Numerična analiza vpliva turbulentnega toka na obnašanje alg

Žibert, Urška

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Title:	Numerična analiza vpliva turbulentnega toka na obnašanje alg
Authors:	ID Žibert, Urška (Author) ID Ravnik, Jure (Mentor) More about this mentor...
Files:	MAG_Zibert_Urska_2017.pdf (3,09 MB) MD5: D09FF57B19BBF15CBE383712FE11B293
Language:	Slovenian
Work type:	Master's thesis/paper
Typology:	2.09 - Master's Thesis
Organization:	FS - Faculty of Mechanical Engineering
Abstract:	O obnašanju alg v turbulentnem toku še ni bilo narejenih veliko raziskav, vendar ima njihovo proučevanje vedno večji pomen zaradi škodljivosti cvetenj na okolje. Pričujoča raziskava je bila usmerjena v raziskavo obnašanja alg v turbulentnem toku in kvantifikacijo rezultatov s statističnimi orodji. Uporabljena metoda dela je bila numerični model Vreteno DNS, ki se je do sedaj uporabljal le za nežive delce. Za posamezne primere simulacije sta bili izbrani algi Microcystis flos-aquae in Planktothrix rubescens. Obravnavali smo tri primere: posamezne celice okroglih alg Microcystis flos-aquae, kolonije po 100 celic alg Microcystis flos-aquae in paličaste alge Planktothrix rubescens. Alge so bile modelirane kot togi delci s sferično obliko oziroma aproksimirane z elipsoidom. Alge smo modelirali v turbulentnem toku v kanalu, kjer je bilo strižno Reynoldsovo število 〖Re〗_τ = 150, ki se nanaša na polovično višino h in strižno hitrost u_τ. Strižna hitrost u_τ, ki temelji na povprečni strižni napetosti na steni in gostoti tekočine, je bila enaka 0,505 m/s. Polovična višina h pa je znašala 0,3 mm. Predstavljeni rezultati so na prvi pogled pri vseh treh primerih zelo podobni. Najbolj očitna podobnost med njimi je zadrževanje ob robovih kanala. Alge v sredini toka imajo najvišje hitrosti, če gledamo globinsko-hitrostne profile primerov. Hitrostni profili alg so precej podobni. Največ alg ima v vseh treh primerih hitrosti med 15 in 18 m/s. Rezultati, ki so med seboj tako podobni, dajejo slutiti, da pri algah bolj kot velikost in oblika na razporeditev v toku vpliva gostota, ki ima pri algah vrednosti, ki se med seboj ne razlikujejo veliko. Do večjih razlik med primeri bi lahko prišlo tudi pri povečanju Re-števila, kar pomeni bolj turbulentni tok, ki bi imel večji vpliv na alge.
Keywords:	matematično-fizikalni model, Vreteno DNS, alge, turbulentni tok
Place of publishing:	Maribor
Publisher:	[U. Žibert]
Year of publishing:	2017
PID:	20.500.12556/DKUM-65054
UDC:	[519.6:532.517.4]:582.263(043.2)
COBISS.SI-ID:	20526614
NUK URN:	URN:SI:UM:DK:XQBLTVO4
Publication date in DKUM:	23.03.2017
Views:	1914
Downloads:	156
Metadata:
Categories:	KTFMB - FS
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Secondary language

Language:	English
Title:	Numerical analysis of the impact of turbulent flow on the behavior of algae
Abstract:	Because of harmful effects on the environment caused by eutrophication the research of algae behaviour in turbulent flows has grown in importance. However, few studies on this topic have been made. The following study was aimed at determining the algae behaviour in turbulent flows and the quantification of the results with statistical software. The method used was the numerical model Vreteno DNS, which was until now used only on inanimate particles. Algae Microcystis flos-aquae and Planktothrix rubescens were used for the individual simulations. Three examples were addressed: individual cells of Microcystis flos-aquae, colonies of 100 cells of Microcystis flos-aquae and the filamentous Planktothrix rubescens. The algae were modelled as rigid spheres or were approximated as an ellipsoid. Algae has been modeled in turbulent flow in the channel, where the shear Reynolds number 〖Re〗_τ = 150, which refers to the half-height h and the shear velocity u_τ. The shear velocity u_τ, which is based on the average shear tension on the wall and fluid density, equals to 0,505 m/s. The half-height h equals to 0,3 mm. The results presented are at first glance similar for all examples. The most obvious similarity between the examples was the retention on the edges of the channel. When looking at the depth-velocity profiles of the examples, the algae in the middle of the flow have greater velocities. The velocity profiles are similar. The most algae have in all examples velocities between 15 and 18 m/s. The similarity of the results gives the impression that algal density, which has similar values between algae, has, rather size and shape, the greater impact on the distribution in the flow. Furthermore, greater Re would result in noticeable differences between the examples, because it would result in an increased turbulent flow which would have an increased impact on the algae.
Keywords:	mathematical-physical model, Vreteno DNS, algae, turbulent flow

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