---

In the present research, numerical simulation of the characteristic chart and steady-state Wakefield flow around a marine propeller is conducted. Solutions were performed using the open-source OpenFOAM software and the steady incompressible simple-Foam solver. The gradients were calculated using the linear Gauss algorithm, and the pressure equation was solved with the multi-grid method. In this research, characteristic chart simulation of the propeller was carried out for the entire operational conditions and the effect of using Realizable-k-ε and k-ε-v^2-f turbulence models on the results was investigated. The results were found to be in good agreement in all conditions except for the near bollard region. In this region, the propeller inlet angle of attack severely increased, and the two equation model predicted the thrust coefficient with 24% error, while implementing the four equation model significantly developed the results and decreased the error to 5%. The wake region parameters were also investigated in the numerical simulations at different longitudinal and radial cross sections behind the propeller which showed good agreement compared with the available experimental data. Wake region investigation showed that the flow behavior in downstream cross sections is similar to the corresponding upstream section with smaller variation ranges and for the swirling flow behind the propeller, the maximum and minimum angular position of the wake components rotates. The obtained results also show that the wake axial velocity component deviation is extremely large at the blade tip.

---

In the present study, the wake flow field of a submarine model was investigated experimentally in a wind tunnel. The experiments were conducted to determine the effect of the location of control surfaces on the wake inflow to the impeller of the submarine. In order to investigate the effect of the location of control surfaces as the most important innovation of the present study, the aforementioned surfaces were installed in three longitudinal positions X/L=0.89, 0.92, 0.95 on the heel of the submarine model, and the wake flow was measured at position X/L=1.7 and the Reynolds number 6*10^5  by a five-hole probe and a hotwire anemometer. Finally, the longitudinal position X/L=0.95 was selected as the optimal location for the stern planes to improve the wake inflow to the impeller in terms of reducing its total area and the least amount of turbulence and non-uniformity. The results obtained during this study showed that arriving of the holder basechr('39')s wake to the stern area increases ​​the area and average velocity and subsequently reducing the non-uniformity of the wake flow.

---

New generation of wind turbines, in comparison to the old versions, have been designed with colossal blades to produce larger amount of power output. However, this has led into some unpredictable challenges including their construction procedure and expenses and particularly blades’ transportation. To overcome these issues, multi-rotor wind turbines have been suggested. Aerodynamic performances of such turbines have been previously assessed by other investigators. However, the wake characteristics of these turbines have been less studied. The focus of the present research is on the assessment of these characteristics, which are crucial in the process of any wind farm design. For this purpose, wake flow of a small three-rotor wind turbine is numerically simulated using computational fluid dynamics. A numerical simulation has been conducted for a single-rotor wind turbine and three-rotor small horizontal axis wind turbine with the angle of 180^⸰ arrangement. The results of single rotor wind turbine indicated that far downstream wake extended up to 8D, with Jensen-Gaussian model can be better predicted. The comparison between three bladed wind turbine and the results of wake models for the equivalent turbine showed that because of wake interactions in the downstream of the rotor, the loss of turbulent kinetic energy and recovery of the stream speed will be faster. As a result, in the wind farms, the turbines in closer distances around 4D of the equivalent signle-rotor wind turbine can be installed.