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Johann Nikuradse – Hydraulic experimenterWilli H. Hager a & Uno Liiv ba VAW , ETH-Zürich , CH-8092 , Zurich , Switzerland E-mail:b Corson Consulting , Akadeemia tee 21, 12618 , Tallinn, Estonia E-mail:Published online: 26 Apr 2010.

To cite this article: Willi H. Hager & Uno Liiv (2008) Johann Nikuradse – Hydraulic experimenter, Journal of HydraulicResearch, 46:4, 435-444, DOI: 10.1080/00221686.2008.9521880

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Journal of Hydraulic Research Vol. 46, No. 4 (2008), pp. 435–444

doi:10.3826/jhr.2008.3186

© 2008 International Association of Hydraulic Engineering and Research

Forum Paper

Johann Nikuradse – Hydraulic experimenter

Johann Nikuradse – Expérimentateur en hydrauliqueWILLI H. HAGER, (IAHR Member), VAW, ETH-Zürich, CH-8092 Zurich, Switzerland. E-mail: hager@vaw.baug.ethz.ch

UNO LIIV, (IAHR Member), Corson Consulting, Akadeemia tee 21, 12618 Tallinn, Estonia. E-mail: uno@corson.ee

ABSTRACTHydraulic engineers are familiar with the Nikuradse sand-roughened pipes, the “Nikuradse harp” describing the friction coefficient of pipe flow, andthe Nikuradse plots showing data points almost perfectly arranged along a curve. Who was Nikuradse, a collaborator of Ludwig Prandtl from GöttingenUniversity? How did Nikuradse work, and where did he finally move? This paper retraces the career and life of a person whose name is widely knownin hydraulic engineering, but whose person has been obscured by the complicated European history from 1900 to 1950. Recently located documentsshed additional light on the “Nikuradse case”.

RÉSUMÉLes ingénieurs hydrauliciens connaissent les conduites à rugosité sableuse de Nikuradse, ’la harpe de Nikuradse’ décrivant le coefficient de frot-tement de l’écoulement, et le tracé de Nikuradse montrant les points de mesures presque parfaitement disposés le long d’une courbe. Qui étaitNikuradse, un collaborateur de Ludwig Prandtl de l’université de Göttingen? Comment Nikuradse a-t-il travaillé, et où est-il allé finalement? Cetarticle retrace la carrière et la vie d’une personne dont le nom est largement connu en technologie hydraulique, mais dont la personne a été obscur-cie par l’histoire européenne compliquée de 1900 à 1950. Des documents récemment localisés ont permis de mieux faire la lumière sur le “casNikuradse”.

Keywords: Biography, experimentation, history, hydraulics, pipe flow

1 Introduction

Understanding pipe flow as a basic hydraulic issue is one of theoldest engineering problems. Until around 1800 little knowledgewas available, because water was mainly supplied by aqueducts.Then, metallic pipes at once allowed transporting water underpressure over larger distances. The Chezy formula devised by theFrenchmanAntoine de Chézy (1718–1798) was the first initiativeto relate the average flow velocity to the energy gradient times thesquare root of the hydraulic radius Rh, times the Chézy coefficientC incorporating the effect of boundary roughness.

Henry Darcy (1803–1858) and Julius Weisbach (1806–1871)developed the previous formulation around 1855 by stating thatthe energy slope SE is related to the average cross-sectionalvelocity V as

SE = f/(4Rh) · V 2/2g, (1)

with f as the friction coefficient and g as gravitational accelera-tion. The hydraulic radius Rh as the ratio between cross-sectionalarea and conduit perimeter is Rh = D/4 for pipe flow in circular

Revision received September 28, 2007/Open for discussion until February 28, 2009.

435

conduits of diameter D. The friction coefficient f is dimension-less, whereas the Chézy coefficient C involves dimensionallyboth length and time.

After Gotthilf Hagen (1797–1884) had realized in 1839 thata distinction must be made between the laminar and turbulentpipe flows; Darcy proposed a number of roughness coefficientsin terms of internal pipe roughness, from very rough to extremelysmooth, provided the flow is in the today’s turbulent regime. In1868, the Frenchman Philippe Gauckler (1826–1905) proposedfor the turbulent rough regime with k as still another roughnessparameter the power formula

V = k · S1/2E · R

2/3h . (2)

The Irish Robert Manning (1816–1897) and the Swiss AlbertStrickler (1887–1963) verified Eq. (2), such that it is currentlyreferred to as the Gauckler–Manning–Strickler GMS equation.

A great advance was made by the English Osborne Reynolds(1842–1912) in 1883, when realizing that pipe flow was governedby what we now designate the Reynolds number R = VD/ν,where ν is the kinematic viscosity. Flows with R < Rc, whereRc is the critical (subscript c) Reynolds number of the order

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436 W.H. Hager and U. Liiv Journal of Hydraulic Research Vol. 46, No. 4 (2008)

Figure 1 Johann Nikuradse around 1925 at KWI, Göttingen

of at least 2300 are in the laminar regime, whereas those withR ≥ Rc are turbulent. Pipe flow is therefore governed by boththe boundary roughness and the kinematic viscosity.

