On the measurement of transverse shear stress on a rectangular open channel using optimal Preston tube

Abstract

The laboratory studies have been carried out in this research. After determining the sensitivity analysis of the Preston tube diameter in shear stress, four Preston tubes with external diameters of 3.2, 3.9, 4.7, and 6.3 mm were used. The aspect ratios of 2.86 to 13.95 were examined. For measuring the pressure di erence of the Preston tube, a 200 millibar di erential pressure transducer with 0.01 accuracy of the original scale was used. Laboratory results demonstrated that Preston tubes with a diameter of 3.9 mm presented the minimum di erence in the average value of the shear stress resulting from the Bechert and Patel calibration equations. Therefore, by using the Preston tube with an optimal diameter, transverse distribution of shear stress in channel beds and walls was determined. The outcome of this part of the study is two dimensionless relationships for determining the local shear stress both on the bed and wall. These relationships are a function of aspect ratio B=H and the bed relative coordinates b=B in cross-section and Z=H sidewall. The survey showed that the dimensionless bed shear stress distribution was considerably in uenced by the aspect ratio. The transverse distribution of wall shear stress was independent of the aspect ratio for B=H > 3.

Assessing Machine Learning versus Mathematical Modeling to Estimate the Transverse Shear Stress Distribution in a Rectangular Channel

“…Information on the SSD has been collected in the Lashkar-Ara and Fatahi [8] experiments of a smooth rectangular channel, performed in a flume 10-meter long, 60 cm wide and 70 cm high. All measurements were performed in the range of 11.06 to 102.38 liter per second flow rate.…”

“…The results of the best GP models and Tsallis entropy in shear stress prediction are compared with the experimental results of Lashkar-Ara and Fatahi [8] in this section. Figures 7 and 8 show the experimental results as well as SSD predictions with different models in a smooth rectangular channel for B/H equal to 2.85, 4.51, 7.14, 13.95.…”

“…Lashkar-Ara and Fatahi [8] measured transverse SSD in the channel bed and wall by using an optimal diameter Preston tube to evaluate the SSD on a rectangular open channel. The outcome of this research is two-dimensional relationships to evaluate local shear stress in both bed and wall.…”

“…This study aimed at using Tsallis entropy method to predict the SSD in smooth rectangular channel. The results of the Tsallis entropy, GP and ANFIS methods compared with experimental results of Lashkar-Ara and Fatahi [8]. Although this analysis was performed in parallel with Sheikh Khozani and Bonakdari [16] research, it can be said in a practical contrast that the data used in this study is based on the measurement of shear stress using the optimal diameter of the Preston tube, which was designed by Lashkar-Ara and Fatahi [8], so the comparison of findings is more precise and less uncertain.…”

Assessing Machine Learning versus a Mathematical Model to Estimate the Transverse Shear Stress Distribution in a Rectangular Channel

“…They examined a wide range of flow depths for each level benching and therefore it had been possible to determine the extent to which the hydraulics changes Park et al [7] utilized laboratory-scale water flume and measured the bed shear stress under high-velocity flow conditions directly. Lashkar-Ara and Fatahi [8] measured transverse SSD in the channel bed and wall by using an optimal diameter Preston tube to evaluate the SSD on a rectangular open channel. The outcome of this research is two-dimensional relationships to evaluate local shear stress in both bed and wall.…”