Simulation of simplified-frigate airwakes using a lattice-Boltzmann method

The airwakes of two simplified-frigate shapes were analysed as part of a study of the complex flow field generated as a helicopter interacts with the airwake of a ship. The current computational studies simulate ship airwake without an immersed helicopter rotor. This flow simplification provides insight into the environment a maritime helicopter pilot will encounter when operating from a frigate or frigate-like ship. The flow around the simplified frigate shapes were simulated using the lattice-Boltzmann flow solver PowerFLOW and the results compared to experimental data. That data included the surface flow visualization on one shape and unsteady off-body velocity measurements on the other. From both the surface and off-body mean flow comparisons, it is shown that the lattice-Boltzmann method captures the correct flow topology. The root-mean-square (RMS) of the fluctuating velocities of the simulated airwake are also seen to match well with the measured RMS velocities. The presented results indicate that the lattice-Boltzmann algorithm will capture both the mean and unsteady portion of the airwake on and off the surface of the frigate for low to moderate wind angles.