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Farhad Bahmanpouri
Department of Civil, Architecture and Environmental Engineering, University of Napoli “Federico II”, Napoli, Italy

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Journal article
Published: 26 April 2021 in Proceedings of the Institution of Civil Engineers - Water Management
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Some basic characteristics of a classic hydraulic jump flow over a pebbled rough bed, as well as on smooth bed as a reference, are presented in this experimental study. For the experiments, inflow Froude number Fr1 from 1.54 to 4.94 and of inflow Reynolds number Re1 from 42,000 to 230,000 were considered. Visual observations and measurements suggested some differences between the formation of a hydraulic jump on rough and smooth bed configurations, including different air entrainment processes, larger vortical structures in the roller length and stronger backward flow in the upper layer. Furthermore, the jump roller and aerated flow lengths were on pebbled rough bed shorter than on smooth bed, while the dimensionless advection velocity of large vortices was the same for both bed types. The instantaneous jump toe perimeter showed the largest variation at the largest Fr1 and on rough bed generally was larger than on smooth bed. Larger oscillations of the free-surface profile were observed on smooth bed, highlighting that roughness resulted in smaller free-surface oscillations, suggesting the higher rate of energy dissipation.

ACS Style

Farhad Bahmanpouri; Carlo Gualtieri; Hubert Chanson. Flow patterns and free-surface dynamics in hydraulic jump on pebbled rough bed. Proceedings of the Institution of Civil Engineers - Water Management 2021, 1 -18.

AMA Style

Farhad Bahmanpouri, Carlo Gualtieri, Hubert Chanson. Flow patterns and free-surface dynamics in hydraulic jump on pebbled rough bed. Proceedings of the Institution of Civil Engineers - Water Management. 2021; ():1-18.

Chicago/Turabian Style

Farhad Bahmanpouri; Carlo Gualtieri; Hubert Chanson. 2021. "Flow patterns and free-surface dynamics in hydraulic jump on pebbled rough bed." Proceedings of the Institution of Civil Engineers - Water Management , no. : 1-18.

Preprint content
Published: 04 March 2021
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When two mega rivers merge the mixing of two flows results in a highly complex three-dimensional flow structure in an area known as the confluence hydrodynamic zone. In the confluence zone, substantial changes occur to the hydrodynamic and morphodynamic features which are of significant interest for researchers. The confluence of the Negro and Solimões Rivers, as one of the largest river junctions on Earth, is the study area of the present research. During the EU-funded Project “Clim-Amazon” (2011-2015), velocity data were collected using an ADCP vessel operating under high and low flow conditions in different locations at that confluence (Gualtieri et al., 2019). By applying the Entropy theory developed by Chiu (1988) for natural channels and simplified by Moramarco et al. (2014), the two-dimensional velocity distribution, as well as depth-averaged velocity, were calculated at the different transects along the confluence zone, using only the surface velocities observation. The estimated data yielded 6.6% and 6.9% error percentage for the discharge data related to high and low flow conditions, respectively, and 8.4% and 8.3% error percentage for the velocity data related to high and low flow conditions, respectively. Regardless of the flow condition, these preliminary results also suggest the potential points at the confluence zone for the maximum local scouring. The findings of the current research highlighted the potential of Entropy theory to estimate the flow characteristics at the large river’s confluence, just starting from the measure of surface velocities. This is of considerable interest for monitoring high flows using no-contact technology, when ADCP or other contact equipment cannot be used for the safety of operators and risks for equipment loss.

 

Keywords: Amazon River, Negro/Solimões Confluence, Entropy Theory, Velocity Distribution, Local Scouring

References

Gualtieri, C., Ianniruberto, M., Filizola, N. (2019). On the mixing of rivers with a difference in density: the case of the Negro/Solimões confluence, Brazil. Journal of Hydrology, 578(11), November 2019, 124029,

Chiu, C. L. (1988). “Entropy and 2-D velocity distribution in open channels”. Journal of Hydrologic Engineering, ASCE, 114(7), 738-756

Moramarco, T., Saltalippi, C., Singh, V.P. (2004). “Estimation of mean velocity in natural channels based on Chiu’s velocity distribution equation”. Journal of Hydrologic Engineering, ASCE, 9 (1), pp. 42-50

ACS Style

Farhad Bahmanpouri; Silvia Barbetta; Carlo Gualtieri; Marco Ianniruberto; Naziano Filizola; Donatella Termini; Tommaso Moramarco. Estimating the hydrodynamic and morphodynamic characteristics using Entropy theory at the confluence of Negro and Solimões Rivers. 2021, 1 .

