Computer Simulations of Low Concentrations Slurry Flows in Pipelines

2000 ◽  
Author(s):  
Yuri Leonenko ◽  
Oleg Vinogradov
Keyword(s):  
Fluid Velocity ◽  
Dynamics Model ◽  
Simple Experiment ◽  
Heterogeneous Flow ◽  
Volumetric Density ◽  
Low Concentrations ◽  
System Of Particles ◽  
Slurry Flows ◽  
Critical Velocities ◽  
Two Parameters

In the paper a discrete system of particles carried by fluid is considered in a planar motion. The volumetric density of particles is taken between 1% and 2% so that they can be treated within the framework of a discrete dynamics model. The fluid is then considered as a carrier of particles. The Landau-Lifshitz concept of turbulence is used to describe the fluctuating part of fluid velocity. This approach is applied to simulate different regimes (laminar and turbulent) and various states of particle motion (moving bed, heterogeneous flow, and homogeneous flow) using only two parameters, which have to be determined experimentally. These two parameters, found for a particular pipe and for a particular velocity from a simple experiment, then have been used for simulations of flow for other pipe diameters and different velocities. The results agree favorably with experimental observations of the type of slurry flow and critical velocities identifying transitions from one type to another.

scholarly journals Numerical Investigation of Jamming of Solid Particles in a Straight Pipe

1996 ◽  
Author(s):  
Yi Sun ◽  
Oleg Vinogradov
Keyword(s):  
Fluid Flow ◽  
Fluid Velocity ◽  
Solid Particles ◽  
Spherical Particles ◽  
Critical Parameters ◽  
Straight Pipe ◽  
Volumetric Density ◽  
Physical Experiments ◽  
Variable Topology ◽  
Two Parameters

The flow of fluids containing solid particles is numerically simulated in order to determine the critical parameters of the system leading to a jam. Two parameters are varied: the volumetric density of solid particles and the velocity of fluid flow. The energy dissipation in the system is due to dry friction losses and collisions. The results presented are based on the mathematical models of granular materials treated as multibody systems with variable topology. The fluid flow is considered to be potential. It is shown that jamming strongly depends on the volumetric density of particles and fluid velocity. The results of numerical experiments are in qualitative agreement with physical experiments of flow of spherical particles in a pipe.

scholarly journals Calculation of the maximum velocity of gravity flow in the pond-clarifier with higher aquatic plants

2020 ◽  
Vol 168 ◽  
pp. 00061
Author(s):  
Yevhen Semenenko ◽  
Tetіana Demchenko ◽  
Artyom Pavlichenko
Keyword(s):  
Free Surface ◽  
Aquatic Plants ◽  
Fluid Velocity ◽  
Maximum Velocity ◽  
Resistance Coefficient ◽  
Gravity Flow ◽  
Recycled Water ◽  
Higher Aquatic Plants ◽  
Two Parameters ◽  
The Given

The analysis of the possible maximum fluid flow rates when using higher aquatic plants for clarification of recycled water in the pondclarifier of the tailing pond has carried out. The study has been performed on the basis of a mathematical model of a plane slow stationary gravity flow of a viscous fluid in two parallel layers. The results of the study made it possible to determine the fluid velocity through a layer of higher aquatic plants floating on a free surface. The maximum possible velocity depending on the layer porosity has been determined. This value is necessary to determine the rational parameters of the process of clarifying technical recycled water from particles of the given hydraulic size, taking into account the pond-clarifier geometric dimensions. It is shown that the velocity in the layer with higher aquatic plants has been determined by the ratio of two parameters of this layer - porosity and dimensionless resistance coefficient. It has been shown that the maximum velocity value coefficient in the layer with plants floating on free surface depends only on porosity of this layer and does not depend on its resistance coefficient.

scholarly journals The Use of Statistical Tests to Calibrate the Black-Scholes Asset Dynamics Model Applied to Pricing Options with Uncertain Volatility

2012 ◽  
Vol 2012 ◽  
pp. 1-20 ◽  
Author(s):  
Lorella Fatone ◽  
Francesca Mariani ◽  
Maria Cristina Recchioni ◽  
Francesco Zirilli
Keyword(s):  
Statistical Tests ◽  
Statistical Significance ◽  
Asset Price ◽  
Real Data ◽  
Dynamics Model ◽  
Stochastic Dynamical Systems ◽  
Pricing Options ◽  
Black Scholes ◽  
Uncertain Volatility ◽  
Two Parameters

A new method for calibrating the Black-Scholes asset price dynamics model is proposed. The data used to test the calibration problem included observations of asset prices over a finite set of (known) equispaced discrete time values. Statistical tests were used to estimate the statistical significance of the two parameters of the Black-Scholes model: the volatility and the drift. The effects of these estimates on the option pricing problem were investigated. In particular, the pricing of an option with uncertain volatility in the Black-Scholes framework was revisited, and a statistical significance was associated with the price intervals determined using the Black-Scholes-Barenblatt equations. Numerical experiments involving synthetic and real data were presented. The real data considered were the daily closing values of the S&P500 index and the associated European call and put option prices in the year 2005. The method proposed here for calibrating the Black-Scholes dynamics model could be extended to other science and engineering models that may be expressed in terms of stochastic dynamical systems.

