swiss

Revision received August 7, 1999. Open for discussion till August 31, 2001.

JOURNAL OF HYDRAULIC RESEARCH, VOL. 39, 2001, NO. 1 3

(1)HM =gT

2uL,

Swiss contribution to water hammer theory

Contribution Suisse à la théorie du coup de bélier

WILLI H. HAGER, VAW, ETH-Zentrum, CH-8092 Zurich, Switzerland

KEY WORDS Fluid Transients, History, Hydraulics, Water Flow, Water Hammer.

ABSTRACTSwiss hydraulic engineers have significantly contributed to the understanding of water hammer, based partly on the advances of the Italians Ménabréaand Allievi. The contributions of Michaud, Strickler, Schnyder and Jaeger are particularly discussed in the light of modern developments, and biogra-phies on the latter two individuals are added. It is concluded that the phenomenon of water hammer has been developed within a short period, mainlydue to the mathematical methods furnished by mechanical engineers and the experience collected by civil engineers for the design and execution ofdams during the golden age of dam engineering.

RÉSUMÉLes ingénieurs hydrauliciens suisses ont contribués de façon significative à la compréhension du coup de bélier, en partie grâce aux développementsdes italiens Ménabréa et Allievi. Les contributions de Michaud, Strickler, Schnyder et Jaeger sont particulièrement traitées à la lumière desdéveloppements modernes, et les biographies des deux dernières personnes ci-dessus sont jointes. Il apparaît en conclusion que le phénomène du coupde bélier s’est précisé durant une très courte période, à cause surtout des méthodes mathématiques présentées par les ingénieurs mécaniciens et lesexpériences réunies par les ingénieurs civils pour la conception et la réalisation des barrages pendant l’âge d’or des constructions de barrages.

Introduction

Water hammer occurs due to hydraulic transients, i.e. any tempo-ral change of a basic parameter such as gate operation or variationof discharge due to pipe rupture. Water hammer has been studiedmainly from the middle of the 19th century and has come to stag-nation about 100 years later, until new interest was initiated withthe availability of computers. Water hammer involves unsteadypressurized fluid flow in an elastic pipe. Its features are describedin excellent textbooks, such as Wylie and Streeter (1967), Sharp(1981) and Chaudhry (1987).In the following, the Swiss contributions to water hammer under-standing are highlighted, with particular reference to the outstand-ing contributions of Schnyder (1904-1974) and Jaeger (1901-1989). Also, the significant contributions of the Lausannehydraulicians are accounted for.

Early contributions

Michaud (1848-1920) presented a paper (1878) to design air com-pressors. He observed that air pockets are not a direct cause forpipe damage, but that air can lead to water hammer when notproperly evacuated. Pipes must thus be filled carefully with water,and air pockets be removed from pipeline systems. By neglectingthe effects of fluid compressibility and elasticity of pipe walls,Michaud studied successively abrupt and partial closure configu-rations. Also, indications on air compressors and their optimumlocation were provided. By accounting for the effects of elasticityand compressibility the maximum pressure increase HM was de-termined as

where u=flow velocity before abrupt closure, L=length of pipefrom reservoir to orifice, g=gravitational acceleration andT=closure time. Michaud treated the water hammer process cor-rectly, in principle, although the wave features of unsteady pipeflow were overlooked (Vischer 1983). These were correctly mod-elled in 1902 by Lorenzo Allievi (1856-1941).While still at ETH as a PhD student, Albert Strickler (1887-1963)first reviewed the generalized approach of water hammer byAllievi, as published in 1913 (Strickler 1914a) and conductedexperiments on water hammer (Strickler 1914b). A steel pipe70m long was subjected to linear variation of the outflow section,and the results compared well with the predictions of Allievi. Theeffect of the so-called water hammer characteristic ρ=avo/(2gyo)was particularly mentioned, where a=propagation velocity,vo=pipe flow velocity and yo=static pressure head. The effects offriction and additional head losses were stated to be insignificantfor technical applications. Strickler was able to present a formula-tion for the extreme pressure head y’ as a function of onlyn=Lvo/(gyoτ) with τ=closure time. It is noteworthy that Strickler’sthesis had nothing to do with either water hammer nor his wellknown velocity formula for which he became famous.

Schnyder’s approach

Schnyder’s first paper (1929) is a mixture of theory and applica-tion, and is not simple to read. The graphical method for waterhammer in connection with pumps and valves, as designed by hisemployer Von Roll iron plant, was outlined, but the solution pro-cedure was not attractive enough for engineers. In Schnyder’s

4 JOURNAL OF HYDRAULIC RESEARCH, VOL. 39, 2001, NO. 1

(2)H – H1 = +g

a(C – C1)

(3)H – H2 = –g

a(C – C2)

(4)αi = rIII =1-III

1-II

1-I

-1III

-1II

-1I

ñññ

ñññ

++−+

,

(5)sIII = 1 – rIII .