The German Heinrich Blasius (1883–1970), the first PhDstudent of Prandtl at the University of Göttingen, substan-tiated Reynolds’ proposal with the friction coefficient f =0.3164R−1/4 for turbulent smooth wall flow. Following Prandtl’sboundary layer theory, he used available data to present hisfamous yet today forgotten relation in 1912 (Hager, 2003a,b).Engineers were puzzled about his result as compared to the bythen accepted equations of the form (2). How come that one‘school’ presents a law in which the velocity depends essentiallyon pipe boundary roughness, whereas for other flows viscos-ity is essential? It was only realized somewhat later by Richardvon Mises (1883–1953), among many others, that practically allflows in hydraulics are essentially governed by both fluid viscos-ity and boundary roughness (von Mises, 1914). The two previousexpressions were recognized as particular cases of a more generalequation that had to be determined urgently. One of the outstand-ing contributions of Prandtl to the modern hydraulics was his pipeflow research during the 1920’s and 1930’s with his collaboratorNikuradse. The following account retraces the contributions ofmainly Nikuradse to pipe flow (Fig. 1).

2 Nikuradse’s research contributions

The first research of Nikuradse (1923) dealt with the velocityprofile of turbulent pipe flow. Based on the works of Blasius(1912) and Prandtl (1913) he measured velocity profiles withPitot tubes both in conduits and open channels of various shapes.Nikuradse (1926) verified Prandtl’s (1/7)-power law for circularpipes according to which the velocity increase with z1/7, where

z is the distance measured from the wall to the pipe axis. Forsmooth pipes, the “von Karman law of the wall” as proposed byTheodore von Karman (1882–1963) was also verified. Nikuradse(1929a) investigated turbulent flow in diverging and convergingchannels, a research topic that had been of considerable interestduring previous decades because of boundary layer separation.He noted that the velocity profile became fuller as the channelconvergence increased. Accelerating a flow thus makes veloc-ity profiles almost uniform, whereas deceleration up to somelimit renders them almost triangular in shape. If a certain limit offlow deceleration is attained, the flow separates from one or evenfrom both sides resulting in flow recirculation and poor flow sta-bility. This research was of far-reaching consequences for bothhydromechanics and aerodynamics.

Two other papers refer to pipe flows with extremely largeReynolds numbers of up to R = 900,000 (Nikuradse, 1929b,1930b). It was demonstrated that a universal velocity profileexists for distances x/D > 40 from the pipe entrance with x asthe streamwise coordinate. Deviations from the Blasius smoothpipe friction factor were noted for R > 300,000; furthermore,the velocity distribution close to the wall followed essentially apower law similar to Blasius, yet with an increasing exponent asthe Reynolds number increases. When plotting the dimensionlessvelocity profiles versus the relative radial coordinate, velocity dis-tributions become fuller for larger Reynolds numbers. Nikuradsealso determined the Prandtl “mixing length” and noted an effectof both the relative roughness and the Reynolds number. Prandtlappears to have been satisfied with these results since they werepresented in various international meetings (Prandtl, 1927, 1929).Nikuradse (1930a) took interest in the velocity and pressure dis-tributions of non-circular pipe flow. He substantiated that thepressure loss may be determined using Eq. (1) along with theconcept of the hydraulic radius. However, large deviations in thevelocity profiles from those of the circular pipe were detected.

Nikuradse’s most important research was published in 1932and in 1933. The first relates to turbulent flow in smooth circularpipes in which the Prandtl and the von Karman mixing lengththeories were verified (Nikuradse, 1932). The radial velocity u

as a function of the relative distance from the pipe center Z =(R − z)/r varied according to the velocity defect law (U − u)/v∗only with Z, where R is the pipe radius, r the radial coordinate,U the axial velocity, and v∗ the shear velocity. Expressions forboth the friction factor and the mixing length were also given.

Nikuradse (1933) extended the previous results to rough pipes,involving the Nikuradse sand-roughened pipes. An expressionfor the friction coefficient included both the relative boundaryroughness ks/D and the Reynolds number R to account for vis-cous effects. The sand roughness height ks was the first successfulattempt to measure boundary roughness indirectly with a uniformsand layer glued into a conduit surface. It is not clear whetherNikuradse or Prandtl have had the idea to measure a statisticalsurface pattern with an equivalent pre-determined surface rough-ness; the “Göttingen” concept was immediately accepted andwidely employed.

During his stay in Breslau (see below), Nikuradse publishedtwo reports involving the boundary layer of a plate for both

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laminar and turbulent flows (Nikuradse, 1942a, 1942b). Theseexperiments were conducted in 1933 in Göttingen and not pub-lished during almost a decade. A last paper of the Breslau erareviewed the lift theory of wings (Nikuradse and Mohr, 1943).This brief bibliography summarizes Nikuradse’s main scientificcontributions. For most of the larger reports, Nikuradse pre-pared summary papers in the German journals Zeitschrift VDIand ZAMM, next to congress contributions (Poggendorff, 1936).

