Flexible slosh diaphragm modeling and simulation in propellant tanks
Levine, Darren Vaughn
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Liquid sloshing and propellant distribution is an important field of research for aerospace applications such as launch vehicles and spacecraft. The propellant mass behavior can greatly influence vehicle dynamics, altering trajectories and structural loading distributions. In order to combat these concerns some propellant tanks employ thin elastomeric diaphragms to separate the fuel from the gas volumes and restrict the fluid's motion. The diaphragm’s flexible behavior is generally highly nonlinear, and various propellant fill levels and acceleration conditions can cause large deflections resulting in complex buckling and folding patterns. When complex and non-uniform deformations occur, there is potential for diaphragm wear and damage to occur at contact and bending regions. Therefore the problem of simulating a diaphragm coupled with a fluid is essential to mass distribution prediction and damage prediction. This thesis explores and implements several fluid coupled diaphragm modeling techniques. Additionally, a comparison with experimentally obtained 3D scans of a diaphragm is made. The results from these analyses show that by using a soft body deformation model, membrane displacement behavior can be predicted with an average error of 7.1% with a standard deviation of 3.3%.