Abstract
Bubbly flow still represents a challenge for large-scale numerical simulation. Among many others, the understanding and modelling of bubble-induced turbulence (BIT) are far from being satisfactory even though continuous efforts have been made. In particular, the buoyancy of the bubbles generally introduces turbulence anisotropy in the flow, which cannot be captured by the standard eddy viscosity models with specific source terms representing BIT. Recently, on the basis of bubble-resolving direct numerical simulation data, a new Reynolds-stress model considering BIT was developed by Ma et al. (J Fluid Mech, 883: A9 (2020)) within the Euler—Euler framework. The objective of the present work is to assess this model and compare its performance with other standard Reynolds-stress models using a systematic test strategy. We select the experimental data in the BIT-dominated range and find that the new model leads to major improvements in the prediction of full Reynolds-stress components.
Highlights
Bubble-laden turbulent flows occur in a large number of processes in the energy generation, chemical industry, and nature (Lohse, 2018)
We select the experimental data in the bubble-induced turbulence (BIT)-dominated range and find that the new model leads to major improvements in the prediction of full Reynolds-stress components
A full Reynolds-stress model recently proposed by Ma et al (2020b) based on the budget analysis of the Reynolds stress and its dispersion from direct numerical simulation (DNS) for bubbly flows is tested rigorously for a large number of bubbly flows
Summary
The experiment of Deen et al (2001) has been simulated very accurately in terms of averaged liquid statistics by using different kinds of scale-resolving simulations without considering any BIT effect (Deen et al., 2001; Ničeno et al, 2008; Ma et al, 2015a; Ullrich et al, 2021) In these cited references, they show that compared to BIT the undulatory modulation of bubble plume is the dominant effect in such a flow, generating the most velocity fluctuations. Attempts in this category, e.g., Lopez de Bertodano et al (1990) combined the RSM of Launder et al (1975) (LRR for short) with the BIT expression by Biesheuvel and van Wijngaarden (1984) as a source tensor to capture the turbulence generated by bubbles This algebraic BIT expression is derived by using the assumption of a potential flow and considers the liquid velocity fluctuations influenced by the moving bubbles primarily from the displacement of the liquid.
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