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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 39546 (09)
- University: Sharif University of Technology
- Department: Civil Engineering
- Advisor(s): Jamali, Mirmosadegh
- Abstract:
- Numerical and laboratory models were used to investigate gravity exchange flow caused by spatial heterogeneity in water temperature, through emergent vegetation with varying diameter along their height (denoted by the parameter ) causing varying stem frontal area along vertical axis. Numerical model was used to anticipate flow characteristics and their alterations relative to non-dimensional vegetation diameter ratio. A set of Teflon dowels with various heights was used to simulate considered vegetative cross-section changes along vertical axis. Interface profile, toe velocity and flow rate were studied. Interface height and flow rate were inquired near the gate where expected to be critical. Numerical model predictions had good agreement with experimental results. All together, results showed that varying stem frontal area along vertical axis doesn’t influence flow characteristics significantly relative to case of constant vegetation frontal area. At last empirical formulas are derived to predict flow characteristics from and non-dimensional drag coefficient ( ). Predicting behavior of buoyant contaminant in vegetated canopies requires anticipating advection and longitudinal dispersion which are controlled by vegetation characteristics. A laboratory experiment was designed to study the influence of vegetation on longitudinal dispersion of floating immiscible contaminant. Lock exchange flow going through a random array of dowels was used to study flow and dispersion through vegetation. Experiments were conducted in a manner resulting in stem-Reynolds number below 200 causing stem-wake regime to be laminar. Stem density ranged between 1.5% and 6%.The longitudinal dispersion coefficients was estimated by measuring time series of variance of contaminant cloud along the array. Observation of tracer transport in laboratory matches well the theoretical predictions. For all vegetation densities, longitudinal dispersion decreases with increasing Reynolds number and for all Reynolds number, in sparse vegetation densities, dispersion coefficient doesn’t change significantly. in high densities dispersion coefficient increases severely. Dispersion due to velocity reduction behind each stem dominates total dispersion in laminar stem-wake regime with vegetation density in the range of 1.5-6%. Finally empirical equations to estimate longitudinal dispersion coefficient are presented.
- Keywords:
- Gravity Current ; Two Layer Flow ; Longitudinal Dispertion ; Vegetative Drag
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محتواي پايان نامه
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