Transient Shear Stress Research Articles

Single cavitation bubble dynamics in a stagnation flow

Jetting of collapsing bubbles is a key aspect in cavitation-driven fluid–solid interactions as it shapes the bubble dynamics and additionally due to its direct interaction with the wall. We study experimentally and numerically the near-wall collapse and jetting of a single bubble seeded into the stagnation flow of a wall jet, i.e. a jet that impinges perpendicular onto a solid wall. High-speed imaging shows rich and rather distinct bubble dynamics for different wall jet flow velocities and bubble-to-wall stand-off distances. The simulations use a volume-of-fluid method that allows us to numerically determine the microscopic and transient pressures and shear stresses on the wall. It is shown that a wall jet at moderate flow velocities of a few metres per second already shapes the bubble ellipsoidally inducing a planar and convergent jet flow. The distinct bubble dynamics allow us to tailor the wall interaction. In particular, the shear stresses can be increased by orders of magnitude without increasing impact pressures the same way. Interestingly, at small seeding stand-offs, the bubble during the final collapse stage can lift off the wall and migrate against the flow direction of the wall jet such that the violent collapse occurs away from the wall.

Evaluating the impact of transient shear stress on platelet activation, adhesion, and aggregation with microfluidic chip technique.

When nonphysiological stenosis occurs, the transient high shear stress formed in vessels increases the risk of thrombosis and is a potential factor for cardiovascular diseases. But the platelet adhesion and aggregation behavior at nonphysiological post-stenosis and its affecting factors are not fully understood yet. In this experiment, platelet aggregation on collagen and fibrinogen at different shear stresses and different hematocrits were observed by microfluidic technology. Platelet activation (P-selectin, glycoprotein IIb/IIIa) and monocyte-platelet aggregate (MPA) levels under different shear stresses were analyzed by flow cytometry. On fibrinogen, platelets aggregate more at higher shear stress conditions. While on collagen, it becomes more difficult for platelets to form stable aggregation at higher shear stress conditions. If platelets adhere initially at low shear stress, stable platelet aggregation can be formed at subsequent high shear stress. Moreover, when the shear stress increases, platelet activity markers (P-selectin, glycoprotein IIb/IIIa and MPAs) increase significantly. Hematocrit affects the degree of platelet aggregation, and the influence of hematocrit is obvious at high shear stress. Transient high shear stress (46 ms) can effectively activate platelets. Platelet aggregation behavior was different for coated fibrinogen and collagen protein. Stable platelet adhesion at post-stenosis is more dependent on fibrinogen and platelet aggregation is stable on both fibrinogen and collagen. Hematocrit can significantly affect the formation of platelet aggregation.

Enhanced anti-fouling of forward osmosis membrane by pulsatile flow operation in textile wastewater treatment

Although osmotically driven membrane processes have exhibited great potential in a variety of applications, forward osmosis (FO) is still facing some critical challenges like membrane fouling, economics and design of draw solute. Current methods include pretreatment and membrane modification have proposed to solve fouling problem, however, these methods are still constrained by complex operational procedures and large use of chemicals. Herein, pulsatile flow, a simply-operated and chemical-free method, was employed to alleviate FO membrane fouling. Effects of pulse frequencies on membrane performance were investigated. Results showed that pulsation could effectively improve water flux and mitigate fouling. In particular, water flux of 5 Hz was 1.36 times higher than steady flow at 0 Hz, and no obvious fouling covered on membrane surface under 5 Hz. Computational Fluid Dynamics (CFD) simulation showed that the flow field on the membrane surface was evenly distributed by pulse, and cross-flow velocity changed regularly from 0.123 to 0.057 m/s in feed channel. Mechanism analysis illustrated effective transient shear stress, pulse induced membrane swing and reduced solute buildup were responsible to improve membrane flux and reduce membrane fouling. This work provides a reference for the further combination and application of pulsatile flow assisted FO to treat wastewater.

