scholarly journals NUMERICAL MODELING OF THE DISTRIBUTION OF SNOW LOAD ON A HYPERBOLIC PARABOLOID. THEORETICAL BASIS

2021 ◽  
pp. 43-51
Author(s):  
M.G. Surianinov ◽  
◽  
S. Jgalli ◽  
Al Echcheikh El Alaoui Douaa ◽  
◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Mixture Model ◽  
Two Phase Flow ◽  
Complex Geometry ◽  
Computational Cost ◽  
Phase Flow ◽  
Hyperbolic Paraboloid ◽  
Two Phase ◽  
Ansys Fluent ◽  
Euler Model

Abstract. The paper discusses the choice of a method for studying the distribution of snow loads on a biconcave roof of a hyperbolic paraboloid and its theoretical justification. It is noted that the numerical modeling of the aerodynamic characteristics of buildings and structures is a difficult and resource-intensive task due to the design features of building objects, which, as a rule, have a complex geometric shape, as well as due to a complex unsteady flow resulting from their flow around them. In addition, the task becomes more complicated due to the interference of vortex structures between different objects. Overcoming these objective difficulties became possible with the advent of modern specialized software systems, primarily ANSYS Fluent. Opportunities have appeared for accurate modeling with verification of the results obtained, which implies the use of an effective, well-tested mathematical apparatus. To implement the theory of two-phase flow, two methods based on numerical modeling are mainly used: the Euler-Lagrange method and the Euler-Euler method. The second method is used in the work. Comparative analysis, which investigates two-phase flow around different structures using different turbulence models (including RSM model, SST k-ω model, k-ε model and k-kl-ω model), shows that the k-kl-ω model is the best fit with experiment. ANSYS Fluent supports four multiphase models, i.e. VOF model, Mixture model, Wet Steam and Euler model. Compared to the other three models, the Mixture model provides better stability and lower computational costs, while the Euler model provides better accuracy, but at a higher computational cost . With a rather complex geometry and flow conditions, the use of the RANS approach does not lead to reliable simulation results. Moreover, unsteady turbulent flows cannot be reproduced. In real situations, landslides, saltations, and the suspended state of snow particles are closely related to the real effects of microbursts and bursts present at the surface of the boundary layer. Therefore, in further research, it is advisable to apply alternative approaches to RANS, which include Direct Numerical Simulation (DNS), Large Eddy Simulation (LES), and the hybrid RANS-LES approach to turbulence modeling, which combine efficiency LES techniques in tear-off free zones and the cost-effectiveness of RANS in near-wall areas.

Simulation of Two Phase Flow Dynamics in Flexible Riser Exit Geometries for Oil and Gas Applications

2018 ◽  
Vol 39 ◽  
pp. 1-13
Author(s):  
Ikpe E. Aniekan ◽  
Owunna Ikechukwu ◽  
Satope Paul
Keyword(s):  
Oil And Gas ◽  
Two Phase Flow ◽  
Flow Analysis ◽  
Computational Cost ◽  
Maximum Velocity ◽  
Oil Well ◽  
Phase Flow ◽  
Two Phase ◽  
The Third ◽  
Riser Pipe

Four different riser pipe exit configurations were modelled and the flow across them analysed using STAR CCM+ CFD codes. The analysis was limited to exit configurations because of the length to diameter ratio of riser pipes and the limitations of CFD codes available. Two phase flow analysis of the flow through each of the exit configurations was attempted. The various parameters required for detailed study of the flow were computed. The maximum velocity within the pipe in a two phase flow were determined to 3.42 m/s for an 8 (eight) inch riser pipe. After thorough analysis of the two phase flow regime in each of the individual exit configurations, the third and the fourth exit configurations were seen to have flow properties that ensures easy flow within the production system as well as ensure lower computational cost. Convergence (Iterations), total pressure, static pressure, velocity and pressure drop were used as criteria matrix for selecting ideal riser exit geometry, and the third exit geometry was adjudged the ideal exit geometry of all the geometries. The flow in the third riser exit configuration was modelled as a two phase flow. From the results of the two phase flow analysis, it was concluded that the third riser configuration be used in industrial applications to ensure free flow of crude oil and gas from the oil well during oil production.

scholarly journals Numerical Prediction of Two-Phase Flow in Tube Bundles with a CFD Porous Media Approach Based on Mixture Model and a Void Fraction Correlation

2021 ◽  
Vol 321 ◽  
pp. 01002
Author(s):  
Claire Dubot ◽  
Vincent Melot ◽  
Claudine Béghein ◽  
Cyrille Allery ◽  
Clément Bonneau
Keyword(s):  
Porous Media ◽  
Mixture Model ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Numerical Prediction ◽  
Phase Flow ◽  
Two Phase ◽  
Mixture Density ◽  
Tube Bundles ◽  
Phase Mixture

