Analysis of Hydrodynamic Ram Effect of Aircraft Fuel Tank Filled with Foam Under Fragment Impact

Modern combat aircraft usually fill the tank with foam, which has been proven to reduce the ignition probability of the tank under fragment impact. However, there is a lack of systematic study on the impact of foam filling on the hydrodynamic ram effect of fuel tank. In this paper, the influence of foam filling and other factors on the hydrodynamic ram effect of tank under fragment impact is studied by numerical simulation. First, a simplified fuel tank model is established by referring to the wing fuel tank of a certain combat aircraft. Then, the finite element model for hydrodynamic ram effect simulation is established and the load transfer between foam, fuel and fuel tank is simulated by ALE algorithm. Finally, the hydrodynamic ram effect of different fragment velocity, liquid filling ratio, tank size and foam filling were simulated and analyzed. Through this study, the following conclusions can be drawn: 1. Filling foam in the tank can significantly reduce the hydrodynamic ram effect under the impact of high speed fragment; 2. In a given situation, there is a size that causes the most severe structural damage to the tank due to the hydrodynamic ram effect. The methods and conclusions of this study can provide basis for the anti-damage design of battle aircraft fuel tank and the high survivability design of aircraft, as well as provide criteria for the battle damage assessment of fragmented warheads to aircraft.