scholarly journals Study of Local Inertial Focusing Conditions for Spherical Particles in Asymmetric Serpentines

2019 ◽  
Author(s):  
Eric Pedrol ◽  
Jaume Massons ◽  
Francesc Díaz ◽  
Magdalena Aguiló
Keyword(s):  
Numerical Simulation ◽  
Flow Rate ◽  
Spherical Particles ◽  
Flow Rates ◽  
Inertial Focusing ◽  
Dean Vortices ◽  
State Diagrams ◽  
Spreading Function ◽  
Simulation Results ◽  
Particles Trajectories

Inertial focusing conditions of fluorescent polystyrene spherical particles are studied at the pointwise level along their pathlines. This is accomplished by an algorithm that calculates a de-gree of spreading function of the particles' trajectories taking streaklines images as raw data. Different confinement ratios of the particles and flow rates are studied and the results are pre-sented in state diagrams showing the focusing degree of the particles in terms of their position within a curve of an asymmetric serpentine and the applied flow rate. In addition, together with numerical simulation results, we present empirical evidence that the preferred trajectories of inertially focused spheres are contained within Dean vortices' centerlines. We speculate about the existence of a new force, never postulated before, to explain this fact.

scholarly journals Study of Local Inertial Focusing Conditions for Spherical Particles in Asymmetric Serpentines

Fluids ◽  
2019 ◽  
Vol 5 (1) ◽  
pp. 1
Author(s):  
Eric Pedrol ◽  
Jaume Massons ◽  
Francesc Díaz ◽  
Magdalena Aguiló
Keyword(s):  
Numerical Simulation ◽  
Flow Rate ◽  
Spherical Particles ◽  
Flow Rates ◽  
Inertial Focusing ◽  
Dean Vortices ◽  
State Diagrams ◽  
Spreading Function ◽  
Simulation Results ◽  
Particles Trajectories

Inertial focusing conditions of fluorescent polystyrene spherical particles are studied at the pointwise level along their pathlines. This is accomplished by an algorithm that calculates a degree of spreading function of the particles’ trajectories taking streaklines images as raw data. Different confinement ratios of the particles and flow rates are studied and the results are presented in state diagrams showing the focusing degree of the particles in terms of their position within a curve of an asymmetric serpentine and the applied flow rate. In addition, together with numerical simulation results, we present empirical evidence that the preferred trajectories of inertially focused spheres are contained within Dean vortices’ centerlines. We speculate about the existence of a new force, never postulated before, to explain this fact.

scholarly journals Application of the Robust Fixed Point Iteration Method in Control of the Level of Twin Tanks Liquid

Computation ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 96
Author(s):  
Hamza Khan ◽  
Hazem Issa ◽  
József K. Tar
Keyword(s):  
Numerical Simulation ◽  
Fixed Point ◽  
Nonlinear Systems ◽  
Flow Rate ◽  
Fluid Level ◽  
Process Industries ◽  
Fixed Point Iteration ◽  
Precise Control ◽  
Strongly Nonlinear ◽  
Simulation Results

Precise control of the flow rate of fluids stored in multiple tank systems is an important task in process industries. On this reason coupled tanks are considered popular paradigms in studies because they form strongly nonlinear systems that challenges the controller designers to develop various approaches. In this paper the application of a novel, Fixed Point Iteration (FPI)-based technique is reported to control the fluid level in a “lower tank” that is fed by the egress of an “upper” one. The control signal is the ingress rate at the upper tank. Numerical simulation results obtained by the use of simple sequential Julia code with Euler integration are presented to illustrate the efficiency of this approach.

