Transient penetration of a viscoelastic fluid in a narrow capillary channel

2017 ◽  
Vol 830 ◽  
pp. 528-552 ◽  
Author(s):  
Udugama R. Sumanasekara ◽  
Martin N. Azese ◽  
Sukalyan Bhattacharya
Keyword(s):  
Surface Tension Force ◽  
Momentum Conservation ◽  
Weissenberg Number ◽  
Asymptotic Results ◽  
Penetration Length ◽  
Capillary Channel ◽  
Narrow Capillary ◽  
Start Up ◽  
Long Time ◽  
Differential Relations

This article describes an unexplored transport phenomenon where a mildly viscoelastic medium encroaches a narrow capillary channel under the action of surface-tension force. The ultimate goal of the study is to provide the penetration length and the intrusion rate of the liquid as functions of time. The resulting analysis would be instrumental in building an inexpensive and convenient rheometric device which can measure the temporal scale for viscoelastic relaxation from the stored data of the aforementioned quantities. The key step in the formulation is a transient eigenfunction expansion of the instantaneous velocity profile. The time-dependent amplitude of the expansion as well as the intruded length are governed by a system of integro-differential relations which are derived by exploiting the mass and momentum conservation principles. The obtained integro-differential equations are simultaneously solved by using a fourth-order Runge–Kutta method assuming a start-up problem from rest. The resulting numerical solution properly represents the predominantly one-dimensional flow which gradually slows down after an initial acceleration and subsequent oscillation. The computational findings are independently verified by two separate perturbation theories. The first of these is based on a Weissenberg number expansion revealing the departure in the unsteady imbibition due to small but finite viscoelasticity. In contrast, the second one explains the long-time behaviour of the system by analytically predicting the decay features of the dynamics. These asymptotic results unequivocally corroborate the simulation inferring the accuracy of the numerics as well as the utility of the simplified mathematical models.

scholarly journals A strategy to speed up formation and strengthen activity of biofilms at low temperature

RSC Advances ◽  
2017 ◽  
Vol 7 (37) ◽  
pp. 22788-22796 ◽  
Author(s):  
Huizhi Hu ◽  
Junguo He ◽  
Huarong Yu ◽  
Jian Liu ◽  
Jie Zhang
Keyword(s):  
Low Temperature ◽  
Biofilm Reactors ◽  
Start Up ◽  
Long Time ◽  
Speed Up

The start-up period of biofilm reactors often takes a long time to obtain a mature and stable biofilm, especially at low temperature.

scholarly journals Role of technopreneurs in indain context

2019 ◽  
Vol 9 (4) ◽  
pp. 249-252
Author(s):  
ARUNKUMAR B ◽  
GURUNATHAN A
Keyword(s):  
Developed Countries ◽  
Achievement Level ◽  
Indian Government ◽  
Indian Context ◽  
Start Up ◽  
Long Time ◽  
Technology Parks ◽  
Current Scenario ◽  
The Developed Countries

Start-up is a basic thing that a person trying to do something real and new, it has high rates of failure, but the minority of successes includes companies that have evolved as giant and market setters. People who use technology for being entrepreneurs are called as technopreneurs, being born the risk in business in addition to being accomplished the achievement level in innovative and initiative a new kind of product and service to the community. India is enjoying with the fruitful result on the progress of start-up environment which it has been focusing for a long time, the best time for promoting the techno start-up to be apillar of strength in the forthcoming trends. The boom of technopreneurs of our nation had been targeted by the developed countries since 2010. A new benchmark may be set in heavily offering number of opportunities to extent the business, which is also a next level of the start-up environmentin the current scenario and the efforts are taken by the Indian Government. The Technopreneurship's growth and contribution to the start-up technopreneurs in Indian context are catered in this paper and in addition new schemes and well equipped technology parks will be effectuated for the goodness of the new start-up.

scholarly journals Modern Base Load Gas Turbines Running on Crude Oil: Long Time Effects and Experience

1982 ◽  
Author(s):  
B. Basler ◽  
P. C. Felix
Keyword(s):  
Crude Oil ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Diesel Oil ◽  
Time Effects ◽  
Start Up ◽  
Long Time ◽  
Reliability Numbers ◽  
Base Load ◽  
Better Than

Crude oils are favorable gas turbine fuels, particularly in areas where light crudes are available and distillates in sufficient quantities are difficult to obtain. In Riyadh, Saudiarabia, local Khurais crude oil is therefore certainly the most reasonable gas turbine fuel. This paper shows the long time experience with this type of fuel gathered in ten modern BBC type 11 turbines with a total of over 100,000 operating hours. The main problems and the measures taken to overcome these problems are described in detail. The operational record of the Riyadh 5 power plant of the last three years demonstrates that it is possible to run a powerplant without any diesel oil for blending or start up, e.g., and still to obtain availability and reliability numbers which are as good or better than for a diesel or gas fired plant.

