May 2, 2024
Ahmad Reza Kohansal

Ahmad Reza Kohansal

Academic Rank: Assistant professor
Address:
Degree: Ph.D in Marine Engineering
Phone: 07731222181
Faculty: Faculty of Engineering

Research

Title
Simulation of maneuvering of high-speed planing hulls: Extension of available models
Type Thesis
Keywords
شناورهاي پروازي، مانور، مدل سازي، كوپل قوي حركات
Researchers Ahmad Reza Kohansal (Primary advisor) , Abbas Dashtimanesh (Primary advisor) , Saeed Jaamei (Advisor)

Abstract

In recent decades planing hulls have been widely used for military, recreational and supply porposes. Maneuverability and stability of these vessels are critical considerations that should be taken into account during the early stages of design. Present study extends the simulation of maneuvering of high-speed planing hulls in three steps. First step is assigned to present CFD (Computational Fluid Dynamics) simulations, which are aiming to evaluate the performance and running attitude of a planing hull in a calm-water condition. The key differences between these models are the ways they use to compute the turbulent flow and simulate the motion of the vessel. Two different frameworks including k-ε and DES (Detached Eddy Simulation) methods are employed to model the turbulence behavior of the fluid motion of the air-water flow around the boat. Motions of the rigid solid body in the fluid domain, are numerically modeled by using two approaches, including morphing and overset techniques. Numerical observations suggest that a DES model can modify the accuracy of the morphing mesh simulations in the prediction of the trim angle and resistance, especially at high-speeds. The overset method overpredicts the resistance force. This overprediction is caused by the larger vorticity, computed in the direction of the waves, generated under the bow of the vessel. In the next step of the current study, asymmetric CFD tests of a planing model are performed to provide a deeper understanding of planing hulls' maneuver behavior. Compression between CFD and experimental results indicates increment in roll angle (greater than 10 degrees), resulting in a significant decrement in resistance force of the boat. In this condition, the stagnation angle on the heeled side becomes larger than its value on the other side and as a result, the Non-dimensional dynamic pressure rises and the skin friction coefficient falls at this part of the boat. Furthermore, evaluating the velocity and vorticity f