Estimation of Leakage Mass Flow Rate through Labyrinth Seal Using CFD Techniques

2017 ◽  
Vol 3 (02) ◽  
Author(s):  
M Neeharika ◽  
Prabhat Kumar Hensh
Keyword(s):  
Numerical Simulation ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Flow Behavior ◽  
Labyrinth Seal ◽  
Empirical Correlation ◽  
Radial Clearance ◽  
Leakage Flow ◽  
Simulation Results

Seal design is an essential part for turbo machinery. Seal consisting of fins is placed in a gap between stationary and rotating component to minimize the leakage flow. Seal leakage flow has been considered as an inevitable loss factor that highly affects the efficiency of any machine. During operation of the equipment, thermal expansion/contraction of components take place, which causes variation of the gap between stationary and rotating component. Importance of the study is to understand the flow behavior due to variation of the gap. The variation of gap leads to change of radial clearance between fin to metal component and subsequent change of flow pattern. The main focus of the paper is to estimate the leakage flow through a labyrinth seal placed between rotor and casing of a typical steam turbine. Numerical techniques using 3D CFD tool are used for this purpose. Three different seal configurations are proposed in the study. The variables of the three seal configurations are radial clearance, number of fins in the flow passage and pressure drop across the seal passages. As an alternative methodology, an empirical correlation is formulated based on numerical simulation results for one set of radial clearance to estimate mass flow rate through the seal. In order to validate the formulated correlation, mass flow rate is determined for another set of radial clearance and compared with numerical simulation results. It is observed that flow rate estimated from 3D CFD study is around 20% lower compared to empirical correlation.

Study on the Porous Media Used in Numerical Simulation of Temperature Characteristic for Isothermal Chambers

2011 ◽  
Vol 291-294 ◽  
pp. 1689-1692
Author(s):  
Li Hong Yang ◽  
Da Hua Liu
Keyword(s):  
Numerical Simulation ◽  
Porous Medium ◽  
Porous Media ◽  
Flow Rate ◽  
Temperature Characteristic ◽  
Test Results ◽  
Temperature Characteristics ◽  
Simulation And Experiment ◽  
Simulation Results ◽  
Metal Wires

Isothermal chamber, which is fabricated by empty chamber stuffed with thin metal wires, is a kind of test devices for flow rate characteristics of pneumatic components, and its temperature characteristics are critical to the accuracy of test results. In this paper, the stuffers in isothermal chamber were considered as porous medium with large porosity, so the temperature characteristics could be studied by numerical simulation. Though there are differences between simulation and experiment, they have same trends and the law of variation can be seen from the simulation results, which demonstrates the reliability of numerical simulation. Consequently, simulation can be an efficient method, which is energy-saving and cost-reducing.

scholarly journals Importance of viscosity contrast for the motion of erythrocytes in microcapillaries

2021 ◽  
Author(s):  
Anil K. Dasanna ◽  
Johannes Mauer ◽  
Gerhard Gompper ◽  
Dmitry A. Fedosov
Keyword(s):  
Flow Rate ◽  
Blood Cells ◽  
Flow Resistance ◽  
Tube Flow ◽  
Membrane Tension ◽  
Flow Rates ◽  
Physical Mechanisms ◽  
State Diagrams ◽  
Viscosity Contrast

ABSTRACTThe dynamics and deformation of red blood cells (RBCs) in microcirculation affect the flow resistance and transport properties of whole blood. One of the key properties that can alter RBC dynamics in flow is the contrast λ (or ratio) of viscosities between RBC cytosol and blood plasma. Here, we study the dependence of RBC shape and dynamics on the viscosity contrast in tube flow, using mesoscopic hydrodynamics simulations. State diagrams of different RBC dynamical states, including tumbling cells, parachutes, and tank-treading slippers, are constructed for various viscosity contrasts and wide ranges of flow rates and tube diameters (or RBC confinements). Despite similarities in the classification of RBC behavior for different viscosity contrasts, there are notable differences in the corresponding state diagrams. In particular, the region of parachutes is significantly larger for λ = 1 in comparison to λ = 5. Furthermore, the viscosity contrast strongly affects the tumbling-to-slipper transition, thus modifying the regions of occurrence of these states as a function of flow rate and RBC confinement. Also, an increase in cytosol viscosity leads to a reduction in membrane tension induced by flow stresses. Physical mechanisms that determine these differences in RBC dynamical states as a function of λ are discussed.

