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Deltar

Summary

The Deltar (Delta Getij Analogon Rekenmachine, English: Delta Tide Analogue Calculator) was an analogue computer used in the design and execution of the Delta Works from 1960 to 1984. Originated by Johan van Veen, who also built the initial prototypes between 1944 and 1946, its development was continued by J.C. Schönfeld and C.M. Verhagen after van Veen's death in 1959.

Room view - Deltar analogue computer at the DIV of Rijkswaterstaat in 1984
The Deltar (27 January 1972)
Layout of the Deltar.
1. Analog river sections
2. Peripheral equipment (Punched tape)
3. Operator controls
4. Measuring controls
5. Analog output (recorders)
6. Digital output (punched tape)
7. Design table (configuration of river setup)
8. Wind generator.
The connection table of the Deltar for the construction of river configurations

The Deltar was first put to use in 1960, and was the successor to a previous analogue computer, the larger Electrisch model van waterlopen (English: Electric model of watercourses).[1]

The Deltar was specifically designed and built to perform complex calculations necessary to predict tidal movements and the effects of interventions such as the construction of compartmentalisation dams in the Delta area of the Netherlands. The Deltar's design was based on the hydraulic analogy between the phenomena of water and electricity. Analogous to water level, flow, inertia, and water storage, the design of the computer used electrical phenomena such as voltage, current, self-inductance, and capacitance.

History edit

Tidal calculations had been a focus of engineering research in the Netherlands for much of the early 20th century. In 1916, Gerard Henri de Vries Broekman had suggested a practical method for the calculation of tidal levels.[2] In 1926, Hendrik Lorentz had developed two methods for the prediction of tidal levels for the Zuiderzee Works.[3]

The methodologies for solving differential equations of tidal motion were continuously researched and improved in the years after this, notably by J.P. Mazure,[4] H.J. Stroband,[5][6][7] Jo Johannis Dronkers,[8] H. Holsters,[9] and Johan Christoph (J.C.) Schönfeld.[10]

In the 1930s, Johan van Veen worked on a model to compare tidal currents with electrical currents. Despite initial scepticism about its reliability, van Veen continued to develop his 'electrical method', which he described in an article in the Dutch journal De Ingenieur as a 'simple engineering method' with 'relatively great accuracy'.[11][12]

His method stood in opposition to the more mathematical methods for tidal calculations, such as those of Dronkers, which required complicated mathematical effort. Dronkers had published several papers on tidal calculations, leading up to his magnum opus, Tidal computations in rivers and coastal waters, in 1964. It remains a benchmark in the field of tidal calculation theory, and led to the award of the Conrad Medal by the Royal Netherlands Institute of Engineers to Dronkers in 1965.[13]

Dronkers' computational approach, though rigorous, was criticised by van Veen for its complexity and computational demands, which he believed could hinder timely practical applications.[14] The Deltar, by comparison, offered a fast and accurate method to undertake tidal calculations.[14]

After the North Sea flood of 1953, the Deltacommissie (English: Delta Commission), led by A.G. Maris, the Director-General of Rijkswaterstaat, was established. This commission was tasked by the Minister of Transport and Water Management to develop plans to prevent such disasters in the future. Although a Delta Plan had been conceived by van Veen before the flood, this event expedited the decision to progress it, with the Dutch coastline to be shortened by approximately 700 kilometres. The scale and complexity of the Delta Works meant that the reduction in calculation time offered by the Deltar, compared with manual calculation methods, would be advantageous.[15][16]

System overview edit

 
An engineer configuring the connection table on the Deltar (1984)
 
The Deltar's 120 computing modules (1967)
 
A computing module from the Deltar analogue computer

The Deltar, an advanced system designed for simulating tides and analysing riverine environments, employed electrical quantities to translate tidal data, river flows, and environmental factors into an analogue format. This process enabled dynamic modelling of time-varying elements, vital for fluid dynamics simulations in natural settings.[17]

Comprising several sections, each representing a different part of the studied river system, the Deltar needed initial configuration with specific values to accurately simulate each river segment. Inputs like changing tide levels and wind conditions, often encoded on punched tapes, were converted into electrical signals for simulation.[17]

The machine's output system recorded the simulations, offering insights into water flow and currents. The Deltar's computing speed was adjusted through a time scale setting, managing the balance between computational power and the speed of data input and output.[1][17][18]

Each module in the Deltar replicated water flow and levels at both ends of a river segment, using electrical currents and voltages. The central computing elements, the operational amplifiers, continuously solved interconnected first-order differential equations.[1]

