One-equation sub-grid scale (SGS) modelling for Euler-Euler large eddy simulation (EELES) of dispersed bubbly flow

In this work, we have presented a one-equation model for sub-grid scale (SGS) kinetic energy and applied it for an Euler-Euler large eddy simulation (EELES) of a bubble column reactor. The one-equation model for SGS kinetic energy shows improved predictions over the state-of-the-art dynamic procedure. With grid refinement, the amount of modelled SGS turbulent kinetic energy diminishes, as one would expect. Bubble induced turbulence (BIT) at the SGS level was modelled with two approaches. In the first approach an algebraic model was used, while in the other approach extra source terms were added in the transport equation for SGS kinetic energy. It was found that the latter approach improved the quantitative prediction of the turbulent kinetic energy. To the best of authors knowledge, this is the first use of a transport equation for SGS kinetic energy in bubbly flows

Reviews on drag reducing polymers

Polymers are effective drag reducers owing to their ability to suppress the formation of turbulent eddies at low concentrations. Existing drag reduction methods can be generally classified into additive and non-additive techniques. The polymer additive based method is categorized under additive techniques. Other drag reducing additives are fibers and surfactants. Non-additive techniques are associated with the applications of different types of surfaces: riblets, dimples, oscillating walls, compliant surfaces and microbubbles. This review focuses on experimental and computational fluid dynamics (CFD) modeling studies on polymer-induced drag reduction in turbulent regimes. Other drag reduction methods are briefly addressed and compared to polymer-induced drag reduction. This paper also reports on the effects of polymer additives on the heat transfer performances in laminar regime. Knowledge gaps and potential research areas are identified. It is envisaged that polymer additives may be a promising solution in addressing the current limitations of nanofluid heat transfer applications