(1932) key work the Schnyder-Bergeron method was outlined,using a generalized treatment of water hammer for arbitraryboundary conditions. The boundary conditions were graphicallydefined and the pressure and velocity distributions along the pipe-line determined. The method applies for both pipelines of con-stant and variable diameters.Based on the governing system of equations in a simple pipeline,the pressure heads H at locations x, x1, and x2, for times t, t1 andt2 may be written in the original notation as

The unknowns pressure head H and velocity C may thus be deter-mined, provided conditions at points 1 and 2 are known. Eqs.(2)and (3) are referred to as the conjugate conditions of state. Ifthese are known at two locations, the conditions at a third location3 may be determined. Refering to an (H,C) coordinate system,straight lines of slope +(a/g) and –(a/g) are drawn, respectively,and the point of intersection defines the solution. The two pointscan of course be located at the end of the pipeline, and the succes-sive development of velocity and pressure can be determined.Basic examples include the closure of a pipeline connected to areservoir, from steady to zero discharge by including friction,water hammer in a pipeline containing a surge tanke, and reso-nance effects on pipelines. The results of these computations areso nicely illustrated, and the method outlined so straightforward,that Schnyder’s paper was popular among hydraulic engineersthat were asked to compute unsteady pipe flows. Note that thecontributions of the Frenchmen Camichel, Eydoux and Garielfrom Toulouse university were cited, whereas Louis Bergeron(1876-1948) remained unmentioned at that time.The 1935 paper of Schnyder refered in particular to water ham-mer in pipe bifurcations added to surge tanks. His basic approachwas extended to this significant application. Bergeron was citedfor the first time, but Schnyder stated that Bergeron followed hisown approach to account for frictional effects. In the same year1935, Bergeron also published two papers, and cited Schnyder’sapproach in the latter paper. Whereas Bergeron refered mainly tothe analytical approach of Jaeger to be discussed below,Schnyder’s key reference was Allievi. It appears that the two re-searchers have had not too much sympathies for each other. Thegraphical method is actually referred to as the Schnyder-Bergeronmethod, a notation introduced by Jaeger.Obviously to attract Bergeron’s attention, Schnyder (1936a) pub-lished a paper in French, in the main engineering journal of West-ern Switzerland. He was able to demonstrate that Bergeron’s ap-proach neglects the effect of velocity head on water hammer. Animportant contribution to this problem was also presented by An-gus (1937), to which both Bergeron and Schnyder submitted dis-cussions, among others, and Jaeger introduced the notationMethod of Schnyder and Bergeron. In 1937 also, this notationwas used in the introduction to a paper on water hammer (Schlag

1937) by the leading French hydraulics journal Revue Généralede l’Hydraulique. Bergeron (1950) proposed the graphicalmethod for other physical phenomena, such as waves on electriclines or even lightnings. It is not clear whether Bergeron has evermet Schnyder, and both have stopped to work on water hammerafter the mid thirties. Schnyder turned more to hydraulic machin-ery associated with Von Roll, such as pressure reduction valves(Schnyder and Büttiker 1936), pumps (Schnyder 1937), and piperupture security (Schnyder 1939).Schnyder returned to fundamental research in 1943, and summa-rized the water hammer theory in a textbook style. One year later,Gaden and Schnyder (1944) were able to discuss various short-comings of the conventional approach by refering not only to thesmall, but also to the large amplitude assumption. The latter sim-plifies to the small amplitude theory whenever the ratio of pipe topropagation velocities is small. Schnyder (1944) also examinedthe relation between water hammer and gas dynamics. For smallrelative velocity, the equations are identical. Even for large veloc-ities of a continuous flow, equations can be expressed in a gener-alized form. However, for discontinuous flows, shocks form thatfollow the Hugoniot equations in gas dynamics.

