Numerical Study of Turbulent Flows Through a Circular Duct With a Rotating Fan

2009 ◽  
Author(s):  
Gaurav Rajwade ◽  
Jie Cui
Keyword(s):  
Turbulent Flows ◽  
Numerical Study ◽  
Pressure Rise ◽  
Flow Conditions ◽  
Circular Duct ◽  
Flow Information ◽  
Computational Fluid Dynamics Cfd ◽  
Air Circulation ◽  
The Relationship ◽  
Good Agreement

A fan is an important part for air circulation in household appliances and automobiles. In this research an attempt has been made to extract the flow information using the Computational Fluid Dynamics (CFD) technique. The numerical results were found for a case with a stationary fan inside the duct and the data obtained were in good agreement with the experiment. The evolution of velocity profiles at various axial locations for different flow conditions were also studied in this research. The numerical method was then extended to the cases with a rotating fan. A proof-of-concept run was also successfully carried out to showe the relationship between air flow rate in the duct and the corresponding pressure rise.

A Numerical Study for the Relationship between Natural Manganese Dendrites and DLA Patterns

2016 ◽  
Vol 71 (3) ◽  
pp. 225-234
Author(s):  
Tugba Ozbey ◽  
Mehmet Bayirli
Keyword(s):  
Critical Exponent ◽  
Numerical Study ◽  
Formation Mechanisms ◽  
Diffusion Limited Aggregation ◽  
Density Correlation ◽  
Diffusion Limited ◽  
Crystalline Anisotropy ◽  
The Relationship ◽  
Good Agreement ◽  
Dla Model

AbstractThe formation mechanisms and the origin of manganese dendrites on the magnesite ore have been under discussion. The growth process of the manganese dendrites is statistically studied by comparing them to aggregations obtained according to the diffusion limited aggregation (DLA) model via Monte Carlo simulations. In this case, ten manganese dendrite patterns changing from the least dense to the densest aggregations on the surface are separately selected to determine the relationship between real and simulated patterns. The sticking parameter is ranged from 0.05≤t≤1. The density–density correlation functions C(r) (their critical exponent A), fractal dimension Df, critical exponent α, and critical exponent β pertaining to the root mean square (rms) thickness have been computed for both the ten manganese dendrites and the simulated aggregations representing them. The results indicate that manganese dendrites may be determined with the general DLA model. Analyses of manganese dendrites, both scaling and simulations, suggest the growth mechanism for the macroscopic expression of crystalline anisotropy for the dendritic patterns. These results are in good agreement with the values in other literature and can be helpful in comparing natural and simulated aggregations (both dendritic and compact deposits).

An Experimental and Numerical Study of Pressure Drop and Hydraulic Behavior in Scaled-Down Fuel Bundle

2013 ◽  
Vol 275-277 ◽  
pp. 409-412
Author(s):  
Duen Sheng Lee ◽  
Kai Ting Hsieh ◽  
Po Chih Tsao ◽  
Tzu Chen Hung ◽  
Yi Tung Chen ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Numerical Study ◽  
Spent Fuel ◽  
Rod Bundles ◽  
Cfd Simulations ◽  
Fuel Bundle ◽  
Acceptable Deviation ◽  
Spent Fuel Pool ◽  
Computational Fluid Dynamics Cfd ◽  
The Relationship

This study presents a scaled-down single fuel assembly experiment to simulate the fuel in the spent fuel pool (SFP). From experiment results, this study obtained the relationship among pressure drop and velocity, the viscous resistance and inertial resistance factor. In computational fluid dynamics (CFD) simulations, the large number of fuel rod bundles is approximated with porous medium technique that imposes similar flow resistance to the motion of the fluid. Difference of the pressure drop between numerical and experimental results is within acceptable deviation.

The Effect of Silencers of the Helmholtz-Resonator Type on Pressure Waves of Finite Amplitude: Single Pressure Pulses

1974 ◽  
Vol 16 (4) ◽  
pp. 268-275 ◽  
Author(s):  
G. H. Trengrouse
Keyword(s):  
Incident Wave ◽  
Helmholtz Resonator ◽  
Single Pulse ◽  
Finite Amplitude ◽  
Pressure Waves ◽  
Flow Conditions ◽  
Partial Reflection ◽  
One Dimensional ◽  
The Relationship ◽  
Good Agreement

The attenuation of large-amplitude waves effected by silencers of the so-called Helmholtz-resonator type is envisaged as being due to the finite efflux of gas through the holes of the silencer with resulting partial reflection, and hence reduced transmission, of the incident wave. Quasi-steady, one-dimensional flow arguments are used to predict the attenuation, the flow conditions being assumed reversible and adiabatic, that is, isentropic. This latter assumption is avoided in an alternative method by assuming a knowledge of the relationship between pipe Mach numbers and the pressure difference in the pipe across the holes. Indicator diagrams resulting from single pulse experiments are, in general, in good agreement with those predicted.

