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1

Implementation of turbulence damping in the OpenFOAM multiphase flow solver interFoam

Polansky Jiri, Schmelter Sonja

Archives of Thermodynamics

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2022

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Vol. 43, no 1

21--43

EN

In the presented work Egorov’s approach (adding a source term to the ω-equation in the k-ω model, which mimics the damping of turbulence close to a solid wall) was implemented in on the subclass of shear stress transport models. Hence, turbulence damping is available for all shear stress transport type models, including hybrid models that are based on the ω-equation. It is shown that turbulence damping improves the prediction of the axial velocity profile not only for Reynolds-averaged Navier–Stokes simulation but also for detached eddy simulation and delayed detached eddy simulation models. Furthermore, it leads to a more realistic estimation of the pressure drop and, hence, to a more correct prediction of the liquid level. In this paper, simulation results for four different turbulence models are presented and validated by comparison with experimental data. Furthermore, the influence of the magnitude of the damping factor on the pressure drop in the channel is investigated for a variety of different gas-to-liquid flow rate ratios. These investigations show that higher gas-to-liquid flow rate ratios require higher damping factors to correctly predict the pressure drop. In the end, advice is formulated on how an appropriate damping factor can be determined for a specific test case.

2

Numerical simulations of linearly stratified flow past submerged bodies

Ma W., Li Y., Ding Y., Hu K., Lan L.

Polish Maritime Research

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2018

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S 3

68--77

EN

In this study, a methodology was presented to predict density stratified flows in the near-field of submerged bodies. The energy equation in temperature form was solved coupled with momentum and mass conservation equations. Linear stratification was achieved by the definition of the density as a function of temperature. At first, verifications were performed for the stratified flows passing a submerged horizontal circular cylinder, showing excellent agreement with available experimental data. The ability of the method to cope with variable density was demonstrated. Different turbulence models were used for different Re numbers and flow states. Based on the numerical methods proposed in this paper, the stratified flow was studied for the real scale benchmark DAPRA Suboff submarine. The approach used the VOF method for tracing the free surface. Turbulence was implemented with a k − ω based Detached Eddy Simulation (DES) approach. The effects of submarine speed, depth and density gradient on the free surface wave pattern were quantitatively analyzed. It was shown that, with the increasing of the speed of the submarine, the wavelength and wave height of the free surface wave were gradually increasing. The wave height of the free surface wave was gradually reduced as the submarine’s depth increased. Relative to the speed and submarine depth, the changes of the gradient density gradient have negligible effects on the free surface wave field.

3

Katabatic flow induced by a cross-slope band of surface cooling

Burkholder B.A., Shapiro A., Fedorovich E.

Acta Geophysica

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2009

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Vol. 57, no. 4

923-949

EN

This paper investigates the behavior of katabatic flow induced by an idealized, thermally inhomogeneous surface; a strip of surface cooling that has a finite width in the along-slope direction and is infinitely long in the cross-slope direction. Numerical simulations using the Boussinesq equations of motion and the thermodynamic energy equation are performed for various slope angles and strip lengths. The underlying dynamical processes in the katabatic jet and the near environment are explored by considering the along-slope momentum balance after a steady state has been achieved. The inhomogeneous nature of the surface forcing also induces a response in the environment that extends very far away from the sloped surface. Nearly horizontal jets close to the vertical heights of both sides of the cold strip are observed in the environment. A horizontal vorticity analysis is performed on these horizontal jets to ascertain their dynamical structure.

4

Gas-liquid and liquid-liquid stratified flows: exact analytical solutions and mechanistic models

Ullmann A., Goldstein A., Brauner N.

Transactions of the Institute of Fluid-Flow Machinery

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2005

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nr 117

59-79

EN

An exact analytical solution has been obtained for fully developed laminar stratified flow in inclined pipes with a plane or curved interface. This solution is of practical significance mainly for studying liquid-liquid flows. However, it is also needed as a benchmark for testing the validity of numerical methods, and for testing closure relations for two-fluid models. Two-fluid models may yield poor predictions in inclined co-current and counter-current flows. The commonly used closure relations for the wall and interfacial shear stresses do not correctly represent the fine balance between the gravity body forces and viscous shear in inclined flows. The exact solution obtained for laminar flows is used to establish and validate new closure relations, which account for the interaction between the phases and are applicable also for turbulent stratified flows.