Experimental and theoretical analyses of two-dimensional flows upstream of broad-crested weirs

2008 ◽  
Vol 35 (9) ◽  
pp. 975-986 ◽  
Author(s):  
M. Salih Kirkgoz ◽  
M. Sami Akoz ◽  
A. Alper Oner
Keyword(s):  
Cfd Simulation ◽  
Turbulence Models ◽  
Free Surface Flows ◽  
Velocity Fields ◽  
Numerical Results ◽  
Cfd Modeling ◽  
Two Dimensional ◽  
The Finite Element Method ◽  
Image Velocimetry ◽  
Computational Fluid Dynamics Cfd

Using the particle image velocimetry (PIV) technique, the laboratory experiments are conducted to measure the velocity fields of two-dimensional turbulent free surface flows upstream of rectangular and triangular broad-crested weirs. The experimental flow cases are analyzed theoretically by a computational fluid dynamics (CFD) modeling in which the finite element method is used to solve the governing equations. In the CFD simulation, the volume of fluid (VOF) method is used to compute the free surfaces of the flows. Using the standard k–ε and standard k–ω turbulence models, the numerical results for the velocity fields and flow profiles are compared with the experimental results for validation purposes. The computed results using k–ω turbulence model on compressed mesh systems are found in good agreement with measured data. The flow cases are also analyzed theoretically using the potential flow (PF) approach, and the numerical results for the velocity fields are compared with measurements.

scholarly journals Biomagnetic Monitoring vs. CFD Modeling: A Real Case Study of Near-Source Depositions of Traffic-Related Particulate Matter along a Motorway

Atmosphere ◽  
2020 ◽  
Vol 11 (12) ◽  
pp. 1285
Author(s):  
Sarah Letaïef ◽  
Pierre Camps ◽  
Thierry Poidras ◽  
Patrick Nicol ◽  
Delphine Bosch ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Particulate Matter ◽  
Cfd Simulation ◽  
Low Cost ◽  
Precast Concrete ◽  
Cfd Modeling ◽  
Concrete Wall ◽  
Fluorescence Measurements ◽  
Computational Fluid Dynamics Cfd

A test site located along a 12-lane motorway east of Montpellier, France, is used to evaluate the potential of biomagnetic monitoring on traffic-related particulate matter (PM) to parametrize a computational fluid dynamics (CFD) simulation of the local airflow. Two configurations were established on the site with three vegetated flat-top earth berms of a basic design, and a fourth one was located windward to the traffic roofed with a 4-m-high precast concrete wall. As a first step, PM deposition simultaneously on plant leaves, on low-cost passive artificial filters, and on soils was estimated from proxies supplied by magnetic and X-ray fluorescence measurements on both sides of the motorway. These latter revealed that traffic-related pollutants are present on soils samples highlighted with a clear fingerprint of combustion residues, and wears of breaks, vehicles, and highway equipment. Maximum PM accumulations were detected in the lee of the berm–wall combination, while no significant deposition was observed on both sides of the flat-top earth berms. These results are in line with measurements from PM µ-sensors operated by the regional state-approved air quality agency. Finally, we compared the experimental measurements with the outcomes of a computational fluid dynamics (CFD) modeling based on the Reynolds-Averaged Navier–Stokes (RANS) equations that consider the traffic-induced momentum and turbulence. The CFD modeling matches the experimental results by predicting a recirculated flow in the near wake of the berm–wall combination that enhances the PM concentration, whereas the flat-top berm geometry does not alter the pollutants’ transport and indeed contributes to their atmospheric dispersion.

Technique for Adequate CFD-Modeling of the Pump With Hydro-Drive of the Low-Pressure Stage

2016 ◽  
Author(s):  
Vasilii M. Zubanov ◽  
Leonid S. Shabliy ◽  
Alexander V. Krivcov ◽  
Valeriy N. Matveev
Keyword(s):  
Rotational Speed ◽  
Cfd Simulation ◽  
Turbulence Models ◽  
Pressure Head ◽  
Low Pressure ◽  
Inlet Pressure ◽  
Cfd Modeling ◽  
Future Research ◽  
Rotor Speed ◽  
Pressure Stage