Computation of Three-Dimensional Turbulent Flows in a Pipe Junction with Reference to Engine Inlet Manifolds

1992 ◽  
Vol 206 (4) ◽  
pp. 285-296 ◽  
Author(s):  
H Fu ◽  
M J Tindal ◽  
A P Watkins ◽  
M Yianneskis
Keyword(s):  
Turbulent Flows ◽  
Combustion Engine ◽  
Laser Doppler Anemometry ◽  
Numerical Study ◽  
Three Dimensional ◽  
Turbulence Energy ◽  
Numerical Predictions ◽  
Split Ratio ◽  
Inlet Manifold ◽  
Good Agreement

This paper presents a numerical study of the flows in an internal combustion engine inlet manifold. The three-dimensional turbulent flows through a single branched manifold were simulated using the κ-ɛ model of turbulence. The flow structure was characterized in detail and the effects of the flow split ratio and inlet flowrate were investigated. Detailed measurements were performed to validate the numerical predictions, using laser Doppler anemometry. Good agreement was obtained between the predicted and the measured mean velocities. The predicted levels of turbulence energy are in qualitative agreement with the measurements.

A Numerical Study of Laminar and Intermittently Turbulent Boundary Layer on an Oscillating Flat Plate Using Pseudo-Compressible RANS Model

2020 ◽  
Author(s):  
Shivank Srivastava ◽  
Brandon M. Taravella ◽  
Kazim M. Akyuzlu
Keyword(s):  
Boundary Layer ◽  
Turbulent Flow ◽  
Flat Plate ◽  
Turbulent Flows ◽  
Numerical Study ◽  
Navier Stokes ◽  
Flow Conditions ◽  
Rans Model ◽  
Explicit Finite Difference ◽  
Turbulent Flow Conditions

Abstract A numerical study was conducted to study the unsteady characteristics of incompressible boundary layer flows over an oscillating flat plate under laminar and intermittently turbulent flow conditions using pseudo-compressible Reynolds Averaged Navier-Stokes (RANS) model. The numerical study is carried out using an in-house code and a commercial CFD package (Fluent). Two equation (k-ε) turbulence closure model, modified near the wall, is used along with RANS equations to simulate intermittently turbulent flows. Fully Explicit-Finite Difference technique (FEFD) is employed to solve the governing differential equations. For validation purposes, the velocity fields predicted by the in-house code and commercial CFD package are compared to the one given by analytical solution to Stokes’ second problem for an oscillating flat plate. Numerical experiments were conducted for unsteady cases for Stokes’ Reynolds number corresponding to laminar and intermittently turbulent flows, respectively. Time dependent velocity profiles, shear stress distribution, turbulence properties during the accelerating and decelerating stages of oscillations are predicted. The above predictions are then compared to ones predicted by commercial CFD code. The velocity magnitudes predicted by the in-house code and commercial CFD code are within acceptable range for laminar and intermittently turbulent flow conditions.

Control strategy optimization for a dual-clutch transmission downshift with a single slipping clutch during the torque phase

2017 ◽  
Vol 232 (5) ◽  
pp. 651-666 ◽  
Author(s):  
Jikai Liu ◽  
Biao Ma ◽  
Heyan Li ◽  
Man Chen ◽  
Guoqiang Li
Keyword(s):  
Control Strategy ◽  
Power Flow ◽  
Control Strategies ◽  
Poor Quality ◽  
Dual Clutch Transmission ◽  
Flow Conditions ◽  
Robust Controller ◽  
Simulation Results ◽  
The Relationship ◽  
Good Agreement

During the torque phase, appropriate coordination between two clutches is of vital importance to the dual-clutch transmission so that a high-quality shift is achieved without clutch interaction and engine flare, because a poor-quality shift definitely extends the shift time and increases the friction work. Concerning this problem, two different power flow conditions during the torque phase are discussed in detail, after investigation of the dual-clutch transmission downshift process and the design of an H∞ robust controller for the inertia phase. The results obtained indicate that, if two clutches are slipping simultaneously during the torque phase, either power interruption or power circulation occurs. Thus, by optimizing the relationship between the two clutches, a novel control strategy is proposed for the dual-clutch transmission so that the downshift process is accomplished with only one slipping clutch, in order to obtain the highest system efficiency. The system model was established on the MATLAB/Simulink platform and used to study the variations in the torque and the speed output in response to different control strategies. The simulation results show that, with the smooth inertia phase guaranteed by the robust controller, the proposed control strategy not only can avoid power interruption or power circulation during the torque phase but also can shorten the shift time (from 1.1 s to 0.8 s) and reduce the jerk level (from 6.8 m/s3 to 5.7 m/s3) effectively, in comparison with the conventional control strategy. Finally, to validate the effectiveness of the proposed control strategy, bench tests on a dual-clutch transmission were carried out, and the test data obtained show good agreement with the simulation results.