3 Nikuradse’s “official” biography

According to present knowledge, Johann Nikuradze (the Germanspelling is Nikuradse, as adopted herein) was born on Novem-ber 20, 1894 in Samtredi, Georgia, and passed away on July 18,1979 in Göttingen (Poggendorff, 1936; KDK, 1966). He grad-uated from the Universities of Dorpat, today’s Tartu in Estonia(Kleinschroth, 1994), and Göttingen in natural sciences and sub-mitted his PhD thesis to the University of Göttingen in 1923(Nikuradse, 1923; 1926). He was a collaborator to Prandtl from1923 to 1934, staying at the Institute of Applied Mechanics until1925, and then at the newly founded Kaiser-Wilhelm InstitutKWI (Fig. 2). In 1934, Nikuradse was appointed Lecturer ofFluid Mechanics at the Technical University of Breslau, today’sWrocław in Poland, and promoted to professor of fluid mechanicsin 1940. He there published his first volume on the Mechanicsof ideal fluids (Nikuradse, 1942c); the manuscript of the sec-ond volume was lost during World War II (Kleinschroth, 1994).Nikuradse left Breslau in 1945 and moved to the Rheinländisch-Westfälische Technical University RWTH inAachen as Emeritus,where he collaborated with his brother Alexander, a profes-sor of electronics at the Munich Technical University, and with

Figure 2 Prandtl with assistants in 1927, from left, seated: Tietjens, Ackeret, Betz, Wieselsberger, Prandtl, Tollmien, Langer; standing: Flachsbart,Buehl, Nikuradse, Busemann, Seiferth, Muttray, Peters, Schrenk (Kraemer, 1975)

whom he published on flows in rarefied gas. In 1960 Nikuradsewas appointed professor of fluid mechanics at RWTH Aachen(Anonymous, 1960). In parallel, he collaborated with the US avi-ation industries and investigated coating procedures of airplanebodies. He was a founder of Collegium Magistrorum in Munich,whose purpose was to improve the mathematics education forhigh school students (Kleinschroth, 1994).

The American Rouse (1991) presented additions to the storyof Nikuradse: According to Rouse, Nikuradse was born onNovember 20, 1896, instead of 1894, almost certainly a printingerror. With reference to the presentation of experimental data,Rouse noted that “Nikuradse’s experimental points were surpris-ingly free from scatter.” Nikuradse had a practice in which hedetermined the rough path of a curve with preliminary obser-vations and then discarded final measurements that fell too farafield’. According to Rouse, “This practice would be suspiciousif the results later proved misleading; however, except for thecase to be discussed, Nikuradse’s pipe data continued to proveuseful in various unexpected ways as time passed.” Zagarolaand Smits (1998), for example, re-evaluated the laws of turbu-lent flow and put Nikuradse’s contribution in context with laterobservations.

Rouse continues: “In 1946, I contacted Prandtl for the discrep-ancy between Nikuradse’s raw and calculated data for smoothpipes. Eventually, Prandtl replied that Nikuradse had indeedadded a constant factor to all his velocity distribution measure-ments, because otherwise his data would not have been in accordwith the laminar limit which they had to approach. Prandtl heldthat Nikuradse was theoretically justified in making the correc-tion, but wrong in not mentioning it in the paper ….” Figure 3shows typical plots of Nikuradse including the “Nikuradse harp,”

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438 W.H. Hager and U. Liiv Journal of Hydraulic Research Vol. 46, No. 4 (2008)

Figure 3 Typical plots of Nikuradse for the friction factor in (a) smooth pipe flow (Nikuradse, 1929b) and (b) rough pipe flow showing the so-called“Nikuradse harp” (Nikuradse, 1933)

with the data extremely close to the trend line, for which onecould also refer to as the “Nikuradse technique.” Rouse furtherstates that “According to KarlWieghardt (1913–1996), Nikuradsewould plot his data as soon as each measurement was completed.If a point fell too far from the expected curve, Nikuradse wouldsay ‘Das passt sich nicht!’ (That doesn’t fit), and would repeatthe measurements, until he obtained practically no scatter amonghis plotted results…”

Rouse further states: “After the war [WW II], astonishingly,Nikuradse brought suit against the government for havingdeprived him of his dozentship [in Breslau]. Even more aston-ishingly, he won the case and his academic rank was restored,but no university would have him. He was back in Göttingenliving with his wife when I [Rouse] was there in 1958. His wifewas at the time of their marriage a draftsman and data-reducer ofPrandtl’s staff. Out of curiosity, I spent an hour in their home, dis-cussing purely irrelevant topics. Naturally, Prandtl and Nikuradsewere not speaking with each other when my letter had arrived.As Tollmien once said to me, ‘Nikuradse ended up with a finesalary and no duties, and all I have is debts’.” Walter Tollmien

(1900–1968) had taken over as Director of KWI from Prandtl in1947.

Another story between Prandtl and Nikuradse is presented byOswatitsch and Wieghardt (1987): “Nikuradse published histest results on turbulent flow through smooth and rough pipes in1932 and 1933…. Unfortunately, this increased his self-esteemto such a height that he tried to replace Prandtl as director afterHitler had come to power. It was, indeed, a dangerous attack,for Nikuradse knew at least one man high up in the Nazi regime,whereas neither Prandtl nor Betz ever became party members inspite of their important positions. Luckily, Prandtl was victorious.Nikuradse had to leave KWI and — without Prandtl’s guidance— he never again wrote a paper worth mentioning.”