Jaeger’s approach

Jaeger (1933a) submitted a thesis published as a book by the wellknown French printer Dunod. In a summary paper, Jaeger(1933b) outlined the findings of his thesis. A generalization ofAllievi’s approach seemed important for a pipeline system con-nected to a surge tank. Until then, substitute pipes were accountedfor, which can lead to serious errors. A large surge tank is an ex-cellent protection against pressure waves because all waves aretotally reflected, and the additional pressures in the pipeline arealways zero.Jaeger’s analysis involving a surge tank allows generalisation ofAllievi’s system of equations. At the bifurcation of three pipes I,II and III starting at the reservoir, the surge tank and the orifice,respectively, the positive wave Fi and the negative wave fi just atthe base of the surge tank are related to as fi=–αiFi with αi as re-flection parameter. With ρi as Allievi’s characteristic previouslyintroduced, Jaeger obtained for transmission ri and reflection si

coefficients, respectively

Allievi’s result for the single pipeline is simply αi=1. At one timestep, Jaeger’s analytical method involves a system of three equa-tions. Computations are described to be lengthy and errors havesignificant consequences to subsequent time steps. Compared tothe graphical method, this was a major disadvantage at Jaeger’stimes when all calculations were manually made. Jaeger con-cluded that water hammer and mass oscillations can add to eachother and result in larger pressure peaks, compared to a simple


(6)t

y

a

g

x

v2 ∂

∂=∂∂

,

(7)x

y

t

v

∂∂=

∂∂

g .

superposition of oscillations. The review of Jaeger’s thesis bySchnyder (1934) was excellent, and the two main Swiss research-ers on water hammer phenomena found a common basis of re-search. Collaboration between the two has not resulted, however,mainly because of too different professional backgrounds. Jaeger(1935a) stated that Schnyder introduced a method of computationfor pipes with a variable diameter. He speculated that Bergeronwas not aware of this generalisation but that Bergeron’s contribu-tion to the problem was mainly inclusion of head losses. Jaegeralso proposed that procedures for the prediction of water hammershould be presented in a generalized approach, including graphi-cal methods of Schnyder and Bergeron, and analytical methodsof Allievi and himself. He drew attention to the fact that the enve-lopes of all possible water hammer curves had not yet been deter-mined, although thousands of observations were available.An introduction of Jaeger’s analytical water hammer theory wasdevised in 1937, in the leading German journal Wasserkraft undWasserwirtschaft. It was stated that most engineers applied thegraphical method of Schnyder-Bergeron, although the analyticalmethod had advantages in defining the water hammer curves forcomplex pipelines. The governing equations for water hammer ina pipeline element based on the conservation equations for massand momentum are

The solution of this linear system of partial differential equationsis known since Riemann. The solutions depend exclusively on theinitial and boundary conditions. It can be demonstrated that func-tion F describes a wave travelling from the closure device to-wards the reservoir and the function f is the reflection wave. Atan arbitrary location x, the pressure head thus equals the sum ofstatic and dynamic pressure heads.Whereas the approach of Allievi refers to a pipeline of constantdiameter that is fed from a large reservoir, the general water ham-mer theory accounts for systems of pipes including also surgetanks. Jaeger presented his theory for both abrupt and continuousclosure and opening scenarios. The latter can be analyzed with asimpler approach because temporal variations are so small thatvarious terms remain constant. He then treated resonance of pipe-line systems due to rhythmic opening and closure processes.When looking at his analytical approach, most engineers werehappy to proceed with the graphical approach and the Schnyder-Bergeron method has been popular within the period until com-puters were available. From this time onwards, the analyticalmethod as introduced by Allievi and generalized by Jaeger tookover, until today. The first contribution to the theory of resonancein English was provided by Jaeger in 1939. By considering apipeline connected with a surge tank the minimum pressure at thegate is H=0, and the maximum pressure head is H=2ho, i.e. thedouble static pressure head. Jaeger extended his considerations tosystems of pipelines and verified his analytical results with

French observations.Jaeger’s textbook (1949) originated from his habilitation thesis in1944 and an almost complete draft was available in 1946. Whenpresenting it to Prof. Meyer-Peter, Director of Versuchsanstalt fürWasserbau at ETH, the latter realized its value and suggested tobe first author, a common European practise. Jaeger, however,disagreed and left the institute. He started working at RugbyU.K., for the English Electric Company, and finished his masterwork. The German version contains almost 500 pages, includingeach 170 pages on steady flows and unsteady flows, and another110 pages on groundwater flow and appendices mainly on experi-mental procedures. The unsteady flow chapter is subdivided al-most equally into surge tanks and water hammer. In the follow-ing, only the latter section is reviewed. After introducing the gov-erning equations of water hammer, and Allievi’s solution for thebasic pipe arrangement, the system reservoir-surge tank-penstockis considered. In addition, multiple pipeline systems are treated,and the effect of decreasing penstock diameter is discussed. Par-ticular reference is made to Henry Favre (1901-1966), a closefriend to Jaeger both during studying at ETH, and later at theVersuchsanstalt. During the years of Jaeger’s illness, collabora-tion was complicated, and when returning to Zurich in 1938,Favre became ETH professor in mechanics. Therefore, no com-mon paper of the two main Swiss theoretical hydraulicians isavailable. The next section of the book deals with resonance inpenstocks, and regulation of turbines. Only then, the method ofSchnyder-Bergeron is introduced and recommended as engineer-ing tool for practical applications. The basics of the method areoutlined for standard opening and closure scenarios. Then, theeffects of diameter reduction and friction are discussed. The waterhammer section is completed with a comparison between thecharacteristics of surge tank oscillations and water hammerwaves.