AMA Style

Farhad Bahmanpouri, Silvia Barbetta, Carlo Gualtieri, Marco Ianniruberto, Naziano Filizola, Donatella Termini, Tommaso Moramarco. Estimating the hydrodynamic and morphodynamic characteristics using Entropy theory at the confluence of Negro and Solimões Rivers. . 2021; ():1.

Chicago/Turabian Style

Farhad Bahmanpouri; Silvia Barbetta; Carlo Gualtieri; Marco Ianniruberto; Naziano Filizola; Donatella Termini; Tommaso Moramarco. 2021. "Estimating the hydrodynamic and morphodynamic characteristics using Entropy theory at the confluence of Negro and Solimões Rivers." , no. : 1.

Journal article
Published: 04 February 2021 in Applied Soft Computing
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A hydraulic jump is an abrupt transition between subcritical and supercritical flows which is associated with energy dissipation, air entrainment, spray, splashing, and surface waves. Both physical and numerical modeling were largely applied to study hydrodynamics, turbulence and air-entrainment in the hydraulic jump, while the literature about the application of classifier models is quite limited. Determining air-flow parameters and turbulent intensity has been merely performed by costly and time-consuming experimental methods, while this study is the first attempt to estimate the mentioned parameters using a computer-based methodology with desired precision. In the present study, air-flow parameters including void fraction (C) and bubble count rate (F), as well as turbulent intensity (Tu) on rough bed were estimated using Bayesian model averaging (BMA) and three multilayer perceptron (MLP), support vector regression (SVR) and generalized regression neural network (GRNN) as classifier models. To develop the stated models, the experimental data from Felder and Chanson (2016) were divided into four classes based on longitudinal distance from the jump toe. Results highlighted that the MLP and GRNN models have more accurate results compared to the SVR model. For F and Tu, the GRNN model and for C, the MLP model showed better performance than other models in four classes. The average acceptance rate between 15 and 30% of the BMA model performance for all classes proved the accuracy and efficiency of the proposed methodology. The average RMSE value of BMA results and the bests classifier models were 0.41 and 0.42, respectively, for the estimation of all three parameters. Results revealed that the BMA model by weighting individual classifier models could be able to estimate parameters with better accuracy than the best classifier model in each class. The significant outcome of this study is that the proposed model is able to render accurate results in a complex system such as hydraulic jump.

ACS Style

Narges Taravatrooy; Farhad Bahmanpouri; Mohammad Reza Nikoo; Carlo Gualtieri; Azizallah Izady. Estimation of air-flow parameters and turbulent intensity in hydraulic jump on rough bed using Bayesian model averaging. Applied Soft Computing 2021, 103, 107165 .

AMA Style

Narges Taravatrooy, Farhad Bahmanpouri, Mohammad Reza Nikoo, Carlo Gualtieri, Azizallah Izady. Estimation of air-flow parameters and turbulent intensity in hydraulic jump on rough bed using Bayesian model averaging. Applied Soft Computing. 2021; 103 ():107165.

Chicago/Turabian Style

Narges Taravatrooy; Farhad Bahmanpouri; Mohammad Reza Nikoo; Carlo Gualtieri; Azizallah Izady. 2021. "Estimation of air-flow parameters and turbulent intensity in hydraulic jump on rough bed using Bayesian model averaging." Applied Soft Computing 103, no. : 107165.

