Effect Of Flow Reversal Research Articles

The intracranial effects of flow reversal during transcarotid artery revascularization.

This study aimed to assess intraoperative cerebral hemodynamic responses and embolic events during transcarotid artery revascularization via transcranial Doppler, near-infrared spectroscopy, and bispectral index monitoring. Twelve patients (7 males, 5 females; mean age: 72.8±9.0 years; range, 63 to 91 years) undergoing transcarotid artery revascularization with simultaneous transcranial Doppler, near-infrared spectroscopy, and bispectral index monitoring were analyzed in this retrospective study between September 2017 and December 2019. The mean flow velocity and pulsatility index of the middle cerebral artery, alongside near-infrared spectroscopy and bispectral index values, before flow reversal, during flow reversal, and after flow reversal phases were investigated. The presence and frequency of high-intensity transient signals were recorded to evaluate embolic incidents. Significant reductions in middle cerebral artery mean flow velocity were noted during flow reversal (40.58±10.57 cm/sec to 20.58±14.34 cm/sec, p=0.0004), which subsequently returned to and exceeded baseline values after flow reversal cessation (53.33±17.69 cm/sec, p=0.0005). Near-infrared spectroscopy (71±4.4% to 66±6.2%) and bispectral index (45.71±8.5 to 40.14±8.1) values mirrored these hemodynamic changes, with notable decreases during flow reversal, and recoveries after flow reversal. The highest concentration of high-intensity transient signals was observed during stent deployment, signifying a critical embolic phase. No perioperative neurological complications or other significant adverse events were documented. Transcranial Doppler, near-infrared spectroscopy, and bispectral index effectively monitor cerebral hemodynamics and embolic potential during transcarotid artery revascularization, providing real-time data crucial for optimizing perioperative management. These findings underscore the clinical value of multimodal monitoring in improving patient outcomes in transcarotid artery revascularization procedures.

A Model of Mass and Heat Transfer for Disc Temperature Prediction in Open Compressor Cavities

Abstract Accurate prediction of heat transfer in compressor cavities is crucial to the design of efficient and reliable aircraft engines. The heat transfer affects the thermal expansion of the compressor rotor and, in turn, the tip clearance of the compressor blades. This article presents a novel, physically based predictive theoretical model of heat transfer and flow structure in an open compressor cavity, which can be used to accurately calculate disc temperatures. The radially higher region of the cavity is dominated by buoyancy effects created by the temperature difference between the hot mainstream flow and the axial throughflow used to cool the turbine. Strong interaction between the air in the cavity and this throughflow creates a mixing region at low radius. For a given geometry, the heat transfer and flow physics are governed by four parameters: the rotational Reynolds number Reϕ, the buoyancy parameter βΔT, the compressibility parameter χ, and the Rossby number Ro. The model quantifies both the buoyancy- and throughflow-induced mass and heat transfer, producing a reliable prediction of the disc and air temperatures. The model takes into account a twofold effect of the throughflow: being entrained into the cold radial plumes directly and creating a toroidal vortex in the radially lower region of the cavity. The exchange of mass between the cavity and throughflow is related to the mass flowrate in the radial plumes in the buoyancy-induced region, considering the effect of flow reversal at low Ro. The model is validated using data collected in the Bath compressor cavity rig and can be incorporated in engine design codes to robustly compute the thermal stress and expansion of the compressor rotor, contributing to more efficient engine designs.

A computational conjugate heat transfer study of a rectangular minichannel undergoing sinusoidal flow pulsations