Further Swiss contributions

Jaeger’s contributions to water hammer are significant, particu-larly his analytical approach. He developed the Allievi approachand continued the (Swiss-French) hydraulics school of this re-search branch. After Daniel Gaden (1893-1966) had translatedAllievi’s general water hammer theory in 1921, a center for waterhammer established in the French part of Switzerland, obviouslyinfluenced by the Engineering School of Lausanne (today EPFL)and Charmilles and Vevey, furnishers for hydro machinery.Gaden, former director of Charmilles at Geneva and later profes-sor for hydraulic machinery at Ecole Polytechnique Universitairede Lausanne (EPUL), contributed largely to the regulation andstability of hydromachinery (Gaden 1945). He presented severalpapers together with Jules Calame (1891-1961), a consulting en-gineer of Geneva. The paper of Calame and Gaden (1935) wasquestioned by the young researcher Jaeger (1935b, 1936), mainlybecause of simplifications introduced into the computational pro-cedure. The present author is unaware of any personal contactsbetween Schnyder and Jaeger, although both were working lessthan 100 km apart, and both have significantly developed the wa-ter hammer theory. Biographies of both persons follow below.


References

Angus, R.W. (1937). Water hammer in pipes, including thosesupplied by centrifugal pumps: Graphical treatment. Proc. Me-chanical Engineers 136: 245-331.

Bergeron, L. (1950). Du coups de bélier en hydraulique aucoup de foudre en éléctricité (From water hammer in hydrau-lics to lightning in electricity). Dunod: Paris (in French).

Calame, J., Gaden, D. (1935). Influence des reflexionspartielles de l’onde aux changements de caracteristiques de laconduite et au point d’insertion d’une chambre d’equilibre (In-fluence of partial wave reflexions at changes of conduit charac-teristics and at the point of surge tank addition). Bulletin Tech-nique de la Suisse Romande 61(19): 217-220; 61(24): 277-282;62(5): 49-53 (in French).

Chaudhry, M.H. (1987). Applied hydraulic transients. VanNostrand Reinhold: New York.

Gaden, D. (1921). Théorie du coup de bélier (Theory of waterhammer). Dunod: Paris (in French).

Gaden, D., Schnyder, O. (1944). Coups de bélier de petites etgrandes amplitudes (Water hammer of small and large ampli-tudes). Bulletin Technique de la Suisse Romande 70(14): 173-182 (in French).

Gaden, D. (1945). Contribution à l’étude des regulateurs devitesse - Considérations sur le problème de la stabilité. LaConcorde: Lausanne (in French).

Jaeger, C. (1933a). Théorie générale du coup de bélier: Appli-cation au calcul des conduites à caractéristiques multiples etdes chambres d’équilibre (General theory of water hammer:Application of computation on pipelines with a multiple char-acteristic and on surge tanks). Dunod: Paris (in French).

Jaeger, C. (1933b). Théorie générale du coup de bélier (Generaltheory of water hammer). Le Génie Civil 103(26): 612-616 (inFrench).

Jaeger, C. (1935a). Über eine allgemeine graphischeBerechnungsmethode der Druckstösse in Rohrleitungen (On ageneral graphical method for water hammer in pipelines).Wasserkraft und Wasserwirtschaft 30(17): 202-203; 30(23):279-280 (in German).

Jaeger, C. (1935b). Les coups de bélier dans les conduites sim-ples et dans les conduites complexes (Water hammer in simpleand complex conduits). Bulletin Technique de la SuisseRomande 61(22): 255-256 (in French).

Jaeger, C. (1936). Quelques remarques en marge de la théoriedu coup de bélier. Réponse aux considerations sur le coup debélier, de MM. Calame et Gaden (Some remarks on the waterhammer theory. Answer to considerations of Calame andGaden). Bulletin Technique de la Suisse Romande 62(10): 113-118 (in French).

Jaeger, C. (1937). Die analytische Theorie des Druckstosses inDruckleitungen (Analytical theory of water hammer in pipes).Wasserkraft und Wasserwirtschaft 32(23): 269-276 (in Ger-man).

Jaeger, C. (1939). Theory of resonance in pressure conduits.Trans. ASME 61: 109-115.

Jaeger, C. (1949). Technische Hydraulik (Technical hydraulics).

