分野別セミナー

A good choice of far-field boundary conditions (BCs) for the simulation
of airfoil and other aerodynamic flows, allows the minimization of the
domain size for a given level of error or the converse. Simulations of a
NACA 0012 airfoil for a range of angles up to 45 degrees using OpenFOAM,
show the need for consistency with the Kutta-Joukowsky (KJ) equation for
the lift in the form of a point vortex boundary condition. This is not
surprising, given that the KJ equation is well-known. What is less
well-known is that consistency with the drag requires a point source
BC. A combined point source, point vortex BC is easy to implement, but
still may be inconsistent with the moment equation for the body. This
may adversely affect the accuracy of the torque computed for, say,
vertical axis turbines which are often simulated in
two-dimensions. Methods of achieving consistency with the moment
equation will be discussed and a surprisingly simple correction for the
use of commonly-used, but inconsistent BCs, will be described.