Assessing sediment transport energetics with instrumented particles for above threshold of motion turbulent flows

2020 ◽  
Author(s):  
Zaid Al-Husban ◽  
Manousos Valyrakis
Keyword(s):  
Sediment Transport ◽  
Turbulent Flows ◽  
Particle Transport ◽  
Particle Interaction ◽  
Turbulent Channel Flow ◽  
Optimal Operation ◽  
Distribution Functions ◽  
Sensor Data ◽  
Flow Rates ◽  
Test Configuration

<p>Despite the fact sediment transport has been studied for decades, there is still a need to gain a further insight on the nature and driving mechanisms of bed particle motions induced by turbulent flows, for the low transport stages where the particle transport is relatively intermittent. A custom designed and prototyped instrumented particle, embedded with inertial sensors is used herein to study its transport over hydraulically rough bed surfaces. The calibration and error estimation for its sensors is also undertaken before starting the experiments, to ensure optimal operation and estimate any uncertainties.</p><p>The observations and results of this research are obtained from experiments carried out at the University of Glasgow 12 meters long and 0.9 meters wide, tilting and water recirculating flume. The flume walls comprise of smooth transparent glass that enables observing particle transport from the side (also with underwater video cameras) and the bed surface generally is layered with coarse gravel.</p><p>The particle is initially located at the upstream end of the test configuration, fully exposed to the uniform and fully developed turbulent channel flow. The top and side cameras are set in their suitable positions to monitor and study the behaviour of particle motion by capturing the dynamical features of sediment motion and to not interfere with flow field that pushes particle downstream.<span> </span></p><p>Using the sensor data to calculate the kinetic energy for a range of sets of sediment transport experiments with varying flow rates and particle densities, the probability distribution functions (PDFs) of particle transport features, such as particle’s total energy, are generated which give information about particle interaction with the surface bed during its motion. In addition, the effects of different flow rates, particle densities on particle energy are assessed.</p>

What Can Be Learned From LES of Particle-Laden Turbulent Flows (Invited Talk)

2002 ◽  
Author(s):  
Olivier Simonin ◽  
Kyle D. Squires
Keyword(s):  
Turbulent Flows ◽  
Broad Class ◽  
Particle Interaction ◽  
Turbulent Channel Flow ◽  
Computational Techniques ◽  
Small Particles ◽  
Two Phase Flows ◽  
Two Phase ◽  
Eddy Simulation ◽  
Large Eddy

Numerical simulation continues to evolve as an important tool in the analysis and prediction of two-phase turbulent flows. Computations are playing an increasingly important role as both a means for study of the fundamental interactions governing a process or flow, as well as forming the backbone for engineering predictions of physical systems. At a practical level, computations for engineering applications continue to rely on solution of a statistically-averaged equation set. Many of the statistical correlations requiring closure in Reynolds-averaged models are often difficult or impossible to measure in experimental investigations of two-phase flows. Computational techniques that directly resolve turbulent eddies are an important component in evaluating closure models, while at the same time offering a useful approach for basic studies of fundamental interactions. The focus of the lecture is on numerical prediction and study of turbulent two-phase flows using computational techniques such as Large Eddy Simulation (LES) that directly resolve the large, energy-containing scales of the turbulent motion. Within this broad class, the subset of two-phase flows in which a dispersed phase is comprised of small particles and is present at low volume fractions is of primary interest, using Lagrangian computational techniques for the prediction of trajectories of a large ensemble of discrete particles. The scope of such an approach considered is on systems in which the ensemble comprising the particulate phase is large enough that direct resolution of the flow in the vicinity of each particle is not feasible and, consequently, models on fluid-particle interfacial transfer and particle-particle interaction must be imposed. The focus of the lecture is on numerical prediction and study of turbulent two-phase flows using computational techniques such as Large Eddy Simulation (LES) that directly resolve the large, energy-containing scales of the turbulent motion. Within this broad class, the subset of two-phase flows in which a dispersed phase is comprised of small particles and is present at low volume fractions is of primary interest, using Lagrangian computational techniques for the prediction of trajectories of a large ensemble of discrete particles. The scope of such an approach considered is on systems in which the ensemble comprising the particulate phase is large enough that direct resolution of the flow in the vicinity of each particle is not feasible and, consequently, models on fluid-particle interfacial transfer and particle-particle interaction must be imposed. The advantages and limitations of such a technique are first considered and its accuracy is evaluated by comparison with discrete particle simulations coupled with fluid turbulence predictions obtained using DNS (understood in the present context as solution of the carrier-phase flow without the use of explicit subgrid turbulence models). An overview and examples of the application of LES to prediction and scientific study of dispersed, turbulent two-phase flows is then presented for several representative flow configurations: statistically stationary and decaying particle-laden isotropic turbulence, homogeneous shear flow, fully-developed turbulent channel flow, and turbulent particle-laden round jet. In such flows, the detailed description possible using LES enables in-depth evaluations of statistical and structural features. In particular, the role of inter-particle collision in turbulent channel flow and more recent efforts focused on exploration and analysis of the spatial structure of the particle concentration and velocity fields in homogeneous turbulence are discussed.

