclear power plants, a cooling water quality of AVT (all volatile treatment) has been defined based on demineralized water with adjustment of the pH value to about 9.0/ 7.0 (25 deg. C/ 200 deg. C) by addiction of ammoniac, and hydrazine in order to absorb oxygen dissolved in water. At that time, a simplified water corrosion test program has been performed using static (no circulation) test cell samples made of above mentioned TS metal combinations. All test cell samples, prepared and filled with AVT water, were performed at 280 deg. C and 65 bars in an autoclave during 3000 hours. The test cell water temperature has been chosen to be sufficient above the TS component working temperature, in order to accelerate an eventual corrosion process. Generally all above mentioned metal
Energy Technology Data Exchange (ETDEWEB)
Lipa, M.; Blanchet, J. [Association Euratom-CEA Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Cellier, F. [Framatome, Centre Technique, 71 - Saint Marcel (France)
2007-07-01
Full text of publication follows: Tore supra (TS) has used from the beginning of operation in 1989 actively cooled plasma facing components. Since the operation and baking temperature of all in vessel components has been defined to be up to 230 deg. C at 40 bars, a special water chemistry of the cooling water plant was suggested in order to avoid eventual water leaks due to corrosion (general corrosion, galvanic corrosion, stress corrosion, etc.) at relative high temperatures and pressures in tubes, pipes, bellows, water boxes, coils, etc. From the beginning of TS operation, in vessel components (e.g. wall protection panels, limiters, ergodic divertor coils, neutralisers and diagnostics) represented a unique combination of metals in the hydraulic circuit mainly such as stainless steel, Inconel, CuCrZr, Nickel and Copper. These different materials were joined together by welding (St to St, Inconel to Inconel, CuCrZr to CuCrZr and CuCrZr to St-St via a Ni sleeve adapter), brazing (St-St to Cu and Cu-LSTP), friction (CuCrZr and Cu to St-St), explosion (CuCrZr to St-St) and memory metal junction (Cryo-fit to Cu - only test sample). Following experiences obtained with steam generator tubes of nuclear power plants, a cooling water quality of AVT (all volatile treatment) has been defined based on demineralized water with adjustment of the pH value to about 9.0/ 7.0 (25 deg. C/ 200 deg. C) by addiction of ammoniac, and hydrazine in order to absorb oxygen dissolved in water. At that time, a simplified water corrosion test program has been performed using static (no circulation) test cell samples made of above mentioned TS metal combinations. All test cell samples, prepared and filled with AVT water, were performed at 280 deg. C and 65 bars in an autoclave during 3000 hours. The test cell water temperature has been chosen to be sufficient above the TS component working temperature, in order to accelerate an eventual corrosion process. Generally all above mentioned metal
Hancock, Thomas
1993-01-01
This experiment investigated the integrity of static computer memory (floppy disk media) when exposed to the environment of low earth orbit. The experiment attempted to record soft-event upsets (bit-flips) in static computer memory. Typical conditions that exist in low earth orbit that may cause soft-event upsets include: cosmic rays, low level background radiation, charged fields, static charges, and the earth's magnetic field. Over the years several spacecraft have been affected by soft-event upsets (bit-flips), and these events have caused a loss of data or affected spacecraft guidance and control. This paper describes a commercial spin-off that is being developed from the experiment.
Ma, Chengju; Ren, Liyong; Qu, Enshi; Tang, Feng; Liang, Quan
2012-11-01
Based on the force analysis, we establish a theoretical model to study the static pressure distribution of the fiber cable spool for the fiber optic guided missile (FOG-M). Simulations indicate that for each fiber layer in the fiber cable spool, the applied static pressure on it asymptotically converges as the number of fiber layers increases. Using the distributed fiber Bragg grating (FBG) sensing technique, the static pressure of fiber cable layers in the spool on the cable winding device was measured. Experiments show that the Bragg wavelength of FBG in every layer varies very quickly at the beginning and then becomes gently as the subsequent fiber cable was twisted onto the spool layer by layer. Theoretical simulations agree qualitatively with experimental results. This technology provides us a real-time method to monitor the pressure within the fiber cable layer during the cable winding process.
Control of Limit Cycle Oscillations of a Two-Dimensional Aeroelastic System
Directory of Open Access Journals (Sweden)
M. Ghommem
2010-01-01
Full Text Available Linear and nonlinear static feedback controls are implemented on a nonlinear aeroelastic system that consists of a rigid airfoil supported by nonlinear springs in the pitch and plunge directions and subjected to nonlinear aerodynamic loads. The normal form is used to investigate the Hopf bifurcation that occurs as the freestream velocity is increased and to analytically predict the amplitude and frequency of the ensuing limit cycle oscillations (LCO. It is shown that linear control can be used to delay the flutter onset and reduce the LCO amplitude. Yet, its required gains remain a function of the speed. On the other hand, nonlinear control can be effciently implemented to convert any subcritical Hopf bifurcation into a supercritical one and to significantly reduce the LCO amplitude.
AEROELASTIC FLUTTER ANALYSIS OF SUPERSONIC WING WITH MULTIPLE EXTERNAL STORES
Directory of Open Access Journals (Sweden)
Nur Azam
2014-12-01
Full Text Available ABSTRACT: Flutter may be considered to be one of the most dangerous aeroelastic failure phenomenon. The flutter characteristic differs for each aircraft type, and depends on the wing geometry as well as its operational region of subsonic, transonic or supersonic speeds. Prior to performing a flight flutter test, extensive numerical simulations and Ground Vibration Test should be conducted where the structural finite element modes and the experimentation results should be matched, otherwise the numerical simulation model must be rejected. In this paper, the analysis of simulation of a supersonic wing equipped with external missiles loaded on the wing is presented. The structural mode shapes at each generated frequency are also visually presented. The analysis is carried out using MSC Nastran FEM software. The wing flutter with the external stores was simulated at different altitudes. The result shows that the flutter velocity is sensitive to the flight altitude. For this reason, the flutter analysis is conducted also for a negative altitude. The negative altitude is obtained by considering the constant equivalent speed-Mach number rule at the flutter speed boundary as a requirement in standard regulation of transport aircraft. ABSTRAK: Salah satu fenomena kegagalan aeroelastik yang paling membahayakan adalah kipasan (flutter. Ciri-ciri kegagalan kipasan (flutter adalah berbeza untuk setiap jenis pesawat bergantung pada geometri sayap dan regim operasi sama ada subsonik, transonik atau supersonik. Sebelum melakukan ujian penerbangan kipasan , simulasi berangka luas dan ujian getaran peringkat bawahan (darat perlu dijalankan di mana struktur mod unsur terhingga dan keputusan eksperimen harus dipadankan, sebaliknya model simulasi berangka boleh ditolak. Dalam kertas kerja ini, simulasi sayap supersonik dilengkapi dengan beban luaran peluru berpandu di sayap telah dianalisis di daerah supersonik tinggi. Bentuk mod struktur pada setiap mod frekuensi
An aeroelastic stability of the circular cylindrical shells containing a flowing fluid
Directory of Open Access Journals (Sweden)
Sergey A. Bochkarev
2015-12-01
Full Text Available The paper is concerned with the analysis of the panel flutter of circular cylindrical shells containing an ideal compressible liquid and subjected to the external supersonic gas flow. The aerodynamic pressure is calculated based on the quasi-static aerodynamic theory. The behavior of the liquid is described in the framework of the potential theory. Using the Bubnov–Galerkin method, the corresponding wave equation together with the impermeability condition and specified boundary conditions are transformed into the system of equations. The classical shell theory based on the Kirchhoff–Love hypotheses and the principle of virtual displacements are used as the mathematical framework for the elastic structure dynamic problem. A solution to the problem is searched for by a semi-analytical version of the finite element method and involves the calculation of the complex eigenvalues of the coupled system of equations using the Muller-based iterative algorithm. The reliability of the obtained numerical solution of the aeroelastic and hydroelastic stability problem has been estimated by comparing it with the available theoretical data. For shells with different dimensions and variants of boundary conditions the numerical experiments have been performed to estimate the influence of velocity of the internal liquid flow on the value of static pressure in the unperturbed gas flow, which is taken as a variable parameter. It has been found that a growth of liquid velocity causes a change in the flutter type of stability loss. It has been shown that with increase of linear dimensions of the shell the stabilizing effect of the internal liquid flow extending the boundaries of aeroelastic stability changes to the destabilizing effect. Specific values of geometrical dimensions determining the variation in the character of dynamic behavior of the system depend on the prescribed combination of boundary conditions.
Research in aeroelasticity EFP-2007-II
Energy Technology Data Exchange (ETDEWEB)
Buhl, T. (ed.)
2009-06-15
This report contains results from the EFP-2007-II project 'Program for Research in Applied Aeroelasticity'. The main results can be summed up into the following bullets: 1) 2D CFD was used to investigate tower shadow effects on both upwind and downwind turbines, and was used to validate the tower shadow models implemented in the aeroelastic code HAWC2. 2) Using a streamlined tower reduces the tower shadow by 50% compared to a cylindrical tower. Similar reductions can be achieved using a four legged lattice tower. 3) The application of laminar/turbulent transition in CFD computations for airfoils is demonstrated. For attached flow over thin airfoils (18%) 2D computations provide good results while a combination of Detached Eddy Simulation and laminar/ turbulent transition modeling improve the results in stalled conditions for a thick airfoil. 4) The unsteady flow in the nacelle region of a wind turbine is dominated by large flow gradients caused by unsteady shedding of vortices from the root sections of the blades. 5) The averaged nacelle wind speed compares well to the freestream wind speed, whereas the nacelle flow angle is highly sensitive to vertical positioning and tilt in the inflow. 6) The trailing edge noise model, TNO, was implemented and validated. The results showed that the noise was not predicted accurately, but the model captured the trends and can be used in airfoil design. The model was implemented in the airfoil design tool AIRFOILOPT and existing airfoils can be adjusted to maintain the aerodynamic characteristics, but with reduced noise in the order of up to 3dB in total sound power level and up to 1dB with A-weighting. 7) 2D CFD simulations are performed to verify their capability in predicting multi element airfoil configurations. The present computations show good agreement with measured performance from wind tunnel experiments. 8) The stochastic fluctuations of the aerodynamic forces on blades in deep-stall have an insignificant
Aeroelastic Calculations Based on Three-Dimensional Euler Analysis
Bakhle, Milind A.; Srivastava, Rakesh; Keith, Theo G., Jr.; Stefko, George L.
1998-01-01
This paper presents representative results from an aeroelastic code (TURBO-AE) based on an Euler/Navier-Stokes unsteady aerodynamic code (TURBO). Unsteady pressure, lift, and moment distributions are presented for a helical fan test configuration which is used to verify the code by comparison to two-dimensional linear potential (flat plate) theory. The results are for pitching and plunging motions over a range of phase angles, Good agreement with linear theory is seen for all phase angles except those near acoustic resonances. The agreement is better for pitching motions than for plunging motions. The reason for this difference is not understood at present. Numerical checks have been performed to ensure that solutions are independent of time step, converged to periodicity, and linearly dependent on amplitude of blade motion. The paper concludes with an evaluation of the current state of development of the TURBO-AE code and presents some plans for further development and validation of the TURBO-AE code.
Integrated aeroelastic vibrator for fluid mixing in open microwells
Xia, H. M.; Jin, X.; Zhang, Y. Y.; Wu, J. W.; Zhang, J.; Wang, Z. P.
2018-01-01
Fluid mixing in micro-wells/chambers is required in a variety of biological and biochemical processes. However, mixing fluids of small volumes is usually difficult due to increased viscous effects. In this study, we propose a new method for mixing enhancement in microliter-scale open wells. A thin elastic diaphragm is used to seal the bottom of the mixing microwell, underneath which an air chamber connects an aeroelastic vibrator. Driven by an air flow, the vibrator produces self-excited vibrations and causes pressure oscillations in the air chamber. Then the elastic diaphragm is actuated to mix the fluids in the microwell. Two designs that respectively have one single well and 2 × 2 wells were prototyped. Testing results show that for liquids with a volume ranging from 10-60 µl and viscosity ranging from 1-5 cP, complete mixing can be obtained within 5-20 s. Furthermore, the device is operable with an air micropump, and hence facilitating the miniaturization and integration of lab-on-a-chip and microbioreactor systems.
Nguyen, Nhan; Ting, Eric; Lebofsky, Sonia
2015-01-01
This paper presents data analysis of a flexible wing wind tunnel model with a variable camber continuous trailing edge flap (VCCTEF) design for drag minimization tested at the University of Washington Aeronautical Laboratory (UWAL). The wind tunnel test was designed to explore the relative merit of the VCCTEF concept for improved cruise efficiency through the use of low-cost aeroelastic model test techniques. The flexible wing model is a 10%-scale model of a typical transport wing and is constructed of woven fabric composites and foam core. The wing structural stiffness in bending is tailored to be half of the stiffness of a Boeing 757-era transport wing while the torsional stiffness is about the same. This stiffness reduction results in a wing tip deflection of about 10% of the wing semi-span. The VCCTEF is a multi-segment flap design having three chordwise camber segments and five spanwise flap sections for a total of 15 individual flap elements. The three chordwise camber segments can be positioned appropriately to create a desired trailing edge camber. Elastomeric material is used to cover the gaps in between the spanwise flap sections, thereby creating a continuous trailing edge. Wind tunnel data analysis conducted previously shows that the VCCTEF can achieve a drag reduction of up to 6.31% and an improvement in the lift-to-drag ratio (L=D) of up to 4.85%. A method for estimating the bending and torsional stiffnesses of the flexible wingUWAL wind tunnel model from static load test data is presented. The resulting estimation indicates that the stiffness of the flexible wing is significantly stiffer in torsion than in bending by as much as 9 to 1. The lift prediction for the flexible wing is computed by a coupled aerodynamic-structural model. The coupled model is developed by coupling a conceptual aerodynamic tool Vorlax with a finite-element model of the flexible wing via an automated geometry deformation tool. Based on the comparison of the lift curve slope
Model Reduction of Nonlinear Aeroelastic Systems Experiencing Hopf Bifurcation
Abdelkefi, Abdessattar
2013-06-18
In this paper, we employ the normal form to derive a reduced - order model that reproduces nonlinear dynamical behavior of aeroelastic systems that undergo Hopf bifurcation. As an example, we consider a rigid two - dimensional airfoil that is supported by nonlinear springs in the pitch and plunge directions and subjected to nonlinear aerodynamic loads. We apply the center manifold theorem on the governing equations to derive its normal form that constitutes a simplified representation of the aeroelastic sys tem near flutter onset (manifestation of Hopf bifurcation). Then, we use the normal form to identify a self - excited oscillator governed by a time - delay ordinary differential equation that approximates the dynamical behavior while reducing the dimension of the original system. Results obtained from this oscillator show a great capability to predict properly limit cycle oscillations that take place beyond and above flutter as compared with the original aeroelastic system.
Aeroelastic Flutter of Subsonic Aircraft Wing Section with Control Surface
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Aeroelastic Flutter of Subsonic Aircraft Wing Section with Control Surface
2015-12-01
Full Text Available Aeroelastic flutter in aircraft mechanisms is unavoidable, essentially in the wing and control surface. In this work a three degree-of-freedom aeroelastic wing section with trailing edge flap is modeled numerically and theoretically. FLUENT code based on the steady finite volume is used for the prediction of the steady aerodynamic characteristics (lift, drag, pitching moment, velocity, and pressure distribution as well as the Duhamel formulation is used to model the aerodynamic loads theoretically. The system response (pitch, flap pitch and plunge was determined by integration the governing equations using MATLAB with a standard Runge–Kutta algorithm in conjunction with Henon’s method. The results are compared with previous experimental data. The results show that the aerodynamic loads and wing-flap system response are increased when increasing the flow speed. On the other hand the aeroelastic response led up to limit cycle oscillation when the flow equals or more than flutter speed.
Interactive aircraft flight control and aeroelastic stabilization
Weisshaar, T. A.
1985-01-01
Aeroservoelastic optimization techniques were studied to determine a methodology for maximization of the stable flight envelope of an idealized, actively controlled, flexible airfoil. The equations of motion for the airfoil were developed in state-space form to include time-domain representations of aerodynamic forces and active control. The development of an optimization scheme to stabilize the aeroelastic system over a range of airspeeds, including the design airspeed is outlined. The solution approach was divided in two levels: (1) the airfoil structure, with a design variable represented by the shear center position; and (2) the control system. An objective was stated in mathematical form and a search was conducted with the restriction that each subsystem be constrained to be optimal in some sense. Analytical expressions are developed to compute the changes in the eigenvalues of the closed-loop, actively controlled system. A stability index is constructed to ensure that stability is present at the design speed and at other airspeeds away from the design speed.
Eckstrom, C. V.; Spain, C. V.
1982-01-01
Experiences in using composite skin material on an aeroelastic research wing used in flight flutter testing are described. Significant variations in skin shear modulus due to stress and temperature were encountered with the original fiberglass laminate skin designed to minimize wing torsional stiffness. These variations along with the sensitivity of wing torsional stiffness to the skin-to-frame attachment method complicated the structural model vibration mode predictions. A wing skin redesign with different fiber orientation and a reduction in the amount of skin-to-frame bonding resulted in more predictable modal characteristics without sacrificing design objectives. Design and modeling considerations for future applications are discussed.
Shil'ko, S. V.; Gavrilenko, S. L.; Panin, S. V.; Alexenko, V. O.
2017-12-01
A method for determining rheological parameters of the Prony model describing the process of viscoelastic deformation of a material was developed based on the results of dynamic mechanical analysis. For the approbation of the method, static (uniaxial tension) and dynamic (three-point bending) mechanical tests of polymer composites were carried out. Based on the analytical dependence of the storage modulus on the parameters of the Prony model, the parameters of the shear function are determined. The results of the static and dynamic analysis are in good agreement. The proposed technique allows us to accelerate the determination of rheological parameters of polymer materials and recommend it to the calculation of the stress-strain state of structural elements and friction joints during their long operation at elevated temperature.
Aeroelastic Stability of a Four-Bladed Semi-Articulated Soft-Inplane Tiltrotor Model
Nixon, Mark W.; Langston, Chester W.; Singleton, Jeffrey D.; Piatak, David J.; Kvaternik, Raymond G.; Corso, Lawrence M.; Brown, Ross K.
2003-01-01
A new four-bladed, semi-articulated, soft-inplane rotor system, designed as a candidate for future heavy-lift rotorcraft, was tested at model scale on the Wing and Rotor Aeroelastic Testing System (WRATS), a 1/5-size aeroelastic wind-tunnel model based on the V-22. The experimental investigation included a hover test with the model in helicopter mode subject to ground resonance conditions, and a forward flight test with the model in airplane mode subject to whirl-flutter conditions. An active control system designed to augment system damping was also tested as part of this investigation. Results of this study indicate that the new four-bladed, soft-inplane rotor system in hover has adequate damping characteristics and is stable throughout its rotor-speed envelope. However, in airplane mode it produces very low damping in the key wing beam-bending mode, and has a low whirl-flutter stability boundary with respect to airspeed. The active control system was successful in augmenting the damping of the fundamental system modes, and was found to be robust with respect to changes in rotor speed and airspeed. Finally, conversion-mode dynamic loads were measured on the rotor and these were found to be signi.cantly lower for the new soft-inplane hub than for the previous baseline stiff - inplane hub.
Data Comparisons and Summary of the Second Aeroelastic Prediction Workshop
Heeg, Jennifer; Wieseman, Carol D.; Chwalowski, Pawel
2016-01-01
This paper presents the computational results generated by participating teams of the second Aeroelastic Prediction Workshop and compare them with experimental data. Aeroelastic and rigid configurations of the Benchmark Supercritical Wing (BSCW) wind tunnel model served as the focus for the workshop. The comparison data sets include unforced ("steady") system responses, forced pitch oscillations and coupled fluid-structure responses. Integrated coefficients, frequency response functions, and flutter onset conditions are compared. The flow conditions studied were in the transonic range, including both attached and separated flow conditions. Some of the technical discussions that took place at the workshop are summarized.
Static electricity: A literature review
Crow, Rita M.
1991-11-01
The major concern with static electricity is its discharging in a flammable atmosphere which can explode and cause a fire. Textile materials can have their electrical resistivity decreased by the addition of antistatic finishes, imbedding conductive particles into the fibres or by adding metal fibers to the yarns. The test methods used in the studies of static electricity include measuring the static properties of materials, of clothed persons, and of the ignition energy of flammable gases. Surveys have shown that there is sparse evidence for fires definitively being caused by static electricity. However, the 'worst-case' philosophy has been adopted and a static electricity safety code is described, including correct grounding procedures and the wearing of anti-static clothing and footwear.
Directory of Open Access Journals (Sweden)
Nathalie Godin
2016-02-01
Full Text Available Non-oxide fiber-reinforced ceramic-matrix composites are promising candidates for some aeronautic applications that require good thermomechanical behavior over long periods of time. This study focuses on the behavior of a SiCf/[Si-B-C] composite with a self-healing matrix at intermediate temperature under air. Static fatigue experiments were performed below 600 °C and a lifetime diagram is presented. Damage is monitored both by strain measurement and acoustic emission during the static fatigue experiments. Two methods of real-time analysis of associated energy release have been developed. They allow for the identification of a characteristic time that was found to be close to 55% of the measured rupture time. This critical time reflects a critical local energy release assessed by the applicability of the Benioff law. This critical aspect is linked to a damage phase where slow crack growth in fibers is prevailing leading to ultimate fracture of the composite.
Aeroelastic flutter of feathers, flight and the evolution of non-vocal communication in birds.
Clark, Christopher J; Prum, Richard O
2015-11-01
Tonal, non-vocal sounds are widespread in both ordinary bird flight and communication displays. We hypothesized these sounds are attributable to an aerodynamic mechanism intrinsic to flight feathers: aeroelastic flutter. Individual wing and tail feathers from 35 taxa (from 13 families) that produce tonal flight sounds were tested in a wind tunnel. In the wind tunnel, all of these feathers could flutter and generate tonal sound, suggesting that the capacity to flutter is intrinsic to flight feathers. This result implies that the aerodynamic mechanism of aeroelastic flutter is potentially widespread in flight of birds. However, the sounds these feathers produced in the wind tunnel replicated the actual flight sounds of only 15 of the 35 taxa. Of the 20 negative results, we hypothesize that 10 are false negatives, as the acoustic form of the flight sound suggests flutter is a likely acoustic mechanism. For the 10 other taxa, we propose our negative wind tunnel results are correct, and these species do not make sounds via flutter. These sounds appear to constitute one or more mechanism(s) we call 'wing whirring', the physical acoustics of which remain unknown. Our results document that the production of non-vocal communication sounds by aeroelastic flutter of flight feathers is widespread in birds. Across all birds, most evolutionary origins of wing- and tail-generated communication sounds are attributable to three mechanisms: flutter, percussion and wing whirring. Other mechanisms of sound production, such as turbulence-induced whooshes, have evolved into communication sounds only rarely, despite their intrinsic ubiquity in ordinary flight. © 2015. Published by The Company of Biologists Ltd.
State of the art in wind turbine aerodynamics and aeroelasticity
DEFF Research Database (Denmark)
Hansen, Martin Otto Laver; Sørensen, Jens Nørkær; Voutsinas, S
2006-01-01
A comprehensive review of wind turbine aeroelasticity is given. The aerodynamic part starts with the simple aerodynamic Blade Element Momentum Method and ends with giving a review of the work done applying CFD on wind turbine rotors. In between is explained some methods of intermediate complexity...
Parameter estimation of an aeroelastic aircraft using neural networks
Indian Academy of Sciences (India)
Application of neural networks to the problem of aerodynamic modelling and parameter estimation for aeroelastic aircraft is addressed. A neural model capable of predicting generalized force and moment coefficients using measured motion and control variables only, without any need for conventional normal elastic ...
Aeroelastic simulation using CFD based reduced order models
International Nuclear Information System (INIS)
Zhang, W.; Ye, Z.; Li, H.; Yang, Q.
2005-01-01
This paper aims at providing an accurate and efficient method for aeroelastic simulation. System identification is used to get the reduced order models of unsteady aerodynamics. Unsteady Euler codes are used to compute the output signals while 3211 multistep input signals are utilized. LS(Least Squares) method is used to estimate the coefficients of the input-output difference model. The reduced order models are then used in place of the unsteady CFD code for aeroelastic simulation. The aeroelastic equations are marched by an improved 4th order Runge-Kutta method that only needs to compute the aerodynamic loads one time at every time step. The computed results agree well with that of the direct coupling CFD/CSD methods. The computational efficiency is improved 1∼2 orders while still retaining the high accuracy. A standard aeroelastic computing example (isogai wing) with S type flutter boundary is computed and analyzed. It is due to the system has more than one neutral points at the Mach range of 0.875∼0.9. (author)
Aeroelastic Loads Modeling for Composite Aircraft Design Support
Baluch, H.A.
2009-01-01
With regard to the simulation of structural vibrations and consequent aeroelastic loads in aircraft components, the use of elastic axis e.a as reference of vibrations is quite common. The e.a decouples the bending and torsion degrees of freedom (D.o.F) during the dynamic analysis. The use of the e.a
Contribution to finite element modelling of airfoil aeroelastic instabilities
Czech Academy of Sciences Publication Activity Database
Horáček, Jaromír; Sváček, P.; Růžička, M.; Feistauer, M.
2007-01-01
Roč. 1, č. 1 (2007), s. 43-52 ISSN 1802-680X. [Computational Mechanics 2007. Hrad Nečtiny, 05.11.2007-07.11.2007] R&D Projects: GA MPO FT-TA/026 Institutional research plan: CEZ:AV0Z20760514 Keywords : induced vibration * aeroelasticity * nonlinear vibrations Subject RIV: BI - Acoustics
Design and simulation of the rotating test rig in the INDUFLAP project
DEFF Research Database (Denmark)
Barlas, Thanasis K.; Aagaard Madsen, Helge; Løgstrup Andersen, Tom
The general description and objectives of the rotating test rig at the Risø campus of DTU are presented, as used for the aeroelastic testing of a controllable rubber trailing edge flap (CRTEF) system in the INDUFLAP project. The design of all new components is presented, including the electrical...... drive, the pitch system, the boom, and the wing/flap section. The overall instrumentation of the components used for the aeroelastic testing is described. Moreover, the aeroelastic model simulating the setup is described, and predictions of steady and dynamic loading along with the aeroelastic analysis...
Zahouani, H; Pailler-Mattei, C; Sohm, B; Vargiolu, R; Cenizo, V; Debret, R
2009-02-01
The study of changes in skin structure with age is becoming all the more important with the increase in life. The atrophy that occurs during aging is accompanied by more profound changes, with a loss of organization within the elastic collagen network and alterations in the basal elements. The aim of this study is to present a method to determine the mechanical properties of total human skin in vivo compared with dermal equivalents (DEs) using indentation and static friction tests. A new bio-tribometer working at a low contact pressure for the characterization the mechanical properties of the skin has been developed. This device, based on indentation and static friction tests, also allows to characterize the skin in vivo and reconstructed DEs in a wide range of light contact forces, stress and strain. This original bio-tribometer shows the ability to assess the skin elasticity and friction force in a wide range of light normal load (0.5-2 g) and low contact pressure (0.5-2 kPa). The results obtained by this approach show identical values of the Young's modulus E(*) and the shear modulus G(*) of six DEs obtained from a 62-year-old subject (E(*)=8.5+/-1.74 kPa and G(*)=3.3+/-0.46 kPa) and in vivo total skin of 20 subjects aged 55 to 70 years (E(*)=8.3+/-2.1 kPa, G(*)=2.8+/-0.8 kpa).
Gust response analysis and wind tunnel test for a high-aspect ratio wing
Directory of Open Access Journals (Sweden)
Liu Yi
2016-02-01
Full Text Available A theoretical nonlinear aeroelastic response analysis for a flexible high-aspect ratio wing excited by harmonic gust load is presented along with a companion wind tunnel test. A multidisciplinary coupled numerical calculation is developed to simulate the flexible model wing undergoing gust load in the time domain via discrete nonlinear finite element structural dynamic analysis and nonplanar unsteady vortex lattice aerodynamic computation. A dynamic perturbation analysis about a nonlinear static equilibrium is also used to determine the small perturbation flutter boundary. A novel noncontact 3-D camera measurement analysis system is firstly used in the wind tunnel test to obtain the spatial large deformation and responses. The responses of the flexible wing under different static equilibrium states and frequency gust loads are discussed. The fair to good quantitative agreements between the theoretical and experimental results demonstrate that the presented analysis method is an acceptable way to predict the geometrically nonlinear gust response for flexible wings.
