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Generalization of Reichardt's Hypothesis: Multiple Coflowing Square Jets

Author(s): B. S. Pani; Joseph H. W. Lee; Adrian C. H. Lai

Linked Author(s): Joseph Hun-Wei Lee

Keywords: Reichardt’s hypothesis; Coflowing jets; Multiple jets; Link factor; Square jets

Abstract: Reichardt’s momentum transfer hypothesis for turbulent jets in a stagnant ambient was used in the past for predicting the flow field of multiple circular jets held in a line. Application of a similar principle for coflowing square jets needs some basic changes in the formulation. Most integral methods presuppose the velocity excess and the concentration distribution to follow the normal distribution. In the present approach, the distribution of uΔu is considered as Gaussian. The governing equation of motion is made linear in uΔu and provides the necessary theoretical basis for superposition. However, while applying the principle of superposition, a characteristic width of the jet b is needed. Unlike the stagnant ambient case, the variation of b with the distance x is non-linear in case of coflowing jets, and is an unknown parameter. For a single jet, the decay of the maximum momentum flux, u m Δu m with x is predicted based on a modified large eddy hypothesis for the spread of the jet. Using the method of superposition, the velocity field and the dilution downstream of multiple square jets in a coflowing stream have been predicted. Experimental data of multiple equivalent circular coflowing jets validate the predictions based on the generalized hypothesis.


Year: 2010

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