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Stein Tore Johansen - One of the best experts on this subject based on the ideXlab platform.

  • on the validity of the two fluid ktgf approach for dense gravity driven granular flows as implemented in Ansys Fluent r17 2
    2020
    Co-Authors: Alexander Busch, Stein Tore Johansen
    Abstract:

    Abstract As a subproblem of solid transport in wellbores, we have investigated the cliff collapse problem by means of the Two-Fluid-Model (TFM), where the rheological description of the second phase (sand) is governed by the Kinetic Theory of Granular Flows (KTGF) and additional closures from soil mechanics for dense (frictional) regions of the solid phase. Using Ansys Fluent R17.2, we have studied the influence of the aspect ratio and scale of the initial cliff, the scale of the particle size, four different interstitial fluids (air, water, and two viscous but shear-thinning solutions), and the role of the initial condition (IC) of the solid volume fraction. The latter was evaluated by two different strategies: (1) Let solids settle to establish a compacted granular bed in dynamic equilibrium prior to allow the cliff to collapse and (2) simply patch the solid volume fraction into the computational domain at t = 0. While most of the simulations produced a final deposit featuring a slope, validation with experimentally obtained scaling laws from the literature was not comprehensively successful. The primary reason identified is that, at steady-state, for which a sloped deposit must exist, a thin layer at the top of the sediment bed remains flowing, yielding a scale-dependent disintegration of the cliff over longer periods of time which ultimately results in a flat bed. We suspect this phenomenon, hereafter termed top bed velocity defect, to be a consequence of the numerical solutions strategy of Fluent which may result in some momentum solid flux imbalance at top-bed regions where the gradient of the solids kinetic/collisional pressure is high. Comprehensive model tuning is required to yield a better physical representation of the IC. In addition, alternative closures for both solid frictional pressure and solid viscosity may be helpful to better replicate the experimental data. On the other hand, experimental spread and missing experimental data for the shear-thinning fluids requires more comprehensive experimental data for validation purposes. If the model in its current form is used for transport modeling of cuttings in wellbore flows, the velocity defect will lead to an unknown overestimation of the mass flux of solids. When it comes to the modeling of dune migration, the top bed velocity defect will likely cause disintegration of the dune over longer periods of time.

  • implementation demonstration and validation of a user defined wall function for direct precipitation fouling in Ansys Fluent
    2017
    Co-Authors: Sverre Gullikstad Johnsen, Tiina Paakkonen, Stein Tore Johansen, Riitta L Keiski, Bernd Wittgens
    Abstract:

    In a previous paper (Johnsen et al., 2015) and presentation (Johnsen et al., 2016), we developed and demonstrated a generic modelling framework for the modelling of direct precipitation fouling from multi-component fluid mixtures that become super-saturated at the wall. The modelling concept involves the 1-dimensional transport of the fluid species through the turbulent boundary layer close to the wall. The governing equations include the Reynolds-averaged (RANS) advection-diffusion equations for each fluid species, and the axial momentum and energy equations for the fluid mixture. The driving force for the diffusive transport is the local gradient in the species' chemical potential. Adsorption mechanisms are not modelled per se, but the time-scale of adsorption is reflected in the choice of Dirichlet boundary conditions for the depositing species, at the fluid-solid interface. In this paper, the modelling framework is implemented as a user-defined function (UDF) for the CFD software Ansys Fluent, to act as a wall boundary condition for mass-transfer to the wall. The subgrid, 1-dimensional formulation of the model reduces the computational cost associated with resolving the fine length-scales at which the boundary-layer mass transfer is determined, and allows for efficient modelling of industry-scale heat exchangers suffering from fouling. The current paper describes the modelling framework, and demonstrates and validates its applicability in a simplified 2D heat exchanger geometry (experimental and detailed CFD modelling data by P\"a\"akk\"onen et al. (2012, 2016)). By tuning the diffusivity, only, good agreement with the experimental data and the detailed CFD model was obtained, in terms of area-averaged deposition rates.

Sergei Sazhin - One of the best experts on this subject based on the ideXlab platform.