Energy Technology Data Exchange (ETDEWEB)
Brezovich, I; Wu, X; Popple, R; Shen, S; Cardan, R; Bolding, M; Fiveash, J; Kraus, J; Spencer, S
2016-06-15
Purpose: To test spatial and dosimetric accuracy of small cranial target irradiation based on 1.5 T MRI scans using static arcs with MLC-defined fields Methods: A plastic (PMMA) phantom simulating a small brain lesion was mounted on a GammaKnife headframe equipped with MRI localizer. The lesion was a 3 mm long, 3.175 mm diameter cylindrical cavity filled with MRI contrast. Radiochromic film passing through the cavity was marked with pin pricks at the cavity center. The cavity was contoured on an MRI image and fused with CT to simulate treatment of a lesion not visible on CT. The transfer of the target to CT involved registering the MRI contrast cannels of the localizer that were visible on both modalities. Treatments were planned to deliver 800 cGy to the cavity center using multiple static arcs with 5.0×2.4 mm MLC-defined fields. The phantom was aligned on a STx accelerator by registering the conebeam CT with the planning CT. Films from coronal and sagittal planes were scanned and evaluated using ImageJ software Results: Geographic errors in treatment based on 1.5 T scans agreed within 0.33, −0.27 and 1.21 mm in the vertical, lateral and longitudinal dimensions, respectively. The doses delivered to the cavity center were 7.2% higher than planned. The dose distributions were similar to those of a GammaKnife. Conclusion: Radiation can be delivered with an accelerator at mm accuracy to small cranial targets based on 1.5 MRI scans fused to CTs using a standard GammaKnife headframe and MRI localizer. MLC-defined static arcs produce isodose lines very similar to the GammaKnife.
National Aeronautics and Space Administration — ZONA Technology, Inc. proposes to develop an integrated flight dynamics simulation capability with nonlinear aeroelastic interactions by combining a flight dynamics...
National Aeronautics and Space Administration — ZONA Technology, Inc. (ZONA) proposes to develop an integrated flight dynamics simulation capability with nonlinear aeroelastic interactions by combining a flight...
Effect of modified aerodynamic strip theories on rotor blade aeroelastic stability
Friedmann, P.; Yuan, C.
1976-01-01
Various existing unsteady aerodynamic strip theories which have been developed in the past for both fixed and rotary wing aeroelastic analyses are modified in the paper so as to make them applicable to the coupled flap-lag-torsional aeroelastic problem of a rotor blade in hover. These corrections are primarily due to constant angle of attack, constant inflow and variable free stream velocity due to lead-lag motion. Next, the modified strip theories are incorporated in a coupled flap-lag-torsional aeroelastic analysis of the rotor blade in hover and the sensitivity of the aeroelastic stability boundaries to the aerodynamic assumptions is examined.
Martos, Borja; Kiszely, Paul; Foster, John V.
2011-01-01
As part of the NASA Aviation Safety Program (AvSP), a novel pitot-static calibration method was developed to allow rapid in-flight calibration for subscale aircraft while flying within confined test areas. This approach uses Global Positioning System (GPS) technology coupled with modern system identification methods that rapidly computes optimal pressure error models over a range of airspeed with defined confidence bounds. This method has been demonstrated in subscale flight tests and has shown small 2- error bounds with significant reduction in test time compared to other methods. The current research was motivated by the desire to further evaluate and develop this method for full-scale aircraft. A goal of this research was to develop an accurate calibration method that enables reductions in test equipment and flight time, thus reducing costs. The approach involved analysis of data acquisition requirements, development of efficient flight patterns, and analysis of pressure error models based on system identification methods. Flight tests were conducted at The University of Tennessee Space Institute (UTSI) utilizing an instrumented Piper Navajo research aircraft. In addition, the UTSI engineering flight simulator was used to investigate test maneuver requirements and handling qualities issues associated with this technique. This paper provides a summary of piloted simulation and flight test results that illustrates the performance and capabilities of the NASA calibration method. Discussion of maneuver requirements and data analysis methods is included as well as recommendations for piloting technique.
Wind Tunnel Testing of the NASA-DFRC Flutterometer using a Two DOF Wing Section
Strganac, Thomas W.
2001-01-01
Flutter of an aeroelastic structure is potentially destructive aeroelastic instability. This phenomenon has motivated research within the aeroelastic community to develop methods that can accurately predict aeroelastic instabilities. The Flutterometer method used herein, and as developed by NASA DFRC, is based upon the mu method which has been coupled with wavelet filtering processes in estimating aeroelastic models from flight data. The approach leads to a methodology to predict the occurrence of flutter boundaries, and may prove to reliably predict flutter boundaries during flight tests. An analytical model is used as the first estimate of the aeroelastic structural dynamics, and uncertainty operators are introduced into the system to model variations between the theoretical system and the physical system. The modelling uncertainties are then updated from experimental data. Although the model used did not work well with this particular experiment, a sensitivity analysis was additionally performed and improvements suggested.
Directory of Open Access Journals (Sweden)
Mansour Imen Ben
2017-01-01
Full Text Available This paper presents an implementation of a data acquisition system for analog-to-digital converters (ADCs using “Laboratory Virtual Instrument Engineering Workbench (LabVIEW” as software for data analysis. The designed and implemented platform allows interaction with the device under test through means of data acquisition and instrument controls. Developing custom tests in LabVIEW can result in reduced test time, which in turn will help reduce costs in testing. This system was developed for evaluation purposes of ADC's static and dynamic parameters (gain error, offset error, DNL, INL, SNR, SINAD, IMD, etc. using single and multi-frequency signals. The virtual control and analysis instrument was created in “LabVIEW” environment to control test signals generation and data acquisition. The testing performance of the platform is demonstrated using the classical ADC circuit “ADC0804”. A comparison with experimental results obtained by CANTEST platform from Bordeaux University (France is also presented to highlight our platform.
A Static Aeroelastic Analysis of a Flexible Wing Mini Unmanned Aerial Vehicle
2008-03-27
sponsoring organization AFRL/ RBCA for the opportunity to work on this fascinating project. I would also like to thank the developers of the Nighthawk, Ap...SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) Dr. Mark Mears, AFRL/ RBCA 2210 8th St, Bldg 146, Rm 305, Wright-Patterson AFB, OH 45433
Mizrah, E. A.; Lobanov, D. K.; Kopylov, E. A.; Balakirev, R. V.; Fedchenko, A. S.
2017-10-01
Performing of the cycle testing according to the principles of Dynamic Stress Test can significantly reduce the overall time of development and production of batteries, which in turn allows reducing the cost of designing and testing of the spacecraft power systems. Performing of Dynamic Stress Test require special charge-discharge units that allows to perform a full cycle of electrical tests of batteries, including cyclic testing. Providing the required accuracy of measurement and stabilization of certain attributes of Li-ion battery operating modes is one of the problems that arise during thedevelopment of such charge-discharge units. The following attributes are of particular interest: charge and discharge currents, discharge powers, battery voltages. Analysis of the charge-discharge unit as a control system allows evaluating the steady-state stabilization error of the required attributes of the developed device. Moreover, using a digital integrator in the control system of the charge-discharge unit allows providing specified values of steady-state stabilization error of required attributes in different test modes.
Aeroelastic tailoring via ribs orientation of NASA Common Research Model
Chan, Y. N.; Harmin, M. Y.; Rafie, A. S. M.
2017-12-01
A baseline model in reference to the NASA Common Research Model is selected to illustrate the concept of aeroelastic tailoring of wing ribs structure by varying the orientation of the ribs. This enables the torsional-bending modes characteristic to be altered, which results in a possibility of improvement in the aeroelastic performance without having to compromise its overall weight. Two strategies are implanted in this work: the first strategy considers the whole ribs to be oriented in parallel while the second one is by dividing the wing into six parts where the ribs are allowed to be oriented in parallel within their part only. In many cases, there are a significant improvement with up to 5.5% of flutter increment via orientating the ribs section, hence leading to a possibility in significant structural weight reduction.
Constructal Theory and Aeroelastic Design of Flexible Flying Wing Aircraft
Directory of Open Access Journals (Sweden)
Pezhman Mardanpour
2017-07-01
Full Text Available The aeroelastic behavior of high-aspect-ratio very flexible flying wing is highly affected by the geometric nonlinearities of the aircraft structure. This paper reviews the findings on how these nonlinearities influence the structural and flight dynamics, and it shows that the aeroelastic flight envelope could significantly be extended with proper choices of design parameters such as engine placement. Moreover, in order to investigate the physics behind the effects of design parameters, constructal theory of design is reviewed. The constructal theory advances the philosophy of design as science, it states that the better structural design emerges when stress flow strangulation is avoided. Furthermore, it shows that airplanes, through their evolution, have obeyed theoretical allometric rules that unite their designs.
A Teaching Experience: Aeroelasticity and the Finite Element Method
Directory of Open Access Journals (Sweden)
Mario Lázaro
2015-07-01
Full Text Available The aeroelastic modelling of aircraft structures is a fundamental area for the students of Aerospace Engineering Degree. This subject has a strongly multidisciplinary character and involves other several subjects like mechanics, vibrations, aerodynamics, structural analysis. Consequently, the students find stimulating the challenge of merging their knowledge at different areas. In this paper, a teaching experience on the solution of the aeroelastic problem of a 3D-wing through six different computer tasks is presented. The main objective is to attempt a relatively complex problem using a simple version of the Finite Element Method with only four degrees of freedom. The students begin creating the shape functions of the discrete model and finish solving the flutter instability problem.
Silva, Walter A.; Sanetrik, Mark D.; Chwalowski, Pawel; Connolly, Joseph; Kopasakis, George
2016-01-01
An overview of recent applications of the FUN3D CFD code to computational aeroelastic, sonic boom, and aeropropulsoservoelasticity (APSE) analyses of a low-boom supersonic configuration is presented. The overview includes details of the computational models developed including multiple unstructured CFD grids suitable for aeroelastic and sonic boom analyses. In addition, aeroelastic Reduced-Order Models (ROMs) are generated and used to rapidly compute the aeroelastic response and utter boundaries at multiple flight conditions.
Unsteady airfoil flows with application to aeroelastic stability
Energy Technology Data Exchange (ETDEWEB)
Johansen, Jeppe
1999-09-01
The present report describes numerical investigation of two-dimensional unsteady airfoil flows with application to aeroelastic stability. The report is divided in two parts. Part A describes the purely aerodynamic part, while Part B includes the aeroelastic part. In Part A a transition prediction algorithm based on a simplified version of the e{sup n} method is proposed. Laminar Boundary Layer instability data are stored in a database from which stability characteristics can be extracted by interpolation. Input to the database are laminar integral boundary layer parameters. These are computed from an integral boundary layer formulation coupled to a Navier-Stokes flow solver. Five different airfoils are considered at fixed angle of attack, and the flow is computed assuming both fully turbulent and transitional flow and compared with experimental data. Results indicate that using a transition model the drag prediction is improved considerably. Also the lift is slightly improved. At high angles of attack transition will affect leading edge separation which again will affect the overall vortex shedding. If the transition point is not properly predicted this will affect the whole hysteresis curve. The transition model developed in the present work showed more stable predictions compared to the empirical transition model. In Part B a simple three degrees-of-freedom (DOF) structural dynamics model is developed and coupled to the aerodynamics models from Part A. A 2nd order accurate time integration scheme is used to solve the equations of motion. Two airfoils are investigated. The aeroelastic models predict stable conditions well at low angle of attack. But at high angles of attack, and where unstable behaviour is expected, only the Navier-Stokes solver predict correct aeroelastic response. The semi-empirical dynamic stall model does not predict vortex shedding and moment correctly leading to an erroneous aerodynamic damping. (au) 5 tabs.; 55 ills., 52 refs.
Aeroelastic deformation of a perforated strip
Guttag, M.; Karimi, H. H.; Falcón, C.; Reis, P. M.
2018-01-01
We perform a combined experimental and numerical investigation into the static deformation of perforated elastic strips under uniform aerodynamic loading at high-Reynolds-number conditions. The static shape of the porous strips, clamped either horizontally or vertically, is quantified as they are deformed by wind loading, induced by a horizontal flow. The experimental profiles are compared to numerical simulations using a reduced model that takes into account the normal drag force on the deformed surface. For both configurations (vertical and horizontal clamping), we compute the drag coefficient of the strip, by fitting the experimental data to the model, and find that it decreases as a function of porosity. Surprisingly, we find that, for every value of porosity, the drag coefficients for the horizontal configuration are larger than those of the vertical configuration. For all data in both configurations, with the exception of the continuous strip clamped vertically, a linear relation is found between the porosity and drag. Making use of this linearity, we can rescale the drag coefficient in a way that it becomes constant as a function of the Cauchy number, which relates the force due to fluid loading on the elastic strip to its bending rigidity, independently of the material properties and porosity of the strip and the flow speed. Our findings on flexible strips are contrasted to previous work on rigid perforated plates. These results highlight some open questions regarding the usage of reduced models to describe the deformation of flexible structures subjected to aerodynamic loading.
Design, realization and structural testing of a compliant adaptable wing
International Nuclear Information System (INIS)
Molinari, G; Arrieta, A F; Ermanni, P; Quack, M; Morari, M
2015-01-01
This paper presents the design, optimization, realization and testing of a novel wing morphing concept, based on distributed compliance structures, and actuated by piezoelectric elements. The adaptive wing features ribs with a selectively compliant inner structure, numerically optimized to achieve aerodynamically efficient shape changes while simultaneously withstanding aeroelastic loads. The static and dynamic aeroelastic behavior of the wing, and the effect of activating the actuators, is assessed by means of coupled 3D aerodynamic and structural simulations. To demonstrate the capabilities of the proposed morphing concept and optimization procedure, the wings of a model airplane are designed and manufactured according to the presented approach. The goal is to replace conventional ailerons, thus to achieve controllability in roll purely by morphing. The mechanical properties of the manufactured components are characterized experimentally, and used to create a refined and correlated finite element model. The overall stiffness, strength, and actuation capabilities are experimentally tested and successfully compared with the numerical prediction. To counteract the nonlinear hysteretic behavior of the piezoelectric actuators, a closed-loop controller is implemented, and its capability of accurately achieving the desired shape adaptation is evaluated experimentally. Using the correlated finite element model, the aeroelastic behavior of the manufactured wing is simulated, showing that the morphing concept can provide sufficient roll authority to allow controllability of the flight. The additional degrees of freedom offered by morphing can be also used to vary the plane lift coefficient, similarly to conventional flaps. The efficiency improvements offered by this technique are evaluated numerically, and compared to the performance of a rigid wing. (paper)
International Nuclear Information System (INIS)
Jesus Miranda, C.A. de.
1992-01-01
An integrated 3-D model of a research PWR reactor core support internals structures was developed for its dynamic analyses. The static tests for the validation of the model are presented. There are about 90 super-elements with, approximately, 85000 degrees of freedom (DoF), 8200 masters DoF, 12000 elements with about 8400 thin shell elements. A DEC VAX computer 11/785 model and the ANSYS program were used. If impacts occurs the spectral seismic analysis will be changed to a non-linear one with direct integration of the displacement pulse derived from the seismic accelerogram. This last will be obtained from the seismic acceleration response spectra. (author)
Stuart, Keith; Bartosh, Blake
1993-01-01
Innovative Information Systems (IIS), Inc. is in the process of designing and fabricating a high bandwidth force and moment measuring device (i.e. the Magnetic Thruster Test Stand). This device will use active magnetic suspension to allow direct measurements of the forces and torques generated by the rocket engines of the missile under test. The principle of operation of the Magnetic Thruster Test Stand (MTTS) is based on the ability to perform very precise, high bandwidth force and position measurements on an object suspended in a magnetic field. This ability exists due to the fact that the digital servo control mechanism that performs the magnetic suspension uses high bandwidth (10 kHz) position data (via an eddy-current proximity sensor) to determine the amount of force required to maintain stable suspension at a particular point. This force is converted into required electromagnet coil current, which is then output to a current amplifier driving the coils. A discussion of how the coil current and magnetic gap distance (the distance between the electromagnet and the object being suspended) is used to determine the forces being applied from the suspended assembly is presented.
Design gridlines for integrated aeroelastic control of wind turbines - Task-12 report
DEFF Research Database (Denmark)
Mogensen, T.S.; Larsen, A.J.; Poulsen, N.K.
The presented design guidelines for active aeroelastic control of PRVS wind turbines are derived by the partners of the project - Aeroelastic Stability and Control of Large Wind Turbines” (STABCON) partially funded by the European Commission (EC) under the contract NNK5-CT2002-00627. The objective...... of this successful long term research cooperation....
Jutte, Christine; Stanford, Bret K.
2014-01-01
This paper provides a brief overview of the state-of-the-art for aeroelastic tailoring of subsonic transport aircraft and offers additional resources on related research efforts. Emphasis is placed on aircraft having straight or aft swept wings. The literature covers computational synthesis tools developed for aeroelastic tailoring and numerous design studies focused on discovering new methods for passive aeroelastic control. Several new structural and material technologies are presented as potential enablers of aeroelastic tailoring, including selectively reinforced materials, functionally graded materials, fiber tow steered composite laminates, and various nonconventional structural designs. In addition, smart materials and structures whose properties or configurations change in response to external stimuli are presented as potential active approaches to aeroelastic tailoring.
Tolba, Khaled Ibrahim; Morgenthal, Guido
2018-01-01
This paper presents an analysis of the scalability and efficiency of a simulation framework based on the vortex particle method. The code is applied for the numerical aerodynamic analysis of line-like structures. The numerical code runs on multicore CPU and GPU architectures using OpenCL framework. The focus of this paper is the analysis of the parallel efficiency and scalability of the method being applied to an engineering test case, specifically the aeroelastic response of a long-span bridge girder at the construction stage. The target is to assess the optimal configuration and the required computer architecture, such that it becomes feasible to efficiently utilise the method within the computational resources available for a regular engineering office. The simulations and the scalability analysis are performed on a regular gaming type computer.
Parameter identification of aeroelastic modes of rotary wings from transient time histories
Amrani, Ahmed Omar; Du Val, Ronald
1990-01-01
A novel moving-block technique is presented for parameter-identification tasks concerning the aeroelastic modes of rotary wings, using a least-squares solver in the time domain to estimate dampings and eigenvector components. The least-squares moving-block (LSMB) technique is shown to yield superior estimates to those of the previous moving-block technique for four different analytical test cases. An additional advantage of the LSMB approach is its ability to estimate eigenvector components with good accuracy; this feature is useful in assessing the coupling of the different modes. The method can also be used to perform periodic modal identification, and is applicable to experimental data for the extraction of modal information.
International Nuclear Information System (INIS)
Arias, F.; Soria, E.
1996-01-01
This report shows the methods and procedures selected to define a strength test for large size wind turbine, anyway in particularly it application on a 500 kW blade and it results obtained in the test carried out in july of 1995 in Asinel test plant (Madrid). Henceforth, this project is designed in an abbreviate form whit the acronym SFAT. (Author)
Energy Technology Data Exchange (ETDEWEB)
Arias, F.; Soria, E.
1996-12-01
This report shows the methods and procedures selected to define a strength test for large size wind turbine, anyway in particular it application on a 500 kW blade and it results obtained in the test carried out in july of 1995 in Asinel`s test plant (Madrid). Henceforth, this project is designed in an abbreviate form whit the acronym SFAT. (Author)
Parallel Aeroelastic Analysis Using ENSAERO and NASTRAN
Eldred, Lloyd B.; Byun, Chansup; Guruswamy, Guru P.
1999-01-01
A high fidelity parallel static structural analysis capability is created and interfaced to the multidisciplinary analysis package ENSAERO-MPI of Ames Research Center. This new module replaced ENSAERO's lower fidelity simple finite element and modal modules. Full aircraft structures may be more accurately modeled using the new finite element capability. Parallel computation is performed by breaking the full structure into multiple substructures. This approach is conceptually similar to ENSAERO's multi-zonal fluid analysis capability. The new substructure code is used to solve the structural finite element equations for each substructure in parallel. NASTRAN/COSMIC is utilized as a front end for this code. Its full library of elements can be used to create an accurate and realistic aircraft mode. It is used to create the stiffness matrices for each sub-structure. The new parallel code then uses an iterative preconditioned conjugate gradient method to solve the global structural equations for the sub-structure boundary nodes. Results are presented for a wing-body configuration.
Bisplinghoff, Raymond L; Pian, Theodore HH
2014-01-01
Profusely illustrated exposition of fundamentals of solid mechanics and principles of mechanics, statics, and simple statically indeterminate systems. Covers strain and stress in three-dimensional solids, elementary elasticity, energy principles in solid continuum, and more. 1965 edition.
GAROS, an aeroelastic code for coupled fixed-rotating structures
Energy Technology Data Exchange (ETDEWEB)
Rees, M. [Aerodyn Energiestyseme GmbH, Rendsburg (Germany); Vollan, A. [Pilatus Flugzeugwerke, Stans (Switzerland)
1996-09-01
The GAROS (General Analysis of Rotating Structures) program system has been specially designed to calculate aeroelastic stability and dynamic response of horizontal axis wind energy converters. Nevertheless it is also suitable for the dynamic analysis of helicopter rotors and has been used in the analysis of car bodies taking account of rotating wheels. GAROS was developed over the last 17 years. In the following the mechanical and the aerodynamic model will be discussed in detail. A short overview of the solution methods for the equation of motion in time and frequency domain will ge given. After this one example for the FEM model of the rotor and tower will be discussed. (EG)
NRT Rotor Structural / Aeroelastic Analysis for the Preliminary Design Review
Energy Technology Data Exchange (ETDEWEB)
Ennis, Brandon Lee [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Paquette, Joshua A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2015-10-01
This document describes the initial structural design for the National Rotor Testbed blade as presented during the preliminary design review at Sandia National Laboratories on October 28- 29, 2015. The document summarizes the structural and aeroelastic requirements placed on the NRT rotor for satisfactory deployment at the DOE/SNL SWiFT experimental facility to produce high-quality datasets for wind turbine model validation. The method and result of the NRT blade structural optimization is also presented within this report, along with analysis of its satisfaction of the design requirements.
Aeroelastic analysis of an adaptive trailing edge with a smart elastic skin
Arena, Maurizio; Pecora, Rosario; Amoroso, Francesco; Noviello, Maria Chiara; Rea, Francesco; Concilio, Antonio
2017-09-01
Nowadays, the design choices of the new generation aircraft are moving towards the research and development of innovative technologies, aimed at improving performance as well as to minimize the environmental impact. In the current "greening" context, the morphing structures represent a very attractive answer to such requirements: both aerodynamic and structural advantages are ensured in several flight conditions, safeguarding the fuel consumption at the same time. An aeronautical intelligent system is therefore the outcome of combining complex smart materials and structures, assuring the best functionality level in the flight envelope. The Adaptive Trailing Edge Device (ATED) is a sub-project inside SARISTU (Smart Intelligent Aircraft Structures), an L2 level project of the 7th EU Framework programme coordinated by Airbus, aimed at developing technologies for realizing a morphing wing extremity addressed to improve the general aircraft performance and to reduce the fuel burning up to 5%. This specific study, divided into design, manufacturing and testing phases, involved universities, research centers and leading industries of the European consortium. The paper deals with the aeroelastic impact assessment of a full-scale morphing wing trailing edge on a Large Aeroplanes category aircraft. The FE (Finite Element) model of the technology demonstrator, located in the aileron region and manufactured within the project, was referenced to for the extrapolation of the structural properties of the whole adaptive trailing edge device placed in its actual location in the outer wing. The input FE models were processed within MSC-Nastran® environment to estimate stiffness and inertial distributions suitable to construct the aeroelastic stick-beam mock-up of the reference structure. Afterwards, a flutter analysis in simulated operative condition, have been carried out by means of Sandy®, an in-house code, according to meet the safety requirements imposed by the applicable
DEFF Research Database (Denmark)
Bayati, I.; Belloli, M.; Bernini, L.
2016-01-01
This paper illustrates the aero-elastic optimal design, the realization and the verification of the wind tunnel scale model blades for the DTU 10 MW wind turbine model, within LIFES50+ project. The aerodynamic design was focused on the minimization of the difference, in terms of thrust coefficient...... and for different angles of attack. The aero-elastic design algorithm was set to define the optimal spanwise thickness over chord ratio (t/c), the chord length and the twist to match the first flapwise scaled natural frequency. An aluminium mould for the carbon fibre was CNC manufactured based on B-Splines CAD...... definition of the external geometry. Then the wind tunnel tests at Politecnico di Milano confirmed successful design and manufacturing approaches....
Hernádi, László; László, János F
2014-07-01
To study the effect of single, 30-min long, whole-body, homogeneous static magnetic field (SMF)-exposure of magnetic induction 147 ± 3 mT on the response latency of the snail Helix pomatia. The response was investigated using the hot plate test. The effect caused by exposure to SMF was compared to sham-exposure and resulted in significant differences (up to 47.1%, p < 0.001). The response latency depended on the day-night cycle; response latency was higher by 51.2% (p < 0.001) during the night. This trend also held for SMF-exposure (28.6%, p < 0.001). Serotonin alone increased response latency (55.7%, p < 0.001), whereas serotonin antagonist tryptamine decreased it (- 97.8%, p < 0.001). Using naloxone, response latency decreased (- 52.5%, p < 0.001); however both SMF-exposure and serotonin in combination with naloxone rose it back to above the control level (116.9%, p < 0.001 or 150.2%, p < 0.001, respectively). This study provides evidence that SMF-exposure mediates peripheral thermal nociceptive threshold by affecting the serotonerg as well as the opioiderg system.
Thimm, Jens C
2017-12-01
The Computerized Adaptive Test of Personality Disorder-Static Form (CAT-PD-SF) is a self-report inventory developed to assess pathological personality traits. The current study explored the reliability and higher order factor structure of the Norwegian version of the CAT-PD-SF and the relationships between the CAT-PD traits and domains of personality functioning in an undergraduate student sample ( N = 375). In addition to the CAT-PD-SF, the short form of the Severity Indices of Personality Problems and the Brief Symptom Inventory were administered. The results showed that the Norwegian CAT-PD-SF has good score reliability. Factor analysis of the CAT-PD-SF scales indicated five superordinate factors that correspond to the trait domains of the alternative DSM-5 model for personality disorders. The CAT-PD traits were highly predictive of impaired personality functioning after controlling for psychological distress. It is concluded that the CAT-PD-SF is a promising tool for the assessment of personality disorder traits.
Kvaternik, Raymond G.; Piatak, David J.; Nixon, Mark W.; Langston, Chester W.; Singleton, Jeffrey D.; Bennett, Richard L.; Brown, Ross K.
2001-01-01
The results of a joint NASA/Army/Bell Helicopter Textron wind-tunnel test to assess the potential of Generalized Predictive Control (GPC) for actively controlling the swashplate of tiltrotor aircraft to enhance aeroelastic stability in the airplane mode of flight are presented. GPC is an adaptive time-domain predictive control method that uses a linear difference equation to describe the input-output relationship of the system and to design the controller. The test was conducted in the Langley Transonic Dynamics Tunnel using an unpowered 1/5-scale semispan aeroelastic model of the V-22 that was modified to incorporate a GPC-based multi-input multi-output control algorithm to individually control each of the three swashplate actuators. Wing responses were used for feedback. The GPC-based control system was highly effective in increasing the stability of the critical wing mode for all of the conditions tested, without measurable degradation of the damping in the other modes. The algorithm was also robust with respect to its performance in adjusting to rapid changes in both the rotor speed and the tunnel airspeed.
Nonlinear Time Delayed Feedback Control of Aeroelastic Systems: A Functional Approach
Marzocca, Piergiovanni; Librescu, Liviu; Silva, Walter A.
2003-01-01
In addition to its intrinsic practical importance, nonlinear time delayed feedback control applied to lifting surfaces can result in interesting aeroelastic behaviors. In this paper, nonlinear aeroelastic response to external time-dependent loads and stability boundary for actively controlled lifting surfaces, in an incompressible flow field, are considered. The structural model and the unsteady aerodynamics are considered linear. The implications of the presence of time delays in the linear/nonlinear feedback control and of geometrical parameters on the aeroelasticity of lifting surfaces are analyzed and conclusions on their implications are highlighted.
