If Duplicate is selected from either the Geometry cell or the header cell, a new system completely independent from the old system is created. Selecting Duplicate from any cell results in the old system and the new system sharing the cells above that cell, if those cells can be shared. Only Geometry and Mesh cells can be shared between Fluid Flow systems. Therefore, if Duplicate is selected from the Mesh cell, only the Geometry cell will be shared. If Duplicate is selected from either the Setup cell or the Solution cell, the new system shares the mesh and geometry from the old system.