This story was also given by von Karman (1967): “Prandtl’sartlessness was even more pronounced in his relationship withthe Nazis in the 1930’s. There is a story told by my friend Pro-fessor Richard Courant, the well-known New York Universitymathematician, who was one of the first Jewish professors tobe ousted from Göttingen when the Nazis came into power. Onthe occasion of Hitler’s takeover, Prandtl was in his office when

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there was a knock on the door. He admitted a laboratory assistant,who for years had been doing relatively minor experimental workaround the laboratory. Nobody had ever paid much attention tohim. This assistant announced that all during those years he hadbeen a Nazi Party member and now he was taking charge of thelaboratory. Prandtl stared at him in disgust, and told him to getout. Suddenly losing courage the assistant obeyed, but Prandtlwasn’t prepared for what happened next. A few days later, theNazi Gauleiter of Göttingen warned Prandtl not to mistreat aloyal Nazi Party member again. Prandtl was shocked. He finallywas compelled to reinstate his assistant into a higher position inthe laboratory.” This may have been the promotion of Nikuradseto Lecturer at Göttingen University, as previously mentioned.

The Nikuradse 1934 case at KWI was also reported by Vogel-Prandtl (1993), one of Prandtl’s daughters, and by CordulaTollmien (1987), a family member of Walter Tollmien. Accordingto the latter, Nikuradse was accused of espionage and of theft ofbooks from KWI; it is also stated that Nikuradse was not partic-ularly popular with his colleagues mainly because they thoughtthat he was looking for preferential treatment from Prandtl. Fur-ther, Nikuradse appears to have been a Nazi member from 1923,just after having arrived in Germany and shortly after the partyhad been founded (which is wrong because he had no Germancitizenship until 1933). Nikuradse seems to have prepared alist with names of Jewish collaborators at Göttingen University.Prandtl, who initially misjudged the real situation and protectedNikuradse against his colleagues, changed his attitude becausethe “Nikuradse case” prevented an orderly management of theInstitute. In 1934, Prandtl therefore decided to dismiss Niku-radse for “imperative official reasons.” Prandtl’s position was,therefore, sufficiently strong in Nazi Germany that his decisionwas accepted, resulting in the move of Nikuradse to Breslau.

4 New findings on the biography of Nikuradse

In 2003, the first author was contacted by the second for the exactdate of birth of Johann Nikuradse. Liiv had located a set of docu-ments in the Estonian Historical Archives relating to Nikuradse’sstay in Tartu. It was realized only later that Johann’s brotherSilovan Nikuradse had been a student in Estonia, and that therewere no documents relating to Johann. Tsarist Russia allowedhigher education for students from Georgia in Estonia and theTartu University offered more academic freedom as compared toother Russian institutions. Tartu is the Estonian name of Dorpat,whereas the city was called Jurjev in Russian, as stated in thedocuments. Liiv was puzzled about the date of birth, officially1894, because Nikuradse would have started at Tartu Universityat the age of only 14 years. Liiv found a birth certificate of aSilovan Iviljanovts Nikuradse stating September 14, 1889 as thebirthday (Appendix A). According to this certificate his father’sfirst name was Iviljanovts and his parents were farmers. Basedon a contact with Roman Shaquarishvili who lives in New Yorkand is the great grandson of Silovan Nikuradse (1889–1965),Silovan indeed studied medicine in Tartu (Appendix B) and wasthe elder brother of Johann. The second author further found that

Figure 4 Johann’s brother Silovan Iveljanovitš Nikuradse in 1908 whenstarting studies in Tartu

Johann has probably stayed with his elder brother Silovan in Tartualthough he was officially not registered as a student (Fig. 4).

The date of birth stated in the PhD thesis of Johann Nikuradse’sCV is therefore almost certainly wrong (Appendix C). Accordingto the second author, the Estonian Archives have no documentsrelating to Johann. If he would have been in Tartu with Silo-van, Johann would have been too young to have studied there. Itappears therefore, that Johann Nikuradse falsely claimed to havestudied in Tartu, when applying for his student status at the Uni-versity of Göttingen. The birth year 1892 stated in Appendix C is2 years earlier than in the official documents (Poggendorff, 1936).

One reason for Johann Nikuradse to appear young was hisanxiety to be conscripted into the Russian Army. In Russia andin the Soviet Union later, there was a system that guaranteeduniversity students would only be conscripted during emergencysituations. Between 1915 and 1917 when the situation for Russiabecame critical, Johann Nikuradse was mobilized. He finallygraduated as an engineer from the Tbilisi (Tiflis) PolytechnicalInstitute in 1919 and then went to Germany, where he startedworking with Prandtl in 1923 (Appendix C).

5 Nikuradse and Prandtl

The first document of Prandtl reproduced in Appendix D origi-nates obviously from the dismissal of 9 colleagues of Nikuradse,as described by Tollmien (1987). Prandtl explains that he found anassistant position for Nikuradse after having completed his PhDthesis. Nikuradse had some talents in administration such that hewas the later grounds manager and head of the institute workshop.Apparently he performed these duties to the satisfaction of KWI.Regarding his scientific works, Prandtl stated that Nikuradsewas unsuited for all theoretical investigations, whereas he wasa skilled, conscientious and hardworking experimenter who hadproduced a number of important results. When writing his reports,

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he was dependent on the help of colleagues who improved hisGerman and scientific derivations. Prandtl continues that if hehad to grade the effect of a collaborator, then Nikuradse wouldreceive a good mark, because his results were important for theInstitute; how these works evolve was considered less impor-tant. As far as the personal merits of Nikuradse are concerned,he pretends to be a more independent scientist as he actually is.However, Prandtl continues and states that there is always a con-siderable portion of his (Prandtl’s) own thoughts and ideas in allstudies produced at KWI, something he finds to be not unusual.

