Assessment of the thermovibrational theory: application to g-jitter on the space-station

This paper deals with the numerical modelling of the effects of g-jitter (oscillatory residual acceleration disturbances) of the type prevailing on the International Space Station. Aim of the work is the extension of the averaging technique, initially introduced by the thermovibrational theory, by evaluating the orders of magnitude of all the terms appearing in the complete equations and identifying the role and the importance of average and periodic terms. The evaluation of the most important terms in the momentum and in the energy equation is made by an “a posteriori” order of magnitude analysis (OMA) by means of the numerical solution of the unsteady full Navier Stokes equations. The discussion of the results identify different regimes and help clarifying some apparent contradictions in the current literature on the effects of g-jitter on temperature disturbances generated by convective motions. The identification of the set of “reduced” equations and associated ranges of validity is of potential great importance for the scientific community. They in fact can be used to obtain analytical and/or mixed numerical/analytical solutions that can lead to a significant reduction of the often prohibitive computational time required for the simulation of the phenomena under investigation.