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Investigation of Hydrodynamic Interaction between a Squat Submarine Operated behind a Ship

Sarraf, Samyar | 2023

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  1. Type of Document: Ph.D. Dissertation
  2. Language: English
  3. Document No: 56402 (58)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Abbaspour, Madjid; Mohtasham Dolatsahhi, Kiarash; Sani, Mahdi
  7. Abstract:
  8. This research investigates the hydrodynamic interaction of a squat submarine operating behind a ship in various wave and resistance experiments for towing and self-propelling arrangements. A one-tenth scaled captive model of a 0.625 m squat submarine is constructed along with a 1.5 m Fridsma ship to perform 116 unique experiments in a 4×6×400 m3 tank located in a towing tank center. The submarine is a new midget-submersible, of Apam-Napat SMSD type, with an L/D ratio below four. The cable is specified, regarding its weight per unit length, using a scaling method introduced in this research. Wave and resistance tests are performed for various 2D relative lengths and depths at short-distance conditions. A wave of 0.1 m height and 1.5 m wavelength is used in the wave tests, and different operational velocities of 0.5, 1.0, and 1.5 m/s are used in the resistance tests. In each case, drag and heave forces are recorded and presented for the vessels using non-dimensional units. Finally, outputs are extended to develop 2D contours to estimate the interactional forces in the full domain. Results show that the collision of surface waves creates a critical zone behind the ship around the 0.75D depth where the submarine drag forces are increased by up to 177% and 41% compared to interaction-free conditions for the towing and self-propelling arrangements respectively. In addition, comparing the towing mechanism to self-propelling operations shows that the towing effect dominates vessel interaction, increasing the drag forces by up to 240% when the ship tows the submarine. The drag forces of the submarine-ship system differ by up to 16.8% between the numerical and experimental evaluations. The findings of this study help optimize the submarine-ship arrangement for site operation, launching, and recovery of the submarine from the ship. It is suggested to avoid locating the submarine in the defined peak zone because of the higher drag forces experienced in that region. Additionally, during submarine transportation to the desired locations, it is suggested to locate it at a short horizontal distance behind the ship in order to lower the combined drag forces on the submarine-ship system. Further, due to the large force variations in the defined critical zone, it is suggested to implement a warning in the submarine control system when approaching this area in order to prevent operational disturbances
  9. Keywords:
  10. Cables ; Towing Tank ; Tow Submarine ; Squat Submarine ; Submarine-Ship Interaction ; Hydrodynamic Performance Curve

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