Multiple rows of jets injected into a cross flow with diameters of 0.3 to 3 m were studied experimentally and numerically. The measured values were in good agreement with CFD calculations. The optimum mixing for a single row was obtained at a normalized momentum flux ratio (J/n(2)) of 0.3 with a penetration depth (h/R) of 0.6, which is in accordance with previous studies. This condition is valid for all numbers of nozzles. However, increasing the number of nozzles will also improve the mixing quality. Double rows with a staggered arrangement always give a worse mixing quality, compared to a single row. Double rows with an inline arrangement will improve the mixing quality only if the injected volumetric flows produce over- and under-penetrated jets for a V-jo1/V-jo2 ratio of 3/1 or 1/3. For operation under ever changing conditions a single row with J/n(2) > 0.3 and n >= 24 is recommended.