A fixed-mesh method for general moving objects in fluid flow was developed and implemented into FLOW-3D®. A general moving object (GMO) is a rigid body with any type of six-degrees-of freedom, fixed-point and fixed-axis motion which can be either user-prescribed or dynamically coupled with fluid flow. The method allows for multiple independently general moving objects.

Equations of motion for rigid body are solved for coupled motion. Area and volume fractions are used to represent the objects in the fixed-grid at every time step to describe time-variation of object locations and orientations. Continuity and momentum equations for fluid and scalar transport equations are modified to account for the effects of object motion. Good agreement was achieved between computational and theoretical/experimental results in several application cases.