A-POSTERIORI ERROR ESTIMATION FOR FINITE-ELEMENT SOLUTIONS OF HELMHOLTZ-EQUATION .2. ESTIMATION OF THE POLLUTION ERROR

In part I of this investigation, we proved that the standard a posteri ori estimates, based only on local computations, may severely underest imate the exact error for the classes of wave-numbers and the types of meshes employed in engineering analyses. We showed that this is due t o the fact that the local estimators do not measure the pollution effe ct inherent to the FE-solutions of Helmholtz' equation with large wave number. Here, we construct a posteriori estimates of the pollution err or. We demonstrate that these estimates are reliable and can be used t o correct the standard a posteriori error estimates in any patch of el ements of interest. (C) 1997 John Wiley & Sons, Ltd.