A Hybrid Method for Full Spectrum Noise and Vibration Prediction

2003 ◽  
Vol 11 (02) ◽  
pp. 323-338 ◽  
Author(s):  
P. J. Shorter ◽  
B. K. Gardner ◽  
P. G. Bremner
Keyword(s):  
Spatial Statistics ◽  
Dynamic Properties ◽  
Hybrid Approach ◽  
Essential Element ◽  
Experimental Investigations ◽  
Local Dynamic ◽  
Local Motion ◽  
Local Modes ◽  
Numerical Predictions ◽  
Vibration Prediction

Predicting the response of a complex structural-acoustic system across a broad frequency range presents a number of challenges to an analyst. It is quite common to find that the uncertainty associated with the local dynamic properties of various subsystems of a system can vary greatly across the system. It is also common to find that the modal density and wavenumber content of the various subsystems can vary greatly across the system. Typically, this results in a mixture of strongly phase correlated (long wavelength) motion which spans many subsystems, superimposed with weakly phase correlated local motion that is confined to individual subsystems. This mismatch in the local statistical and dynamic properties of a system is often referred to as the mid-frequency problem. This paper provides a qualitative definition of the mid-frequency problem and suggests that a statistical description of the local dynamic properties of a system is an essential element of any mid-frequency prediction method. A hybrid approach to the mid-frequency problem is then described which employs a statistical description of the local modal properties of various subsystems in a system. The spatial statistics of the local modes are of particular interest and the way in which these statistics are encompassed in the hybrid analysis is discussed. Experimental investigations of the spatial statistics of a frame-panel structure are then presented and measurements of the acoustic power radiated by the structure are compared with numerical predictions.

scholarly journals A Two-Step Hybrid Approach for Modeling the Nonlinear Dynamic Response of Piezoelectric Energy Harvesters

2018 ◽  
Vol 2018 ◽  
pp. 1-21 ◽  
Author(s):  
Claudio Maruccio ◽  
Giuseppe Quaranta ◽  
Pasquale Montegiglio ◽  
Francesco Trentadue ◽  
Giuseppe Acciani
Keyword(s):  
Dynamic Response ◽  
Nonlinear Dynamic ◽  
Hybrid Approach ◽  
Experimental Investigations ◽  
Geometrical Parameters ◽  
Nonlinear Dynamic Response ◽  
Energy Harvesters ◽  
Global Dynamic ◽  
Numerical Predictions ◽  
Piezoelectric Energy

An effective hybrid computational framework is described here in order to assess the nonlinear dynamic response of piezoelectric energy harvesting devices. The proposed strategy basically consists of two steps. First, fully coupled multiphysics finite element (FE) analyses are performed to evaluate the nonlinear static response of the device. An enhanced reduced-order model is then derived, where the global dynamic response is formulated in the state-space using lumped coefficients enriched with the information derived from the FE simulations. The electromechanical response of piezoelectric beams under forced vibrations is studied by means of the proposed approach, which is also validated by comparing numerical predictions with some experimental results. Such numerical and experimental investigations have been carried out with the main aim of studying the influence of material and geometrical parameters on the global nonlinear response. The advantage of the presented approach is that the overall computational and experimental efforts are significantly reduced while preserving a satisfactory accuracy in the assessment of the global behavior.

Influence of a Honeycomb Facing on the Flow Through a Stepped Labyrinth Seal

2000 ◽  
Vol 124 (1) ◽  
pp. 140-146 ◽  
Author(s):  
V. Schramm ◽  
K. Willenborg ◽  
S. Kim ◽  
S. Wittig
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Theoretical Work ◽  
Labyrinth Seal ◽  
Honeycomb Structure ◽  
Experimental Investigations ◽  
Labyrinth Seals ◽  
Numerical Predictions ◽  
Flow Through ◽  
Aero Engines

This paper reports numerical predictions and measurements of the flow field in a stepped labyrinth seal. The theoretical work and the experimental investigations were successfully combined to gain a comprehensive understanding of the flow patterns existing in such elements. In order to identify the influence of the honeycomb structure, a smooth stator as well as a seal configuration with a honeycomb facing mounted on the stator wall were investigated. The seal geometry is representative of typical three-step labyrinth seals of modern aero engines. The flow field was predicted using a commercial finite volume code with the standard k-ε turbulence model. The computational grid includes the basic seal geometry as well as the three-dimensional honeycomb structures.

