The only two possibilities for examining the thermal-hydraulic behavior of a liquid-metal spallation source target are either to build a full-size target and install it in a proton beam, suitably supplied with coolant under design conditions and instrumented, or to simulate such a target using a state-of-the-art computational fluid dynamics computer code. This latter approach has been pursued in the design of the proposed European Spallation Source for a target filled with liquid mercury coolant under forced circulation. Results indicate that a carefully designed target can remove the 2.8 MW of heat that neutronics calculations predict will be deposited within the coolant and the target body, without the overheating of either.