This article describes the technique for CFD-modeling of a powerful two-stage pump with the following main parameters: main rotor speed is 13,300 rpm, inlet pressure is 0.2 MPa, pressure head is more than 3,000 meters with mass flow of 250 kg/s. The main feature of investigated pump is the hydro-drive of the low-pressure stage of turbine with variable rotational speed. There are two highlights in this work in comparison with the previous ones. The first one is how to choose the rotating speed of hydro-turbine. The second one is the CFD-modeling of cavitation processes. The core part of proposed technique is the determination of rotational speed during CFD-simulation by special methodology. Another feature is the cavitation modeling to be sure that there is no cavitation in pre-pump at quite low inlet pressure and variable rotor speed. Also, recommendations about program tools (ANSYS CFX, NUMECA AutoGrid5, ANSYS ICEM CFD) are a significant part of the discussed technique, as well as modeling features (fluid domain restriction, meshing, turbulence models choosing, convergence checking, post-processing). The adequacy of CFD-model was evaluated by comparing predicted characteristics of the pump with the experimental ones derived from the test rig. The differences amounted to less than 10%. The obtained technique can be used in the future research for performance improving and efficiency increasing of pumps with hydro-drive of the low-pressure stage by CFD-tools.

scholarly journals Performance Investigation of The Bed Adsorption of An Adsorption Desalination Using CFD Simulation

2021 ◽  
Author(s):  
Mohamad Hossein Bakhshandeh ◽  
Taleb Zarei ◽  
Jamshid Khorshidi
Keyword(s):  
Silica Gel ◽  
Water Uptake ◽  
Cfd Simulation ◽  
Finned Tube ◽  
Copper Plate ◽  
Cfd Modeling ◽  
Desorption Process ◽  
Critical Elements ◽  
Computational Fluid Dynamics Cfd ◽  
Fin Thickness

Abstract One of the critical elements of an adsorption desalination system is the adsorption bed. System dynamics of a 2-bed single-stage silica gel plus water-based AD system was analyzed. A great pattern is expanded using energy conservation and mass connected with the kinetics of the ad- sorption/desorption process. Computational fluid dynamics (CFD) modeling was handled for simulation of the adsorption process for a rectangular finned tube-based adsorption bed featured with silica gel adsorbent substance. For the simulation, the adsorbents were considered as a solid volume with defined porosity based on Darcy equation. The adsorption and desorption mode of the adsorption bed was simulated. The CFD techniques were then applied to study fin thickness and fin height. The results showed that decreasing the fin thickness increased the water uptake by up to 8% and decreased the fin height from 30mm to 20mm, which resulted in an increase of the water uptake up to 17%. The CFD technique was also used to investigate the effect of plate type on the adsorption bed performance. The results showed that the copper plate improved the water uptake up to 9%. The copper plate decreased the temperature of the adsorption bed up to 11% more than the aluminum plate.

Investigation of Streaming Flow Patterns in a Thermoacoustic Device Using PIV

2010 ◽  
Author(s):  
Hadi Babaei ◽  
Kamran Siddiqui
Keyword(s):  
Particle Image ◽  
Velocity Fields ◽  
Two Dimensional ◽  
Cold Side ◽  
Velocity Magnitude ◽  
Piv Technique ◽  
Image Velocimetry ◽  
Streaming Velocity ◽  
The Difference ◽  
Streaming Flow

We report on an experimental study conducted to study the streaming velocity fields in the vicinity of the stack in a thermoacoustic device. Synchronized Particle Image Velocimetry (PIV) technique was used to measure the two-dimensional streaming velocity fields. The streaming velocity fields were measured at both sides of the porous stack over a range of pressure amplitudes (drive ratios). The results show that the streaming flow structure is significantly different on hot and cold sides of the stack. The hot side of the stack experienced higher magnitudes and higher spatial variability of the streaming velocities compared to the cold side. The difference in the velocity magnitude between the hot and cold sides of the stack showed a significant increase with an increase in the drive ratio.

Capability Assessment of Five Different RANS-Based Turbulence Models to Simulate the Various Regions of Slot Turbulent Impingement Jet Flow

2017 ◽  
Author(s):  
Mahmoud Charmiyan ◽  
Ahmed-Reza Azimian ◽  
Ebrahim Shirani ◽  
Fethi Aloui
Keyword(s):  
Experimental Data ◽  
Turbulence Models ◽  
Jet Flows ◽  
Two Dimensional ◽  
Mean Flow ◽  
Impingement Jet ◽  
Image Velocimetry ◽  
The Mean ◽  
Bottom To Top ◽  
Plate Distance

