August, 2019

Dear Allan、

I had heard a lot about you from your former student, Dr. Oki Furuya, before I first met you in 1981. What a respect- and lovable educator you are! My admire to you was implanted prior to the visit by Oki, one of the undergraduate students whom I taught at Mechanical Engineering Department of the University of Tokyo around 1965.

You and I enjoyed sharing the same research interests in dynamic fluid forces on oscillating pump impellers in 1980s and early 90s. However, researches in CalTec and in UTokyo started quite independently; yours triggered by vibration trouble of turbopumps of Space Shuttle main engine, ours by that of high speed boiler feed pumps for supercritical thermal power plants. I was not aware of your research until Dr. T. Iino, Mechanical Engineering Research Laboratory of Hitachi, told me what he saw after he returned from NASA Workshop on Rotordynamic Instability Problems in High Performance Turbomachinery held at Texas A&M Uni. in 1980. Thanks to his introduction of our research at the workshop, we got invitation to submit a paper belatedly to the Conference Publication of the Workshop, NASA CP 2133.

We started theoretical and experimental study of lateral fluid forces on whirling centrifugal impellers around 1978 with close cooperation with Hitachi. Dr. H. Shoji of our group worked intensively on theory and completed his first contribution in 1979. We sent this paper to NASA and could join the Workshop on publication.

We completed our test rig for forced whirling motion in 1980 and continued experiments for 10 years with stepwise improvement of methods and devices. The first report on experiment was presented at ASME Winter Annual Meeting of 1981 at Washington, DC. On the way back home, I stopped over in Pasadena and met you at your office (photo below).

In 1990 we reformed the rig to forced precession motion, and continued experiment of force and moment on tilting impeller till my retirement in 1992. When I retired from UTokyo, I could not find successor of the research in my laboratory. Prof. Yoshi Tsujimoto of Osaka University, one of right-hand men supporting your research, appeared then as a Savior. He kindly offered to continue our research at his laboratory. The property registration of the whole test rig and accessories were officially transferred and moved to Osaka University. I am very glad and happy that Yoshi had produced a lot of contributions using the rig till his retirement in 2013. I hear also the test rig is still alive and active today under the new successor, Prof. K. Sugiyama.

 The test rig is now 40 years old. Its basic structure remains unchanged but measuring methods and devices have been continuously improved and renewed. The test rig is surely worth receiving Achievement Award for long years of service!

 Two researches at CalTec and UTokyo on fluid forces on oscillating impellers started independently, but got together finally by merge and acquisition by Yoshi. It is quite a happy end!

 Allan, I have many reasons to thank you. First of all, you raised many students from Japan to potential researchers and engineers, Oki is of course one of them. You were also a valuable mentor to numerous visitors from Japan, from academia as well as from industries, and gave them strong influences and incentives. Yoshi has been a good mediator to connect them to you. The conferment you received with the Order of the Rising Sun, Gold Rays with Neck Ribbon in 2012 was a big joy for all Acosta fans in Japan.

 You have been showing a beautiful example of sincere way of life as an educator, scientist and engineer, last but not least, as a human . We all Acosta fans are praying for your continuing wellbeing. Please show us good example of longevity for years to come!

With heartfelt regards,

Your

Hideo Ohashi

Prof. Emeritus, University of Tokyo (88 years old)

Office looked like a showcase of impellers.

Held at Hyatt Regency Hotel, Shinjuku, Tokyo.