Structured in 3 groups of 40 units, the Deltar was equipped with the necessary input and output tools. Each unit represented a section of a river, allowing for simultaneous investigations of up to 3 tidal problems. The analogue sections were set up to immediately reflect a river section's hydraulic properties - like length, width, depth, and resistance coefficient.[16][19]

Manual and automatic adjustments were features of the Deltar. Basic settings were manually inputted, while changes in water height triggered automatic adjustments via servomotor-controlled resistors in each module. This ensured dynamic reflection of water level changes in simulations.[1]

The Deltar's mechanical function generator, driven by a servomotor spindle, was essential for accurately modelling water behaviour in each river segment. The required low drift and high common-mode rejection of the operational amplifiers were achieved using mirror galvanometer-based amplifiers. Four such amplifiers were in each module, alongside an ECC81 dual triode vacuum tube in the servo circuit, ensuring precision and stability.[18]

Capable of running simulations at 100 times real-time speed, the Deltar was versatile and allowed a wide range of adjustable hydraulic properties, allowing it to be used for diverse river types and layouts.[20][21]

Computational tasks edit

The Deltar's first major assignment was to study the tidal movement in the North Delta area during and after the execution of the Delta Plan. It was also used for:[22][23][24][25][26]

Current status edit

Despite its advanced capabilities, the advent of digital computing, exemplified by the Electrologica X1, soon overshadowed the Deltar's analogue methodology.[18] After 1984, the system was dismantled and almost entirely lost. However, four units are known to have been preserved, three of which are on display at Deltapark Neeltje Jans, and one at the Computer Museum of the University of Amsterdam.[1]

