Mehdi Pourmostafa - Ph.D. at Dept. of Marine technology, Amirkabir University of Technology, Tehran, Iran
Jafar Jafarpour - Ph.D. Candidate of Industrial Management, Islamic Azad University, Science and Research Branch, Tehran, Iran
Mohammad Ghasemieh - Master Degree at Dept. of Marine technology, Sharif University of Technology, Tehran, Iran

The current paper presents a three-dimensional unsteady numerical model of potential flow for predictingmain characteristics of a twin skewed B-series propeller propulsion system. The proposed method utilizesconstant source and dipole intensity distribution over the blade panels. Combining BEM with timestepping method facilitates the possibility of generating and rebuilding the propeller wake in each timestep, which gives the designers the ability to simulate burst starting of a propeller which is a completelyunsteady phenomenon. Applying a multi-body solver with separate coordinate systems is a particularnovelty of this work. Accordingly, each propeller rotates in its own coordinate and its effect is applied onthe other propeller and its wake shape. Comparison of the current results with existing experimental datashows good compliance. As a result of investigating the twin propeller system, wake sheet rollup pattern ofeach propeller over time, is presented. By performing a set of parametric simulations, it is demonstratedhow the hydrodynamic performance charts (including KT, KQ, η) gradually change due to differentpropellers' spacing. Considering the low calculation time of BEM, these charts can be widely used forpreliminary designs purposes

Twin propeller system, Boundary element method, Time stepping method, Wake sheet generation,Multi-body simulation