First-order aerodynamic and aeroelastic behavior of a single-blade installation setup
DEFF Research Database (Denmark)
Gaunaa, Mac; Bergami, Leonardo; Guntur, Srinivas
2014-01-01
the first-order aerodynamic and aeroelastic behavior of a single blade installation system, where the blade is grabbed by a yoke, which is lifted by the crane and stabilized by two taglines. A simple engineering model is formulated to describe the aerodynamic forcing on the blade subject to turbulent wind...... of arbitrary direction. The model is coupled with a schematic aeroelastic representation of the taglines system, which returns the minimum line tension required to compensate for the aerodynamic forcing. The simplified models are in excellent agreement with the aeroelastic code HAWC2, and provide a solid basis...
Aeroelastic Ground Wind Loads Analysis Tool for Launch Vehicles
Ivanco, Thomas G.
2016-01-01
Launch vehicles are exposed to ground winds during rollout and on the launch pad that can induce static and dynamic loads. Of particular concern are the dynamic loads caused by vortex shedding from nearly-cylindrical structures. When the frequency of vortex shedding nears that of a lowly-damped structural mode, the dynamic loads can be more than an order of magnitude greater than mean drag loads. Accurately predicting vehicle response to vortex shedding during the design and analysis cycles is difficult and typically exceeds the practical capabilities of modern computational fluid dynamics codes. Therefore, mitigating the ground wind loads risk typically requires wind-tunnel tests of dynamically-scaled models that are time consuming and expensive to conduct. In recent years, NASA has developed a ground wind loads analysis tool for launch vehicles to fill this analytical capability gap in order to provide predictions for prelaunch static and dynamic loads. This paper includes a background of the ground wind loads problem and the current state-of-the-art. It then discusses the history and significance of the analysis tool and the methodology used to develop it. Finally, results of the analysis tool are compared to wind-tunnel and full-scale data of various geometries and Reynolds numbers.
Linearized FUN3D for Rapid Aeroelastic and Aeroservoelastic Design and Analysis, Phase I
National Aeronautics and Space Administration — The overall objective of this Phase I project is to develop a hybrid approach in FUN3D, referred herein to as the Linearized FUN3D, for rapid aeroelastic and...
Novel Reduced Order in Time Models for Problems in Nonlinear Aeroelasticity, Phase I
National Aeronautics and Space Administration — Research is proposed for the development and implementation of state of the art, reduced order models for problems in nonlinear aeroelasticity. Highly efficient and...
National Aeronautics and Space Administration — The need to accurately predict aeroelastic phenomenon for a wide range of Mach numbers is a critical step in the design process of any aerospace vehicle. Complex...
National Aeronautics and Space Administration — The need to accurately predict aeroelastic phenomenon for a wide range of Mach numbers is a critical step in the design process of any aerospace vehicle. Complex...
A pragmatic approach to including complex natural modes of vibration in aeroelastic analysis
CSIR Research Space (South Africa)
Van Zyl, Lourens H
2015-09-01
Full Text Available would be generated due to the movement of the structure. This presentation concerns mainly the structural dynamic component of the aeroelastic problem, and specifically the structural damping forces (which is usually not mentioned in the definition...
National Aeronautics and Space Administration — Stirling Dynamics Inc and the University of Washington propose to develop a MATLAB toolbox for rapid aeroelastic (AE) and aeroservoelastic (ASE) modeling, analysis...
Efficient Method for Aeroelastic Tailoring of Composite Wing to Minimize Gust Response
Directory of Open Access Journals (Sweden)
Yang Yu
2017-01-01
Full Text Available Aeroelastic tailoring of laminated composite structure demands relatively high computational time especially for dynamic problem. This paper presents an efficient method for aeroelastic dynamic response analysis with significantly reduced computational time. In this method, a relationship is established between the maximum aeroelastic response and quasi-steady deflection of a wing subject to a dynamic loading. Based on this relationship, the time consuming dynamic response can be approximated by a quasi-steady deflection analysis in a large proportion of the optimization process. This method has been applied to the aeroelastic tailoring of a composite wing of a tailless aircraft for minimum gust response. The results have shown that 20%–36% gust response reduction has been achieved for this case. The computational time of the optimization process has been reduced by 90% at the cost of accuracy reduction of 2~4% comparing with the traditional dynamic response analysis.
Static balance and developmental coordination disorder
Geuze, RH
2003-01-01
The development of static balance is a basic characteristic of normal motor development. Most of the developmental motor tests include a measure of static balance. Children with a developmental coordination disorder (DCD) often fail this item. Twenty-four children at risk for DCD with balance
Static Analysis Numerical Algorithms
2016-04-01
STATIC ANALYSIS OF NUMERICAL ALGORITHMS KESTREL TECHNOLOGY, LLC APRIL 2016 FINAL TECHNICAL REPORT APPROVED FOR PUBLIC RELEASE; DISTRIBUTION...3. DATES COVERED (From - To) NOV 2013 – NOV 2015 4. TITLE AND SUBTITLE STATIC ANALYSIS OF NUMERICAL ALGORITHMS 5a. CONTRACT NUMBER FA8750-14-C...and Honeywell Aerospace Advanced Technology to combine model-based development of complex avionics control software with static analysis of the
Static electromagnetic frequency changers
Rozhanskii, L L
1963-01-01
Static Electromagnetic Frequency Changers is about the theory, design, construction, and applications of static electromagnetic frequency changers, devices that used for multiplication or division of alternating current frequency. It is originally published in the Russian language. This book is organized into five chapters. The first three chapters introduce the readers to the principles of operation, the construction, and the potential applications of static electromagnetic frequency changers and to the principles of their design. The two concluding chapters use some hitherto unpublished work
National Aeronautics and Space Administration — ZONA proposes a phase II effort to fully develop a comprehensive methodology for aeroelastic predictions of the nonlinear aerodynamic/aerothermodynamic - structure...
National Aeronautics and Space Administration — The proposed research program will develop a physics-based identification, modeling and risk management infrastructure for aeroelastic transonic flutter and...
National Aeronautics and Space Administration — ASSURE - Aeroelastic / Aeroservoelastic (AE/ASE) Uncertainty and Reliability Engineering capability - is a set of probabilistic computer programs for isolating...
The aeroelastic code HawC - model and comparisons
Energy Technology Data Exchange (ETDEWEB)
Thirstrup Petersen, J. [Risoe National Lab., The Test Station for Wind Turbines, Roskilde (Denmark)
1996-09-01
A general aeroelastic finite element model for simulation of the dynamic response of horizontal axis wind turbines is presented. The model has been developed with the aim to establish an effective research tool, which can support the general investigation of wind turbine dynamics and research in specific areas of wind turbine modelling. The model concentrates on the correct representation of the inertia forces in a form, which makes it possible to recognize and isolate effects originating from specific degrees of freedom. The turbine structure is divided into substructures, and nonlinear kinematic terms are retained in the equations of motion. Moderate geometric nonlinearities are allowed for. Gravity and a full wind field including 3-dimensional 3-component turbulence are included in the loading. Simulation results for a typical three bladed, stall regulated wind turbine are presented and compared with measurements. (au)
A Highly Accurate Approach for Aeroelastic System with Hysteresis Nonlinearity
Directory of Open Access Journals (Sweden)
C. C. Cui
2017-01-01
Full Text Available We propose an accurate approach, based on the precise integration method, to solve the aeroelastic system of an airfoil with a pitch hysteresis. A major procedure for achieving high precision is to design a predictor-corrector algorithm. This algorithm enables accurate determination of switching points resulting from the hysteresis. Numerical examples show that the results obtained by the presented method are in excellent agreement with exact solutions. In addition, the high accuracy can be maintained as the time step increases in a reasonable range. It is also found that the Runge-Kutta method may sometimes provide quite different and even fallacious results, though the step length is much less than that adopted in the presented method. With such high computational accuracy, the presented method could be applicable in dynamical systems with hysteresis nonlinearities.
On the way to reliable aeroelastic load simulation on VAWT's
DEFF Research Database (Denmark)
Larsen, Torben J.; Aagaard Madsen, Helge
2013-01-01
In this paper a method for an implementation of a 2D actuator cylinder flow model of an Vertical Axis Wind Turbine (VAWT) is presented. The model is implemented in a full aeroelastic code including consideration of structural dynamics, dynamic inflow, tower shadow and dynamic stall, which is needed...... for a full load analysis relating to eg. certification of a VAWT turbine. Further on, principal load cases according to the IEC61400-1 are simulated for a fictitious 5MW VAWT turbine in it’s simplest 2 bladed Darrieus configuration. The IEC61400-1 load cases, originally developed for Horizontal Axis Wind...... Turbines (HAWT’s), are discussed regarding the application to VAWT’s. Further on a small section regarding aerodynamic flow in curved motion is included....
Directory of Open Access Journals (Sweden)
Roberto da Cunha Follador
2016-04-01
Full Text Available The Operational Modal Analysis technique is a methodology very often applied for the identification of dynamic systems when the input signal is unknown. The applied methodology is based on a technique to estimate the Frequency Response Functions and extract the modal parameters using only the structural dynamic response data, without assuming the knowledge of the excitation forces. Such approach is an adequate way for measuring the aircraft aeroelastic response due to random input, like atmospheric turbulence. The in-flight structural response has been measured by accelerometers distributed along the aircraft wings, fuselage and empennages. The Enhanced Frequency Domain Decomposition technique was chosen to identify the airframe dynamic parameters. This technique is based on the hypothesis that the system is randomly excited with a broadband spectrum with almost constant power spectral density. The system identification procedure is based on the Single Value Decomposition of the power spectral densities of system output signals, estimated by the usual Fast Fourier Transform method. This procedure has been applied to different flight conditions to evaluate the modal parameters and the aeroelastic stability trends of the airframe under investigation. The experimental results obtained by this methodology were compared with the predicted results supplied by aeroelastic numerical models in order to check the consistency of the proposed output-only methodology. The objective of this paper is to compare in-flight measured aeroelastic damping against the corresponding parameters computed from numerical aeroelastic models. Different aerodynamic modeling approaches should be investigated such as the use of source panel body models, cruciform and flat plate projection. As a result of this investigation it is expected the choice of the better aeroelastic modeling and Operational Modal Analysis techniques to be included in a standard aeroelastic
Static Analysis of Mobile Programs
2017-02-01
and not allowed, to do. The second issue was that a fully static analysis was never a realistic possibility, because Java , the programming langauge...not justified by the test data). This idea came to define the project: use dynamic analyiss to guess the correct properties a program points of interest...scale to large programs it had to handle essentially all of the features of Java and could also be used as a general-purpose analysis engine. The
Martian Atmospheric Pressure Static Charge Elimination Tool
Johansen, Michael R.
2014-01-01
A Martian pressure static charge elimination tool is currently in development in the Electrostatics and Surface Physics Laboratory (ESPL) at NASA's Kennedy Space Center. In standard Earth atmosphere conditions, static charge can be neutralized from an insulating surface using air ionizers. These air ionizers generate ions through corona breakdown. The Martian atmosphere is 7 Torr of mostly carbon dioxide, which makes it inherently difficult to use similar methods as those used for standard atmosphere static elimination tools. An initial prototype has been developed to show feasibility of static charge elimination at low pressure, using corona discharge. A needle point and thin wire loop are used as the corona generating electrodes. A photo of the test apparatus is shown below. Positive and negative high voltage pulses are sent to the needle point. This creates positive and negative ions that can be used for static charge neutralization. In a preliminary test, a floating metal plate was charged to approximately 600 volts under Martian atmospheric conditions. The static elimination tool was enabled and the voltage on the metal plate dropped rapidly to -100 volts. This test data is displayed below. Optimization is necessary to improve the electrostatic balance of the static elimination tool.
14 CFR 33.64 - Pressurized engine static parts.
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Pressurized engine static parts. 33.64... engine static parts. (a) Strength. The applicant must establish by test, validated analysis, or a combination of both, that all static parts subject to significant gas or liquid pressure loads for a...
Deets, D. A.; Brown, L. E.
1986-01-01
The highly maneuverable aircraft technology (HiMAT) program explored the various and complex interactions of advanced technologies, such as aeroelastic tailoring, close-coupled canard, and relaxed static stability. A 0.44-subscale remotely piloted research vehicle (RPRV) of a hypothetical fighter airplane was designed and flight-tested to determine the effects of these interactions and to define the design techniques appropriate for advanced fighter technologies. Flexibility and high maneuverability were provided by flight control laws implemented in ground-based computers and telemetered to the vehicle control system during flight tests. The high quality of the flight-measured data and their close correlation with the analytical design modeling proved that the RPRV is a viable and cost-effective tool for developing aerodynamic, structure, and control law requirements for highly maneuverable fighter airplanes of the future.
DEFF Research Database (Denmark)
Aagaard Madsen, Helge; Larsen, Torben J.; Schmidt Paulsen, Uwe
2013-01-01
The paper presents the implementation of the Actuator Cylinder (AC) flow model in the HAWC2 aeroelastic code originally developed for simulation of Horizontal Axis Wind Turbine (HAWT) aeroelasticity. This is done within the DeepWind project where the main objective is to explore the competitivene...
Shen, Jinwei
A comprehensive aeroelastic analytical model of helicopter rotors with trailing-edge flaps for primary and vibration controls has been developed. The derivation of system equations is based on Hamilton principles, and implemented with finite element method in space and time. The blade element consists of fifteen degrees of freedom representing blade flap, lag, torsional, and axial deformations. Three aerodynamic models of flapped airfoils were implemented in the present analysis, the unsteady Hariharan-Leishman model for trailing-edge flaps without aerodynamic balance, a quasi-steady Theodorsen theory for an aerodynamic balanced trailing-edge flap, and table lookup based on wind tunnel test data. The trailing-edge flap deflections may be modeled as a degree of freedom so that the actuator dynamics can be captured properly. The coupled trim procedures for swashplateless rotor are solved in either wind tunnel trim or free flight condition. A multicyclic controller is also implemented to calculate the flap control inputs for minimization of vibratory rotor hub loads. The coupled blade equations of motion are linearized by using small perturbations about a steady trimmed solution. The aeroelastic stability characteristics of trailing-edge flap rotors is then determined from an eigenanalysis of the homogeneous equations using Floquet method. The correlation studies of a typical bearingless rotor and an ultralight teetering rotor are respectively based on wind tunnel test data and simulations of another comprehensive analysis (CAMRAD II). Overall, good correlations are obtained. Parametric study identifies that the effect of actuator dynamics cannot be neglected, especially for a torsionally soft smart actuator system. Aeroelastic stability characteristics of a trailing-edge flap rotor system are shown to be sensitive to flap aerodynamic and mass balances. Key parameters of trailing-edge flap system for primary rotor control are identified as blade pitch index angle
Three-Dimensional CST Parameterization Method Applied in Aircraft Aeroelastic Analysis
Directory of Open Access Journals (Sweden)
Hua Su
2017-01-01
Full Text Available Class/shape transformation (CST method has advantages of adjustable design variables and powerful parametric geometric shape design ability and has been widely used in aerodynamic design and optimization processes. Three-dimensional CST is an extension for complex aircraft and can generate diverse three-dimensional aircraft and the corresponding mesh automatically and quickly. This paper proposes a parametric structural modeling method based on gridding feature extraction from the aerodynamic mesh generated by the three-dimensional CST method. This novel method can create parametric structural model for fuselage and wing and keep the coordination between the aerodynamic mesh and the structural mesh. Based on the generated aerodynamic model and structural model, an automatic process for aeroelastic modeling and solving is presented with the panel method for aerodynamic solver and NASTRAN for structural solver. A reusable launch vehicle (RLV is used to illustrate the process for aeroelastic modeling and solving. The result shows that this method can generate aeroelastic model for diverse complex three-dimensional aircraft automatically and reduce the difficulty of aeroelastic analysis dramatically. It provides an effective approach to make use of the aeroelastic analysis at the conceptual design phase for modern aircraft.
Directory of Open Access Journals (Sweden)
Pezhman Mardanpour
2015-01-01
Full Text Available Energy efficiency plays important role in aeroelastic design of flying wing aircraft and may be attained by use of lightweight structures as well as solar energy. NATASHA (Nonlinear Aeroelastic Trim And Stability of HALE Aircraft is a newly developed computer program which uses a nonlinear composite beam theory that eliminates the difficulties in aeroelastic simulations of flexible high-aspect-ratio wings which undergoes large deformation, as well as the singularities due to finite rotations. NATASHA has shown that proper engine placement could significantly increase the aeroelastic flight envelope which typically leads to more flexible and lighter aircraft. The areas of minimum kinetic energy for the lower frequency modes are in accordance with the zones with maximum flutter speed and have the potential to save computational effort. Another aspect of energy efficiency for High Altitude, Long Endurance (HALE drones stems from needing to minimize energy consumption because of limitations on the source of energy, that is, solar power. NATASHA is capable of simulating the aeroelastic passive morphing maneuver (i.e., morphing without relying on actuators and at as near zero energy cost as possible of the aircraft so as the solar panels installed on the wing are in maximum exposure to sun during different time of the day.
Aeroelastic Uncertainty Quantification Studies Using the S4T Wind Tunnel Model
Nikbay, Melike; Heeg, Jennifer
2017-01-01
This paper originates from the joint efforts of an aeroelastic study team in the Applied Vehicle Technology Panel from NATO Science and Technology Organization, with the Task Group number AVT-191, titled "Application of Sensitivity Analysis and Uncertainty Quantification to Military Vehicle Design." We present aeroelastic uncertainty quantification studies using the SemiSpan Supersonic Transport wind tunnel model at the NASA Langley Research Center. The aeroelastic study team decided treat both structural and aerodynamic input parameters as uncertain and represent them as samples drawn from statistical distributions, propagating them through aeroelastic analysis frameworks. Uncertainty quantification processes require many function evaluations to asses the impact of variations in numerous parameters on the vehicle characteristics, rapidly increasing the computational time requirement relative to that required to assess a system deterministically. The increased computational time is particularly prohibitive if high-fidelity analyses are employed. As a remedy, the Istanbul Technical University team employed an Euler solver in an aeroelastic analysis framework, and implemented reduced order modeling with Polynomial Chaos Expansion and Proper Orthogonal Decomposition to perform the uncertainty propagation. The NASA team chose to reduce the prohibitive computational time by employing linear solution processes. The NASA team also focused on determining input sample distributions.
Research in aeroelasticity EFP-2002; Forskning i aeroelasticitet EFP-2002
Energy Technology Data Exchange (ETDEWEB)
Bak, Christian (ed.)
2004-02-01
This report contains results from the Energy Research Project 'Application, demonstration and further development of advanced aerodynamic and aeroelastic models' (EFP 2002), covering the time from July 1 2002 to December 31 2003. The partners in the project are Risoe National Labo-ratory (Risoe), The Technical University of Denmark (DTU), Bonus Energy A/S, LM Glasfiber A/S, NEG Micon A/S og Vestas Wind Systems A/S. In the project, Risoe and DTU have de-monstrated the application of their advanced computational methods on several different mega-Watt-size wind turbine designs. Compared to traditional methods the advanced methods have among other results shown: 1) that the aerodynamics at the blade tip for a wind turbine cannot be analysed correctly for a non-rotating blade. 2) that the drag coefficient distribution on a rotor in stand still according to Computational Fluid Dynamics should be increased from the blade root towards the blade tip. 3) that the maximum 2D lift coefficient in airfoil characteristics should be reduced at the blade tip and should be increased significantly on the inner part of the rotor. The drag coefficients should in general be increased for all sections on the blade, when the flow is separating. 4) that the choice of airfoil characteristics, aerodynamical as well as structural, are impor-tant for the loads, the noise and the design of a wind turbine. 5) that blade edgewise vibrations in stand still computed with an aeroelastic code are most critical around 40 deg. and 140 deg. angles of attack and that these vibrations depend completely on the given values of lift and drag. 6) that the energy production decreases in the case of large deflections of the blades. 7) that the blade flap eigenfrequency increases in the case of large deflections. 8) that there is an increased coupling between blade edge and blade torsional frequency in the case of large deflections. 9) that an overview of the dynamics for a wind turbine design can be
Aeroelastic modal dynamics of wind turbines including anisotropic effects
Energy Technology Data Exchange (ETDEWEB)
Fisker Skjoldan, P.
2011-03-15
Several methods for aeroelastic modal analysis of a rotating wind turbine are developed and used to analyse the modal dynamics of two simplified models and a complex model in isotropic and anisotropic conditions. The Coleman transformation is used to enable extraction of the modal frequencies, damping, and periodic mode shapes of a rotating wind turbine by describing the rotor degrees of freedom in the inertial frame. This approach is valid only for an isotropic system. Anisotropic systems, e.g., with an unbalanced rotor or operating in wind shear, are treated with the general approaches of Floquet analysis or Hill's method which do not provide a unique reference frame for observing the modal frequency, to which any multiple of the rotor speed can be added. This indeterminacy is resolved by requiring that the periodic mode shape be as constant as possible in the inertial frame. The modal frequency is thus identified as the dominant frequency in the response of a pure excitation of the mode observed in the inertial frame. A modal analysis tool based directly on the complex aeroelastic wind turbine code BHawC is presented. It uses the Coleman approach in isotropic conditions and the computationally efficient implicit Floquet analysis in anisotropic conditions. The tool is validated against system identifications with the partial Floquet method on the nonlinear BHawC model of a 2.3 MW wind turbine. System identification results show that nonlinear effects on the 2.3 MW turbine in most cases are small, but indicate that the controller creates nonlinear damping. In isotropic conditions the periodic mode shape contains up to three harmonic components, but in anisotropic conditions it can contain an infinite number of harmonic components with frequencies that are multiples of the rotor speed. These harmonics appear in calculated frequency responses of the turbine. Extreme wind shear changes the modal damping when the flow is separated due to an interaction between
International Nuclear Information System (INIS)
Medjber, Salim; Bekkar, Hacene; Menouar, Salah; Ryeol Choi, Jeong
2016-01-01
The relationship between quantum mechanics and classical mechanics is investigated by taking a Gaussian-type wave packet as a solution of the Schrödinger equation for the Caldirola–Kanai oscillator driven by a sinusoidal force. For this time-dependent system, quantum properties are studied by using the invariant theory of Lewis and Riesenfeld. In particular, we analyze time behaviors of quantum expectation values of position and momentum variables and compare them to those of the counterpart classical ones. Based on this, we check whether the Ehrenfest theorem which was originally developed in static quantum systems can be extended to such time-varying systems without problems. (paper)
Batterson, Sidney A.
1959-01-01
An experimental investigation was made at the Langley landing loads track to obtain data on the maximum spin-up coefficients of friction developed by a landing gear having a static-load rating of 20,000 pounds. The forward speeds ranged from 0 to approximately 180 feet per second and the sinking speeds, from 2.7 feet per second to 9.4 feet per second. The results indicated the variation of the maximum spin-up coefficient of friction with forward speed and vertical load. Data obtained during this investigation are also compared with some results previously obtained for nonrolling tires to show the effect of forward speed.
Preliminary aeroelastic assessment of a large aeroplane equipped with a camber-morphing aileron
Pecora, Rosario; Amoroso, Francesco; Palumbo, Rita; Arena, Maurizio; Amendola, Gianluca; Dimino, Ignazio
2017-04-01
The development of adaptive morphing wings has been individuated as one of the crucial topics in the greening of the next generation air transport. Research programs have been lunched and are still running worldwide to exploit the potentials of morphing concepts in the optimization of aircraft efficiency and in the consequent reduction of fuel burn. In the framework of CRIAQ MDO 505, a joint Canadian and Italian research project, an innovative camber morphing architecture was proposed for the aileron of a reference civil transportation aircraft; aileron shape adaptation was conceived to increase roll control effectiveness as well as to maximize overall wing efficiency along a typical flight mission. Implemented structural solutions and embedded systems were duly validated by means of ground tests carried out on a true scale prototype. Relying upon the experimental modes of the device in free-free conditions, a rational analysis was carried out in order to investigate the impacts of the morphing aileron on the aeroelastic stability of the reference aircraft. Flutter analyses were performed in compliance with EASA CS-25 airworthiness requirements and referring -at first- to nominal aileron functioning. In this way, safety values for aileron control harmonic and degree of mass-balance were defined to avoid instabilities within the flight envelope. Trade-off analyses were finally addressed to justify the robustness of the adopted massbalancing as well as the persistence of the flutter clearance in case of relevant failures/malfunctions of the morphing system components.
Evolution of Coextruded Structures in Static Mixers
Sollogoub, C.; Guinault, A.; Pedros, M.
2007-04-01
Coextrusion allows to combine two thermoplastics in different ways, creating structures with different cross-sectional geometries (side-by-side structure or concentric ring structure). We use static mixers after the feedblock, in order to homogenise these initial structures and obtain different blend morphologies. The control of these morphologies is of prime importance in order to predict the final properties of the polymer blends. The aim of this paper is to study the evolution of some initial coextruded structures in different static mixers. Different static mixers, with adjustable number of mixing elements, are tested. The experimental observations are confronted with numerical simulation results.
Directory of Open Access Journals (Sweden)
Debrégeas G.
2010-06-01
Full Text Available We present the results of recent friction experiments in which a MEMS-based sensing device is used to measure both the normal and tangential stress ﬁelds at the base of a rough elastomer ﬁlm in frictional contact with smooth, rigid, glass indentors. We consider successively multicontacts under (i static normal loading by a spherical indentor and (ii frictional steady sliding conditions against a cylindrical indentor, for an increasing normal load. In both cases, the measured ﬁelds are compared to elastic calculations assuming (i a smooth interface and (ii Amontons’ friction law. In the static case, signiﬁcant deviations are observed which decrease with increasing load and which vanish when a lubricant is used. In the steady sliding case, Amontons’ law reproduces rather satisfactorily the experiments provided that the normal/tangential coupling at the contact interface is taken into account. We discuss the origin of the diﬀerence between the Amontons ﬁelds and the measured ones, in particular the eﬀect of the ﬁnite normal and tangential compliances of the multicontact interface.
Observing the Forces Involved in Static Friction under Static Situations
Kaplan, Daniel
2013-01-01
Static friction is an important concept in introductory physics. Later in the year students apply their understanding of static friction under more complex conditions of static equilibrium. Traditional lab demonstrations in this case involve exceeding of the maximum level of static friction, resulting in the "onset of motion." (Contains…
Control Application of Piezoelectric Materials to Aeroelastic Self-Excited Vibrations
Directory of Open Access Journals (Sweden)
Mohammad Amin Rashidifar
2014-01-01
Full Text Available A method for application of piezoelectric materials to aeroelasticity of turbomachinery blades is presented. The governing differential equations of an overhung beam are established. The induced voltage in attached piezoelectric sensors due to the strain of the beam is calculated. In aeroelastic self-excited vibrations, the aerodynamic generalized force of a specified mode can be described as a linear function of the generalized coordinate and its derivatives. This simplifies the closed loop system designed for vibration control of the corresponding structure. On the other hand, there is an industrial interest in measurement of displacement, velocity, acceleration, or a contribution of them for machinery condition monitoring. Considering this criterion in quadratic optimal control systems, a special style of performance index is configured. Utilizing the current relations in an aeroelastic case with proper attachment of piezoelectric elements can provide higher margin of instability and lead to lower vibration magnitude.
Directory of Open Access Journals (Sweden)
Wan Zhiqiang
2014-04-01
Full Text Available An aeroelastic two-level optimization methodology for preliminary design of wing structures is presented, in which the parameters for structural layout and sizes are taken as design variables in the first-level optimization, and robust constraints in conjunction with conventional aeroelastic constraints are considered in the second-level optimization. A low-order panel method is used for aerodynamic analysis in the first-level optimization, and a high-order panel method is employed in the second-level optimization. It is concluded that the design of the abovementioned structural parameters of a wing can be improved using the present method with high efficiency. An improvement is seen in aeroelastic performance of the wing obtained with the present method when compared to the initial wing. Since these optimized structures are obtained after consideration of aerodynamic and structural uncertainties, they are well suited to encounter these uncertainties when they occur in reality.
Low-order aeroelastic models of wind turbines for controller design
DEFF Research Database (Denmark)
Sønderby, Ivan Bergquist
Wind turbine controllers are used to optimize the performance of wind turbines such as to reduce power variations and fatigue and extreme loads on wind turbine components. Accurate tuning and design of modern controllers must be done using low-order models that accurately captures the aeroelastic...... response of the wind turbine. The purpose of this thesis is to investigate the necessary model complexity required in aeroelastic models used for controller design and to analyze and propose methods to design low-order aeroelastic wind turbine models that are suited for model-based control design...... stall using only few states. A set of reduced-order models obtained at various operating points are shown to be easily connected by interpolation and are thereby suited for gain-scheduling control design. A new method is proposed to reduce separately the number of structural and aerodynamic states...