Birkhäuser: Basle (in German).Michaud, J. (1878). Coup de bélier dans les conduites - Etude

des moyens employés pour en atténuer les effets (Water ham-mer in pipelines - Study of means to reduce the effects). Bulle-tin de la Société Vaudoise des Ingénieurs et des Architects4(3): 56-64; 4(4): 65-77 (in French).

Michaud, J. (1903). Intensité des coups de bélier dans lesconduites d’eau (Intensity of water hammer in water pipelines).Bulletin Technique de la Suisse Romande 29(3): 35-38; 29(4):49-51 (in French).

Schlag, A. (1937). Le coup de bélier dans une conduite àcaractéristique unique (The water hammer in a pipe withunique characteristic). Revue Universelle des Mines Series 813(10): 413-430 (in French).

Schnyder, O. (1929). Druckstösse in Pumpensteigleitungen(Water hammer in pumping pipelines). SchweizerischeBauzeitung 94(22): 271-273; 94(23): 283-286 (in German).

Schnyder, O. (1932). Über Druckstösse in Rohrleitungen (Onwater hammer in pipelines). Wasserkraft und Wasserwirtschaft27(5): 49-54; 27(6): 64-70; 27(8): 96 (in German).

Schnyder, O. (1934). Review of Théorie générale du coup debélier, by Charles Jaeger. Schweizerische Bauzeitung 104(5):54 (in German).

Schnyder, O. (1935). Über Druckstösse in verzweigtenLeitungen mit besonderer Berücksichtigung von Wasser-schlossanlagen (On water hammer in bifurcated pipelines withparticular consideration of surge tanks). Wasserkraft undWasserwirtschaft 30(12): 133-142; 30(14): 172 (in German).

Schnyder, O. (1936a). Considérations sur le coup de bélier(Considerations on water hammer). Bulletin Technique de laSuisse Romande 62(11): 121-123; 62(12): 133-137 (in French).

Schnyder, O. (1936b). Über Druckstösse in Rohrleitungen, diezur bleibenden Rohrverformung führen (On water hammer inconduits resulting in lasting pipe deformations). Wasserkraftund Wasserwirtschaft 31(4): 37-40 (in German).

Schnyder,O.,Büttiker,W. (1936).DruckreduzierventileundRegler für Wasserversorgungsanlagen (Pressure reductionvalves and regulators for drinking water supply). Bulletin derGas- und Wasserfachmänner 16(2): 35-41 (in German).

Schnyder, O. (1937). Comparisons between calculated and testresults on water hammer in pumping plants. Trans. ASME59(13): 695-700.

Schnyder, O. (1939). Rohrbruchsicherheitsanlagen (Pipe rup-ture safety installations). Wasserkraft und Wasserwirtschaft34(19/20): 230-238 (in German).

Schnyder, O. (1943). Druckstösse in Rohrleitungen (Waterhammer in conduits). Von Roll Mitteilung 2(3/4): 1-56 (in Ger-man).

Schnyder, O. (1944). Zur Theorie der Druckstösse bei grosserFliessgeschwindigkeit und die Zusammenhänge mit derGasdynamik (Theory of large velocity water hammer and rela-tions to gas dynamics). Wasserkraft und Wasserwirtschaft39(5/6): 131-134 (in German).

Sharp, B.B. (1981). Water hammer, problems and solutions.Arnold: London.

Strickler, A. (1914a). Theorie des Wasserstosses (Review of


Othmar Schnyder in 1935

Theory of water hammer). Schweizerische Bauzeitung 63(25):357 (in German).

Strickler, A. (1914b). Versuche über Druckschwankungen ineisernen Rohrleitungen (Experiments on pressure variations insteel pipes). Schweizerische Bauzeitung 64(7): 85-87; 64(10):123 (in German).

Vischer, D. (1983). Schweizer Pioniere der Hydraulik (Swisspioneers in hydraulics). Schweizer Ingenieur und Architekt101(48): 1129-1134 (in German).

Wylie, E.B., Streeter, V.L. (1967). Fluid transients.McGraw-Hill: New York.