Energy dissipation in a rapid filling vertical pipe with trapped air

An energy-dissipation model is developed to simulate rapid filling having an entrapped air pocket within a vertical pipe. Both convective heat transfer and transient wall shear stresses are considered. The resulting predictions are compared both to those obtained via a conventional empirical polytropic model and to experimental data. The comprehensive model accurately reproduces the experimental pressure oscillations. Results reveal that the dynamic behaviour of air pockets in all tested cases approaches a purely adiabatic process over the first two oscillations, but also that the pressure variation then gradually evolves to an isothermal variation. Moreover, the high air temperatures predicted in the numerical simulations account for the observed phenomenon of white mist in the pipe as well as the notably hot pipe wall. Significantly, the conventional empirical polytropic model associated with the adiabatic assumption for the gas phase was sufficient to reproduce the pressures and temperatures during the first two oscillations.

Dynamic quantitative visualization of transient shear stresses in solids

To aid in shear strength analysis, a technique combined with a time-resolved imaging scheme to achieve direct dynamic quantitative visualization of the distribution and evolution of transient shear stresses in solids through one measurement is studied. By modulating the polarization state of the elliptically polarized light transmitted or reflected from the sample, this method requires only one measurement to achieve visualization. Mathematical models of the correlation between the variation of modulated light field and the shear stresses in the plane perpendicular to the optical axis are established based on the theory of mechanics and photoelasticity. The maximum shear stresses of any section are further derived. As an example, the distribution and evolution of shear stresses induced by an ultrasonic field have been quantitatively visualized by the technique. The visualization results are in fairly good agreement with the finite element simulation results. The simplicity and efficiency of this technique are embodied in the fact that one single measurement can directly obtain the distribution of shear stresses in solids, and the measurements of dynamic shear stresses can be conveniently realized through continuous monitoring.

Transient waves in a piezomagnetic half-space subjected to dynamic anti-plane loading

Propagation of transient waves in a piezomagnetic half-space, which is subjected to dynamic anti-plane-concentrated line force, is analyzed theoretically in this study. By employing Laplace transformation and Cagniard de-Hoop method, explicit closed forms of solution for the transverse displacement, shear stress, magnetic potential, and induction are obtained, and contribution from the mechanical and magnetic waves is thus expressed in the transient full-field solution. Propagation of the transient waves in the piezomagnetic half-space is then discussed in detail using numerical calculation. The results show that the magneto-mechanical coupling coefficient and location of the receiver have a significant influence on the transient response of this half-space. The magnitude of the transient shear stress is effectively reduced by the weakening magneto-mechanical coupling coefficient and the arrival time of the transient magnetic induction peak increases with decreasing magneto-mechanical coupling coefficient. In addition, it is found that the smaller the magneto-mechanical coupling coefficient, the higher the static value of the transient magnetic induction.

Computational analysis of the transient mixed convective flow of nanofluid in the plume regions

Computer microchips and many other electrical devices that use microfluidics use nanofluids as coolants. Nanofluids have a higher thermal conductivity due to the volumetric proportion of nanoparticles. Thus, as the nanofluids in engineering and industrial process have a significant role, the current study aims to focus on the transient mixed convective flow of nanofluid in the plume regions. The numerical solutions for the transient mixed convection flow in the form of amplitude and phase angle are performed reasonably. The desired nonlinear mathematical model is created by incorporating periodic behavior into conservation equations and appropriate boundary conditions. Using appropriate scaling variables, the dimensioned equations are transformed into dimensionless ones. Solutions for the values of Prandtl number Pr, Schmidt number Sc, thermophoretic parameter Nt, Brownian motion parameter Nb and mixed convection parameters and show that the coupling between the fluid and heat transfer can have dramatic effects on the transient shear stress heat and mass transfer. The buoyancy force acting on the heated boundary layer of nanofluid can also have a significant impact on transient skin friction, heat and mass transfer. The governing process is accelerating or depending upon the position of the sphere.