Numerical and Experimental Investigations on Preload Effects in Air Foil Journal Bearings

2017 ◽  
Author(s):  
Marcel Mahner ◽  
Pu Li ◽  
Andreas Lehn ◽  
Bernhard Schweizer
Keyword(s):  
Reynolds Equation ◽  
Journal Bearing ◽  
Journal Bearings ◽  
Compressible Fluids ◽  
Experimental Investigations ◽  
Hysteresis Curves ◽  
Numerical Predictions ◽  
Bearing Stiffness ◽  
Gasdynamic Model ◽  
Good Agreement

A detailed elasto-gasdynamic model of a preloaded three-pad air foil journal bearing is presented. Bump and top foil deflections are herein calculated with a nonlinear beamshell theory according to Reissner. The 2D pressure distribution in each bearing pad is described by the Reynolds equation for compressible fluids. With this model, the influence of the assembly preload on the static bearing hysteresis as well as on the aerodynamic bearing performance is investigated. For the purpose of model validation, the predicted hysteresis curves are compared with measured curves. The numerically predicted and the measured hysteresis curves show a good agreement. The numerical predictions exhibit that the assembly preload increases the bearing stiffness (in particular for moderate shaft displacements) and the bearing damping.

Futuristic Research Perspectives of IoT Platforms

2022 ◽  
pp. 258-275
Author(s):  
Dhaya R. ◽  
Kanthavel R.
Keyword(s):  
Power Management ◽  
Technology Development ◽  
Hybrid Approach ◽  
Essential Element ◽  
Digital Transformation ◽  
Security Education ◽  
Research Perspectives ◽  
Iot Platforms ◽  
Development Objectives ◽  
Innovation Patterns

Future IoT innovation patterns will assist offices with getting the greatest proficiency and efficiency out of their hardware and assembling parts. IoT is an essential element of digital transformation enterprises in business and industrial sections. Service suppliers and utilities have also been taking on IoT to get pioneering services to keep competitive. Services with security, power management, asset presentation, healthcare effectiveness, and threat and agreement management must be resolved properly in order to enhance the IoT effectively and efficiently. As new tech turns up, hackers prepare to capture the benefits of its potential flaws, and this is precisely why enhancing the precautions of associated strategy is the top IoT technology development. Objectives of this chapter are to analyze and access the future of IoT in healthcare, security, education, and agriculture. This chapter will focus on edge computing, a hybrid approach to process the data that allows connected devices to distribute, compute, examine, and maintain data locally.

scholarly journals Numerical and experimental investigations of buffet on a diamond airfoil designed for space launcher applications

2019 ◽  
Vol 30 (9) ◽  
pp. 4203-4218
Author(s):  
Jéromine Dumon ◽  
Yannick Bury ◽  
Nicolas Gourdain ◽  
Laurent Michel
Keyword(s):  
Shock Wave ◽  
Chaotic Behavior ◽  
Navier Stokes ◽  
Experimental Investigations ◽  
Fluid Structure ◽  
Content Type ◽  
Eddy Simulation ◽  
Numerical Predictions ◽  
Comprehensive Knowledge ◽  
Flow Effects

Purpose The development of reusable space launchers requires a comprehensive knowledge of transonic flow effects on the launcher structure, such as buffet. Indeed, the mechanical integrity of the launcher can be compromised by shock wave/boundary layer interactions, that induce lateral forces responsible for plunging and pitching moments. Design/methodology/approach This paper aims to report numerical and experimental investigations on the aerodynamic and aeroelastic behavior of a diamond airfoil, designed for microsatellite-dedicated launchers, with a particular interest for the fluid/structure interaction during buffeting. Experimental investigations based on Schlieren visualizations are conducted in a transonic wind tunnel and are then compared with numerical predictions based on unsteady Reynolds averaged Navier–Stokes and large eddy simulation (LES) approaches. The effect of buffeting on the structure is finally studied by solving the equation of the dynamics. Findings Buffeting is both experimentally and numerically revealed. Experiments highlight 3D oscillations of the shock wave in the manner of a wind-flapping flag. LES computations identify a lambda-shaped shock wave foot width oscillations, which noticeably impact aerodynamic loads. At last, the experiments highlight the chaotic behavior of the shock wave as it shifts from an oscillatory periodic to an erratic 3D flapping state. Fluid structure computations show that the aerodynamic response of the airfoil tends to damp the structural vibrations and to mitigate the effect of buffeting. Originality/value While buffeting has been extensively studied for classical supercritical profiles, this study focuses on diamond airfoils. Moreover, a fluid structure computation has been conducted to point out the effect of buffeting.

