TY  - GEN
AU  - Đorđević, Dejana
PY  - 2024
UR  - https://grafar.grf.bg.ac.rs/handle/123456789/3506
AB  - The double-averaging methodology (DAM) arose to respond to a need to provide 
a mathematically rigorous tool for describing spatially heterogeneous turbulent 
flows. Initial developments originate from micrometeorologists who revealed 
notable discrepancies between measured and simulated temperature and 
moisture fields above trees when using only Reynolds-averaged Navier-Stokes 
(RANS) equations with various turbulence model closures. The discrepancies were 
attributed to the spatial inhomogeneity of the flow field caused by vegetation. 
Thus, additional spatial averaging of RANS equations over horizontal planes 
sufficiently large to provide statistical averaging of all differences caused by an 
arbitrary distribution of plants and the influence of the biggest vortices responsible 
for the transfer of momentum was suggested. The advantages of using the DAM 
in open-channel hydraulics of gravel-bed rivers were recognised in the early 2000s 
when DAM was first applied and consequently improved. Open-channel vegetated 
flows are another example of spatially heterogene¬ous turbulent flows to which 
the DAM can be applied. The paper presents the results of the DoubleVeg project 
led by the author, in which a new set of equations was derived. After introducing 
the basic DAM concepts, the procedure of deriving Depth-Integrated Double
Averaged Navier-Stokes equations is presented. Consequently, the main 
challenges in solving these equations are discussed, and the results of initial testing 
of systems of homogeneous and non-homogeneous equations are shown.
PB  - University of Novi Sad,  Faculty of Civil Engineering Subotica  Kozaračka 2а, 24000 Subotica, Serbia  URL: conference.gf.uns.ac.rs
T2  - Conference Proceedings of the IX International Conference on Contemporary Achievments in Civil Engineering
T1  - On the application of the double-averaging methodology in modelling vegetated open-channel flows
EP  - 63
SP  - 29
DO  - 10.14415/CACE2024.03
ER  - 

@misc{
author = "Đorđević, Dejana",
year = "2024",
abstract = "The double-averaging methodology (DAM) arose to respond to a need to provide 
a mathematically rigorous tool for describing spatially heterogeneous turbulent 
flows. Initial developments originate from micrometeorologists who revealed 
notable discrepancies between measured and simulated temperature and 
moisture fields above trees when using only Reynolds-averaged Navier-Stokes 
(RANS) equations with various turbulence model closures. The discrepancies were 
attributed to the spatial inhomogeneity of the flow field caused by vegetation. 
Thus, additional spatial averaging of RANS equations over horizontal planes 
sufficiently large to provide statistical averaging of all differences caused by an 
arbitrary distribution of plants and the influence of the biggest vortices responsible 
for the transfer of momentum was suggested. The advantages of using the DAM 
in open-channel hydraulics of gravel-bed rivers were recognised in the early 2000s 
when DAM was first applied and consequently improved. Open-channel vegetated 
flows are another example of spatially heterogene¬ous turbulent flows to which 
the DAM can be applied. The paper presents the results of the DoubleVeg project 
led by the author, in which a new set of equations was derived. After introducing 
the basic DAM concepts, the procedure of deriving Depth-Integrated Double
Averaged Navier-Stokes equations is presented. Consequently, the main 
challenges in solving these equations are discussed, and the results of initial testing 
of systems of homogeneous and non-homogeneous equations are shown.",
publisher = "University of Novi Sad,  Faculty of Civil Engineering Subotica  Kozaračka 2а, 24000 Subotica, Serbia  URL: conference.gf.uns.ac.rs",
journal = "Conference Proceedings of the IX International Conference on Contemporary Achievments in Civil Engineering",
title = "On the application of the double-averaging methodology in modelling vegetated open-channel flows",
pages = "63-29",
doi = "10.14415/CACE2024.03"
}

Đorđević, D.. (2024). On the application of the double-averaging methodology in modelling vegetated open-channel flows. in Conference Proceedings of the IX International Conference on Contemporary Achievments in Civil Engineering
University of Novi Sad,  Faculty of Civil Engineering Subotica  Kozaračka 2а, 24000 Subotica, Serbia  URL: conference.gf.uns.ac.rs., 29-63.
https://doi.org/10.14415/CACE2024.03

Đorđević D. On the application of the double-averaging methodology in modelling vegetated open-channel flows. in Conference Proceedings of the IX International Conference on Contemporary Achievments in Civil Engineering. 2024;:29-63.
doi:10.14415/CACE2024.03 .