3D CFD simulation and analysis of transient flow in a water pipeline

Abstract A three-dimensional (3D) computational fluid dynamics (CFD) approach is developed to elaborate the water-hammer pipe flow and 3D detailed dynamic characteristics of a closing ball valve. The proposed CFD approach considers the water compressibility and the viscous sublayer, which are sometimes neglected in previous studies. Comparisons of the CFD results, the measured pressures and the one-dimensional results, demonstrate that the current 3D CFD approach better reproduces the experimental pressure oscillations while helping to visualize the associated physical processes and to further explore the 3D transient characteristics. The mean velocity distributions in the radial direction significantly change as the pipe transient progresses, which is closely associated with transient shear stress. Mean velocity variations at the valve during the closing process undergo three distinct stages: slight change, then drastic reduction, and finally slowing down. Head loss coefficient and discharge coefficient of the valve change as the valve closing time shortens.

Numerical investigation elucidating effects of microstructure on the transient thermomechanical phenomena during laser impact welding

Transient thermomechanical phenomena such as extreme plastic strains and temperature spikes that occur during laser impact welding are impractical to experimentally observe given the sub-microsecond duration of the joining process. Thus, computational models are necessary to study in-situ behavior along the weld interface. While researchers have utilized computational models for such investigations, this work elucidates the specific influence of microstructure-level modeling that captures the associated inhomogeneity/anisotropic effects at smaller scales. An aluminum 1100-H19 flyer and a stainless steel 304-O target foil are modeled using an Eulerian framework to simulate cases with and without microstructure consideration during laser impact welding of dissimilar metallic foils. When considering microstructure modeling, variations in flow stress reveal intermittently elevated temperatures along the weld interface due to concentrations of shock pressure at relatively small grains; however, they are not found to be a significant source of instability initiating or influencing the joint formation. Grain refinement and material hardening are suggested within a 10 μm-thick zone of the flyer near the weld interface, while severe plastic deformation in the target indicates possible martensitic phase transformation. Grain boundary sliding driven by variations in yield surfaces among individual grains gives rise to relatively higher collision velocity. Consequently, higher plastic strain rates along with greater amounts of plastic heat dissipation at the interface result in increased material jetting at higher temperatures. Alternating transient shear stresses are predicted in each model, though the inhomogeneous model predicts the brief appearance of a concentrated shear zone in the rebound region which is not seen in the homogeneous model. This work illuminates correlations between microstructure and transient phenomena during laser impact welding of dissimilar metallic foils, thus demonstrating a numerical modeling approach extensible to numerous other impact welding processes that complete within a very short time span.

Stokes’ second problem and oscillatory Couette flow for a two-layer fluid: Analytical solutions

The unsteady motion of a two-layer fluid induced by oscillatory motion of a flat plate along its length is mathematically analyzed. Two cases are considered: (i) the two-layer fluid is bounded only by the oscillating plate (Stokes’ second problem), and (ii) the two-layer fluid is confined between two parallel plates, one of which oscillates while the other is held stationary (oscillatory Couette flow). In each of the Stokes and Couette cases, both cosine and sine oscillations of the plate are considered. It is assumed that the fluids are immiscible, and that the flat interface between the fluids remains flat for all times. Solutions to the initial-boundary value problems are obtained using the Laplace transform method.The results obtained for the velocity fields for the flows are new and complete. Steady periodic and transient velocity fields are explicitly presented. Transient and steady-state shear stresses at the boundaries of the flows are calculated; the existing literature lacks any such results. The results derived in this paper retrieve previously known results for corresponding single-layer flows. Furthermore, the results obtained are illustrated taking particular example of each of the Stokes’ problem and the Couette flow. With the help of the illustrations, some physical insights into the flows of the particular problems are gained. Again, the results obtained could also be applicable to a problem of heat conduction in a composite solid with sinusoidal temperature variation on the surface.

