I have an Image file of micro CT images in nhdr, and in raw format(dci format can also be obtained) from which I am able to view using ImageJ/paraview and able to generate pore network model. Now I want to simulate these 3D model for permeability prediction. What is the way to simulate such 3D images? I have heard of Avizo software. Is there any open source software from where I can perform these simulation?