please help to improve grammar of the following paragraphMany efforts have been devoted to investigate air-water two-phase flow pattern in narrow channel during the past decades Wilmarth and Ishii8 me

Over the past few decades, numerous efforts have been made to investigate the air-water two-phase flow pattern in narrow channels. Wilmarth and Ishii[8] measured the flow using a charge-coupled device in both narrow vertical and horizontal channels. They found that the bubbly to slug transition in narrow channels aligns with the flow regime transition criteria proposed by Mishima and Ishii[9] for tubes when using a suitable value of the distribution parameter C0. However, their results were less satisfactory for the slug to churn-turbulent transition. Xu and coworkers[10, 11] examined the flow pattern of air-water flow in narrow channels with gaps of 0.3, 0.6 and 1.0mm by using a high-speed camera. They determined that the transition boundaries on the flow pattern map shifted to a lower gas superficial velocity as the channel gap decreased. They also proposed a flow regime transition criteria for narrow channels based on the Mishima & Ishii model[9]. Hibiki and Mishima[12] also proposed a flow regime transition criteria for narrow channels following the concept of the Mishima & Ishii model[9]. They stated that the criteria could be applied to air-water flows in narrow rectangular channels with gaps larger than 0.3mm when compared with available data. Satitchaicharoen and Wongwises[13] studied the effects of channel geometry and liquid viscosity on the flow pattern maps of narrow channels by using a high-speed camera. They found that the transition boundary of air-water flow shifted to a lower superficial gas velocity as the channel gap or channel width decreased. Furthermore, as the liquid viscosity increased, the bubbly to slug transition boundary shifted to a lower superficial gas velocity, while the slug to churn and churn to annular transition boundaries shifted in the opposite direction. Wang et al.[14] experimentally investigated the critical void fraction of the bubbly to slug transition of air-water flow in narrow channels by using a high-speed camera. Based on their experimental data, they adjusted the critical void fraction of the Hibiki & Mishima model[12] by considering the channel aspect ratio. Chalgeri and Jeong [6] used a high-speed camera to measure the flow patterns of upward and downward air-water flow in narrow rectangular channels. They identified four different flow patterns for the vertical upward flow and seven flow patterns for the vertical downward flow