Special Issue on Aerospace and Naval Propulsion

Aerospace and naval propulsion involves a broad variety of flows and scientific areas than can be categorized in many ways, the most obvious one being based on the type of fluid: water or air. However, one slightly different and interesting distinction between the various problems of fluid mechanics in this domain is to consider compressible versus incompressible flows. While the first category includes all problems related to supersonic propulsion and reactive flows, the second one refers not only to hydrodynamic issues, but also to low-speed aerodynamic propulsion where temperature and compressible effects can be ignored. The latter pool of problems can also naturally include liquid flows with a dilute gas phase, like cavitating flows, although this choice is of course questionable, since cavitation generates compressible effects.The present Special Issue of the ASME Journal of Fluids Engineering is a collection of ten research papers focused on this type of “incompressible” problems related to aerospace and naval propulsion. These papers have all been selected through the initial review process conducted in the preparation of the 17th ISROMAC conference, which was organized on Maui in December 2017. ISROMAC is the International Symposium on Transport Phenomena and Dynamics of Rotating Machinery, which is organized every two years in Hawaii. It has a long history of scientific exchanges in all areas related to rotating machinery, and the 16th and 17th Symposia focused on cross-disciplinary works, in all scientific areas covered by the 30 forums of the conference. The objective was to attract contributions that would not be systematically connected to rotating machinery, in order to obtain presentations related to other applications or fundamental works, and therefore promote new ideas and future progress.ISROMAC 17 has been attended by more than 270 researchers from 29 countries in America, Europe, Asia, and Oceania. A thorough review process of all full papers has been conducted, which has resulted in the selection of 47 papers to be published in four Special Issues of renowned journals, after a second step of reviews specific to the different journals. It is a great pleasure for me to introduce the works included in the present Special Issue, which are related to:“Effect of non-uniform flexibility on hydrodynamic performance of pitching propulsors”I would like to thank the Editor of the ASME Journal of Fluids Engineering, Francine Battaglia, for her initial acceptance of this idea and her continuous support, the Editorial Office, Amber Grady-Fuller, and the Production team at the American Society of Mechanical Engineers for their assistance during the course of this Special Issue publication. I also would like to thank the authors of the papers for their efforts in preparing these contributions, and all reviewers for their help to improve the papers and identify the most suitable contributions for this Special Issue.