A first-order physical model for the prediction of shear-induced particle migration and lubricating layer formation during concrete pumping

2021 ◽  
Vol 147 ◽  
pp. 106530
Author(s):  
Shirin Fataei ◽  
Egor Secrieru ◽  
Viktor Mechtcherine ◽  
Nicolas Roussel
Keyword(s):  
Physical Model ◽  
Particle Migration ◽  
Layer Formation ◽  
First Order ◽  
Lubricating Layer ◽  
Concrete Pumping

scholarly journals Experimental Investigation of the Pumping of a Model-Concrete through Pipes

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1161
Author(s):  
Martin A. Haustein ◽  
Moritz N. Kluwe ◽  
Rüdiger Schwarze
Keyword(s):  
Pressure Loss ◽  
Plug Flow ◽  
Particle Migration ◽  
Test Plant ◽  
Flow Profile ◽  
Time Resolved ◽  
Rheological Measurements ◽  
Lubricating Layer ◽  
Image Velocimetry ◽  
First Time

Many practical aspects of processing fresh concrete depend on its rheology, such as the pumping of the material. It is known that a lubricating layer is formed in the process, which significantly reduces the pumping pressure. However, these phenomena can hardly be considered in the usual rheological measurements. A main problem is the optical inaccessibility of the material, which prevents estimations about, e.g., the thickness of the plug flow or particle migration. In this paper, the pneumatic pumping of a transparent model concrete is performed by means of a test plant. The flow profile over the entire pipe cross-section is resolved in time and space via Particle Image Velocimetry (PIV) measurements. This allows the comparison with the analytical flow profile from rheological measurements of the material using the Buckingham–Reiner equation. A reduction of the pressure loss to around 60% induced through segregation of the material is found. These measurements reflect the rheology of the material under realistic pumping conditions including particle migration. This makes it possible for the first time to observe a transparent material with concrete-like rheology under pulsating pumping conditions and to compare the true and calculated time-resolved pressure loss.

scholarly journals Experimental Insights into Concrete Flow-Regimes Subject to Shear-Induced Particle Migration (SIPM) during Pumping

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1233 ◽  
Author(s):  
Shirin Fataei ◽  
Egor Secrieru ◽  
Viktor Mechtcherine
Keyword(s):  
Flow Pattern ◽  
Volume Fraction ◽  
Discharge Rate ◽  
High Volume ◽  
Particle Migration ◽  
Hardened Concrete ◽  
Concrete Pipe ◽  
Lubricating Layer ◽  
Definition Of ◽  
Concrete Flow

In this paper, the authors have focused on shear-induced particle migration (SIPM), its effect on concrete flow patterns, and lubricating layer formation during pumping. For this purpose, various volume-fractions ϕ of aggregates were selected. The particle migration was analyzed by applying two methods: sampling hardened concrete exposed to pumping and performing X-ray microcomputed tomography (μCT) and image analysis to determine the thickness of the lubricating layer due to SIPM. The results indicate that the first approach is unsuitable due to the nearly equal molecular density of particles and matrix. The second approach indicated that the actual thickness of the lubricating layer depends on the discharge rate as well as on ϕ and viscosity of concrete bulk; hence, it cannot be defined as a constant parameter for all concrete mixtures. Additionally, the concrete pipe-flow pattern, i.e., plug versus shear flow, was captured and studied while considering pumping pressure and discharge rate. It was concluded that particle migration is essential in the cases of both flowable and very flowable concretes with a high volume-fraction of solids. The changes in rheological properties caused by SIPM are severe enough to influence the definition of the flow pattern as plug or shear and the discharge rate of pumped concrete as well.

scholarly journals An Implicitly Balanced Hurricane Model with Physics-Based Preconditioning

2005 ◽  
Vol 133 (4) ◽  
pp. 1003-1022 ◽  
Author(s):  
J. M. Reisner ◽  
A. Mousseau ◽  
A. A. Wyszogrodzki ◽  
D. A. Knoll
Keyword(s):  
Linear System ◽  
Physical Model ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Solution Procedure ◽  
Sound Waves ◽  
Time Step ◽  
Efficient Manner ◽  
First Order ◽  
Implicit Approach