Nano-ADEPT Aeroloads Wind Tunnel Test
Smith, Brandon; Yount, Bryan; Kruger, Carl; Brivkalns, Chad; Makino, Alberto; Cassell, Alan; Zarchi, Kerry; McDaniel, Ryan; Ross, James; Wercinski, Paul;
2016-01-01
A wind tunnel test of the Adaptable Deployable Entry and Placement Technology (ADEPT) was conducted in April 2015 at the US Army's 7 by10 Foot Wind Tunnel located at NASA Ames Research Center. Key geometric features of the fabric test article were a 0.7 meter deployed base diameter, a 70 degree half-angle forebody cone angle, eight ribs, and a nose-to-base radius ratio of 0.7. The primary objective of this wind tunnel test was to obtain static deflected shape and pressure distributions while varying pretension at dynamic pressures and angles of attack relevant to entry conditions at Earth, Mars, and Venus. Other objectives included obtaining aerodynamic force and moment data and determining the presence and magnitude of any dynamic aeroelastic behavior (buzz/flutter) in the fabric trailing edge. All instrumentation systems worked as planned and a rich data set was obtained. This paper describes the test articles, instrumentation systems, data products, and test results. Four notable conclusions are drawn. First, test data support adopting a pre-tension lower bound of 10 foot pounds per inch for Nano-ADEPT mission applications in order to minimize the impact of static deflection. Second, test results indicate that the fabric conditioning process needs to be reevaluated. Third, no flutter/buzz of the fabric was observed for any test condition and should also not occur at hypersonic speeds. Fourth, translating one of the gores caused ADEPT to generate lift without the need for a center of gravity offset. At hypersonic speeds, the lift generated by actuating ADEPT gores could be used for vehicle control.
Efficient computation of aerodynamic influence coefficients for aeroelastic analysis on a transputer network
Janetzke, David C.; Murthy, Durbha V.
1991-01-01
Aeroelastic analysis is multi-disciplinary and computationally expensive. Hence, it can greatly benefit from parallel processing. As part of an effort to develop an aeroelastic capability on a distributed memory transputer network, a parallel algorithm for the computation of aerodynamic influence coefficients is implemented on a network of 32 transputers. The aerodynamic influence coefficients are calculated using a 3-D unsteady aerodynamic model and a parallel discretization. Efficiencies up to 85 percent were demonstrated using 32 processors. The effect of subtask ordering, problem size, and network topology are presented. A comparison to results on a shared memory computer indicates that higher speedup is achieved on the distributed memory system.
Optimal Topology of Aircraft Rib and Spar Structures under Aeroelastic Loads
Stanford, Bret K.; Dunning, Peter D.
2014-01-01
Several topology optimization problems are conducted within the ribs and spars of a wing box. It is desired to locate the best position of lightening holes, truss/cross-bracing, etc. A variety of aeroelastic metrics are isolated for each of these problems: elastic wing compliance under trim loads and taxi loads, stress distribution, and crushing loads. Aileron effectiveness under a constant roll rate is considered, as are dynamic metrics: natural vibration frequency and flutter. This approach helps uncover the relationship between topology and aeroelasticity in subsonic transport wings, and can therefore aid in understanding the complex aircraft design process which must eventually consider all these metrics and load cases simultaneously.
Quick Method for Aeroelastic and Finite Element Modeling of Wind Turbine Blades
DEFF Research Database (Denmark)
Bennett, Jeffrey; Bitsche, Robert; Branner, Kim
2014-01-01
In this paper a quick method for modeling composite wind turbine blades is developed for aeroelastic simulations and finite element analyses. The method reduces the time to model a wind turbine blade by automating the creation of a shell finite element model and running it through a cross...... the user has two models of the same blade, one for performing a structural finite element model analysis and one for aeroelastic simulations. Here, the method is implemented and applied to reverse engineer a structural layup for the NREL 5MW reference blade. The model is verified by comparing natural...
The influence of turbulence on the aero-elastic instability of wind turbines
DEFF Research Database (Denmark)
Zhang, Zili; Nielsen, Søren R.K.
2014-01-01
calibrated to the NREL 5 MW baseline wind turbine. Aeroelastic stability of the wind turbine system has been evaluated for various values of the rated generator torque, the rated rotational speed of the rotor, the mean wind speed and the turbulence intensity. Critical turbulence intensity, at which the wind...... turbine shifts from a stable state into an instable state, is determined in different cases. Results show that turbulence intensity has significant influence on the aeroelastic stability of high-performance wind turbines operating close to stall, and the stability of the wind turbine might be changed due...
Messerle, H K; Declaris, Nicholas
2013-01-01
Energy Conversion Statics deals with equilibrium situations and processes linking equilibrium states. A development of the basic theory of energy conversion statics and its applications is presented. In the applications the emphasis is on processes involving electrical energy. The text commences by introducing the general concept of energy with a survey of primary and secondary energy forms, their availability, and use. The second chapter presents the basic laws of energy conversion. Four postulates defining the overall range of applicability of the general theory are set out, demonstrating th
DEFF Research Database (Denmark)
Damian, Daniel; Danvy, Olivier
2001-01-01
Starting from an operational specification of a translation from a structured to an unstructured imperative language, we point out how a compositional and context-insensitive translation gives rise to static chains of jumps. Taking an inspiration from the notion of continuation, we state a new...... compositional and context-sensitive specification that provably gives rise to no static chains of jumps, no redundant labels, and no unused labels. It is defined with one inference rule per syntactic construct and operates in linear time and space on the size of the source program (indeed it operates in one...
DEFF Research Database (Denmark)
Nielsen, Christoffer Rosenkilde; Nielson, Hanne Riis
2006-01-01
operation blinding. In this paper we study the theoretical foundations for one of the successful approaches to validating cryptographic protocols and we extend it to handle the blinding primitive. Our static analysis approach is based on Flow Logic; this gives us a clean separation between the specification...
DEFF Research Database (Denmark)
Danvy, Olivier; Damian, Daniel
2001-01-01
Starting from an operational specification of a translation from a structured to an unstructured imperative language, we point out how a compositional and context-insensitive translation gives rise to static chains of jumps. Taking an inspiration from the notion of continuation, we state a new co...
Naab, Laurie; Henry, David
2009-01-01
Using Wiggins and McTighe's (1998) concept of Big Ideas, the authors planned and designed an electricity investigation to address common student misconceptions about static electricity. With Styrofoam plates and transparent tape, elementary students investigated many properties of electrically charged and uncharged objects in a 5E learning cycle…
Explosions and static electricity
DEFF Research Database (Denmark)
Jonassen, Niels M
1995-01-01
The paper deals with the problem of electrostatic discharges as causes of ignition of vapor/gas and dust/gas mixtures. A series of examples of static-caused explosions will be discussed. The concepts of explosion limits, the incendiveness of various discharge types and safe voltages are explained...
Proposed Wind Turbine Aeroelasticity Studies Using Helicopter Systems Analysis
Ladkany, Samaan G.
1998-01-01
Advanced systems for the analysis of rotary wing aeroelastic structures (helicopters) are being developed at NASA Ames by the Rotorcraft Aeromechanics Branch, ARA. The research has recently been extended to the study of wind turbines, used for electric power generation Wind turbines play an important role in Europe, Japan & many other countries because they are non polluting & use a renewable source of energy. European countries such as Holland, Norway & France have been the world leaders in the design & manufacture of wind turbines due to their historical experience of several centuries, in building complex wind mill structures, which were used in water pumping, grain grinding & for lumbering. Fossil fuel cost in Japan & in Europe is two to three times higher than in the USA due to very high import taxes. High fuel cost combined with substantial governmental subsidies, allow wind generated power to be competitive with the more traditional sources of power generation. In the USA, the use of wind energy has been limited mainly because power production from wind is twice as expensive as from other traditional sources. Studies conducted at the National Renewable Energy Laboratories (NREL) indicate that the main cost in the production of wind turbines is due to the materials & the labor intensive processes used in the construction of turbine structures. Thus, for the US to assume world leadership in wind power generation, new lightweight & consequently very flexible wind turbines, that could be economically mass produced, would have to be developed [4,5]. This effort, if successful, would result in great benefit to the US & the developing nations that suffer from overpopulation & a very high cost of energy.
Investigation of two pitot-static tubes at supersonic speeds
Hasel, Lowell E; Coletti, Donald E
1948-01-01
The results of tests at a Mach number of 1.94 of an ogives-nose cylindrical pitot-static tube and similar tests at Mach numbers of 1.93 and 1.62 of a service pitot-static tube to determine body static pressures and indicated Mach numbers are presented and discussed. The radial pressure distribution on the cylindrical bodies is compared with that calculated by an approximate theory.
Effects of extreme wind shear on aeroelastic modal damping of wind turbines
DEFF Research Database (Denmark)
Skjoldan, P.F.; Hansen, Morten Hartvig
2013-01-01
Wind shear is an important contributor to fatigue loads on wind turbines. Because it causes an azimuthal variation in angle of attack, it can also affect aerodynamic damping. In this paper, a linearized model of a wind turbine, based on the nonlinear aeroelastic code BHawC, is used to investigate...
Aeroelastic Optimization of a 10 MW Wind Turbine Blade with Active Trailing Edge Flaps
DEFF Research Database (Denmark)
Barlas, Athanasios; Tibaldi, Carlo; Zahle, Frederik
2016-01-01
This article presents the aeroelastic optimization of a 10MW wind turbine ‘smart blade’ equipped with active trailing edge flaps. The multi-disciplinary wind turbine analysis and optimization tool HawtOpt2 is utilized, which is based on the open-source framework Open-MDAO. The tool interfaces to ...
Low-fidelity 2D isogeometric aeroelastic optimization with application to a morphing airfoil
Gillebaart, E.; De Breuker, R.
2015-01-01
Low-fidelity isogeometric aeroelastic analysis has not received much attention since the introduction of the isogeometric analysis (IGA) concept, while the combination of IGA and the boundary element method in the form of the potential flow theory shows great potential. This paper presents a
Aeroelastic experiments with measurement of the kinematic properties based on optical methods
Czech Academy of Sciences Publication Activity Database
Chládek, Štěpán; Zolotarev, Igor
2015-01-01
Roč. 21, č. 1 (2015), s. 43-53 ISSN 1803-9782 R&D Projects: GA ČR GA13-10527S Institutional support: RVO:61388998 Keywords : aeroelasticity * optical measurements * vibration frequencies * kinematic properties * profile in the wind tunnel Subject RIV: BI - Acoustics
Development and Analysis of a Swept Blade Aeroelastic Model for a Small Wind Turbine (Presentation)
Energy Technology Data Exchange (ETDEWEB)
Preus, R.; Damiani, R.; Lee, S.; Larwood, S.
2014-06-01
As part of the U.S. Department-of-Energy-funded Competitiveness Improvement Project, the National Renewable Energy Laboratory (NREL) developed new capabilities for aeroelastic modeling of precurved and preswept blades for small wind turbines. This presentation covers the quest for optimized rotors, computer-aided engineering tools, a case study, and summary of the results.
Aeroelastic tailoring using lamination parameters : Drag reduction of a Formula One rear wing
Thuwis, G.A.A.; De Breuker, R.; Abdalla, M.M.; Gürdal, Z.
2009-01-01
The aim of the present work is to passively reduce the induced drag of the rear wing of a Formula One car at high velocity through aeroelastic tailoring. The angle-of-attack of the rear wing is fixed and is determined by the required downforce needed to get around a turn. As a result, at higher
Semi-analytical method for calculating aeroelastic effect of profiled rod flying at high velocity
Directory of Open Access Journals (Sweden)
Hui-jun Ning
2015-03-01
Full Text Available The key technique of a kinetic energy rod (KER warhead is to control the flight attitude of rods. The rods are usually designed to different shapes. A new conceptual KER named profiled rod which has large L/D ratio is described in this paper. The elastic dynamic equations of this profiled rod flying at high velocity after detonation are set up on the basis of Euler-Bernoulli beam, and the aeroelastic deformation of profiled rod is calculated by semi-analytical method for calculating the vibration characteristics of variable cross-section beam. In addition, the aeroelastic deformation of the undeformed profiled rod and the aeroelastic deformation of deformed profiled rod which is caused by the detonation of explosive are simulated by computational fluid dynamic and finite element method (CFD/FEM, respectively. A satisfactory agreement of these two methods is obtained by the comparison of two methods. The results show that the semi-analytical method for calculating the vibration characteristics of variable cross-section beam is applied to analyze the aeroelastic deformation of profiled rod flying at high velocity.
Donnell, K.O.; Schober, S.; Stolk, M.; Marzocca, P.; De Breuker, R.; Abdalla, M.; Nicolini, E.; Gürdal, Z.
2007-01-01
This paper discusses modeling, simulations and experimental aspects of active aeroelastic control on aircraft wings by using Synthetic Jet Actuators (SJAs). SJAs, a particular class of zero-net mass-flux actuators, have shown very promising results in numerous aeronautical applications, such as
DEFF Research Database (Denmark)
Damgaard, Mads; Andersen, Lars Vabbersgaard; Ibsen, Lars Bo
2015-01-01
-parameter model fitted to the frequency response of the ground, a surface foundation is implemented into the aeroelastic code FLEX5. In case of a horizontal stratum overlaying a homogeneous half-space and within the low frequency range, analyses show that a standard lumped-parametermodel provides an accurate...
Aeroelastic Limit-Cycle Oscillations resulting from Aerodynamic Non-Linearities
van Rooij, A.C.L.M.
2017-01-01
Aerodynamic non-linearities, such as shock waves, boundary layer separation or boundary layer transition, may cause an amplitude limitation of the oscillations induced by the fluid flow around a structure. These aeroelastic limit-cycle oscillations (LCOs) resulting from aerodynamic non-linearities
Energy Technology Data Exchange (ETDEWEB)
Robinson, Brandon [Carleton Univ., Ottawa, ON (Canada). Dept. of Civil and Environmental Engineering; Rocha da Costa, Leandro Jose [Carleton Univ., Ottawa, ON (Canada). Dept. of Civil and Environmental Engineering; Poirel, Dominique [Royal Military College of Canada, Kingston (Canada). Dept. of Mechanical and Aerospace Engineering; Pettit, Chris [US Naval Academy, Annapolis, MD (United States). Dept. of Mechanical and Aerospace Engineering; Khalil, Mohammad [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Sarkar, Abhijit [Carleton Univ., Ottawa, ON (Canada). Dept. of Civil and Environmental Engineering
2017-09-01
Our study details the derivation of the nonlinear equations of motion for the axial, biaxial bending and torsional vibrations of an aeroelastic cantilever undergoing rigid body (pitch) rotation at the base. The primary attenstion is focussed on the geometric nonlinearities of the system, whereby the aeroelastic load is modeled by the theory of linear quasisteady aerodynamics. This modelling effort is intended to mimic the wind-tunnel experimental setup at the Royal Military College of Canada. While the derivation closely follows the work of Hodges and Dowell [1] for rotor blades, this aeroelastic system contains new inertial terms which stem from the fundamentally different kinematics than those exhibited by helicopter or wind turbine blades. Using the Hamilton’s principle, a set of coupled nonlinear partial differential equations (PDEs) and an ordinary differential equation (ODE) are derived which describes the coupled axial-bending-bending-torsion-pitch motion of the aeroelastic cantilever with the pitch rotation. The finite dimensional approximation of the coupled system of PDEs are obtained using the Galerkin projection, leading to a coupled system of ODEs. Subsequently, these nonlinear ODEs are solved numerically using the built-in MATLAB implicit ODE solver and the associated numerical results are compared with those obtained using Houbolt’s method. It is demonstrated that the system undergoes coalescence flutter, leading to a limit cycle oscillation (LCO) due to coupling between the rigid body pitching mode and teh flexible mode arising from the flapwise bending motion.
Blades Forced Vibration Under Aero-Elastic Excitation Modeled by Van der Pol
Czech Academy of Sciences Publication Activity Database
Půst, Ladislav; Pešek, Luděk
2017-01-01
Roč. 27, č. 11 (2017), č. článku 1750166. ISSN 0218-1274 R&D Projects: GA ČR GA16-04546S Institutional support: RVO:61388998 Keywords : ade vibration * aero-elastic force * self-excitation * van der Pol Subject RIV: BI - Acoustics OBOR OECD: Applied mechanics Impact factor: 1.329, year: 2016
OC3 -- Benchmark Exercise of Aero-Elastic Offshore Wind Turbine Codes: Preprint
Energy Technology Data Exchange (ETDEWEB)
Passon, P.; Kuhn, M.; Butterfield, S.; Jonkman, J.; Camp, T.; Larsen, T. J.
2007-08-01
This paper introduces the work content and status of the first international investigation and verification of aero-elastic codes for offshore wind turbines as performed by the "Offshore Code Comparison Collaboration" (OC3) within the "IEA Wind Annex XXIII -- Subtask 2".
Ferede, E.A.
2016-01-01
There is a growth in the energy consumption of the world, leading to rapid depletion of natural resources, such as fossil fuels. Added to that, the environmental impact of fossil fuels (e.g. global warming) makes a renewable source of energy a better alternative for power generation. Among renewable
Static and dynamic thyroid scintigraphy
International Nuclear Information System (INIS)
Mahlstedt, J.
1986-01-01
Static images as isolated investigation in thyroid diagnosis mainly provides morphologic information, and therefore sonography is largely applied for this purpose. 99m Tc-pertechnetate scans or 123 I-scans are indicated in cases of malpositions and serve to clarify lesions of unknown dignity. Additionally 201 Tl-chloride is suited for examinations with regard to metabolically active thyroid tissue, whereby differential diagnostic laboratory tests must be carried out to exclude parathyroid adenoma. Dynamic thyroid scans before and after regulation tests (suppression, stimulation) reflect the physiological correlation between the iodine avidity of the thyroid, the peripheral thyroid hormone concentrations and the hypophyseal regulation in the TRH-test. The main application of this procedure is the clarification of thyroid autonomy, i.e. indication, detection, quantification or exclusion of thyroid autonomy. For the treatment of immunogenic thyrotoxicosis, dynamic thyroid scintigraphy provides important information about the onset of remission, thus permitting to end thyreostatic therapy. (orig.) [de
Static Behaviour of Bucket Foundations
DEFF Research Database (Denmark)
Larsen, Kim André
theory is proposed. The proposed expression applies to plane strain as well as axis-symmetric stress conditions for foundations with smooth or rough bases. A thorough experimental investigation of the static behaviour of bucket foundations subjected to combined loading is carried out. Laboratory tests...... as well as large-scale tests on bucket foundations subjected to low vertical load are performed during this work. Numerical simulations of the tests performed are carried out using the Mohr Coulomb material model and the commercial finite element code ABAQUS. Based on the present work, the finite element...... method is concluded to be a superior method in estimating the post peak behaviour as well as the combined capacity of bucket foundations in relation to the offshore wind turbine problem....
Application of CFD based wave loads in aeroelastic calculations
DEFF Research Database (Denmark)
Schløer, Signe; Paulsen, Bo Terp; Bredmose, Henrik
2014-01-01
domain decomposed potentialflow CFD solver result in different dynamic forces in the tower and monopile, despite that the static forces on a fixed monopile are similar. The changes are due to differences in the force profiles and wave steepness in the two solvers. The results indicate that an accurate...
Energy Technology Data Exchange (ETDEWEB)
Doessing, M.
2011-05-15
During the last decades the annual energy produced by wind turbines has increased dramatically and wind turbines are now available in the 5MW range. Turbines in this range are constantly being developed and it is also being investigated whether turbines as large as 10-20MW are feasible. The design of very large machines introduces new problems in the practical design, and optimization tools are necessary. These must combine the dynamic effects of both aerodynamics and structure in an integrated optimization environment. This is referred to as aeroelastic optimization. The Risoe DTU optimization software HAWTOPT has been used in this project. The quasi-steady aerodynamic module have been improved with a corrected blade element momentum method. A structure module has also been developed which lays out the blade structural properties. This is done in a simplified way allowing fast conceptual design studies and with focus on the overall properties relevant for the aeroelastic properties. Aeroelastic simulations in the time domain were carried out using the aeroelastic code HAWC2. With these modules coupled to HAWTOPT, optimizations have been made. In parallel with the developments of the mentioned numerical modules, focus has been on analysis and a fundamental understanding of the key parameters in wind turbine design. This has resulted in insight and an effective design methodology is presented. Using the optimization environment a 5MW wind turbine rotor has been optimized for reduced fatigue loads due to apwise bending moments. Among other things this has indicated that airfoils for wind turbine blades should have a high lift coefficient. The design methodology proved to be stable and a help in the otherwise challenging task of numerical aeroelastic optimization. (Author)
DEFF Research Database (Denmark)
Tishin, A.M.; Spichkin, Yu.I.; Bohr, Jakob
1999-01-01
to the appearance of anomalies in elastic constants, as well as to additional damping of sound oscillations in the lanthanide materials. The importance of understanding the nature of magnetoelastic interactions and related effects arises from the scientific desire to gather a better knowledge of magnetism, as well......In this chapter we shall consider the properties of lanthanide metals, their alloys and compounds which can be studied using static and alternating mechanical stresses. The main attention will be paid to the effects related to magnetoelastic interactions. These interactions in magnetic materials...... can display themselves in static magnetostriction deformations (this effect is not considered here) and in the changing of the magnetic state under mechanical stress. The latter causes variation of the magnetic phase transition temperatures, magnetization and magnetic structures, and leads...
Design, Manufacture and Testing of A Bend-Twist D-Spar
Energy Technology Data Exchange (ETDEWEB)
Ong, Cheng-Huat; Tsai, Stephen W.
1999-06-01
Studies have indicated that an adaptive wind turbine blade design can significantly enhance the performance of the wind turbine blade on energy capture and load mitigation. In order to realize the potential benefits of aeroelastic tailoring, a bend-twist D-spar, which is the backbone of a blade, was designed and fabricated to achieve the objectives of having maximum bend-twist coupling and fulfilling desirable structural properties (031 & GJ). Two bend-twist D-spars, a hybrid of glass and carbon fibers and an all-carbon D-spar, were fabricated using a bladder process. One of the D-spars, the hybrid D-spar, was subjected to a cantilever static test and modal testing. Various parameters such as materials, laminate schedule, thickness and internal rib were examined in designing a bend-twist D-spar. The fabrication tooling, the lay-up process and the joint design for two symmetric clamshells are described in this report. Finally, comparisons between the experimental test results and numerical results are presented. The comparisons indicate that the numerical analysis (static and modal analysis) agrees well with test results.
QuickChecking Static Analysis Properties
DEFF Research Database (Denmark)
Midtgaard, Jan; Møller, Anders
2015-01-01
A static analysis can check programs for potential errors. A natural question that arises is therefore: who checks the checker? Researchers have given this question varying attention, ranging from basic testing techniques, informal monotonicity arguments, thorough pen-and-paper soundness proofs......, to verified fixed point checking. In this paper we demonstrate how quickchecking can be useful for testing a range of static analysis properties with limited effort. We show how to check a range of algebraic lattice properties, to help ensure that an implementation follows the formal specification...
QuickChecking static analysis properties
DEFF Research Database (Denmark)
Midtgaard, Jan; Møller, Anders
2017-01-01
A static analysis can check programs for potential errors. A natural question that arises is therefore: who checks the checker? Researchers have given this question varying attention, ranging from basic testing techniques, informal monotonicity arguments, thorough pen-and-paper soundness proofs......, to verified fixed point checking. In this paper, we demonstrate how quickchecking can be useful to test a range of static analysis properties with limited effort. We show how to check a range of algebraic lattice properties, to help ensure that an implementation follows the formal specification of a lattice...
Sandrock, H.E.
1982-05-06
Static axial mixing apparatus includes a plurality of channels, forming flow paths of different dimensions. The axial mixer includes a flow adjusting device for adjustable selective control of flow resistance of various flow paths in order to provide substantially identical flows through the various channels, thereby reducing nonuniform coating of interior surfaces of the channels. The flow adjusting device may include diaphragm valves, and may further include a pressure regulating system therefor.
International Nuclear Information System (INIS)
Accioly, A.J.; Vaidya, A.N.; Som, M.M.
1983-01-01
The problem of static electromagnetic field admitting a time-like and two space-like Killing vectors is completely solved. The solutions contain plane-symmetric solution as a special case. The solutions can be transformed into solutions describing the gravitational field of a charge line-mass by suitably introducing weyl's canonical coordinates. Further, these solutions are true generalizations of Kasner solutions. (Author) [pt
Microprocessor controlled static converter
Directory of Open Access Journals (Sweden)
Stefan Szabo
2005-10-01
Full Text Available This paper wants to demonstrate a way of implementing a microcontroller into an DC motor speed control loop. The static power converter is a fully controlled rectifier bridge, using standard SCR's. The bridge's control signals are supplied by the microcontroller and are phase-angle or burst types. The automation loop contains a software PI-style regulator. All the experimental results shows that this aproach is flexibile enough to be used on a large scale.
National Aeronautics and Space Administration — Research is proposed for the development of a state-of-the-art computational aeroelastic tool. This tool will include various levels of fidelity and the ability to...
PEBBLES Simulation of Static Friction and New Static Friction Benchmark
International Nuclear Information System (INIS)
Cogliati, Joshua J.; Ougouag, Abderrafi M.
2010-01-01
Pebble bed reactors contain large numbers of spherical fuel elements arranged randomly. Determining the motion and location of these fuel elements is required for calculating certain parameters of pebble bed reactor operation. This paper documents the PEBBLES static friction model. This model uses a three dimensional differential static friction approximation extended from the two dimensional Cundall and Strack model. The derivation of determining the rotational transformation of pebble to pebble static friction force is provided. A new implementation for a differential rotation method for pebble to container static friction force has been created. Previous published methods are insufficient for pebble bed reactor geometries. A new analytical static friction benchmark is documented that can be used to verify key static friction simulation parameters. This benchmark is based on determining the exact pebble to pebble and pebble to container static friction coefficients required to maintain a stable five sphere pyramid.
Kilgore, R. A.; Davenport, E. E.
1976-01-01
A sharp leading edge delta-wing model was tested through an angle-of-attack range at Mach numbers of 0.75, 0.80, and 0.85 at both ambient and cryogenic temperatures in the Langley 1/3-meter transonic cryogenic tunnel. Total pressure was varied with total temperature in order to hold test Reynolds number constant at a given Mach number. Agreement between the aerodynamic data obtained at ambient and cryogenic temperatures indicates that flows with leading-edge vortex effects are duplicated properly at cryogenic temperatures. The test results demonstrate that accurate aerodynamic data can be obtained by using conventional force-testing techniques if suitable measures are taken to minimize temperature gradients across the balance and to keep the balance at ambient (warm) temperatures during cryogenic operation of the tunnel.
2016-08-01
average tensile strain of up to 5 percent (500 times higher than conventional concrete) and compressive strengths of approximately 40 MPa (5.8 ksi...produce resistance functions for a given type of support conditions. Initial test methods used positive air pressure to apply loads to masonry walls...focused on testing concrete masonry unit (CMU) walls. The CMU walls were built in place. Water is introduced simultaneously on both sides of the panel
Alexandrou, C; Tsapalis, A; Forcrand, Ph. de
2002-01-01
Using state of the art lattice techniques we investigate the static baryon potential. We employ the multi-hit procedure for the time links and a variational approach to determine the ground state with sufficient accuracy that, for distances up to $\\sim 1.2$ fm, we can distinguish the $Y$- and $\\Delta$- Ans\\"atze for the baryonic Wilson area law. Our analysis shows that the $\\Delta$-Ansatz is favoured. This result is also supported by the gauge-invariant nucleon wave function which we measure for the first time.
