Computational Fluid Dynamics (CFD) is an ever evolving numerical tool used to compute fluid flow in complex geometries. Historically, CFD has been used to consider flow in an inertial reference frame. As CFD matures and computational power increases, there is constant research into how the technology can be extended. A recent development is the coupling of a rigid-body solver with a fluid solver. This new technique has the potential to allow CFD simulations to be completed on problems with non-inertial reference frames. Currently, these problems - such as that of an accelerating rocket - have been solved using simplified analytic equations and empirical
In its latest release, FLUENT -a commercial CFD package - has introduced a Six Degree of Freedom (6DOF) solver. FLUENT already had the ability to solve simulations with moving boundaries through its dynamic mesh model; the inclusion of the 6DOF solver has the potential to open an entirely new realm of simulations. According to the advertising material, examples that were once considered inappropriate for CFD can now be solved; including store separation, missile launches, tank sloshing and a host of maritime cases.
The purpose of this study is to critically investigate the FLUENT 6DOF solver and its application to problems with a non-inertial reference frame. This will be achieved through the investigation of the flight trajectories of a water rocket.
Included in this report is a comparison of current numerical techniques, CFD simulations and experimental data of rocket trajectories. The launches of interest are a vertical launch and a mortar launch. Through this comparison, features of the 6DOF solver are investigated with mixed results. It is shown that the FLUENT 6DOF solver is capable of simulating problems with noninertial reference frames. However, the data would suggest that these simulations do not exhibit the accuracy needed for commercial confidence.
There are limitations on what can be drawn from this study. It is shown that the experimental data lacks repeatability, and further testing is needed to improve the confidence of this information. Furthermore, there is a lack of other similar investigations to compare results; hence, there is a chance that restrictions on the 6DOF solver have been exceeded during the study.
In conclusion, this research has demonstrated the enormous potential for CFD codes that incorporates a six degree-of-freedom solver. The FLUENT 6DOF solver has confirmed this capability; however more work appears to be needed to improve the accuracy of the results.