Analysis of Influence of the Roller Number and Rolling Schedule to Straighten Quality of the Project Steel Bar

2013 ◽  
Vol 437 ◽  
pp. 590-596
Author(s):  
Xi Jian Zheng ◽  
Lei Ma ◽  
Yu Fei Zhu
Keyword(s):  
Reference Value ◽  
System Dynamics Model ◽  
Dynamics Model ◽  
Rolling Schedule ◽  
Actual Measurement ◽  
Steel Bar ◽  
Simulation Results ◽  
Two Parameters ◽  
Domestic Manufacturer

Roll number and rolling schedule are the important parameters affecting the quality of steel bar straightening，when domestic manufacturer design the straightening equipment, these two parameters design basic is by analogy, so it is necessary to study these two parameters. This paper calculated the straightening roller to obtain reasonable roll number; next step quantitative calculate to obtains the theory rolling schedule, in the meantime actual measurement to obtains the practical rolling schedule of the same equipment；then based on rigid-flexible virtual prototype technology to build straightening system dynamics model. At the theory rolling schedule, and the practical rolling schedule for steel bar straighten emulation, obtained straightness and deviation of different diameter steel bar after straightening. By comparison and analysis the simulation results, we obtain the reasonable roll number and rolling schedule. In this paper, this method have reference value to design the roll number and rolling schedule for similar straightening equipment.

Design of the EMF-PF and Error Correction

2014 ◽  
Vol 936 ◽  
pp. 1587-1591
Author(s):  
Kai Xia Wei
Keyword(s):  
Error Correction ◽  
Fluid Velocity ◽  
Electromagnetic Flowmeter ◽  
Order Correction ◽  
Third Order ◽  
The Third ◽  
Two Parameters

This paper designs the electromagnetic flowmeter in partially filled pipes (EMF-PF), which sensor alternate duties, sensing both the fluid velocity and fill height signals in order to get the flow in the partially filled pipes. Because the errors caused by two parameters measured, different sensitivities and zero-shifts reduce the accuracy of the EMF-PF, therefore calibration is needed. The repeated tests show that the third-order correction of the errors achieved good results.

scholarly journals Properties of pyruvate dehydrogenase of rat mammary tissue and its changes during pregnancy, lactation and weaning

1974 ◽  
Vol 142 (1) ◽  
pp. 87-95 ◽  
Author(s):  
Haldane G. Coore ◽  
Barbara Field
Keyword(s):  
Enzyme Activity ◽  
Pyruvate Dehydrogenase ◽  
Time Course ◽  
Active Form ◽  
Mammary Tissue ◽  
Similar Time ◽  
Total Enzyme Activity ◽  
Low Concentrations ◽  
Two Parameters ◽  
Total Enzyme

Pyruvate dehydrogenase of rat mammary tissue showed many of the regulatory properties of the analogous enzyme in other mammalian tissues. It was inactivated in the presence of low concentrations of ATP and this rate of inactivation was slowed if pyruvate or PP1 was also present. Reactivation by Mg2+ in the presence of low concentrations of Ca2+ occurred over a similar time-course. The Km value for Mg2+ in this process was about 2mm. The enzyme was assayed in extracts of freeze-clamped mammary glands removed from pregnant, lactating or recently weaned rats under halothane anaesthesia. Both the initial activity and the activity after full activation (‘total enzyme activity’) were determined. The former parameter, when expressed on a DNA basis, varied within a range of 40 times its lowest value. Maximum total enzyme activity was about 1 unit/g wet wt. The total enzyme activity and the fraction in the active form increased in step from pregnancy to mid-lactation, remained elevated until the end of lactation and then fell steeply within 3 days after weaning. The correlation of these two parameters of enzyme activity may indicate a common regulatory factor or else an interdependence arising from inherent properties of the multi-enzyme complex.

scholarly journals Quenching active swarms: effects of light exposure on collective motility in swarming Serratia marcescens

2019 ◽  
Vol 16 (156) ◽  
pp. 20180960 ◽  
Author(s):  
Junyi Yang ◽  
Paulo E. Arratia ◽  
Alison E. Patteson ◽  
Arvind Gopinath
Keyword(s):  
Serratia Marcescens ◽  
Brownian Dynamics ◽  
Large Scale ◽  
Light Exposure ◽  
Wide Spectrum ◽  
Dynamics Model ◽  
Planktonic Bacteria ◽  
Starting Point ◽  
Active Bacteria ◽  
Two Parameters