scholarly journals Assessing and Modelling the Interactions of Instrumented Particles with Bed Surface at Low Transport Conditions

2021 ◽  
Vol 11 (16) ◽  
pp. 7306
Author(s):  
Zaid Alhusban ◽  
Manousos Valyrakis
Keyword(s):  
Sediment Transport ◽  
Turbulent Flows ◽  
Particle Transport ◽  
Particle Density ◽  
Probability Distributions ◽  
Low Cost ◽  
Bed Load ◽  
Transport Dynamics ◽  
Field Deployment ◽  
Near Future

Sediment transport at near threshold to low transport stages (below the continuous transport) can still be affected by flow turbulence and its dynamics can benefit from further comprehensive studies. This study uses an instrumented particle embedded with micro electromechanical sensors (MEMS) to allow tracking the motions and forces acting on it, leading to and during its transport. Instrumented particle transport experiments were carried out at laboratory flume under a range of flow conditions. The probability distributions functions (PDFs) of bed load particle instantaneous velocities, hop distances and associated travel times (measured from start to stop of transport) were obtained for all the performed experiments with varying flow rates and particle density. The modelled distributions are useful and enable a deeper understanding of bed load sediment transport dynamics from a Lagrangian perspective. Furthermore, the results analyzed from the instrumented particle (including the particle’s transport mode) were validated using visual particle tracking methods (top and side cameras). The findings of this study demonstrate that for the range of turbulent flows trialed herein, the instrumented particle can be a useful, accessible, and low-cost tool for obtaining particle transport dynamics, having demonstrated satisfactory potential for field deployment in the near future.

A numerical study on combined baffles quick-separation device

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ehsan Dehdarinejad ◽  
Morteza Bayareh ◽  
Mahmud Ashrafizaadeh
Keyword(s):  
Turbulent Flows ◽  
Separation Efficiency ◽  
Numerical Study ◽  
Turbulence Models ◽  
Complete Separation ◽  
Solid Particles ◽  
Flow Rates ◽  
Separation Device ◽  
Coupling Technique ◽  
Laminar And Turbulent Flows

Abstract The transfer of particles in laminar and turbulent flows has many applications in combustion systems, biological, environmental, nanotechnology. In the present study, a Combined Baffles Quick-Separation Device (CBQSD) is simulated numerically using the Eulerian-Lagrangian method and different turbulence models of RNG k-ε, k-ω, and RSM for 1–140 μm particles. A two-way coupling technique is employed to solve the particles’ flow. The effect of inlet flow velocity, the diameter of the splitter plane, and solid particles’ flow rate on the separation efficiency of the device is examined. The results demonstrate that the RSM turbulence model provides more appropriate results compared to RNG k-ε and k-ω models. Four thousand two hundred particles with the size distribution of 1–140 µm enter the device and 3820 particles are trapped and 380 particles leave the device. The efficiency for particles with a diameter greater than 28 µm is 100%. The complete separation of 22–28 μm particles occurs for flow rates of 10–23.5 g/s, respectively. The results reveal that the separation efficiency increases by increasing the inlet velocity, the device diameter, and the diameter of the particles.

