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fbtwitterlinkedinvimeoflicker grey 14rssslideshare1
Sharil, Suraya
Languages: English
Types: Doctoral thesis
Subjects: TA

Classified by OpenAIRE into

arxiv: Physics::Fluid Dynamics, Physics::Geophysics
In recent years aquatic vegetation has become more accepted and important in the river restoration schemes and preserving river ecology. The purpose of this thesis is\ud to investigate the influence of emergent vegetation on velocity and turbulence fields in order to have a better understanding of the effect of vegetation on the transverse\ud mixing processes. To achieve this objective, a series of experiments was conducted in an open channel flume with emergent rigid rods in both staggered and aligned\ud arrangements. Detailed velocity, turbulence and dye tracer measurement were carried out for six vegetation densities relating to solid volume fractions (SVF) in the\ud range 0.51 % to 7.79 %. In sparse vegetation (SVF < 10 %) as expected the normalised spatially-averaged longitudinal velocity reduces as the vegetation density increases with approximately 30 % to 50 % reduction when the solid volume\ud fraction is doubled. Results indicated that in sparse vegetation, the normalised turbulence intensities increased with increasing solid volume fraction. The bulk drag\ud coefficient increased with increasing vegetation density whilst decreased with increasing stem Reynolds number. The transverse mixing coefficient increases with\ud both increasing vegetation density and stem Reynolds number. The current study showed that for sparse vegetation (SVF < 10%), the transverse mixing coefficient\ud has a stronger correlation with turbulence intensity compared to transverse shear.\ud Therefore indicating that within sparse vegetated flows, turbulence dominates over transverse shear in transverse mixing. In addition to that, transverse mixing also\ud correlate better with double-averaged turbulence intensity compared to turbulent kinetic energy. This reflects that the turbulence in the longitudinal direction plays a\ud greater contribution to the overall transverse dispersion than the contribution of the total turbulence in all three directions. Finally two vegetation transverse dispersions\ud models proposed by other researcher for randomly distributed vegetation were tested against data from the current study. Both models were found to predict reasonably\ud well.
  • The results below are discovered through our pilot algorithms. Let us know how we are doing!

    • Goring, D. and Nikora, V. (2002). Despiking Acoustic Doppler Velocimeter Data. J. Hydraul. Eng., 128(1): 117 126
    • Nepf, H. M. (2004) Vegetated Flow Dynamics. p. 137 164. In S. Fagherazzi, M. Marani, and L. Blum [eds]. Ecogeomorphology of tidal marshes. Coastal Estuar. Monogr. Ser. 59: doi: 10.1029/59CE09.
    • Tanino, Y. and Nepf, H. M. (2009) Lateral dispersion in vegetated flows: Reynolds number dependence at transitional Reynolds numbers. 33rd IAHR Congress: Water Engineering for a Sustainable Environment, Vancouver, Canada.
    • Toth, L. G., Parpala, L., Balogh, C. and Tatrai, I. and Baranyai, E. (2011) Zooplankton community response to enhanced turbulence generated by water level decrease in Lake Balaton, the largest shallow lake in Central Europe. Limnol. Oceanogr., 56(6), 2011, 2211 2222.
    • White, B. L. and Nepf, H. M. (2003) "Scalar transport in random cylinder arrays at moderate Reynolds number." Journal of Fluid Mechanics, (487): 43.
    • Wilson, C.A.M.E., Stoesser, T., Bates, P.D., and Batemann Pinzen, A. (2003) Open channel flow through different forms of submerged flexible vegetation. Journal of Hydraulic Engineering, 129(11), 847-853.
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