  • a model for heating and evaporation of a droplet cloud and its implementation into Ansys Fluent
    2018
    Co-Authors: Oyuna Rybdylova, Timur Zaripov, Sergei Sazhin
    Abstract:

    Abstract A model for heating and evaporation of a cloud of monocomponent droplets in air, taking into account the evolution of droplet number densities, is developed and implemented into Ansys Fluent. Functionality testing of the new customised version of Ansys Fluent is based on its application to the analysis of a droplet cloud in a two-phase back-step flow. It is shown that the effect of the droplet cloud needs to be taken into account when estimating the heat and mass transfer rates from the carrier phase to the droplets.

  • a model for multi component droplet heating and evaporation and its implementation into Ansys Fluent
    2018
    Co-Authors: Oyuna Rybdylova, Al M Qubeissi, Cyril Crua, Luke Poulton, Ahmed Elwardany, T Khan, Sergei Sazhin
    Abstract:

    Abstract The main ideas of the model for multi-component droplet heating and evaporation, based on the analytical solutions to the heat conduction and species diffusion equations in the liquid phase, and its implementation into Ansys Fluent CFD software are described. The model is implemented into this software via User-Defined Functions (UDF). The predictions of Ansys Fluent with the newly implemented model are verified against the results predicted by the previously developed in-house research code for droplets comprising of a mixture of ethanol and acetone evaporating and cooled down in ambient air.

  • a model for mono and multi component droplet heating and evaporation and its implementation into Ansys Fluent
    2017
    Co-Authors: Luke Poulton, Oyuna Rybdylova, Sergei Sazhin, Cyril Crua, Mansour Al Qubeissi, Ahmed Elwardany
    Abstract:

    A model for heating and evaporation of mono- and multi-component droplets, based on analytical solutions to the heat transfer and species diffusion equations in the liquid phase, is summarised. The implementation of the model into Ansys Fluent via User-Defined Functions (UDF) is described. The model is applied to the analysis of pure acetone, ethanol, and mixtures of acetone/ethanol droplet heating/cooling and evaporation. The predictions of the customised version of Ansys Fluent with the newly implemented UDF model are verified against the results predicted by the previously developed in house, one-dimensional code. DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4759

  • the fully lagrangian approach to the analysis of particle droplet dynamics implementation into Ansys Fluent and application to gasoline sprays
    2017
    Co-Authors: Timur Zaripov, Oyuna Rybdylova, Sergei Sazhin, A K Gilfanov, Steven Begg, Morgan Heikal
    Abstract:

    The fully Lagrangian approach (FLA) to the calculation of the number density of inertial particles in dilute gas-particle flows is implemented into the CFD code Ansys Fluent. The new version of Ansys Fluent is applied to modeling dilute gas-particle flow around a cylinder and liquid droplets in a gasoline fuel spray. In a steady-state case, the predictions of the FLA for the flow around a cylinder and those based on the equilibrium Eulerian method (EE) are almost identical for small Stokes number, Stk, and small Reynolds number, Re, (Re = 1, Stk = 0.05). For the larger values of these numbers (Re = 10, 100; Stk = 0.1, 0.2) the FLA predicts higher values of the gradients of particle number densities in front of the cylinder compared with the ones predicted by the EE. For transient flows (Re = 200), both methods predict high values of the number densities between the regions of high vorticity and very low values in the vortex cores. For Stk ≥ 0.1 the maximal values predicted by FLA are shown to be several orders of magnitude higher than those predicted by the EE. An application of FLA to a direct injection gasoline fuel spray has focused on the calculation of the number densities of droplets. Results show good qualitative agreement between the numerical simulation and experimental observations. It is shown that small droplets with diameters dp = 2 μm tend to accumulate in the regions of trajectory intersections more readily, when compared with larger droplets (dp = 10 μm, dp = 20 μm). This leads to the prediction of the regions of high number densities of small droplets.

  • a model for droplet heating and its implementation into Ansys Fluent
    2016
    Co-Authors: Oyuna Rybdylova, Al M Qubeissi, G De Sercey, Elena Sazhina, Cyril Crua, Julien Manin, Lyle M Pickett, M. Braun, Sergei Sazhin
    Abstract:

    The main ideas of the model for droplet heating and evaporation, based on the analytical solution to the heat conduction equation inside the droplet, and its implementation into Ansys Fluent are described. The model is implemented into Ansys Fluent using User-Defined Functions (UDF). The predictions of Ansys Fluent with the new model are verified against the results predicted by in-house research code for an n-dodecane droplet heated and evaporated in hot air. Also, the predictions of this version of Ansys Fluent are compared with in-house experimental data.