The development of current and next generation high performance electronic devices has led to smaller components in more densely packed spaces. The increasing power levels have resulted in ever-increasing heat flux densities which necessitates the evolution of new liquid-based heat exchange technologies. Pulsating flow in single-phase cooling systems is viewed as a potential solution to the problems involving high heat flux densities. A review of published literature indicates a lack of time-resolved and space-resolved links between the hydrodynamic pulsating characteristics and associated heat transfer perturbations. The scope of this work involves the development of a validated three-dimensional conjugate heat transfer computational model to investigate hydrodynamically and thermally fully developed pulsating flows in a heated rectangular minichannel. Simulations were performed for a sinusoidal waveform with a fixed pulsation amplitude for varying pulsation frequencies in the range of 0.02 Hz to 25 Hz, corresponding to Womersley numbers in the range of 0.5 ≤Wo≤ 18.33. Low pulsation frequencies exhibited the well known parabolic profile for the fluctuating hydrodynamic and thermal parameters, i.e., velocity, wall shear, and wall temperature. As a result, the axial pressure gradient, velocity, and wall shear stress profiles were in phase and similar results were obtained for the oscillating wall and bulk fluid temperatures. For the inertia dominated high frequency flows, an increase in axial pressure gradient leads to a phase lag of π/2 when compared with the velocity and wall shear profiles. The shorter time period pulsations exhibit unique attributes in the form of flow reversal effects at local near wall regions. High near wall thermal gradients were observed as a result of stronger viscous effects due to a narrowing thermal boundary layer; consequently the transverse diffusion of heat was ineffective. A phase lag and a subsequent drop in the peak magnitudes existed between the oscillating bulk and wall temperatures for high frequency flows. Fluctuations in near wall heat flux profiles showed a dependency on the imposed pulsation frequencies. For the chosen pulsation profile and frequencies, the overall time averaged thermal performance indicates that pulsating flow performs worse than steady flow for a flow rate amplitude of 1. The highest thermal performance was achieved for Wo=5.1 while maintaining a low friction factor.

Counter-flow phenomena studied by nuclear magnetic resonance (NMR) velocimetry and flow simulations

Flow patterns including counter-flow and flow reversal effects have been studied by a combination of nuclear magnetic resonance flow imaging and numerical modeling using the finite volume method in the open-source computational fluid mechanics package OpenFOAM. Two cylindrical geometries have been used: In a concentric double-cylinder system the flow reversal under oscillatory rotation of the inner cylinder has been followed, and the time evolution of the flow reversal has been studied. We find extended periods of counter-rotating flow in the gap where fluid in the inner part of the gap follows the new direction of the rotor, while the outer part takes a longer time until the viscous forces transmit the reverted flow direction outwards. The radial position of the reversal of flow direction has been monitored as a function of the oscillation angle after the turning point. In the second cylindrical geometry, the rotating bob is placed off the center and a counter-rotating vortex is detected in the wider part of the gap. At constant viscosity and eccentricity, the position of the center of the vortex was found to depend on the rotation frequency of the bob. Qualitative and quantitative agreement between experiment and laminar (nonturbulent) flow simulations has been obtained for both steady-state flow using the Semi-Implicit Method for Pressure Linked Equations (SIMPLE) algorithm and time-dependent flow using the Pressure Implicit with Splitting of Operators (PISO) algorithm.

On the effect of flow reversal during crossflow microfiltration of a cell and protein mixture

Alternating tangential flow (ATF) filtration is a cell retention technique of increasing importance in continuous biomanufacturing. Despite its frequent application, the role of flow reversal in fouling mitigation remains unclear this far. We implemented a customized pilot plant comprising a low-shear centrifugal pump and fast switching valves, which enables us to create alternating crossflow, where crossflow velocities and cycle times can be varied independently, as well as conventional steady forward and pulsatile forward crossflow. We then used a model feed containing yeast cells and bovine serum albumin (BSA) in order to simulate a fermentation broth and investigated the impact of alternating crossflow on microfiltration performance at this customized filtration plant. By comparing the results with filtration trials conducted at forward only pulsatile crossflow as well as steady crossflow using the same plant, we observed the true effect of flow reversal, corrected for effects induced by crossflow velocity, transmembrane pressure as well as transmembrane pressure fluctuations. We found that alternating crossflow, i.e. crossflow with flow reversal, leads to a reduced fouling resistance and a higher solute transmission in comparison to steady crossflow filtration. However, the flux increase is lower than for pulsatile crossflow filtration, which might be attributed to length dependency effects. The transmission of BSA, on the other side, is even higher at alternating crossflow filtration than for pulsatile crossflow. Thus, we conclude that flow reversal plays a part in fouling mitigation, but a greater part of the anti-fouling effect of alternating crossflow, however, is caused by the transmembrane pressure fluctuations.

Never Change a Flowing System? The Effects of Retrograde Flow on Isolated Perfused Lungs and Vessels.