In this paper, impingement of a turbulent rectangular flow to a fixed wall is investigated. The jet flows from bottom-to-top and the output jet Reynolds is 16000. The nozzle-to-plate distance is equal to 10 (H/e = 10). Five turbulence models, including k-ε, RNG k-ε, k-ω SST, RSM and v2f model have been used for two-dimensional numerical simulation of the turbulent flow. Because of the complexities of the impingement flow, such as curved streamlines, flow separation, normal strains and sudden deceleration in different areas, different turbulence models are proposed to simulate different regions of the flow. To investigate the capability of these turbulence models in simulating different regions of the impinging jet, the mean flow velocity field and turbulent kinetic energy are extracted and compared with the experimental data of a two-dimensional particle image velocimetry (PIV). The calculated error of these five turbulence models was presented for the various flow regions, while it have not been clearly investigated earlier. Results indicate the highest conformity of the v2f model with the experimental data at the jet centerline. However, this model does not predict well the flow at the shear layer and wall-jet areas. RSM Gibson and Lander model has the highest conformity with the experimental data in these regions.

CFD Simulation of 5×5 Rod Bundles With Split-Type Spacers

2013 ◽  
Author(s):  
K. Podila ◽  
J. Bailey ◽  
Y. F. Rao ◽  
M. Krause
Keyword(s):  
Cfd Simulation ◽  
Turbulence Models ◽  
Reynolds Stress Model ◽  
Atomic Energy ◽  
Rod Bundles ◽  
Spacer Grid ◽  
Two Phase ◽  
Ansys Fluent ◽  
Computational Fluid Dynamics Cfd ◽  
Canada Limited

Atomic Energy of Canada Limited (AECL) has initiated a program to develop Computational Fluid Dynamics (CFD) capability for simulating single- and two-phase flows in rod-bundles. In the current work, a 5×5 rod assembly with a split-type spacer grid is simulated with ANSYS Fluent 14 using unsteady simulations with a fully conformal hybrid mesh (wall y+∼30). This work represents results of AECL’s recent participation in the OECD/NEA organized CFD benchmarking exercise on the MATiS-H experiment performed at the Korean Atomic Energy Research Institute (KAERI). The sensitivity to turbulence models is tested using the standard k-ε and the Reynolds stress model (RSM). Reasonable agreement is achieved between the calculated and experimental velocity values in the region close to the spacer grid, whereas turbulence intensity values are underpredicted compared to the experiments.

scholarly journals Two-Dimensional CFD Modeling of Hysteresis Behavior of MR Dampers

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Pengfei Guo ◽  
Jing Xie
Keyword(s):  
Mr Damper ◽  
Cfd Modeling ◽  
Two Dimensional ◽  
The Finite Element Method ◽  
One Dimensional ◽  
Hysteresis Behavior ◽  
Mr Dampers ◽  
Nonlinear Hysteresis ◽  
Mr Fluids ◽  
Dimensional Modeling

So far, most previous studies on the nonlinear hysteresis analysis of ER/MR dampers have been limited to one-dimensional modeling techniques. A two-dimensional (2D) axisymmetric CFD model of MR dampers is developed in this work. The main advantage of the proposed 2D model of MR dampers lies in that it can be used to predict dynamic behavior of MR devices of arbitrary geometries. The compressibility of MR fluids is the main factor responsible for the hysteresis behavior of MR dampers, and it has been rarely investigated in previous multidimensional modeling of MR damper. In our model, the compressibility of MR fluids is taken into account by the two-dimensional constitutive model which is extended from a previous one-dimensional physical model. The model is solved by using the finite element method, and the movement of the piston is described by the moving mesh technique. The MR damper in a reference is simulated, and the model predictions show good agreement with the experimental data in the reference.

Numerical Investigation on the Stirred Reactor with Rushton Turbine

2014 ◽  
Vol 881-883 ◽  
pp. 1823-1826
Author(s):  
Li Dai ◽  
Li Bin Yang ◽  
Kai Liu
Keyword(s):  
Cfd Simulation ◽  
Numerical Results ◽  
Turbulent Model ◽  
Rushton Turbine ◽  
Design And Optimization ◽  
Flow Prediction ◽  
Stirred Reactor ◽  
Discretization Schemes ◽  
Flow Information ◽  
Computational Fluid Dynamics Cfd

Computational Fluid Dynamics (CFD) simulation is expected to give detailed flow information which is important for stirred reactor design and optimization, however accurate flow prediction remains a challenge for CFD application. In the present paper, influence of discretization scheme on the flow prediction in a stirred reactor with Rushton turbine was investigated. Standardk-εturbulent model and MRF model was adopted and numerical results obtained by using three different discretization schemes were compared. Results showed that the numerical results agreed well with data provided in literature. It is acceptable to use any discreticaiton method if aiming at a general flow field, while QUICK is recommended considering the more detailed flow information.

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