Concerning the relation of Nikuradse toward his collaborators,one may state that his subordinates stand up for him in a sym-pathetic manner, but that those at the same professional level aremostly opposed to him. This may result to a certain degree fromNikuradse’s foreign descent, but also because of his attempt inleadership to cover his inferiority in theoretical matters. Towardme (Prandtl), Nikuradse is of great loyalty and following; he hascontributed to the matters of the institute with great energy. Inturn I have the feeling that I am in his debt.

In a letter of the Trustee of Göttingen University to the DirectorGeneral of KWI in Berlin, dated August 16, 1933, the reasonfor the accusation against Nikuradse is well-founded: He wassuspected of book theft and of espionage for France and Russia.The latter cause was considered ridiculous because Nikuradse hadlived for 10 years in Germany and acquired German citizenship.Later, in a letter dated December 21, 1933 from Prandtl to thePresident of KWI, it is stated that Nikuradse is a follower ofthe Nazi party, yet he was not a member until June 1933 (whenbecoming the German citizenship) because of his nationality.

Nikuradse wrote a letter to the district court of Göttingen onFebruary 27, 1934, in which he made a complaint against theAerodynamische Versuchsanstalt AVA, which was represented byLudwig Prandtl and Albert Betz (Fig. 5). Nikuradse states thathe began work at AVA on March 1, 1925 as a scientific collab-orator until February 15, 1934, when he received his dismissalwith effect as of March 31, 1934. Nikuradse writes that thereis no reason for a dismissal; furthermore, his dismissal wouldbe unfair, since a number of his colleagues were not marriedand entered AVA later than he did (typically a valid argument in

Figure 5 Johann Nikuradse (a) from a photo attached to a letter ofPrandtl in 1934, (b) around 1975 (Kleinschroth, 1994).

German labour courts). However, Prandtl and Betz maintainedtheir position and Nikuradse was only left with the option tosubmit his case to the labor court.

Appendix E contains excerpts of a rather lengthy documentwritten in Spring of 1934, at which time Prandtl was in the processof dismissing Nikuradse. Prandtl had originally overestimatedNikuradse’s scientific capacities, since he had often employed thehelp of colleagues in the laboratory without necessarily givingthem full credit or authorship on reports. Just how incapableNikuradse was, was in fact masked by his deficiencies in theGerman language, something that was very apparent at seminardiscussions. Having realized his error, Prandtl concluded thatNikuradse was only suitable for menial jobs in the laboratory,but faced the dilemma that he could no longer be demoted toa technician, since he also did have any training in the trades.A dismissal was the only option left.

A number of details and quarrels are described in Sec-tions 2–7 of the document, all pointing to a weak character ofNikuradse: petty arguments about misplaced documents, falseaccusations about the behavior of colleagues, outright lies con-cerning his involvement in drawing up a list of Jewish professorsin Göttingen, misuse of word of honor and lie, and general dis-turbance of the working atmosphere at the Institute. Prandtl musthave spent weeks with the Nikuradse case, until he finally cameto the conclusion that his institute could only be calmed afterNikuradse left. This was initially sought by a dismissal, whichwas successfully countered by Nikuradse. It appears that Niku-radse did have contacts to the Nazi party, at least he boastedabout them among colleagues, and these may have some impacton the final solution. Appendix E also states that (1) Prof. Prandtldismissed Nikuradse originally for political reasons; (2) Niku-radse states that he withdraws with regret his comment madeon June 20 (1934) according to which Prandtl had tried to usewitnesses against him; and (3) Prandtl withdrew the dismissalwithout notice made on June 30. In common agreement, theofficial employment of Nikuradse came to an end on July 31,1934. As previously described, Nikuradse moved, perhaps withthe assistance of Prandtl, to the University of Breslau.

6 Conclusions

Johann Nikuradse contributed to the reputation of Ludwig Prandtlin hydrodynamics at Göttingen University by original data thatsupported various additions to the boundary-layer theory and toclarify the influence of both fluid viscosity and relative roughnessin pipe flow. The way in which Nikuradse prepared his well-known curves is certainly uncommon, although his results havebeen and still are used in hydraulics. Discrepancies in his offi-cial biography were detected relating particularly to the officialyear of birth, which Nikuradse appears to have placed after theeffective date to circumvent participation in World War I. Par-ticular attention was paid to the relation between Nikuradse andPrandtl, and Nikuradse and his colleagues at KWI, based on doc-uments that were recently found at the Historical Archives ofthe Max–Planck-Association. Nikuradse’s move from Göttingen

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to Breslau University was not planned, and some uncertaintiesremain in how he fell out of the favor with Prandtl and underwhat circumstances he obtained his position at Breslau Univer-sity in 1934. In any case, Nikuradse’s contribution to hydraulicengineering will survive.