Retrograde perfusion may occur during disease, surgery or extracorporeal circulation. While it is clear that endothelial cells sense and respond to changes in blood flow, the consequences of retrograde perfusion are only poorly defined. Similar to shear stress or disturbed flow, retrograde perfusion might result in vasomotor responses, edema formation or inflammation in and around vessels. In this study we investigated in rats the effects of retrograde perfusion in isolated systemic vessels (IPV) and in pulmonary vessels of isolated perfused lungs (IPL). Anterograde and retrograde perfusion was performed for 480 min in IPV and for 180 min in the IPL. Perfusion pressure, cytokine levels in perfusate and bronchoalveolar lavage fluid (BALF), edema formation and mRNA expression were studied. In IPV, an increased perfusion pressure and initially also increased cytokine levels were observed during retrograde perfusion. In the IPL, increased edema formation occurred, while cytokine levels were not increased, though dilution of cytokines in BALF due to pulmonary edema cannot be excluded. In conclusion, effects of flow reversal were visible immediately after initiation of retrograde perfusion. Pulmonary edema formation was the only effect of the 3 h retrograde perfusion. Therefore, further research should focus on identification of possible long-term complications of flow reversal.

Fully Developed Opposing Mixed Convection Flow in the Inclined Channel Filled with a Hybrid Nanofluid.

This paper studies the convective heat transfer of a hybrid nanofluid in the inclined channel, whose walls are both heated by the uniform heat flux. The governing ordinary differential equations are made nondimensional and solved analytically, in which explicit distributions of velocity, temperature and pressure are obtained. The effects of flow reversal, wall skin friction and Nusselt number with the hybrid nanofluid depend on the nanoparticle volume fractions and pressure parameters. The obtained results indicate that the nanoparticle volume fractions play a key role in delaying the occurrence of the flow reversal. The hybrid nanofluids hold more delayed range than conventional nanofluids, which is about 2.5 times that of nanofluids. The calculations have been compared with the base fluid, nanofluid and two kinds of hybrid models (type II and type III). The hybrid model of type III is useful and simplified in that it omits the nonlinear terms due to the interaction of different nanoparticle volumetric fractions, with the relative error less than 3%. More results are discussed in the results section below.

Piecewise linear model predictive control of a rapid pressure swing adsorption system

AbstractRapid pressure swing adsorption (RPSA) is a gas separation technology used in the small‐scale oxygen concentrator devices. These devices are commonly used to produce high purity (~90%) oxygen from air for oxygen rehabilitation therapy, but can also produce a much wider range of oxygen purities for other applications. RPSA is a complex, cyclic, nonlinear switched logic process resulting from the coupling of gas adsorption, heat transfer, flow reversal effects, and process logic switches. For RPSA devices to operate satisfactorily, feedback control is critical but challenging due to their inherent complexity. In this article, we present a piecewise linear model predictive control framework for operation and control of a single‐bed RPSA system. A set of coupled, nonlinear partial differential equations with flow switching conditions is used as a plant model for the RPSA process. Subspace system identification with pseudo‐random binary sequence signals applied to this plant model at multiple operating points is used to generate a family of piecewise linear models for use in the model predictive controller algorithm. Detailed descriptions of the RPSA plant model, the multiple linear model identification procedure, the controller formulation and model switching logic are presented. The closed‐loop system is evaluated in simulation using several realistic set point tracking and disturbance rejection cases.

Reverse flow reactor with side feeding as a novel strategy to create dynamic oxygen coverage and heat propagations in lean ammonia oxidation

The simulation of dynamic reverse flow operation (RFO) with reactor side feeding for selectivity issue during exothermic reaction, while incorporating mass and energy balances both solid phase and gas phase, is presented in this paper with particular aim to investigate the product distribution. The reactor model consisted of mass balances on the level of elementary steps, which led to detailed dynamic influence of flow reversal effect on kinetics. The results showed the production rate of the desired product can be kept at high level, which may exceed the level of regular RFO and even of steady state operation (SSO). Even for the quasi-steady state regime, the reverse flow reactor with side feeding shows a different product distribution in comparison to SSO. The influence of shifting the feed positions to the reactor center is most pronounced. The reverse flow operation with reactor side feeding is a prime key for improved conversion and manipulation of product distribution.

