Out of Memory although using more RAM

Hej there,

I ran a rarefied gas flow model (transitional flow) on my 16GB RAM machine. I build a 2D model with a D2Q36 quadrature and it runs on my machine.
As I want to use an larger quadrature which can not be simulated on my 16GB machine anymore I tried a 38GB RAM machine. But on this even the D2Q36 model that ran on the smaller machine gives an "out of memory during LU factorization" error. How can this be and how top solve this problem?

Thanks
Laura