Rheological analysis of bio-ink for 3D bio-printing processes

3D bio-printing is an emerging technology to fabricate tissue scaffold in-vitro through the controlled allocation of biomaterial and cells, which can mimic the in-vivo counterpart of living tissue. Live cells are often encapsulated into the biomaterials (i.e., bio-ink) and extruded by controlling the printing parameters. The functionality of the bioink depends upon three factors: (a) printability, (b) shape fidelity, and (c) bio-compatibility. Increasing viscosity will improve the printability and the shape fidelity but require higher applied extrusion pressure, which is detrimental to the living cell dwelling in the bio-ink, which is often ignored in the bio-ink optimization process. This paper demonstrates a roadmap to develop and optimize bio-inks, ensuring printability, shape fidelity, and cell survivability. The pressure exerted on the bio-ink during extrusion processes is measured analytically, and the information is incorporated in the bio-ink's rheology design. Cell-laden filaments are fabricated with multiple cell lines, i.e., Human Embryonic Kidney (HEK 293), BxPC3, and prostate cancer cells which are analyzed for cell viability. The cross-sectional live-dead assay of the extruded filament demonstrates a spatial pattern for HEK 293 cell viability, which correlates with our analytical finding of the shear stress at the nozzle tip. All three cell lines were able to sustain a transient shear stress of 3.7 kPa and demonstrate 90% viability with our designed bio-ink after 15 days of incubation. Simultaneously, the shape fidelity and printability matrices show its suitability for 3D bio-printing process.

Investigating the mechanotransduction of transient shear stress mediated by Piezo1 ion channel using a 3D printed dynamic gravity pump.

Microfluidic systems are widely used for studying the mechanotransduction of flow-induced shear stress in mechanosensitive cells. However, these studies are generally performed under constant flow rates, mainly, due to the deficiency of existing pumps for generating transient flows. To address this limitation, we have developed a unique dynamic gravity pump to generate transient flows in microfluidics. The pump utilises a motorised 3D-printed cam-lever mechanism to change the inlet pressure of the system in repeated cycles. 3D printing technology facilitates the rapid and low-cost prototyping of the pump. Customised transient flow patterns can be generated by modulating the profile, size, and rotational speed of the cam, location of the hinge along the lever, and the height of the syringe. Using this unique dynamic gravity pump, we investigated the mechanotransduction of shear stress in HEK293 cells stably expressing Piezo1 mechanosensitive ion channel under transient flows. The controllable, simple, low-cost, compact, and modular design of the pump makes it suitable for studying the mechanobiology of shear sensitive cells under transient flows.

A New Protocol for Controlling and Targeting Reactive Hyperemia Shear Stress to Assess Endothelial Function