scholarly journals The study of electrohydrodynamic printing by numerical simulation

2020 ◽  
Vol 71 (6) ◽  
pp. 413-418
Author(s):  
Xue Yang ◽  
Rui Liu ◽  
Lu Li ◽  
Zhifu Yin ◽  
Kai Chen ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Influencing Factors ◽  
Flow Rate ◽  
Applied Voltage ◽  
Promising Technique ◽  
Electrohydrodynamic Printing ◽  
Nozzle Size ◽  
Simulation Results

AbstractEHD (Electrohydrodynamic) printing is a promising technique for alternative fabrication of highresolution micro- and nanostructures without employment of any molds or photo-masks However, the printing precision can be easily influenced by the printing conditions, such as applied voltage, printing distance (the distance between the nozzle tip and the substrate), and flow rate. Unfortunately, up to now there was no work which analyzed those influencing factors in-depth and systematically by theory and numerical simulation. In this paper, the theory of EHD printing was presented and the effect of applied voltage, printing distance, and flow rate on the width of printed line was analyzed by numerical simulation. The simulation results showed that the width of printed lines is proportional to printing distance, nozzle size, and flow rate. However, it is inversely proportional to the applied voltage.

scholarly journals Numerical Simulation of Temperature Decrease in Greenhouses with Summer Water-Sprinkling Roof

Energies ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2435 ◽  
Author(s):  
Jiaming Guo ◽  
Yanhua Liu ◽  
Enli Lü
Keyword(s):  
Numerical Simulation ◽  
Three Dimensional ◽  
Simple Algorithm ◽  
Discrete Ordinates ◽  
Multiphase Model ◽  
Temperature Decrease ◽  
Turbulent Model ◽  
Flow Rates ◽  
Symmetrical Model ◽  
Simulation Results

Decreasing the temperature of a greenhouse in summer is very important for the growth of plants. To investigate the effects of a roof sprinkler on the heat environment of a greenhouse, a three-dimensional symmetrical model was built, in which a k-ε (k-epsilon) turbulent model, a DO (Discrete Ordinates) irrational model, a Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) algorithm, and a multiphase model were used to simulate the effects of the roof sprinkler, at different flow rates. Based on the simulation results, it was found that the temperature could be further reduced under a proper sprinkle rate, and the temperature distribution in the film on the roof was more uniform. A test was conducted to verify the accuracy of the model, which proved the validity of the numerical results. The simulation results of this study will be helpful for controlling and optimizing the heat environment of a greenhouse.

LATTICE BOLTZMANN SIMULATION OF THE MOTION OF SPHERICAL PARTICLES IN STEADY POISEUILLE FLOW

2009 ◽  
Vol 20 (06) ◽  
pp. 831-846 ◽  
Author(s):  
H. H. YI ◽  
L. J. FAN ◽  
Y. Y. CHEN
Keyword(s):  
Numerical Simulation ◽  
Fluid Flow ◽  
Poiseuille Flow ◽  
Lattice Boltzmann ◽  
Cylindrical Tube ◽  
Simulation Method ◽  
Three Dimensions ◽  
Spherical Particles ◽  
Lattice Boltzmann Simulation ◽  
Simulation Results

A technique, based on the stress-integration method, for the evaluation of hydrodynamic forces on solid boundaries is proposed to simulate the solid-fluid flow systems in three dimensions in lattice Boltzmann simulations. The accuracy of the scheme is demonstrated by simulating the sphere migrating in a pressure-driven Newtonian fluid flow in a cylindrical tube. The numerical simulation results recover the Segré–Silberberg effect. Using this scheme, we investigate the behavior of a pair of spheres in a tube Poiseuille flow. Oscillatory states are observed for two spheres with different radii placed on opposite sides. The simulation results show that the present model is an effective and efficient direct numerical simulation method for simulating particle motions in fluid flows at finite Reynolds numbers in three dimensions.

