1,721,098 research outputs found
A parallel multi-block method for the unsteady vorticity-velocity equations
No full textThis paper provides a numerical method
for solving two- and three-dimensional unsteady incompressible
flows. The vorticity-velocity formulation of the
Navier–Stokes equations is considered, employing the
vorticity transport equation and a second-order Poisson
equation for the velocity. Second-order-accurate centred
finite differences on a staggered grid are used for the
space discretization. The vorticity equation is discretized
in time using a fully implicit three-level scheme. At each
physical time level, a dual-time stepping technique is
used to solve the coupled system of non linear algebraic
equations by various efficient relaxation schemes. Steady
flows are computed by dropping the physical time derivative
and converging the pseudo-time-dependent problem.
A domain decomposition of the physical space is also
employed: the multi-block algorithm allows one to handle
multiply-connected domains and complex configurations
and, more importantly, to solve each grid-block on a
single processor of a parallel platform. The accuracy and
efficiency of the proposed methodology is demonstrated
by solving well known two-dimensional flow problems.
Then, the steady and unsteady flows inside a cubic cavity
are considered and the numerical results are compared
with experimental and numerical data
Experimental and numerical investigation on the performance of a Wells turbine prototype
No full textDetailed CFD analysis of the steady flow in a Wells turbine under incipient and deep stall conditions
No full textThis paper presents the results of the numerical simulations carried out to evaluate the
performance of a high solidity Wells turbine designed for an oscillating water column
wave energy conversion device. The Wells turbine has several favorable features (e.g.,
simplicity and high rotational speed) but is characterized by a relatively narrow operating
range with high efficiency. The aim of this work is to investigate the flow-field through
the turbine blades in order to offer a description of the complex flow mechanism that
originates separation and, consequently, low efficiency at high flow-rates. Simulations
have been performed by solving the Reynolds-averaged Navier–Stokes equations together
with three turbulence models, namely, the Spalart–Allmaras, k-, and Reynolds-stress
models. The capability of the three models to provide an accurate prediction of the
complex flow through the Wells turbine has been assessed in two ways: the comparison of
the computed results with the available experimental data and the analysis of the flow by
means of the anisotropy invariant maps. Then, a detailed description of the flow at
different flow-rates is provided, focusing on the interaction of the tip-leakage flow with the main stream and enlightening its role on the turbine performance
- …