Othmar Schnyder (1904-1974)

Born on 25th March 1904 at Kriens close to Lucerne, Switzer-land, Schnyder obtained the degree of mechanical engineer at theSwiss Federal Institute of Technology (ETH) in 1926. He submit-ted a PhD thesis on the static computation of regulation rings forturbines and pumps (1928) to obtain the degree of Doctor ofTechnical Sciences. In mid 1928, he started working with VonRoll iron works at Klus, close to Solothurn, Switzerland.The professional career of Schnyder is thus subdivided into twoparts: (1) His job as a design engineer for hydraulic machinerywith Von Roll and later in his own office, and (2) his hobby oreven his love: Water hammer. Schnyder’s (1930) typical contri-bution to his professional duties is characterized with a strongrelation to mechanical design of security elements. In 1936,Schnyder combined in a way his job and hobby for security in-stallations in hydraulic machinery. By this time, the Method of

Schnyder-Bergeron became a simple means for hydraulic engi-neers to tackle fluid transients in pipes. Schnyder, however,seems to have been aside from the rapid development, because ofhis physical distance to any university. By the end of the thirties,Daniel Gaden, a professor of hydraulic machinery of EPUL atLausanne (now EPFL) followed Schnyder’s outstanding work,and the two started collaboration, mainly during weekends.Schnyder, on the other hand, was firmely attached to Von Roll,and he was asked to develop hydraulic control elements for largepresses and oil pumps (Schnyder 1942, 1946). He was even al-lowed to develop a hydraulic lab in 1947 at Von Roll with instal-lations for both pressurized and free surface flows. However,Schnyder was pushed to consulting and management, which hedid not really like as a researcher. Frustrated by the job prospectat Von Roll, Schnyder decided to start his own company as a con-sultant in 1950, and in 1954 as the head of Hydro-Progress, anengineering office for developing hydraulic machinery.Othmar Schnyder was a quiet person, he loved to be with his fam-ily, and his daughter seemed to be his best friend. During week-ends, he often visited his chalet on lake of Lucerne, to be in na-ture and to elaborate new concepts for hydraulic machinery. Dur-ing the week, he visited his clients all over Switzerland, as also inGermany and Austria. In 1962, he started with Hydro-Progress atMalters close to Lucerne, sufficiently far away from Von Roll.There, he collaborated with his brother-in-law, who has been headof Hydro-Progress since 1974.Schnyder was a natural talent in technical terms. His practicalsense is demonstrated by the elegant development of his graphicalmethod for water hammer. He was an authority in technical mat-ters, and all his designs worked so nicely that clients hardly askedwhy. Schnyder was not a teacher: "Either you know how thisworks, or you will not learn it". He had always time for a newapproach, and many details were developed during nights orweekends. He was working to his last day, and visited his Hydro-Progress from his residence at Rüschlikon, close to Zurich. Aserious illness caused his death, but he was happy that the familydid well. Othmar Schnyder died on October 28, 1974 after a ful-filled live for progress in hydraulic machinery. He left his wifeAnna and a daughter.

References

Schnyder,O. (1930).AbsperrorganefürWasserkraftmaschinen(Arresting organs for hydraulic machinery). SchweizerischeTechnische Zeitschrift 27(10/11): 163-167 (in German).

Schnyder, O. (1936). Rohrbruchsicherungen (Safety elementsagainstpiperupture).SchweizerischeBauzeitung107(25):281-284 (in German).

Schnyder, O. (1942). Sind Flanschen hoch beansprucht? (Areflanges highly stressed?). Schweizerische Bauzeitung 119(25):298-299 (in German).

Schnyder, O. (1946). Various notes. Von Roll Mitteilung 5: 51-96; 5: 102-123 (in German).

Schnyder, O. (1947). Die hydraulische Forschungsanstalt (Thehydraulic laboratory). Von Roll Mitteilung 6: 102-119 (in Ger-man).


Charles Jaeger in 1936

Charles Jaeger (1901-1989)

Time at ETH

Charles Jaeger was born on March 26, 1901 in Zurich, Switzer-land, townsman of Auboranges in canton of Fribourg. He left theSwiss Federal Institute of Technology in 1924 as a civil engineerand started working with an engineering company in Geneva.However, he was suffering from tuberculose and had to be in iso-lation because of infection danger. He spent 1926 to 1928 at theInternational University Sanatory at Leysin. The first recoverycenter at approximately 1400m a.o.d. was opened in 1922 andcontained lecture rooms, libraries and study rooms. Jaeger couldthus penetrate into the technical literature. From 1929 to 1931 hewas the private assistant to Prof. Eugen Meyer-Peter (1883-1969),and presented a thesis on water hammer in 1932. His mothertongue was French, and he was fluent in German and Spanish. Hegot married in 1934, once his professional life was set. From1934 to 1938 he was a consultant at Villars sur Ollons, locatedEast of Montreux. There he was busy in writing state-of-the-artpapers on various subjects, such as descriptions of the recentlyopened Versuchsanstalt für Wasserbau (Jaeger 1930), newlyerrected power plants (Jaeger 1932a, 1936a, 1937b), on the fric-tion losses of tunnels, pipes and channels (Jaeger 1936b, c), onconstruction installations for dams (Jaeger 1936d) and even oneconomical problems of the thirties (Jaeger 1932b, 1937a). Hestarted also to act as a scientific reporter for journals such asWasserkraft and Wasserwirtschaft, the leading hydraulics journalin German language. From 1935 to 1938, all his papers and notes

