RESEARCH ON THE INFLUENCE OF SUPPORT SWORD STRUCTURE ON THE DRAG RESISTANCE OF UNDERWATER VEHICLES AND CORRECTION METHOD

Towing tank tests are a crucial method for determining the hydrodynamic resistance parameters of underwater vehicles, which are essential for predicting operational performance and optimizing hull design. However, the indispensable support strut used for model mounting introduces significant parasitic effects and flow field disturbances. This issue is complicated by the coupled interaction with the free surface at varying submergence depths, which severely compromises the accuracy and fidelity of resistance measurements.To address this challenge, this study employs a hybrid methodology that combines physical towing tank experiments with high-fidelity computational fluid dynamics (CFD). This approach facilitates a systematic investigation into the strut's influence on the total resistance of an underwater vehicle, as well as its constituent components of pressure and frictional drag, across a comprehensive range of depths. To validate the baseline data, a rigorous uncertainty analysis of the experiments was also conducted in accordance with the International Towing Tank Conference (ITTC) guidelines. Building upon these analytical findings, a systematic strut interference correction methodology was formulated based on the specific resistance components decomposed via CFD. The fundamental core of this method lies in rigorously correcting the pressure resistance, simultaneously, the frictional resistance is determined by fitting the classical theoretical flat plate friction formula, thereby enabling the calculation of the final corrected total resistance. The results reveal that the strut's impact on total resistance stems primarily from two mechanisms: abrupt pressure variations at the strut-hull intersection and the complex, coupled hydrodynamic interaction of their respective wakes. These phenomena lead to a substantial, erroneous increase in the measured pressure drag. The study ultimately yields an empirical formula for the frictional drag coefficient and a targeted correction for the pressure drag coefficient. These are synthesized to produce a more accurate total drag coefficient, effectively mitigating the interference effects of the support strut and enhancing the overall reliability and practical value of experimental data.