Gas Phase Cluster Formation of Sodium Chloride and Water: Monte Carlo Simulations

1991 ◽  
Vol 46 (4) ◽  
pp. 351-356
Author(s):  
Bernd M. Rode
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Cluster Formation ◽  
Ion Pairs ◽  
Particle Interaction ◽  
Distribution Functions ◽  
Prebiotic Atmosphere ◽  
Low Concentrations ◽  
Phase Cluster ◽  
Simulation Parameters

Abstract Monte Carlo simulations of a system of 200 water and 24 NaCl molecules at 6 different densities in the range from 0.003 g/cm3 to 0.999 g,/cm3 and T = 125 °C and 225 CC were performed to obtain some insight into cluster formation which should precede and determine the formation of aerosol structures and has possibly played some role in prebiotic atmosphere chemistry. Solute hydration occurs already at very low concentrations mainly in the form of hydrated molecules ("contact ion pairs"). At higher densities larger cluster structures are observed, leading rather continuously to the structure of the supersaturated 7.1 M NaCl solution at the same temperature. Radial distribution functions, coordination numbers and particle interaction energies are discussed with respect to the simulation parameters density and temperature

Exploring probability distribution functions best-fitting the kinetic energy of coarse particles at above threshold flow conditions

2021 ◽  
Author(s):  
Hamed Farhadi ◽  
Manousos Valyrakis
Keyword(s):  
Probability Distribution ◽  
Kinetic Energy ◽  
Test Section ◽  
Particle Transport ◽  
River Flow ◽  
Distribution Functions ◽  
Transport Processes ◽  
Flow Conditions ◽  
Probability Distribution Functions ◽  
Transport Regime

<p>Applying an instrumented particle [1-3], the probability density functions of kinetic energy of a coarse particle (at different solid densities) mobilised over a range of above threshold flow conditions conditions corresponding to the intermittent transport regime, were explored. The experiments were conducted in the Water Engineering Lab at the University of Glasgow on a tilting recirculating flume with 800 (length) × 90 (width) cm dimension. Twelve different flow conditions corresponding to intermittent transport regime for the range of particle densities examined herein, have been implemented in this research. Ensuring fully developed flow conditions, the start of the test section was located at 3.2 meters upstream of the flume outlet. The bed surface of the flume is flat and made up of well-packed glass beads of 16.2 mm diameter, offering a uniform roughness over which the instrumented particle is transported. MEMS sensors are embedded within the instrumented particle with 3-axis gyroscope and 3-axis accelerometer. At the beginning of each experimental run, instrumented particle is placed at the upstream of the test section, fully exposed to the free stream flow. Its motion is recorded with top and side cameras to enable a deeper understanding of particle transport processes. Using results from sets of instrumented particle transport experiments with varying flow rates and particle densities, the probability distribution functions (PDFs) of the instrumented particles kinetic energy, were generated. The best-fitted PDFs were selected by applying the Kolmogorov-Smirnov test and the results were discussed considering the light of the recent literature of the particle velocity distributions.</p><p>[1] Valyrakis, M.; Alexakis, A. Development of a “smart-pebble” for tracking sediment transport. In Proceedings of the International Conference on Fluvial Hydraulics (River Flow 2016), St. Louis, MO, USA, 12–15 July 2016.</p><p>[2] Al-Obaidi, K., Xu, Y. & Valyrakis, M. 2020, The Design and Calibration of Instrumented Particles for Assessing Water Infrastructure Hazards, Journal of Sensors and Actuator Networks, vol. 9, no. 3, 36.</p><p>[3] Al-Obaidi, K. & Valyrakis, M. 2020, Asensory instrumented particle for environmental monitoring applications: development and calibration, IEEE sensors journal (accepted).</p>

Can Bump Arrays Separate Particles From Turbulent Flows?

