Quantitative molecular-mixing measurements in a round jet with tabs

The near field of chemically reacting round jets was studied at Reynolds numbers between 5.2×103 and 3.2×105. The measured chemical product was used to infer molecular mixing. The effects of mixing tabs and Reynolds number were determined. Four tabs enhance molecular mixing more than two tabs do, although two tabs cause the velocity profile to decay faster than four tabs do. The product formation rate is nearly constant with respect to streamwise distance, for turbulent jets with zero, two, and four tabs. The amount of chemical product is determined by both the molecular mixing and the equivalence ratio. The chemical product and the effects of the tabs are independent of Reynolds number, once the jet is turbulent. The effects of the tabs are smaller in a transitional jet than in a turbulent jet.