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• Impact of double rows on air/mist film cooling is studied for the first time. • Sellers prediction model is appropriately modified for double rows. • Modified sellers method is proved to be more suitable for air/mist film cooling. • Air/mist film cooling effectiveness is accurately correlated by the modified model. Improving the multi-row film cooling effectiveness of turbine vanes and blades is becoming increasingly important, and the configuration design of the multi-row holes is becoming increasingly complex. This paper presents a simulation study of the air/mist film cooling characteristics on double-row-hole flat plates and makes predictions about spanwise-averaged cooling effectiveness using a modified Sellers superposition method. The effects of blowing ratio, row spacing, row arrangement, droplet diameter, and mist mass ratio on film cooling are systematically investigated. It is found that the injected mist improves the film cooling effectiveness under all operating conditions for the coolant air. The air/mist cooling is particularly effective at a blowing ratio of 1.25 or a row spacing of 5 D with the staggered two-row holes. The improvement in cooling effectiveness increases with increasing mass ratio or decreasing droplet diameter of the mist. Furthermore, the spanwise-averaged cooling effectiveness can be accurately predicted by modifying the classical Sellers superposition model. This study lays the foundation for accurately predicting the distribution of air/mist film cooling effectiveness of turbine vanes and blades, and helps to promote the development of practical air/mist film cooling technology. [ABSTRACT FROM AUTHOR]