Đorđević, Dejana, "On the application of the double-averaging methodology in modelling vegetated open-channel flows" in Conference Proceedings of the IX International Conference on Contemporary Achievments in Civil Engineering (2024):29-63,
https://doi.org/10.14415/CACE2024.03 . .

TY  - JOUR
AU  - Đorđević, Dejana
AU  - Pokrajac, Dubravka
PY  - 2023
UR  - https://grafar.grf.bg.ac.rs/handle/123456789/3339
AB  - Sa hidrauličkog stanovišta, prostorni raspored vodene vegetacije u koritima i na obalama vodotoka je slučajan i nezavisan od karakteristika toka. Vegetacija svojim prisustvom pruža otpore kretanju vode i utiče na tran-sportne procese i procese mešanja. Proračun otvorenih tokova sa promenljivim prostornim rasporedom vege-tacije zahteva da se prilikom numeričkog modeliranja vodi računa o konvektivnim članovima, jer oni pored zavisno promenljivih sadrže i prostorno promenljivu poroznost usled prisustva vegetacije u koritu. U ovom radu se za opis linijskih otvorenih tokova sa promenljivim rasporedom vegetacije koriste trostruko osrednjene Navije-Stoksove jednačine (Depth-Integrated Double-Averaged Navier-Stokes - DIDANS equations). Prikazan je postupak njihovog numeričkog rešavanja primenom metode konačnih zapremina. Za diskretizaciju jednačina u kojima se konvektivni član piše u razvijenom obliku da bi se uzela u obzir prostorna promena poroznosti, koristi se računski postupak razdvajanja fluksova (flux-difference splitting) i prilagođena Rouova računska shema za aproksimaciju zavisno promenljivih na granicama kontrolne zapremine. Modifikovan Rouov postupak testiran je na pojednostavljenom, idealizovanom primeru homogenih DIDANS jednačina (horizontalno dno i zanemareni otpori trenja i oblika). Rezultati numeričkog modela upoređeni su sa analitičkim rešenjem za ovaj pojednostavljen slučaj, pri čemu je dobijeno odlično slaganje.
AB  - From the point of view of Engineering Hydraulics, the spatial distribution of the aquatic vegetation in the natural streams and their floodplanes is random and unrelated to the streams' flow characteristics. Aquatic vegetation enhances flow resistance and influences mixing and transport processes. Numerical simulation of open channel flows with variable spatial distribution of aquatic vegetation requires a special treatment of the advective terms, because, besides the main variables, they also contain the spatialy variable porosity due to the presence of vegetation in the channel. In this paper flow in open channels with variable spatial distribution of vegetation is described using triple-averaged Navier-Stokes equations (Depth-Integrated Double-Averaged Navier-Stokes, DIDANS equations). They are solved numerically using the finite volume method. The equations with the advective terms explicitly accounting for the spatial variation of porosity are solved by using the flux difference splitting and Roe's method for approximation of the dependent variables at the boundaries between the computational cells. The modified Roe's method is tested on an idealised case of homogeneous DIDANS equations (horizontal bed and all flow resistance terms neglected). Numerical results for this simplified case are in excellent agreement with the analytical solution.
PB  - Srpsko društvo za odvodnjavanje i navodnjavanje
T2  - Vodoprivreda
T1  - Numeričko modeliranje linijskih otvorenih tokova sa promenljivim rasporedom vegetacije
T1  - Numerical modelling of vegetated open-channel flows with arbitrary distribution of vegetation patches
EP  - 153
IS  - 325-326
SP  - 143
VL  - 55
UR  - https://hdl.handle.net/21.15107/rcub_grafar_3339
ER  - 