CONTROL OF A CHAOTIC SWITCHED ARRIVAL SYSTEM WITH CONTROLLED INTERNAL CONNECTIONS

2006 ◽  
Vol 16 (03) ◽  
pp. 701-707 ◽  
Author(s):  
WEI LI ◽  
TOSHIMITSU USHIO
Keyword(s):  
Numerical Simulation ◽  
Theoretical Analysis ◽  
Periodic Orbit ◽  
Chaotic Attractor ◽  
Control Variables ◽  
Flow Rates ◽  
Novel Method ◽  
Simulation Results ◽  
Internal Connections

In this paper, a chaotic switched arrival system with N buffers and controlled internal connections is considered. An unstable N periodic orbit embedded in the chaotic attractor is theoretically derived. A novel method for the stabilization of the unstable N periodic orbit using the flow rates of the internal connections as control variables is presented. It is showed that the switched arrival system can be stabilized by using N - 2 internal connections. Numerical simulation results are also provided to demonstrate the theoretical analysis.

On the Validation of a Differential Variational Inequality Approach for the Dynamics of Granular Material

2010 ◽  
Author(s):  
Dan Melanz ◽  
Martin Tupy ◽  
Bryce Smith ◽  
Kevin Turner ◽  
Dan Negrut
Keyword(s):  
Friction Coefficient ◽  
Granular Material ◽  
Flow Rate ◽  
Granular Flow ◽  
Solution Method ◽  
Time Data ◽  
Flow Rates ◽  
Macro Scale ◽  
Simulation Results ◽  
Experimental Runs

The validation of a DVI approach for the dynamics of granular material focuses on comparing the experimental and simulation results of granular flow for two tests in the Chrono::Engine simulation environment. A macro scale validation was previously carried out through examination of granular flow in PBR reactors [1]. For this work, an aluminum rig was designed and fabricated to measure the flow rate of a given amount of micro scale granular material flowing due to gravity through a slit. The flow was initiated by using a Newport UMR8.25 translational stage and Newport LTA-HL precision linear actuator to open and close the slit steadily. Once the slit was open, the weight of the granular material was transmitted to the processor via a router connected to a Cooper LFS242 Tension/Compression Cell (Serial No. 286284) and graphed over time. A model of the flow meter was created in Chrono::Engine and the results were matched to experimental runs by changing the friction coefficient between particles. After the friction coefficient of the particles was determined to be 0.15, several experimental runs with differing slit sizes were run. These flow rates were compared to the weight versus time data that Chrono::Engine output for the corresponding slit size. Runs for gap sizes of 1.5mm, 2.0mm, 2.5mm and 3.0mm were performed with 0.0624 N of granular material, which amounted to approximately 39,000 spheres with 500μm in diameter. These gap sizes corresponded to an experimental flow rate of 1.41E-2 N/s, 2.59E-2 N/s, 4.00E-2 N/s, and 4.44E-2 N/s, and a simulated flow rate of 1.40E-2 N/s, 2.62E-2 N/s, 4.05E-2 N/s, and 4.48E-2 N/s, respectively. Based on this experiment, Chrono::Engine had less than a 2% error in calculating the flow rate of the granular material through a slit. In addition to comparing flow rates, the pile repose angle from the experimental runs was compared to the simulation results. A description of the GPU execution model along with its memory spaces is provided to illustrate its potential for parallel scientific computing. The equations of motion associated with the dynamics of many rigid bodies are introduced and a solution method is presented. The solution method is designed to map well on the parallel hardware, which is demonstrated by an order of magnitude reductions in simulation time for large systems that concern the dynamics of granular material.

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