I did fluid simulation where fluids fall on the obstacle object but … they are actually few centimeters higher then that object is. (Sorry for my english, i hope that you understand my problem).
Yes, that is correct. The fluid simulator is not good at interfaces and closeups. It always makes a negative meniscus (too strong a surface tension and no capillary action simulation). So, for example, when you spill your milk on the table, make your domain or obstacle, bake and then move the table up to intersect the fluid before rendering. This also plays havoc with internal shadows. Things improve as you increase domain resolution but it is impossible to get better than 1/2 the voxel size.