Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach-Institut, EMIResearchers are investigating the hydrodynamic ram effect (HRAM) on water-filled tanks.
April, 2026. Collisions with birds, drones, or other flying objects pose a major danger to aircraft. If they strike the leading edge of the wings—where the fuel tanks are located—they can trigger the hydrodynamic ram effect (HRAM). HRAM is a complex phenomenon in which the liquid and the tank structure interact extremely rapidly in a fraction of a second. In the worst case, this event can lead to structural failure.
These effects can be simulated in the laboratory: highspeed projectiles strike water-filled tanks. Water has physical properties comparable to kerosene, but without the risk of fire or explosion.
Fraunhofer EMI conducted a series of such tests to analyze tank deformation and failure. Using commercial numerical simulation programs such as ANSYS/ LS-DYNA and ANSYS/AUTODYN-3D, the scientists simulated the experiments to additionally analyze the fluid dynamic processes inside the water-filled tank.
The experiments revealed how cavities form, oscillate, and collapse again in the water—accompanied by precise pressure measurements.
The simulations captured the phases of the HRAM effect and demonstrated projectile deceleration and fluid motion.
The research provided valuable insights into the HRAM phenomenon and validated numerical methods for safety-critical applications in aviation.
In future work, the scientists will refine the material models and couple the structural simulation with the “APOLLO Blast Simulator” to describe the shock wave in the liquid. Another aspect of the numerical research is the modeling of liquid hydrogen (LH2) instead of tap water.
