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This study analyses the impact of initial conditions on the results of numerical simulations of the fan load with underwater detonation and simultaneously typical harmonic loads from the operating device. It was shown that different initial conditions affect both displacement and velocity results. Furthermore, significant differences were indicated when comparing the results with devices without harmonic loads. The results indicate the need for more detailed analyses at the initial stage of modelling the impact resistance of devices planned for ship installation., (© 2024. The Author(s).)

The paper presents the selected results of the international project called Nextprop, carried out in the framework of the European Defence Agency, which main goal was to examine elastic polymer propellers. The article includes the results of the comparative analysis in terms of the noise produced by two propellers: (1) the classical one made from Nickel Aluminium Bronze (NAB) and (2) the novel elastic counterpart manufactured from polyamide. The measurements were taken in the CTO cavitation tunnel in Gdańsk, Poland. The obtained results allow the following highlights to be formulated: the novel flexible propellers seem to be a promising solution for the new ships, especially in terms of energetic efficiency and produced noise, i.e. lower sound pressure level has been obtained for the new polymer propeller and larger advance speed for the same rotational speeds has been received for the new propeller compared to the classical metal counterpart. At the beginning, the introduction with the results of state-of-the-art analysis is presented. Then, the description of the measurement stand and examined propellers with seizing conditions is included. Next, the obtained results are illustrated and discussed. At the end, the conclusions with the draft of the future research are presented., (© 2023. The Author(s).)

The paper presents the results of research on assessing the accuracy of angular position measurement relative to the sea horizon using a camera mounted on an unmanned bathymetric surveying vehicle of the Unmanned Surface Vehicle (USV) or Unmanned Aerial Vehicle (UAV) type. The first part of the article presents the essence of the problem. The rules of taking the angular position of the vehicle into account in bathymetric surveys and the general concept of the two-camera tilt compensator were described. The second part presents a mathematical description of the meters characterizing a resolution and a mean error of measurements, made on the base of the horizon line image, recorded with an optical system with a Complementary Metal-Oxide Semiconductor (CMOS) matrix. The phenomenon of the horizon line curvature in the image projected onto the matrix that appears with the increase of the camera height has been characterized. The third part contains an example of a detailed analysis of selected cameras mounted on UAVs manufactured by DJI, carried out using the proposed meters. The obtained results including measurement resolutions of a single-pixel and mean errors of the horizon line slope measurement were presented in the form of many tables and charts with extensive comments. The final part presents the general conclusions from the performed research and a proposal of directions for their further development.