## 1 Introduction
The impact of the step on the stability of the air layer was confirmed by putting up a ship model with a step at the bottom for jet injection while varying the jet flow rate and ship attitude. At the same time, it was suggested that proper hull trim adjustment helped maintain the air layer and that there is an ideal trim angle for various model and step size combinations to produce the best air layer. A 95000 DWT bulk carrier was used in a 1:38 scale air lubrication experiment conducted by [PERSON] [14]. The absolute drag reduction rates were 26.99% and 33.79% for the conditions of design displacement and load displacement, respectively, by air jetting grooves into the bottom of the ship. The effective power and main engine power were decreased by 9.65% and 22.16%, respectively, after conversion to the real ship. Many nations have verified and applied the use of air lubrication technology on actual ships, building on the research done by numerous academics. The Netherlands, Sweden, Japan, and China have among these nations particularly concentrated on low-speed, large-displacement vessels, with a focus on ocean-going ships. In contrast, Russia has made tremendous strides in the study and use of air lubrication technology in high-speed bubble crafts. The Netherlands-based company DKgroup [15] has created an air cavity system for actual ships that has produced energy savings of 5-9% on container ships and 10-15% on oil tankers and bulk carriers. The renowned Swedish shipowner Stena Bulk [16] carried out the \"Air Max Project\" in cooperation with Chalmers University of Technology in Gothenburgand the SSPA Towing Tank. They built a 35-ton test vessel for air layer drag reduction as part of this project and performed experiments on it. The air layer efficiently covered 30% of the ship's wetted surface area during the testing, resulting in a maximum drag reduction rate of up to 25%. In 2010, the Mitsubishi Heavy Industries Group tested the micro-bubble air lubrication system in real ship conditions on the NYK-subsidiary and NYK-Hinode modular transport vessels. According to these experiments, the net energy-saving benefit could only be as high as 12% [17]. The Krelov Shipbuilding Research Institute of Russia has been conducting research on aerodynamic drag reduction technology since 1961 and has conducted theoretical and experimental research on various ship types, such as large transport ships, high-speed boats, planing boats, catamarans, and multibody ships. In the field of high-speed boats, since 1981, more than 70 fast boats have successfully adopted aerodynamic drag reduction technology, with maximum speeds of over 30 knots and a maximum speed of 52 knots [18; 19]. Inland water transportation makes up a substantial percentage of the shipping sector in addition to sea transportation. The motion response of inland transport ships is relatively low due to the low wind and wave activity in the inland waterway, which is beneficial for the coverage and stability of the air layer. However, the waterway's width and depth are substantially reduced due to the limited water depth and channel width, particularly during times of low water levels. Shallow waters have several negative navigational effects, which raise the possibility of collision and grounding. For ships using air lubrication, this will also result in changes to the ship's flow field, which will have an impact on the shape of the air layers and the efficiency of drag reduction. [PERSON] [20] studied air lubrication in shallow water circumstances utilizing a 2D flat plate to address this problem. The research uncovered certain trends about how shallow water affects the efficiency of air cushion drag reduction. [PERSON] [21] also carried out a comparative study on a planning craft with discontinuous steps intended for shallow water navigation, examining the variations in total resistance, trim angle, and heave and pitch motions with respect to the vessel's speed in both deep and shallow water conditions.