See also edit

References edit

  1. ^ a b c d e "Deltar computer". University of Amsterdam. Retrieved 28 December 2023.
  2. ^ de Vries Broekman, G.H. (1916). "Invloed van eb en vloed op de benedenrivieren" [Influence of ebb and flow on the lower rivers]. De Ingenieur (in Dutch) (29).
  3. ^ Lorentz, H.A.; Wortman, H.; van Everdingen, E.; Stoel, W.F. (1926). Verslag van de commissie Lorentz (gevolgen afsluiting Zuiderzee op het getij) [Report of the Lorentz Committee (Effects of the Closure of the Zuiderzee on the Tide)] (in Dutch). Algemene Landsdrukkerij. Retrieved 28 December 2023.
  4. ^ Mazure, J.P. (1937). De berekening van getijden en stormvloeden op benedenrivieren [The Calculation of Tides and Storm Surges in Lower Rivers] (PhD thesis) (in Dutch). TU Delft. Retrieved 28 December 2023.
  5. ^ Stroband, H.J. (1945). "De voortplanting van het getij bepaald met behulp van de electrotechniek : 1e stuk" [The propagation of the tide determined using the electro technique: 1st piece]. Rijkswaterstaat Publications Platform (in Dutch). Retrieved 28 December 2023.
  6. ^ "Verklaring overbrenging collectie Van Veen van Rijksinstituut voor Kust en Zee te Den Haag naar het Nationaal Archief te Den Haag" [Declaration transfer collection Van Veen of the National Institute for Coast and Sea in The Hague to the National Archives in The Hague]. Rijkswaterstaat Publications Platform (in Dutch). Retrieved 28 December 2023.
  7. ^ Stroband, H.J. (1943). "Stormvloedsberekening met de sinusoidale methode" [The calculation of tidal surges by the sinusoidal method]. Rapport Studiendienst (in Dutch). 's-Gravenhage: Rijkswaterstaat.
  8. ^ Dronkers, J.J. (1949). "De exacte methode voor getijberekening met als toepassing de berekening van de getijvoortplanting bij enkele theoretische stormvloeden" [The exact method of tidal calculation with examples of its application to the calculation of several theoretical tide surges]. Rapport Studiendienst (in Dutch). 's-Gravenhage: Rijkswaterstaat.
  9. ^ Holsters, H. (1953). "Le calcul du mouvement non permanent dans les rivières par la méthode dite des "lignes d'influence"" [Calculation of non-permanent flow in rivers by the method known as "influence lines"]. La Houille Blanche (in French). 39 (4): 495–509. doi:10.1051/lhb/1953044. ISSN 0018-6368. Retrieved 28 December 2023.
  10. ^ Schönfeld, J.C. (1951). Propagation of tides and similar waves. Staatsdrukkerij en Uitgeversbedrijf. Retrieved 28 December 2023.
  11. ^ van Veen, J. (1947). "Analogy between tides and AC electricity". The Engineer (Oct/Dec 1947): 498–499, 520–521, 544–545. Retrieved 28 December 2023 – via TU Delft Repository.
  12. ^ van Veen, J. (1937). "Getijstroomberekening met behulp van wetten analoog met die van Ohm en Kirchhoff" [Tidal current calculation using laws analogous to those of Ohm and Kirchhoff]. De Ingenieur (in Dutch) (19).
  13. ^ Dronkers, J.J. (1964). Tidal computations in rivers and coastal waters. Amsterdam; New York: North-Holland Pub. Co.; Interscience Publishers. Retrieved 28 December 2023.
  14. ^ a b Van Veen, J. (1946). "Electrische nabootsing van getijden: Commentaar van dr J. J. Dronkers, met naschrift van de auteur" [Electrical Simulation of Tides: Commentary by Dr. J. J. Dronkers, with Postscript from the Author]. De Ingenieur (in Dutch) (17). Koninklijk Instituut van Ingenieurs: 70–78. Retrieved 28 December 2023.
  15. ^ Maris, A.G.; Van Veen, J.; De Vries, J.W.; Dibbits, H.A.M.C. (24 February 1956). "Het deltaplan en zijn verschillende facetten" [The Delta Plan and Its Various Aspects] (in Dutch). KiVI-NIRIA. Retrieved 27 December 2023.
  16. ^ a b Schönfeld, J.C.; Verhagen, C.M. (1957). "Development of the tidal analogue technique in Holland". Second International Analogue Computation Meeting. Straatsburg.
  17. ^ a b c Schönfeld, J.C.; Stroband, H.J. (1961). "Rijkswaterstaat getijonderzoek door middel van de hydraulisch-elektrische analogie" [Rijkswaterstaat tide research by means of the hydraulic-electric analogy]. Rapport Deltacommissie. Deel 4. Bijdragen 3: Beschouwingen over stormvloeden en getijbeweging (Deltacommission Report. Part 4. Contributions 3: Considerations on Storm Surges and Tidal Movement). (in Dutch). 4 (3). Delft: Rijkswaterstaat: 209–231 – via TU Delft Repository.
  18. ^ a b c Van Den Ende, J. (1992). "Tidal calculations in the Netherlands, 1920-60". IEEE Annals of the History of Computing. 14 (3): 23–33. doi:10.1109/85.150066. ISSN 1058-6180. Retrieved 28 December 2023 – via IEEE Computer Society.
  19. ^ Schönfeld, J.C. (1951). "Propagation of tides and similar waves". Staatsdrukkerij- en uitgeversbedrijf Den Haag. Retrieved 28 December 2023 – via TU Delft Repository.
  20. ^ Verhagen, C.M. (1957). "Symposium over elektronische analogon machines: I - Principes en mogelijkheden van elektronische analogon machines" [Symposium on Electronic Analogue Machines: I - Principles and Possibilities of Electronic Analogue Machines]. De Ingenieur (in Dutch). 69 (27): 61–69.
  21. ^ Verhagen, C.M. (1957). "Symposium over elektronische analogon machines: II - De fouten in elektronische analogon machines" [Symposium on Electronic Analogue Machines: II - Errors in Electronic Analogue Machines]. De Ingenieur (in Dutch). 69 (30): 71–74.
  22. ^ "Getijonderzoek door middel van de hydraulisch-elektrische analogie" [Tidal Research through Hydraulic-Electric Analogy]. Rapport Deltacommissie Deel 4 Bijdrage III.8 (in Dutch). 1960.
  23. ^ Schönfeld, J.C. "De getijrekenmachine Deltar" [The Tidal Computing Machine Deltar]. Natuurkundige Voordrachten, Nieuwe Reeks (in Dutch). 1962–1963 (41).
  24. ^ Stroband, H.J. (1970). "De Deltar" [The Deltar]. Weg en Waterbouw (in Dutch) (30/12): 429–431.
  25. ^ Maris, A.G.; De Blocq van Kuffeler, V.J.P.; Harmsen, W.J.H.; Jansen, P.P.; Nijhoff, G.P.; Thijsse, J.T.; Verloren van Themaat, R.; De vries, J.W.; Van der Wal, L.T. (1961). "Rapport Deltacommissie. Deel 1: Eindverslag en interimadviezen" [Report of The Delta Commission. Part 1: Final report and interim advice]. Deltacommissie (in Dutch). Retrieved 28 December 2023.
  26. ^ Huis in 't Veld, J. C.; Stuip, J.; Walther, A.W.; van Westen, J.M. (1987). The Closure of tidal basins: closing of estuaries, tidal inlets, and dike breaches (2nd ed.). Delft, the Netherlands: Delft University Press. ISBN 90-6275-287-X. OCLC 18039440. Retrieved 28 December 2023.

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