Natural Vibration of a Cavity Backed Rectangular Plate Using A Receptor-Rejector System Model

1995 ◽  
Vol 117 (4) ◽  
pp. 416-423 ◽  
Author(s):  
C. Rajalingham ◽  
R. B. Bhat ◽  
G. D. Xistris
Keyword(s):  
Rectangular Plate ◽  
Natural Vibration ◽  
Coupled System ◽  
System Model ◽  
Total System ◽  
Modal Interactions ◽  
Principle Of Superposition ◽  
Noise Transmission ◽  
Modes Of Vibration ◽  
Flexible Wall

Forced vibration of a cavity backed rectangular plate is widely used to study the physics of noise transmission into an enclosure. In this context, the cavity backed plate is a dynamical system with coupled motion of the plate and the air cavity. The natural frequencies of the coupled system are the most important characteristics of the noise transmission into the cavity. This paper investigates the natural vibration of a cavity backed rectangular plate and presents numerical results for the particular case of a cavity backed simply supported plate. The natural vibration of the total system is viewed as the result of the interactions of various natural modes of vibration of its subsystems. The physics of the modal interactions is discussed using a receptor-rejector system model, and the dynamics of the cavity backed panel is investigated using the plate receptance and the cavity rejectance (inverse receptance) parameters. The modal interactions are further clarified using a cavity backed piston forming a single degree of freedom system. With the principle of superposition, the receptor-rejector system model can be used to analyze cavities with more than one flexible wall.

The effect of structural-acoustic coupling on the sound field in a trapezoidal enclosure

2019 ◽  
Vol 67 (3) ◽  
pp. 180-189
Author(s):  
Yuan Wang ◽  
Jianrun Zhang ◽  
Lan Chen ◽  
Naifei Ren ◽  
Lei Li ◽  
...  
Keyword(s):  
Sound Field ◽  
Coupled System ◽  
System Model ◽  
Rectangular Enclosure ◽  
Coupling System ◽  
Modal Density ◽  
Resonance Frequencies ◽  
Decay Times ◽  
Flexible Wall ◽  
Trapezoidal Enclosure

The sound field characteristics in a trapezoidal enclosure surrounded by a flexible wall, which is adjacent to the tilted one, are investigated and compared with the case of a rectangular enclosure. The acoustic modes of trapezoidal enclosure are obtained by the coupling of the modes of rectangular enclosure that bounds it. The coupling system model is then built between trapezoidal enclosure modes and flexible wall modes using modal coupling theory. Based on the coupled system model, the effect of flexible wall modal density on the resonance frequencies and the decay times of coupled system are analyzed. Compared with the case of rectangular enclosure, the variation of the resonance frequency and the decay time of enclosure-controlled system mode is determined by its mode indices and tilted wall location when the panel modal density is changed. When the modal indices of trapezoidal sound field in the two directions unparallel to the tilted wall are equal to zero simultaneously, the effect of inclination angle on the resonance frequencies and decay times of these coupled system modes can be neglected. Otherwise, the coupling system modes behaviors are changed with the elevation angle. In addition, the coupling selection between the modes of trapezoidal enclosure and flexible wall is discussed in detail.

scholarly journals Description and evaluation of NorESM1-F: A fast version of the Norwegian Earth System Model (NorESM)

2018 ◽  
Author(s):  
Chuncheng Guo ◽  
Mats Bentsen ◽  
Ingo Bethke ◽  
Mehmet Ilicak ◽  
Jerry Tjiputra ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Sea Ice ◽  
Large Scale ◽  
Coupled Model ◽  
Coupled System ◽  
Internal Variability ◽  
Earth System Model ◽  
Meridional Overturning Circulation ◽  
System Model ◽  
Earth System

Abstract. A new computationally efficient version of the Norwegian Earth System Model (NorESM) is presented. This new version (here termed NorESM1-F) runs about 2.5 times faster (e.g. 90 model years per day on current hardware) than the version that contributed to the fifth phase of the Coupled Model Intercomparison project (CMIP5), i.e., NorESM1-M, and is therefore particularly suitable for multi-millennial paleoclimate and carbon cycle simulations or large ensemble simulations. The speedup is primarily a result of using a prescribed atmosphere aerosol chemistry and a tripolar ocean-sea ice horizontal grid configuration that allows an increase of the ocean-sea ice component time steps. Ocean biogeochemistry can be activated for fully coupled and semi-coupled carbon cycle applications. This paper describes the model and evaluates its performance using observations and NorESM1-M as benchmarks. The evaluation emphasises model stability, important large-scale features in the ocean and sea ice components, internal variability in the coupled system, and climate sensitivity. Simulation results from NorESM1-F in general agree well with observational estimates, and show evident improvements over NorESM1-M, for example, in the strength of the meridional overturning circulation and sea ice simulation, both important metrics in simulating past and future climates. Whereas NorESM1-M showed a slight global cool bias in the upper oceans, NorESM1-F exhibits a global warm bias. In general, however, NorESM1-F has more similarities than dissimilarities compared to NorESM1-M, and some biases and deficiencies known in NorESM1-M remain.

