Internal Standing Waves in a Cylindrical Vessel and Their Near-Wall Features

1993 ◽  
Vol 115 (3) ◽  
pp. 613-620 ◽  
Author(s):  
S. Ushijima ◽  
S. Moriya ◽  
N. Tanaka
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Internal Wave ◽  
Turbulence Model ◽  
Standing Waves ◽  
Prediction Method ◽  
Temperature Fluctuations ◽  
Cylindrical Vessel ◽  
Experimental Investigations ◽  
Near Wall

This paper describes numerical and experimental investigations on internal standing waves occurring in a cylindrical vessel and their near-wall behavior in the vicinity of an adiabatic cylinder located at the center of the vessel. A numerical prediction method was developed with a low-Reynolds-number turbulence model to stimulate the occurrence of the internal standing waves and their near-wall features. These features are characterized by the attenuation and phase shifts in temperature fluctuations as observed in the present experiments. The measured results were well predicted by the numerical simulation in terms of certain statistical values as well as qualitative internal wave motions and flow patterns.

scholarly journals Turbulence model performance for ventilation components pressure losses

2021 ◽  
Author(s):  
Karsten Tawackolian ◽  
Martin Kriegel
Keyword(s):  
Reynolds Number ◽  
Turbulence Model ◽  
Pressure Loss ◽  
Low Reynolds Number ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Test Case ◽  
Pressure Losses ◽  
Loss Coefficients ◽  
Near Wall

AbstractThis study looks to find a suitable turbulence model for calculating pressure losses of ventilation components. In building ventilation, the most relevant Reynolds number range is between 3×104 and 6×105, depending on the duct dimensions and airflow rates. Pressure loss coefficients can increase considerably for some components at Reynolds numbers below 2×105. An initial survey of popular turbulence models was conducted for a selected test case of a bend with such a strong Reynolds number dependence. Most of the turbulence models failed in reproducing this dependence and predicted curve progressions that were too flat and only applicable for higher Reynolds numbers. Viscous effects near walls played an important role in the present simulations. In turbulence modelling, near-wall damping functions are used to account for this influence. A model that implements near-wall modelling is the lag elliptic blending k-ε model. This model gave reasonable predictions for pressure loss coefficients at lower Reynolds numbers. Another example is the low Reynolds number k-ε turbulence model of Wilcox (LRN). The modification uses damping functions and was initially developed for simulating profiles such as aircraft wings. It has not been widely used for internal flows such as air duct flows. Based on selected reference cases, the three closure coefficients of the LRN model were adapted in this work to simulate ventilation components. Improved predictions were obtained with new coefficients (LRNM model). This underlined that low Reynolds number effects are relevant in ventilation ductworks and give first insights for suitable turbulence models for this application. Both the lag elliptic blending model and the modified LRNM model predicted the pressure losses relatively well for the test case where the other tested models failed.

Numerical Simulation of Turbid-Density Current Using v2 – f Turbulence Model

2005 ◽  
Author(s):  
A. Mehdizadeh ◽  
B. Firoozabadi ◽  
B. Farhanieh
Keyword(s):  
Reynolds Number ◽  
Turbulence Model ◽  
Isotropic Turbulence ◽  
Turbidity Current ◽  
Solid Particles ◽  
Density Currents ◽  
Complex Flow ◽  
Fall Velocity ◽  
High Reynolds ◽  
Near Wall

The deposition behavior of fine sediment is an important phenomenon, and yet unclear to engineers concerned about reservoir sedimentation. An elliptic relaxation turbulence model (v2 – f model) has been used to simulate the motion of turbid density currents laden whit fine solid particles. During the last few years, the v2 – f turbulence model has become increasingly popular due to its ability to account for near-wall damping without use of damping functions. In addition, it has been proved that the v2 – f model to be superior to other RANS methods in many fluid flows where complex flow features are present. Due to low Reynolds number turbulence of turbidity current, (its critical Reynolds no. is about 1000), the κ - ε model, which was standardized for high Reynolds number and isotropic turbulence flow, cannot simulate the anisotropy and non-homogenous behavior near wall. In this study, turbidity current with uniform velocity and concentration enters the channel via a sluice gate into a lighter ambient fluid and moves forward down-slope. The model has been verified with experimental data sets. Moreover, results have been compared with the standard κ - ε turbulent model. Results show that the κ - ε model has the poor result on this current. In addition, results show that the coarse particles settle down rapidly and make the higher deposition rate. The deposition of particles and the effects of their fall velocity on concentration distribution, height of body, and entrainment coefficient are also investigated.

scholarly journals Numerical Simulation Using Near Wall K-.EPSILON. Turbulence Model for Flow in Intake Port of Automotive Engine.