were signed by C. J., Villars sur Ollon, where his wife worked asa dentist. He still had contacts to the Versuchsanstalt at Zurich,and it was normally him that summarized research results offriends, such as of Henri Favre (1901-1966) and Hans Albert Ein-stein (1904-1973), or the ASME water hammer committee, ofwhich he was associate member. He reported also on the activi-ties of ETH and Ecole Polytechnique de l’Université de Lausanne(EPUL) because of his interest in international activities, much incontrast to most of the other Swiss hydraulic engineers. The mainresearch topic until 1938, his return to ETH as a scientific collab-orator, remained of course water hammer, and he was able to gettwo papers accepted by the ASME Transactions on resonance ofpipe flow due to water hammer.His first topic after returning to the Versuchsanstalt was scour atplunge pools (Jaeger 1939, 1940). His proposal initiated the re-searches of Willi Eggenberger and Robert Müller on generalizedscour equations (Hager 1998). Further research topics of Jaegeruntil 1946 involved the generalized energy equation for free sur-face flows, stability analysis of surge tanks, groundwater flowand history of hydraulics. These shall not be reviewed here, how-ever. According to friends at ETH, Jaeger was a reticent personmainly writing reports, and not conducting lab works. He was byfar the most internationally known person of the institute, and thedirector Eugen Meyer-Peter had obviously some problems ofcompetition. The latter was a practitioner with excellent relationsto Swiss industries, but with a small international engagementuntil the end of the war. This tension grew into a conflict whenJaeger presented Meyer-Peter his book draft TechnischeHydraulik. Jaeger, since 1943 Privat-Dozent of ETH similar to asenior reader in the english university system, but without a lead-ing role at the Versuchsanstalt, decided to leave Switzerland.Jaeger and his young family left for a rather unsafe future both inprivate and professional terms.

From theory to applications

After fifteen years of academic research, Charles Jaeger wasthrown into the cold waters, as we say, with the English ElectricCompany at Rugby, close to London, U.K. He was suddenly inthe center of applications. England had just finished the war, andlots of activities started in power engineering. As a specialist inwater hammer and surge tanks analysis, Jaeger took actively partin the design of underground hydro-electric power stations. Healso gave advice for complex designs all over Europe as a con-sulting engineer. Jaeger developed into a specialist for pressuretunnels, and started working on rock mechanics, a science thathad not really developed yet. By the end of the fifties, so-calledpumped storage was developed, and Jaeger again was an impor-tant contributor to such designs. His activities are set down inmany contributions to English journals, such as in the Proc. of theInstitution of Civil Engineers, Water Power, the English ElectricJournal or the Engineering Journal.Jaeger was involved in various dam problems as an expert, suchas Malpasset (France in 1959), Vajont (Italy in 1963), Tarbela(Pakistan) and Kariba (Central Africa). His knowledge was pub-lished in books, starting from the classical textbook Technische


Hydraulik (1949) of which French and English translations werepublished in the mid fifties. Later, he contributed to Guthrie-Brown’s Hydro-Electric Engineering Practice (1970) and pub-lished the noteworthy Rock Mechanics and Engineering (1972).Jaeger summarized his immense knowledge on unsteady flows inFluid Transients (1977). All these books evolved from his activi-ties at Imperial College, where he served from 1946 to 1965 firstas a special lecturer, and then as a visiting professor (Jaeger1965). He stated that hydro-power engineering required widetechnical knowledge ranging from hydrology and fluid mechanicsto structures and architecture, a fact mainly responsible for thestudent’s interest in this branch of engineering, without fearingover-specialisation. After the war, a majority of students believedthat hydraulic engineering was the best introduction to a career incivil engineering. He then referred to the graduate course in engi-neering fluid mechanics and hydro-power structures that startedafter war at Imperial College, London. This initiative was takento fill in the gap for the future design of large hydro-power pro-jects, mainly in Scotland and in the Commonwealth. Thesecourses, which led to an engineering diploma, were an acceptedfeature of British universities.Jaeger offered rock mechanics as a particular course for graduatestudents at Imperial College. Such a course had become necessaryas a supplement to dam foundations, tunneling methods and de-sign of underground power stations. In his Preface to the rockmechanics book Jaeger (1979) stated that there is no bettermethod to deal with technical problems than the close analysis ofcase histories. Jaeger was known as an engineer and not only aspecialist, at least after his arrival at England. It is this outstand-ing quality that deserves particular attention in a time of over-specialisation.