scholarly journals Analysis and management of operating risk created by turbine operation under flexible regimes

2019 ◽  
Vol 137 ◽  
pp. 01026 ◽  
Author(s):  
Andrzej Rusin ◽  
Adam Wojaczek ◽  
Martyna Tomala
Keyword(s):  
Power Unit ◽  
Power Plants ◽  
Considerable Increase ◽  
Low Cycle Fatigue ◽  
Diagnostic Testing ◽  
Propagation Rate ◽  
Rotor Steel ◽  
Start Up ◽  
Long Time ◽  
Non Destructive

The new conditions in which coal-fired power plants, especially 200 MW units, have to operate require a considerable increase in the dynamics of their operation. The power unit start-up frequency increases and so does the frequency of changes in loads. This intensifies some wear processes, such as low- cycle fatigue and crack propagation in particular. Therefore, further operation of power units which have already been in service for a long time has to be supplemented with results of analyses and tests taking account of the intensification of wear processes. The paper presents a proposal for an extension of standard diagnostic testing of turbines by adding small punch tests (SPT) of the rotor material micro specimens. The SPT method enables a fast quasi non-destructive assessment of changes in mechanical properties, especially rotor steel embrittlement due to the turbine previous operation. The other element of the proposed testing is the analysis of the propagation rate of potential cracks in the rotor and assessment of the rotor failure probability for different scenarios of the power unit further operation.

scholarly journals Single and multiple solution algorithms to scan asteroid databases for identifications

2006 ◽  
Vol 2 (S236) ◽  
pp. 269-280
Author(s):  
Maria E. Sansaturio ◽  
O. Arratia
Keyword(s):  
Solar System ◽  
Physical Object ◽  
Poor Quality ◽  
Multiple Solution ◽  
Minor Planet ◽  
Solution Algorithms ◽  
Start Up ◽  
Long Time ◽  
Great Advance

AbstractThe process of cataloguing the minor planet population of the Solar System has experienced a great advance in the last decades with the start-up of several surveys. The large volume of data generated by them has increased with time and given rise to huge databases of asteroids with uneven qualities.In fact, a significant fraction of these objects have not been enough observed, thus leading to the computation of very poor quality orbits as to carry out useful predictions of the positions of such asteroids. As a result, some objects can get lost, which is particularly embarrassing for those with Earth crossing orbits.When this situation persists for a long time, the aforementioned databases end up contaminated in the sense that they contain more than one discovery for the same physical object and some kind of action must be taken. The algorithms for asteroid identifications are thought precisely to mitigate this problem and their design will depend upon the quality of the available data for the objects to be identified.In this paper we will distinguish two cases: when both objects have a nominal orbit and when one of them lacks it. In addition, when the available data poorly constrain the solution, other orbits in the neighbourhood of the nominal one are also compatible with the observations. Using these alternative orbits allows us to find many identifications that otherwise would be missed. Finally, we will show the efficiency of all these algorithms when applied to the datasets distributed by the Minor Planet Center.

Mathematic Model of Airliner Forced Landing onto Water in Contacting Stage

2012 ◽  
Vol 170-173 ◽  
pp. 1983-1986
Author(s):  
Shu Ya Wang ◽  
Mong Yu Li ◽  
Chao Liu ◽  
She Sheng Zhang ◽  
Sheng Ping Jin
Keyword(s):  
Peak Pressure ◽  
Mathematic Model ◽  
Impact Angle ◽  
Momentum Conservation ◽  
Forced Landing ◽  
Long Time ◽  
Fluid Coupling ◽  
Water Stage ◽  
The Difference ◽  
Surface Angle

A mathematic model of the optimal posture of airliner landing onto water is built in contacting water stage. By using solid-fluid coupling, momentum conservation, motion equation and pressure drags, the difference equation is constructed to find the influences of the contact water surface angle. The numeric results shows that the peak pressure keeps long time if impact angle small..

scholarly journals On the origin of start-up effects in ply-ply friction for UD fiber-reinforced thermoplastics in melt

2021 ◽  
Author(s):  
Rens Pierik ◽  
Wouter Grouve ◽  
Sebastiaan Wijskamp ◽  
Remko Akkerman
Keyword(s):  
Shear Stress ◽  
Yield Stress ◽  
Nonlinear Viscoelasticity ◽  
Wall Slip ◽  
Simulation Software ◽  
Design Stage ◽  
Fiber Reinforced ◽  
Press Forming ◽  
Start Up ◽  
Long Time

