The shipping industry faces significant challenges in energy conservation and emission reduction, for which microbubble drag reduction (MBDR) offers a promising solution. This study numerically investigates the standard KCS container ship model using the RANS method coupled with the Volume of Fluid (VOF) model. Slot-type and multi-nozzle injectors are evaluated across moderate- and high-speed conditions, along with a preliminary combined injection layout. Results reveal a pronounced speed-dependency of injector performance. At moderate speed, slot-type injectors achieve approximately 15% drag reduction by forming a stable continuous air layer. At high speed, multi-nozzle injectors outperform the slot configuration due to broader lateral coverage, with drag reduction increasing monotonically with air flow rate. For the cases studied, the combined layout offers no meaningful advantage over the slot injector alone; its performance is highly sensitive to injector spacing, and excessive proximity induces severe flow interference that undermines drag reduction.
Cui et al. (Mon,) studied this question.