scholarly journals Description and evaluation of NorESM1-F: a fast version of the Norwegian Earth System Model (NorESM)

2019 ◽  
Vol 12 (1) ◽  
pp. 343-362 ◽  
Author(s):  
Chuncheng Guo ◽  
Mats Bentsen ◽  
Ingo Bethke ◽  
Mehmet Ilicak ◽  
Jerry Tjiputra ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Sea Ice ◽  
Large Scale ◽  
Coupled Model ◽  
Coupled System ◽  
Internal Variability ◽  
Earth System Model ◽  
Meridional Overturning Circulation ◽  
System Model ◽  
Earth System

Abstract. A new computationally efficient version of the Norwegian Earth System Model (NorESM) is presented. This new version (here termed NorESM1-F) runs about 2.5 times faster (e.g., 90 model years per day on current hardware) than the version that contributed to the fifth phase of the Coupled Model Intercomparison project (CMIP5), i.e., NorESM1-M, and is therefore particularly suitable for multimillennial paleoclimate and carbon cycle simulations or large ensemble simulations. The speed-up is primarily a result of using a prescribed atmosphere aerosol chemistry and a tripolar ocean–sea ice horizontal grid configuration that allows an increase of the ocean–sea ice component time steps. Ocean biogeochemistry can be activated for fully coupled and semi-coupled carbon cycle applications. This paper describes the model and evaluates its performance using observations and NorESM1-M as benchmarks. The evaluation emphasizes model stability, important large-scale features in the ocean and sea ice components, internal variability in the coupled system, and climate sensitivity. Simulation results from NorESM1-F in general agree well with observational estimates and show evident improvements over NorESM1-M, for example, in the strength of the meridional overturning circulation and sea ice simulation, both important metrics in simulating past and future climates. Whereas NorESM1-M showed a slight global cool bias in the upper oceans, NorESM1-F exhibits a global warm bias. In general, however, NorESM1-F has more similarities than dissimilarities compared to NorESM1-M, and some biases and deficiencies known in NorESM1-M remain.

ELECTROSTATIC INTERACTIONS FOR PARTICLE ARRAYS IN ELECTRORHEOLOGICAL FLUIDS I: CALCULATIONS

1994 ◽  
Vol 08 (20n21) ◽  
pp. 2877-2894 ◽  
Author(s):  
YUNG-HUI SHIH ◽  
A. F. SPRECHER ◽  
H. CONRAD
Keyword(s):  
Electrostatic Interactions ◽  
Polarization Vector ◽  
Maximum Force ◽  
Total System ◽  
Hexagonal Array ◽  
Single Chain ◽  
Principle Of Superposition ◽  
Rectangular Array ◽  
Chain System ◽  
Static Conditions

A simple effective charge method and the principle of superposition were used to calculate the total system interaction energy of two-dimensional rectangular and hexagonal arrays of particles in electrorheological suspensions. The calculations gave for static conditions (no shear) that a close-packed hexagonal array of particles was energetically favored over a rectangular array and that for very dilute suspensions a structure consisting of separated single chains was favored over one consisting of clusters. For shearing and assuming that no rotation of the polarization vector takes place, no difference in the maximum force per chain occurred for a two-chain system compared to a single-chain system in either the rectangular or close-packed hexagonal array. This was also the case with rotation of the polarization vector in the rectangular array, although the force was less with rotation compared to without rotation for this array. However, in the case of the dose-packed hexagonal array with rotation of the polarization vector there occurred an order of magnitude enhancement of the maximum force for the two-chain system compared to the single-chain system. This enhancement is comparable to the ratio of the measured strength of ER fluids to that predicted for the structure consisting of separated single chains.

Stochastic Earthquake Analysis of Underwater Storage Tanks

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
H. Karadeniz
Keyword(s):  
Finite Element ◽  
Water Pressure ◽  
Water Structure ◽  
Coupled System ◽  
Earthquake Loading ◽  
Storage Tanks ◽  
Analysis Method ◽  
Eulerian Formulation ◽  
Analysis Technique ◽  
Flexible Wall

In this paper, the problem and analysis method of underwater storage tanks resting on a horizontal seabed is presented under stochastic earthquake loading. The tank is axisymmetrical and has a flexible wall/roof. The finite element method is used for the response solution. A solid axisymmetrical finite element has been formulated to idealize the tank whereas an axisymmetrical fluid element is used for the idealization of the fluid domain. The Eulerian formulation of the fluid system is used to calculate the interactive water pressure acting on the tank during the free motion of the tank and earthquake motion. For the response calculation, the modal analysis technique is used with a special algorithm to obtain natural frequencies of the water-structure coupled system. For the stochastic description of the earthquake loading, the modified Kanai–Tajimi earthquake spectrum is used. Finally, the analysis method presented in the paper is demonstrated by an example.