A numerical framework for simulating hurricanes based upon solving a nonlinear equation set with an implicitly balanced solution procedure is described in this paper. The physical model is the Navier–Stokes equations plus a highly simplified and differentiable microphysics parameterization package. Because the method is fully implicit, the approach is able to employ time steps that result in Courant–Friedrichs–Lewy (CFL) numbers greater than one for advection, gravity, and sound waves; however, the dynamical time scale of the problem must still be respected for accuracy. The physical model is solved via the Jacobian-free Newton–Krylov (JFNK) method. The JFNK approach typically requires the approximate solution of a large linear system several times per time step. To increase the efficiency of the linear system solves, a physics-based preconditioner has been employed. To quantify the accuracy and efficiency of the new approach against traditional approaches, the implicitly balanced solver was first compared against semi-implicit approaches for the simulation of a precipitating moist bubble. The moist-bubble simulations demonstrated the ability of the implicitly balanced approach to achieve a given level of accuracy in a more efficient manner than either a first-order semi-implicit approach or a traditional leapfrog semi-implicit approach. This behavior is further illustrated in first-of-a-kind three-dimensional implicitly balanced hurricane simulations that reveal the first-order-in-time semi-implicit algorithm needs to take a time step at least 60 times smaller than the implicitly balanced algorithm to produce a comparable accuracy.

scholarly journals Modeling the kinetics of essential oil hydrodistillation from plant materials

2013 ◽  
Vol 67 (5) ◽  
pp. 843-859 ◽  
Author(s):  
Svetomir Milojevic ◽  
Dragana Radosavljevic ◽  
Vladimir Pavicevic ◽  
Srdjan Pejanovic ◽  
Vlada Veljkovic
Keyword(s):  
Essential Oil ◽  
Essential Oils ◽  
Physical Model ◽  
Steam Distillation ◽  
Sigmoid Function ◽  
Plant Materials ◽  
Operational Conditions ◽  
First Order ◽  
Kinetics Of ◽  
And Diffusion

The present work deals with modeling the kinetics of essential oils extraction from plant materials by water and steam distillation. The experimental data were obtained by studying the hydrodistillation kinetics of essential oil from juniper berries. The literature data on the kinetics of essential oils hydrodistillation from different plant materials were also included into the modeling. A physical model based on simultaneous washing and diffusion of essential oil from plant materials were developed to describe the kinetics of essential oils hydrodistillation, and two other simpler models were derived from this physical model assuming either instantaneous washing followed by diffusion or diffusion with no washing (i.e. the first-order kinetics). The main goal was to compare these models and suggest the optimum ones for water and steam distillation and for different plant materials. All three models described well the experimental kinetic data on water distillation irrespective of the type of distillation equipment and its scale, the type of plant materials and the operational conditions. The most applicable one is the model involving simultaneous washing and diffusion of the essential oil. However, this model was generally inapplicable for steam distillation of essential oils, except for juniper berries. For this hydrodistillation technique, the pseudo first-order model was shown to be the best one. In a few cases, a variation of the essential oil yield with time was observed to be sigmoidal and was modeled by the Boltzmann sigmoid function.

scholarly journals A First-Order Mechanical Device to Model Traumatized Craniovascular Biodynamics

2006 ◽  
Vol 1 (1) ◽  
pp. 89-95
Author(s):  
Sean S. Kohles ◽  
Ryan W. Mangan ◽  
Edward Stan ◽  
James McNames
Keyword(s):  
Mathematical Models ◽  
Physical Model ◽  
Brain Tissue ◽  
Head Injuries ◽  
Post Injury ◽  
Traumatic Head Injury ◽  
First Order ◽  
Mechanical Models ◽  
Bed Position ◽  
Poiseuille’S Equation

Mathematical models currently exist that explore the physiology of normal and traumatized intracranial function. Mechanical models are used to assess harsh environments that may potentially cause head injuries. However, few mechanical models are designed to study the adaptive physiologic response to traumatic brain injury. We describe a first-order physical model designed and fabricated to elucidate the complex biomechanical factors associated with dynamic intracranial physiology. The uni-directional flow device can be used to study interactions between the cranium, brain tissue, cerebrospinal fluid, vasculature, blood, and the heart. Solid and fluid materials were selected to simulate key properties of the cranial system. Total constituent volumes (solid and fluid) and volumetric flow (650ml∕min) represent adult human physiology, and the lengths of the individual segments along the flow-path are in accord with Poiseuille’s equation. The physical model includes a mechanism to simulate autoregulatory vessel dynamics. Intracranial pressures were measured at multiple locations throughout the model during simulations with and without post-injury brain tissue swelling. Two scenarios were modeled for both cases: Applications of vasodilation/constriction and changes in the head of bed position. Statistical results indicate that all independent variables had significant influence over fluid pressures measured throughout the model (p<0.0001) including the vasoconstriction mechanism (p=0.0255). The physical model represents a first-order design realization that helps to establish a link between mathematical and mechanical models. Future designs will provide further insight into traumatic head injury and provide a framework for unifying the knowledge gained from mathematical models, injury mechanics, clinical observations, and the response to therapies.

scholarly journals Estimation of Lubrication Layer Thickness and Composition through Reverse Engineering of Interface Rheometry Tests

