In the fields of hull structure construction, maintenance, and digital twinning based on digital technology, a reliable positioning method is required to achieve real-time alignment between a ship's digital model and the coordinate system of the physical structure, thereby determining the position of data acquisition points within the hull model's coordinate system. This paper utilizes a lightweight RGB-D camera to acquire image data of the hull structure. Visual feature extraction algorithms are employed to obtain structural features. A method for real-time coordinate alignment between the image data and the 3D model data based on the feature data is proposed, enabling fast and accurate alignment of the image and model coordinate systems. The method first extracts linear features from a prior 3D model of the structure to define the model coordinate system. It then generates corresponding linear features in the 3D reconstruction space from the depth and color images captured by the RGB-D camera. Finally, based on a linear registration algorithm, the fusion of the prior 3D model and the reconstructed model is achieved, enabling the real-time calculation of the positions of the RGB-D camera’s acquisition points within the coordinate system of the structural 3D model.

There are great challenges to the air environment design of some ship cabins with large space, high occupant density and complex structure. The traditional ventilation method cannot meet the requirement. The application of the displacement ventilation system for a ship cabin is then researched by adopting the computational fluid dynamics(CFD) method. The physical modeling and numerical calculation modeling are established for the simulation analysis and optimization of the air distribution and thermal comfort in the early design stage. The original scheme and the optimization scheme of the displacement ventilation system for a ship academic hall are compared and analyzed. The results indicate that the displacement ventilation system is characterized of the stratified flows and the vertical temperature gradient. Compared with the original scheme, the optimization scheme optimizes the cabin temperature, wind speed and thermal comfort index, effectively reduces the blowing sense, ensures the air quality around the human body, and its thermal comfort index also meets the standard requirements. The conclusions will provide reference in the application research of the displacement ventilation systems for ships.