Retrieval of collision kernels from the change of droplet size distributions with linear inversion

We have developed a new simple inversion scheme for retrieving collision kernels from the change of droplet size distributions due to collision growth. Three-dimensional direct numerical simulations (DNS) of colliding droplets in an isotropic steady turbulence are performed in order to investigate the validity of the developed inversion scheme. In the DNS, air turbulence is calculated using a quasi-spectral method, and droplet motions are tracked by a Lagrange method. The initial droplet size distribution is set to be equivalent to that obtained in a wind tunnel experiment. Comparison between collision kernels retrieved by the developed inversion scheme and those obtained by DNS shows that the collision kernel can be retrieved within 15% error. This verifies the feasibility of retrieving collision kernels by using the present inversion scheme.