Low frequency evaluation of steady‐state pressure distribution and reverberation time in two‐room coupled system

2008 ◽  
Vol 123 (5) ◽  
pp. 3911-3911
Author(s):  
Miroslaw Meissner
Keyword(s):  
Steady State ◽  
Pressure Distribution ◽  
Low Frequency ◽  
Coupled System ◽  
Reverberation Time ◽  
State Pressure

Computational studies of steady-state sound field and reverberant sound decay in a system of two coupled rooms

Open Physics ◽  
2007 ◽  
Vol 5 (3) ◽  
Author(s):  
Mirosław Meissner
Keyword(s):  
Steady State ◽  
Sound Pressure ◽  
Low Frequency ◽  
Sound Field ◽  
Coupled System ◽  
Reverberation Time ◽  
Acoustic Characteristics ◽  
Acoustical Properties ◽  
Forced Oscillator ◽  
Calculation Results

AbstractThe acoustical properties of an irregularly shaped room consisting of two connected rectangular subrooms were studied. An eigenmode method supported by a numerical implementation has been used to predict acoustic characteristics of the coupled system, such as the distribution of the sound pressure in steady-state and the reverberation time. In the theoretical model a low-frequency limit was considered. In this case the eigenmodes are lightly damped, thusthey were approximated by normal acoustic modes of a hard-walled room. The eigenfunctions and eigenfrequencies were computed numerically via application of a forced oscillator method with a finite difference algorithm. The influence of coupling between subrooms on acoustic parameters of the enclosure was demonstrated in numerical simulations where different distributions of absorbing materials on the walls of the subrooms and various positions of the sound source were assumed. Calculation results have shown that for large differences in the absorption coefficient in the subrooms the effect of modal localization contributes to peaks of RMS pressure in steady-state and a large increase in the reverberation time.

scholarly journals Measurement of Steady State Pressure Distribution and Dynamic Pressure Fluctuations During Sputtering Process

2017 ◽  
Vol 60 (6) ◽  
pp. 220-227
Author(s):  
Shuichi TAJIRI ◽  
Takanori ONISHI ◽  
Yukiko OKANO ◽  
Soichi OGAWA ◽  
Hiroshi MIMA
Keyword(s):  
Steady State ◽  
Pressure Distribution ◽  
Dynamic Pressure ◽  
Pressure Fluctuations ◽  
State Pressure

Dynamic Modeling of Air Cushion Vehicles

2007 ◽  
Author(s):  
M. Pollack ◽  
B. Connell ◽  
J. Wilson ◽  
W. Milewski
Keyword(s):  
Free Surface ◽  
Pressure Distribution ◽  
Dynamic Pressure ◽  
Strong Dependence ◽  
Low Frequency ◽  
Coupled System ◽  
Lumped Parameter Model ◽  
Mode Shapes ◽  
Resonant Frequencies ◽  
Air Cushion

The motion of an Air Cushion Vehicle (ACV) is a complex process involving the nonlinear dynamics of the ship, free surface waves, air cushion cavity, skirt, and air flow hydraulics (e.g. orifice behavior of the bag feed holes). The overall system is tightly coupled, with the loading of the ship dependent on the pressure field within the cavity, and the dynamics of the cavity dependent on the motion of the ship, free surface, and skirt. Principle excitation to the system is through the free surface motion and the fan flow. The large dimensions of the system introduce low frequency acoustic and mechanical resonances, which lead to complex and coupled system dynamics. The focus of this paper is on analytical modeling of an ACV and its physics to enable verification of a numerical model which is under development. The initial focus is on the dynamics of the air cushion cavity, with emphasis on its resonant frequencies and mode shapes. The mode shapes are important because they define the nature of the dynamic pressure distribution acting on the ship, and associated heave, pitch, and roll excitation. The strong dependence of the cavity resonant characteristics on the impedance of the skirt, which bounds the cavity, is first demonstrated by assessing limiting cases of a high impedance skirt (e.g. massive or rigid) and of a low impedance skirt (e.g. light or soft). The changes in resonant frequency and dynamic pressure distribution associated with the changes in skirt impedance are illustrated. Because the actual skirt impedance will lie between these two idealized cases, we also develop a lumped parameter model of the skirt dynamics. Initial parametric studies with this model, which investigate variations in the skirt mass, further demonstrate the strong dependence of the resonant frequencies and pressure distributions on the skirt impedance.

Asymptotic Analysis of a Finite Gas Slider Bearing of Narrow Geometry

1983 ◽  
Vol 105 (3) ◽  
pp. 491-495 ◽  
Author(s):  
J. J. Shepherd ◽  
R. C. DiPrima
Keyword(s):  
Steady State ◽  
Asymptotic Analysis ◽  
Pressure Distribution ◽  
Asymptotic Expansions ◽  
Matched Asymptotic Expansions ◽  
Slider Bearing ◽  
Load Bearing ◽  
Bearing Number ◽  
Isothermal Gas ◽  
State Pressure

The method of matched asymptotic expansions is used to analyze the steady state pressure distribution and load bearing properties of a finite rectangular isothermal gas slider bearing when ε, the ratio of transverse to longitudinal dimensions of the bearing, is small and the bearing number Λ is moderate. General expressions for the pressure and load are obtained. Specific results are given for bearings with shallow crowning. The effects of the bearing number becoming large and the interaction between the two effects ε→0 and Λ→∞ are discussed.

Experimental Periodic Localized Motions in Coupled Beams With Active Nonlinearities

1995 ◽  
Author(s):  
Melvin E. King ◽  
Johannes Aubrecht ◽  
Alexander F. Vakakis
Keyword(s):  
Steady State ◽  
Vibrational Energy ◽  
Normal Modes ◽  
Coupled System ◽  
Nonlinear Normal Modes ◽  
Nonlinear Frequency ◽  
Nonlinear Phenomenon ◽  
Response Curves ◽  
Nonlinear Motion ◽  
Spatially Extended

Abstract Steady-state nonlinear motion confinement is experimentally studied in a system of weakly coupled cantilever beams with active stiffness nonlinearities. Quasi-static swept-sine tests are performed by periodically forcing one of the beams at frequencies close to the first two closely-spaced modes of the coupled system, and experimental nonlinear frequency response curves for certain nonlinearity levels are generated. Of particular interest is the detection of strongly localized steady-state motions, wherein vibrational energy becomes spatially confined mainly to the directly excited beam. Such motions exist in neighborhoods of strongly localized anti-phase nonlinear normal modes (NNMs) which bifurcate from a spatially extended NNMs of the system. Steady-state nonlinear motion confinement is an essentially nonlinear phenomenon with no counterpart in linear theory, and can be implemented in vibration and shock isolation designs of mechanical systems.

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