Acknowledgements

The authors acknowledge the assistance of Archiv zur Geschichteder Max-Planck-Gesellschaft in Berlin-Dahlem and the EstonianHistorical Archives in Tartu. They also would like to thank JensUnger for help in the preparation of this manuscript. The improve-ment of the manuscript by Prof. Dr. C. Tropea, University ofDarmstadt, is gratefully acknowledged.

Appendix A: Translation of birth certificate (ESHA, 2003a)

Under of the order of the Imperial Highness of the Rus-sian Autocracy given thus to the Georgian-Impretian ClericalDominated Notarial Office to resident-peasant Iveljan PavlovitšNikuradze from the Kutaisi County village Kulaši by his petitionto issue him the Certificate on the base of the 1st part MetricanBook point 30 of the Kulaši Crucification Church about the birthand christening of his son Silovan, who was born on the sixthand christened on the fourteenth of September of the year onethousand eight hundred eighty nine. His parents are the residentsof the village Kulaši, peasant Iveljan Pavlovitš Nikuradze and hiswife Elizaveta Georgievna both trusting Orthodoxy, witness wasresident of the Kutaisi County village Kavakude peasant DavitAleksiev Loria, the christening ceremory was held by the blessedchurchman Ermolai Kandelaki together with the sexton NestorKandelaki.

The Georgian-Impretian Clerical Dominated Notarial Officeclarifies the above citation with signatures and the heraldic stamp.For that document the corresponding heraldic payment has beenmade. Town of Tiflis, 27th of May 1909.

Signatures

Member of the Notarial Office, Secretary, Tablechief

Appendix B: Translation of university course certificate(ESHA, 2003b)

Private Medical University Courses, Jurjev, September 24th,1915, No 9285

EXERCISE CERTIFICATE

The bearer of the current Certificate Silovan IljanovitšNIKURADZE born in Kutaisi County on September Sixth 1889,Crucification Church faith, son of the peasant Iveljan PavlovitšNikuradze, was accepted as a student of the Medical Faculty ofthe Private Medical University Courses from September 1908.The present CERTIFICATE is issued after satisfactory ending

of the full course of medical sciences, acknowledging the truthof it with the consensus of the corresponding teachers, the pre-liminary examinations during ten semesters, allowing for finalexamination to become the degree of medical doctor under theinjunction number 5244 of the Ministry of the Public Educationfrom February 6th, 1915. [A number of marks for the variousbranches is then given.]

In addition he fulfilled with satisfaction preliminary exam-inations, participated in practical exercises, followed closelythe trends of different clinical diseases under the courses of thesecond part.

Assuring above mentioned, the Certificate was issued andsupplied with signatures and seal.

Director of the Courses, Prof. KurnizkiDean of the Medical Faculty, Kesler

Appendix C

Nikuradse’s CV, From the University Archives, Göttingen,Germany (Added to his PhD thesis in 1923)

I, Johann Nikuradse, son of the railways director Ilia Nikuradse,was born on November 20th, 1892 in Samtredi, Georgia. I am acitizen of Georgia. I received my school education from the Com-merz Gymnasium in Tiflis. From 1914 to 1917 I made studies atthe Dorpat University and continued from 1917 to 1919 at theTrans-Caucasian University in Tiflis. Induced by the GeorgianGovernment by the end of 1919 I moved to the University ofGöttingen to get acquainted with the German culture and sci-ence. In Göttingen, I followed the lectures of the professors Born,Gudden, Courant, Hertz, Hilbert, Franck, Prandtl, Pohl, Reich,Runge and Schmeidler. To all the teachers I express my thanks.

In particular, I would like to thank Prof. Reich and Prof. Pohlfor their help during my studies, as also to Prof. Prandtl for his richsuggestions and his steady help, which I received permanentlyand in particular during the writing of this work.

(Signed J. Nikuradse)

Appendix D: Investigation against Dr. J. Nikuradse(undated, probably in 1933)

Prof. Dr. L. Prandtl, GöttingenBetr.: Untersuchung gegen Dr. J. Nikuradse

Auf Wunsch von Herrn Universitätsrat Wolff gebe ich hieruntereine Darlegung meiner Eindrücke über Herrn Dr. Nikuradse.

Nikuradse war zuerst mein Doktorand und hat später alsVolontär seine Forschungen fortgesetzt. Als er in Not geraten war,habe ich mich einverstanden erklärt, ihm von Seiten des InstitutsBeihilfen zu geben. Da seine Leistungen für das Institut immerwertvoller wurden, entschloss ich mich, ihm bei einer eintre-tenden Veränderung im Institut eine Assistentenstelle zu geben.Da er offensichtliches Talent für Verwaltungsangelegenheitenhat, habe ich ihn dann später zum Betriebsleiter der Abteilunggemacht und ihm die Leitung der Werkstätte und auch die wis-senschaftliche Verwaltung übertragen. Über die Art, wie er diese

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Verwaltung geführt hat, herrscht nach allem, was ich höre, auchseitens der Kaiser-Wilhelm-Gesellschaft uneingeschränktes Lob.

