Computational Models for Turbulent Reacting Flows

Appendix B: Direct Quadrature Method of Moments

B.1 Quadrature Method of Moments

The quadrature method of moments (QMOM) is apresumed PDF approach that determines the unknown parameters by forcing the lower-order moments of the presumed PDF to agree with the moment transport equations (McGraw 1997; Barrett and Webb 1998; Marchisio et al. 2003a; Marchisio et al. 2003b). As with the multi-environment presumed PDF method discussed in Section 5.10, the form of the presumed PDF is

(B.1)

where N s = K + 1 is the number of scalars in the composition vector ?. However, unlike with the multi-environment model, the probabilities p n and conditional means ? ? ? ? n are found by forcing (B.1) to yield known values for the moments:

(B.2)

where the m i are typically chosen to be non-negative integers.

As an example, consider a uni-variate case ( N s = 1) where

(B.3)

The right-hand side of this equation involves 2N e unknowns: ( p 1,..., p Ne) and ( ? ? ? 1,..., ? ? ? N e). In the QMOM approach, these unknowns can be found from a unique set of 2 N e moments. For example, integer moments with m = 0, 1,..., 2 N e 1 can be employed:

(B.4)

The modeling problem then reduces to finding ( p 1 ,..., p Ne) and ( ? ? ? 1,..., ? ? ? N e) assuming the left-hand...

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