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Item type:Publication, Access status: without files , Dynamic analysis of variable depth sonar systems under realistic sea conditionsUnderwater detection is an important capability for many vessels, particularly naval and research ships, where accurate and reliable data is essential. To enable this capability, vessels are often equipped with variable depth sonar (VDS) systems that are typically towed behind the ship. The deployment and retrieval of such towed bodies can exhibit complex and potentially uncontrolled dynamic behaviour—not only while entering or exiting the water but also in the underwater near-field of the vessel. For instance, if the towed body enters the propeller wash, it may experience uncontrollable oscillations, making a safe retrieval impossible. Therefore, calculating and predicting the motion behaviour and the influence of external forces acting on the system during deployment and retrieval is of great importance. This paper presents a comprehensive and modular approach for modelling the dynamic motion behaviour of a VDS system deployed from a shipborne crane. The model accounts for ship-induced excitations, external forces and the complex oscillatory motion of the towed body. Ship motions are simulated using the E4-ROLLS method, while the VDS dynamics are formulated within a multi-coordinate framework based on the system’s differential equations of motion. The model combines ship-induced excitations at the deployment point as well as hydrodynamic damping effects due to water resistance. Furthermore, external forces acting on the VDS during underwater operation are considered, particularly those arising from interactions with the vessel’s propeller wash and surrounding environment. The proposed approach provides a valuable tool for enhancing the deployment strategies and operational performance of variable depth sonar systems under realistic sea conditions.Publicationtype: Conference Paper5 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Optimization of oscillation dynamics in a VDS deploymentUnderwater detection is a fundamental capability for many vessels, especially for naval and research ships, where precise and reliable data is crucial. To achieve this capability ships can be equipped with a variable depth sonar (VDS) system, which is generally towed behind the vessel. When such a VDS system is launched into the water, it experiences excitation induced by the ship’s motion, causing the body to oscillate. These oscillations can result in amplitudes increases and uncontrolled behavior, which can damage the VDS and reduce the vessel’s operational effectiveness. If the oscillation of the VDS, while it’s launching, can effectively be predicted, and damping due to rope motion can be modeled the potential of underwater detection of the vessel can significantly be increased. In this paper, a method is presented to calculate the oscillation of the VDS system and to optimize the winch speed, while it’s launching, to reduce the oscillation. This approach relies on the differential equation of motion for the VDS system, taking into account a variable rope length and the ship induced excitations at the deployment point of the VDS. These excitations are calculated in the time domain using “E4-ROLLS”. To enable operations in conditions with higher significant wave heights, the method integrates the principle of swing damping along with a CHWARISMI optimizer to determine the optimal damping and winch speed for every situation. Initial results indicate that this optimized VDS system can be used effectively at significant wave heights up to one meter higher than previously feasible. This advancement enhances underwater detection capabilities and increases operational safety and efficiency for vessels in challenging sea conditions.Publicationtype: Conference Paper20