Was eine wissenschaftliche Tätigkeit betrifft, so muss gesagtwerden, dass ihm alles Theoretische nicht liegt, dagegen ist er einsehr geschickter, gewissenhafter und fleissiger Experimentatorund hat für das Institut schon eine ganze Anzahl recht wichtigerBeobachtungsreihen gemacht und veröffentlicht. Bei der Her-stellung der zugehörigen Forschungsberichte musste er sowohlbezüglich des deutschen Stils wie auch der textlichen Abfas-sung von etwa vorkommenden theoretischen Erörterungen wegendie Hilfe von anderen Mitarbeitern des Instituts in Anspruchnehmen. Die Aussagen von Dr. [Hermann] Schlichting, dieoffenbar angezweifelt worden sind, entsprechen, soviel ich sehe,durchaus den Tatsachen. Wenn man die Wirksamkeit der einzel-nen Mitarbeiter des Instituts danach beurteilt, was auf Grundihrer Arbeiten herausgekommen ist, so muss Herr Nikuradse hierdurchaus eine gute Note erteilt werden. Für den Endeffekt ist esvor allem wichtig, dass gute Arbeiten zustande kommen, wiees hier tatsächlich der Fall ist; wie sie im einzelnen zustandekommen, ist weniger wichtig. Soweit es sich allerdings darumhandelt, aus den gedruckten Arbeiten ein Urteil über die per-sönliche Leistung des Verfassers zu bekommen, so gebe ich zu,dass die Nikuradse’schen Arbeiten in gewisser Hinsicht einenselbständigeren Forscher vortäuschen als er es wirklich ist. Imübrigen steckt in seinen Arbeiten, wie auch in vielen Arbeitender anderen Mitarbeiter, eine erhebliche Portion meines persön-lichen Gedankenguts, aber ich halte auch dies als durchaus inder Ordnung. Ich finde, dass man in den Kreisen der BeurteilerDerartiges auch schon in Rechnung zieht und habe selbst schonerlebt, dass Gedanken meiner Mitarbeiter, die ganz ihr eigenesgeistiges Eigentum waren, hinterher von Aussenstehenden mirzugeschrieben wurden.

Was das Verhältnis von Dr. Nikuradse zu seinen Mitarbeit-ern betrifft, so ist durchweg festzustellen, dass die, welche unterihm arbeiten, sich in höchst sympathischer Weise für ihn einset-zen, dass aber diejenigen, die ihm gleichgestellt sind, zu einemerheblichen Prozentsatz gegen ihn stehen. Bis zu einem gewis-sen Grade mag das durch seine fremdländische Abstammungkommen, wohl aber auch dadurch, dass er einerseits danachstrebt, selbst eine führende Rolle zu spielen und andererseitsim Bewusstsein seiner Unterlegenheit in theoretischen Dingengegen die Kollegen misstrauisch ist.

Mir gegenüber ist er von einer sehr grossen Treue undAnhänglichkeit und hat, wie es aus den Protokollen mehrfach her-vorgeht, sich auch für die grossen Belange des Instituts mehrfachmit grosser Energie eingesetzt. Jedenfalls habe ich das Gefühl,dass ich ihm auch wieder Treue schuldig bin.

Gez. Ludwig Prandtl

Appendix E (Abt. I Rep. 44, Nr. 159; undated, mostprobably in spring 1934)

1. Prof. P.[randtl] hat N.[ikuradse] während seines Studi-ums als wissenschaftlich wenig qualifiziert kennen ge-lernt. Da N. nach Abschluss seiner Studien durchaus bei

Prof. P. arbeiten wollte, wurde er von diesem mit ein-facheren Messarbeiten beschäftigt. N. hat dann jahrelang mitemsigem Fleiss für wenig Entgelt gearbeitet und so erhielt erschliesslich eine Anstellung im KWI. N. verstand es, für diewissenschaftliche und konstruktive Leitung seiner Versuchesowie für die wissenschaftliche Auswertung seiner Messun-gen andere Mitarbeiter heranzuziehen. Es sind daher eineReihe guter Forschungsarbeiten entstanden und unter demNamen N. veröffentlicht worden. Durch diese Arbeiten hatteder Chef den Eindruck gewonnen N. habe sich inzwischenwissenschaftlich herausgemacht. Der Tiefstand der Kennt-nisse N.s blieb dem Chef durch N.s mangelhafte Beherrschungder deutschen Sprache verborgen, die in Vorträgen undBesprechungen stets offenbar wurde. Im Laufe des letztenJahres hat Prof. P. aber erkannt, dass er sich bezüglich N.sLeistungen geirrt hat, dass N. vollkommen auf die Hilfeanderer angewiesen ist und dass N. noch genau wie vor 10Jahren nur für einfachste Arbeiten zu gebrauchen ist. Prof.P. bedauert sehr, dass N. schon so lange eine Scheinexistenzführen konnte. Da sich N. schwerlich zu einem Hilfsarbeiterdegradieren lassen würde—als Techniker käme N. nicht inFrage, da er weder handwerkliche noch konstruktive Fer-tigkeiten besitzt - kann Prof. P. dem unhaltbaren Zustand nurdurch Kündigung ein Ende bereiten.

