Philip Saffman


The Jewish Chronicle - - Obituaries -

AWORLD EX­PERT on pat­terns of fluid move­ment, es­pe­cially ro­ta­tion or ed­dies, Pro­fes­sor Philip Saffman used his skill in ap­plied math­e­mat­ics and aero­nau­tics to solve and avoid cer­tain types of air crash, writes John Fisher.

The son of Sarah and Sam Saffman, a well-known Leeds so­lic­i­tor, he broke the fam­ily mould by not join­ing the fam­ily firm, un­like his two broth­ers, one of whom sur­vives him.

Ed­u­cated at Round­hay, Leeds’ premier gram­mar school, Philip shone aca­dem­i­cally, gain­ing hon­ours in some 10 sub­jects in Higher School Cer­tifi­cate, the equiv­a­lent of to­day’s A-Lev­els, when he was just 15.

His fas­ci­na­tion with wa­ter emerged while on fam­ily hol­i­days. He would sit on the beach for hours ob­serv­ing the move­ment of the waves.

At 16 he took a gap year and went to stay with rel­a­tives in Bal­ti­more, re­turn­ing to Eng­land to do his na­tional ser­vice. A year later the RAF re­leased him as “some­thing of a prodigy”. He en­tered Trin­ity Col­lege, Cam­bridge, where he gained his bach­e­lor, mas­ter and doc­toral de­grees.

In 1954, he mar­ried Ruth Arion, sis­ter of a for­mer class­mate at Round­hay. In 1958 he was ap­pointed as­sis­tant lec­turer in ap­plied math­e­mat­ics at Cam­bridge and the cou­ple moved to the city.

Af­ter teach­ing the sub­ject at Cam­bridge and at King’s Col­lege, Lon­don, for six years, he moved in 1964 to the US as pro­fes­sor of fluid me­chan­ics in the divi­sion of en­gi­neer­ing and ap­plied sci­ence at the Cal­i­for­nia In­sti­tute of Tech­nol­ogy, bet­ter known as Cal­tech.

Pro­fes­sor Saffman made his name with his study on what oc­curs when a fluid of low vis­cos­ity, such as wa­ter, is in­jected into a fluid of higher vis­cos­ity, or stick­i­ness, such as glyc­er­ine. The be­hav­iour he ob­served and de­scribed be­came known as the Saff- man-Tay­lor in­sta­bil­ity, and is closely re­lated to many tech­no­log­i­cally im­por­tant pro­cesses, such as flow in a por­ous medium.

His re­search into the sub­ject was in­stru­men­tal in help­ing oil com­pa­nies to de­velop the best meth­ods of re­cov­er­ing trapped oil by in­ject­ing wa­ter or steam to force the oil to the sur­face.

He also made fun­da­men­tal con­tri­bu­tions to the un­der­stand­ing of vor­tic­ity, the way ships move through wa­ter and air­craft through air.

His metic­u­lous math­e­mat­i­cal anal­y­sis of tur­bu­lence in the wake of jet air­craft dur­ing take-off al­lowed him to cal­cu­late how long it takes for tur­bu­lence to dis­perse. This de­ter­mines when it is safe for an­other air­craft to fol­low.

Act­ing as con­sul­tant fol­low­ing sev­eral air­craft dis­as­ters, he helped ex­plain the con­di­tions that con­trib­uted to the ac­ci­dents. One of th­ese was the 1985 Dal­las air crash in­volv­ing a Delta Air Lines flight which tried to land in a thun­der­storm, killing 135 peo­ple.

In­ves­ti­ga­tion re­vealed that the weather had changed dras­ti­cally in the eight min­utes prior to the crash. Pro­fes­sor Saffman helped per­suade air-traf­fic con­trollers to al­low a min­i­mum pe­riod be­tween take-offs, to al­low tur­bu­lence to sub­side in the wake of pre­ced­ing air­craft.

Elected a fel­low of the Royal So­ci­ety in 1988, Pro­fes­sor Saffman was also a fel­low of the Amer­i­can Academy of Arts and Sciences and was awarded the Otto La­porte Award by the Amer­i­can Phys­i­cal So­ci­ety.

Au­thor of nu­mer­ous pa­pers in sci­en­tific jour­nals, he was co-au­thor of Vor­tex Dy­nam­ics (1992), analysing a field in which he be­came a prin­ci­pal con­trib­u­tor.

In 1995 he was named the Theodore von Kár­mán Pro­fes­sor of Ap­plied Math­e­mat­ics and Aero­nau­tics at Cal­tech.

He spent his re­tire­ment years from 2001 qui­etly with his fam­ily un­til his long fi­nal ill­ness. A gen­tle, soft-spo­ken man with a dry sense of hu­mour, he kept a low pro­file and re­fused to com­ment on what he did not un­der­stand.

He was a first-rate sci­en­tist and in­spir­ing teacher with the rare abil­ity to ex­plain com­pli­cated re­sults in a sim­ple way which al­ways reached the heart of the mat­ter.

Col­leagues at Cal­tech paid trib­ute to his gen­eros­ity as men­tor and friend to many, and praised his un­wa­ver­ing com­mit­ment to the high­est stan­dards of sci­en­tific ex­cel­lence and in­tegrity in ev­ery as­pect of his work.

He is sur­vived by his wife, Ruth; three chil­dren, Louise, Mark and Emma; and eight grand­chil­dren.

Pro­fes­sor Philip Saffman: ex­pert on ed­dies

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