American Society of Civil Engineers


Experimental and Numerical Investigation of Bed-Load Transport under Unsteady Flows


by Gökçen Bombar, Ph.D., (Post-doctoral Researcher, Civil Engineering Dept., Dokuz Eylul Univ., Tinaztepe, Izmir. E-mail: gokcenbombar2@gmail.com), S¸ebnem Elçi, (Assoc. Prof., Civil Engineering Dept., Izmir Inst. of Technology, Urla, Izmir. E-mail: sebnemelci@iyte.edu.tr), Gokmen Tayfur, (corresponding author), (Professor, Civil Engineering Dept., Izmir Inst. of Technology, Urla, Izmir. E-mail: gokmentayfur@iyte.edu.tr), M. S¸ükrü Güney, (Professor, Civil Engineering Dept., Dokuz Eylul University, Tinaztepe, Izmir. E-mail: sukru.guney@deu.edu.tr), and Aslı Bor, (Research Assistant, Civil Engineering Dept., Izmir Inst. of Technology, Urla, Izmir. E-mail: aslibor@iyte.edu.tr)

Journal of Hydraulic Engineering, Vol. 137, No. 10, October 2011, pp. 1276-1282, (doi:  http://dx.doi.org/10.1061/(ASCE)HY.1943-7900.0000412)

     Access full text
     Purchase Subscription
     Permissions for Reuse  

Document type: Technical Note
Abstract: The dynamic behavior of bed-load sediment transport under unsteady flow conditions is experimentally and numerically investigated. A series of experiments are conducted in a rectangular flume (18 m in length, 0.80 m in width) with various triangular and trapezoidal shaped hydrographs. The flume bed of 8 cm in height consists of scraped uniform small gravel of D50=4.8 mm. Analysis of the experimental results showed that bed-load transport rates followed the temporal variation of the triangular and trapezoidal hydrographs with a time lag on the average of 11 and 30 s, respectively. The experimental data were also qualitatively investigated employing the unsteady-flow parameter and total flow work index. The analysis results revealed that total yield increased exponentially with the total flow work. An original expression which is based on the net acceleration concept was proposed for the unsteadiness parameter. Analysis of the results then revealed that the total yield increased exponentially with the increase in the value of the proposed unsteadiness parameter. Further analysis of the experimental results revealed that total flow work has an inverse exponential variation relation with the lag time. A one-dimensional numerical model that employs the governing equations for the conservation of mass for water and sediment and the momentum was also developed to simulate the experimental results. The momentum equation was approximated by the diffusion wave approach, and the kinematic wave theory approach was employed to relate the bed sediment flux to the sediment concentration. The model successfully simulated measured sedimentographs. It predicted sediment yield, on the average, with errors of 7% and 15% of peak loads for the triangular and trapezoidal hydrograph experiments, respectively.


ASCE Subject Headings:
Unsteady flow
Sediment transport
Bed loads
Parameters
Kinematic wave theory
Numerical models
Simulation

Author Keywords:
Unsteady flow
Sediment transport
Bed load
Unsteadiness parameter
Work flow index
Time lag
Diffusion wave
Kinematic wave theory
Numerical model
Simulation