Recently there has been an increasing interest for a better understanding of
ultra low Reynolds number flows. In this context we present a new setup which
allows to efficiently solve the stationary incompressible Navier-Stokes
equations in an exterior domain in three dimensions numerically. The main point
is that the necessity to truncate for numerical purposes the exterior domain to
a finite sub-domain leads to the problem of finding so called "artificial
boundary conditions" to replace the conditions at infinity. To solve this
problem we provide a vector filed that describes the leading asymptotic
behavior of the solution at large distances. This vector field depends
explicitly on drag and lift which are determined in a self-consistent way as
part of the solution process. When compared with other numerical schemes the
size of the computational domain that is needed to obtain the hydrodynamic
forces with a given precision is drastically reduced, which in turn leads to an
overall gain in computational efficiency of typically several orders of
magnitude.Comment: 17 pages, 3 tables, 11 figure