1993 ◽  
Vol 59 (561) ◽  
pp. 1753-1760
Author(s):  
Shigeki Sugiura ◽  
Yoshiharu Saito ◽  
Toshio Yamada ◽  
Koji Morinishi ◽  
Nobuyuki Satofuka
Keyword(s):  
Numerical Simulation ◽  
Turbulence Model ◽  
Intake Port ◽  
Automotive Engine ◽  
Near Wall

scholarly journals Numerical simulation of flow dynamics and heat transfer in a rectangular channel with periodic ribs on one of the walls

2021 ◽  
Vol 2119 (1) ◽  
pp. 012028
Author(s):  
A V Barsukov ◽  
V V Terekhov ◽  
V I Terekhov
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Turbulence Model ◽  
Rectangular Channel ◽  
Flow Dynamics ◽  
Flat Channel ◽  
Optimal Model

Abstract The result of numerical simulation of a turbulent flow in a flat channel with a periodic transverse rib by the RANS and LES methods is presented. The Reynolds number, calculated from the rib height and the superficial velocity, is Re = 12600. The data obtained as a result of the study demonstrate the influence of the modeling method and the turbulence model on the quality of heat transfer prediction. The optimal model for this type of problems is presented.

scholarly journals Numerical simulation of the flow over a tubercled wing

2020 ◽  
Vol 307 ◽  
pp. 01036
Author(s):  
Mohammed Baghdad ◽  
Abdelkader Nehmar ◽  
Ahmed Ouadha
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Drag Coefficient ◽  
Turbulence Model ◽  
Numerical Study ◽  
Leading Edge ◽  
Governing Equations

The objective of the present study is to carry out a numerical study of the flow around a NACA0021 modified wing by the incorporation of sinusoidal tubercles on its leading edge at a Reynolds number equal to 225,000. The SST k-ω turbulence model is used as closure to the incompressible governing equations. Runs have been performed for several attack angles. Results show that for lower angles of attack, tubercles reduce the drag coefficient with a slight increase in lift.

scholarly journals Analysis of Resistance Characteristics of a 37 Rod Fuel Bundle under Low Reynolds Number

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Yonghua Li ◽  
Meijun Li ◽  
Yangyang Guo
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Turbulence Model ◽  
Low Reynolds Number ◽  
Heat Removal ◽  
Turbulence Models ◽  
Experimental Results ◽  
Liquid Sodium ◽  
Water Medium ◽  
Low Reynolds

During the working period of decay heat removal system, the flow rate of liquid sodium in wire-wrapped fuel assembly is very low, generally Re < 1000 . In the present study, both experimental methods and numerical simulation methods are applied. First, water experiment of 37-pin wire-wrapped rod bundle was carried out. Then, the numerical simulation study was carried out, the experimental data and the numerical simulation results were compared and analyzed, and a suitable turbulence model was selected to simulate the liquid sodium medium. Finally, numerical simulations under different boundary conditions were performed. Results indicate that except for the low Reynolds number k - ε turbulence model, other turbulence models have little difference with the experimental results. The results of realizable k - ε turbulence model are the most close to the experimental results. Compared with the friction factor obtained by using water medium and liquid sodium medium, the calculation results of water medium and sodium medium under the same condition are basically consistent, with the deviation within 1%. The reason is that the velocity of water is higher than sodium medium at the same Reynolds number, and the transverse disturbance caused by helical wire is larger.

scholarly journals Low Reynolds number k-ε modeling by using the direct numerical simulation (DNS) data

2008 ◽  
pp. 48-65
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Boundary Layer Flow ◽  
Low Reynolds Number ◽  
Reynolds Numbers ◽  
Damping Function ◽  
Layer Flow ◽  
Near Wall

The constant C and the near-wall damping function f in the eddyviscosityrelation of the k-ε model are evaluated from direct numerical simulation (DNS) data for developed channel and boundary-layer flow, eachat two Reynolds numbers. Various existing

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