This paper reports the result of direct simulations of fluid–particle motions in two dimensions. We solve the initial value problem for the sedimentation of circular and elliptical particles in a vertical channel. The fluid motion is computed from the Navier–Stokes equations for moderate Reynolds numbers in the hundreds. The particles are moved according to the equations of motion of a rigid body under the action of gravity and hydrodynamic forces arising from the motion of the fluid. The solutions are as exact as our finite-element calculations will allow. As the Reynolds number is increased to 600, a circular particle can be said to experience five different regimes of motion: steady motion with and without overshoot and weak, strong and irregular oscillations. An elliptic particle always turn its long axis perpendicular to the fall, and drifts to the centreline of the channel during sedimentation. Steady drift, damped oscillation and periodic oscillation of the particle are observed for different ranges of the Reynolds number. For two particles which interact while settling, a steady staggered structure, a periodic wake-action regime and an active drafting–kissing–tumbling scenario are realized at increasing Reynolds numbers. The non-linear effects of particle–fluid, particle–wall and interparticle interactions are analysed, and the mechanisms controlling the simulated flows are shown to be lubrication, turning couples on long bodies, steady and unsteady wakes and wake interactions. The results are compared to experimental and theoretical results previously published.

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Direct Simulation of Initial Value Problems for the Motion of Solid Bodies in a Newtonian Fluid Part 1. Sedimentation

Thermal performance criteria of elliptic tube bundle in crossflow

A review of bluff body wakes

A numerical investigation of louvered fin-and-tube heat exchangers having circular and oval tube configurations

Fluid flow and heat transfer over a 4-row. elliptic, finned-tube heat exchanger having an axis ratio of 2.83:1 are studied experimentally and numerically. Three types of finned-tube configurations have been investigated under dry and wet conditions for different values of inlet frontal velocity ranging from 2 to 7 m/s: two elliptic finned tubes with staggered and in-line arrangements and one circular finned tube with staggered arrangement. The experimental results indicate that the average heat transfer coefficient of an elliptic finned lube is 35–50% of the corresponding circular finned tube having the same tube perimeter, while the pressure drop for an elliptic finned-tube bank is only 25–30% of the circular finned-tube bank configuration. Three-dimensional numerical results of a laminar model for dry coils are also presented and are compared with the experimental data.

Taoka Yukiyasu

Papers

Heat transfer and flow around an elliptic cylinder