Abstract
In this study, a numerical simulation of clear air turbulence (CAT) was carried out by an large eddy simulation (LES). Measurement-integrated simulation based on four-dimensional variational method (4D-Var) was introduced because it is difficult to determine initial and boundary condition for CAT. The 4D-Var is formulated as a minimization problem of a cost function of initial flow variables, thus an adjoint code was developed to obtain gradient of the cost function at one time. The 4D-Var was applied to the flight data obtained when an aircraft encountered CAT. Characteristic vortices which correspond to CAT was reproduced by the 4D-Var. And then, power spectrum density of reproduced flow field was investigated.