Conduit artery endothelial function is most commonly assessed via measurement of flow mediated dilation (FMD) evoked by a transient post-limb occlusion increase in shear stress [reactive hyperemia (RH)]. A limitation of RH-FMD is the uncontrolled nature of the RH shear stress stimulus which produces RH-FMD response variability that is independent of conduit artery endothelial function. The purpose of this study was to develop a protocol to create a uniform, targeted, and transient (40 second) shear stress stimulus and compare it to the standard RH-FMD approach. We hypothesize that incorporating arterial compression in the controlled targeted RH (CTRH) protocol will allow us to achieve a uniform target shear rate (estimate of shear stress) within and between participants. Young, healthy men and women (females n = 4, age = 22 ± 1 years; males n = 2, age = 25 ± 3 years) underwent one trial of RH-FMD and two trials of CTRH-FMD with duplex ultrasound assessment. The CTRH protocol incorporated three-minutes of ischemic handgrip exercise at 30% of participants’ maximum voluntary contraction during a five-minute occlusion to create a large forearm vasodilation and hyperemic reserve. Upon cuff release, the ensuing hyperemia was controlled with manual brachial artery compression at the antecubital fossa. A live velocity readout permitted compression adjustments to achieve the velocity required to maintain a target shear rate of 120 s-1. The cuff was re-inflated after 40s of cuff release. The RH-FMD trial followed the standard five-minute forearm occlusion protocol. The 40s average shear rate was 116.0 ± 8.8s-1 in the CTRH test and 102.1 ± 15.4 s-1 in the RH test. The CTRH test shear rate was significantly closer to the 120s-1 target; calculated as the absolute distance from target in 3s time bins over the 40s period: CTRH = 19.0 ± 3.9s-1; RH = 36.5 ± 6.7 s-1 p = 0.002. The between participant coefficient of variation (CV) for the RH 40s average shear rate was lower in the CTRH test (CTRH CV = 8.1%; RH CV = 15.1%). The within subject trial to trial CV for the CTRH 40s average shear rate was 3.0 ± 4.6%. FMD responses were similar between tests (CTRH-FMD% = 8.3 ± 1.6%; RH-FMD% = 7.6 ± 4.8%, p=0.717). These preliminary findings demonstrate the capacity for RH stimulus control. CTRH-FMD is minimally impacted by stimulus variability and may provide a clearer reflection of brachial artery endothelial function.

Deformation and cyclic resistance of sand in large-strain undrained torsional shear tests with initial static shear stress

This paper presents the findings from an experimental study focusing on the undrained cyclic behavior of sand in the presence of initial static shear stress. A series of undrained cyclic torsional shear tests was performed on saturated air-pluviated Toyoura sand specimens up to single amplitude shear strain (γSA) exceeding 50%. Two types of cyclic loading conditions, namely, stress reversal (SR) and stress non-reversal (SNR), were employed by changing the amplitude of the combined initial static shear and cyclic shear stresses. The tests covered a broad range of initial states in terms of relative density (Dr = 20–74%) and the initial static shear stress ratio (α = 0–0.30). The following five distinct modes of deformation were identified from the tests based on the density state, the transient undrained peak shear stress, and the combined cyclic and static shear stresses: 1) static liquefaction, 2) cyclic liquefaction, 3) cyclic mobility, 4) shear deformation failure, and 5) limited deformation. Of these, cyclic liquefaction and static liquefaction are the most critical. They occur in very loose sand (Dr ≤ 24%) under SR and SNR, respectively, and are characterized by abrupt flow-type shear deformation. Cyclic mobility occurs under SR in loose to dense sand with Dr ≥ 24%. Contrarily, shear deformation failure typically occurs under SNR in sand with 24 < Dr < 65%, and limited deformation may take place in dense sand with Dr ≥ 65%. In this paper, a stress-void ratio-based predictive method is proposed to identify the likely mode of deformation/failure in sand under undrained shear loading with static shear. Furthermore, the cyclic resistance is evaluated at three different levels of γSA (i.e., small, γSA = 3%; moderate, γSA = 7.5%; and large, γSA = 20%). The results show that, independent of the density state, the cyclic resistance continuously decreases with an increase in α at the small γSA level, while it first decreases and then increases for both loose and dense sand at the moderate and large γSA levels.

Effect of a Support Tower on the Performance and Wake of a Tidal Current Turbine

Tidal energy is one of the major sources of renewable energy. To accelerate the development of tidal energy, improved designs of Tidal Current Turbine (TCT) are necessary. The effect of tower on performance and wake of TCT is investigated using Computational Fluid Dynamics (CFD) simulations. Transient analysis with transient rotor stator frame change model and shear stress transport turbulence model are utilized in ANSYS CFX. An experimentally validated numerical model with full scale tidal turbine with a blockage ratio of 14.27% and Tip Speed Ratio (TSR) 4.87 is used to simulate the effect of different tower diameters on performance and wake. The effect of different tower diameters is quantified in terms of coefficient of performance (CP). Coefficient of performance for a 3.5 m tower diameter is 0.472 which is followed by 3, 2.5 and 2 m with coefficients of performance of 0.476, 0.478 and 0.476 respectively. Similarly, the coefficient of thrust (CT) on the rotor for 3.5 m tower diameter is 0.902, for 3 m diameter 0.906 and for 2.5 and 2 m diameters are 0.908 and 0.906 respectively.