scholarly journals Vibro-acoustic analysis of a trapezoidal cavity with a clamped flexible wall

2018 ◽  
Vol 37 (4) ◽  
pp. 801-815 ◽  
Author(s):  
Yuan Wang ◽  
Jianrun Zhang ◽  
Xinzhou Zhang ◽  
Bo Wu
Keyword(s):  
Acoustic Analysis ◽  
Coupled Model ◽  
Coupled System ◽  
Coupling Theory ◽  
Incident Plane ◽  
Resonance Frequencies ◽  
Modal Coupling ◽  
Cavity Coupling ◽  
Flexible Wall ◽  
Matching Degree

The coupled model between trapezoidal cavity and its clamped flexible wall is developed using classical modal coupling theory. Based on the coupled model, the resonance frequencies of coupled system are obtained and compared with the corresponding uncoupled one. Meanwhile, the reason for the variation of resonance frequencies of coupled system modes is analyzed in detail. Then, the response of coupled system is investigated using the acoustic potential energy in the cavity and panel vibration kinetic energy when it is excited by an incident plane wave outside of the cavity. Coupling coefficient between trapezoidal cavity and its clamped flexible wall is proposed to assess the modal matching degree between them. It is shown that the coupling selection is not satisfied except in the axis direction which is parallel to the inclined wall. In addition, a rectangular cavity with a clamped flexible wall is also considered and compared with that of the trapezoidal one.

Sea-state dependency of air-sea fluxes for high winds in ECMWF Earth System Model

2020 ◽  
Author(s):  
Jean Bidlot
Keyword(s):  
Drag Coefficient ◽  
Tropical Cyclones ◽  
Coupled System ◽  
Wave Model ◽  
Earth System Model ◽  
System Model ◽  
Earth System ◽  
Sea State ◽  
Medium Range ◽  
Fully Coupled

<p>The global analyses and medium range forecasts from the European Centre for Medium range Weather Forecasts rely on a state-of-the-art Numerical Weather Prediction (NWP) system. To best represent the air-sea exchanges, it is tightly coupled to an ocean wave model.  As part of ECMWF approach to Earth System Model, it is also coupled to a global ocean model for all its forecasting systems from the medium range up to the seasonal time scale.</p><p>Because the feedback from and to the ocean can be significant, it is only in the fully coupled system that parameterisation for air-sea processes should be revisited. For instance, it is now accepted that the drag coefficient should generally attained maximum values for storm winds but should level or even decrease for very strong winds, namely in tropical cyclones or intense mid-latitude wind storms.</p><p>A modification of the wind input source was tested, whereby the Charnock coefficient estimated by the wave model and therefore the drag coefficient sharply reduce for large winds (> 30 m/s). As a consequence, ECMWF tendency to under predict strong tropical cyclones was sharply alleviated, in better agreement with observational evidence. This change is now planned for operational implementation with the next model cycle (CY47R1, June 2020).</p><p>Experimental evidences also point to a sea state/wind dependency of the heat and moisture fluxes.  Following an extension of the wind wave generation theory, a sea state dependent parameterisation for the roughness length scales for heat and humidity has been tested. Again, a proper assessment of the different parameterisations warrants the fully coupled system. Experimentations so far indicate the benefit of such change. Ongoing work aims at future operational implementation.</p>

Coupling Effect of Flexible Geared Rotor on Quick Return Mechanism

2005 ◽  
Author(s):  
J. R. Chang ◽  
W. C. Hsu
Keyword(s):  
Integration Method ◽  
Coupling Effect ◽  
Three Dimensional ◽  
Coupled System ◽  
System Model ◽  
Parameter Study ◽  
Dynamic Behaviors ◽  
Gear Mesh ◽  
Bearing Stiffness ◽  
Stiffness And Damping

Regarding the quick return mechanism, some researchers have neglected the rotor-mechanism coupling effect, and other researchers have combined the quick return mechanism with the motor but only considered the rotational motion of the rotor by assuming the rotor to be rigid and neglected the gear mesh dynamics. In the study, the rotor-mechanism coupling effect is investigated to find that the dynamic behaviors of the coupled system are different from those uncoupled systems. The coupling effect is mainly due to the flexibility of the shaft, the bearing, and the gear mesh. When the quick return mechanism is driven with the flexible geared rotor, the vibrations of the geared rotor have significant influences on the dynamic behaviors of the quick return mechanism. The traditional studies formulated the quick return mechanism only under the consideration of planar motion. However, the three dimensional vibration has to be considered for establishing the physical model of the coupled system. The main objective of this study is focused on the investigation of the coupling effect of the geared rotor on the quick return mechanism. The system model is formulated by using finite element method and following Hamiltonian approach. The numerical integration method is applied to obtain the dynamic response. The coupling effect of the geared rotor on the quick return mechanism is discussed by the parameter study. It is shown that the bearing stiffness and damping and the shaft radius have significant influences on the dynamic behavior of the mechanism.

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