Time-dependent flows of a Newtonian fluid through periodic arrays of spheres were simulated using the lattice-Boltzmann scheme. By applying a constant body force per unit mass to the fluid, a steady background fluid flow through the array of stationary spheres was first established. Subsequently, a small-amplitude perturbation to the body force, which varied periodically in time, was added and ...

A recently derived axisymmetric lattice Boltzmann model is evaluated numerically. The model incorporates a spatially and temporally varying source term into the evolution equation for the momentum distribution function on a two-dimensional Cartesian lattice. The precise form of the source term is derived through a Chapman-Enskog analysis so that the additional axisymmetric contributions in the ...

a r t i c l e i n f o An accurate model for the drag coefficient (C D) of a falling sphere is presented in terms of a non-linear rational fractional transform of the series of Goldstein (Proc. Roy. Soc. London A, 123, 225-235, 1929) to Oseen's equation. The coefficients of the six polynomial terms are improved through a direct fit to the experimental data of Roos and Willmarth (AIAA J., 9:285-2...

In this paper, three-dimensional two phase turbulent free surface flow is solved by an in-house code. The incompressible Reynolds average Navier-Stocks equations (RANS) with k-ε turbulence model are solved by the finite volume method in the non-orthogonal curvilinear coordinates. For the modeling of the free surface effect, Lagrangian propagation volume tracking method (VOF-PLIC) is used. The c...

Drag forces acting on Steller sea lions (Eumetopias jubatus) were investigated from 'deceleration during glide' measurements. A total of 66 glides from six juvenile sea lions yielded a mean drag coefficient (referenced to total wetted surface area) of 0.0056 at a mean Reynolds number of 5.5x10(6). The drag values indicate that the boundary layer is largely turbulent for Steller sea lions swimmi...

The drag coefficient, CD, of an arbitrary shaped object ca;; be calculated by twodimensional hydrodynamic cellular automata. Results spanning nearly four orders of magnitude in the Reynolds number (0.I < Re < 10~) are presented for a simple, hexagonal object, and good quantitative agreement with previous experiments on cylinders is obtained. Hydrodynamical cellular automata (IIDCA), also called...

The adjoint-based sensitivity analyses well explored in hydrodynamic stability studies are extended to calculate the sensitivity of forces acting on an aerofoil with respect to wall transpiration. The magnitude of the sensitivity quantifies the controllability of the force, and the distribution of the sensitivity represents a most effective control when the control magnitude is small enough. Si...

This paper briefly reviews bluff body aerodynamics and focuses mainly on the use of short and thin splitter plates to interfere with the vortex wakes and suppress vortex-induced forces (VIF). The present investigation primarily examines the suppression of unsteady, two-dimensional wake instabilities over a low Reynolds number range of less than 250. A circular cylinder is used as the bluff body...

Aquatic plants convert mean kinetic energy into turbulent kinetic energy at the scale of the plant stems and branches. This energy transfer, linked to wake generation, affects vegetative drag and turbulence intensity. Drawing on this physical link, a model is developed to describe the drag, turbulence and diffusion for flow through emergent vegetation which for the first time captures the relev...