Editorial

It is a privilege to be able to produce this special issue of the International Journal of Aeroacoustics in honor of our mentor Professor Dennis K McLaughlin. Dennis is an outstanding researcher in the field of jet aeroacoustics, a talented academician, and a valuable administrator. He became an AIAA Fellow in 2005, and he was the AIAA/CEAS Aeroacoustics Award winner in 2010. The award citation succinctly describes his contributions: “For pioneering contributions in experimental acoustics, particularly measurements of noise generated by large-scale structures in supersonic jets, and for leadership in aerospace engineering education.” Additionally, he has made contributions in optical measurement techniques, noise generation from turbomachinery, compressible shear layer mixing, and wind turbine noise generation. His experimental work has increased fundamental physical understanding in these areas and has been used as the basis for model validation and for varied theoretical efforts. He has authored or coauthored numerous archival papers on these topics. Even after a formal “retirement,” he is still actively working on the life-long passion of jet noise reduction. However, all of these contributions and accomplishments represent only one side of Dennis’s professional life. He was also the Head of the Department of Aerospace Engineering at the Pennsylvania State University for 18 years, and an academician who taught many courses on experimental fluid dynamics and aeroacoustics. He has supervised numerous Postdocs, Doctoral and Master’s theses, and many undergraduate level research projects. Experimental aeroacousticians are a special breed, and Dennis’s students are playing major roles in many aerospace companies, government agencies, and various universities around the world.

Dennis was our thesis advisor, and as with any graduate student/advisor relationship, it had its ups and downs. However, in the end, we benefitted from a great learning experience. Jay recalls thoughtful advice from Dennis like “I can tell you how to do research rather than what to do” and “use your head for analyzing than memorizing.” Anyone who has come across Dennis knows about his organization skill; he is a “man with a plan.” In fact, the planning skill is the first thing that every student needed to learn. For non-native English speakers, like Jay, Dennis’s choice of some words was mysterious until one day the department secretary revealed the source: ice hockey, a sport Dennis regularly played. In fact, Mike remembers getting help from Dennis on a few Saturday mornings at the lab where Dennis would show up in sweatpants after having played hockey. For Mike, meeting the enthusiastic and genuine Dennis on a campus visit was what “sealed the deal” in his mind to attend Penn State. That enthusiasm was certainly on display a few years later when the jet noise team, led by Dennis, rented a U-Haul and drove hundreds of miles to dismantle and load up several key jet noise laboratory components from another university (with permission of course).

This issue starts with a great biographical article on Dennis by his close collaborator Professor Phil Morris. In addition to Dennis’s academic path and research career, the article sheds a lot of light on his personal life, including his love of ice hockey, and presents a collection of interesting photographs. We have organized the rest of the articles in chronological order of first association with Dennis. Among the contributors to the issue, Chris holds the distinction of the earliest association with Dennis, followed by Khairul and Dimitri. There are four papers by his graduate students (both former and current) and their associates interspersed among two papers by his colleagues, Mo and Thomas, and their associates. The articles span a wide range of topics: jet noise experimentation and modeling, modeling of combustion noise, measurements and simulations of fan noise, algorithm development for computational aeroacoustics, and an article on the aeroacoustics of space vehicles. We want to sincerely thank the authors for their contributions, the reviewers for their assistance, the Editor, Ganesh Raman, for giving us the opportunity to put this special issue together, and most importantly, Dennis. Dennis is a passionate researcher, a skilled mentor, and a great friend. Working on this issue brought back memories of years of association with Dennis. It is an honor for us to be the guest editors of this special issue.