Dissipative structure as the final steady state of an ultralow-expansion glass after prolonged aging

2018 ◽  
Vol 57 (3) ◽  
pp. 031401
Author(s):  
Hiroshi Kobayashi ◽  
Atsuo Morinaga
Keyword(s):  
Steady State ◽  
Dissipative Structure ◽  
Prolonged Aging ◽  
Final Steady State

Transient Thermoelastohydrodynamic Study of Tilting-Pad Journal Bearings Under Dynamic Loading

1998 ◽  
Vol 120 (2) ◽  
pp. 405-409 ◽  
Author(s):  
P. Monmousseau ◽  
M. Fillon ◽  
J. Freˆne
Keyword(s):  
Steady State ◽  
Dynamic Loading ◽  
Dynamic Load ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Maximum Temperature ◽  
Tilting Pad ◽  
Transient Period ◽  
Final Steady State ◽  
Tilting Pad Journal Bearings

Nowadays, tilting-pad journal bearings are submitted to more and more severe operating conditions. The aim of this work is to study the thermal and mechanical behavior of the bearing during the transient period from an initial steady state to a final steady state (periodic). In order to study the behavior of this kind of bearing under dynamic loading (Fdyn) due to a blade loss, a nonlinear analysis, including local thermal effects, realistic boundary conditions, and bearing solid deformations (TEHD analysis) is realized. After a comparison between theoretical results obtained with four models (ISO, ADI, THD, and TEHD) and experimental data under steady-state operating conditions (static load Ws), the evolution of the main characteristics for three different cases of the dynamic load (Fdyn/Ws < 1, Fdyn/Ws = 1 and Fdyn//Ws > 1) is discussed. The influence of the transient period on the minimum film thickness, the maximum pressure, the maximum temperature, and the shaft orbit is presented. The final steady state is obtained a long time after the appearance of a dynamic load.

On the evolution of thermally driven shallow cavity flows

1994 ◽  
Vol 259 ◽  
pp. 107-124 ◽  
Author(s):  
P. G. Daniels ◽  
P. Wang
Keyword(s):  
Steady State ◽  
Numerical Solutions ◽  
Temporal Evolution ◽  
Initial Conditions ◽  
Lateral Wall ◽  
Cavity Flows ◽  
Thermally Driven ◽  
Order Of Magnitude ◽  
Final Steady State ◽  
Shallow Cavity

The temporal evolution of thermally driven flow in a shallow laterally heated cavity is studied for the nonlinear regime where the Rayleigh number R based on cavity height is of the same order of magnitude as the aspect ratio L (length/height). The horizontal surfaces of the cavity are assumed to be thermally insulating. For a certain class of initial conditions the evolution is found to occur over two non-dimensional timescales, of order one and of order L2. Analytical solutions for the motion throughout most of the cavity are found for each of these timescales and numerical solutions are obtained for the nonlinear time-dependent motion in end regions near each lateral wall. This provides a complete picture of the evolution of the steady-state flow in the cavity for cases where instability in the form of multicellular convection does not occur. The final steady state evolves on a dimensional timescale proportional to l2/κ, where l is the length of the cavity, κ is the thermal diffusivity of the fluid and the constant of proportionality depends on the ratio R/L.

Final steady-state pioneer dies

Physics World ◽  
2005 ◽  
Vol 18 (10) ◽  
pp. 9-9
Author(s):  
Matin Durrani
Keyword(s):  
Steady State ◽  
Final Steady State

An Empirical Model for the Prediction of Hemodialysis System Performance

2011 ◽  
Author(s):  
Jane Kang ◽  
Amit Jariwala ◽  
David W. Rosen
Keyword(s):  
Steady State ◽  
Time Constant ◽  
Empirical Model ◽  
Prediction Method ◽  
Fixed Time ◽  
State Behavior ◽  
Steady State Condition ◽  
Inverse Simulation ◽  
Optimal Inputs ◽  
Final Steady State

The examination of steady state behavior of hemodialysis treatment using the analytical model created by Olson et al. revealed that for each set of hemodialysis conditions, a fixed time constant exists that dictates how quickly the patient’s waste level cycle reaches a steady state condition. They also revealed that initial waste level does not affect the final steady state waste level. In this study, an empirical model for the time constant and the final steady state maximum waste level were found that lumps hemodialysis inputs such as flow rates, dialyzer properties, and patient waste generation by conducting a parametric study on a previous hemodialysis model from Olson et al. [1] The empirical model is validated by comparing the curve that predicts how the peak waste level of each cycle changes over time with the analytical model’s results. For all the tested input values which cover most of practical hemodialysis treatments, the curve closely matched the numerical model’s results with R2 value higher than .9973. The empirical model created in this study provides a much simpler prediction method without the use of complex numerical simulations. In addition, the Olson model cannot be used to run an inverse simulation to determine optimal inputs for desired outputs. This limitation is overcome by our empirical model, which further allows much easier and more extended exploration of different therapies (dose length and schedule) for both doctors and renal replacement system designers.

