Validation of the Numerical Model for Submerged Flow Discharge Prediction Based on Experimental Measurements

Document Type : Research Paper

Authors

1 Department of Arid and Mountainous Region Reclamation, Faculty of Natural Resources, University of Tehran, Karaj, Iran.

2 Hydraulic and Aquatic Environment Engineering Research Institute, Water Research Institute, Ministry of Energy, Tehran, Iran.

3 Department of Rangeland and Watershed Management (Nature Engineering), Faculty of Agriculture, Fasa University, Fasa, Iran.

10.22059/jwim.2026.411597.1291

Abstract

Accurate discharge measurement under submerged flow conditions remains a major challenge in irrigation and drainage networks. Portable SMBF flumes, despite their widespread application, experience reduced accuracy under submergence conditions. In this study, the hydraulic performance of an SMBF flume under submerged conditions was evaluated through an integrated experimental and numerical approach using the Flow-3D simulator. Experiments were conducted in a rectangular flume with contraction ratios of (r=0.342) and (r=0.561). In the numerical modeling framework, the RNG turbulence model and the Volume of Fluid (VOF) method were employed to accurately capture the free-surface dynamics. Model performance was assessed using RMSE, NSE, the Kling–Gupta Efficiency (KGE) index, and a systematic mesh sensitivity analysis. The results indicated that the contraction ratio (r=0.342) showed the best agreement with experimental data, while increasing the contraction ratio to (r=0.561) led to a reduction in model accuracy. Furthermore, an optimal grid configuration with a cell size of approximately one hundredth of a meter and a total number of cells between 105× 7/5 and 106×1/1 provided a suitable balance between numerical accuracy and computational cost. The main novelty of this study lies in presenting an integrated framework combining three-dimensional numerical modeling, mesh sensitivity analysis, and the application of the KGE index for multi-dimensional performance evaluation under submerged flow conditions. This approach enables simultaneous assessment of accuracy, stability, and variability of flow. The findings can be directly applied to the calibration of SMBF flumes and the improvement of discharge measurement accuracy in irrigation networks.

Keywords

Main Subjects

References

  1. Addor, N., Fowler, K. J., & Clark, M. P. (2013). Hydrologic model performance evaluation: Experience with multi‑objective diagnostics and hydrologic signatures. Hydrology and Earth System Sciences, 17(1), 111-128.
  2. Aminpour, Y., Vatankhah, A. R., & Farhoudi, J. (2020). Experimental modeling of flumes with two semi cylinder contractions (free and submerged flows). Flow Measurement and Instrumentation, 76, 101844.
  3. Asadi, M., Koochakzadeh, S., & Sotudenia, M. (2011). Water Measurement Manual, Iranian National Committee on Irrigation & Drainage (IRNCID), Tehran, Iran. (In Persian).
  4. Clemmens, A. J., Wahl, T. L., Bos, M. G., & Replogle, J. A. (2001). Water measurement with flumes and weirs (ILRI Publication 58). International Institute for Land Reclamation and Improvement (ILRI).
  5. Fleit, G., Baranya, S., & Bihs, H. (2018). CFD modeling of varied flow conditions over an ogee‑weir. Periodica Polytechnica Civil Engineering, 62(1), 26-32.
  6. García‑Alén, M., et al. (2021). Numerical modeling of submerged weir flows in complex geometries. Journal of Hydraulic Research, 59(4), 501-515.
  7. Guan, D., et al. (2019). Experimental and numerical study of sediment transport downstream of submerged weirs. Water, 11(9), 1746.
  8. Gupta, H. V., Kling, H., Yilmaz, K. K., & Martinez, G. F. (2009). Decomposition of the mean squared error and NSE performance criteria: Implications for improving hydrological modelling. Journal of Hydrology, 377(1-2), 80-91.
  9. Herrera‑Granados, O. (2021). Numerical analysis of flow behavior in a rectangular channel with submerged weirs. Water, 13(10), 1396.
  10. Kolavani, F. L., Bijankhan, M., Di Stefano, C., Ferro, V., & Mazdeh, A. M. (2019). Experimental study of central baffle flume. Journal of Irrigation and Drainage Engineering, 145(3), 04019002.
  11. Kolavani, L. F., Bijankhan, M., Di Stefano, C., Ferro, V., & Mazdeh, A. M. (2018). Flow measurement using circular portable flume. Flow Measurement and Instrumentation, 62, 76-83.
  12. Kraatz, D. B., & Mahajan, I. K. (1975). Small Hydraulic Structures (FAO Irrigation and Drainage Paper No. 26). Food and Agriculture Organization of the United Nations.
  13. Maghsoodi, S., et al. (2012). 3D simulation of flow over submerged weirs using CFD. Journal of Hydraulic Engineering, 138(3), 234-243.
  14. Moriasi, D. N., Arnold, J. G., Van Liew, M. W., Bingner, R. L., Harmel, R. D., & Veith, T. L. (2007). Model evaluation guidelines for systematic quantification of accuracy. Transactions of the ASABE, 50(3), 885-900.
  15. Nash, J. E., & Sutcliffe, J. V. (1970). River flow forecasting through conceptual models. Journal of Hydrology, 10(3), 282-290.
  16. Pedersen, O., & Rüther, N. (2016). Numerical modeling of submerged flow over ogee‑weirs. In River Flow 2016: Proceedings of the International Conference on Fluvial Hydraulics (pp. 249-256).
  17. Samani, Z. (2017). Three simple flumes for flow measurement in open channels. Journal of Irrigation and Drainage Engineering, 143(6), 04017010.
  18. Samani, Z., & Magallanez, H. (1993). Modified circular flume for trapezoidal channels. Journal of Irrigation and Drainage Engineering, 119(6), 1023-1031.
  19. Samani, Z., Jorat, S., & Yousaf, M. (1991). Hydraulic characteristics of a circular flume. Journal of Irrigation and Drainage Engineering, 117(4), 558-566.
  20. Sun, B., Yang, L., Zhu, S., Zhang, H., Zhang, C., & Zhang, J. (2020). Experimental and numerical investigation of flow measurement mechanism and hydraulic performance of portable pillar-shaped flumes in trapezoid channels. Shock and Vibration, 8815957.
  21. Willmott, C. J., & Matsuura, K. (2005). Advantages of the mean absolute error (MAE) over RMSE. Climate Research, 30(1), 79-82.
  22. Yarahmadi, N., & Vatankhah, A. R. (2021). Experimental study on rectangular cut-throated flume: Effects of flume wall slopes and channel longitudinal slope. Flow Measurement and Instrumentation, 79, 101919.
  23. Yilmaz, K. K., Gupta, H. V., & Wagener, T. (2008). A process‑based diagnostic approach to model evaluation: Application to the NWS distributed hydrologic model. Water Resources Research, 44(9), W09417.
Water and Irrigation Management
Volume 16, Issue 1
July 2026
Pages 69-79

Files

Share

How to cite

Statistics