Experimental Study on the Effects of Artificial Vegetation Density on Gravity Current's flow Characteristics

Gravity current is one of the most important factors in sedimentation and reduction of life expectancy of reservoirs. Forehead part of gravity currents is one of the important parts of these currents that are under influence of many factors. The present research has surveyed the effects of vegetation cover in reducing the velocity of forehead gravity current. To do so، the gravity current is entered the flume with 10، 20، 30 and 40 g/l concentration. Then، vegetation covers with 15 and 20 cm heights and five densities of 0. 6، 0. 8، 1. 0، 1. 2، and 1. 4 percent are located across the currents. Measuring the velocity is done in 6 sections of 5 cm distance. The vertical concentration profile is measured in 3 sections with 1m distance. The results showed that as the density of vegetation cover with different heights increases، the development velocity of current proportion to smooth bed reduces to 13 to 28. 5 % and also the gravity current concentration reduces between 53. 54 to 81. 28 %. The 1. 4% density is the most effective density for reducing velocity and concentration of forehead gravity current. Finally، a relation has been presented for calculating the velocity in smooth bed and the vegetation cover beds with different densities.