@article{
author = "Đorđević, Dejana and Pokrajac, Dubravka",
year = "2023",
abstract = "Sa hidrauličkog stanovišta, prostorni raspored vodene vegetacije u koritima i na obalama vodotoka je slučajan i nezavisan od karakteristika toka. Vegetacija svojim prisustvom pruža otpore kretanju vode i utiče na tran-sportne procese i procese mešanja. Proračun otvorenih tokova sa promenljivim prostornim rasporedom vege-tacije zahteva da se prilikom numeričkog modeliranja vodi računa o konvektivnim članovima, jer oni pored zavisno promenljivih sadrže i prostorno promenljivu poroznost usled prisustva vegetacije u koritu. U ovom radu se za opis linijskih otvorenih tokova sa promenljivim rasporedom vegetacije koriste trostruko osrednjene Navije-Stoksove jednačine (Depth-Integrated Double-Averaged Navier-Stokes - DIDANS equations). Prikazan je postupak njihovog numeričkog rešavanja primenom metode konačnih zapremina. Za diskretizaciju jednačina u kojima se konvektivni član piše u razvijenom obliku da bi se uzela u obzir prostorna promena poroznosti, koristi se računski postupak razdvajanja fluksova (flux-difference splitting) i prilagođena Rouova računska shema za aproksimaciju zavisno promenljivih na granicama kontrolne zapremine. Modifikovan Rouov postupak testiran je na pojednostavljenom, idealizovanom primeru homogenih DIDANS jednačina (horizontalno dno i zanemareni otpori trenja i oblika). Rezultati numeričkog modela upoređeni su sa analitičkim rešenjem za ovaj pojednostavljen slučaj, pri čemu je dobijeno odlično slaganje., From the point of view of Engineering Hydraulics, the spatial distribution of the aquatic vegetation in the natural streams and their floodplanes is random and unrelated to the streams' flow characteristics. Aquatic vegetation enhances flow resistance and influences mixing and transport processes. Numerical simulation of open channel flows with variable spatial distribution of aquatic vegetation requires a special treatment of the advective terms, because, besides the main variables, they also contain the spatialy variable porosity due to the presence of vegetation in the channel. In this paper flow in open channels with variable spatial distribution of vegetation is described using triple-averaged Navier-Stokes equations (Depth-Integrated Double-Averaged Navier-Stokes, DIDANS equations). They are solved numerically using the finite volume method. The equations with the advective terms explicitly accounting for the spatial variation of porosity are solved by using the flux difference splitting and Roe's method for approximation of the dependent variables at the boundaries between the computational cells. The modified Roe's method is tested on an idealised case of homogeneous DIDANS equations (horizontal bed and all flow resistance terms neglected). Numerical results for this simplified case are in excellent agreement with the analytical solution.",
publisher = "Srpsko društvo za odvodnjavanje i navodnjavanje",
journal = "Vodoprivreda",
title = "Numeričko modeliranje linijskih otvorenih tokova sa promenljivim rasporedom vegetacije, Numerical modelling of vegetated open-channel flows with arbitrary distribution of vegetation patches",
pages = "153-143",
number = "325-326",
volume = "55",
url = "https://hdl.handle.net/21.15107/rcub_grafar_3339"
}

Đorđević, D.,& Pokrajac, D.. (2023). Numeričko modeliranje linijskih otvorenih tokova sa promenljivim rasporedom vegetacije. in Vodoprivreda
Srpsko društvo za odvodnjavanje i navodnjavanje., 55(325-326), 143-153.
https://hdl.handle.net/21.15107/rcub_grafar_3339

Đorđević D, Pokrajac D. Numeričko modeliranje linijskih otvorenih tokova sa promenljivim rasporedom vegetacije. in Vodoprivreda. 2023;55(325-326):143-153.
https://hdl.handle.net/21.15107/rcub_grafar_3339 .

Đorđević, Dejana, Pokrajac, Dubravka, "Numeričko modeliranje linijskih otvorenih tokova sa promenljivim rasporedom vegetacije" in Vodoprivreda, 55, no. 325-326 (2023):143-153,
https://hdl.handle.net/21.15107/rcub_grafar_3339 .