2. Ein besonders krasser Fall wissenschaftlicher Unehrlichkeithat sich noch in jüngster Zeit ereignet: N. versuchte, unterseinem alleinigen Namen eine Arbeit zur Veröffentlichunganzumelden, die ein Ingenieur des Institutes unter Anleitungvon Prof. P. ohne jegliche Mitarbeit N.s ausgeführt hat.

3. Im Sommer [19]32 verbreitete N. die Behauptung, der dama-lige Abteilungsleiter Flachsbart (jetzt Professor in Hannover)intrigiere gegen den Chef und erstrebe einen Direktionspostenim Institut. Durch die Verbreitung dieses Gerüchtes wurdeder Arbeitsfrieden beträchtlich gestört. Prof. P. konnte aberfeststellen, dass sich Flachsbart jederzeit korrekt verhaltenhat und die umfangreichen Anklagen N.s brachen im Nichtszusammen. Daraufhin hat sich Prof. P. sehr überlegt, ob erN. behalten könne [Anmerkung mit Bleistift: Eine Kündi-gung habe ich damals nicht in Betracht gezogen]. Da Prof. P.glaubte, N.s Verhalten sei durch seine psychopathische Veran-lagung, die Eigentümlichkeit seiner undeutschen Rasse sowieseine mangelhafte Beherrschung der deutschen Sprache zuerklären, und da auch Flachsbart N. entschuldigte und aufeine Genugtuung verzichtete, hat Prof. P. von einer Kündigungabgesehen.

4. ….5. Im Frühsommer [19]33 gab N. gelegentlich einer Unter-

haltung mit Schröter und W.[alchner] zweimal das Ehren-wort, sich politisch nie betätigt zu haben und auch eineJudenliste Göttinger Professoren nicht aufgestellt zu haben,obwohl bereits das Gegenteil erwiesen war (Zeuge: Hansen,Helmbold). Durch diese Vergeudung des Ehrenwortes warseitdem ein Vertrauensverhältnis zwischen den beiden imgleichen Zimmer arbeitenden Assistenten W. und Schröternicht mehr möglich. Geheimrat Wolff sagte später in dieserSache lächelnd zu W.: “Das war aber das kleine Ehrenwort!”

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[Anmerkung mit Bleistift: d.h. Wolff war auch der Ansicht,dass N. sich politisch betätigt habe]. Im übrigen rühmt sichN. des Öfteren seiner politischen Beziehungen und seinerpolitischen Freunde.

6. N. erhob am 25. Oktober [19]33 in Gegenwart von Prof. P.,Prof. Glum und Frl. Kreibohm gegen W. die Beschuldigung,dieser hätte den Inhalt seines Schreibtisches kontrolliert.Einige Tage später begründete N. in Gegenwart von Prof. P.und W. diese Verdächtigung damit, dass er einmal die rechteSchublade seines Schreibtisches halbgeöffnet vorgefundenhabe. Die Absicht N.s, W. beim Generaldirektor Dr. Glumzu verleumden, geht aus der Tatsache hervor, dass es sichum eine Schublade handelte, zu der W. sowie einige Instituts-Mitglieder jederzeit Öffnungsrecht hatten. In der Schubladelagen verabredungsgemäss der Schlüssel zum Schrank desgemeinsamen Dienstzimmers W.-N., sowie ein Buch, dessenBenutzung W. genau so zustand wie N.

7. Am 25. Oktober [19]33 hat N. vor Prof. P. und vor demGeneraldirektor Glum behauptet, seine Sachen würden vonandern Mitarbeitern durchstöbert. An seinem Schreibtischseien ihm Schriftstücke entwendet und in einer Schubladedes Luftlabors abgelegt worden, offenbar in der Absicht, dasssie bei dem Sammler selbst nicht gefunden werden könnten.Diese Behauptungen hat N. aufgestellt, obwohl er nachweis-lich genau wusste, dass die angeblich entwendeten Papiereauf ganz harmlose Weise in jene Schublade des Luftlaborsgelangt sind.N. hat vor einigen Jahren an den früheren Doktoranden Wendt(heute Assistent in Clausthal) einen Tisch verliehen und hatin Verabredung mit Wendt seine Sachen in der Schubladegelassen. Der Tisch wurde später von einem anderen Dok-toranden verwendet, der die N.schen Gegenstände AnfangSeptember [19]33 in jener Schublade des Luftlabors ablegte.Wie aus einem Schreiben N.s an Wendt hervorgeht, das inder Anlage beigefügt ist, wusste N. bereits am 10.10. [19]33,dass die in Frage stehenden Schriftstücke [Anmerkung mitBleistift: wahrscheinlich] aus dem von Wendt benutzten Tischstammten. Er vermutete sogar, er habe Wendt die Papiereseinerzeit selbst überlassen. Auf N.s Anfrage hat Wendt, wieer angibt, sehr bald geantwortet, seines Wissens habe N.die Sachen in dem verborgten Tisch liegen lassen. Selbstwenn N. bis zum 25.10. [1933] die Antwort von Wendtnicht erhalten haben sollte, was höchst unwahrscheinlich ist,stellt N.s Behauptung vor dem Institutschef und dem Gen-eraldirektor, ihm seien aus seinem Schreibtisch Schriftstückeentwendet worden, eine ganz böswillige Verleumdung seinerMitarbeiter dar.

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