Validation of AIAD Sub-Models for Advanced Numerical Modelling of Horizontal Two-Phase Flows

Abstract

<jats:p>In this work, the modelling of horizontal two-phase flows within the two-fluid Euler–Euler approach is investigated. A modified formulation of the morphology detection functions within the Algebraic Interfacial Area Density (AIAD) model is presented in combination with different models for the drag force acting on a sheared gas–liquid interface. In the case of free surface flows, those closure laws are often based on experimental correlations whose applicability is limited to certain flow regimes. It is investigated here whether the implementation of the modified blending functions in ANSYS CFX avoids this limitation. The influence of the new functions on the prediction of turbulence parameters in free surface flows is also examined quantitatively for the k-ω and k-ε two-equation turbulence models. Transient simulations of the WENKA counter-current stratified two-phase flow experiment were performed for validation. A prediction of the correct flow pattern as observed in the experiment improved dramatically when a turbulence damping term was included in the standard two-equation models. Using the k-ω and a modified k-ε turbulence model with damping terms close to the interface, better agreement with the experimental data was achieved. The morphology detection mechanism of the unified blending functions within the AIAD is seen as an improvement with respect to the detection of sharp interfaces. Satisfactory quantitative agreement is achieved for the modified free surface drag. Furthermore, it is demonstrated that turbulence dampening has to be accounted for in both turbulence models to qualitatively reproduce the mean flow and turbulence quantities from the experiment.</jats:p>

Numerical Modelling of Horizontal Oil-Water Pipe Flow

“…The results with AIAD clearly presents a more realistic behavior clearly showing the waves produced at the interface. The small wave turbulence at the interface between the two phases are achieved in AIAD by considering turbulence damping and sub-grid wave turbulence [12]. This behavior cannot be captured in the case without AIAD (Figure 17).…”

“…The AIAD model allows the recognition of the flow morphology and the consistent switching of arbitrary closure relations. It has already been described by Höhne et al [12], so only a brief description is given here.…”

“…A grid study was performed based on experiences with similar pipes/channels for horizontal two-phase flow modelling [1,12] and the proper mesh resolution was selected. The mesh is based on a block-structured hexahedral grid (O-Grid) generated by ICEM CFD to give accurate results as well as to achieve the convergence of the solution as quickly as possible.…”

Modelling of Reactive and Non-Reactive Multiphase Flows

“…The Special Issue "Modelling of Reactive and Non-Reactive Multiphase Flows" collects 11 papers covering a broad range of topics dealing with applications of non-reactive [1][2][3][4][5][6] and reactive [7][8][9][10][11] multiphase flows in natural environment as well as technical applications. The contributions address important numerical and modelling issues, which not only cover fundamental physics but also address the aspect of application.…”

“…Horizontal two-phase flows are common in nature, such as the movement of water droplets in the air or the formation of waves on water surfaces, but they also occur in industrial processes, for example, in wave-like flows in pressurized water reactors. Their modelling and experimental characterization have been addressed by Höhne et al [3] and Carraretto et al [4]. The modelling [3] has been performed within the two-fluid Euler-Euler approach.…”