Probability-based assessment of number of equivalent uniform stress cycles

For seismic soil liquefaction triggering and performance assessments, durational effects in field-based evaluations are mostly represented by the magnitude of the seismic event. However, in the laboratory, the equivalent number of uniform shear stress cycle concept is used. Benefitting from the findings of both case history- and laboratory-based research streams requires the conversion of earthquake-induced transient shear stresses to equivalent uniform (harmonic) stress cycles, or vice versa. A critical review of currently existing studies has revealed that; i) significantly extended earthquake catalogs are now available, which enable improved assessment of the conversion scheme, ii) based on the findings of Cetin and Bilge, weighting factors (m values) of stress conversions are now known to be stress, strain and density state dependent, and iii) these weighting factors extend to ranges that exceed the limits of earlier studies. Inspired by these, a semi-empirical probability-based model for the estimation of equivalent number of uniform stress cycles as functions of earthquake, site and performance (either strain or pore pressure-based) parameters is proposed. The proposed predictive relationship is shown to be more accurate and precise, evident by higher R2 and smaller model error standard deviations. However, despite significant improvement to an R2 value of 0.30, it is concluded to be still low, which addresses the uncertainties involved in duration assessments of earthquake shaking, and the need for further research. The probabilistic use of the proposed model is illustrated for a sandy soil layer at a soil site, which is expected to be shaken by a scenario earthquake event.

Influence of undulating wall heat and mass flux on MHD natural convection boundary layer flow from a vertical wall

AbstractCurrent study expounds an unsteady magnetohydrodynamic natural convective flow along a vertical wall in presence of variable transverse magnetic field. Small amplitude undulation in wall heat flux and wall mass flux are imposed at the vertical wall to generate the boundary layer flow. The flow governing equations are divided into sets of steady and unsteady equations and then transformed into the similarity and nonsimilarity equations, respectively, by introducing stream function formulations. The sets of nonsimilarity equations are solved numerically by using three different techniques, namely, perturbation solution technique, asymptotic solution technique and implicit finite difference technique applied, respectively, for lower, higher, and all frequencies (ξ). Results are illustrated in connection with the amplitude and phase angles of shear stress, wall temperature, and concentration against the frequency (ξ) for wide ranges of physically significant parameters. Likening of the results obtained by above mentioned numerical methods are presented in every figure and table. Results reveal that the amplitude of undulating shear stress and wall temperature dwindle and the amplitude of wall concentration increases due to increment in Prandtl number (Pr). Besides, on incrementing Schmidt number (Sc) the amplitude of undulating shear stress and wall concentration dwindle and the amplitude of wall temperature increases. Results also reveal that on incrementing magnetic parameter (M) the amplitude of transient shear stress dwindles while the amplitude of transient wall temperature and concentration increase.

Damage to the rat cerebrum under in vitro sinusoidal translational shear deformation

Blast waves, which induce sinusoidal shear waves within brain tissue, may cause mild traumatic brain injury (mTBI). To identify damage from a shear deformation wave, sagittal slices of rat cerebra are subjected to 50 cycles of translational shear deformation at six fixed frequencies between 25 Hz and 125 Hz and displacement amplitudes of 10% or 25% of the original length of the specimen. Each deformation frequency produces transient and apparent steady shear stress states that frequency analysis describes by their harmonic wavelet and Fourier frequency components. The dominant frequency components are integer multiples of the applied deformation frequency. The morphology of the shear stress versus time curve, and probably the type of damage, changes with deformation frequency. Damage at the lower frequencies appears to be diffuse bond breaking. Imaging and histology do not clearly detect mild damage due to bond breaking that underlies mTBI, which the analysis of the shear stress response captures. Major transitions in the morphology of the stress response in the two regions occur at about 75 Hz deformation frequency, possibly due to minor damage to cerebral substructures. An increase in deformation frequency increases the drag force between the extracellular fluid and solid matter. The deformation frequency dependence of the shear stress response makes protection against blast mTBI more difficult because the frequency content of a blast wave is not known a priori.