Gan, Jiaye
The purpose of this research is to develop high fidelity numerical methods to investigate the complex aeroelasticity fluid-structural problems of aircraft and aircraft engine turbomachinery. Unsteady 3D compressible Navier-Stokes equations in generalized coordinates are solved to simulate the complex fluid dynamic problems in aeroelasticity. An efficient and low diffusion E-CUSP (LDE) scheme designed to minimize numerical dissipation is used as a Riemann solver to capture shock waves in transonic and supersonic flows. An improved hybrid turbulence modeling, delayed detached eddy simulation (DDES), is implemented to simulate shock induced separation and rotating stall flows. High order accuracy (3rd and 5th order) weighted essentially non-oscillatory (WENO) schemes for inviscid flux and a conservative 2nd and 4th order viscous flux differencing are employed. To resolve the nonlinear interaction between flow and vibrating blade structures, a fully coupled fluid-structure interaction (FSI) procedure that solves the structural modal equations and time accurate Navier-Stokes equations simultaneously is adopted. A rotor/stator sliding interpolation technique is developed to accurately capture the blade rows interaction at the interface with general grid distribution. Phase lag boundary conditions (BC) based on the time shift (direct store) method and the Fourier series phase lag BC are applied to consider the effect of phase difference for a sector of annulus simulation. Extensive validations are conducted to demonstrate high accuracy and robustness of the high fidelity FSI methodology. The accuracy and robustness of RANS, URANS and DDES turbulence models with high order schemes for predicting the lift and drag of the DLR-F6 configuration are verified. The DDES predicts the drag very well whereas the URANS model significantly over predicts the drag. DDES of a finned projectile base flows is conducted to further validate the high fidelity methods with vortical flow. The
Augustynowicz, S. D.; Fesmire, James E.; Steinrock, T. (Technical Monitor)
2001-01-01
A unique research program, including a comprehensive study of thermal performance at cryogenic vacuum insulation systems, was performed at the NASA Kennedy Space Center. The main goal was to develop a new soft vacuum system (from 1 torr to 10 torr) that provides an intermediate level of performance (k-value below 4.8 mW/m-K). Liquid nitrogen boil-off methods were used to test conventional materials, novel materials, and certain combinations. The test articles included combinations of aluminum foil, fiberglass paper, polyester fabric, silica aerogel composite blanket, fumed silica, silica aerogel powder, and syntactic foam. A new LCI system was developed at the Cryogenics Test Laboratory. This system performs exceptionally well at soft vacuum levels and nearly as good as an MLI at high vacuum levels. Apparent thermal conductivities for the LCI range from 2 mW/m-K at soft vacuum to 0.1 mW/m-K at high vacuum. Several cryostats were designed, constructed, and calibrated by the Cryogenics Test Laboratory at KSC NASA as part of this research program. The cryostat test apparatus is a liquid nitrogen boil-off calorimeter system for direct measurement of the apparent thermal conductivity at a fixed vacuum level between 5 x 10(exp -5) and 760 torr. The apparatus is also used for transient measurements of temperature profiles. The development of efficient, robust cryogenic insulation systems has been a targeted area of research for a number of years. Improved methods of characterization, testing, and evaluation of complex biological substance systems for cryosurgery and cryobiology are the focus of this paper.
Directory of Open Access Journals (Sweden)
Daniele Pochi
2013-09-01
Full Text Available Modern tractors are characterized by the introduction of devices designed to increase the operative performances of the machines, such as systems for monitoring and controlling various functions (through a massive use of electronics and hydraulics, or deputed to improve the comfort of the driver (paying more attention to ergonomics, air-conditioning, noise and vibration. Such devices need energy to be operated, affecting the energetic balance of the tractor. In this context, the availability of suitable methodologies and instrumental systems could be useful to provide objective, accurate and reliable measurements of the performances of the tractors under different conditions, also considering the power requirements from ancillary services and/or simulating the coupling with operating machines. The tests on the performances of tractors are now made using different methods, including the trial codes issued by the OECD Codes. Beyond their undoubted validity, they fix standard test conditions that often do not adequately represent the operative reality, so that, much remains to investigate on the actual performances provided by the tractors. From this point of view and with reference to fixed point tests, a test bench was developed for the measurement of the power required by various devices, such as transmission and air conditioning. It was used in experimental tests on a tracked tractor and on a wheeled tractor, aimed at validating the test device, measuring the power absorption related to the rotational speed of the organs of propulsion and to the characteristics curves, in order to quantify the power drawn by the transmission and by the air conditioning and assess the residual power for other tractor functions. As to field conditions, a study is being conducted at CRA-ING, within the project PTO (Mi.P.A.A.F., to develop a mobile test bench aimed at evaluating the power required by different operations, such as self displacement, traction, use of
Harasid, Harun; Roesyanto; Iskandar, Rudi; Silalahi, Sofyan A.
2018-03-01
Piling Foundation is one of the foundations which is used to penetrate its load through soil layer. The power carried by the piling is obtained from the end bearing capacity, that is, the compressive end piling and friction bearing capacity obtained from friction bearing and adhesive capacity between the piling and the soil around it. The investigation on the Standard Penetration Test is aimed to get the description of soil layer, based on the type and color of soil through visual observation, and soil characteristics. SPT data can be used to calculate bearing capacity. Besides investigating the SPT, this study is also been equipped by taking the samples in laboratory and loading test on the piling and Ducth Cone Penetrometer (DCP) data to confirm its bearing capacity. This study analyzed bearing capacity and settlement in the square pile of 40X40 cm in diameter in a single pile or grouped, using an empirical method, AllPile program, Plaxis program, and comparing the result with interpreting its loading test in the foundation of Rusunawa project, Jatinegara, Jakarta. The analysis was been done by using the data on soil investigation and laboratory by comparing them with Mohr-Coulomb soil model. Ultimate bearing capacity from the SPT data in the piling of 15.4 meters was 189.81 tons and the parameter of soil shear strength was 198.67 tons. The sander point, based on Aoki and De Alencar bearing capacity was 276.241 tons and based on Mayerhoff it was 305.49 tons. Based on the loading test of bearing capacity, unlimited bearing capacity for the three methods was Davisson (260 tons), Mazurkiewich (270 tons), and Chin (250 tons). The efficiency of grouped piles according to Converse-Library Equation method = 0.73, according to Los Angeles Group Action Equation method = 0.59, and according to Sheila-Keeny method = 0.94. Bearing capacity based on piling strength was 221.76 tons, bearing capacity based on calendaring data was 201.71 tons, and lateral bearing capacity of a
National Research Council Canada - National Science Library
Yu, Yung H; Tung, Chee; van der Wall, Berend; Pausder, Heinz-Juergen; Burley, Casey; Brooks, Thomas; Beaumier, Philippe; Delrieux, Yves; Mercker, Edzard; Pengel, Kurt
2002-01-01
...) conducted a comprehensive experimental program in October 2001 with a 40%-geometrically and aeroelastically scaled model of a BO-105 main rotor in the open-jet anechoic test section of the German-Dutch Windtunnel (DNW...
Doucette, William J; Mendenhall, Scout; McNeill, Laurie S; Heavilin, Justin
2014-06-01
Tests of horizontally restrained rocket motors at the ATK facility in Promontory, Utah, USA result in the deposition of an estimated 1.5million kg of entrained soil and combustion products (mainly aluminum oxide, gaseous hydrogen chloride and water) on the surrounding area. The deposition is referred to as test fire soil (TFS). Farmers observing TFS deposited on their crops expressed concerns regarding the impact of this material. To address these concerns, we exposed corn and alfalfa to TFS collected during a September 2009 test. The impact was evaluated by comparing the growth and tissue composition of controls relative to the treatments. Exposure to TFS, containing elevated levels of chloride (1000 times) and aluminum (2 times) relative to native soils, affected the germination, growth and tissue concentrations of various elements, depending on the type and level of exposure. Germination was inhibited by high concentrations of TFS in soil, but the impact was reduced if the TFS was pre-leached with water. Biomass production was reduced in the TFS amended soils and corn grown in TFS amended soils did not develop kernels. Chloride concentrations in corn and alfalfa grown in TFS amended soils were two orders of magnitude greater than controls. TFS exposed plants contained higher concentrations of several cations, although the concentrations were well below livestock feed recommendations. Foliar applications of TFS had no impact on biomass, but some differences in the elemental composition of leaves relative to controls were observed. Washing the TFS off the leaves lessened the impact. Results indicate that the TFS deposition could have an effect, depending on the amount and growth stage of the crops, but the impact could be mitigated with rainfall or the application of additional irrigation water. The high level of chloride associated with the TFS is the main cause of the observed impacts. Copyright © 2014 Elsevier B.V. All rights reserved.
Aerodynamic and aeroelastic characteristics of the DARPA Smart Wing Phase II wind tunnel model
Sanders, Brian P.; Martin, Christopher A.; Cowan, David L.
2001-06-01
A wind tunnel demonstration was conducted on a scale model of an unmanned combat air vehicle (UCAV). The model was configured with traditional hinged control surfaces and control surfaces manufactured with embedded shape memory alloys. Control surfaces constructed with SMA wires enable a smooth and continuous deformation in both the spanwise and cordwise directions. This continuous shape results in some unique aerodynamic effects. Additionally, the stiffness distribution of the model was selected to understand the aeroelastic behavior of a wing designed with these control surfaces. The wind tunnel experiments showed that the aerodynamic performance of a wing constructed with these control surfaces is significantly improved. However, care must be taken when aeroelastic effects are considered since the wing will show a more rapid reduction in the roll moment due to increased moment arm about the elastic axis. It is shown, experimentally, that this adverse effect is easily counteracted using leading edge control surfaces.
DEFF Research Database (Denmark)
Pirrung, Georg
efficiency is increased. The model is validated against results from full rotor CFD and free wake panel code computations, which show that the model yields improved results in steady and unsteady simulations compared to unsteady BEM modeling. Especially the aerodynamic work due to prescribed in-plane and out......In this work, an aerodynamic model for the use in aeroelastic wind turbine codes is presented. It consists of a simplified lifting line model covering the induction due to the trailed vorticity in the near wake, a 2D shed vorticity model and a far wake model using the well known blade element...... momentum (BEM) theory. The model is an extension of unsteady BEM models, which provides a radial coupling of the aerodynamic sections through the trailed vorticity. The model is very fast and slows down aeroelastic wind turbine simulations by only few percent, compared to an unsteady BEM model. Compared...
DEFF Research Database (Denmark)
Gebhardt, Cristian; Veluri, Badrinath; Preidikman, Sergio
2010-01-01
loads and their evolution in the space and the time domains, considering multiple aerodynamic interactions among blades, wakes, hub, nacelle, support tower, ground and land–surface boundary layer. All these in combination affect substantially the total efficiency of the turbine. In addition, a flexible......In this work an aeroelastic model that describes the interaction between aerodynamics and drivetrain dynamics of a large horizontal–axis wind turbine is presented. Traditional designs for wind turbines are based on the output of specific aeroelastic simulation codes. The output of these codes gives...... implies that vibrations of these internal drive train components are not taken into account and, as a consequence, dynamic loads on these components cannot be simulated. In this effort an aerodynamical model based on the non–linear and unsteady vortex–lattice method is used to compute the aerodynamic...
Janetzke, D. C.; Murthy, D. V.
1991-01-01
Aeroelastic analysis is mult-disciplinary and computationally expensive. Hence, it can greatly benefit from parallel processing. As part of an effort to develop an aeroelastic analysis capability on a distributed-memory transputer network, a parallel algorithm for the computation of aerodynamic influence coefficients is implemented on a network of 32 transputers. The aerodynamic influence coefficients are calculated using a three-dimensional unsteady aerodynamic model and a panel discretization. Efficiencies up to 85 percent are demonstrated using 32 processors. The effects of subtask ordering, problem size and network topology are presented. A comparison to results on a shared-memory computer indicates that higher speedup is achieved on the distributed-memory system.
Drones for aerodynamic and structural testing /DAST/ - A status report
Murrow, H. N.; Eckstrom, C. V.
1978-01-01
A program for providing research data on aerodynamic loads and active control systems on wings with supercritical airfoils in the transonic speed range is described. Analytical development, wind tunnel tests, and flight tests are included. A Firebee II target drone vehicle has been modified for use as a flight test facility. The program currently includes flight experiments on two aeroelastic research wings. The primary purpose of the first flight experiment is to demonstrate an active control system for flutter suppression on a transport-type wing. Design and fabrication of the wing are complete and after installing research instrumentation and the flutter suppression system, flight testing is expected to begin in early 1979. The experiment on the second research wing - a fuel-conservative transport type - is to demonstrate multiple active control systems including flutter suppression, maneuver load alleviation, gust load alleviation, and reduce static stability. Of special importance for this second experiment is the development and validation of integrated design methods which include the benefits of active controls in the structural design.
Aero-elastic stability of airfoil flow using 2-D CFD
Energy Technology Data Exchange (ETDEWEB)
Johansen, J. [Risoe National Lab., Roskilde (Denmark)
1999-03-01
A three degrees-of-freedom structural dynamics model has been coupled to a two-dimensional incompressible CFD code. The numerical investigation considers aero-elastic stability for two different airfoils; the NACA0012 and the LM 2 18 % airfoils. Stable and unstable configurations and limit cycle oscillations are predicted in accordance with literature for the first airfoil. An attempt to predict stall induced edge-wise vibrations on a wind turbine airfoil fails using this two-dimensional approach. (au)
Two methods for estimating aeroelastic damping of operational wind turbine modes from experiments
DEFF Research Database (Denmark)
Hansen, Morten Hartvig; Thomsen, Kenneth; Fuglsang, Peter
2006-01-01
The theory and results of two experimental methods for estimating the modal damping of a wind turbine during operation are presented. Estimations of the aeroelastic damping of the operational turbine modes (including the effects of the aerodynamic forces) give a quantitative view of the stability...... the deterministic excitation, and the modal frequencies and damping of the first tower and first edgewise whirling modes are extracted. Copyright © 2006 John Wiley & Sons, Ltd....
The aeroelasticity research project 2004[Wind turbines]; Forskning i aeroelasticitet EFP-2004
Energy Technology Data Exchange (ETDEWEB)
Bak, C.
2005-05-01
The report presents the results of the project ''Programme for Applied Aeroelasticity'', the Danish Energy Research Programme 2004. The main results are: 1) Based on an analysis of the NREL/NASA experiment with a wind turbine in a wind tunnel a new model is formulated for 3D corrections of profile data for aeroelastic codes. Use of the model on three rotors suggests that the load distribution is determined more correctly than in existing 3D models. 2) A near-wake model, originally developed for aerodynamic loads on helicopter rotors, is implemented for calculating dynamic induction on wind turbine rotors. The model has several advantages to the other normally used model BEM. 3) A detailed comparison of the aeroelastic models FLEX5 and HAWC shows that there are no model differences that can result in large differences in the calculated loads. The comparison shows that differences in the calculated loads are due to the use of the models. 4) A model for pitch-servo dynamics on a modern wind turbine is formed and implemented in HAWC2. The conclusion from analysis of the importance of the pitch-servo characteristics showed that coupling between structure/aerodynamics and pitch actuator may be of importance, especially for the loads on the actuator itself. Also large deflections are coupled to the pitch moment and thus also to torsion of the wing and wing bearing. 5) An un-linear stability analysis has been performed in which periodic loads are included and compared to a linear analysis used in HAWCStab. For a profile with near zero aerodynamic damping in one oscillation direction, the aerodynamic force in this direction depends mostly of the square on the profile's speed. The linear damping is changed only a little by the profile's forced oscillation. It is assumed that the present HAWCStab can predict the mean aeroelastic damping for turbines' oscillations in operation. (LN)
Effect of a Bonded Patch on Aeroelastic Behavior of Cantilevered Plates
Directory of Open Access Journals (Sweden)
Sirwan Farhadi
2010-01-01
Full Text Available In recent years, many researchers have studied vibration suppression of fluttering plates using piezoelectric actuators. Lots of these researchers have focused on optimal placement of piezoelectric patches to obtain maximum controllability. Although mass and stiffness characteristics of bonded patches can alter aeroelastic behavior of fluttering plates, few of them considered the effect of the mentioned parameters in optimization process. This paper investigates effect of a bonded patch on aeroelastic behavior of cantilevered plates in supersonic flow. For this purpose, critical dynamic pressure and limit-cycle oscillations of the system are studied. Von Karman plate theory along with first order piston theory is employed for mathematical simulation of the system. Obtained results reveal that a bonded patch with a small mass ratio can change the system critical dynamic pressure significantly, where the main part of the variations is resulted from the added mass of the bonded patch. The maximum raise of dynamic pressure is acquired when the patch is placed on the plate’s leading edge. The results show that mass and stiffness characteristics of bonded piezoelectric patches can have a great impact on aeroelastic performance of fluttering plates. Therefore, these parameters must be considered as effective factors for optimal placement of piezo-actuators.
Reddy, T. S. R.; Srivastava, R.; Mehmed, Oral
2002-01-01
An aeroelastic analysis system for flutter and forced response analysis of turbomachines based on a two-dimensional linearized unsteady Euler solver has been developed. The ASTROP2 code, an aeroelastic stability analysis program for turbomachinery, was used as a basis for this development. The ASTROP2 code uses strip theory to couple a two dimensional aerodynamic model with a three dimensional structural model. The code was modified to include forced response capability. The formulation was also modified to include aeroelastic analysis with mistuning. A linearized unsteady Euler solver, LINFLX2D is added to model the unsteady aerodynamics in ASTROP2. By calculating the unsteady aerodynamic loads using LINFLX2D, it is possible to include the effects of transonic flow on flutter and forced response in the analysis. The stability is inferred from an eigenvalue analysis. The revised code, ASTROP2-LE for ASTROP2 code using Linearized Euler aerodynamics, is validated by comparing the predictions with those obtained using linear unsteady aerodynamic solutions.
A comparison between different finite elements for elastic and aero-elastic analyses
Directory of Open Access Journals (Sweden)
Mohamed Mahran
2017-11-01
Full Text Available In the present paper, a comparison between five different shell finite elements, including the Linear Triangular Element, Linear Quadrilateral Element, Linear Quadrilateral Element based on deformation modes, 8-node Quadrilateral Element, and 9-Node Quadrilateral Element was presented. The shape functions and the element equations related to each element were presented through a detailed mathematical formulation. Additionally, the Jacobian matrix for the second order derivatives was simplified and used to derive each element’s strain-displacement matrix in bending. The elements were compared using carefully selected elastic and aero-elastic bench mark problems, regarding the number of elements needed to reach convergence, the resulting accuracy, and the needed computation time. The best suitable element for elastic free vibration analysis was found to be the Linear Quadrilateral Element with deformation-based shape functions, whereas the most suitable element for stress analysis was the 8-Node Quadrilateral Element, and the most suitable element for aero-elastic analysis was the 9-Node Quadrilateral Element. Although the linear triangular element was the last choice for modal and stress analyses, it establishes more accurate results in aero-elastic analyses, however, with much longer computation time. Additionally, the nine-node quadrilateral element was found to be the best choice for laminated composite plates analysis.
Results of including geometric nonlinearities in an aeroelastic model of an F/A-18
Buttrill, Carey S.
1989-01-01
An integrated, nonlinear simulation model suitable for aeroelastic modeling of fixed-wing aircraft has been developed. While the author realizes that the subject of modeling rotating, elastic structures is not closed, it is believed that the equations of motion developed and applied herein are correct to second order and are suitable for use with typical aircraft structures. The equations are not suitable for large elastic deformation. In addition, the modeling framework generalizes both the methods and terminology of non-linear rigid-body airplane simulation and traditional linear aeroelastic modeling. Concerning the importance of angular/elastic inertial coupling in the dynamic analysis of fixed-wing aircraft, the following may be said. The rigorous inclusion of said coupling is not without peril and must be approached with care. In keeping with the same engineering judgment that guided the development of the traditional aeroelastic equations, the effect of non-linear inertial effects for most airplane applications is expected to be small. A parameter does not tell the whole story, however, and modes flagged by the parameter as significant also need to be checked to see if the coupling is not a one-way path, i.e., the inertially affected modes can influence other modes.
Pototzky, Anthony S.
2010-01-01
A methodology is described for generating first-order plant equations of motion for aeroelastic and aeroservoelastic applications. The description begins with the process of generating data files representing specialized mode-shapes, such as rigid-body and control surface modes, using both PATRAN and NASTRAN analysis. NASTRAN executes the 146 solution sequence using numerous Direct Matrix Abstraction Program (DMAP) calls to import the mode-shape files and to perform the aeroelastic response analysis. The aeroelastic response analysis calculates and extracts structural frequencies, generalized masses, frequency-dependent generalized aerodynamic force (GAF) coefficients, sensor deflections and load coefficients data as text-formatted data files. The data files are then re-sequenced and re-formatted using a custom written FORTRAN program. The text-formatted data files are stored and coefficients for s-plane equations are fitted to the frequency-dependent GAF coefficients using two Interactions of Structures, Aerodynamics and Controls (ISAC) programs. With tabular files from stored data created by ISAC, MATLAB generates the first-order aeroservoelastic plant equations of motion. These equations include control-surface actuator, turbulence, sensor and load modeling. Altitude varying root-locus plot and PSD plot results for a model of the F-18 aircraft are presented to demonstrate the capability.
A comparison between different finite elements for elastic and aero-elastic analyses.
Mahran, Mohamed; ELsabbagh, Adel; Negm, Hani
2017-11-01
In the present paper, a comparison between five different shell finite elements, including the Linear Triangular Element, Linear Quadrilateral Element, Linear Quadrilateral Element based on deformation modes, 8-node Quadrilateral Element, and 9-Node Quadrilateral Element was presented. The shape functions and the element equations related to each element were presented through a detailed mathematical formulation. Additionally, the Jacobian matrix for the second order derivatives was simplified and used to derive each element's strain-displacement matrix in bending. The elements were compared using carefully selected elastic and aero-elastic bench mark problems, regarding the number of elements needed to reach convergence, the resulting accuracy, and the needed computation time. The best suitable element for elastic free vibration analysis was found to be the Linear Quadrilateral Element with deformation-based shape functions, whereas the most suitable element for stress analysis was the 8-Node Quadrilateral Element, and the most suitable element for aero-elastic analysis was the 9-Node Quadrilateral Element. Although the linear triangular element was the last choice for modal and stress analyses, it establishes more accurate results in aero-elastic analyses, however, with much longer computation time. Additionally, the nine-node quadrilateral element was found to be the best choice for laminated composite plates analysis.
Aeroelastic stability of full-span tiltrotor aircraft model in forward flight
Directory of Open Access Journals (Sweden)
Zhiquan LI
2017-12-01
Full Text Available The existing full-span models of the tiltrotor aircraft adopted the rigid blade model without considering the coupling relationship among the elastic blade, wing and fuselage. To overcome the limitations of the existing full-span models and improve the precision of aeroelastic analysis of tiltrotor aircraft in forward flight, the aeroelastic stability analysis model of full-span tiltrotor aircraft in forward flight has been presented in this paper by considering the coupling among elastic blade, wing, fuselage and various components. The analytical model is validated by comparing with the calculation results and experimental data in the existing references. The influence of some structural parameters, such as the fuselage degrees of freedom, relative displacement between the hub center and the gravity center, and nacelle length, on the system stability is also investigated. The results show that the fuselage degrees of freedom decrease the critical stability velocity of tiltrotor aircraft, and the variation of the structural parameters has great influence on the system stability, and the instability form of system can change between the anti-symmetric and symmetric wing motions of vertical and chordwise bending. Keywords: Aeroelastic stability, Forward flight, Full-span model, Modal analysis, Tiltrotor aircraft
Ippolito, Corey; Nguyen, Nhan; Lohn, Jason; Dolan, John
2014-01-01
The emergence of advanced lightweight materials is resulting in a new generation of lighter, flexible, more-efficient airframes that are enabling concepts for active aeroelastic wing-shape control to achieve greater flight efficiency and increased safety margins. These elastically shaped aircraft concepts require non-traditional methods for large-scale multi-objective flight control that simultaneously seek to gain aerodynamic efficiency in terms of drag reduction while performing traditional command-tracking tasks as part of a complete guidance and navigation solution. This paper presents results from a preliminary study of a notional multi-objective control law for an aeroelastic flexible-wing aircraft controlled through distributed continuous leading and trailing edge control surface actuators. This preliminary study develops and analyzes a multi-objective control law derived from optimal linear quadratic methods on a longitudinal vehicle dynamics model with coupled aeroelastic dynamics. The controller tracks commanded attack-angle while minimizing drag and controlling wing twist and bend. This paper presents an overview of the elastic aircraft concept, outlines the coupled vehicle model, presents the preliminary control law formulation and implementation, presents results from simulation, provides analysis, and concludes by identifying possible future areas for research
Static Validation of XSL Transformations
DEFF Research Database (Denmark)
Møller, Anders; Olesen, Mads Østerby; Schwartzbach, Michael Ignatieff
2007-01-01
no static guarantees that, under the assumption that the input is valid relative to the input schema, the output of the transformation is valid relative to the output schema. We present a validation technique for XSLT based on the XML graph formalism introduced in the static analysis of JWIG Web services...... and XACT XML transformations. Being able to provide static guarantees, we can detect a large class of errors in an XSLT stylesheet at the time it is written instead of later when it has been deployed, and thereby provide benefits similar to those of static type checkers for modern programming languages...
Static Analysis Using the Cloud
Directory of Open Access Journals (Sweden)
Rahul Kumar
2016-10-01
Full Text Available In this paper we describe our experience of using Microsoft Azure cloud computing platform for static analysis. We start by extending Static Driver Verifier to operate in the Microsoft Azure cloud with significant improvements in performance and scalability. We present our results of using SDV on single drivers and driver suites using various configurations of the cloud relative to a local machine. Finally, we describe the Static Module Verifier platform, a highly extensible and configurable platform for static analysis of generic modules, where we have integrated support for verification using a cloud services provider (Microsoft Azure in this case.
Federal Laboratory Consortium — Structural testing is performed to verify the structural integrity of space flight and ground test hardware. Testing is also performed to verify the finite element...
Statics and Mechanics of Structures
DEFF Research Database (Denmark)
Krenk, Steen; Høgsberg, Jan Becker
The statics and mechanics of structures form a core aspect of civil engineering. This book provides an introduction to the subject, starting from classic hand-calculation types of analysis and gradually advancing to a systematic form suitable for computer implementation. It starts with statically...
DEFF Research Database (Denmark)
Bergami, Leonardo; Gaunaa, Mac; Heinz, Joachim Christian
2013-01-01
The aeroelastic response of wind turbines is often simulated in the time domain by using indicial response techniques. Unsteady aerodynamics in attached flow are usually based on Jones's approximation of the flat plate indicial response, although the response for finite‐thickness airfoils differs...... of equivalent fatigue loads, ultimate loads, and stability limits. The agreement with CFD computations of a 2D profile in harmonic motion is improved by the indicial function accounting for the finite‐thickness of the airfoil. Concerning the full wind turbine aeroelastic behavior, the differences between...... profile undergoing harmonic pitching motion in the attached flow region; the resulting lift forces are compared with computational fluid dynamics (CFD) simulations. The relevance for aeroelastic simulations of a wind turbine is also evaluated, and the effects are quantified in terms of variations...
Energy Technology Data Exchange (ETDEWEB)
Baxevanou, C.A.; Vlachos, N.S. [Department of Mechanical and Industrial Engineering, University of Thessaly, Athens Avenue, 38334 Volos (Greece); Chaviaropoulos, P.K. [Centre for Renewable Energy Sources, Pikermi Attikis (Greece); Voutsinas, S.G. [Department of Mechanical Engineering, National Technical University of Athens (Greece)
2008-08-15
This paper describes a new aeroelastic numerical model, which combines a Navier-Stokes CFD solver with an elastic model and two coupling schemes for the study of the aeroelastic behaviour of wind turbine blades undergoing classical flutter. The basic characteristics of the aerodynamic and elastic models are presented together with the coupling schemes. The present model is evaluated by comparing with previous numerical results and the corresponding linear analytical solutions. Consequently, a parametric study is carried out. Conclusions are drawn about the ability of the model to handle the aeroelastic behaviour of an airfoil and about the most appropriate coupling scheme in terms of predicting the modal damping and the flutter limiting point. The present study shows that the predictions are only slightly affected by the coupling or the space discretization scheme and mainly by the turbulence model used. (author)
Static three- and four-quark potentials
Alexandrou, C; Tsapalis, A; Forcrand, Ph.de
2002-01-01
We present results for the static three- and four-quark potentials in SU(3) and SU(4) respectively. Using a variational approach, combined with multi-hit for the time-like links, we determine the ground state of the baryonic string with sufficient accuracy to test the $Y-$ and $\\Delta-$ ans\\"atze for the baryonic Wilson area law. Our results favor the $\\Delta$ ansatz, where the potential is the sum of two-body terms.
