scholarly journals A time domain approach for the exponential stability of a linearized compressible flow‐structure PDE system

2020 ◽  
Vol 44 (2) ◽  
pp. 1326-1342
Author(s):  
Pelin Guven Geredeli
Keyword(s):  
Exponential Stability ◽  
Compressible Flow ◽  
Flow Structure ◽  
Time Domain

scholarly journals Time-domain boundedness of noise-to-state exponentially stable systems

2020 ◽  
Vol 26 ◽  
pp. 105
Author(s):  
Zhou Fang ◽  
Chuanhou Gao
Keyword(s):  
Lower Bound ◽  
Exponential Stability ◽  
Time Domain ◽  
Domain Of Attraction ◽  
Stable System ◽  
Stochastic Noise ◽  
Exponentially Stable ◽  
Probability Domain ◽  
The Time Domain ◽  
Insight Into

In this paper we prove the time-domain boundedness for noise-to-state exponentially stable systems, and further make an estimation of its lower bound function, which allows to answer the question that how long the solution of a stochastic noise-to-state exponentially stable system stays in the domain of attraction and what happens with it if it escapes from this region for a while. The results will complement the probability-domain boundedness of noise-to-state exponentially stable systems, and provide a new insight into noise-to-state exponential stability.

scholarly journals Identifiability of Location and Magnitude of Flow Barriers in Slightly Compressible Flow

SPE Journal ◽  
2016 ◽  
Vol 21 (03) ◽  
pp. 0899-0908 ◽  
Author(s):  
S.. Kahrobaei ◽  
M.. Mansoori Habibabadi ◽  
G. J. Joosten ◽  
P. M. Van den Hof ◽  
J. D. Jansen
Keyword(s):  
Transfer Function ◽  
Compressible Flow ◽  
Time Domain ◽  
Production Data ◽  
Permeability Barrier ◽  
Low Permeability ◽  
Noise Levels ◽  
Large Reservoir ◽  
Slightly Compressible ◽  
Free Data

Summary Classic identifiability analysis of flow barriers in incompressible single-phase flow reveals that it is not possible to identify the location and permeability of low-permeability barriers from production data (wellbore pressures and rates), and that only averaged reservoir properties in between wells can be identified. We extend the classic analysis by including compressibility effects. We use two approaches: a twin experiment with synthetic production data for use with a time-domain parameter-estimation technique, and a transfer-function formalism in the form of bilaterally coupled four-ports allowing for an analysis in the frequency domain. We investigate the identifiability, from noisy production data, of the location and the magnitude of a low-permeability barrier to slightly compressible flow in a 1D configuration. We use an unregularized adjoint-based optimization scheme for the numerical time-domain estimation, by use of various levels of sensor noise, and confirm the results by use of the semianalytical transfer-function approach. Both the numerical and semianalytical results show that it is possible to identify the location and the magnitude of the permeability in the barrier from noise-free data. By introducing increasingly higher noise levels, the identifiability gradually deteriorates, but the location of the barrier remains identifiable for much-higher noise levels than the permeability. The shape of the objective-function surface, in normalized variables, indeed indicates a much-higher sensitivity of the well data to the location of the barrier than to its magnitude. These theoretical results appear to support the empirical finding that unregularized gradient-based history matching in large reservoir models, which is well-known to be a severely ill-posed problem, occasionally leads to useful results in the form of model-parameter updates with unrealistic magnitudes but indicating the correct location of model deficiencies.

A time-domain evaluation of the large-scale flow structure in a turbulent jet

1979 ◽  
Vol 367 (1729) ◽  
pp. 193-218 ◽  
Keyword(s):  
Flow Structure ◽  
Time Domain ◽  
Large Scale ◽  
Reynolds Numbers ◽  
Turbulent Jet ◽  
Flow Structures ◽  
Jet Flows ◽  
Hot Wire ◽  
Potential Core ◽  
Large Scale Flow

This paper describes an investigation of the large-scale flow processes which occur in turbulent circular jet flows ( Re > 10 5 ). The existence of regular large-scale flow structures at low and moderate Reynolds numbers ( Re < 5 x 10 4 ) has clearly been demonstrated by flow-visualization experi­ments, but visual evidence for order in jet turbulence becomes ambiguous at a Reynolds number around 7 x 10 4 . A new time-domain technique for the study of two-dimensional large-scale flow structures has been developed by Bruun (1977). In this paper this technique is extended to the study of three-dimensional large-scale flow structures by the inclusion of X hot-wire and circumferential eductions. The evaluated large-scale structures in the turbulent jet ( Re = 2 x 10 5 ) are shown to deviate considerably from the axi-symmetric flow structures which occurs at low and moderate Reynolds numbers ( Re < 5 x 10 4 ). We observe a much smaller deformation rate of the semi-regular flow structure in the potential core in the turbulent jet case, and also the circumferential eductions reveal a rapid radial decrease in the circumferential coherence of the related large-scale flow structure in the mixing region. Further-­more, combining these results with the X hot-wire eductions in the mixing region proved that the major contributions to the shear stress uv is caused by circumferentially-narrow tongues of ‘fast moving ejected’ and ‘slow moving entrained ’fluid, similar to the ‘burst’ and ‘sweep’ events observed previously in turbulent wall boundary layers.

Study of turbulent compressible flow structure in a CO2 laser cylindrical discharge tube

1993 ◽  
Author(s):  
O. Boiron ◽  
G. Vlad ◽  
Philippe Caminat ◽  
Philippe Bournot ◽  
G. Le Palec
Keyword(s):  
Compressible Flow ◽  
Flow Structure ◽  
Co2 Laser ◽  
Discharge Tube

A time-domain analysis of the large-scale flow structure in a circular jet. Part 1. Moderate Reynolds number

1977 ◽  
Vol 83 (4) ◽  
pp. 641-671 ◽  
Author(s):  
H. H. Bruun
Keyword(s):  
Reynolds Number ◽  
Flow Structure ◽  
Time Domain ◽  
Large Scale ◽  
Time Domain Analysis ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Moderate Reynolds Number ◽  
Temporal And Spatial ◽  
Large Scale Flow

This paper presents a new experimental time-domain technique for the evaluation of the large-scale structure in a turbulent flow. The technique is demonstrated by hot-wire anemometry for a circular jet flow at a moderate Reynolds number of 104, and the large-scale structure identified is compared successfully with smoke flow-visualization observations. The temporal and spatial relationships of the separate large-scale flow events have been derived, and this information enabled the evaluation of the nonlinear spatial development of the large-scale flow structure.

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