Thank you Mathias.rnYou’ve mentioned that OpenLB does not have a free surface solver.rnTo me it sounds that it cannot be used for my task. Or I am wrong?rnI believed that if two “”liquids”” with different densities (water and air), and gravity are specified, then surface will appear automatically. And a hard body of intermediate density will automatically float. Like on this video.rnhttps://www.youtube.com/watch?v=5F-qHsPIrYErnIs it not the case with OpenLB?rnAm I too naive, and it is not that simple? :)rnrn