Turbulence modulation in particle-laden flow, especially the influence of vortex shedding, was investigated by means of the direct numerical simulation. To this end, we developed a finite-difference scheme to resolve the flow around each particle moving in turbulence. The method was applied to the flow around a sphere and the accuracy was confirmed up to the Reynolds number range with vortex shedding. The agreement between our 4th-order central finite-difference method and spectral method for turbulent channel flow without particles was also fine. Then, we simulated upward flow in a vertical channel including solid particles. The velocity and vorticity fluctuations as well as Reynolds shear stress were strongly affected by wakes from particles. The shed vortices were elongated in the mainstream direction by the velocity gradient and resulted in the hairpin vortices. They increased the energy production rate in couple with production due to particle-turbulence correlation.

Turbulence Structure of Particle-Laden Flow in a Vertical Plane Channel Due to Vortex Shedding

Numerical investigation on flow around circular cylinders in tandem arrangement at a subcritical Reynolds number

Comparison between laminar and turbulent heat transfer in a stationary square duct with transverse or angled rib turbulators

Effect of centrifugal buoyancy on turbulent heat transfer in an orthogonally rotating square duct with transverse or angled rib turbulators

A numerical model was developed based upon the Cubic-Interpolated Pseudo-particle (CIP) Combined Unified Procedure (CIP-CUP or C-CUP) method equipped with a Large Eddy Simulation (LES) model and a re-initialisation method. The model was validated and applied to the laminar dam-break flow problem, the turbulent dam-break flow problem and the tidal bore flow with a weak breaking front. In the laminar dam break flow problem the model resolved the free surface profiles, and the flow calculations were in good agreement with the experiment studies of Martin and Moyce (1952) and the experimental and numerical test of Koshizuka et al. (1995) and Koshizuka and Oka (1996). In the turbulent dam break flow problem, the model included a LES turbulence model and it was applied to a dam break wave in a relatively long channel. The shape of the leading edge was compared with the experimental studies, e.g. Dressler (1952, 1954); Cavaille (1965) and theoretical studies, e.g. Chanson (2005, 2006). In the tidal bore flow with a weak breaking front, the model equipped with a LES turbulence model reproduced accurately the large deformation of the free surface immediately after gate closure and the bore generation. The free-surface profile and surge front celerity data were in good agreement with the experimental data of Koch and Chanson (2005). At a fixed sampling location, the numerical results showed the existence of some short-lived flow reversal next to the bed immediately after the bore front passage. This flow feature was documented by Koch and Chanson (2005) and Chanson (2007). By applying the method to these complex flows, it was shown that the numerical technique was effective for the analysis of various flows in civil engineering applications.

https://espace.library.uq.edu.au/view/UQ:138913/ch6608_long.pdf

A Numerical Study of Open Channel Flow Hydrodynamics and Turbulence of the Tidal Bore and Dam-Break Flows

To apply the direct numerical simulation (DNS) and the large-eddy simulation (LES) of turbulence to flow fields of complicated geometry, a higher-order finite difference method (FDM) has been developed for the body-fitted coordinate system The consistency and the conservat ior property of FDMs are discussed for the collocated grid As numerical examples, DNS results of decaying isotropic turbulence and DNS/LES results for plane channel flow are shown and the influence of variable arrangement is examined The results by the consistent 'interpolation' method for gradient form on the collocated grid agree well with those by other proper FDMs and the spectral method

Kazuhiko Okazaki

Papers

High-Order Finite-Difference Method for Incompressible Flows Using Collocated Grid System