Determination of Engine Roughness Using Multi-Physics Numerical Predictions

2005 ◽  
Author(s):  
M. Perera ◽  
S. Theodossiades ◽  
H. Rahnejat
Keyword(s):  
Film Formation ◽  
Structural Deformation ◽  
Experimental Investigations ◽  
Tribological Behaviour ◽  
Load Bearing ◽  
Numerical Predictions ◽  
Engine Design ◽  
Model Predictions ◽  
Simplifying Assumptions ◽  
Experimental Findings

The paper presents a detailed engine modelling method, referred to as a multi-physics approach, in which combined rigid body inertial dynamics, structural modal characteristics of elastic components and tribological behaviour of load bearing surfaces can be studied within a single analysis. This approach is regarded as holistic and a good aid for detailed design. Of particular interest is the evaluation of behaviour of critical elements in the system, such as the load bearing conjunctions (e.g. crankshaft engine bearings). Another important feature is the inclusion of study of motion across the physics of scale, from micro-scale fluid film formation in bearings to sub-millimetre structural deformation of components and large displacement inertial dynamics. In order to arrive at predictions within sensible industrial time scales, it is essential to include, as far as possible, modelling features of analytical rather than numerical nature, which necessitates inclusion of some simplifying assumptions. When such an undertaking is made, the validity of model predictions must be gauged against experimental findings to enhance confidence in the use of the method. The paper shows good conformance between model predictions and experimental investigations. It further shows that some important issues in engine design and development can be addressed in a satisfactory manner, paving the way for reduction in the empirical or iterative nature of engine design evaluation.

scholarly journals Simultaneous light and small-angle neutron scattering on aggregating concentrated colloidal suspensions

2003 ◽  
Vol 36 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Sara Romer ◽  
Claus Urban ◽  
Vladimir Lobaskin ◽  
Frank Scheffold ◽  
Anna Stradner ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Dynamic Properties ◽  
Sol Gel ◽  
Colloidal Suspensions ◽  
Gel Point ◽  
Local Dynamic ◽  
Colloidal Systems ◽  
High Concentration

A new sample environment has been developed in order to perform light and small-angle neutron scattering (SANS) simultaneously on colloidal systems. The combination of SANS and diffusing wave spectroscopy (DWS) is of particular use in the high-concentration regime. DWS provides information on the local dynamic properties of the individual particles, whereas SANS gives access to the structural properties on similar length scales. The combination of both methods thus allows one to obtain structural and dynamic information over a very large range of length and time scales. Using this new setup, the onset of aggregation and the sol–gel transition in concentrated destabilized polystyrene sphere suspensions have been investigated. At the gel point, a dramatic change of the particle dynamics from diffusion to a subdiffusive arrested motion is observed. However, while the DWS measurements indicate that dramatic changes in the local dynamics occur over a long period, the SANS pattern quickly reaches its final appearance. The SANS experiments thus indicate that a fluid-like structure is arrested in the course of the gel formation. The data are found to be in good qualitative agreement with computer simulations.

Local dynamic properties

2002 ◽  
Vol 82 (2) ◽  
pp. 133-141 ◽  
Author(s):  
J. L. Feldman ◽  
C. S. Hellberg ◽  
G. Viliani ◽  
W. Garber ◽  
F. M. Tangerman
Keyword(s):  
Dynamic Properties ◽  
Local Dynamic

Investigation of Blade and Disc Vibrations on the Upgraded Power Turbine for the THM 1304 Gas Turbine

2004 ◽  
Author(s):  
D. Frank ◽  
A. Kleinefeldt ◽  
U. Orth ◽  
W. Cline
Keyword(s):  
Gas Turbine ◽  
Power Output ◽  
Turbine Blades ◽  
Mode Shapes ◽  
Experimental Investigations ◽  
Numerical Predictions ◽  
Power Turbine ◽  
Temperature Capability ◽  
Blade System ◽  
High Level

As part of an ongoing uprating and upgrading program of the THM 1304 gas turbine directed towards increasing power output and efficiency as well as further improving the high level of availability, major design modifications were made on the power turbine (PT). New blades and vanes were designed for increased aerodynamic efficiency, improved high temperature capability, higher power output and higher nominal operating speed. This report presents the analytical and experimental investigations made on the vibration modes and frequencies of blades with pre-loaded interlocking tip shrouds. One focus is upon observed families of mode shapes at different nodal diameters. A comparison of finite-element results with test data shows how good predictions are in the case of coupled blade vibrations. The value of testing the vibration behavior of power turbine blades in the actual machine, over the complete speed range, becomes evident as an important addition to the numerical predictions and laboratory tests. Another focus is on the method of testing, including the telemetry system used and the problem of optimum placement of strain gages on the blades. The selected strain gage positions are crucial to the value and meaningfulness of the test results. The observed strain vibration amplitudes were compared with high-cycle-fatigue (HCF) data available for the blade material. It was shown that measured amplitudes were significantly below allowable levels over the complete range of operating power and speed. The analytical and experimental methods employed to determine blade mode shapes and frequencies for a blade system with pre-loaded tip shrouds are presented in detail.

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