Hello everyone:

Like all of you, I was saddened to learn of Allan’s death.  He taught me a great deal, probably much more than he realized, about research, fluid mechanics, writing, and thinking, all of it informally.  He was also kind, for he let me explore a topic neither of us knew anything about, namely, non-Newtonian fluid mechanics.  All of his guidance came to the fore when I wrote a manuscript based on my PhD research.  It was a good paper, as it turned out, and he helped with the writing, but he thought that his name did not belong on the manuscript, saying that the work was all mine. I explained how much I had learned from him, as indicated above, and how much he had contributed to the paper in that way.  Happily, his name is there.  

It was part of the academic culture in those days — the sixties —  that I had to persuade my adviser to be a co-author. 

David James

It was a shock to hear of the passing of Allan; my friend, teacher and collaborator. While he had been ailing recently his passing leaves a deep sadness and it signifies the end of a very special era in my life. I met Allan on campus in 1960 when I arrived at Caltech as a foreign graduate student. He became my doctorate supervisor that year and that began a lifetime of camaraderie and friendship. Allan was unique in that he was able to slip transparently between being a teacher, a mentor and a friend thereby bridging the full spectrum of a close and enduring relationship. So many memories come to mind of this whether it was taking his classes, working with him in the lab, discussing some technical problem, critiquing my doctoral thesis, sailing or spending time with our families at his home in Altadena. He was always there to provide guidance, support and genuine personal interest. With great fondness, he always reminded me that I was his first doctoral student. I spent a couple of years after graduating as a Research Fellow working with him on several Navy and NASA contracts working in the Hydrodynamics laboratory in Guggenheim. We would spend many hours together on these programs but always go sailing on Wednesday afternoons in the “Wet Wednesday” racing series or race in some other regatta. Anchoring off Catalina on weekends to go scuba diving or fishing for abalone was another of his favorite past-times. 

Such life time recollections can never be replaced and will always be with me as i think of Allen. He changed my life and many others. To all his former students and colleagues and especially to his children Alison and Joey, who spent so much time with our family, and to Annette, our sincere condolences. We all will miss him!

Richard Wade

Dear all,

I would like to join you mourning for Allan’s death. To me the new is inspiring deep sadness but also a feeling of serenity, as his has been a life of great accomplishments and recognitions by those who most closely knew him. Meeting Allan at Caltech 40 years ago when he became my supervisor was a very fortunate step in my life, since I ended up working with both a great teacher and a master of life. He has been a very special person to me for his enthusiasm and imagination and for his ability to motivate and direct a group that led research in his field worldwide for more than a generation. Allan always exercised the necessary leadership with wisdom, generosity, consideration and respect for the his younger collaborators. I owe him the “can do” attitude and the notion that “If everything seemed under control, you are just not going fast enough”, which hopefully inspired my later academic career. He once said that his objective in life was “trying to make things better”, the distinctive feature of a true gentleman. He fully succeeded. In retrospective, I was very happy and honored to realize that, while working with him, we had become friends, a friend I will never forget.

Luca

Luca d’Agostino

Hi All:

I concur with everything everyone has said about Al.  He was a great educator, mentor, friend and gentleman.  I had the pleasure and honor not only to have studied under him but worked closely along side him for more than a decade when he was consulting with the company where I was employed. He definitely had a positive influence on me and the other engineers who had the privilege of interfacing with him.  My wife and I have many fond  memories of having Pat and Al over to our home for social functions.  He will be sadly missed but not forgotten.

All the best,

Khoon Ooi

Kean Khoon Ooi

I have received the itinerary and the official report of Allan’s visit to Japan in 1986, as well as many pictures, from Prof. Akira Shima of Tohoku University, Institute of High Speed Mechanics at that time and Institute of Fluid Science now, through Prof. Yuka Iga. The reports are available from:  [Itinerary] [Report]. Prof. Shima stayed with Allan long time before and arranged the visit. He is happy that he was appointed as a Fellow of ASME, recommended by Allan.

The documents remind me of the emergency phone call from Prof. Ohashi, on March 23, 1986. Allan’s flight JL61, scheduled to land at Narita, was diverted to Osaka because of heavy snow at Narita. All roads to Narita were closed. Prof. Ohashi was concerned that Allan could be kidnapped in the cabin till Narita is reopened and asked me to rescue him at Osaka. We were happy to welcome him as the first guest to our new apartment. He traveled to Tokyo by Shinkansen on the next day and could fit into the original schedule.   

Another memory is associated with his invited talk at the Cavitation Symposium. To show the cavity inception in the laminar separation bubble, he planned to use a high-speed film. However, the meeting site did not like him to use their movie projector：they were afraid of film jamming. Since the film was the key of his talk, we negotiated with the site saying that we will take all the responsibility in case of jamming, although we were not sure how we could. His talk was perfect: it proved that “take responsibility” is a key phrase in Japan.

