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Show The sources in the variance equation [4] come from gradients in mean fuel mixture fraction and from the turbulence level as: v eff ,3? 'gl a. <lx7> g2 p H * (10) In the COMO chemistry model, the fluid properties such as species concentration, fluid density, and temperature, are computed with a probability density function (PDF). This function accounts for the phenomena where chemical reactions are controlled by the mixing of fuel and oxidant which are contained in individual turbulent eddies. Properties are obtained with the relation:* •(f) P(f) df (11) The goal of the calculations is to find the function P(f) given 1 and g such that the following definitions are satisfied. O f P(f) df (12) (f - I)2 P(f) df (13) J0 COMO currently uses a triangular function for the shape of the PDF. Given the shape, two parameters can completely describe the function P(f). These para- *This equation holds for species concentration. For density and temperature a Reynolds average is used so that <J> - 1/p for density, <j> - T/p for temperature. -8- |