Molecular and Continuum Transport Perspectives on Electroosmotic Slip Flows

Velocity slip in electroosmotic flows (EOF) is investigated using an analytical solution of Poisson–Boltzmann and Stokes (PB-S) equations with slip correction, and the results are compared with the predictions from molecular dynamics (MD) simulations. Particularly, EOFs of NaCl solution in silicon nanochannels are simulated, and channel dimensions are picked to exhibit plug flow behavior in the bulk region. Electrochemical conditions are specified within the validity region of PB theory to avoid charge inversion and flow reversal effects. The analytical model shows normalization of the slip length (an interfacial property) with the Debye length determined by the ionic concentration, implying that the slip enhancement in EOFs is independent of the channel height. MD results are compared with the analytical solution using the apparent viscosity and slip lengths determined by force-driven flow simulations in charged silicon nanochannels. Onset of slip velocity within the electrical double layer and its effec...

A radiofrequency heated reactor system for post-combustion carbon capture

Several problems with stabilization of electricity grid system are related to the time lag between the electricity supply and demand of the end users. Many power plants run for a limited period of time to compensate for increased electricity demand during peak hours. The amount of CO2 generated by these power installations can be substantially reduced via the development of new demand side management strategies utilizing CO2 absorption units with a short start-up time. The sorbent can be discharged using radiofrequency (RF) heating to fill the night-time valley in electricity demand helping in the stabilization of electricity grid. Herein a concept of RF heated fixed bed reactor has been demonstrated to remove CO2 from a flue gas using a CaCO3 sorbent. A very stable and reproducible operation has been observed over twenty absorption-desorption cycles. The application of RF heating significantly reduced the transition time required for temperature excursions between the absorption and desorption cycles. The effect of flow reversal during desorption on desorption time has been investigated. The desorption time was reduced by 1.5 times in the revered flow mode and the total duration of a single absorption-desorption cycle was reduced by 20%. A reactor model describing the reduced desorption time has been developed.

Gas flow analysis for the impact of gob gas ventholes on coalbed methane drainage from a longwall gob

A large amount of methane releasing from the residual coal and the surrounding pressure-relieved gas-bearing strata may accumulate in the longwall gob of gas-bearing coal seam, which is increasingly exploited as a major source of coalbed methane (CBM) development in coal mining areas. Meanwhile, if the gob methane emits into the working space along with air-leakage flow, they may impair the safety and productivity of underground coal mines. Thus, gob gas drainage is of great significance to both the CBM development and the control of gob gas emission. Currently, there exist two major technologies for gob gas drainage–gob gas ventholes (GGVs) drainage and underground drainage (such as high-level suction tunnels, high-located boreholes and buried pipes in the upper-corner). In practical engineering applications, the GGVs have greater advantage over the traditional underground drainage in the extraction flux of gob gas and the control of gob gas emission, but the theoretical mechanism of GGVs has not yet been revealed in previous studies. Consequently, the characteristics of gob gas flow with GGVs drainage needs further research.In this paper, the numerical simulation of gas flow in gob gas reservoirs and the in-situ assessment of GGVs drainage are carried out to investigate the mechanism of the control of gob gas flow with GGVs drainage. Firstly, based on fluid mechanics in porous media the mathematical model of gob gas transport is developed. Then, the gas pressure distribution, gas flow patterns and methane concentration distribution in the gob under the conditions of no drainage measures, drainage with buried pipe in the upper-corner and GGVs in different locations are discussed by conducting numerical simulation, respectively. In addition, the influence of distance between GGV and return airway on the gob methane flow and the strong control scope of GGVs are analyzed in detail. It is found that: 1) GGVs has the “flow-interception effect” on the gas in the deep zone of the gob and the “flow-reversal effect” on the gas in the gob close to the longwall face, which accounts for that GGVs drainage advantage over underground drainage. 2) GGVs can be applied to drain the gas in the deep zone of the gob massively and to control the gob gas migration effectively, so they are a top choice for the extraction of gob gas and the control of gob gas emission. Finally, both GGVs drainage and underground drainage are adopted to extract gob gas in east-102 working face in Weijiadi coal mine. The comparison of the extracted and emitted volume of gob gas with two different technologies shows that, GGV can drain the gob gas with greater flux and can better control the gob gas emission, which validated the prediction of numerical stimulation.