The latter part of the report was written by Allan himself and I now learned from it that motivation and preparedness is very important for us engineers and researchers. He found that engineers in Japan are requested to be a specialist not only in a field but sometimes requested to lead a group in another quite different field. He argues that this might be very stressful not only for the engineers but also for their managements.  The flexibility he found might be a strong point of Japanese engineers and we might need to cultivate it also in the future.

Thank you Allan, for your careful observations and warm suggestions!!

Yoshi, based on material from Prof. Akira Shima, September, 2019

Allan is my most influential mentor and set my research style after my stay with him in 1983(Oct)-1984(June), as a visiting associate. On the day of my arrival, he said that I might go to Santa Monica beach everyday if I wished, but if not I might work on a topic of rotordynamics. I knew that this interesting problem was studied also by Prof. Ohashi of University of Tokyo and, to tell the truth, I did not want to be his competitor. By comparing their treatments, I found that more fundamental approach was used at Caltech and I decided to extend it for realistic cases. After developing fundamental equations, I proposed Allan to carry out calculations after returning to Japan and spent the latter half of the stay studying cavitation under Allan’s guidance.

Although the results of calculation could simulate the experimental results qualitatively (convenient word!!), the magnitude was smaller than the experimental results. Instead of being disappointed, Allan kindly built and tested a 2D impeller which is assumed in the theoretical model and showed that the theory can simulate the magnitude as well!!  It was eventually found that the elementary flow fields developed for the rotordynamic problem could be conveniently used also for the analyses of rotating stalls in centrifugal impeller, vaned and vaneless diffusers.

Just after my return to Japan, Allan visited Japan to attend the first Cavitation Symposium at Sendai. Although I was not involved in cavitation at that time, he advised me to attend the symposium since I would be involved in the field. Before the Symposium he visited many universities and institutes and reported me about his impression. Perhaps on another visit to Japan, he was interested in visiting Matsue, on the other side of Hiroshima, which is not very familiar to foreign tourists. We drove there from Osaka and visited many marinas and small fishing villages as well. On the trip and other occasions with him, I learned from Allan about important attitudes for a researcher such as “make problems as simple as possible”, “nothing is more practical than a simple theory (said by someone else?)”, ”keep good balance between theory and experiment”. I tried to get closer to them throughout my life.

Allan developed a linear partial cavity model on a flat hydrofoil [1] and has shown that the cavity length is a function of a parameter (cavitation number)/(incidence angle). It was found that this parameter is important also for the occurrence of various types of cavitation instabilities. He also made the first detailed experimental study of cavitating inducer [2]. He reported about cavitation instabilities such as cavitation surge, alternate blade cavitation, and rotating cavitation. They are found also in modern turbopump inducers and extensive efforts are being made to avoid them.

Although my stay was only 10 months, he introduced me to many students who graduated before and after my stay, on my later visits. I feel very relaxed whenever I find Acosta family member in in various meetings all over the world. It is interesting that the stay with Allan gave me opportunities of getting familiar with Japanese important people, who are very busy and would have no time to talk with me in Japan. The first is Prof. Ohashi. He gave me his rotordanamic test facility on his retirement!! This is still working at Osaka University. The second is Dr. Kamijo, Dr. Yamada, and Dr. Shimura from National Space Laboratory, who introduced me to the interesting field of cavitation instabilities in turbopumps for rocket engines. In solving the problem, Allan’s theoretical and experimental works including those mentioned in the last section were very helpful. So, they invited Allan many times to obtain his suggestions. We collaborated with Dr. Furuya, a student of Allan, for the fundamental study of unsteady cavity response to disturbances.

Thus, I actually got deeply involved in cavitation as Allan predicted at the first Cavitation Symposium.

I am always asking myself how Allan would think, whenever I encounter new problems. I am now wearing the T-shirts and listening to the music both from Allan. So, Allan is always with me and I wish his quick recovery.

References

[1] A. J. Acosta, (1955) “A Note on Partial Cavitation of Flat Plate Hydrofoils”, California Institute of Technology Hydrodynamic Laboratory Report No. E-19.9.

[2] Acosta, A.J., (1958). An Experimental Study of Cavitating Inducers. Second Symposium on Naval Hydrodynamics, Hydrodynamoc Noise, Cavity Flow. August 25-29, Washington D.C., ACR-38, 533-557.