Comparing numerically exact and modelled static friction
Directory of Open Access Journals (Sweden)
Krengel Dominik
2017-01-01
Full Text Available Currently there exists no mechanically consistent “numerically exact” implementation of static and dynamic Coulomb friction for general soft particle simulations with arbitrary contact situations in two or three dimension, but only along one dimension. We outline a differential-algebraic equation approach for a “numerically exact” computation of friction in two dimensions and compare its application to the Cundall-Strack model in some test cases.
14 CFR 25.629 - Aeroelastic stability requirements.
2010-01-01
... be shown by analyses, wind tunnel tests, ground vibration tests, flight tests, or other means found..., large auxiliary power unit, or large externally mounted aerodynamic body (such as an external fuel tank... addition, the effect of a single feathered propeller or rotating device must be coupled with the failures...
Aeroelastic stability of plate interacting with a flowing fluid
Directory of Open Access Journals (Sweden)
Sergey A. Bochkarev
2016-09-01
Full Text Available The paper presents the results of a numerical study of the dynamic behavior of the deformable plate interacting both with the external supersonic gas flow and the internal fluid flow. The constitutive relations describing the behavior of ideal compressible fluid in the case of small perturbations are written in terms of the perturbation velocity potential and transformed using the Bubnov–Galerkin method. The aero- and dynamic pressures are calculated based on the quasi-static aerodynamic theory. The strains in the plate evaluated following the Timoshenko hypotheses. A mathematical formulation of the dynamic problem of elastic structure is developed using the variational principle of virtual displacements, which takes into account the work done by the inertia forces, aerodynamic and hydrodynamic pressures. Calculation of complex eigenvalues of the coupled system of two equations is performed using an algorithm based on implicitly restarted Arnoldi method. The stability criterion is based on an analysis of the complex eigenvalues of system of two equations obtained for increasing flow or gas velocity. The reliability of the obtained numerical solution has been estimated by comparing it with the available theoretical data. A few numerical examples were considered to demonstrate the existence of different types of instability depending on the velocities of fluid or gas flow, combinations of kinematic boundary conditions prescribed at the edges of the plate, and the fluid layer height. It has been found that a violation of the smoothness of the obtained relationships and diagrams of stability is caused by a change in the flutter mode, or change of the type of loss of stability.
Statics of Historic Masonry Constructions
Como, Mario
2013-01-01
Masonry constructions are the great majority of the buildings in Europe’s historic centres and the most important monuments in its architectural heritage. Given the age of much of these constructions, the demand for safety assessments and restoration projects is pressing and constant. This book aims to help fill this demand presenting a comprehensive new statics of masonry constructions. The book, result of thirty years of research and professional experience, gives the fundamentals of statics of the masonry solid, then applied to the study of statics of arches, piers and vaults. Further, combining engineering and architecture and through an interdisciplinary approach, the book investigates the statical behaviour of many historic monuments, as the Pantheon, the Colosseum, the domes of S. Maria del Fiore in Florence and of St. Peter in Rome, the Tower of Pisa, the Gothic Cathedrals and the Masonry Buildings under seismic actions.
Statics and mechanics of structures
Krenk, Steen
2013-01-01
The statics and mechanics of structures form a core aspect of civil engineering. This book provides an introduction to the subject, starting from classic hand-calculation types of analysis and gradually advancing to a systematic form suitable for computer implementation. It starts with statically determinate structures in the form of trusses, beams and frames. Instability is discussed in the form of the column problem - both the ideal column and the imperfect column used in actual column design. The theory of statically indeterminate structures is then introduced, and the force and deformation methods are explained and illustrated. An important aspect of the book’s approach is the systematic development of the theory in a form suitable for computer implementation using finite elements. This development is supported by two small computer programs, MiniTruss and MiniFrame, which permit static analysis of trusses and frames, as well as linearized stability analysis. The book’s final section presents related ...
Introduction of the ASP3D Computer Program for Unsteady Aerodynamic and Aeroelastic Analyses
Batina, John T.
2005-01-01
A new computer program has been developed called ASP3D (Advanced Small Perturbation 3D), which solves the small perturbation potential flow equation in an advanced form including mass-consistent surface and trailing wake boundary conditions, and entropy, vorticity, and viscous effects. The purpose of the program is for unsteady aerodynamic and aeroelastic analyses, especially in the nonlinear transonic flight regime. The program exploits the simplicity of stationary Cartesian meshes with the movement or deformation of the configuration under consideration incorporated into the solution algorithm through a planar surface boundary condition. The new ASP3D code is the result of a decade of developmental work on improvements to the small perturbation formulation, performed while the author was employed as a Senior Research Scientist in the Configuration Aerodynamics Branch at the NASA Langley Research Center. The ASP3D code is a significant improvement to the state-of-the-art for transonic aeroelastic analyses over the CAP-TSD code (Computational Aeroelasticity Program Transonic Small Disturbance), which was developed principally by the author in the mid-1980s. The author is in a unique position as the developer of both computer programs to compare, contrast, and ultimately make conclusions regarding the underlying formulations and utility of each code. The paper describes the salient features of the ASP3D code including the rationale for improvements in comparison with CAP-TSD. Numerous results are presented to demonstrate the ASP3D capability. The general conclusion is that the new ASP3D capability is superior to the older CAP-TSD code because of the myriad improvements developed and incorporated.
Static and Dynamic Traversable Wormholes
Adamiak, Jaroslaw P.
2008-09-01
The aim of this work is to discuss the effects found in static and dynamic wormholes that occur as a solution of Einstein equations in general relativity. The ground is prepared by presentation of faster than light effects, then the focus is narrowed to Morris-Thorne framework for a static spherically symmetric wormhole. Two types of dynamic worm-holes, evolving and rotating, are considered.
Static Decoupling in fault detection
DEFF Research Database (Denmark)
Niemann, Hans Henrik
1998-01-01
An algebraic approach is given for a design of a static residual weighting factor in connection with fault detection. A complete parameterization is given of the weighting factor which will minimize a given performance index......An algebraic approach is given for a design of a static residual weighting factor in connection with fault detection. A complete parameterization is given of the weighting factor which will minimize a given performance index...
Czech Academy of Sciences Publication Activity Database
Sváček, P.; Horáček, Jaromír
2015-01-01
Roč. 267, September (2015), s. 28-41 ISSN 0096-3003 R&D Projects: GA ČR(CZ) GAP101/11/0207; GA ČR GAP101/12/1271 Institutional support: RVO:61388998 Keywords : aeroelasticity * finite element method * 2D RANS equation s * sudden gust Subject RIV: BI - Acoustics Impact factor: 1.345, year: 2015 http://www.sciencedirect.com/science/article/pii/S0096300315008887/pdfft?md5=1329144b9cc04b57a05c506ae7f54b0a&pid=1-s2.0-S0096300315008887-main.pdf
Aeroelastic large eddy simulations using vortex methods: unfrozen turbulent and sheared inflow
DEFF Research Database (Denmark)
Branlard, Emmanuel Simon Pierre; Papadakis, G.; Gaunaa, Mac
2015-01-01
Vortex particles methods are applied to the aeroelastic simulation of a wind turbine in sheared and turbulent inflow. The possibility to perform large-eddy simulations of turbulence with the effect of the shear vorticity is demonstrated for the first time in vortex methods simulations. Most vortex...... methods formulation of shear, including segment formulations, assume a frozen shear. It is here shown that these formulations omit two source terms in the vorticity equation. The current paper also present unfrozen simulation of shear. The infinite support of the shear vorticity is accounted for using...
Reduced-order LPV model of flexible wind turbines from high fidelity aeroelastic codes
DEFF Research Database (Denmark)
Adegas, Fabiano Daher; Sønderby, Ivan Bergquist; Hansen, Morten Hartvig
2013-01-01
of high-order linear time invariant (LTI) models. Firstly, the high-order LTI models are locally approximated using modal and balanced truncation and residualization. Then, an appropriate coordinate transformation is applied to allow interpolation of the model matrices between points on the parameter...... space. The obtained LPV model is of suitable size for designing modern gain-scheduling controllers based on recently developed LPV control design techniques. Results are thoroughly assessed on a set of industrial wind turbine models generated by the recently developed aeroelastic code HAWCStab2....
Analysis of wind turbine aerodynamics and aeroelasticity using vortex-based methods
DEFF Research Database (Denmark)
Branlard, Emmanuel Simon Pierre
Momentum analysis through Blade Element Momentum (BEM) and Computational Fluid Dynamics (CFD) are the two major paths commonly followed for wind turbine aerodynamic and aeroelastic research. Instead, the current PhD thesis focuses on the application of vortex-based methods. Vortex-based methods...... to be used in BEM implementations. The current thesis also presents the implementation of a vortex code to further investigate wind turbine aerodynamics. The code consists of both low-order and high-order formulations. The implementation features are described and illustrated through different validation...
Trailed vorticity modeling for aeroelastic wind turbine simulations in stand still
DEFF Research Database (Denmark)
Pirrung, Georg; Aagaard Madsen, Helge; Schreck, Scott
2016-01-01
Current fast aeroelastic wind turbine codes suitable for certification lack an induction model for standstill conditions. A trailed vorticity model previously used as addition to a blade element momentum theory based aerodynamic model in normal operation has been extended to allow computing...... the steady loading for the Phase VI blade in attached flow. The prediction of the dynamic force coefficient loops from the Phase VI experiment is improved by the trailed vorticity modeling in both attached flow and stall in most cases. The exception is the tangential force coefficient in stall, where...
Effect of steady deflections on the aeroelastic stability of a turbine blade
DEFF Research Database (Denmark)
Kallesøe, Bjarne Skovmose
2011-01-01
This paper deals with effects of geometric non-linearities on the aeroelastic stability of a steady-state defl ected blade. Today, wind turbine blades are long and slender structures that can have a considerable steady-state defl ection which affects the dynamic behaviour of the blade. The fl...... apwise blade defl ection causes the edgewise blade motion to couple to torsional blade motion and thereby to the aerodynamics through the angle of attack. The analysis shows that in the worst case for this particular blade, the edgewise damping can be decreased by half. Copyright © 2010 John Wiley & Sons......, Ltd....
Static Checking of Interrupt-driven Software
DEFF Research Database (Denmark)
Brylow, Dennis; Damgaard, Niels; Palsberg, Jens
2001-01-01
Resource-constrained devices are becoming ubiquitous. Examples include cell phones, palm pilots, and digital thermostats. It can be difficult to fit required functionality into such a device without sacrificing the simplicity and clarity of the software. Increasingly complex embedded systems...... require extensive brute-force testing, making development and maintenance costly. This is particularly true for system components that are written in assembly language. Static checking has the potential of alleviating these problems, but until now there has been little tool support for programming...... at the assembly level. In this paper we present the design and implementation of a static checker for interrupt-driven Z86-based software with hard real-time requirements. For six commercial microcontrollers, our checker has produced upper bounds on interrupt latencies and stack sizes, as well as verified...
Scott, Robert C.; Bartels, Robert E.
2009-01-01
This paper examines the aeroelastic stability of an on-orbit installable Space Shuttle patch panel. CFD flutter solutions were obtained for thick and thin boundary layers at a free stream Mach number of 2.0 and several Mach numbers near sonic speed. The effect of structural damping on these flutter solutions was also examined, and the effect of structural nonlinearities associated with in-plane forces in the panel was considered on the worst case linear flutter solution. The results of the study indicated that adequate flutter margins exist for the panel at the Mach numbers examined. The addition of structural damping improved flutter margins as did the inclusion of nonlinear effects associated with a static pressure difference across the panel.
Directory of Open Access Journals (Sweden)
Anderson Freitas
2009-01-01
Full Text Available OBJETIVO: Avaliar isolada e comparativamente placas do tipo sistema dinâmico do quadril (DHS de dois fabricantes nacionais, analisar estatisticamente seus resultados e demonstrar a falta de determinantes para sua fabricação. MÉTODOS: Foram realizados ensaios estáticos de flexão em cinco placas DHS do fabricante I (grupo I e em igual quantidade do mesmo modelo do fabricante II (grupo II, sendo todas fabricadas em aço inoxidável austenítico ASTM F 138, com quatro furos e angulação de 135º. Utilizou-se máquina servohidráulica MTS, modelo Test Star II®, com capacidade de carga de 10 toneladas e controle de deslocamento. Foram obtidos dados da carga aplicada (P em função do deslocamento vertical do pistão (L, cuja velocidade foi 5 mm/min. Os ensaios foram interrompidos após atingir a deflexão vertical máxima especificada pelas normas dos ensaios. RESULTADOS: Grupo I: resistência de flexão, 161,4 ± 17,2 kgf rigidez, 64,5 ± 1,8 kgf/mm, ductilidade, > 25,4 mm. Grupo II: resistência de flexão, 124,7 ± 4,4, rigidez 59,6 ± 2,3, ductilidade > 25,4 mm. Para análise estatística foi adotado o teste de Mann-Whitney e a determinação de significância foi de 5% (pOBJECTIVE: To evaluate, both individually and comparatively, dynamic hip system-type plates marketed by two local manufacturers, to statistically analyze its results and show the lack of parameters for its manufacturing. METHODS: Static tests of flexion were carried out in five DHS plates of the manufacturer I (I group I and in equal quantity of the same model of the manufacturer II (I group II, being all made in stainless austenitic ASTM F 138 steel, with four holes and a 135º angle. A servo-hydraulic MTS machine, Test Star II model, was used with a load capacity of 10 tons and dislocation control. The data were obtained from the applied load (P as a function of the vertical dislocation of the piston (L, whose speed was 5mm/min. The tests were shutdown after reaching
Static Analysis of Android Apps: A Systematic Literature Review
Li, Li; Bissyande, Tegawendé François D Assise; Papadakis, Mike; Rasthofer, Siegfried; Bartel, Alexandre; Octeau, Damien; Klein, Jacques; Le Traon, Yves
2017-01-01
Context: Static analysis exploits techniques that parse program source code or bytecode, often traversing program paths to check some program properties. Static analysis approaches have been proposed for different tasks, including for assessing the security of Android apps, detecting app clones, automating test cases generation, or for uncovering non-functional issues related to performance or energy. The literature thus has proposed a large body of works, each of which attempts to tackle one...
Barlas, A.; van Kuik, G.A.M.
2009-01-01
A newly developed comprehensive aeroelastic model is used to investigate active flap concepts on the Upwind 5MW reference wind turbine. The model is specially designed to facilitate distributed control concepts and advanced controller design. Different concepts of centralized and distributed control
Barlas, A.; Van Kuik, G.A.M.
2009-01-01
A newly developed comprehensive aeroelastic model is used to investigate active flap concepts on the Upwind 5MW reference wind turbine. The model is specially designed to facilitate distributed control concepts and advanced controller design. Different concepts of centralized and distributed control
Energy Technology Data Exchange (ETDEWEB)
Dugeai, A.; Sens, A.S. [Office National d' Etudes et de Recherches Aerospatiales (ONERA), 92 - Chatillon (France); Madec, A. [Societe Nationale d' Etude et de Construction de Moteurs d' Aviation SNECMA, 77 - Villaroche (France)
2001-07-01
A computational tool for the prediction of aeronautical machineries aeroelastic stability is presented. Numerical features of the quasi-3D Navier-Stokes unsteady solver are discussed: turbulence models, grid deformation techniques, specific boundary conditions. Isolated profile and cascade computational results are compared to experimental data, for steady and unsteady cases. (authors)
Static and Dynamic Friction Behavior of Candidate High Temperature Airframe Seal Materials
Dellacorte, C.; Lukaszewicz, V.; Morris, D. E.; Steinetz, B. M.
1994-01-01
The following report describes a series of research tests to evaluate candidate high temperature materials for static to moderately dynamic hypersonic airframe seals. Pin-on-disk reciprocating sliding tests were conducted from 25 to 843 C in air and hydrogen containing inert atmospheres. Friction, both dynamic and static, was monitored and serves as the primary test measurement. In general, soft coatings lead to excessive static friction and temperature affected friction in air environments only.
Pre-exposure to moving form enhances static form sensitivity.
Directory of Open Access Journals (Sweden)
Thomas S A Wallis
Full Text Available BACKGROUND: Motion-defined form can seem to persist briefly after motion ceases, before seeming to gradually disappear into the background. Here we investigate if this subjective persistence reflects a signal capable of improving objective measures of sensitivity to static form. METHODOLOGY/PRINCIPAL FINDINGS: We presented a sinusoidal modulation of luminance, masked by a background noise pattern. The sinusoidal luminance modulation was usually subjectively invisible when static, but visible when moving. We found that drifting then stopping the waveform resulted in a transient subjective persistence of the waveform in the static display. Observers' objective sensitivity to the position of the static waveform was also improved after viewing moving waveforms, compared to viewing static waveforms for a matched duration. This facilitation did not occur simply because movement provided more perspectives of the waveform, since performance following pre-exposure to scrambled animations did not match that following pre-exposure to smooth motion. Observers did not simply remember waveform positions at motion offset, since removing the waveform before testing reduced performance. CONCLUSIONS/SIGNIFICANCE: Motion processing therefore interacts with subsequent static visual inputs in a way that can improve performance in objective sensitivity measures. We suggest that the brief subjective persistence of motion-defined forms that can occur after motion offsets is a consequence of the decay of a static form signal that has been transiently enhanced by motion processing.
Statics of historic masonry constructions
Como, Mario
2017-01-01
Masonry constructions are the great majority of the buildings in Europe’s historic centres and the most important monuments of its architectural heritage. Given the age of these constructions, the demand for safety assessments and restoration projects is pressing and constant; still within the broad studies in the subject it is not yet recognised, in particular within the seismic area, a unitary approach to deal with Masonry structures. This successful book contributes to clarify the issues with a rigorous approach offering a comprehensive new Statics of Masonry Constructions. This third edition has been driven by some recent developments of the research in the field, and it gives the fundamentals of Statics with an original and rigorous mathematical formulation, further in-depth inquired in this new version. With many refinements and improvements, the book investigates the static behaviour of many historic monuments, such as the Gothic Cathedrals, the Mycenaean Tholoi, the Pantheon, the Colosseum, the dome...
Czech Academy of Sciences Publication Activity Database
Krištofíková, Z.; Čermák, M.; Benešová, O.; Klaschka, Jan; Zach, P.
2005-01-01
Roč. 30, č. 2 (2005), s. 253-262 ISSN 0364-3190 R&D Projects: GA MZd NF7576 Keywords : magnetic nanoparticles * choline transport * cholinergic * functional impairment * hippocampus * laterality * magnetoreception * static magnetic field Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 2.187, year: 2005
Zhang, Dongliang
2014-08-05
The quality of migration images depends on the accuracy of the velocity model. For large velocity errors, the migration image is strongly distorted, which unflattens events in the common image gathers and consequently leads to a blurring in the stacked migration image. To mitigate this problem, we propose dynamic image warping to flatten the common image gathers before stacking and to enhance the signal-to-noise ratio of the migration image. Numerical tests on the Marmousi model and GOM data show that image warping of the prestack images followed by stacking leads to much better resolved reflectors than the original migration image. The problem, however, is that the reflector locations have increased uncertainty because the wrong velocity model is still used.
Scott, Robert C.; Vetter, Travis K.; Penning, Kevin B.; Coulson, David A.; Heeg, Jennifer
2014-01-01
This is part 2 of a two part document. Part 1 is titled: "Aeroservoelastic Testing of Free Flying Wind Tunnel Models Part 1: A Sidewall Supported Semispan Model Tested for Gust Load Alleviation and Flutter Suppression." A team comprised of the Air Force Research Laboratory (AFRL), Boeing, and the NASA Langley Research Center conducted three aeroservoelastic wind tunnel tests in the Transonic Dynamics Tunnel to demonstrate active control technologies relevant to large, flexible vehicles. In the first of these three tests, a full-span, aeroelastically scaled, wind tunnel model of a joined wing SensorCraft vehicle was mounted to a force balance to acquire a basic aerodynamic data set. In the second and third tests, the same wind tunnel model was mated to a new, two degree of freedom, beam mount. This mount allowed the full-span model to translate vertically and pitch. Trimmed flight at10 percent static margin and gust load alleviation were successfully demonstrated. The rigid body degrees of freedom required that the model be flown in the wind tunnel using an active control system. This risky mode of testing necessitated that a model arrestment system be integrated into the new mount. The safe and successful completion of these free-flying tests required the development and integration of custom hardware and software. This paper describes the many systems, software, and procedures that were developed as part of this effort. The balance and free flying wind tunnel tests will be summarized. The design of the trim and gust load alleviation control laws along with the associated results will also be discussed.
Statics and Mechanics of Structures
DEFF Research Database (Denmark)
Krenk, Steen; Høgsberg, Jan Becker
The statics and mechanics of structures form a core aspect of civil engineering. This book provides an introduction to the subject, starting from classic hand-calculation types of analysis and gradually advancing to a systematic form suitable for computer implementation. It starts with statically...... of trusses and frames, as well as linearized stability analysis. The book’s final section presents related strength of materials subjects in greater detail; these include stress and strain, failure criteria, and normal and shear stresses in general beam flexure and in beam torsion....
EFFECT OF STATIC STRETCHING ON STRENGTH OF HAMSTRING MUSCLE
Directory of Open Access Journals (Sweden)
Shweta P Pachpute
2016-04-01
Full Text Available Background: Flexibility is an indisputable component of fitness defined as the ability to move a single joint or series of joints through an unrestricted pain free range of motion. Static stretching consists of stretching a muscle or group of muscle to its farthest point and then maintaining or holding that position. The literature supports that muscles are capable of exerting their greatest strength when they are fully lengthen. Hence this study was conducted to find the effect of static stretching on hamstring muscle. Methods: The study was experimental study design. 40 samples were selected by purposive sampling method. Flexibility of the hamstring muscle unilaterally right side (arbitrarily chosen was measured by active knee extension test of all the subjects who met the inclusion criteria of the study. After measuring the flexibility of hamstring muscle, strength was measured by 1RM for the same side (right hamstring muscle. Static Stretching Protocol was given for 5 days per week for 6 weeks to all the participants. After the 6 weeks of training, knee extension deficiency and 1RM was documented. Result: Statistical analysis using Paired t-test was done. The t-test showed that there was significant effect of static stretching on 1RM of hamstring muscle (p<0.05 & active knee extension test (p=0.000. Conclusion: Static stretching showed significant change in pre and post 1RM of hamstring muscle and active knee extension test. There was significant improvement of hamstring muscles flexibility and strength after giving static stretching in female population. So it is possible that females who are unable to participate in traditional strength training activities may be able to experience gains through static stretching.
Wind-tunnel tests of the XV-15 tilt rotor aircraft
Weiberg, J. A.; Maisel, M. D.
1980-01-01
The XV-15 aircraft was tested in the Ames 40 by 80 Foot Wind Tunnel for preliminary evaluation of aerodynamic and aeroelastic characteristics prior to flight. The tests were undertaken to investigate the aircraft performance, stability, control and structural loads for flight modes from helicopter through transition and airplane mode up to the tunnel capability of 170 knots. Results from these tests are presented.
HiMAT aerodynamic design and flight test experience
Matheny, N. W.; Panageas, G. N.
1981-01-01
Consideration is given to the design phase of the highly maneuverable aircraft technology program. Design objectives are examined, noting full-scale design and the remotely piloted research vehicle. Attention is given to subsonic, transonic, and supersonic design. Design results are discussed with reference to aerodynamic efficiency, aeroelastic tailoring, and the flight test program.
Static Analysis for Dynamic XML
DEFF Research Database (Denmark)
Christensen, Aske Simon; Møller, Anders; Schwartzbach, Michael Ignatieff
2002-01-01
We describe the summary graph lattice for dataflow analysis of programs that dynamically construct XML documents. Summary graphs have successfully been used to provide static guarantees in the JWIG language for programming interactive Web services. In particular, the JWIG compiler is able to check...
Some Static Properties of Slinky
Eskandari-asl, Amir
2018-01-01
In this paper we use a simple discrete model for Slinky to explore some of its static properties. We derive some relations for vertically and U-shaped suspended Slinkies, based on which, some demonstrations are proposed that can be simply done in freshmen physics classes.
Static Analysis of Dynamic Languages
DEFF Research Database (Denmark)
Madsen, Magnus
with static type systems, such as Java and C# , but the same features are rarely available for dynamic languages such as JavaScript. The aim of this thesis is to investigate techniques for improving the tool- support for dynamic programming languages without imposing any artificial restrictions...
Static Verification for Code Contracts
Fähndrich, Manuel
The Code Contracts project [3] at Microsoft Research enables programmers on the .NET platform to author specifications in existing languages such as C# and VisualBasic. To take advantage of these specifications, we provide tools for documentation generation, runtime contract checking, and static contract verification.
Static Analysis for Systems Biology
DEFF Research Database (Denmark)
Nielson, Flemming; Nielson, Hanne Riis; Rosa, D. Schuch da
2004-01-01
This paper shows how static analysis techniques can help understanding biological systems. Based on a simple example we illustrate the outcome of performing three different analyses extracting information of increasing precision. We conclude by reporting on the potential impact and exploitation o...... of these techniques in systems biology....
Static Correctness of Hierarchical Procedures
DEFF Research Database (Denmark)
Schwartzbach, Michael Ignatieff
1990-01-01
A system of hierarchical, fully recursive types in a truly imperative language allows program fragments written for small types to be reused for all larger types. To exploit this property to enable type-safe hierarchical procedures, it is necessary to impose a static requirement on procedure calls...
Static strain aging in austenitic stainless steels
International Nuclear Information System (INIS)
Monteiro, S.N.
1978-07-01
The static strain aging effects were investigated in austenitic stainless steels by measuring the yield points developed in tensile tests following the arrest of the crosshead for some period of time. The results appear to indicate that the dragging of dislocations in the interval of temperatures from 100 to 300 0 C, where the strain aging is effective, does not apparently depend on the Cottrell's atmosphere. Moreover the influence of the pre-deformation and time on the yield point intensity displayed the existence of stages. The strain aging mechanics and the reasons for the stages were discussed. (Author) [pt
Aeroelastic flutter energy harvesters self-polarized by triboelectric effects
Perez, M.; Boisseau, S.; Geisler, M.; Gasnier, P.; Willemin, J.; Despesse, G.; Reboud, J. L.
2018-01-01
This paper presents the performances of several electrostatic flutter energy harvesters tested in a wind tunnel between 0 and 20 m s-1. The main idea is to use the flutter capability of thin flexible films confined between lateral walls to induce simultaneously the capacitance variations and the electrostatic polarization required by the triboelectric/electrostatic conversion. This technology provides thin and flexible devices and solve the electret’s stability issue (Perez et al 2015 Smart Mater. Struct., Perez et al 2015 New Circuits and Systems). Our prototypes (light breeze) to 35 μW cm-2@20 m s-1 (fresh gale). A Maximum Power Point circuit has been developed to efficiently use the power provided by the energy harvesters. The energy harvester combined with its power management circuit has finally been used to supply an 868 MHz wireless sensor node with temperature and acceleration measurements, validating the complete energy harvesting chain.
Bartels, Robert E.; Scott, Robert C.; Allen, Timothy J.; Sexton, Bradley W.
2015-01-01
Considerable attention has been given in recent years to the design of highly flexible aircraft. The results of numerous studies demonstrate the significant performance benefits of strut-braced wing (SBW) and trussbraced wing (TBW) configurations. Critical aspects of the TBW configuration are its larger aspect ratio, wing span and thinner wings. These aspects increase the importance of considering fluid/structure and control system coupling. This paper presents high-fidelity Navier-Stokes simulations of the dynamic response of the flexible Boeing Subsonic Ultra Green Aircraft Research (SUGAR) truss-braced wing wind-tunnel model. The latest version of the SUGAR TBW finite element model (FEM), v.20, is used in the present simulations. Limit cycle oscillations (LCOs) of the TBW wing/strut/nacelle are simulated at angle-of-attack (AoA) values of -1, 0 and +1 degree. The modal data derived from nonlinear static aeroelastic MSC.Nastran solutions are used at AoAs of -1 and +1 degrees. The LCO amplitude is observed to be dependent on AoA. LCO amplitudes at -1 degree are larger than those at +1 degree. The LCO amplitude at zero degrees is larger than either -1 or +1 degrees. These results correlate well with both wind-tunnel data and the behavior observed in previous studies using linear aerodynamics. The LCO onset at zero degrees AoA has also been computed using unloaded v.20 FEM modes. While the v.20 model increases the dynamic pressure at which LCO onset is observed, it is found that the LCO onset at and above Mach 0.82 is much different than that produced by an earlier version of the FEM, v. 19.