Flow reversal effects on buoyancy induced air flow in a solar chimney

This paper reports a numerical investigation of flow reversal effects on the buoyancy induced air flow in a solar chimney for ventilation applications over a range of controlling parameters. The reverse flow phenomenon is quantitatively examined by calculating its penetration depth. In order to suppress the reverse flow and enhance ventilation performance, a configuration with an inclined passive wall is proposed as a new design; the effectiveness of this design has been examined over the Rayleigh number range of 109⩽Ra⩽1011. It is identified that there exists an optimum inclination angle corresponding to an optimum aspect ratio at which the mass flow rate is the maximum for a given Rayleigh number. The numerical results are supported by a scaling argument and a flow visualization experiment.

Flow Reversal and Mixing

Summary Flow-reversal studies provide insights into mixing mechanisms in flow through porous media. In these studies, the direction of flow is reversed after the solute slug has penetrated into the medium (but not exited) to a predetermined distance. We simulated the effect of flow reversal on mixing in 2D porous media using two different approaches. In the first approach, we perform direct numerical simulation of a solute-slug transport (by solving Navier-Stokes and convection/diffusion equations) in a surrogate pore space. This approach allows a direct visualization of mixing in simple flow geometries. The effect of flow reversal on mixing is investigated for several diffusion coefficients, penetration depths, and flow geometries. The second approach uses particle tracking to simulate the effect of flow reversal at larger length scales. This approach is free of numerical dispersion, can be used in the absence of diffusion, and has no limits on the size of the simulation. It is, however, limited to layered-media flow. The simulation studies presented in this paper explain the mechanism of mixing and the origin of the irreversibility of dispersion in flow through porous media. We also explain several experimental observations on flow-reversal tests found in the literature. Mixing in porous media takes place because of interaction between convective spreading and molecular diffusion. The con-verging/diverging paths and flow around impervious sand grains cause the solute front to stretch and split. In this process, the area of contact between the solute slug and the resident fluid increases by an order of magnitude and diffusion becomes an effective mixing mechanism. This local mixing, caused by diffusion, is irreversible. For purely convective transport, solute particles retrace their path back to the inlet upon flow reversal. Convective spreading gets canceled, and echo dispersion is 0. Diffusion, even though small in magnitude, is responsible for local mixing and making dispersion in porous media irreversible. Thus, it is important to include the effect of diffusion when analyzing miscible displacements in porous media.

Simulation of the flow-reversal effect in dual-channel CICC for ITER

The discovery of an upward counter flow of helium in the outer annulus of the vertically oriented and top-to-bottom cooled ITER PF-FSJS (Poloidal Field Coil-Full Size Joint Sample) in 2002 led to closer investigations of the effect because it may lead to a reduction of the operational margin of the superconductor used in the ITER environment. Recently, further thermo-hydraulic experiments were carried out on the TFAS2 sample (Toroidal Field Advanced Strand sample 2) with the intent to asses the effect in detail. First investigations confirmed the initial assumption that the origin of the effect lies in the buoyancy of the heated, and thus less dense, helium in the outer annulus of the cable. The helium there is in good contact with the superconducting strands heated by neutron irradiation, ac losses or heat influx, but is thermally and hydraulically less well coupled to the downward flowing helium in the central channel. This paper presents an analysis of the TFAS2 experiments using the simulation program THEA™, specifically extended with a term for gravitational forces acting on helium of varying density. With the experience gained, the simulation of the thermo-hydraulic behavior of the Toroidal Field Coil inner leg shows the operational limits and boundary conditions of this coil in ITER.

Modelling climate change impacts in the Peace and Athabasca Catchment and delta: II—variations in flow and water levels with varying winter severity

AbstractAs freshwater ice is known to significantly affect flows and water levels within the Peace–Athabasca Delta (PAD), a winter severity sensitivity analysis using a one‐dimensional open channel hydraulic model was performed for four climate scenarios (from mild to severe), and was examined under three differing flow conditions (low, average, and high hydraulic regimes), in an effort to better understand the multiple interactions between ice cover and the hydrodynamic regime of this complex system characterized by overbank flooding and flow reversal episodes. In general, a reduction of winter severity lowered lake levels and river flows. While the winter severity effect is of relatively short duration in the rivers, the subsequent reduction in lake levels extends over the summer months. High river flows predispose flow reversal conditions, and water enters the lakes at the outlet as the water levels in the rivers feeding the PAD increase significantly over a short period of time. This flow reversal effect is suppressed during milder winters. Numerical modelling results indicate that extending the ice‐cover season (severe winter) by 14 days resulted in an increase of up to 5 cm in water level of large lakes in the PAD, while reducing it by 28 days lowered the levels by almost 10 cm. Short‐term variations in river levels reached up to 1·5 m as a result of varying the extent of the ice‐cover season. As the simulation runs did not consider ice‐jam events and neglected the effect of ice thickness on water levels, the reported quantitative results must be interpreted with prudence. Copyright © 2006 Crown in the right of Canada, and John Wiley & Sons, Ltd.