Yoshi Tsujimoto, August, 2019

I was incredibly fortunate to have enjoyed Allan Acosta as a teacher, a friend, and as a mentor.  When I was a young post-doc back in 1969, I was lucky enough to be assigned an office in the von Karman building next to an office occupied by Allan. From the start our interests and personalities drew us naturally together and so began 50 years of friendship and the most fruitful collaboration of my time.  I recognized early that Allan was a truly remarkable engineer, one of those rare individuals as talented in synthesizing machines and experiments as he was in analyzing phenomena.  I remember vividly the first time we flew back to Huntsville, Alabama in the 1970s to talk to NASA about a possible research program. The aura of von Braun and the Peenemunde kids still hung heavy around the Marshall Space Flight Center and the Redstone Arsenal and the huge test facilities gave the place a futuristic dimension. The Space Shuttle was then just a paper idea and the planned power density of the main engines were scary with all kinds of possible consequences.

That visit was the beginning of a long and very productive period in Allan’s career as well as my own – the beginning of a long sponsorship by NASA and a marvelous collaboration between Allan and I. Together we created a number of remarkable experimental facilities – facilities that in later years spawned copies in many institutions around the world – from Osaka, Japan, to Pisa, Italy, and many other places. But none that equaled the originality and productivity of  our “pump lab” in terms of the quality of data, new information and new concepts. That data and information are now used worldwide throughout the rocket and pump design industries.

Several generations of graduate students as well as numerous undergraduates contributed to and were witness to those events.  Allan was an inspirational teacher and along with all those students I learnt from him both the art and science of teaching. He made a fundamental contribution to whatever later success I enjoyed in the classroom. At the end of my teaching career, the students in my fluid mechanics class videotaped my lectures and, when I look at those tapes, I see Allan’s technique and even his gestures unwittingly reproduced.

But we also had great fun away from campus for we were both adventurers at heart. Allan taught me how to endure being hoisted to the top of a mast on a sailing boat in the middle of a gale and  how to disentangle the jib hoist prior to the start of a sailing race. How to swim/snorkle under the same boat to clean off the barnacles that allegedly were preventing us winning the race. How to dive down to the bottom of a kelp bed to pry abalone off the rocks with a tire iron and then to tenderize the meat with a piece of driftwood. And many more invaluable skills.

May the force be with you, my friend.

Christopher Earls Brennen, July 2019.

An interview in four sessions, in April and May 1994, with Allan James Acosta, Richard L. and Dorothy M. Hayman Professor of Mechanical Engineering, emeritus, in the Division of Engineering and Applied Science [LINK]

Dear Professor Acosta,

Upon hearing that you are gravely ill, I find myself remembering fondly of the interactions that I had with you during my years at Caltech.  Beyond teaching us how to think and analyze fluid phenomena, I really appreciated learning that people in competitive professions can be friendly and supportive.  Those years led me to my lasting friendship with Tom Berto with whom I share many memories of your undergraduate courses.  You also direct me to attend MIT for graduate school, which in turn led me to my wife of 30 years.

Do you remember the time that Tom and I rode our bicycles down to Seal Beach from Pasadena and dropped in on you on your boat?  It was very nice of you to host us onboard for the visit.

In the last year or so, I have been fortunate to start enjoying retirement life.  It is with regret that I was too busy with work and life to visit you.  While I started my career helping Volvo produce aerodynamically efficient cars, I eventually shifted my focus to electrified drive train technologies.  Although I could not talk to you about it at the time, I like to think that you would approve the way I engineered to cool the lithium-ion battery modules in the 2003 EV that my team built at Volvo.

Thank you professor for preparing me for such a fulfilling life.

Yours truly,

Ichiro Sugioka

Class of 1983

Dear Doctor Acosta –

I apologize for taking so long to write.  A friend and I, on a recent Sierra backpacking trip, discussed our favorite and most significant college professors.  In my case, you are both of those. 

At Caltech, I had the unalloyed pleasure of learning fluid mechanics from you in my junior year, and heat transfer from you in my senior year.  Those two classes began what has become my lifelong love affair with mechanical engineering – and let into an ongoing career of 34 years.

I appreciate the wisdom and the inimitable, graceful style with which you taught those classes.  At times, I was transfixed, and at all times, I was learning.

Over the years I’ve been able to apply that experience in my career as a mechanical engineer.

You also provided direct and clear guidance to me at the end of my senior year, in regard to the choice between starting my professional career immediately, or continuing on in academia for a Master of Science degree.  As you put it: “You can work for the rest of your life.”   I remained a student for a while longer, attained my Master of Science in Mechanical Engineering at UC Berkeley, and never regretted any aspect of that experience for a moment.  I appreciated, then and now, your thoughts at that crucial time in my life.

I thank you, sir.   

Most sincerely, a devoted former student –