Froude supercritical flow processes and sedimentary structures: New insights from experiments with a wide range of grain sizes

AbstractRecognition of Froude supercritical flow deposits in environments that range from rivers to the ocean floor has triggered a surge of interest in their flow processes, bedforms and sedimentary structures. Interpreting these supercritical flow deposits is especially important because they often represent the most powerful flows in the geological record. Insights from experiments are key to reconstruct palaeo‐flow processes from the sedimentary record. So far, all experimentally produced supercritical flow deposits are of a narrow grain‐size range (fine to medium sand), while deposits in the rock record often consist of a much wider grain‐size distribution. This paper presents results of supercritical‐flow experiments with a grain‐size distribution from clay to gravel. These experiments show that cyclic step instabilities can produce more complex and a larger variety of sedimentary structures than the previously suggested backsets and ‘scour and fill’ structures. The sedimentary structures are composed of irregular lenses, mounds and wedges with backsets and foresets, as well as undulating planar to low‐angle upstream and downstream dipping laminae. The experiments also demonstrate that the Froude number is not the only control on the sedimentary structures formed by supercritical‐flow processes. Additional controls include the size and migration rate of the hydraulic jump and the substrate cohesion. This study further demonstrates that Froude supercritical flow promotes suspension transport of all grain sizes, including gravels. Surprisingly, it was observed that all grain sizes were rapidly deposited just downstream of hydraulic jumps, including silt and clay. These results expand the range of dynamic mud deposition into supercritical‐flow conditions, where local transient shear stress reduction rather than overall flow waning conditions allow for deposition of fines. Comparison of the experimental deposits with outcrop datasets composed of conglomerates to mudstones, shows significant similarities and highlights the role of hydraulic jumps, rather than overall flow condition changes, in producing lithologically and geometrically complex stratigraphy.

Nonlinear shear of entangled polymers from nonequilibrium molecular dynamics

ABSTRACTThis study aims to use molecular dynamics (MD) simulations of Kremer–Grest (KG) chains to inform future developments of models of entangled polymer dynamics. We perform nonequilibrium MD simulations, under shear flow, for well‐entangled KG chains. We study chains of 512 and 1000 KG beads, corresponding to 8 and 15 entanglements, respectively. We compute the linear rheological properties from equilibrium simulations of the stress autocorrelation and obtain from these data the tube model parameters. Under nonlinear shear flow, we compute the shear viscosity, the first and second normal stress differences, and chain contour length. For chains of 512 monomers, we obtain agreement with the results of Cao and Likhtman (ACS Macro. Lett. 2015, 4, 1376). We also compare our nonlinear results with the Graham, Likhtman and Milner‐McLeish (GLaMM) model. We identify some systematic disagreement that becomes larger for the longer chains. We made a comparison of the transient shear stress maximum from our simulations, two nonlinear models and experiments on a wide range of melts and solutions, including polystyrene (PS), polybutadiene, and styrene–butadiene rubber. This comparison establishes that the PS melt data show markedly different behavior to all other melts and solutions and KG simulations reproduce the PS data more closely than either the GLaMM or Xie and Schweizer models. We discuss the performance of these models against the data and simulations. Finally, by imposing a rapid reversing flow, we produce a method to extract the recoverable strain from MD simulations, valid for sufficiently entangled monodisperse polymers. We explore how the resulting data can probe the melt state just before the reversing flow. © 2019 The Authors. Journal of Polymer Science Part B: Polymer Physics published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1692–1704