Motion: Flow-Driven Motion of small objects may be subject to instability


The motion of very small parts subjected to flow-driven motion can be subject to strong oscillations and a high sensitivity to the momentum of the surrounding fluid.



Very small objects typically have a low mass value. This in turn leads to a relatively low inertia.

One solution is to artificially increase the mass of the object.

Do this by increasing the density of the solid material.

This affects the motion and the solution accuracy, but will result in a more stable simulation. The effect of the higher density should be readily apparent in the reduced oscillatory strength of the motion.

Note that this approach is valid if the goal of the simulation is to determine the steady-state position of the object. This technique is not valid if the objective is to study the time-history of the motion. Changing the density of the object will definitely affect the amount of time it takes to reach its steady-state position as well as the path it may take.


Simulation CFD