Prediction of boundary shear stress distribution in straight open channels using velocity distribution
Conventional methods for measuring local shear stress on the wetted perimeter of open channels are related to the measurement of the very low velocity close to the boundary. Measuring near-zero velocity values with high fluctuations has always been a difficult task for fluid flow near solid boundari...
| Main Authors: | , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Elsevier
2021-06-01
|
| Series: | Water Science and Engineering |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S1674237021000223 |
| _version_ | 1818643233241038848 |
|---|---|
| author | Behzad Malvandi Mahmoud F. Maghrebi |
| author_facet | Behzad Malvandi Mahmoud F. Maghrebi |
| author_sort | Behzad Malvandi |
| collection | DOAJ |
| description | Conventional methods for measuring local shear stress on the wetted perimeter of open channels are related to the measurement of the very low velocity close to the boundary. Measuring near-zero velocity values with high fluctuations has always been a difficult task for fluid flow near solid boundaries. To solve the observation problems, a new model was developed to estimate the distribution of boundary shear stress from the velocity distribution in open channels with different cross-sectional shapes. To estimate the shear stress at a point on the wetted perimeter by the model, the velocity must be measured at a point with a known normal distance to the boundary. The experimental work of some other researchers on channels with various cross-sectional shapes, including rectangular, trapezoidal, partially full circular, and compound shapes, was used to evaluate the performance of the proposed model. Optimized exponent coefficients for the model were found using the multivariate Newton method with the minimum of the mean absolute percentage error (MAPE) between the model and experimental data as the objective function. Subsequently, the calculated shear stress distributions along the wetted perimeter were compared with the experimental data. The most important advantage of the proposed model is its inherent simplicity. The mean MAPE value for the seven selected cross-sections was 6.9%. The best results were found in the cross-sections with less discontinuity of the wetted perimeter, including the compound, trapezoidal, and partially full circular pipes. In contrast, for the rectangular cross-section with an angle between the bed and walls of 90°, MAPE increased due to the large discontinuities. |
| first_indexed | 2024-12-16T23:55:42Z |
| format | Article |
| id | doaj.art-9fb040a4858041bbac57c86c0f050203 |
| institution | Directory Open Access Journal |
| issn | 1674-2370 |
| language | English |
| last_indexed | 2024-12-16T23:55:42Z |
| publishDate | 2021-06-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Water Science and Engineering |
| spelling | doaj.art-9fb040a4858041bbac57c86c0f0502032022-12-21T22:11:13ZengElsevierWater Science and Engineering1674-23702021-06-01142159166Prediction of boundary shear stress distribution in straight open channels using velocity distributionBehzad Malvandi0Mahmoud F. Maghrebi1Department of Civil Engineering, Ferdowsi University of Mashhad, Mashhad 91775-1111, IranCorresponding author.; Department of Civil Engineering, Ferdowsi University of Mashhad, Mashhad 91775-1111, IranConventional methods for measuring local shear stress on the wetted perimeter of open channels are related to the measurement of the very low velocity close to the boundary. Measuring near-zero velocity values with high fluctuations has always been a difficult task for fluid flow near solid boundaries. To solve the observation problems, a new model was developed to estimate the distribution of boundary shear stress from the velocity distribution in open channels with different cross-sectional shapes. To estimate the shear stress at a point on the wetted perimeter by the model, the velocity must be measured at a point with a known normal distance to the boundary. The experimental work of some other researchers on channels with various cross-sectional shapes, including rectangular, trapezoidal, partially full circular, and compound shapes, was used to evaluate the performance of the proposed model. Optimized exponent coefficients for the model were found using the multivariate Newton method with the minimum of the mean absolute percentage error (MAPE) between the model and experimental data as the objective function. Subsequently, the calculated shear stress distributions along the wetted perimeter were compared with the experimental data. The most important advantage of the proposed model is its inherent simplicity. The mean MAPE value for the seven selected cross-sections was 6.9%. The best results were found in the cross-sections with less discontinuity of the wetted perimeter, including the compound, trapezoidal, and partially full circular pipes. In contrast, for the rectangular cross-section with an angle between the bed and walls of 90°, MAPE increased due to the large discontinuities.http://www.sciencedirect.com/science/article/pii/S1674237021000223Open channelBoundary shear stressViscous shear stressVelocity distributionVelocity gradient |
| spellingShingle | Behzad Malvandi Mahmoud F. Maghrebi Prediction of boundary shear stress distribution in straight open channels using velocity distribution Water Science and Engineering Open channel Boundary shear stress Viscous shear stress Velocity distribution Velocity gradient |
| title | Prediction of boundary shear stress distribution in straight open channels using velocity distribution |
| title_full | Prediction of boundary shear stress distribution in straight open channels using velocity distribution |
| title_fullStr | Prediction of boundary shear stress distribution in straight open channels using velocity distribution |
| title_full_unstemmed | Prediction of boundary shear stress distribution in straight open channels using velocity distribution |
| title_short | Prediction of boundary shear stress distribution in straight open channels using velocity distribution |
| title_sort | prediction of boundary shear stress distribution in straight open channels using velocity distribution |
| topic | Open channel Boundary shear stress Viscous shear stress Velocity distribution Velocity gradient |
| url | http://www.sciencedirect.com/science/article/pii/S1674237021000223 |
| work_keys_str_mv | AT behzadmalvandi predictionofboundaryshearstressdistributioninstraightopenchannelsusingvelocitydistribution AT mahmoudfmaghrebi predictionofboundaryshearstressdistributioninstraightopenchannelsusingvelocitydistribution |