Rehabilitation at ETH

In early 1980 Charles Jaeger came into contact with Prof. D.L.Vischer, former director of VAW, ETH Zurich. Jaeger submitteda curriculum vitae that served as the basis of a summary on Swisshydraulicians (Vischer 1983). Indeed, Jaeger returned from Eng-land in 1968, after having been visiting professor at ColoradoState University in 1966, and consultant for UNESCO in India,in 1967. His wife didn’t like the English weather, and the Jaegerswere happy at Pully, on Lake Geneva. Under the leadership ofProf. Vischer again, Jaeger was honored by a special issue of theSchweizerische Bauzeitung, with contributions of various friendsworldwide. In the introduction, Vischer refers to Jaeger as theknown unknown person, because Jaeger had great influence onSwiss hydraulics but was not known in public.Jaeger received various honors including the Gotthilf-Hagen-Medal for his services for water power development in 1965, buthis own country followed only in 1983, to honor him with theETH Honorary Degree of Doctor. The laudatio reads Honor forhis contributions to pipe and channel hydraulics and unsteadyprocesses in pipelines of power plants in particular (Vischer1989). Charles Jaeger was proud that ETH at last offered him thisspecial recognition. He died after a rich life for the engineeringprofession on December 5, 1989 at Pully.

Acknowledgements

The preparation of the biographies depended largely on the helpof Mrs. A. Schnyder, Rüschlikon, and Mrs. N. Hopkirk,Wallisellen, Charles Jaeger’s daughter. The author would like toacknowledge em.Prof. Dr. D.L. Vischer, ETH, and em.Prof. Dr.P. Novak, University of Newcastle, U.K., for reviewing themanuscript.

References

(1930) Die Versuchsanstalt für Wasserbau an der ETH in Zürich(The hydraulic lab at ETH Zurich). Schweiz. Baumeister-Zeitung 30(1): 4-6 (in German).

(1932a). Essai sur un modèle reduit de la galérie de fuite deWettingen (Model test on outlet tunnel of Wettingen powerplant). Bulletin Technique de la Suisse Romande 58: 289-291(in French).

(1932b). L’organisation du troc international au moyen dechambres de compensation d’industries (The organisation ofinternational barter by industrial compensation chambres).Goemaere: Bruxelles (in French).

(1936a) Die neueren französischen Wasserkraftwerke (Recenthydraulic power plants of France). Wasserkraft und Wasser-wirtschaft 31(13): 162-166; 31(14): 175-177 (in German).

(1936b). Italienische Messungen über Druckverluste inDruckrohren, Stollen und Kanälen (Italian observations onpressure losses in penstocks, tunnels and channels). Schweize-rische Bauzeitung 108(14): 150-151 (in German).

(1936c). Gleichförmige Strömung in grossen Rohrleitungen undKanälen (Uniform flow in large penstocks and channels).Wasserkraft und Wasserwirtschaft 31(21): 273-275 (in Ger-man).

(1936d). Baustelleninstallationen bei grossen Staumauern (Siteinstallations for large dams). Hoch- und Tiefbau 35(20): 168-171; 35(21): 175-179 (in German).

(1937a). Le problème de la prévision en économique rationelle(The problem of forecast for rational economics). ZeitschriftfürSchweizerischeStatistikundVolkswirtschaft73(2):279-286(in French).

(1937b). Die französischen Versuchsanstalten für Wasserbau(The French hydraulic laboratories). Wasserkraft und Wasser-wirtschaft 32(4): 44-46 (in German).

(1939). Über die Ähnlichkeit bei flussbaulichen Modellversuchen(On similarity of river engineering models). Wasserkraft undWasserwirtschaft 34(23/24): 269-270 (in German).

(1940). Sur les équations des cours d’eau à fond mobile (On theequations of flow in mobile bed channels). Comptes Rendus del’Académie des Sciences Paris 210(13): 472-474.

(1965) A college course in hydroelectric engineering. WaterPower 17(7): 267-272.

(1970). Governing of water turbines. Hydro-Electric engineeringpractise 2: 799-816. J. Guthrie Brown, ed. Blackie & Son:Glasgow.

(1972). Engineering and rock mechanics. Water Power 22(5/6):203-209; 22(7/8): 253-259.


(1977). Fluid transients. Blackie: Glasgow and London.(1979). Rock mechanics and engineering. 2nd ed. Cambridge

University Press: Cambridge.Hager, W.H. (1998). Plunge pool scour: Early history and

hydraulicians. Journal of Hydraulic Engineering 124(12):

1185-1187.Vischer, D. (1989). Zum Hinschied von Charles Jaeger (Obituary

for Charles Jaeger). Wasser, Energie, Luft 81(11/12): 361 (inGerman).

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