Oyuna Rybdylova - One of the best experts on this subject based on the ideXlab platform.

  • a model for heating and evaporation of a droplet cloud and its implementation into Ansys Fluent
    2018
    Co-Authors: Oyuna Rybdylova, Timur Zaripov, Sergei Sazhin
    Abstract:

    Abstract A model for heating and evaporation of a cloud of monocomponent droplets in air, taking into account the evolution of droplet number densities, is developed and implemented into Ansys Fluent. Functionality testing of the new customised version of Ansys Fluent is based on its application to the analysis of a droplet cloud in a two-phase back-step flow. It is shown that the effect of the droplet cloud needs to be taken into account when estimating the heat and mass transfer rates from the carrier phase to the droplets.

  • a model for multi component droplet heating and evaporation and its implementation into Ansys Fluent
    2018
    Co-Authors: Oyuna Rybdylova, Al M Qubeissi, Cyril Crua, Luke Poulton, Ahmed Elwardany, T Khan, Sergei Sazhin
    Abstract:

    Abstract The main ideas of the model for multi-component droplet heating and evaporation, based on the analytical solutions to the heat conduction and species diffusion equations in the liquid phase, and its implementation into Ansys Fluent CFD software are described. The model is implemented into this software via User-Defined Functions (UDF). The predictions of Ansys Fluent with the newly implemented model are verified against the results predicted by the previously developed in-house research code for droplets comprising of a mixture of ethanol and acetone evaporating and cooled down in ambient air.

  • a model for mono and multi component droplet heating and evaporation and its implementation into Ansys Fluent
    2017
    Co-Authors: Luke Poulton, Oyuna Rybdylova, Sergei Sazhin, Cyril Crua, Mansour Al Qubeissi, Ahmed Elwardany
    Abstract:

    A model for heating and evaporation of mono- and multi-component droplets, based on analytical solutions to the heat transfer and species diffusion equations in the liquid phase, is summarised. The implementation of the model into Ansys Fluent via User-Defined Functions (UDF) is described. The model is applied to the analysis of pure acetone, ethanol, and mixtures of acetone/ethanol droplet heating/cooling and evaporation. The predictions of the customised version of Ansys Fluent with the newly implemented UDF model are verified against the results predicted by the previously developed in house, one-dimensional code. DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4759

  • the fully lagrangian approach to the analysis of particle droplet dynamics implementation into Ansys Fluent and application to gasoline sprays
    2017
    Co-Authors: Timur Zaripov, Oyuna Rybdylova, Sergei Sazhin, A K Gilfanov, Steven Begg, Morgan Heikal
    Abstract:

    The fully Lagrangian approach (FLA) to the calculation of the number density of inertial particles in dilute gas-particle flows is implemented into the CFD code Ansys Fluent. The new version of Ansys Fluent is applied to modeling dilute gas-particle flow around a cylinder and liquid droplets in a gasoline fuel spray. In a steady-state case, the predictions of the FLA for the flow around a cylinder and those based on the equilibrium Eulerian method (EE) are almost identical for small Stokes number, Stk, and small Reynolds number, Re, (Re = 1, Stk = 0.05). For the larger values of these numbers (Re = 10, 100; Stk = 0.1, 0.2) the FLA predicts higher values of the gradients of particle number densities in front of the cylinder compared with the ones predicted by the EE. For transient flows (Re = 200), both methods predict high values of the number densities between the regions of high vorticity and very low values in the vortex cores. For Stk ≥ 0.1 the maximal values predicted by FLA are shown to be several orders of magnitude higher than those predicted by the EE. An application of FLA to a direct injection gasoline fuel spray has focused on the calculation of the number densities of droplets. Results show good qualitative agreement between the numerical simulation and experimental observations. It is shown that small droplets with diameters dp = 2 μm tend to accumulate in the regions of trajectory intersections more readily, when compared with larger droplets (dp = 10 μm, dp = 20 μm). This leads to the prediction of the regions of high number densities of small droplets.

  • a model for droplet heating and its implementation into Ansys Fluent
    2016
    Co-Authors: Oyuna Rybdylova, Al M Qubeissi, G De Sercey, Elena Sazhina, Cyril Crua, Julien Manin, Lyle M Pickett, M. Braun, Sergei Sazhin
    Abstract:

    The main ideas of the model for droplet heating and evaporation, based on the analytical solution to the heat conduction equation inside the droplet, and its implementation into Ansys Fluent are described. The model is implemented into Ansys Fluent using User-Defined Functions (UDF). The predictions of Ansys Fluent with the new model are verified against the results predicted by in-house research code for an n-dodecane droplet heated and evaporated in hot air. Also, the predictions of this version of Ansys Fluent are compared with in-house experimental data.

