CALCULATION OF PARTICLE CONCENTRATION AROUND AIRCRAFT-LIKE GEOMETRIES

A computationally-efficient method is presented to calculate local par ticle concentration enhancements resulting from potential fluid flow a round an idealized aircraft fuselage and wing. The geometries chosen f or study are a 10:1 prolate ellipsoid at 0-degrees angle of attack and a Joukowski airfoil at 0-degrees and 5-degrees angles of attack, for which potential flow analytic solutions are known. The collection effi ciency of and surface concentration on a cylinder in potential flow ar e also considered for algorithm verification. Particle concentration i s calculated along particle pathlines by a mixed Eulerian-Lagrangian t echnique developed by Fernandez de la Mora and Rosner (1981, Fernandez de la Mora, J. F. and Rosner, D. E, Physico Chem. Hydro. 2, 1). Ordin ary differential equations for particle position, velocity, and concen tration are integrated numerically by a variable order, backward diffe rence algorithm. The calculations show the creation of regions of incr eased concentration near objects, and of particle-free shadow zones do wnstream. The magnitudes of the concentration disturbances are greates t at intermediate Stokes numbers (0.1-1.0) where inertia and drag are equally dominant. Samplers placed in these regions of enhanced particl e concentration may not provide accurate concentration measurements. U ltimately, this approach could be included with detailed flow solution s about specific aircraft geometries to provide guidance in locating s amplers in regions of acceptably small concentration deviations.