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Climate Change Assessment Using Atmosphere-Ocean General Circulation Model) AOGCM( and Its Effect on Runoff Using HEC-HMS model
J. Abedi Koupai, A.r. Vahabi,
Volume 27, Issue 2 (9-2023)
Abstract
Awareness of water resources status is essential for the proper management of resources and planning for the future due to the occurrence of climate change in most parts of the world and its impact on different parts of the water cycle. Hence, many studies have been carried out in different regions to analyze the effects of climate change on the hydrological process in the coming periods. The present study examined the effects of climate change on surface runoff using the Atmosphere-Ocean General Circulation Model (AOGCM) in Khomeini Shahr City. The maximum and minimum temperatures and precipitation of the upcoming period (2020-2049) were simulated using a weighted average of three models for each of the minimum and maximum temperatures and precipitation parameters based on the scenario A2 and B1 (pessimistic and optimistic states, respectively) of the AOGCM-AR4 models. The LARS-WG model was also used to measure the downscaling. The HEC-HMS was used to predict runoff. The effects of climate change in the coming period (2020-2049) compared with the observation period (1971-2000), in the A2 scenario, the minimum and maximum temperatures would increase by 1.1 and 1.6 Degrees Celsius, respectively, and the precipitation would decrease 17.8 percent. In the B1 scenario, the minimum and maximum temperatures would increase by 1.1 and 1.4 degrees Celsius, respectively, and the precipitation would decrease by 13 percent. The results of runoff were different in the six scenarios in the way the most runoff reduction is related to the scenario of fixed land use and scenario A2 (22.2% reduction), and the most increase is related to the scenario of 45% urban growth and scenario B1 (5.8% increase). So, according to increase urban texture in the future and consequently enhance the volume of runoff, this volume of runoff can be used to feed groundwater, irrigate gardens, and green space in the city.

Numerical Simulation Results of Hydraulic Jump in Different Conditions of Roughness, Adverse Slope, and Positive Step
N. Pourabdollah, M. Heidarpour, Jahangir Abedi-Koupai,
Volume 27, Issue 3 (12-2023)
Abstract
Hydraulic jump is used for dissipation of kinetic energy downstream of hydraulic structures such as spillways, chutes, and gates. In the present study, the experimental measurements and numerical simulation of the free hydraulic jump by applying Flow-3D software in six different conditions of adverse slope, roughness, and positive step were compared. It should be noted that two turbulence models including k-ε and RNG were used for numerical simulation. Based on the results, simulation accuracy using the RNG model was more than the k-ε model. The statistical indices of NRMSE, ME, NS, and R2 for comparing the water surface profile were obtained at 34.3, 0.0052, 0.995, and 983 for the application of the RNG model, respectively. Also, using the RNG model, the values of these indices for the velocity profile were obtained at 14.92, 0.127, 0.9982, and 962, respectively. In general, the error of the simulated water surface and velocity profile were obtained at 5.31 and 12.4 percent, respectively. Moreover, the maximum error of the numerical simulation results of D2/D1, Lj/D2, and Lr/D1 was ±12, ±12, and 16%, respectively. Therefore, the use of Flow-3D software with the application of the RNG turbulence model is recommended for numerical simulation of the hydraulic jump in different situations.

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