scholarly journals Single bubble rising behaviors in Newtonian and non‐Newtonian fluids with validation of empirical correlations: A computational fluid dynamics study

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
Md. Tariqul Islam ◽  
Poo Balan Ganesan ◽  
Ji Cheng ◽  
Mohammad Salah Uddin
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Newtonian Fluids ◽  
Single Bubble ◽  
Empirical Correlations ◽  
Bubble Rising

Experimental Investigations of Single Bubble Rising in Static Newtonian Fluids as a Function of Temperature Using a Modified Drag Coefficient

2019 ◽  
Vol 29 (3) ◽  
pp. 2209-2226 ◽  
Author(s):  
Nannan Liu ◽  
Yong Yang ◽  
Jian Wang ◽  
Binshan Ju ◽  
Eric Thompson Brantson ◽  
...  
Keyword(s):  
Drag Coefficient ◽  
Newtonian Fluids ◽  
Single Bubble ◽  
Experimental Investigations ◽  
Bubble Rising

Inlet Losses in Counterflow Wet-Cooling Towers

2001 ◽  
Vol 123 (2) ◽  
pp. 460-464 ◽  
Author(s):  
E. de Villiers ◽  
D. G. Kro¨ger
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Numerical Model ◽  
Loss Coefficient ◽  
Cooling Towers ◽  
Empirical Correlations ◽  
Dependent Variables ◽  
Loss Coefficients

The inlet loss coefficients for dry, isotropically packed, circular and rectangular counterflow cooling towers are determined experimentally and empirical correlations are formulated to fit this data. Computational fluid dynamics is used to investigate the dependence of the inlet loss coefficient on the rain zone characteristics. The rain zone generally dampens the inlet loss, but the coupling is indirect and involves a large number of dependent variables. The numerical model is validated by means of experimental data for dry towers and it is found that the degree of accuracy achieved for circular towers exceeds that for rectangular towers. Consequently, the correlation derived to predict this occurrence for circular towers can be applied more confidently than its rectangular counterpart.

scholarly journals Electrokinetically Forced Turbulence in Microfluidic Flow

2018 ◽  
Author(s):  
Willy L. Duffle ◽  
Evan C. Lemley
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Experimental Data ◽  
Computational Fluid Dynamics ◽  
Newtonian Fluids ◽  
Rectangular Microchannel ◽  
Electromagnetic Simulations ◽  
Microfluidic Flow ◽  
Low Reynolds ◽  
Forced Turbulence

While laminar flow heat transfer and mixing in microfluidic geometries has been investigated experimentally, as has the effect of geometry-induced turbulence in microfluidic flow (it is well documented that turbulence increases convective heat transfer in macrofluidic flow), little literature exists investigating the effect of electrokinetically-induced turbulence on heat transfer at the micro scale. Using recently observed experimental data, this work employed computational fluid dynamics coupled with electromagnetic simulations to determine if electrokinetically-forced, low-Reynolds number turbulence could be observed in a rectangular microchannel with using Newtonian fluids. Analysis of the results was done via comparison to the experimental criteria defined for turbulent flow. This work shows that, even with a simplified simulation setup, computational fluid dynamics (CFD) software can produce results comparable to experimental observations of low-Reynolds turbulence in microchannels using Newtonian fluids. In addition to comparing simulated velocities and turbulent energies to experimental data this work also presents initial data on the effects of electrokinetic forcing on microfluidic flow based on entropy generation rates.

Support Vector Regression and Computational Fluid Dynamics Modeling of Newtonian and Non-Newtonian Fluids in Annulus With Pipe Rotation

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Mehmet Sorgun ◽  
A. Murat Ozbayoglu ◽  
M. Evren Ozbayoglu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Gradient ◽  
Support Vector Regression ◽  
Newtonian Fluids ◽  
Support Vector ◽  
Pressure Losses ◽  
Percent Error ◽  
Pipe Rotation ◽  
Absolute Percent Error

The estimation of the pressure losses inside annulus during pipe rotation is one of the main concerns in various engineering professions. Pipe rotation is a considerable parameter affecting pressure losses in annulus during drilling. In this study, pressure losses of Newtonian and non-Newtonian fluids flowing through concentric horizontal annulus are predicted using computational fluid dynamics (CFD) and support vector regression (SVR). SVR and CFD results are compared with experimental data obtained from literature. The comparisons show that CFD model could predict frictional pressure gradient with an average absolute percent error less than 3.48% for Newtonian fluids and 19.5% for non-Newtonian fluids. SVR could predict frictional pressure gradient with an average absolute percent error less than 5.09% for Newtonian fluids and 5.98% for non-Newtonian fluids.