Investigation of Back Pressure Effects on Transient Gas Flow Through Porous Media via Laboratory Experiments and Numerical Simulation

2014 ◽  
Author(s):  
Xiaolei Liu ◽  
Akkharachai Limpasurat ◽  
Gioia Falcone ◽  
Catalin Teodoriu
Keyword(s):  
Steady State ◽  
Gas Flow ◽  
Laboratory Experiments ◽  
Transient Flow ◽  
Pressure Profile ◽  
Back Pressure ◽  
Pressure Effects ◽  
Gas Wells ◽  
Liquid Loading ◽  
Final Steady State

When developing a transient numerical reservoir simulator, it is important to consider the back pressure effects that waves propagating from one end of the porous medium will have on the temporal distribution of pore fluid pressure within the medium itself. Such waves can be triggered by changing boundary conditions at the interface between reservoir and wellbore. An example is given by the transient reservoir response following pressure fluctuations at the wellbore boundary for gas wells suffering from liquid loading. Laboratory experiments were performed using a modified Hassler cell to mimic the effect of varying downhole pressure on gas flow in the near-wellbore region of a reservoir. Gauges were attached along a sandstone core to monitor the pressure profile. The results of the experiments are shown in this paper. A numerical code for modelling transient flow in the near-wellbore region was run to mimic the experiments. The comparisons of simulations and laboratory test results are presented here, for the initial and final steady-state flowing conditions, and where the inlet pressure was maintained constant while initiating a transient pressure build up at the core outlet. The concept of the U-shaped pressure profile along the near-wellbore region of a reservoir under transient flow conditions, originally proposed by Zhang et al. [1], was experimentally and numerically reproduced for single-phase gas flow. This is due to a combination of inertia and compressibility effects, leading to the reservoir response not being instantaneous. The results suggest that, in two phase gas-liquid conditions, liquid re-injection could occur during liquid loading in gas wells. From the experimental results, the U-shaped curves were more obvious and of longer duration in the case of greater outlet pressure. The transition from the initial to the final steady state condition occurred rapidly in all the cases shown here, with the U-shaped pressure profile appearing only over a relatively short time (at the small scale and low pressures tested in this study).

scholarly journals Global Structure of Interstellar Medium and Star Formation Rate

1981 ◽  
Vol 93 ◽  
pp. 73-73
Author(s):  
S. Ikeuchi
Keyword(s):  
Steady State ◽  
Interstellar Medium ◽  
Supernova Remnants ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Neutral Medium ◽  
Shell Formation ◽  
Shock Heating ◽  
Final Steady State ◽  
Warm Ionized Medium

Assuming that the interstellar medium (ISM) is composed of the hot ionized medium (HIM), the warm ionized medium (WIM) and the cold neutral medium (CNM), we examine the interchange processes among them by supernova remnants. These are the evaporation of CNM, the shock heating of WIM and the cold shell formation at the shock front. Calculating the time variation of each component, the timescale and evolutionary characteristics till attaining a steady state are deduced. Generally speaking, the final steady state is classified to two types.

Efficient Steady-State Computation for Wear of Multimaterial Composites

2016 ◽  
Vol 138 (3) ◽  
Author(s):  
Florian Feppon ◽  
Mark A. Sidebottom ◽  
Georgios Michailidis ◽  
Brandon A. Krick ◽  
Natasha Vermaak
Keyword(s):  
Steady State ◽  
Optimization Design ◽  
Iterative Scheme ◽  
Parabolic Partial Differential Equation ◽  
Iterative Schemes ◽  
Foundation Model ◽  
Final Steady State ◽  
Inverse Rule ◽  
And Control ◽  
Two Parameter

Traditionally, iterative schemes have been used to predict evolving material profiles under abrasive wear. In this work, more efficient continuous formulations are presented for predicting the wear of tribological systems. Following previous work, the formulation is based on a two parameter elastic Pasternak foundation model. It is considered as a simplified framework to analyze the wear of multimaterial surfaces. It is shown that the evolving wear profile is also the solution of a parabolic partial differential equation (PDE). The wearing profile is proven to converge to a steady-state that propagates with constant wear rate. A relationship between this velocity and the inverse rule of mixtures or harmonic mean for composites is derived. For cases where only the final steady-state profile is of interest, it is shown that the steady-state profile can be accurately and directly determined by solving a simple elliptic differential system—thus avoiding iterative schemes altogether. Stability analysis is performed to identify conditions under which an iterative scheme can provide accurate predictions and several comparisons between iterative and the proposed formulation are made. Prospects of the new continuous wear formulation and steady-state characterization are discussed for advanced optimization, design, manufacturing, and control applications.

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