CFD Predictions and Experiments of Erosion of Elbows in Series in Liquid Dominated Flows

2018 ◽  
Author(s):  
Thiana A. Sedrez ◽  
Yeshwanth R. Rajkumar ◽  
Siamack A. Shirazi ◽  
Hadi Arabnejad Khanouki ◽  
Brenton S. McLaury
Keyword(s):  
Solid Particle Erosion ◽  
Flow Conditions ◽  
Erosion Modeling ◽  
Cfd Simulations ◽  
Horizontal Orientation ◽  
In Series ◽  
Computational Fluid Dynamics Cfd ◽  
Sand Flow ◽  
Pattern Visualization ◽  
Good Agreement

Most previous studies of solid particle erosion in elbows considered an elbow for which the upstream length is long (L/D>100) and flow is well developed before reaching the elbow. But, in this study, experiments were conducted for two elbows in series, one in vertical upward-horizontal orientation and the second one placed after L/D = 6 in horizontal-vertical downward orientation. Erosion experiments were conducted with liquid-sand and liquid-gas-sand flow conditions in an experimental facility with two test section configurations: metallic elbows in series for erosion measurements and acrylic elbows in series for erosion pattern visualization. The experiments include erosion measurements of both metallic elbows with ultrasonic wall thickness (UT) measurements. All experiments including flow visualization of erosion pattern were conducted for both elbows for liquid dominated flows, and the results comparing the erosion ratio of the second elbow to the first elbow are presented. In addition, Computational Fluid Dynamics (CFD) simulations have been performed and compared to the experimental erosion patterns with both erosion pattern visualization and UT measurements. The results show good agreement between experiments and CFD simulations and experimental results provide a database for improving erosion modeling in liquid dominated flows.

Performance Analysis of Centrifugal Compressor under Different Operation Conditions

2015 ◽  
Vol 779 ◽  
pp. 133-140
Author(s):  
Yu Liang Lu ◽  
Yun Feng Zhao ◽  
Bo Liang
Keyword(s):  
Centrifugal Compressor ◽  
Load Distribution ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Operation Conditions ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Domain ◽  
The Relationship ◽  
Good Agreement

Centrifugal compressor in bootstrap turbine cooler was studied to build computational model of flow domain for compressor component. The relationship between pressure ratio πc, efficiency ηc, flow rate G and rotational speed N was calculated by 3D numerical method. Experimental data were compared with the calculated results and good agreement was achieved. It indicated that performance characteristics of centrifugal compressor under off-Design condition could be predicted by computational fluid dynamics (CFD) technology. Furthermore, internal flow characteristics and load distribution could be visualized directly by CFD post processing graph.

Numerical Study of Liquid-Liquid Vertical Dispersed Flows

2012 ◽  
Author(s):  
Kofi Freeman K. Adane ◽  
Syed Imran A. Shah ◽  
R. Sean Sanders
Keyword(s):  
Turbulent Flows ◽  
Volume Fraction ◽  
Numerical Study ◽  
Continuous Phase ◽  
Numerical Results ◽  
Mean Velocity ◽  
Ansys Cfx ◽  
Oil In Water ◽  
Dispersed Flows ◽  
Good Agreement

Numerical simulations of liquid-liquid dispersed flow in a vertical pipe (38mm) have been carried out using the two-fluid approach implemented in a commercial CFD code, ANSYS CFX. A dispersion of oil in water (where water is the continuous phase) was studied. Both fluids were considered as turbulent flows. The k-ε model was used for the continuous phase, with the eddy viscosity of the dispersed phase estimated from that of the continuous phase. A comparison of the present numerical results with previous experimental and numerical results in terms of volume fraction, mean velocity and turbulent kinetic energy is discussed. In general, good agreement between the simulation results and experimental measurements was observed.

The Effect of Stratification Ratio on the Macrostructure of Stratified Swirl Flames: Experimental and Numerical Study

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Xiao Han ◽  
Davide Laera ◽  
Aimee S. Morgans ◽  
Yuzhen Lin ◽  
Chih-Jen Sung
Keyword(s):  
Numerical Study ◽  
Large Eddy Simulations ◽  
Flame Dynamics ◽  
Large Eddy ◽  
Swirling Flame ◽  
Computational Fluid Dynamics Cfd ◽  
Different Shapes ◽  
Flame Quenching ◽  
Simulation Results ◽  
Good Agreement

The present paper reports experimental and numerical analyses of the macrostructures featured by a stratified swirling flame for varying stratification ratio (SR). The studies are performed with the Beihang Axial Swirler Independently Stratified (BASIS) burner, a novel double-swirled full-scale burner developed at Beihang University. Experimentally, it is found that depending on the ratio between the equivalence ratios of the methane–air mixtures from the two swirlers, the flame stabilizes with three different shapes: attached V-flame, attached stratified flame, and lifted flame. In order to better understand the mechanisms leading to the three macrostructures, large eddy simulations (LES) are performed via the open-source computational fluid dynamics (CFD) software OpenFOAM using the incompressible solver ReactingFoam. Changing SR, simulation results show good agreement with experimentally observed time-averaged flame shapes, demonstrating that the incompressible LES are able to fully characterize the different flame behaviors observed in stratified burners. When the LES account for heat loss from walls, they better capture the experimentally observed flame quenching in the outer shear layer (OSL). Finally, insights into the flame dynamics are provided by analyzing probes located near the two separate streams.

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