This research modeled low-speed flow past idealized engine nacelle clutter in support of aircraft fire suppression research. The idealized clutter was comprised of three vertical rows of staggered circular cylinders approximating typical nacelle obstructions such as fuel lines and wire bundles. Single-phase Detached-Eddy Simulations (DES) were conducted using the commercial CFD solver, Fluent?, to resolve the flow-field dynamics inside the clutter element. The goal of the simulations was to examine potential droplet transport and trapping mechanisms in the flow field which might inhibit or facilitate fire suppressant transport through engine clutter under low-speed flow conditions (ReD = 1, 575). The resulting numerical models provided no evidence that span-wise vorticity or three-dimensional shedding effects were responsible for transporting or trapping dispersed-phase particles. However, the simulations did demonstrate that suppressant droplets would likely follow a path governed by the vector sum of the local carrier fluid velocity and the velocity imposed by gravity. The Stokes number was computed from time-accurate data to determine the ability of dispersed particles to negotiate the clutter element without impinging on a cylinder. For slower free-stream velocities, Uoo = 1 rn/s, suppressant droplets (D = 90 /im) will likely be entrained in vortices shed from the intermediate row of cylinders and subsequently deposited on the last row of cylinders as the Karrnan vortex directly collides with the clutter. At free-stream velocities, Ux, = 5 m/s, the droplet particles will likely fail to track the carrier fluid streamlines in the cylinder wake and remain free of any shed vortices. Thus, the suppressant will conceivably transit the cylinder array without impact. These findings imply that a bluff-body turbulent diffusion flame in a cylinder wake could be nearly impossible to extinguish under high-speed, co-flow conditions. Conversely, suppressant transported by low-speed co-flow would experience difficulty traversing the cylinder array and reaching a downstream fire.
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