Hot press forming is an attractive production technology to fulfil the increasing demand for complex fiber-reinforced thermoplastic parts. Over the years, process simulation tools on press forming have shown to be very helpful in facilitating the design stage for defect free parts production. One of the important deformation mechanisms considered in process simulations is the relative slip of successive plies or ply-ply friction, of which the underlying principles need to be better understood in order to improve the overall predictive simulation quality. In particular the use of steady-state friction values, neglecting the transient response, is questionable as experiments showed that shear stress overshoots can be as high as three times the long-time value. The phenomenon of the overshoot at start-up shear is analyzed. Possible explanations include nonlinear viscoelasticity and a slip relaxation effect giving rise to wall slip, which are discussed using relevant ply-ply friction measurements carried out on a dedicated friction test set-up. Experimental results on UD C/PEEK show that the shear stress build up and subsequent relaxation comply with nonlinear viscoelasticity. However, the long-time shear stress fails to match the matrix material’s viscosity, possibly due to a yield stress. The flow curve corrected for a yield stress resembles the effects of wall slip. A transient model according to these findings will enhance the accuracy of press forming simulation software.

Some Notes on the Strength of the Enrico Fermi Reactor Vessel Structure

1959 ◽  
Vol 81 (1) ◽  
pp. 66-72
Author(s):  
F. R. Beyer
Keyword(s):  
High Temperature ◽  
Reactor Vessel ◽  
Enrico Fermi ◽  
Strain Gages ◽  
Start Up ◽  
Vessel Structure ◽  
Long Time ◽  
And Function ◽  
Structure Evaluation ◽  
Temperature Strain

The place and function of the reactor vessel in the Enrico Fermi Atomic Power Plant—the most complex nuclear structure built to date—is described. The design basis must lead to a conservative structure. Evaluation of the design of any new and radically different structure must be based upon tests. Strain gaging during hydrostatic testing gave limited results. High-temperature strain gages will be used during simulated-service tests prior to start-up. A successful high temperature strain-gaging technique for long-time static applications up to at least 900 F is developed and described.

scholarly journals Analytical Stability Checks for Diaphragm Wall Trenches and Boreholes Supported by Polymer Solutions

2016 ◽  
Author(s):  
Lesemann Henning ◽  
Vogt Norbert ◽  
Pulsfort Matthias
Keyword(s):  
Polymer Solutions ◽  
Three Dimensional ◽  
Hydraulic Gradient ◽  
Diaphragm Wall ◽  
Hydraulic Support ◽  
Penetration Length ◽  
Foundation Soil ◽  
Analytical Stability ◽  
Long Time ◽  
Temporary Stabilization

Polymer solutions are increasingly used as supporting fluids for the temporary stabilization of diaphragm wall trenches and boreholes. However, analytical stability checks as they are common practice for geotechnical structures like retaining walls or slopes are rarely performed in these cases. Fundamental considerations for such stability checks will be presented here. For trenches and boreholes supported by bentonite suspensions analytical stability checks have proven themselves over a long time. Based on this concept, characteristics of hydraulic support by polymer solutions will be described in detail. The focus will be on the derivation of the time-dependent penetration length of a polymer solution into the surrounding foundation soil and of the hydraulic gradient over this penetration length which correlates with the efficiency of hydraulic support. Findings of other references dealing with three-dimensional failure body geometry, layered soils etc. may be combined with the approach in this paper as the hydraulic gradient around the trench or borehole is always required for such investigations. Unlike trial trenches or boreholes (typical in construction practice) analytical stability checks allow to evaluate relevant parameters for a specific application and to determine a level of safety for a given system. Such calculations should therefore complement trials on site.

scholarly journals Asymptotic limits for a nonlinear integro-differential equation modelling leukocytes’ rolling on arterial walls

Nonlinearity ◽  
2021 ◽  
Vol 35 (2) ◽  
pp. 843-869
Author(s):  
Vuk Milišić ◽  
Christian Schmeiser
Keyword(s):  
Mathematical Framework ◽  
Time Behavior ◽  
Long Time Behavior ◽  
Asymptotic Results ◽  
Differential Model ◽  
Absolute Value ◽  
Arterial Walls ◽  
Equation Modelling ◽  
Convergence Results ◽  
Long Time

Abstract We consider a nonlinear integro-differential model describing z, the position of the cell center on the real line presented in Grec et al (2018 J. Theor. Biol. 452 35–46). We introduce a new ɛ-scaling and we prove rigorously the asymptotics when ɛ goes to zero. We show that this scaling characterizes the long-time behavior of the solutions of our problem in the cinematic regime (i.e. the velocity z ˙ tends to a limit). The convergence results are first given when ψ, the elastic energy associated to linkages, is convex and regular (the second order derivative of ψ is bounded). In the absence of blood flow, when ψ, is quadratic, we compute the final position z ∞ to which we prove that z tends. We then build a rigorous mathematical framework for ψ being convex but only Lipschitz. We extend convergence results with respect to ɛ to the case when ψ′ admits a finite number of jumps. In the last part, we show that in the constant force case [see model 3 in Grec et al (2018 J. Theor. Biol. 452 35–46), i.e. ψ is the absolute value)] we solve explicitly the problem and recover the above asymptotic results.

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