Rolling Contact Fatigue and Static Compression Deformation of UHMWPE thrust bearing in water
Directory of Open Access Journals (Sweden)
Inagaki Masahiro
2017-01-01
Full Text Available In this study, the rolling contact fatigue tests were performed in order to investigate the effect of thrust load on life of UHMWPE bearings. Furthermore, the static compression tests were performed in order to investigate the effect of static load on deformation. It was found that thrust load controls limitations of the bearings, and the deformation by the static load is not the main reason of the adhesion failure.
Scott, Robert C.; Castelluccio, Mark A.; Coulson, David A.; Heeg, Jennifer
2011-01-01
A team comprised of the Air Force Research Laboratory (AFRL), Boeing, and the NASA Langley Research Center conducted three aeroservoelastic wind-tunnel tests in the Transonic Dynamics Tunnel to demonstrate active control technologies relevant to large, exible vehicles. In the first of these three tests, a full-span, aeroelastically scaled, wind-tunnel model of a joined-wing SensorCraft vehicle was mounted to a force balance to acquire a basic aerodynamic data set. In the second and third tests, the same wind-tunnel model was mated to a new, two-degree-of-freedom, beam mount. This mount allowed the full-span model to translate vertically and pitch. Trimmed flight at -10% static margin and gust load alleviation were successfully demonstrated. The rigid body degrees of freedom required that the model be own in the wind tunnel using an active control system. This risky mode of testing necessitated that a model arrestment system be integrated into the new mount. The safe and successful completion of these free-flying tests required the development and integration of custom hardware and software. This paper describes the many systems, software, and procedures that were developed as part of this effort. The balance and free ying wind-tunnel tests will be summarized. The design of the trim and gust load alleviation control laws along with the associated results will also be discussed.
Aeroelastic performance evaluation of a flexure box morphing airfoil concept
Pankonien, Alexander M.; Inman, Daniel J.
2014-04-01
The flexure-box morphing aileron concept utilizes Macro-Fiber Composites (MFCs) and a compliant box to create a conformal morphing aileron. This work evaluates the impact of the number of MFCs on the performance, power and mass of the aileron by experimentally investigating two different actuator configurations: unimorph and bimorph. Implemented in a NACA 0012 airfoil with 304.8 mm chord, the unimorph and bimorph configurations are experimentally tested over a range of flow speeds from 5 to 20 m/s and angles of attack from -20 to 20 degrees under aerodynamic loads in a wind tunnel. An embedded flexible sensor is installed in the aileron to evaluate the effect of aerodynamic loading on tip position. For both design choices, the effect of actuation on lift, drag and pitching moment coefficients are measured. Finally, the impact on aileron mass and average power consumption due to the added MFCs is considered. The results showed the unimorph exhibiting superior ability to influence flow up to 15 m/s, with equivalent power consumption and lower overall mass. At 20 m/s, the bimorph exhibited superior control over aerodynamic forces and the unimorph experienced significant deformation due to aerodynamic loading.
Static Force-Deflection Properties of Automobile Steering Components
1987-06-01
This report provides the static force-deflection test results for 28 steering columns and 24 steering wheels used in domestic and import passener cars from model year 1975 to 1985. The steering columns and wheels tested include approzimately 90 perce...
Static and Animated Presentations in Learning Dynamic Mechanical Systems
Boucheix, Jean-Michel; Schneider, Emmanuel
2009-01-01
In two experiments, we investigated how learners comprehend the functioning of a three-pulley system from a presentation on a computer screen. In the first experiment (N = 62) we tested the effect of static vs. animated presentations on comprehension. In the second experiment (N = 45), we tested the effect of user-control of an animated…
The static characteristics of a torsionally flexible metal coupling
Directory of Open Access Journals (Sweden)
Krzysztof FILIPOWICZ
2008-01-01
Full Text Available The paper presents a description of test stands and the methodology ofdetermining the static characteristics of a metal coupling of high torsional flexibility. In addition, the paper presents preliminary tests results which enable to determine the above characteristics.
Real-Time Adaptive Least-Squares Drag Minimization for Performance Adaptive Aeroelastic Wing
Ferrier, Yvonne L.; Nguyen, Nhan T.; Ting, Eric
2016-01-01
This paper contains a simulation study of a real-time adaptive least-squares drag minimization algorithm for an aeroelastic model of a flexible wing aircraft. The aircraft model is based on the NASA Generic Transport Model (GTM). The wing structures incorporate a novel aerodynamic control surface known as the Variable Camber Continuous Trailing Edge Flap (VCCTEF). The drag minimization algorithm uses the Newton-Raphson method to find the optimal VCCTEF deflections for minimum drag in the context of an altitude-hold flight control mode at cruise conditions. The aerodynamic coefficient parameters used in this optimization method are identified in real-time using Recursive Least Squares (RLS). The results demonstrate the potential of the VCCTEF to improve aerodynamic efficiency for drag minimization for transport aircraft.
Energy Technology Data Exchange (ETDEWEB)
Anderson, M.B. [Renewable Energy Systems Ltd., Hemel Hempstead (United Kingdom)
1996-09-01
It is possible to compute the aeroelastic response of a horizontal axis wind turbine comprising; Structural: rotor substructure 144 dof, tower substructure 48 dof, induction, synchronous or variable speed, and gearbox. Aerodynamic: 3 blades (10 elements per blade), dynamic stall, and 6 different aerofoil types with combination of fixed or pitching elements. Control: stall or power regulation or speed control and shutdowns, wind shear, and tower shadow. Turbulence: 8 radial points, 32 circumferential, and 3 components. On a DEC Alpha Workstation the code will simulate the response inclose to real-time. As the code is presently formulated deflections from the initial starting point have to be small and therefore its ability to fully analyse very flexible structures is limited. (EG)
8th International Symposium on Unsteady Aerodynamics and Aeroelasticity of Turbomachines
1998-01-01
Twenty-one years have passed since the first symposium in this series was held in Paris (1976). Since then there have been meetings in Lausanne (1980), Cambridge (1984), Aachen (1987), Beijing (1989), Notre Dame (1991) and Fukuoka (1994). During this period a tremendous development in the field of unsteady aerodynamics and aeroelasticity in turbomachines has taken place. As steady-state flow conditions become better known, and as blades in the turbomachine are constantly pushed towards lower weight, and higher load and efficiency, the importance of unsteady phenomena appear more clearly. th The 8 Symposium was, as the previous ones, of high quality. Furthermore, it presented the audience with the latest developments in experimental, numerical and theoretical research. More papers than ever before were submitted to the conference. As the organising committee wanted to preserve the uniqueness of the symposium by having single sessions, and thus mingle speakers and audience with different backgrounds in this int...
DEFF Research Database (Denmark)
Aagaard Madsen, Helge; Larsen, Gunner Chr.; Larsen, Torben J.
2010-01-01
in an aeroelastic model. Calibration and validation of the different parts of the model is carried out by comparisons with actuator disk and actuator line (ACL) computations as well as with inflow measurements on a full-scale 2 MW turbine. It is shown that the load generating part of the increased turbulence......As the major part of new wind turbines are installed in clusters or wind farms, there is a strong need for reliable and accurate tools for predicting the increased loadings due to wake operation and the associated reduced power production. The dynamic wake meandering (DWM) model has been developed...... on this background, and the basic physical mechanisms in the wake—i.e., the velocity deficit, the meandering of the deficit, and the added turbulence—are modeled as simply as possible in order to make fast computations. In the present paper, the DWM model is presented in a version suitable for full integration...
Aeroelastic Stability of a 2D Airfoil Section equipped with a Trailing Edge Flap
DEFF Research Database (Denmark)
Bergami, Leonardo
Recent studies conclude that important reduction of the fatigue loads encountered by a wind turbine blade can be achieved using a deformable trailing edge control system. The focus of the current work is to determine the effect of this flap-like system on the aeroelastic stability of a 2D airfoil...... section. A simulation tool is implemented to predict the flow speed at which a flap equipped section may become unstable, either due to flutter or divergence. First, the stability limits of the airfoil without flap are determined, and, in the second part of the work, a deformable trailing edge flap...... is applied. Stability is investigated for the uncontrolled flap, and for three different control algorithms. The three controls are tuned for fatigue load alleviation and they are based on, respectively, measurement of the heave displacement and velocity, measurement of the local angle of attack, measurement...
DEFF Research Database (Denmark)
Døssing, Mads
During the last decades the annual energy produced by wind turbines has increased dramatically and wind turbines are now available in the 5MW range. Turbines in this range are constantly being developed and it is also being investigated whether turbines as large as 10-20MW are feasible. The design...... numerical modules, focus has been on analysis and a fundamental understanding of the key parameters in wind turbine design. This has resulted in insight and an eective design methodology is presented. Using the optimization environment a 5MW wind turbine rotor has been optimized for reduced fatigue loads...... due to apwise bending moments. Among other things this has indicated that airfoils for wind turbine blades should have a high lift coecient. The design methodology proved to be stable and a help in the otherwise challenging task of numerical aeroelastic optimization....
Aeroelastic research programme EFP-2001[YAW;STALL]; Forskning i aeroelasticitet EFP-2001
Energy Technology Data Exchange (ETDEWEB)
Aagaard Madsen, H. (ed.)
2002-12-01
The project covers the one year period from mid 2001 to mid 2002 and is the last part of a 5 years research programme on aeroelasticity. The overall objectives of the project are to improve the load and design basis for wind turbines and to ensure in collaboration with industry a continu-ously running process on development of new designs and solution of actual problems. Specifi-cally the main objectives for the present period are the following: a) development of a design tool for analysis of dynamic stability b) investigations of blade tip aerodynamics and blade tip design on basis of 3D CFD computa-tions c) publication of an airfoil catalogue d) load reduction using new control strategies e) aeroacoustic modelling of noise propagation During the present project period the computer code HAWCModal has been finished. The code computes the modal characteristics for a turbine as function of rotational speed. It is based on the structural modelling in the aeroelastic code HAWC and uses the same input files. The computed eigen frequencies are shown in a Campbell diagram and the corresponding modal forms can be shown graphically for an operating turbine. Finally, the structural damping is also computed by the code. HAWCModal is the basis for the stability analysis tool HAWCStab which is now under devel-opment. With HAWCStab the aeroelastic stability of a turbine can be analysed. The complex aerodynamics at three different blade tip shapes have been analysed with the three-dimensional CFD code EllipSys3D. The tip vortex was visualised and the lift and drag coef-ficients in the tip region were analysed in order to study the influence of the tip geometry on the performance and aerodynamic damping. An airfoil catalogue containing computations on 28 different airfoils for wind turbine applica-tion in comparison with experimental data has been developed and is available via the internet. Besides the main themes of the project as mentioned above there have been research
OC3—Benchmark Exercise of Aero-elastic Offshore Wind Turbine Codes
Passon, P.; Kühn, M.; Butterfield, S.; Jonkman, J.; Camp, T.; Larsen, T. J.
2007-07-01
This paper introduces the work content and status of the first international investigation and verification of aero-elastic codes for offshore wind turbines as performed by the "Offshore Code Comparison Collaboration"(OC3) within the "IEA Wind Annex XXIII - Subtask 2". An overview is given on the state-of-the-art of the concerned offshore wind turbine simulation codes. Exemplary results of benchmark simulations from the first phase of the project are presented and discussed while subsequent phases are introduced. Furthermore, the paper discusses areas where differences between the codes have been identified and the sources of those differences, such as the differing theories implemented into the individual codes. Finally, further research and code development needs are presented based on the latest findings from the current state of the project.
Aeroelastic Control of a Segmented Trailing Edge Using Fiber Optic Strain Sensing Technology
Graham, Corbin Jay; Martins, Benjamin; Suppanade, Nathan
2014-01-01
Currently, design of aircraft structures incorporate a safety factor which is essentially an over design to mitigate the risk of structure failure during operation. Typically this safety factor is to design the structure to withstand loads much greater than what is expected to be experienced during flight. NASA Dryden Flight Research Centers has developed a Fiber Optic Strain Sensing (FOSS) system which can measure strain values in real-time. The Aeroelastics Lab at the AERO Institute is developing a segmented trailing edged wing with multiple control surfaces that can utilize the data from the FOSS system, in conjunction with an adaptive controller to redistribute the lift across a wing. This redistribution can decrease the amount of strain experienced by the wing as well as be used to dampen vibration and reduce flutter.
A nonlinear computational aeroelasticity model for aircraft wings
Feng, Zhengkun
Cette these presente le developpement d'un code d'aeroelasticite nonlineaire base sur un solveur CFD robuste afin de l'appliquer aux ailes flexibles en ecoulement transsonique. Le modele mathematique complet est base sur les equations du mouvement des structures et les equations d'Euler pour les ecoulements transsoniques non-visqueux. La strategie de traiter tel systeme complexe par un couplage etage presente des avantages pour le developpement d'un code modulaire et facile a faire evoluer. La non-correspondance entre les deux grilles de calcul a l'interface fluide-structure, due aux differences des tailles et des types des elements utilises par la resolution de l'ecoulement et de la structure, est resolue par l'ajout d'un module specifique. Les transferts des informations entre ces deux grilles satisfont la loi de la conservation de l'energie. Le modele nonlineaire de la dynamique du fluide base sur la description Euler-Lagrange est discretise dans le maillage mobile. Le modele pour le calcul des structures est suppose lineaire dans lequel la methode de superposition modale est appliquee pour reduire le temps de calcul et la dimension de la memoire. Un autre modele pour la structure base directement sur la methode des elements finis est aussi developpe. Il est egalement couple dans le code pour prouver son extension future aux applications plus generales. La nonlinearite est une autre source de complexite du systeme bien que celle-ci est prevue uniquement dans le modele aerodynamique. L'algorithme GMRES nonlineaire avec le preconditioneur ILUT est implemente dans le solveur CFD ou un capteur de choc pour les ecoulements transsoniques et la technique de stabilisation numerique SUPG pour des ecoulements domines par la convection sont appliques. Un schema du second ordre est utilise pour la discretisation temporelle. Les composants de ce code sont valides par des tests numeriques. Le modele complet est applique et valide sur l'aile aeroelastique AGARD 445.6 dans le
Static and flicker perimetry in age-related macular degeneration.
Luu, Chi D; Dimitrov, Peter N; Wu, Zhichao; Ayton, Lauren N; Makeyeva, Galina; Aung, Khin-Zaw; Varsamidis, Mary; Robman, Luba; Vingrys, Algis J; Guymer, Robyn H
2013-05-01
The relationship between clinical severity of age-related macular degeneration (AMD) and macular function has not been well established. In this study, we investigated the correlation between clinical severity and functional deficits as detected by static and flicker perimetry. This cross-sectional study consisted of 279 AMD subjects and 24 control participants. AMD subjects were allocated into 1 of 10 AMD severity groups depending on the status of the designated study eye and the fellow eye, as assessed by color fundus photographs. Visual acuity, and static and flicker perimetry were tested on one eye during the same session. The geometric means, SDs, and percentage of abnormal eyes of static and flicker sensitivity of each AMD severity group were determined and compared. The pattern of change in sensitivity and percentage of abnormal eyes for static perimetry across all AMD severity groups were similar to flicker perimetry. Eyes with drusen > 125 μm (P[static] = 0.018, P[flicker] = 0.024), drusenoid epithelial detachment (P[static and flicker] flicker] flicker sensitivities compared to normal eyes. Static (β-coefficient -1.59, 95% confidence interval [CI] -4.78-1.60) and flicker (β-coefficient -1.29, 95% CI -4.66-2.08) sensitivities declined at a similar rate in eyes that showed clinical signs of progression. Static and flicker perimetry were affected similarly across the spectrum of AMD severity, and methods appeared to be valid techniques for assessing retinal sensitivity in AMD once drusen > 125 μm are present, but before the development of late AMD.
Statics of historic masonry constructions
Como, Mario
2016-01-01
This successful book, which is now appearing in its second edition, presents a comprehensive new Statics of Masonry Constructions. Masonry constructions are the great majority of the buildings in Europe’s historic centres and the most important monuments in its architectural heritage. Given the age of these constructions, the demand for safety assessments and restoration projects is pressing and constant. The book you hold in hands contributes to fill this demand. The second edition integrates the original text of the first edition with new developments, widening and revisions, due to recent research studies achievements. The result is a book that gives a complete picture of the behaviour of the Masonry Constructions. First of all, it gives the fundamentals of its Statics, based on the no-tension assumption, and then it develops the Limit Analysis for the Masonry Constructions. In this framework, through an interdisciplinary approach combining Engineering and Architecture, the book also investigates the sta...
Water cooled static pressure probe
Lagen, Nicholas T. (Inventor); Eves, John W. (Inventor); Reece, Garland D. (Inventor); Geissinger, Steve L. (Inventor)
1991-01-01
An improved static pressure probe containing a water cooling mechanism is disclosed. This probe has a hollow interior containing a central coolant tube and multiple individual pressure measurement tubes connected to holes placed on the exterior. Coolant from the central tube symmetrically immerses the interior of the probe, allowing it to sustain high temperature (in the region of 2500 F) supersonic jet flow indefinitely, while still recording accurate pressure data. The coolant exits the probe body by way of a reservoir attached to the aft of the probe. The pressure measurement tubes are joined to a single, larger manifold in the reservoir. This manifold is attached to a pressure transducer that records the average static pressure.
Size scaling of static friction.
Braun, O M; Manini, Nicola; Tosatti, Erio
2013-02-22
Sliding friction across a thin soft lubricant film typically occurs by stick slip, the lubricant fully solidifying at stick, yielding and flowing at slip. The static friction force per unit area preceding slip is known from molecular dynamics (MD) simulations to decrease with increasing contact area. That makes the large-size fate of stick slip unclear and unknown; its possible vanishing is important as it would herald smooth sliding with a dramatic drop of kinetic friction at large size. Here we formulate a scaling law of the static friction force, which for a soft lubricant is predicted to decrease as f(m)+Δf/A(γ) for increasing contact area A, with γ>0. Our main finding is that the value of f(m), controlling the survival of stick slip at large size, can be evaluated by simulations of comparably small size. MD simulations of soft lubricant sliding are presented, which verify this theory.
Fracture characterisation of float glass under static and dynamic loading
Directory of Open Access Journals (Sweden)
A. Nyounguè
2016-12-01
Full Text Available This paper presents the study of float glass fracture under static and dynamic loading, with the use of experimental and numerical fracture mechanics methods. It has been shown that the value of notch fracture toughness under static loading depends neither on the kind of test nor on specimen geometry. This makes it possible to replace the three-points-bending specimens with the Brazilian discs which are, under certain test conditions, simpler and convenient to study. For both types of specimens, an analysis of the fracture strength, the notch stress intensity factor and fragmentation of specimens was carried out.
Static and Dynamic Membrane Structures
Directory of Open Access Journals (Sweden)
Sergiu Ivanov
2012-10-01
Full Text Available While originally P systems were defined to contain multiset rewriting rules, it turned out that considering different types of rules may produce important results, such as increasing the computational power of the rules. This paper focuses on factoring out the concept of a membrane structure out of various P system models with the goal of providing useful formalisations. Both static and dynamic membrane structures are considered.
Homotheties of cylindrically symmetric static spacetimes
International Nuclear Information System (INIS)
Qadir, A.; Ziad, M.; Sharif, M.
1998-08-01
In this note we consider the homotheties of cylindrically symmetric static spacetimes. We find that we can provide a complete list of all metrics that admit non-trivial homothetic motions and are cylindrically symmetric static. (author)
Three Inexpensive Static-Electricity Demonstrations.
Gore, Gordon R.; Gregg, William R.
1992-01-01
Describes demonstrations to (1) construct an inexpensive static electricity detector; (2) obtain an abundant supply of either negative or positive charge using household items; and (3) create static electricity using a Tesla coil or Van de Graaff generator. (MDH)
Open-loop frequency response analysis of a wind turbine using a high-order linear aeroelastic model
DEFF Research Database (Denmark)
Sønderby, Ivan Bergquist; Hansen, Morten Hartvig
2014-01-01
generator torque and collective pitch control actions of a modern non-floating wind turbine based on a high-order linear model. The model is a linearization of a geometrically non-linear finite beam element model coupled with an unsteady blade element momentum model of aerodynamic forces including effects......Wind turbine controllers are commonly designed on the basis of low-order linear models to capture the aeroelastic wind turbine response due to control actions and disturbances. This paper characterizes the aeroelastic wind turbine dynamics that influence the open-loop frequency response from......-minimum phase zeros below the frequency of the first drivetrain mode. To correctly predict the non-minimum phase zeros, it is essential to include lateral tower and blade flap degrees of freedom. Copyright © 2013 John Wiley & Sons, Ltd....
30 CFR 18.26 - Static electricity.
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Static electricity. 18.26 Section 18.26 Mineral... § 18.26 Static electricity. Nonmetallic rotating parts, such as belts and fans, shall be provided with a means to prevent an accumulation of static electricity. ...
A Pedagogical Model of Static Friction
Pickett, Galen T.
2015-01-01
While dry Coulombic friction is an elementary topic in any standard introductory course in mechanics, the critical distinction between the kinetic and static friction forces is something that is both hard to teach and to learn. In this paper, I describe a geometric model of static friction that may help introductory students to both understand and apply the Coulomb static friction approximation.
Goldman, Benjamin D.; Dowell, Earl H.; Scott, Robert C.
2014-01-01
Conical shell theory and piston theory aerodynamics are used to study the aeroelastic stability of the thermal protection system (TPS) on the NASA Hypersonic Inflatable Aerodynamic Decelerator (HIAD). Structural models of the TPS consist of single or multiple orthotropic conical shell systems resting on several circumferential linear elastic supports. The shells in each model may have pinned (simply-supported) or elastically-supported edges. The Lagrangian is formulated in terms of the generalized coordinates for all displacements and the Rayleigh-Ritz method is used to derive the equations of motion. The natural modes of vibration and aeroelastic stability boundaries are found by calculating the eigenvalues and eigenvectors of a large coefficient matrix. When the in-flight configuration of the TPS is approximated as a single shell without elastic supports, asymmetric flutter in many circumferential waves is observed. When the elastic supports are included, the shell flutters symmetrically in zero circumferential waves. Structural damping is found to be important in this case. Aeroelastic models that consider the individual TPS layers as separate shells tend to flutter asymmetrically at high dynamic pressures relative to the single shell models. Several parameter studies also examine the effects of tension, orthotropicity, and elastic support stiffness.
Static mechanical properties of buffer material
International Nuclear Information System (INIS)
Takaji, Kazuhiko; Suzuki, Hideaki
1999-11-01
The buffer material is expected to maintain its low water permeability, self-sealing properties, radionuclides adsorption and retardation properties, thermal conductivity, chemical buffering properties, overpack supporting properties, stress buffering properties, etc. over a long period of time. Natural clay is mentioned as a material that can relatively satisfy above. Among the kinds of natural clay, bentonite when compacted is superior because (i) it has exceptionally low water permeability and properties to control the movement of water in buffer, (ii) it fills void spaces in the buffer and fractures in the host rock as it swells upon water uptake, (iii) it has the ability to exchange cations and to adsorb cationic radioelements. In order to confirm these functions for the purpose of safety assessment, it is necessary to evaluate buffer properties through laboratory tests and engineering-scale tests, and to make assessments based on the ranges in the data obtained. This report describes the procedures, test conditions, results and examinations on the buffer material of unconfined compression tests, one-dimensional consolidation tests, consolidated-undrained triaxial compression tests and consolidated-undrained triaxial creep tests that aim at getting hold of static mechanical properties. We can get hold of the relationship between the dry density and tensile stress etc. by Brazilian tests, between the dry density and unconfined compressive strength etc. by unconfined compression tests, between the consolidation stress and void ratio etc. by one-dimensional consolidation tests, the stress pass of each effective confining pressure etc. by consolidated-undrained triaxial compression tests and the axial strain rate with time of each axial stress etc. by consolidated-undrained triaxial creep tests. (author)
STATIC ANALYSIS OF LEAF SPRING
E VENUGOPAL GOUD; G HARINATH GOWD
2012-01-01
Leaf springs are special kind of springs used in automobile suspension systems. The advantage of leaf spring over helical spring is that the ends of the spring may be guided along a definite path as it deflects to act as a structural member in addition to energy absorbing device. The main function of leaf spring is not only tosupport vertical load but also to isolate road induced vibrations. It is subjected to millions of load cycles leading to fatigue failure. Static analysis determines the ...
Static Validation of Security Protocols
DEFF Research Database (Denmark)
Bodei, Chiara; Buchholtz, Mikael; Degano, P.
2005-01-01
We methodically expand protocol narrations into terms of a process algebra in order to specify some of the checks that need to be made in a protocol. We then apply static analysis technology to develop an automatic validation procedure for protocols. Finally, we demonstrate that these techniques ...... suffice to identify several authentication flaws in symmetric and asymmetric key protocols such as Needham-Schroeder symmetric key, Otway-Rees, Yahalom, Andrew secure RPC, Needham-Schroeder asymmetric key, and Beller-Chang-Yacobi MSR...
T-tail flutter: Potential-flow modelling, experimental validation and flight tests
Murua, Joseba; Martínez, Pablo; Climent, Héctor; van Zyl, Louw; Palacios, Rafael
2014-11-01
Flutter of T-tail configurations is caused by the aeroelastic coupling between the vertical fin and the horizontal stabiliser. The latter is mounted on the fin instead of the fuselage, and hence the arrangement presents distinct characteristics compared to other typical empennage setups; specifically, T-tail aeroelasticity is governed by inplane dynamics and steady aerodynamic loading, which are typically not included in flutter clearance methodologies based on the doublet lattice method. As the number of new aircraft featuring this tail configuration increases, there is a need for precise understanding of the phenomenon, appropriate tools for its prediction, and reliable benchmarking data. This paper addresses this triple challenge by providing a detailed explanation of T-tail flutter physics, describing potential-flow modelling alternatives, and presenting detailed numerical and experimental results to compensate for the shortage of reproducible data in the literature. A historical account of the main milestones in T-tail aircraft development is included, followed by a T-tail flutter research review that emphasises the latest contributions from industry as well as academia. The physical problem is dissected next, highlighting the individual and combined effects that drive the phenomenon. Three different methodologies, all based on potential-flow aerodynamics, are considered for T-tail subsonic flutter prediction: (i) direct incorporation of supplementary T-tail effects as additional terms in the flutter equations; (ii) a generalisation of the boundary conditions and air loads calculation on the double lattice; and (iii) a linearisation of the unsteady vortex lattice method with arbitrary kinematics. Comparison with wind-tunnel experimental results evidences that all three approaches are consistent and capture the key characteristics in the T-tail dynamics. The validated numerical models are then exercised in easy-to-duplicate canonical test cases. These
Effect of 8-week exerciseon improving the static and dynamic ...
African Journals Online (AJOL)
Before the training program of supinated legs of navicular drop test subjects, static balance and dynamic balance was measured with a force platform. The experimental group carried out exercises program for 8 weeks with a frequency of three times a week on the area of weak muscles and stretched legs, and the control ...
On the scaling of gas leakage from static seals
International Nuclear Information System (INIS)
Chivers, T.C.; Hunt, R.P.
1977-01-01
The interaction between gas leakage from static seals and eight potential variables is discussed. From a consideration of the interaction of these various parameters and the mechanical design of the seal system the importance of correctly interpreting leakage data is demonstrated. Given a situation where model experiments are necessary, this document forms a basis for the definition and interpretation of a test programme. (author)
Thickness effect in composite laminates in static and fatigue loading
Lahuerta Calahorra, F.