Journal article
Published: 19 October 2020 in Journal of Hydrology
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Disastrous floods result in severe loss of human lives and intense destruction to the infrastructure and economic activities. Furthermore, it leads to environmental and ecological damages located at the downstream area of the dam. This present study aims at investigating experimentally and numerically the sediment transport and morphological evolution of the erodible bed induced by dam-break flows. Experimental runs were conducted in a flume, specially designed for dam-break flow process, equipped with a thin vertical gate at its middle. Based upon an initial plane bed, the effect of three different compaction rates of the bed at both up-and downstream of the dam was investigated. The experimental data consistently suggested that increasing the bed compaction rate resulted in decreasing the scouring and sedimentation depth, as well as the sediment transport rate. Further, increasing the bed compaction rate led to increasing the wave-front celerity, reducing the scouring rate and the erosion depth. Both the experimental and numerical outputs highlighted the process of air entrainment at the leading edge of the wave-front. The numerical results showed that the maximum void fraction was associated with the maximum flow velocity at the zone of wave-front. Comparisons were made between the experimental results and those are provided from a numerical study using standard volume of fluid VOF method, where three different turbulence closure schemes; RNG, k-ε and k-ω, and three bed load sediment transport approaches, Van Rijn, Meyer-Peter-Muller and Nielson, were applied. Accordingly, by considering the error values in predicting the free surface height and the bed deformation, the k-ω closure model showed the highest accuracy in capturing the turbulence features while the Mayer Peter-Muller formula had the highest performance in predicting the bed deformation in non-compacted (NC) bed. Besides, the RNG closure model and Nielsen bed load formula revealed the highest accuracy in predicting the aforementioned features in a semi-compacted (SC) bed. The k-ɛ closure model and Mayer Peter-Muller formula showed the highest accuracy in reproducing the turbulence characteristics and bed profile in a fully-compacted (FC) bed.

ACS Style

Farhad Bahmanpouri; Mohammad Daliri; Alireza Khoshkonesh; Masoud Montazeri Namin; Mariano Buccino. Bed compaction effect on dam break flow over erodible bed; experimental and numerical modeling. Journal of Hydrology 2020, 594, 125645 .

AMA Style

Farhad Bahmanpouri, Mohammad Daliri, Alireza Khoshkonesh, Masoud Montazeri Namin, Mariano Buccino. Bed compaction effect on dam break flow over erodible bed; experimental and numerical modeling. Journal of Hydrology. 2020; 594 ():125645.

Chicago/Turabian Style

Farhad Bahmanpouri; Mohammad Daliri; Alireza Khoshkonesh; Masoud Montazeri Namin; Mariano Buccino. 2020. "Bed compaction effect on dam break flow over erodible bed; experimental and numerical modeling." Journal of Hydrology 594, no. : 125645.

Journal article
Published: 03 May 2018 in Geosciences
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Confluences are a common feature of riverine systems; the area of converging flow streamlines and potential mixing of separate flows. The hydrodynamics about confluences have a highly complex three-dimensional flow structure. This paper presents the results of a numerical study using the CCHE2D code to investigate the influence of junction angle and discharge ratio on the flow and erosion patterns. The hydraulic and geometric parameters which affect the maximum relative scouring depth are analyzed. The model is first calibrated and validated. Then three discharge ratios, seven junction angles and five width ratios are considered and compared. Results generally agree with experimental data and show that the process of scouring depends on all these parameters. Numerical results demonstrate that a decrease in the ratio of the tributary width to the main channel width results in an increase in the size of the separation zone. Furthermore, the increase in the width ratio leads to a decrease in the maximum depth of bed erosion. Finally, the maximum depth of bed erosion at the confluence increases with the increasing angle of the junction.

ACS Style

Javad Ahadiyan; Atefeh Adeli; Farhad Bahmanpouri; Carlo Gualtieri. Numerical Simulation of Flow and Scour in a Laboratory Junction. Geosciences 2018, 8, 162 .

AMA Style

Javad Ahadiyan, Atefeh Adeli, Farhad Bahmanpouri, Carlo Gualtieri. Numerical Simulation of Flow and Scour in a Laboratory Junction. Geosciences. 2018; 8 (5):162.

Chicago/Turabian Style

Javad Ahadiyan; Atefeh Adeli; Farhad Bahmanpouri; Carlo Gualtieri. 2018. "Numerical Simulation of Flow and Scour in a Laboratory Junction." Geosciences 8, no. 5: 162.