Abstract:
A three dimensional
implicit multiblock Navier-Stokes solver for hovering rotor
vortical flow simulations has been developed. The governing equations used are
cast in an attached blade rotating frame. Two formulations of the governing
equations using the relative or absolute velocity as variables respectively are
employed and investigated. The Osher's approximate Riemann solver is used for
the convective fluxes evaluation. A modified MUSCL scheme is employed for
improving the accuracy of the discretisation for the in viscid fluxes. A Block
Incomplete Lower and Upper Decomposition (BILU) is adopted for solving the
linear
system resulted from the use of an implicit scheme. Special treatment for
the terms, including extra flux terms and source terms, arising from the non-
inertial reference
system are implemented. A multiblock technique is used to
obtain the
exibility for quality grid generation. The suitability of different grid
topologies for vortex wake capturing is demonstrated. Numerical tests show that
significant improvement in computational efficiency is achieved by utilising the
BILU
implicit scheme in both fixed wing and hovering rotor calculations.
Numerical simulations also demonstrate Navier-Stokes solutions give more
accurate results than that from Euler solutions, especially in transonic tip speed
cases.
Computed results including surface pressure distributions and tip vortex
trajectories are compared with the experimental data, which shows that the
developed solver and the numerical scheme can simulate hovering rotor flows
with
good accuracy.