2017-01-01
Thick Laminates (above 6mm) are increasingly present in large composites structures such as wind turbine blades. Designs are based on static and fatigue coupon tests performed on 1-4mm thin laminates. However, a thickness effect has been observed in limited available experimental data. For this
Hubble expansion in static spacetime
International Nuclear Information System (INIS)
Rossler, Otto E.; Froehlich, Dieter; Movassagh, Ramis; Moore, Anthony
2007-01-01
A recently proposed mechanism for light-path expansion in a static spacetime is based on the moving-lenses paradigm. Since the latter is valid independently of whether space expands or not, a static universe can be used to better see the implications. The moving-lenses paradigm is related to the paradigm of dynamical friction. If this is correct, a Hubble-like law is implicit. It is described quantitatively. A bent in the Hubble-like line is predictably implied. The main underlying assumption is Price's Principle (PI 3 ). If the theory is sound, the greatest remaining problem in cosmology becomes the origin of hydrogen. Since Blandford's jet production mechanism for quasars is too weak, a generalized Hawking radiation hidden in the walls of cosmic voids is invoked. A second prediction is empirical: slow pattern changes in the cosmic microwave background. A third is ultra-high redshifts for Giacconi quasars. Bruno's eternal universe in the spirit of Augustine becomes a bit less outlandish
Directory of Open Access Journals (Sweden)
N. Carrasco
2014-09-01
Full Text Available Motivated by a recent paper by the RBC–UKQCD Collaboration, which observes large violations of the naïve factorization hypothesis in K→ππ decays, we study in this paper the accuracy of the Vacuum Insertion Approximation (VIA for the matrix elements of the complete basis of four-fermion ΔF=2 operators. We perform a comparison between the matrix elements in QCD, evaluated on the lattice, and the VIA predictions. We also investigate the dependence on the external meson masses by computing matrix elements for K, Ds, Bs and static mesons. In commonly used renormalization schemes, we find large violations of the VIA in particular for one of the two relevant Wick contractions in the kaon sector. These deviations, however, decrease significantly as the meson mass increases and the VIA predictions turn out to be rather well verified for B-meson matrix elements and, even better, in the infinite mass limit.
Innovative scaling laws for aeroelastic and aeroservoelastic problems in compressible flow
Presente, Eyal
Active flutter suppression of a two dimensional wing section in subsonic flow is studied. The equations of motion of a typical cross section are presented in nondimensional form. A two degree of freedom problem, with pitch and plunge dynamics, combined with a trailing-edge control surface is considered. Aerodynamic loads are expressed in the time-domain using Roger's approximation. Augmented aerodynamic states are reconstructed using a Kalman filter, and linear optimal control is used to design a full-state feedback regulator for flutter suppression. Recent advances in the area of adaptive materials, smart structures, have led to the use of such materials as actuators for aeroservoelastic applications. The attractiveness of such materials consists of their potential to introduce continuous structural deformations of the lifting surface that can be exploited to manipulate the unsteady aerodynamic loads and prevent undesirable aeroelastic effects such as flutter. A general formulation of the aerodynamic loads, based on thin airfoil theory, and the deformation of a flat plate wing section are used to calculate the amount of power required to twist a wing along its span with piezoelectric patches. Composite materials enhance bend/twist coupling, which is used to modify the aerodynamic loads for the purpose of flutter suppression. Scaling laws of aeroservoelastic systems are addressed. Scaling parameters required for maintaining similarity between a full-scale system and a model are studied. An innovative two-pronged approach is used to obtain "similarity solutions" of the aeroservoelastic problem. Changes of structural and aerodynamic variables between a full scale configuration and its scaled models facilitate similarity between the systems. Two cases of scaled models are examined, a geometrically scaled model and an aeroelastically scaled one. Flutter suppression of a typical cross section employing a trailing edge control surface is compared with that of a typical
Optimal aeroelastic trim for rotorcraft with constrained, non-unique trim solutions
Schank, Troy C.
New rotorcraft configurations are emerging, such as the optimal speed helicopter and slowed-rotor compound helicopter which, due to variable rotor speed and redundant lifting components, have non-unique trim solution spaces. The combination of controls and rotor speed that produce the best steady-flight condition is sought among all the possible solutions. This work develops the concept of optimal rotorcraft trim and explores its application to advanced rotorcraft configurations with non-unique, constrained trim solutions. The optimal trim work is based on the nonlinear programming method of the generalized reduced gradient (GRG) and is integrated into a multi-body, comprehensive aeroelastic rotorcraft code. In addition to the concept of optimal trim, two further developments are presented that allow the extension of optimal trim to rotorcraft with rotors that operate over a wide range of rotor speeds. The first is the concept of variable rotor speed trim with special application to rotors operating in steady autorotation. The technique developed herein treats rotor speed as a trim variable and uses a Newton-Raphson iterative method to drive the rotor speed to zero average torque simultaneously with other dependent trim variables. The second additional contribution of this thesis is a novel way to rapidly approximate elastic rotor blade stresses and strains in the aeroelastic trim analysis for structural constraints. For rotors that operate over large angular velocity ranges, rotor resonance and increased flapping conditions are encountered that can drive the maximum cross-sectional stress and strain to levels beyond endurance limits; such conditions must be avoided. The method developed herein captures the maximum cross-sectional stress/strain based on the trained response of an artificial neural network (ANN) surrogate as a function of 1-D beam forces and moments. The stresses/strains are computed simultaneously with the optimal trim and are used as constraints
Non-local means filter for trim statics
Huang, Yunsong
2014-08-05
Structures will be mispositioned across prestack migration gathers in the presence of inaccuracies in the velocity model. Stacking these misaligned gathers runs the risk of destroying important structures in the stacked migration image. To mitigate this problem, we propose a trim statics inspired by the non-local means algorithm originally developed for image denoising. This method differs from the conventional one in two fundamental respects. First, the trim statics are computed by comparing image patches instead of individual image traces. Second, no global pilot trace is needed because only two migration images at a time participate in trim statics and are stacked into one image. A multitude of migration images are stacked recursively in this two-to-one fashion. Tests with a Gulf of Mexico dataset show a noticeable improvement in the feature coherency of the stacked migration image.
Static structure of active Brownian hard disks
de Macedo Biniossek, N.; Löwen, H.; Voigtmann, Th; Smallenburg, F.
2018-02-01
We explore the changes in static structure of a two-dimensional system of active Brownian particles (ABP) with hard-disk interactions, using event-driven Brownian dynamics simulations. In particular, the effect of the self-propulsion velocity and the rotational diffusivity on the orientationally-averaged fluid structure factor is discussed. Typically activity increases structural ordering and generates a structure factor peak at zero wave vector which is a precursor of motility-induced phase separation. Our results provide reference data to test future statistical theories for the fluid structure of active Brownian systems. This manuscript was submitted for the special issue of the Journal of Physics: Condensed Matter associated with the Liquid Matter Conference 2017.
Static analysis of an office desk construction
Directory of Open Access Journals (Sweden)
Milan Novotný
2011-01-01
Full Text Available The objective of the paper is a static analysis of a desk construction and the determination of its probable mechanical behaviour using Finite Element Method. The construction was modelled and numerically analysed in Autocad Inventor 2011 and the stability of the entire desk was calculated with the size and placement of the loading force based on the standards and cited literature. Possible locations and directions of the deformation were analysed and a solution for its prevention was proposed and the stability of the desk as well as the extreme position of the stand were calculated. The verification of the obtained results in an accredited furniture testing lab is planned using a prototype of the office desk.
The Predictive Validity of the Static-99, Static-99R, and Static-2002/R: Which One to Use?
Reeves, Sophie G; Ogloff, James R P; Simmons, Melanie
2017-06-01
The use of Static tools (Static-99, Static-99R, Static-2002, and Static-2002R) in risk decision making involving sexual offenders is widespread internationally. This study compared the predictive accuracy and incremental validity of four Static risk measures in a sample of 621 Australian sexual offenders. Results indicated that approximately 45% of the sample recidivated (with 18.8% committing sexual offenses). All of the Static measures investigated yielded moderate predictive validity for sexual recidivism, which was comparable with other Australian and overseas studies. Area under the curve (AUC) values for the four measures across the 5-, 10-, and 15-year intervals ranged from .67 to .69. All of the Static measures discriminated quite well between low-risk and high-risk sexual offenders but less well for the moderate risk categories. When pitted together, none of the tools accounted for additional variance in sexual recidivism, above and beyond what the other measures accounted for. The overall results provide support for the use of Static measures as a component of risk assessment and decision making with Australian sexual offending populations. The limitations of this study and recommendations for further research are also discussed.
Dynamic and Static Assessment of Phonological Awareness in Preschool: A Behavior-Genetic Study
Coventry, William L.; Byrne, Brian; Olson, Richard K.; Corley, Robin; Samuelsson, Stefan
2011-01-01
The genetic and environmental overlap between static and dynamic measures of preschool phonological awareness (PA) and their relation to preschool letter knowledge (LK) and kindergarten reading were examined using monozygotic and dizygotic twin children (maximum N = 1,988). The static tests were those typically used to assess a child's current…
Statics learning from engineering examples
Emri, Igor
2016-01-01
This textbook introduces and explains the basic concepts on which statics is based utilizing real engineering examples. The authors emphasize the learning process by showing a real problem, analyzing it, simplifying it, and developing a way to solve it. This feature teaches students intuitive thinking in solving real engineering problems using the fundamentals of Newton’s laws. This book also: · Stresses representation of physical reality in ways that allow students to solve problems and obtain meaningful results · Emphasizes identification of important features of the structure that should be included in a model and which features may be omitted · Facilitates students' understanding and mastery of the "flow of thinking" practiced by professional engineers.
Wing aeroelasticity analysis based on an integral boundary-layer method coupled with Euler solver
Directory of Open Access Journals (Sweden)
Ma Yanfeng
2016-10-01
Full Text Available An interactive boundary-layer method, which solves the unsteady flow, is developed for aeroelastic computation in the time domain. The coupled method combines the Euler solver with the integral boundary-layer solver (Euler/BL in a “semi-inverse” manner to compute flows with the inviscid and viscous interaction. Unsteady boundary conditions on moving surfaces are taken into account by utilizing the approximate small-perturbation method without moving the computational grids. The steady and unsteady flow calculations for the LANN wing are presented. The wing tip displacement of high Reynolds number aero-structural dynamics (HIRENASD Project is simulated under different angles of attack. The flutter-boundary predictions for the AGARD 445.6 wing are provided. The results of the interactive boundary-layer method are compared with those of the Euler method and experimental data. The study shows that viscous effects are significant for these cases and the further data analysis confirms the validity and practicability of the coupled method.
Gupta, K. K.
1997-01-01
A multidisciplinary, finite element-based, highly graphics-oriented, linear and nonlinear analysis capability that includes such disciplines as structures, heat transfer, linear aerodynamics, computational fluid dynamics, and controls engineering has been achieved by integrating several new modules in the original STARS (STructural Analysis RoutineS) computer program. Each individual analysis module is general-purpose in nature and is effectively integrated to yield aeroelastic and aeroservoelastic solutions of complex engineering problems. Examples of advanced NASA Dryden Flight Research Center projects analyzed by the code in recent years include the X-29A, F-18 High Alpha Research Vehicle/Thrust Vectoring Control System, B-52/Pegasus Generic Hypersonics, National AeroSpace Plane (NASP), SR-71/Hypersonic Launch Vehicle, and High Speed Civil Transport (HSCT) projects. Extensive graphics capabilities exist for convenient model development and postprocessing of analysis results. The program is written in modular form in standard FORTRAN language to run on a variety of computers, such as the IBM RISC/6000, SGI, DEC, Cray, and personal computer; associated graphics codes use OpenGL and IBM/graPHIGS language for color depiction. This program is available from COSMIC, the NASA agency for distribution of computer programs.
Constrained adaptive neural network control of an MIMO aeroelastic system with input nonlinearities
Directory of Open Access Journals (Sweden)
Yiyong Gou
2017-04-01
Full Text Available A constrained adaptive neural network control scheme is proposed for a multi-input and multi-output (MIMO aeroelastic system in the presence of wind gust, system uncertainties, and input nonlinearities consisting of input saturation and dead-zone. In regard to the input nonlinearities, the right inverse function block of the dead-zone is added before the input nonlinearities, which simplifies the input nonlinearities into an equivalent input saturation. To deal with the equivalent input saturation, an auxiliary error system is designed to compensate for the impact of the input saturation. Meanwhile, uncertainties in pitch stiffness, plunge stiffness, and pitch damping are all considered, and radial basis function neural networks (RBFNNs are applied to approximate the system uncertainties. In combination with the designed auxiliary error system and the backstepping control technique, a constrained adaptive neural network controller is designed, and it is proven that all the signals in the closed-loop system are semi-globally uniformly bounded via the Lyapunov stability analysis method. Finally, extensive digital simulation results demonstrate the effectiveness of the proposed control scheme towards flutter suppression in spite of the integrated effects of wind gust, system uncertainties, and input nonlinearities.
Effects of mean flow on transmission loss of orthogonally rib-stiffened aeroelastic plates.
Xin, F X; Lu, T J
2013-06-01
This paper investigates the sound transmission loss (STL) of aeroelastic plates reinforced by two sets of orthogonal rib-stiffeners in the presence of external mean flow. Built upon the periodicity of the structure, a comprehensive theoretical model is developed by considering the convection effect of mean flow. The rib-stiffeners are modeled by employing the Bernoulli-Euler beam theory and the torsional wave equation. While the solution for the transmission loss of the structure based on plate displacement and acoustic pressures is given in the form of space-harmonic series, the corresponding coefficients are obtained from the solution of a system of linear equations derived from the plate-beam coupling vibration governing equation and Helmholtz equation. The model predictions are validated by comparing with existing theoretical and experimental results in the absence of mean flow. A parametric study is subsequently performed to quantify the effects of mean flow as well as structure geometrical parameters upon the transmission loss. It is demonstrated that the transmission loss of periodically rib-stiffened structure is increased significantly with increasing Mach number of mean flow over a wide frequency range. The STL value for the case of sound wave incident downstream is pronouncedly larger than that associated with sound wave incident upstream.
Jha, Sourabh; Crittenden, Thomas; Glezer, Ari
2017-11-01
The limits of low Reynolds number forced convection heat transport within rectangular, mm-scale channels that model segments of air-cooled heat sinks are overcome by the deliberate formation of unsteady small-scale vortical motions that are induced by autonomous aero-elastic fluttering of cantilevered planar thin-film reeds. The coupled flow-structure interactions between the fluttering reeds and the embedding channel flow and the formation and evolution of the induced unsteady small-scale vortical motions are explored using video imaging and PIV. Concave/convex undulations of the reed's surface that are bounded by the channel's walls lead to the formation and advection of cells of vorticity concentration and ultimately to alternate shedding of spanwise CW and CCW vortices. These vortices scale with the channel height, and result in increased turbulent kinetic energy and enhanced dissipation that persist far downstream from the reed and are reminiscent of a turbulent flow at significantly higher Reynolds numbers (e.g., at Re = 800, TKE increases by 86% ,40 channel widths downstream of reed tip). These small-scale motions lead to strong enhancement in heat transfer that increases with Re (e.g., at Re = 1,000 and 14,000, Nu increases by 36% and 91%, respectively). The utility of this approach is demonstrated in improving the thermal performance of low-Re heat sinks in air-cooled condensers of thermoelectric power plants. NSF-EPRI.
Quasi-Static Viscoelasticity Loading Measurements of an Aircraft Tire
Mason, Angela J.; Tanner, John A.; Johnson, Arthur R.
1997-01-01
Stair-step loading, cyclic loading, and long-term relaxation tests were performed on an aircraft tire to observe the quasi-static viscoelastic response of the tire. The data indicate that the tire continues to respond viscoelastically even after it has been softened by deformation. Load relaxation data from the stair-step test at the 15,000-lb loading was fit to a monotonically decreasing Prony series.
Pulsed Current Static Electrical Contact Experiment
National Research Council Canada - National Science Library
Jones, Harry N; Neri, Jesse M; Boyer, Craig N; Cooper, Khershed P; Meger, Robert A
2006-01-01
Railguns involve both static and sliding electrical contacts, which must transmit the large transient electrical currents necessary to impart high forces onto a projectile for acceleration to hypervelocity...
Effects of Static Stretching and Playing Soccer on Knee Laxity.
Baumgart, Christian; Gokeler, Alli; Donath, Lars; Hoppe, Matthias W; Freiwald, Jürgen
2015-11-01
This study investigated exercise-induced effects of static stretching and playing soccer on anterior tibial translation (ATT) of the knee joint. Randomized controlled trial. University biomechanics laboratory. Thirty-one athletes were randomly assigned into a stretching (26.9 ± 6.2 years, 1.77 ± 0.09 m, 67.9 ± 10.7 kg) and a control group (27.9 ± 7.4 years, 1.75 ± 0.08 m, 72.0 ± 14.9 kg). Thirty-one amateur soccer players in an additional soccer group (25.1 ± 5.6 years, 1.74 ± 0.10 m, 71.8 ± 14.8 kg). All participants had no history of knee injury requiring surgery and any previous knee ligament or cartilage injury. The stretching group performed 4 different static stretching exercises with a duration of 2 × 20 seconds interspersed with breaks of 10 seconds. The soccer group completed a 90-minute soccer-specific training program. The control group did not perform any physical activity for approximately 30 minutes. Anterior tibial translation was measured with the KT-1000 knee arthrometer at forces of 67 N, 89 N, and maximal manual force (Max) before and after the intervention. There was a significant increase in ATT after static stretching and playing soccer at all applied forces. Maximal manual testing revealed a mean increase of ATT after static stretching of 2.1 ± 1.6 mm (P static stretching at 67 and 89 N is significantly higher than in controls. At maximum manual testing, significant differences were evident between all groups. Static stretching and playing soccer increase ATT and may consequently influence mechanical factors of the anterior cruciate ligament. The ATT increase after static stretching was greater than after playing soccer. The observed increase in ATT after static stretching and playing soccer may be associated with changes in kinesthetic perception and sensorimotor control, activation of muscles, joint stability, overall performance, and higher injury risk.
2016-08-03
channel was increased gradually (at a rate of about 16 cm/sec/sec) using a flow controller that is built into the air supply (cf., §III.3.1) while...integrated film heaters (operating in constant heat flux, cf, §III.3.1). The heat flux to the heaters was varied over a range of flow rates (2,000...AFRL-AFOSR-VA-TR-2016-0339 Enhanced convection heat transfer using small-scale vorticity concentrations effected by flow -driven, aeroelastically
Static Material Strength Determined Using a DAC
Energy Technology Data Exchange (ETDEWEB)
Cynn, H; Evans, W; Klepeis, J P; Lipp, M; Liermann, P; Yang, W
2009-06-04
By measuring sample thickness and pressure gradient using x-ray absorption and x-ray diffraction, respectively, the accurate static yield strengths of Ta and Fe were determined at high pressure. This improved method has several advantages over other similar methods to quantitatively determine static material strength.
Static domain wall in braneworld gravity
Energy Technology Data Exchange (ETDEWEB)
Abdalla, M.C.B.; Carlesso, P.F. [UNESP, Universidade Estadual Paulista, Instituto de Fisica Teiorica, Rua Dr. Bento Teobaldo Ferraz 271, Bloco II, Barra-Funda, Caixa Postal 70532-2, Sao Paulo, SP (Brazil); Hoff da Silva, J.M. [UNESP, Universidade Estadual Paulista, Departamento de Fisica e Quimica, Guaratingueta, SP (Brazil)
2014-01-15
In this paper we consider a static domain wall inside a 3-brane. Different from the standard achievement obtained in General Relativity, the analysis performed here gives a consistency condition for the existence of static domain walls in a braneworld gravitational scenario. Also the behavior of the domain wall's gravitational field in the newtonian limit is shown. (orig.)
Static multiplicities in heterogeneous azeotropic distillation sequences
DEFF Research Database (Denmark)
Esbjerg, Klavs; Andersen, Torben Ravn; Jørgensen, Sten Bay
1998-01-01
different static behavior. The method of Petlyuk and Avet'yan (1971), Bekiaris et al. (1993), which assumes infinite reflux and infinite number of stages, is extended to and applied on heterogeneous azeotropic distillation sequences. The predictions are substantiated through simulations. The static sequence...
Automatic incrementalization of Prolog based static analyses
DEFF Research Database (Denmark)
Eichberg, Michael; Kahl, Matthias; Saha, Diptikalyan
2007-01-01
Modem development environments integrate various static analyses into the build process. Analyses that analyze the whole project whenever the project changes are impractical in this context. We present an approach to automatic incrementalization of analyses that are specified as tabled logic...... incrementalizing a broad range of static analyses....
Optimal Static Range Reporting in One Dimension
DEFF Research Database (Denmark)
Alstrup, Stephen; Brodal, Gerth Stølting; Rauhe, Theis
2001-01-01
We consider static one dimensional range searching problems. These problems are to build static data structures for an integer set S \\subseteq U, where U = \\{0,1,\\dots,2^w-1\\}, which support various queries for integer intervals of U. For the query of reporting all integers in S contained within...
Static Complexity Analysis of Higher Order Programs
DEFF Research Database (Denmark)
Avery, James Emil; Kristiansen, Lars; Moyen, Jean-Yves
2009-01-01
The overall goal of the research presented in this paper is to find^Mautomatic methods for static complexity analysis of higher order^Mprograms.......The overall goal of the research presented in this paper is to find^Mautomatic methods for static complexity analysis of higher order^Mprograms....
Static response of deformable microchannels
Christov, Ivan C.; Sidhore, Tanmay C.
2017-11-01
Microfluidic channels manufactured from PDMS are a key component of lab-on-a-chip devices. Experimentally, rectangular microchannels are found to deform into a non-rectangular cross-section due to fluid-structure interactions. Deformation affects the flow profile, which results in a nonlinear relationship between the volumetric flow rate and the pressure drop. We develop a framework, within the lubrication approximation (l >> w >> h), to self-consistently derive flow rate-pressure drop relations. Emphasis is placed on handling different types of elastic response: from pure plate-bending, to half-space deformation, to membrane stretching. The ``simplest'' model (Stokes flow in a 3D rectangular channel capped with a linearly elastic Kirchhoff-Love plate) agrees well with recent experiments. We also simulate the static response of such microfluidic channels under laminar flow conditions using ANSYSWorkbench. Simulations are calibrated using experimental flow rate-pressure drop data from the literature. The simulations provide highly resolved deformation profiles, which are difficult to measure experimentally. By comparing simulations, experiments and our theoretical models, we show good agreement in many flow/deformation regimes, without any fitting parameters.
Remote histology learning from static versus dynamic microscopic images.
Mione, Sylvia; Valcke, Martin; Cornelissen, Maria
2016-05-06
Histology is the study of microscopic structures in normal tissue sections. Curriculum redesign in medicine has led to a decrease in the use of optical microscopes during practical classes. Other imaging solutions have been implemented to facilitate remote learning. With advancements in imaging technologies, learning material can now be digitized. Digitized microscopy images can be presented in either a static or dynamic format. This study of remote histology education identifies whether dynamic pictures are superior to static images for the acquisition of histological knowledge. Test results of two cohorts of second-year Bachelor in Medicine students at Ghent University were analyzed in two consecutive academic years: Cohort 1 (n = 190) and Cohort 2 (n = 174). Students in Cohort 1 worked with static images whereas students in Cohort 2 were presented with dynamic images. ANCOVA was applied to study differences in microscopy performance scores between the two cohorts, taking into account any possible initial differences in prior knowledge. The results show that practical histology scores are significantly higher with dynamic images as compared to static images (F (1,361) = 15.14, P Association of Anatomists. © 2015 American Association of Anatomists.
Deformation behavior of welded steel sandwich panels under quasi-static loading
2011-03-01
This report describes engineering studies that were conducted to examine the deformation behavior of flat, welded steel sandwich panels under two quasi-static loading conditions: (1) uniaxial compression; and (2) bending with an indenter. Testing and...
Effects of Dynamic and Static Stretching Within General and Activity Specific Warm-Up Protocols
Samson, Michael; Button, Duane C.; Chaouachi, Anis; Behm, David G.
2012-01-01
The purpose of the study was to determine the effects of static and dynamic stretching protocols within general and activity specific warm-ups. Nine male and ten female subjects were tested under four warm-up conditions including a 1) general aerobic warm-up with static stretching, 2) general aerobic warm-up with dynamic stretching, 3) general and specific warm-up with static stretching and 4) general and specific warm-up with dynamic stretching. Following all conditions, subjects were tested...
Predicting vertebral bone strength by vertebral static histomorphometry
DEFF Research Database (Denmark)
Thomsen, Jesper Skovhus; Ebbesen, Ebbe Nils; Mosekilde, Lis
2002-01-01
of the entire vertebral bodies (L-2) were used for histomorphometry. The other iliac crest biopsies and the L-3 were destructively tested by compression. High correlation was found between BV/TV or Tb.Sp and vertebral bone strength (absolute value of r = 0.86 in both cases). Addition of Tb.Th significantly....... No gender-related differences were found in any of the relationships. Neither static histomorphometry nor biomechanical testing of iliac crest bone biopsies is a good predictor of vertebral bone strength.......The study investigates the relationship between static histomorphometry and bone strength of human lumbar vertebral bone. The ability of vertebral histomorphometry to predict vertebral bone strength was compared with that of vertebral densitometry, and also with histomorphometry and bone strength...
Strategy for Alternative Occupant Volume Testing
2009-10-20
This paper describes plans for a series of quasi-static : compression tests of rail passenger equipment. These tests are : designed to evaluate the strength of the occupant volume under : static loading conditions. The research plan includes a detail...
Design, development, and testing of a mini solid state adaptive rotor
Barrett, Ronald M.; Schliesman, Michael; Frye, Phillip
1997-06-01
The design principles, analytical models, construction methods and test results for a new type of solid state adaptive rotor (SSAR) are presented. A pair of directionally attached piezoelectric (DAP) torque-plates were fabricated and attached to the root of a 23.5' diameter helicopter rotor assembly. The DAP torque-plate tips were joined to a pair of graphite-epoxy servopaddles which were moved in pitch by the action of the torque-plates. The torque-plates were constructed from a single aluminum substrate and PZT-5H DAP elements mounted symmetrically at 45 degrees. Electrical signals were carried to the DAP torque-plates via a shielded brush and rotating contact assembly. A series of non-rotating static tests were conducted on the rotor, demonstrating servopaddle pitch deflections up to plus or minus 5.8 degrees and good correlation with classical laminated plate theory. Non rotating dynamic testing showed a system natural frequency in excess of 2.5/rev and good correlation with inertial models. Because the servopaddles were aeroelastically tailored to balance out propeller moments, deflection degradation with increasing rotor speed was barely noticeable up to plus or minus 1 degree pitch levels. However, as rotor speed increased, total servopaddle deflections in the rotating frame at 1600 rpm (full speed) were degraded, but still operated up to plus or minus 2.7 degrees in pitch. To conclude the study, the rotor was attached to a converted Kyosho Hyperfly electric helicopter. Flight tests demonstrated fundamental controllability. A system-level comparison showed that the SSAR Hyperfly experienced a 40% drop in flight control system weight, an 8% cut in total gross weight, a 26% decrease in parasite drag and a part count reduction from 94 components to 5.
DEFF Research Database (Denmark)
Barlas, Thanasis K.; van Wingerden, W.; Hulskamp, A.W.
2013-01-01
In this paper, the proof of concept of a smart rotor is illustrated by aeroelastic simulations on a small-scale rotor and comparison with wind tunnel experiments. The application of advanced feedback controllers using actively deformed flaps in the wind tunnel measurements is shown to alleviate d...
Byun, Chansup; Guruswamy, Guru P.; Kutler, Paul (Technical Monitor)
1994-01-01
In recent years significant advances have been made for parallel computers in both hardware and software. Now parallel computers have become viable tools in computational mechanics. Many application codes developed on conventional computers have been modified to benefit from parallel computers. Significant speedups in some areas have been achieved by parallel computations. For single-discipline use of both fluid dynamics and structural dynamics, computations have been made on wing-body configurations using parallel computers. However, only a limited amount of work has been completed in combining these two disciplines for multidisciplinary applications. The prime reason is the increased level of complication associated with a multidisciplinary approach. In this work, procedures to compute aeroelasticity on parallel computers using direct coupling of fluid and structural equations will be investigated for wing-body configurations. The parallel computer selected for computations is an Intel iPSC/860 computer which is a distributed-memory, multiple-instruction, multiple data (MIMD) computer with 128 processors. In this study, the computational efficiency issues of parallel integration of both fluid and structural equations will be investigated in detail. The fluid and structural domains will be modeled using finite-difference and finite-element approaches, respectively. Results from the parallel computer will be compared with those from the conventional computers using a single processor. This study will provide an efficient computational tool for the aeroelastic analysis of wing-body structures on MIMD type parallel computers.
Delaminations in composite plates under transverse static loads - Experimental results
Finn, Scott R.; He, Yi-Fei; Springer, George S.
1992-01-01
Tests were performed measuring the damage initiation loads and the locations, shapes, and sizes of delaminations in Fiberite T300/976 graphite/epoxy, Fiberite IM7/977-2 graphite-toughened epoxy, and ICI APC-2 graphite-PEEK plates subjected to transverse static loads. The data were compared to the results of the Finn-Springer model, and good agreements were found between the measured and calculated delamination lengths and widths.