Al M Qubeissi - One of the best experts on this subject based on the ideXlab platform.

  • a model for multi component droplet heating and evaporation and its implementation into Ansys Fluent
    2018
    Co-Authors: Oyuna Rybdylova, Al M Qubeissi, Cyril Crua, Luke Poulton, Ahmed Elwardany, T Khan, Sergei Sazhin
    Abstract:

    Abstract The main ideas of the model for multi-component droplet heating and evaporation, based on the analytical solutions to the heat conduction and species diffusion equations in the liquid phase, and its implementation into Ansys Fluent CFD software are described. The model is implemented into this software via User-Defined Functions (UDF). The predictions of Ansys Fluent with the newly implemented model are verified against the results predicted by the previously developed in-house research code for droplets comprising of a mixture of ethanol and acetone evaporating and cooled down in ambient air.

  • a model for droplet heating and its implementation into Ansys Fluent
    2016
    Co-Authors: Oyuna Rybdylova, Al M Qubeissi, G De Sercey, Elena Sazhina, Cyril Crua, Julien Manin, Lyle M Pickett, M. Braun, Sergei Sazhin
    Abstract:

    The main ideas of the model for droplet heating and evaporation, based on the analytical solution to the heat conduction equation inside the droplet, and its implementation into Ansys Fluent are described. The model is implemented into Ansys Fluent using User-Defined Functions (UDF). The predictions of Ansys Fluent with the new model are verified against the results predicted by in-house research code for an n-dodecane droplet heated and evaporated in hot air. Also, the predictions of this version of Ansys Fluent are compared with in-house experimental data.

Timur Zaripov - One of the best experts on this subject based on the ideXlab platform.

  • a model for heating and evaporation of a droplet cloud and its implementation into Ansys Fluent
    2018
    Co-Authors: Oyuna Rybdylova, Timur Zaripov, Sergei Sazhin
    Abstract:

    Abstract A model for heating and evaporation of a cloud of monocomponent droplets in air, taking into account the evolution of droplet number densities, is developed and implemented into Ansys Fluent. Functionality testing of the new customised version of Ansys Fluent is based on its application to the analysis of a droplet cloud in a two-phase back-step flow. It is shown that the effect of the droplet cloud needs to be taken into account when estimating the heat and mass transfer rates from the carrier phase to the droplets.

  • the fully lagrangian approach to the analysis of particle droplet dynamics implementation into Ansys Fluent and application to gasoline sprays
    2017
    Co-Authors: Timur Zaripov, Oyuna Rybdylova, Sergei Sazhin, A K Gilfanov, Steven Begg, Morgan Heikal
    Abstract:

    The fully Lagrangian approach (FLA) to the calculation of the number density of inertial particles in dilute gas-particle flows is implemented into the CFD code Ansys Fluent. The new version of Ansys Fluent is applied to modeling dilute gas-particle flow around a cylinder and liquid droplets in a gasoline fuel spray. In a steady-state case, the predictions of the FLA for the flow around a cylinder and those based on the equilibrium Eulerian method (EE) are almost identical for small Stokes number, Stk, and small Reynolds number, Re, (Re = 1, Stk = 0.05). For the larger values of these numbers (Re = 10, 100; Stk = 0.1, 0.2) the FLA predicts higher values of the gradients of particle number densities in front of the cylinder compared with the ones predicted by the EE. For transient flows (Re = 200), both methods predict high values of the number densities between the regions of high vorticity and very low values in the vortex cores. For Stk ≥ 0.1 the maximal values predicted by FLA are shown to be several orders of magnitude higher than those predicted by the EE. An application of FLA to a direct injection gasoline fuel spray has focused on the calculation of the number densities of droplets. Results show good qualitative agreement between the numerical simulation and experimental observations. It is shown that small droplets with diameters dp = 2 μm tend to accumulate in the regions of trajectory intersections more readily, when compared with larger droplets (dp = 10 μm, dp = 20 μm). This leads to the prediction of the regions of high number densities of small droplets.