Volumes and voids versus concentrated forces
Rather than inserting voids or new volumes into the model, an equivalent load could be considered. For example, the weight of a rectangular block can be considered as a vertical force applied at its centroid. However, to account for the inertia forces generated by all the masses in the model, it is preferable to use volumes or voids rather than concentrated forces. In addition, these volumes or voids generate hydrostatic forces when in contact with the reservoir.