2021 ◽  
Author(s):  
Leonard F. Pease ◽  
Jason Serkowski ◽  
Timothy G. Veldman ◽  
Jonathan Willams ◽  
Xiao-Ying Yu ◽  
...  
Keyword(s):  
Turbulent Flows ◽  
Particle Separation ◽  
Reynolds Numbers ◽  
Industrial Scale ◽  
Flow Rates ◽  
Scale Particle ◽  
Experimental Findings

Abstract In this paper, we evaluate the hypothesis that bump arrays can be used to separate particles from turbulent flows entering the array. Microfluidic bump arrays are known for separating particles by size from laminar inlet flows. However, turbulent inlet flows have not been explored but become important as microfluidic bump arrays are scaled up to mesofluidic bump arrays. We find experimentally that particle separation is indeed effective at higher Reynolds numbers. These experimental findings portend industrial scale particle separation due to the higher flow rates they facilitate.

Direct numerical simulation of turbulent channel flow up to

2015 ◽  
Vol 774 ◽  
pp. 395-415 ◽  
Author(s):  
Myoungkyu Lee ◽  
Robert D. Moser
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Turbulent Flows ◽  
Channel Flow ◽  
Turbulent Channel Flow ◽  
Streamwise Velocity ◽  
Mean Velocity ◽  
Layer Structures ◽  
High Reynolds

A direct numerical simulation of incompressible channel flow at a friction Reynolds number ($\mathit{Re}_{{\it\tau}}$) of 5186 has been performed, and the flow exhibits a number of the characteristics of high-Reynolds-number wall-bounded turbulent flows. For example, a region where the mean velocity has a logarithmic variation is observed, with von Kármán constant ${\it\kappa}=0.384\pm 0.004$. There is also a logarithmic dependence of the variance of the spanwise velocity component, though not the streamwise component. A distinct separation of scales exists between the large outer-layer structures and small inner-layer structures. At intermediate distances from the wall, the one-dimensional spectrum of the streamwise velocity fluctuation in both the streamwise and spanwise directions exhibits $k^{-1}$ dependence over a short range in wavenumber $(k)$. Further, consistent with previous experimental observations, when these spectra are multiplied by $k$ (premultiplied spectra), they have a bimodal structure with local peaks located at wavenumbers on either side of the $k^{-1}$ range.

scholarly journals Ion-driven Instabilities in the Inner Heliosphere. I. Statistical Trends

2021 ◽  
Vol 923 (1) ◽  
pp. 116
Author(s):  
Mihailo M. Martinović ◽  
Kristopher G. Klein ◽  
Tereza Ďurovcová ◽  
Benjamin L. Alterman
Keyword(s):  
Solar Wind ◽  
Particle Interaction ◽  
Radial Distance ◽  
Solar Wind Plasma ◽  
Distribution Functions ◽  
Nyquist Criterion ◽  
Velocity Distribution Functions ◽  
Instability Growth ◽  
Statistical Trends ◽  
The Impact

Abstract Instabilities described by linear theory characterize an important form of wave–particle interaction in the solar wind. We diagnose unstable behavior of solar wind plasma between 0.3 and 1 au via the Nyquist criterion, applying it to fits of ∼1.5M proton and α particle Velocity Distribution Functions (VDFs) observed by Helios I and II. The variation of the fraction of unstable intervals with radial distance from the Sun is linear, signaling a gradual decline in the activity of unstable modes. When calculated as functions of the solar wind velocity and Coulomb number, we obtain more extreme, exponential trends in the regions where collisions appear to have a notable influence on the VDF. Instability growth rates demonstrate similar behavior, and significantly decrease with Coulomb number. We find that for a nonnegligible fraction of observations, the proton beam or secondary component might not be detected, due to instrument resolution limitations, and demonstrate that the impact of this issue does not affect the main conclusions of this work.

Sign in / Sign up

Export Citation Format

Share Document