Being able to predict the void fraction is essential for a numerical prediction of the thermohydraulic behaviour in steam generators. Indeed, it determines two-phase mixture density and affects two-phase mixture velocity which enable to evaluate the pressure drop of heat exchanger, the mass transfer and heat transfer coefficients. In this study, the flow is modelled by coupling Ansys Fluent with an in-house code library where a CFD porous media approach is implemented. In this code, the two-phase flow has been modelled so far using the Eulerian model. However, this two-phase model requires interaction laws between phases which are not known and/or reliable for a flow within a tube bundle. The aim of this paper is to use the mixture model, for which it is easier to implement suitable correlations for tube bundles. By expressing the relative velocity, as a function of slip, the void fraction model of Feenstra et al. developed for upward cross-flow through horizontal tube bundles is introduced. With this method, physical phenomena that occur in tube bundles are taken into consideration in the mixture model. The developed approach is validated based on the experimental results obtained by Dowlati et al.

scholarly journals Simulation of Stratified Two-phase Flow Regime using Air-Water Model in ANSYS Fluent ®

2019 ◽  
Vol 1355 ◽  
pp. 012014
Author(s):  
Binet Monachan ◽  
Rijo J. Thomas ◽  
Deepak Steaphen ◽  
Mathew Skaria ◽  
K.A. Shafi
Keyword(s):  
Flow Regime ◽  
Two Phase Flow ◽  
Water Model ◽  
Phase Flow ◽  
Two Phase ◽  
Ansys Fluent

scholarly journals Prediction of two-phase flow through a safety relief valve

2012 ◽  
Vol 227 (1) ◽  
pp. 42-55 ◽  
Author(s):  
Wael Elmayyah ◽  
William Dempster
Keyword(s):  
Mixture Model ◽  
Equilibrium Model ◽  
Two Phase Flow ◽  
Turbulent Transport ◽  
Valve Lift ◽  
Phase Flow ◽  
Atmospheric Conditions ◽  
Relief Valve ◽  
Two Phase ◽  
Air Mass

Safety relief valves are necessary elements in any pressurised system. The flow inside the safety relief valve shows a number of interesting, yet complicated, features especially when a two-phase flow is involved. Consequently, developing an efficient and accurate means for predicting the safety relief valve performance and understanding the flow physics is a demanding objective. In this article, the ability of a two-phase mixture model to predict the critical flows of air and water through a safety valve is examined. An industrial refrigeration safety relief valve of ¼” inlet bore size has been tested experimentally over a pressure range of 6–15 barg and air mass qualities from 0.23 to 1 when discharging to near atmospheric conditions for a range of valve lift positions. A two-dimensional mixture model consisting of mixture mass, momentum and energy equations, combined with a liquid mass equation and the standard k-e turbulence model for mixture turbulent transport has been used to predict the two-phase flows though the valve. The mixture model results have been compared with the homogenous equilibrium model and the homogenous non-equilibrium model adopted by the ISO standard. It has been shown that the mixture model can be used satisfactorily to predict the mass flows for the above conditions. Overall, the accuracy of the two-phase air mass flow for given inlet liquid flow rates can be predicted to within 15%.

scholarly journals Numerical Modeling of Turbulent Swirling Two-Phase Flow in a Centrifugal Classifier

2016 ◽  
Vol 110 ◽  
pp. 01070
Author(s):  
Alexander Shvab ◽  
Pavel Zyatikov ◽  
Marina Goyko
Keyword(s):  
Numerical Modeling ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase

Well-posed Euler model of shock-induced two-phase flow in bubbly liquid

Shock Waves ◽  
2017 ◽  
Vol 28 (2) ◽  
pp. 253-266 ◽  
Author(s):  
R. R. Tukhvatullina ◽  
S. M. Frolov
Keyword(s):  
Two Phase Flow ◽  
Bubbly Liquid ◽  
Phase Flow ◽  
Two Phase ◽  
Euler Model ◽  
Well Posed

Numerical Modeling of Two Phase Flow under Centrifugation

2012 ◽  
Vol 326-328 ◽  
pp. 221-226
Author(s):  
Jozef Kačur ◽  
Benny Malengier ◽  
Pavol Kišon
Keyword(s):  
Inverse Problem ◽  
Numerical Modeling ◽  
Numerical Experiments ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Saturated Sample ◽  
Dae Systems ◽  
Capillary Pressure Curves ◽  
Wetting Liquid

Numerical modeling of two-phase flow under centrifugation is presented in 1D.A new method is analysed to determine capillary-pressure curves. This method is based onmodeling the interface between the zone containing only wetting liquid and the zone containingwetting and non wetting liquids. This interface appears when into a fully saturated sample withwetting liquid we inject a non-wetting liquid. By means of this interface an efficient and correctnumerical approximation is created based upon the solution of ODE and DAE systems. Bothliquids are assumed to be immiscible and incompressible. This method is a good candidate tobe used in solution of inverse problem. Some numerical experiments are presented.

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