*Editorial* **Selected Papers from the Sixth International Symposium on Marine Propulsors**

**Kourosh Koushan 1,\* and Sverre Steen <sup>2</sup>**


Received: 14 April 2020; Accepted: 14 April 2020; Published: 1 May 2020

**Keywords:** propellers; waterjets; unconventional propulsors; cavitation; noise and vibration; numerical methods in propulsion; propulsor dynamics; propulsion in seaways; propulsion in off-design conditions; energy saving devices

This Special Issue is following up the success of the latest Symposium on Marine Propulsors (www. marinepropulsors.com, smp'19) by publishing extended or improved versions of the selected papers presented at the symposium. This issue also includes new original contributions. The symposium smp'19 was the sixth in a series of international symposiums dedicated to the hydrodynamics of all types of marine propulsors. The next symposium in this series will be held in China in May 2021. This Special Issue comprises 17 excellent papers originating from the symposium [1–17] and two outstanding new papers [18,19]. The papers disseminate state-of-the-art numerical and experimental research results on marine propulsors and marine renewable devices.

Marine propulsors are key components of the many thousands of ships operating in oceans, lakes, and rivers around the world. The performance of propulsors is vital for the efficiency, environmental impact, including the impact on marine fauna, and safety of ships. Propulsor performance is also important for crew and passenger comfort. New types of propulsors with electric drives, flexible blades, and rim driven propellers require new knowledge and improved tools. Innovative main or auxiliary propulsor types, using renewable energy from waves or winds, are also being commercialized. The improvement of computers and computational fluid dynamics creates new opportunities for advanced design and performance predictions, and new instrumentation and data collection techniques enable more advanced experimental techniques. This Special Issue of the *Journal of Marine Science and Engineering* is devoted to bringing the latest developments in research and technical developments regarding hydrodynamic aspects of marine propulsors, to the benefit of both academics and the industry.

Prof. Dr. Kourosh Koushan and Prof. Dr. Sverre Steen

Guest Editors of "Selected Papers from the Sixth International Symposium on Marine Propulsors"

**Author Contributions:** K.K. wrote the editorial. S.S. contributed to and reviewed the editorial. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflict of interest.

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