Water in Fuel Sloshing for Aircraft Fuel Tanks

Water is an unavoidable contaminant in aircraft fuel tanks. During an aircraft manoeuvre, fuel and water will slosh. The sloshing of two liquids (two-liquid sloshing) gives rise to a number of interesting phenomena which single-liquid sloshing does not experience. These include internal waves at the liquid-liquid interface and interaction between the motions of the two liquids. This paper investigated the ability of three commercial Computational Fluid Dynamics (CFD) modelling packages to accurately predict the pressures imparted on the tank walls of a rectangular tank when excited at near-resonant frequency while containing two liquids; water and fuel. A sloshing test rig was set-up to provide both qualitative (visual images) and quantitative (pressure data) results for comparison with the CFD calculations. The CFD calculations correlated well with the experimental results qualitatively and quantitatively. Snapshots of the sloshing show that CFD is able to model the wave modes reasonably well; and the pressure data show that CFD is able to simulate the pressure them were postulated.