On the added mass force at finite Reynolds and acceleration numbers

Numerical simulations of flow around a rigid sphere, subjected to a sudden acceleration (or deceleration) in relative velocity, are considered. Particular attention is paid to the interaction between the imposed sudden acceleration and a preexisting finite Re wake. The results clearly establish the independence of added mass coefficient to the acceleration number and to the state of flow prior to acceleration. A simple reasoning based on the different time scales of the flow is given.