On Deriving High Pressure Empirical Multiphase Forcing Functions From CFD Analysis

2019 ◽  
Author(s):  
Olivier Macchion ◽  
Stefan Belfroid ◽  
Leszek Stachyra ◽  
Atle Jensen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
High Pressure ◽  
Pipe Flow ◽  
Experimental Results ◽  
Internal Diameter ◽  
Cfd Analysis ◽  
Empirical Correlations ◽  
Cfd Simulations ◽  
Computational Fluid Dynamics Cfd

Abstract Computational Fluid Dynamics (CFD) simulations are used to predict the flow-induced forcing in high-pressure multiphase pipe flow. Furthermore, empirical correlations from the literature is compared and validated against computational and experimental results. Based on the CFD results and in conjunction with the reference 6” (internal diameter (ID)) data, new scaling rules are proposed.

Modeling of boilover phenomenon consequences: Computational fluid dynamics (CFD) and empirical correlations

2019 ◽  
Vol 129 ◽  
pp. 25-39 ◽  
Author(s):  
Omran Ahmadi ◽  
Seyed Bagher Mortazavi ◽  
Hadi Pasdarshahri ◽  
Hassan Asilian Mahabadi ◽  
Kazem Sarvestani
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Empirical Correlations ◽  
Computational Fluid Dynamics Cfd

Lateral Migration of Single Bubbles Due to the Presence of Wall

2002 ◽  
Author(s):  
Shigeo Hosokawa ◽  
Akio Tomiyama ◽  
Shinji Misaki ◽  
Tomoyuki Hamada
Keyword(s):  
Reynolds Number ◽  
Flat Plate ◽  
Experimental Results ◽  
Single Bubble ◽  
Force Model ◽  
Lateral Migration ◽  
Empirical Correlations ◽  
Force Coefficient ◽  
Bubble Rising ◽  
Vertical Flat Plate

Lateral migration of a single bubble rising in the vicinity of a vertical flat plate was measured to evaluate a wall force acting on the bubble. Experimental results indicated that a wall force coefficient CW3 is a function of the bubble Reynolds number Re and the Eo¨tvo¨s number Eo. Empirical correlations of CW3 were deduced for bubbles and particles. It was confirmed that the wall force model proposed by one of the authors and the proposed correlations of CW3 are applicable not only to high viscousity systems but also for low viscousity systems, provided that a bubble does not collide with the wall.

Modeling of the Fluid Flow and Heat Transfer an a Pebble Bed Modular Reactor Core With a Computational Fluid Dynamics Code

2002 ◽  
Author(s):  
J. Bryce Taylor ◽  
Savas Yavuzkurt ◽  
Anthony J. Baratta
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Future Research ◽  
Empirical Correlations ◽  
Flow And Heat Transfer

The Pebble Bed Modular Reactor (PBMR), a promising Generation IV nuclear reactor design, raises many novel technological issues for which new experience and techniques must be developed. This brief study explores a few of these issues, utilizes a computational fluid dynamics code to model some simple phenomena, and points out deficiencies in current knowledge that should be addressed by future research and experimentation. A highly simplified representation of the PBMR core is analyzed with FLUENT, a commercial computational fluid dynamics code. The applied models examine laminar and turbulent flow in the vicinity of a single spherical fuel pebble near the center of the core, accounting for the effects of the immediately adjacent fuel pebbles. Several important fluid flow and heat transfer parameters are examined, including heat transfer coefficient, Nusselt number, and pressure drop, as well as the temperature, pressure, and velocity profiles near the fuel pebble. The results of these “unit cell” calculations are also compared to empirical correlations available in the literature. As FLUENT is especially sensitive to geometry during the generation of a computational mesh, the sensitivity of code results to pebble spacing is also examined. The results of this study show that while a PBMR presents a novel and complex geometry, a code such as FLUENT is suitable for calculation of both local and global flow characteristics, and can be a valuable tool for the thermal-hydraulic study of this new reactor design. FLUENT results for pressure drop deviate from the Darcy correlation by several orders of magnitude in all cases. When determining the heat transfer coefficient, FLUENT is again much lower than Robinson’s correlation. Results for Nusselt number show better agreement, with FLUENT predicting results that are 10 or 20 times as large as those from the Robinson and Lancashire correlations. These differences may arise because the empirical correlations concern mainly integral parameters, while the FLUENT model focuses on local flow behaviors. Local phenomena are significant in the case of local heat transfer characteristics, fine temperature distribution calculations to identify hot spots, and fission product transport phenomena. All of these are important to a safety analysis of the PBMR reactor during normal operation, as well as during transient circumstances, and should be the focus of future research efforts.

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