scholarly journals Modeling of nonstationary gas outflow at breaks of subsea gas pipelines

2021 ◽  
Vol 2119 (1) ◽  
pp. 012063
Author(s):  
A A Lukyanov ◽  
M V Alekseev
Keyword(s):  
Numerical Modeling ◽  
Turbulence Models ◽  
Vof Method ◽  
Gas Jet ◽  
Gas Bubble ◽  
Gas Pipelines ◽  
Bubble Detachment ◽  
Air Jet ◽  
Sst Model

Abstract Numerical modeling of the outflow of an air jet into water with a guillotine rupture of a pipeline by the VOF method using k-ε and k-ω SST turbulence models was carried out. The calculations were carried out in the axisymmetric approximation. The following phases of the outflow process were calculated: the formation of a large gas bubble at the place of the rupture, its growth, the separation of the bubble from the place of rupture, and the formation of a gas jet behind the bubble. It is shown that the rate of bubble detachment in the calculations by the k-ω SST model is higher than that in the calculation by the k-ε model.

scholarly journals Analysis of Flow Characteristics and Effects of Turbulence Models for the Butterfly Valve

2021 ◽  
Vol 11 (14) ◽  
pp. 6319
Author(s):  
Sung-Woong Choi ◽  
Hyoung-Seock Seo ◽  
Han-Sang Kim
Keyword(s):  
Turbulence Model ◽  
Dissipation Rate ◽  
Flow Characteristics ◽  
Turbulence Models ◽  
Flow Properties ◽  
Nominal Diameter ◽  
Large Pressure ◽  
Sst Model ◽  
Turbulence Effect ◽  
Valve Opening

In the present study, the flow characteristics of butterfly valves with different sizes DN 80 (nominal diameter: 76.2 mm), DN 262 (nominal diameter: 254 mm), DN 400 (nominal diameter: 406 mm) were numerically investigated under different valve opening percentages. Representative two-equation turbulence models of two-equation k-epsilon model of Launder and Sharma, two-equation k-omega model of Wilcox, and two-equation k-omega SST model of Menter were selected. Flow characteristics of butterfly valves were examined to determine turbulence model effects. It was determined that increasing turbulence effect could cause many discrepancies between turbulence models, especially in areas with large pressure drop and velocity increase. In addition, sensitivity analysis of flow properties was conducted to determine the effect of constants used in each turbulence model. It was observed that the most sensitive flow properties were turbulence dissipation rate (Epsilon) for the k-epsilon turbulence model and turbulence specific dissipation rate (Omega) for the k-omega turbulence model.

scholarly journals A Review of Numerical Simulations of Secondary Flows in River Bends

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 884
Author(s):  
Rawaa Shaheed ◽  
Abdolmajid Mohammadian ◽  
Xiaohui Yan
Keyword(s):  
Numerical Modeling ◽  
Numerical Simulations ◽  
Secondary Flow ◽  
Cross Section ◽  
Turbulence Models ◽  
Main Flow ◽  
Secondary Flows ◽  
River Bends ◽  
River Cross Section ◽  
River Bend

River bends are one of the common elements in most natural rivers, and secondary flow is one of the most important flow features in the bends. The secondary flow is perpendicular to the main flow and has a helical path moving towards the outer bank at the upper part of the river cross-section, and towards the inner bank at the lower part of the river cross-section. The secondary flow causes a redistribution in the main flow. Accordingly, this redistribution and sediment transport by the secondary flow may lead to the formation of a typical pattern of river bend profile. It is important to study and understand the flow pattern in order to predict the profile and the position of the bend in the river. However, there are a lack of comprehensive reviews on the advances in numerical modeling of bend secondary flow in the literature. Therefore, this study comprehensively reviews the fundamentals of secondary flow, the governing equations and boundary conditions for numerical simulations, and previous numerical studies on river bend flows. Most importantly, it reviews various numerical simulation strategies and performance of various turbulence models in simulating the flow in river bends and concludes that the main problem is finding the appropriate model for each case of turbulent flow. The present review summarizes the recent advances in numerical modeling of secondary flow and points out the key challenges, which can provide useful information for future studies.

