turbulent model k-epsilon

yann

hi,

i am trying to look at the flow of air around a rectangle (length 7m and width 2.5m) (in turbulent regime). the inlet velocity is 16.66m/s. i solved in 2nd order implicit segregated. i have tried 3 different models of turbulent regime in order to compare them: k-epsilon standard, K-epsilon realisable and K-epsilon RNG. i did focus my study on the recirculation zone generated after the rectangle and the drag coefficient.

the results i have are quite disturbing: length of recirculation zone: k-espilon standard: 4.44m k-epsilon realisable: 4.36m k-epsilon RNG: 7.59m drag coefficient k-espilon standard: 2.3811 k-epsilon realisable: 2.2554m k-epsilon RNG: 2.5053m

my problem is that i dont understand why the length of the recirculation zone is that big for the case of the k-epsilon RNG. it is almost the double of the length for the realisable or the standard.

if someone has an explanation that would be nice!

thanks