Before revision:  A few modes in the semi-infinite subdomain are found to suffice to deal with outgoing single wave and wave train signals  , thus providing an appealing model for fluid flow simulations in unbounded regions.
After revision:  A few modes in the semi-infinite subdomain are found to suffice to deal with outgoing single wave and wave train signals more accurately than standard approaches at a given computational cost , thus providing an appealing model for fluid flow simulations in unbounded regions.