Gas holdup and bubble size are important parameters for simulation and designing in bubble column reactors. Because based on these parameters, the available gas-liquid interfacial area is defined for mass transfer. In this paper, the results of applying magnetic fields on the velocity field and volume fraction of gas holdup are reported. Hydrodynamics of the bubble column in the reactors is inv...

We re-examine the Boussinesq hypothesis of an effective turbulent viscosity within the context of simple closure considerations for models of strong magnetohydrodynamic turbulence. Reynolds-stress and turbulent Maxwell-stress closure models will necessarily introduce a suite of transport coefficients, all of which are to some degree model-dependent. One of the most important coefficients is the...

The present paper is primarily concerned with modeling complex turbulent wall-bounded flow in spray-painting processes by using a commercial CFD code. Computational results of turbulent channel flow with low Reynolds numbers are compared with DNS data in order to obtain the performance of turbulence models and near wall treatments. The realizable k-ε model with the nonequilibrium wall function ...

Energy dissipation rate, ε, is an important parameter for nearly every experiment on turbulent flow. Mathematically precise relationships between ε and other measurable statistics for the case of anisotropic turbulence are useful to experimentalists. Such relationships are obtained for which the measurable statistics are the 3rd-order and 2nd-order velocity structure functions as well as the ac...

Flotation modelling to date appears to have concentrated either on macroscale processes or on ideal microscale processes – there has been no attempt to integrate detailed models at different scales. In this paper, bubble-particle collision efficiency with mobile bubble surfaces in a turbulent flow is investigated from a multiscale modelling viewpoint and a general methodology for modelling of t...

A thermohydrodynamic (THD) analysis of turbulent flow in journal bearings is presented based on the computational fluid dynamic (CFD) techniques. The bearing has infinite length and operates under incompressible and steady conditions. In this analysis, the numerical solution of Navier-Stokes equations with the equations governing the kinetic energy of turbulence and the dissipation rate, couple...

We present a new closure for the mean rate of stretching of a dissolved polymer by homogeneous isotropic turbulence. The polymer is modeled by a bead-spring-type model (e.g., Oldroyd B, FENE-P, Giesekus) and the analytical closure is obtained assuming the Lagrangian velocity gradient can be modeled as a Gaussian, white-noise stochastic process. The resulting closure for the mean stretching depe...

Numerical simulation of the turbulent flow around a triangular cylinder at a Reynolds number of 45,000 is presented in this paper. Both steady and unsteady vortexshedding results are presented. A body force potential model is used to model the turbulent motion. This approach is able to model non-equilibrium turbulence accurately at a cost and complexity comparable to k-ε models. The numerical m...

This 24 months research topic was an industrial driven project jointly conducted by RSAF-Defence Science & Technology Agency, NTU and Pratt & Whitney (PWA)United Technology Research Centre. The first phase was held in PWA mainly on field investigation of stall flutter in fan blades through the RSAF’s On-Job-Training Programme. The second phase was held in NTU for code development in simulation ...

Inspired by the remarkable performance of the Leray-α (and the Navier–Stokes alpha (NS-α), also known as the viscous Camassa–Holm) subgrid scale model of turbulence as a closure model to Reynolds averaged equations (RANS) for flows in turbulent channels and pipes, we introduce in this paper another subgrid scale model of turbulence, the modified Leray-α (ML-α) subgrid scale model of turbulence....