Analiza nestacionarnih režima rada u vrelovodnim mrežama

Mihaljević, Ivica (1998) Analiza nestacionarnih režima rada u vrelovodnim mrežama. = Scientific master's thesis , Sveučilište u Zagrebu, Fakultet strojarstva i brodogradnje, UNSPECIFIED. Mentor: Doliner, Zdravko.

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Abstract (Croatian)

Polazeći od osnovnih jednadžbi dinamike fluida izvodi se hidrodinamički model jednodimenzionalnog nestacionarnog viskoznog strujanja slabo stlacivog fluida pri konstantnoj temperaturi u elastičnom cjevovodu kruto vezanom za podlogu. Primjenom metode karakteristika parcijalne diferencijalne jednadžbe hidrodinamičkog modela se prevode u obične diferencijalne jednadžbe koje se rješavaju numeričkom postupkom konačnih razlika uz uvjet poznavanja početnih i graničnih uvjeta. Početne uvjete predstavljaju rezultati proračuna stacionarnog strujanja koje se provodi uz pomoć kompjuterskog programa utemeljenog na metodi Hardy-Crossa. Granični uvjeti dobiveni su modeliranjem elemenata koji se uglavnom pojavljuju u vrelovodnim mrežama i sastavni su dio programa razvijenog za proračun nestacionarnog strujanja. Ocjena točnosti numeričkog postupka variranjem prostorno-vremenskog koraka integracije i testiranje ispravnosti programa za nestacionarno strujanje provedeno je na primjeru hidrauličkog udara u jednostavnom cjevovodu s poznatim analitičkim rješenjem. Testiranje je pokazalo da se najbolji rezultati dobiju kada elementi cijevne mreže imaju jednaku duljinu i kada se usvoji vremenski korak integracije prema kriteriju Lewy-Couranta. Pomoću razvijene metode obavljena je numerička analiza nestacionarnih pojava, tj. karakterističnih situacija hidrauličkog udara, u tipičnoj vrelovodnoj mreži urbane sredine. lz provedene analize nestacionarnog strujanja fluida slijedi da je ona neophodna i nužna ukoliko se želi ispravno definirati zaštita mreže od hidrauličkog udara.

Abstract

Starting from the basic equations of Fluid Mechanics, Hydrodynamic Model of one-dimensional unsteady viscosity isotermic weak compressible fluid flow in elastic pipes which is solid conected to base, was derived. The method of characteristics was applied for translating partial differential equations into simple differential equations which was solved with numerical finite difference method with condition of knowing initial and limited condition. A computer program based on Hardy-Cross method was developed to calculate steady fluid flow which results represented initial condition. Limited conditions were obtained by modelling elements which apears mostly in hot-water heating net and it was component part of program developed for calculation unsteady fluid flow. Estimation of accuracy numerical procedure through variation of space-time step of integration and testing accuracy for program unsteady fluid flow were relised on example of waterhammer in simple pipes with knowning analytical solution. Testing indicate the best results were got when pipe network's elements had equal length and when accepted to criterion by Lewy-Courant. The numerical analysis unsteady fluid flow, i.e., characteristical situations of waterhammer in tipical hot-water heating net at city environment, was done with developed method. From realised analysis unsteady fluid flow follows it is indispensable and necessarity if there is wish for correctly defining protection of network from waterhammer.

Item Type: Thesis (Scientific master's thesis)
Uncontrolled Keywords: mehanika fluida; nestacionarno strujanje; hidraulički udar; metoda karakteristika; vrelovodna mreža
Divisions: 500 Department of Energy, Power Engineering and Environment > 510 Power Engineering and Energy Management Chair
Date Deposited: 22 Sep 2014 18:00
Last Modified: 16 Oct 2015 13:20
URI: http://repozitorij.fsb.hr/id/eprint/60

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