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1799
Author(s):  
Alexis Salinas ◽  
Dimitri Feys
Keyword(s):  
Particle Size ◽  
Pipe Wall ◽  
Single Layer ◽  
Particle Migration ◽  
Particle Sizes ◽  
Maximum Particle Size ◽  
Lubrication Layer ◽  
Concrete Pumping ◽  
Maximum Particle ◽  
Sand Particles

During concrete pumping, a lubrication layer is formed near the pipe wall. Extensive research has been performed on measuring and modeling the properties of this layer and using these values to predict pumping pressures. However, there are numerous discussions in the literature about the composition and thickness of this layer: can it be considered mortar, a micromortar, or is it cement paste? In this paper, possible solutions for the thickness and composition of the lubrication layer are derived from interface rheometry tests. It is assumed that the lubrication layer is composed of one or more concentric layers of paste or micromortar. To accomplish this determination, the rheological properties of the composing paste, mortars with different maximum particle sizes and concrete need to be known. Challenges arising from using different rheometers and from the sensitivity of the paste rheology to shearing are addressed in this contribution. The results show that, mathematically, a single layer of homogeneous paste or mortar with different maximum particle sizes can be responsible for the formation of the lubrication layer. Physically, however, the composing material should contain sand particles to some extent, as particle migration is proportional to the size squared. If the literature results from pumping are applicable to the results obtained in this paper, it seems that the lubrication layer is composed of a mortar with a maximum particle size of around 1 to 2 mm.

Dynamic Model for a Dome-Loaded Pressure Regulator

1997 ◽  
Vol 122 (2) ◽  
pp. 290-297 ◽  
Author(s):  
A. Nabi ◽  
E. Wacholder ◽  
J. Dayan
Keyword(s):  
Physical Model ◽  
Lumped Parameter Model ◽  
Pressure Regulator ◽  
Flow Rates ◽  
First Order ◽  
Runge Kutta Method ◽  
Lumped Parameter ◽  
Wide Range ◽  
Fast Acting ◽  
Good Agreement

A generalized physical model describing dynamic behavior of a fast-acting, dome-loaded, gas pressure regulator was developed. The regulator is designed to respond quickly to command changes, and to operate over a wide range of flow rates and pressures. The analytical lumped-parameter model developed consists of a set of nonlinear, first-order, ordinary differential equations with respect to time, accounting for mass and energy conservation at regulator outlet, command dome and internal feedback compartments. It also accounts for the equation-of-motion for the poppet and the control piston-assembly. The numerical solution, based on a Runge–Kutta method, is amenable to an extensive parametric study of regulator performance, and serves as a useful analytical tool for designing new pressure regulators. Several tests were performed on a fast-acting regulator to verify the physical model. Good agreement between predictions and measurements was obtained. The effect of several parameters, geometrical and operational, on regulator performance was studied. [S0022-0434(00)00402-0]

scholarly journals Definition of Forming Processes Microparameters for Epitropic Liquid Crystal Boundary Lubrication Layers

2020 ◽  
Vol 20 (4) ◽  
pp. 72-77
Author(s):  
A. G. Zheleznov ◽  
V. A. Godlevskiy ◽  
O. V. Blinov
Keyword(s):  
Liquid Crystal ◽  
Boundary Lubrication ◽  
Molecular Modelling ◽  
Layer Formation ◽  
Crystal Boundary ◽  
Lubricating Layer ◽  
Lubrication Layer ◽  
Efficiency Parameter ◽  
Definition Of ◽  
Modelling Methods

The kinetics theory of ordered boundary lubricating layer formation is presented. The theory contains the description of the formation of boundary lubricating layer from liquid lubricating media containing tribo-active adsorbing component. The expressions for specific forming time and thickness of the boundary lubrication layer in the conditions of the considered model are defined. The prospects of the mentioned parameters experimental definition they are marked out. The tribological efficiency parameter of tribological additive is introduced. This parameter can be evaluated in model physicochemical researches or by molecular modelling methods.

Dual systems for all: Higher-order, role-based relational reasoning as a uniquely derived feature of human cognition

2019 ◽  
Vol 42 ◽  
Author(s):  
Daniel J. Povinelli ◽  
Gabrielle C. Glorioso ◽  
Shannon L. Kuznar ◽  
Mateja Pavlic
Keyword(s):  
Temporal Reasoning ◽  
Higher Order ◽  
Important Case ◽  
Human Cognition ◽  
Relational Reasoning ◽  
Dual Systems ◽  
First Order ◽  
Reasoning System ◽  
Role Based

Abstract Hoerl and McCormack demonstrate that although animals possess a sophisticated temporal updating system, there is no evidence that they also possess a temporal reasoning system. This important case study is directly related to the broader claim that although animals are manifestly capable of first-order (perceptually-based) relational reasoning, they lack the capacity for higher-order, role-based relational reasoning. We argue this distinction applies to all domains of cognition.

Sign in / Sign up

Export Citation Format

Share Document