-Onthebasisofthephysicalmechanism,abody-fittedcoordinatesystemisdeveloped.Byusingthissystemtheboundariesinsimulationandinrealarefittedwell,andsimulationwithgreataccuracyisachieved.Acomputationexampleindicatesthatcomparedtotraditionaltwo-dimensionalcomputationmethods,thebody-fittedsimulationhasanadvantangeofbettercoincidencewiththerealandcanbeadoptedinsimulatingflowfieldsintidalestuaries.