Alfred Ritter

(University of Alabama in Huntsville, U.S.A.)

The grand memorial meeting to commemorate the 90th an­niversary of the birth of the late Professor Y.H. Kuo is a wonderful tribute to his memory. I am honored to contribute some brief words to reflect on my own memories and relationship with him.

I first met Professor Kuo in September 1948 when I entered the Graduate School of Aeronautical Engineering at Cornell Uni­versity in Ithaca, New York as a Ph.D. student. The School had been founded two years earlier under the leadership of Professor W. R. Sears, and Kuo was one of the original faculty members. He taught me courses in viscous fluids, boundary layer theory and tur­bulence. Moreover, he became my research advisor as I addressed the problem of the reflection of shock waves from boundary lay­ers. These were the early days of theoretical work on shock wave-boundary layer interaction. It was also the time in which Professor Kuo worked on perturbation methods for treating laminar bound­ary layers. His research in this area led to his famous paper in 1953 in which the well-known Poincaré-Lighthill-Kuo(PLK) tech­nique was established. A description of this technique followed in a lengthy review paper by H.S. Tsien (1956).

Professor Kuo taught me a number of technical subjects and guided my research. Most important, he taught by example. He attacked the difficult problems in aerodynamics and fluid dynam­ics and set for himself, his students and co-workers the highest standards of integrity. He found unacceptable the research worker who was, in Kuo’s words,“a mathematician without a soul”. That description was given to those individuals who, through mathemat­ical dexterity, produced elegant solutions to problems which yielded non-physical results in limiting cases.

Professor Kuo could project a stern presence. However, in my relationship with him, he exhibited a father-like quality. We had adjacent offices in the old Aero School building at Cornell, and he would wander in frequently to peer over my shoulder to see, pick up, and read the sheets of paper I had written. We argued frequently about technical points, but that was his approach to teaching me. I remember well the time he became very impatient with me when I couldn’t write down immediately the general solution to a par­ticular type of partial differential equation. In an expression of frustration, he exclaimed that he knew the solution when he was just eighteen years old.

During student days in Ithaca, my wife, Joyce, developed a warm friendship with Kuo’s wife, Li Pei. Consequently, the Ritters and Kuos met freqrently at various Aero School social functions. In September, 1951, I received my degree, and we departed for Washington D.C.

After Ithaca, we saw the Kuos several times. I visited them in Pasadena in 1953 when Kuo was on sabbatical leave at Cal Tech working with the distinguished scientist, H. S. Tsien. The Kuo family, now including their young daughter Janie, stayed with us during their visits to Washington in 1952 and to Chicago in 1956. That last visit occurred while Kuo and his family were en route to China. Kuo had a strong sense of patriotism and was returning to serve his country.

Back in China, Kuo was re-united with Professor Tsien. Now, Kuo’s influence expanded from that of an individual scientist to one as Deputy Director of the Institute of Mechanics, Academia Sinica in Beijing. In addition, with Professor Tsien, he was instrumental in setting up the China Aerodynamic Research and Development Center (CARDC) in Mianyang, Sichuan as a national center for aerodynamic research in China.

In early 1998, the China International Culture Exchange Cen­tre, as part of their academic exchange program, invited me to visit China in June of that year. I had not been to China previously, so this was a welcome opportunity for me to see the research institu­tions that were started some thirty and forty years ago. Thus, fifty years after I first met Professor Kuo, and forty-two years after I last saw him. I had the pleasure of giving several lectures on aero­dynamics at the Institute of Mechanics in Beijing and at CARDC in Mianyang. In many respects, this was a period in which I re­newed our friendship in spirit. In addition to the lectures, however, I had the good fortune to see once again Professor Li Pei. She and I talked at length about old times, old friends and good memories. Finally, to make my visit complete, Li Pei took me to see my old and very good friend, Dr. H.S. Tan. As fellow students at Cornell, Tan and I shared an office and later worked together for many years in Ithaca. I had not seen him for eighteen years. Clearly, my time with Li Pei and Tan was cause for celebration of a long delayed reunion.