Aerosol Sampling from Aircraft: Impact of Turbulence on Aspiration and Transmission Efficiencies

NAGARAJAN RADHAKRISHNAN, Sreekesh Kookkal, Suresh Dhaniyala, Clarkson university

     Abstract Number: 506
     Working Group: Instrumentation and Methods

Abstract
Computational fluid dynamics (CFD) studies of particle transport in aircraft sampling systems have typically overlooked the influence of turbulence on particle trajectories. This is largely due to the error in discrete random walk (DRW) models that are built-in CFD software such as ANSYS Fluent, that result in overprediction of particle loss due to turbulence. In this study, we use a newly developed DRW model to evaluate the role of turbulence in two aircraft inlet designs – a classical solid wall inlet with an expansion region downstream of the entrance and a porous inlet with boundary layer suction. The CFD simulations are conducted with two Reynolds Averaged Navier Stokes (RANS) models: k-ε and k-ω SST in 2D and 3D. The solid wall inlet is modeled under sampling flowrates ranging from isokinetic to anisokinetic. The porous wall inlet is modeled with isokinetic sampling and varying amounts of boundary layer suction. The inlet aspiration and transmission efficiencies were calculated for both inlets using FLUENT’s in-built DRW model and the newly developed DRW code. In this presentation, we will highlight the role of turbulence on sampling performance considering both the CFD models, both DRW models, and the two inlet designs. The results will be compared against classical results obtained ignoring turbulence.

Keywords: Aircraft sampling, Turbulent deposition, Boundary layer suction, Low turbulence inlet.