Numerical modeling of gas-jet wiping process

2013 ◽  
Vol 68 ◽  
pp. 26-31 ◽  
Author(s):  
Konstantinos Myrillas ◽  
Patrick Rambaud ◽  
Jean-Michel Mataigne ◽  
Pascal Gardin ◽  
Stéphane Vincent ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Gas Jet

Computational Fluid Dynamics Evaluation of Heat Transfer Correlations for Sodium Flows in a Heat Exchanger

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Seok-Ki Choi ◽  
Seong-O Kim ◽  
Hoon-Ki Choi
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Turbulence Model ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Cross Flow ◽  
Turbulence Models ◽  
Parallel Flow ◽  
Sst Model ◽  
Heat Transfer Correlations

A numerical study for the evaluation of heat transfer correlations for sodium flows in a heat exchanger of a fast breeder nuclear reactor is performed. Three different types of flows such as parallel flow, cross flow, and two inclined flows are considered. Calculations are performed for these three typical flows in a heat exchanger changing turbulence models. The tested turbulence models are the shear stress transport (SST) model and the SSG-Reynolds stress turbulence model by Speziale, Sarkar, and Gaski (1991, “Modelling the Pressure-Strain Correlation of Turbulence: An Invariant Dynamical System Approach,” J. Fluid Mech., 227, pp. 245–272). The computational model for parallel flow is a flow past tubes inside a circular cylinder and those for the cross flow and inclined flows are flows past the perpendicular and inclined tube banks enclosed by a rectangular duct. The computational results show that the SST model produces the most reliable results that can distinguish the best heat transfer correlation from other correlations for the three different flows. It was also shown that the SSG-RSTM high-Reynolds number turbulence model does not deal with the low-Prandtl number effect properly when the Peclet number is small. According to the present calculations for a parallel flow, all the old correlations do not match with the present numerical solutions and a new correlation is proposed. The correlations by Dwyer (1966, “Recent Developments in Liquid-Metal Heat Transfer,” At. Energy Rev., 4, pp. 3–92) for a cross flow and its modified correlation that takes into account of flow inclination for inclined flows work best and are accurate enough to be used for the design of the heat exchanger.

scholarly journals Impact of Turbulence Models on the Air Flow in a Confined Rectangular Space

2020 ◽  
pp. 46-53
Author(s):  
Jakub Mularski ◽  
Amit Arora ◽  
Muhammad Azam Saeed ◽  
Łukasz Niedźwiecki ◽  
Samrand Saeidi
Keyword(s):  
Experimental Data ◽  
Air Flow ◽  
Turbulence Models ◽  
The Other ◽  
Experimental Measurements ◽  
Wall Region ◽  
Sst Model ◽  
Computational Fluid Dynamics Cfd ◽  
The Impact ◽  
The Given

The paper regards the impact of four different turbulence models on the air flow pattern in a confined rectangular space. The following approaches are analyzed. The Baseline (BSL) Reynolds model, the Speziale-Sarkar-Gatzki (SSG) Reynolds model, the Menter's shear-stress transport (SST) model and the basic k-ε model. Computational fluid dynamics (CFD) results are compared with the experimental measurements in four different planes. The Reynolds number for the given conditions is equal to 5000. The k-ε model yielded the most accurate results with regard to the experimental data but its reliability decreased near the wall region. With respect to the other models, it was also found that the k-ε approach generated the least circulating flow.

Enhanced surface wettability and innate activity of an iron borate catalyst for efficient oxygen evolution and gas bubble detachment

2019 ◽  
Vol 7 (25) ◽  
pp. 15252-15261 ◽  
Author(s):  
Kamran Dastafkan ◽  
Yibing Li ◽  
Yachao Zeng ◽  
Li Han ◽  
Chuan Zhao
Keyword(s):  
Oxygen Evolution ◽  
Nickel Foam ◽  
Dip Coating ◽  
Surface Wettability ◽  
Gas Bubble ◽  
Iron Borate ◽  
Bubble Detachment ◽  
Enhanced Surface

Alternating dip-coating of iron borate on nickel foam provides surface wettability towards achieving a low-adhesion oxygen evolution electrode.