Time-dependent, three-dimensional flow and mass transport during solution growth of potassium titanyl phosphate

A finite-element, numerical model is used to compute time-dependent, three-dimensional fluid flow, mass transfer, and continuum growth kinetics in the potassium titanyl phosphate (KTP) solution crystal growth system of Bordui et al. The effects of a periodically-reversing crystal rotation schedule are analyzed for two different crystal-mounting geometries. Results suggest a lower probability of the occurrence of defects when the mounting geometry is designed to take advantage of periodic flow reversal effects on the supersaturation field.

Modeling physiological resistance in bacterial biofilms

A mathematical model of the action of antimicrobial agents on bacterial biofilms is presented. The model includes the fluid dynamics in and around the biofilm, advective and diffusive transport of two chemical constituents and the mechanism of physiological resistance. Although the mathematical model applies in three dimensions, we present two-dimensional simulations for arbitrary biofilm domains and various dosing strategies. The model allows the prediction of the spatial evolution of bacterial population and chemical constituents as well as different dosing strategies based on the fluid motion. We find that the interaction between the nutrient and the antimicrobial agent can reproduce survival curves which are comparable to other model predictions as well as experimental results. The model predicts that exposing the biofilm to low concentration doses of antimicrobial agent for longer time is more effective than short time dosing with high antimicrobial agent concentration. The effects of flow reversal and the roughness of the fluid/biofilm are also investigated. We find that reversing the flow increases the effectiveness of dosing. In addition, we show that overall survival decreases with increasing surface roughness.

Nitric oxide is significantly reduced in ex vivo porcine arteries during reverse flow because of increased superoxide production

Oscillatory and negative flows occur normally in the cardiovascular system, which predispose those regions to atherosclerosis. Nitric oxide (NO) production increases in proportion to the magnitude of flow and is known to be athero-protective. What is not known, however, is the effect of flow reversal on NO concentration ([NO]). The hypothesis of the present study is that [NO] is reduced in reverse flow. An additional hypothesis is that the reduction in [NO] is mediated through an increase in superoxide production during flow reversal. These hypotheses were tested in an ex vivo preparation of porcine elastic and muscular arteries. The flow of a physiological solution through the vessels was regulated in the forward and reverse direction and the effluent was assayed for nitrite levels using a combination of a diazo coupling method and high performance liquid chromatography. Our results show that [NO] is significantly reduced during reverse flow. Furthermore, addition of tempol (superoxide dismutase-mimetic) which is a superoxide scavenger returns the [NO] during reverse flow to mirror those of forward flow. These results have important implications since the action of superoxide is implicated in many cardiovascular diseases, and the present finding suggests that flow reversal should be added to the list.

Effect of Flow Reversal on the Shear Induced Formation of Multilamellar Vesicles

The influence of rate controlled flow reversal on the transition from planar lamellae to multilamellar vesicles (MLV) using a nonionic lamellar phase consisting of 40 wt % triethylene glycol monodecyl ether (C10E3 in D2O) is investigated by means of time-resolved rheo-small-angle light and neutron scattering (SALS, SANS). Flow reversal provides the possibility to control the kinetics of the transition substantially, and states occurring very early during the transition can be studied. A slowing down of the transition on an absolute strain axis is observed as the strain amplitude of the flow reversal is decreased. This retardation is attributed to the partial recovery of an earlier state as shear is inverted. This can nicely be demonstrated by the width of the azimuthal intensity distribution, which shows oscillations upon flow reversal. From the slowing down of the process a loss term is defined, which provides insight in the very early stages of the experiment, namely the minimum strain that is needed to induce irreversible structural changes in the sample. This quantity is for the present sample found to be 6.5 strain units. Furthermore, the exponential scaling of the strain needed to reach characteristic states of the transition with strain amplitude seems to hold for all length scales involved in the process.