Experimental Investigation of Downburst Physics to Derive Scaling Laws*

The behavior of downbursts and their interaction with the ground and structures is being investigated in order to develop scaling relations. Downbursts are extremely powerful and relatively under-examined phenomena that cause extensive damage to both ground structures and aircraft. Most damage is generally caused by an outburst of descending air upon impact with the ground. Tests are performed in a water tunnel using an elevated cylinder of dense fluid to simulate the high-density air. The fluid is dropped and its interaction with the ground is observed. Tracer particles in the dense fluid are then analyzed using particle image velocimetry, and observations quantified to develop scaling laws to apply to full-scale downbursts. Conditions analyzed include different combinations of densities and varying amounts of fluid released, as previous tests showed correlation between these factors and the resulting outburst strength. Results are compared against other simulations in order to verify the model’s accuracy.