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Experimental Investigation of the Effect of Vertical Variation of Stem Density on Flow and Vertical Transport

Ghazvinizadeh Esfahani, Somayeh | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 39504 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Jamali, Mirmosaddegh
  7. Abstract:
  8. Presence of emergent vegetation can change the governing forces in flow through such systems and affects the turbulence structure and scalar transport. On the other hand, vertical variation of physical characteristics of stems, which is fairly observed in reality, leads to variation in frontal area and the called vertical density difference. In this study we experimentally investigate the effect of vertical density difference on both flow and vertical transport of mass. The results will be compared with theoretical predictions.
    Using rigid emergent model of cylinders as stems with step density variation in depth I simmulate field conditions considering actual variation of frontal area. Experiments are in turbulent range, Red>=480. This study has two parts. First part discusses velocity field and turbulence features of flow in canopies with vertical density variation. Velocity profile is measured with ADV. Comparison of velocity profiles with experiments and theory shows a good agreement. In the second part vertical diffusion coefficient was measured by recording movies from release of dyed solution in the canopy and using image processing technique. Experimental results indicate an increase in vertical diffusion coefficient with decrease of density in depth. Theoretical prediction which is defined for uniform density in depth has poor consistency with experimental results of this study
  9. Keywords:
  10. Image Processing ; Vegetated Flow ; Density Variation ; Vertical Diffusion

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