Influence of Operational Timing on the Efficiency of Venting Turbidity Currents

Abstract

Reservoir sedimentation is gaining growing attention as dams are aging, due to economic and environmental consequences. Venting of turbidity currents is one of many sediment management techniques, highly recommended when water is in shortage. The venting operation is experimentally investigated using two reservoir bed slopes. The main research questions concern the opening timing of bottom outlets and the duration of venting. The timings tested are relative to the arrival of the current at the outlet. The results showed that in-time venting, synchronized with the arrival of the turbidity current at the outlet, is more efficient than early or late venting. It is recommended to start opening the gates when the turbidity current is around 300 m upstream of the outlet, so that the evacuation is synchronized with the arrival of the current at the dam. Additionally, venting should not be stopped immediately after the end of the turbidity current flow but should instead last for a certain time in order to evacuate the muddy lake depending on the outflow discharge.

Prediksi Umur Waduk Gunungrowo Setelah Pengerukan

“…Keberlanjutan waduk membutuhkan tindakan untuk menghilangkan sedimen yang ada di dalam waduk atau mengurangi pengendapan yang akan terjadi [10]. Sedimentasi waduk juga berdampak pada permasalahan ekonomi dan lingkungan [11].…”

“…Kajian penanganan sedimentasi dengan pengerukan [14]. Penelitian waktu yang tepat untuk membuka bottom outlet dan lama pelepasan sedimen pada penanganan sedimen dengan venting of turbidity currents [11]. Penelitian untuk mengembangkan metode yang efisien untuk melepaskan sedimen halus, dengan mempertahankan sedimen dalam suspensi.…”

Numerical Modeling of turbidity currents with Ansys CFX and Telemac 3D

“…Numerical models, either 1D vertical or 3D, allow to take into account complex bed topography, varying flows, sediments characteristics, etc. Many numerical studies on turbidity currents have been performed in the past using 3D CFD codes such as Ansys-CFX [8][9][10], Flow-3D [11,12], Ssim 2 [13][14][15][16][17] , Delft3D [18], Elcom [19].…”

Velocity Structure of Density Currents Propagating over Rough Beds

“…As seen in Figure 1, the vertical downstream velocity of density currents is divided into two regions: an inner region below the location of maximum velocity, which has a steep increase in velocity from the bottom to the maximum velocity, and an outer region above the maximum velocity with a negative velocity gradient. The general approach for density current studies has been simplifying the situation by regarding the bed as smooth [2,[11][12][13][14][15][16]. However, in most practical cases, these currents usually flow over surfaces that are not smooth, such as, mobile beds, obstacles, grain roughness (e.g., sand or gravel), and form roughness (e.g., ripples or dunes).…”

“…Moreover, they can represent obstacles used for partially or entirely stopping density currents transporting pollutants or hazardous materials. Therefore, studying these currents over roughness arrays can have considerable benefits for human and environmental The general approach for density current studies has been simplifying the situation by regarding the bed as smooth [2,[11][12][13][14][15][16]. However, in most practical cases, these currents usually flow over surfaces that are not smooth, such as, mobile beds, obstacles, grain roughness (e.g., sand or gravel), and form roughness (e.g., ripples or dunes).…”