difference between MIKE 21 and MIKE 21 fm?

Hi,
i have done 2D flood modelling using bathymetry with MIKE 21. then i used the same bathymetry for 2D modelling with MIKE 21fm. but im getting completely different inundation pattern. why this is happening?
thanks in advance...

Hi Vadlamudo Premkumar,

the answer for your question could depend on a lot of things: As one fundamental difference between MIKE 21 and MIKE 21 FM is the representation of the bathymetry, I would first look at the mesh in MIKE 21 FM:
* Does it represent the key features of the bathymetry grid which was used in MIKE 21?
* How is the model result when you use a finer mesh (say refine by factor 0.5)?

Best regards
Stefan

hi stefan,
yes, i agreed with that. but in MIKE 21 fm we can choose either bathymetry or mesh. i'm using the same bahymetry which i used for the MIKE 21. so the entire input for both MIKE 21 and MIKE 21 fm is same but result not getting the same.

thanks and regards

Hi Vadlamudir,

please note that the numerical methods in both modules are different (finite differences in MIKE21 vs. finite volumes in MIKE21FM). When switching the model from MIKE21 to MIKE21FM, you need to recalibrate it.