Search

A large-eddy simulation method of calculating the flow past an elastically-supported body, has been constructed based on the finite difference method formulated in the coordinates fixed on the moving body. The boundary conditions on the body can be applied in the same way as on a fixed body. Reconstruction of computational mesh or interpolation of the computational points is not needed as the body moves. The coding of the method is simple and the computation is efficient, but the equations of motion must be written in the non-inertial coordinates and the boundary conditions on the outer boundaries of the flow domain that also move must be adjusted as the orientation of the body changes. The method has been tested in the computation of the flow past a rectangular cylinder supported by a spring and dashpot and the motion of the cylinder for which experimental data are available. Comparison with experimental data in the case of a rectangular cylinder of depth to breadth ratio of D/B =2 indicates that the characteristics of the translational oscillation corresponding to the heaving of long beams and the rotational oscillation corresponding to the torsional deformation are reproduced well. [ABSTRACT FROM AUTHOR]

Three-dimensional unsteady flow in the intake channel of a small-scale hydroelectric power facility has been simulated numerically using a large eddy simulation technique. The basic numerical method is the highly simplified MAC iteration method modified for the free-surface flow. The standard Smagorinsky model with near-wall damping and correction for irrotational strain was used to evaluate the sub-grid scale stresses. Using the numerical grid that marginally resolves the near-wall flow of laboratory-scale Reynolds number, the complex and unsteady nature of the vortical flow can be reproduced well. The free-surface depression associated with the formation of a free-surface vortex and its time development, which have so far been difficult to be reproduced numerically, are particularly well captured. The present study shows that this method is relevant for predicting the intake flows with possible air entrainment. [ABSTRACT FROM AUTHOR]