Numerical investigation of the effect of clearance between control surfaces and body on some linear maneuvering hydrodynamic coefficients of suboff benchmark model

With the development of AUVs, accurate calculation of hydrodynamic coefficients in the equations of motion of these vehicles increased significantly, and accurate calculation of hydrodynamic coefficients for predicting maneuverability, dynamic stability, and controller design is of particular importance. One of the effective parameters in the uncertainty of the results obtained from the regression methods for calculating the hydrodynamic coefficients is the clearance between the control surfaces and the body. In this article, to investigate the effect of the clearance on some linear hydrodynamic coefficients of the maneuver, a numerical analysis has been performed on the Suboff benchmark model, and the damping and added mass coefficients have been studied using static and dynamic tests. The vertical clearance of the control surfaces from the body is considered a variable and the analysis has been done at several clearance from the body. The numerical results, after validating with the model results, showed that the hydrodynamic coefficients become independent of the distance between the body and the control surfaces from the distance of 0.06 meters. Also, in the static drift test, with the increase in the clearance of the control surfaces from the body, the hydrodynamic coefficient related to the sway force and the hydrodynamic coefficient related to the yaw moment decrease. However, in the pure sway test, with the increase in the clearance, the hydrodynamic coefficient related to the sway force decreases, and the hydrodynamic coefficient related to the yaw moment first decreases and then increases.