Sensitization of the SST Turbulence Model to Rotation and Curvature by Applying the Spalart–Shur Correction Term

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Pavel E. Smirnov ◽  
Florian R. Menter
Keyword(s):  
Turbulent Flows ◽  
Turbulence Model ◽  
Transport Model ◽  
Correction Term ◽  
Computational Cost ◽  
Turbulence Models ◽  
Reynolds Stress Transport Model ◽  
Wide Range ◽  
Sst Model ◽  
The One

A rotation-curvature correction suggested earlier by Spalart and Shur (1997, “On the Sensitization of Turbulence Models to Rotation and Curvature,” Aerosp. Sci. Technol., 1(5), pp. 297–302) for the one-equation Spalart–Allmaras turbulence model is adapted to the shear stress transport model. This new version of the model (SST-CC) has been extensively tested on a wide range of both wall-bounded and free shear turbulent flows with system rotation and/or streamline curvature. Predictions of the SST-CC model are compared with available experimental and direct numerical simulations (DNS) data, on the one hand, and with the corresponding results of the original SST model and advanced Reynolds stress transport model (RSM), on the other hand. It is found that in terms of accuracy the proposed model significantly improves the original SST model and is quite competitive with the RSM, whereas its computational cost is significantly less than that of the RSM.

CFD Analysis of Stall in a Wells Turbine

2018 ◽  
Author(s):  
Kellis Kincaid ◽  
David W. MacPhee
Keyword(s):  
Source Code ◽  
Turbulence Models ◽  
Ocean Waves ◽  
Cfd Analysis ◽  
Oscillating Water Column ◽  
Blade Profile ◽  
Flow Conditions ◽  
Wells Turbine ◽  
Sst Model ◽  
Blade Shape

The Wells turbine is a self-rectifying device that employs a symmetrical blade profile, and is often used in conjunction with an oscillating water column to extract energy from ocean waves. The effects of solidity, angle of attack, blade shape and many other parameters have been widely studied both numerically and experimentally. To date, several 3-D numerical simulations have been performed using commercial software, mostly with steady flow conditions and employing various two-equation turbulence models. In this paper, the open source code Open-FOAM is used to numerically study the performance characteristics of a Wells turbine using a two-equation turbulence model, namely the Menter SST model, in conjunction with a transient fluid solver.

Experimental and Numerical Characterization of the Flow Around the Keel of a Yacht

2008 ◽  
Author(s):  
Renata M. B. Chaves ◽  
Atila P. S. Freire ◽  
Alexandre T. P. Alho
Keyword(s):  
Laboratory Data ◽  
Turbulence Models ◽  
Detailed Comparison ◽  
Mean Velocity ◽  
Flow Parameters ◽  
Numerical Characterization ◽  
Sst Model ◽  
Order Of Magnitude ◽  
Measured Flow ◽  
Turbulence Data

The present work carries out a detailed comparison between numerical computations for the flow around the keel and the bulb of a sailboat and some newly obtained laboratory data. Two typical turbulence models are tested: the eddy-viscosity SST model and the second-moment model BSL-RSM-ω. Hot-wire anemometry (HWA) and particle image velocimetry (PIV) are used to characterize the flow around the keel and the bulb of a yacht. The experiments are conducted in a low speed wind tunnel. Measured flow parameters include the mean velocity profiles and second order moments. Both turbulence models are shown to perform well regarding mean velocity and global predictions. Turbulence data predictions, however, are shown to be erroneous by at least one order of magnitude.

scholarly journals Gas depletion through single gas bubble diffusive growth and its effect on subsequent bubbles

2017 ◽  
Vol 831 ◽  
pp. 474-490 ◽  
Author(s):  
Álvaro Moreno Soto ◽  
Andrea Prosperetti ◽  
Detlef Lohse ◽  
Devaraj van der Meer
Keyword(s):  
Bubble Growth ◽  
Quantitative Data ◽  
Liquid Solution ◽  
Nucleation Site ◽  
Simplified Model ◽  
Gas Bubble ◽  
Dissolved Gas ◽  
Bubble Detachment ◽  
Diffusive Growth ◽  
Pure Diffusion

When a gas bubble grows by diffusion in a gas–liquid solution, it affects the distribution of gas in its surroundings. If the density of the solution is sensitive to the local amount of dissolved gas, there is the potential for the onset of natural convection, which will affect the bubble growth rate. The experimental study of the successive quasi-static growth of many bubbles from the same nucleation site described in this paper illustrates some consequences of this effect. The enhanced growth due to convection causes a local depletion of dissolved gas in the neighbourhood of each bubble beyond that due to pure diffusion. The quantitative data of sequential bubble growth provided in the paper show that the radius-versus-time curves of subsequent bubbles differ from each other due to this phenomenon. A simplified model accounting for the local depletion is able to collapse the experimental curves and to predict the progressively increasing bubble detachment times.

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