This study focuses on direct numerical simulations of temporally evolving mixing layers with selective bubble placement. Such computations allow direct investigation of the two-way interaction between turbulence modulation and bubble dispersion. The turbulence modulation mechanism is characterized through evaluation of the fluctuating velocities resulting from local and global modification of the large-scale structures. In addition, dispersion mechanisms are investigated through statistical tracking as a function of bubble length and time scales. Results show that classical steady-state lift and drag coefficients are not sufficient to describe local bubble-eddy interactions.

Cinematography particle image velocimetry is used to identify velocity vectors throughout a two-dimensional plane of a turbulent flowfield as a function of time. To resolve the temporal dynamics, the PIV technique is combined with a high-resolution movie camera. This technique involves multiple laser scans over an interrogation domain that focuses on two to three eddies per frame. Issues of bubble dispersion in large-scale structures are then studied directly, and directly compared with numerical time integration studies.

The objective is to properly predict the uniformity of the liquid water content produced by spray bars in wind tunnels used to simulate clouds for icing tests. A computational fluid dynamics methodology is being developed that treats the droplets in Lagrangian form and the water vapor in Eulerian form. Recent research has allowed a novel cpu acceleration with independent local time stepping for the two reference frames.

* Denotes principal investigator.