Swarming colonies of the light-responsive bacteria Serratia marcescens grown on agar exhibit robust fluctuating large-scale flows that include arrayed vortices, jets and sinuous streamers. We study the immobilization and quenching of these collective flows when the moving swarm is exposed to intense wide-spectrum light with a substantial ultraviolet component. We map the emergent response of the swarm to light in terms of two parameters—light intensity and duration of exposure—and identify the conditions under which collective motility is impacted. For small exposure times and/or low intensities, we find collective motility to be negligibly affected. Increasing exposure times and/or intensity to higher values suppresses collective motility but only temporarily. Terminating exposure allows bacteria to recover and eventually reestablish collective flows similar to that seen in unexposed swarms. For long exposure times or at high intensities, exposed bacteria become paralysed and form aligned, jammed regions where macroscopic speeds reduce to zero. The effective size of the quenched region increases with time and saturates to approximately the extent of the illuminated region. Post-exposure, active bacteria dislodge immotile bacteria; initial dissolution rates are strongly dependent on duration of exposure. Based on our experimental observations, we propose a minimal Brownian dynamics model to examine the escape of exposed bacteria from the region of exposure. Our results complement studies on planktonic bacteria, inform models of patterning in gradated illumination and provide a starting point for the study of specific wavelengths on swarming bacteria.

scholarly journals Emergence of moderate opinions as a consequence of group pressure

2019 ◽  
Vol 30 (11) ◽  
pp. 1950091 ◽  
Author(s):  
Nuno Crokidakis
Keyword(s):  
Order Parameter ◽  
Opinion Dynamics ◽  
Dynamics Model ◽  
High Group ◽  
Group Pressure ◽  
Agent Interactions ◽  
Stochastic Parameters ◽  
Two Phases ◽  
Two Parameters ◽  
Fully Connected

In this work, we study a continuous opinion dynamics model considering 3-agent interactions and group pressure. Agents interact in a fully-connected population, and two parameters govern the dynamics: the agents’ convictions [Formula: see text] that are homogeneous in the population, and the group pressure [Formula: see text]. Stochastic parameters also drive the interactions. Our analytical and numerical results indicate that the model undergoes symmetry-breaking transitions at distinct critical points [Formula: see text] for any value of [Formula: see text], i.e. the transition can be suppressed for sufficiently high group pressure. Such transition separates two phases: for any [Formula: see text], the order parameter [Formula: see text] is identically null ([Formula: see text], a symmetric, absorbing phase), while for [Formula: see text], we have [Formula: see text], i.e. a symmetry-broken phase (ferromagnetic). The numerical simulations also reveal that the increase of group pressure leads to a wider distribution of opinions, decreasing the extremism in the population.

scholarly journals Existence of strong solutions to a fluid-structure system with a structure given by a finite number of parameters

2020 ◽  
Vol 54 (1) ◽  
pp. 301-333
Author(s):  
Guillaume Delay
Keyword(s):  
Stokes Equations ◽  
Virtual Work ◽  
Mixed Boundary ◽  
Fluid Velocity ◽  
Local Existence ◽  
Strong Solutions ◽  
Mixed Boundary Conditions ◽  
Fluid Structure ◽  
Structure System ◽  
Two Parameters

We study the existence of strong solutions to a 2d fluid-structure system. The fluid is modelled by the incompressible Navier–Stokes equations. The structure represents a steering gear and is described by two parameters corresponding to angles of deformation. Its equations are derived from a virtual work principle. The global domain represents a wind tunnel and imposes mixed boundary conditions to the fluid velocity. Our method reposes on the analysis of the linearized system. Under a compatibility condition on the initial data, we can guarantee local existence in time of strong solutions to the fluid-structure problem.

Modeling and Analysis of an Gantry Crane with Flexible Cable

2013 ◽  
Vol 753-755 ◽  
pp. 1054-1059
Author(s):  
Wen Zheng Du ◽  
Zheng Xie
Keyword(s):  
Operating Conditions ◽  
Gantry Crane ◽  
Dynamics Model ◽  
Coupled Dynamics ◽  
Modeling And Analysis ◽  
Flexible Cable ◽  
Simulation Results ◽  
Set Up ◽  
Two Parameters ◽  
Gantry Cranes

This paper introduces a novel mathematical model that using the Hamiltons' principle to set up coupled dynamics model of gantry cranes with flexible cable. By using finite element method to solve the equations that govern the motion of the crane system. Numerical simulations for the coupled dynamics model are presented for various operating conditions, and compared to the simulation results of the model with cranes made with rigid cable under the same working conditions. From the consequence, we can get the effects of cable's flexibility on gantry crane's kinematical properties; According to the conclusions, this paper defines two parameters of the gantry cranes, and qualitatively analyzes the two parameters' effects on dynamics kinematical properties of gantry cranes.

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