@article{ValeroBung2016,
  author    = {Valero, Daniel and Bung, Daniel B.},
  title     = {Development of the interfacial air layer in the non-aerated region of high-velocity spillway flows: Instabilities growth, entrapped air and influence on the self-aeration onset},
  series = {International Journal of Multiphase Flow},
  volume    = {84},
  journal   = {International Journal of Multiphase Flow},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0301-9322},
  doi       = {10.1016/j.ijmultiphaseflow.2016.04.012},
  pages     = {66 -- 74},
  year      = {2016},
  abstract  = {Self-aeration is traditionally explained by the water turbulent boundary layer outer edge intersection with the free surface. This paper presents a discussion on the commonly accepted hypothesis behind the computation of the critical point of self-aeration in spillway flows and a new formulation is proposed based on the existence of a developing air flow over the free surface. Upstream of the inception point of self-aeration, some surface roughening has been often reported in previous studies which consequently implies some entrapped air transport and air-water flows coupling. Such air flow is proven in this study by presenting measured air velocities and computing the air boundary layer thickness for a 1V:2H smooth chute flow. Additionally, the growth rate of free surface waves has been analysed by means of Ultrasonic Sensors measurements, obtaining also the entrapped air concentration. High-speed camera imaging has been used for qualitative study of the flow perturbations.},
  language  = {en}
}
@inproceedings{KerpenBungValeroetal.2016,
  author    = {Kerpen, Nils B. and Bung, Daniel B. and Valero, Daniel and Schlurmann, Torsten},
  title     = {Energy dissipation within the wave run-up at stepped revetments},
  series = {8th Chinese-German Joint Symposium on Hydraulic and Ocean Engineering, Qingdao, China},
  booktitle = {8th Chinese-German Joint Symposium on Hydraulic and Ocean Engineering, Qingdao, China},
  pages     = {6 Seiten},
  year      = {2016},
  language  = {en}
}
@inproceedings{BungValero2016,
  author    = {Bung, Daniel B. and Valero, Daniel},
  title     = {Image processing techniques for velocity estimation in highly aerated flows: bubble image velocimetry vs. optical flow},
  series = {Sustainable Hydraulics in the Era of Global Change : Proceedings of the 4th IAHR Europe Congress (Liege, Belgium, 27-29 July 2016)},
  booktitle = {Sustainable Hydraulics in the Era of Global Change : Proceedings of the 4th IAHR Europe Congress (Liege, Belgium, 27-29 July 2016)},
  editor    = {Dewals, Benjamin},
  publisher = {CRC Press},
  isbn      = {978-1-138-02977-4},
  doi       = {10.1201/b21902-31},
  pages     = {151 -- 157},
  year      = {2016},
  language  = {en}
}
@inproceedings{ValeroBungOertel2016,
  author    = {Valero, Daniel and Bung, Daniel B. and Oertel, M.},
  title     = {Turbulent dispersion in bounded horizontal jets : RANS capabilities and physical modeling comparison},
  series = {Sustainable Hydraulics in the Era of Global Change : Proceedings of the 4th IAHR Europe Congress (Liege, Belgium, 27-29 July 2016)},
  booktitle = {Sustainable Hydraulics in the Era of Global Change : Proceedings of the 4th IAHR Europe Congress (Liege, Belgium, 27-29 July 2016)},
  editor    = {Dewals, Benjamin},
  publisher = {CRC Press},
  isbn      = {978-1-138-02977-4},
  doi       = {10.1201/b21902-13},
  pages     = {49 -- 55},
  year      = {2016},
  language  = {en}
}
@inproceedings{ValeroBung2016,
  author    = {Valero, Daniel and Bung, Daniel B.},
  title     = {Interfacial velocity estimation in highly aerated stepped spillway flows with a single tip fibre optical probe and Artificial Neural Networks},
  series = {6th IAHR International Junior Researcher and Engineer Workshop on Hydraulic Structures, May 30th to June 1st 2016. L{\"u}beck, Germany},
  booktitle = {6th IAHR International Junior Researcher and Engineer Workshop on Hydraulic Structures, May 30th to June 1st 2016. L{\"u}beck, Germany},
  doi       = {10.15142/T3Q590},
  pages     = {13 Seiten},
  year      = {2016},
  abstract  = {Air-water flows can be found in different engineering applications: from nuclear engineering to huge hydraulic structures. In this paper, a single tip fibre optical probe has been used to record high frequency (over 1 MHz) phase functions at different locations of a stepped spillway. These phase functions have been related to the interfacial velocities by means of Artificial Neural Networks (ANN) and the measurements of a classical double tip conductivity probe. Special attention has been put to the input selection and the ANN dimensions. Finally, ANN have shown to be able to link the signal rising times and plateau shapes to the air-water interfacial velocity.},
  language  = {en}
}
@article{BungValero2016,
  author    = {Bung, Daniel B. and Valero, Daniel},
  title     = {Optical flow estimation in aerated flows},
  series = {Journal of Hydraulic Research},
  volume    = {54},
  journal   = {Journal of Hydraulic Research},
  number    = {5},
  publisher = {Taylor \& Francis},
  address   = {London},
  doi       = {10.1080/00221686.2016.1173600},
  pages     = {575 -- 580},
  year      = {2016},
  abstract  = {Optical flow estimation is known from Computer Vision where it is used to determine obstacle movements through a sequence of images following an assumption of brightness conservation. This paper presents the first study on application of the optical flow method to aerated stepped spillway flows. For this purpose, the flow is captured with a high-speed camera and illuminated with a synchronized LED light source. The flow velocities, obtained using a basic Horn-Schunck method for estimation of the optical flow coupled with an image pyramid multi-resolution approach for image filtering, compare well with data from intrusive conductivity probe measurements. Application of the Horn-Schunck method yields densely populated flow field data sets with velocity information for every pixel. It is found that the image pyramid approach has the most significant effect on the accuracy compared to other image processing techniques. However, the final results show some dependency on the pixel intensity distribution, with better accuracy found for grey values between 100 and 150.},
  language  = {en}
}
@article{BayonValeroGarciaBartualetal.2016,
  author    = {Bayon, Arnau and Valero, Daniel and Garcia-Bartual, Rafael and Vall{\´e}s-Mor{\´a}n, Francisco Jos{\´e} and L{\´o}pez-Jim{\´e}nez, P. Amparo},
  title     = {Performance assessment of OpenFOAM and FLOW-3D in the numerical modeling of a low Reynolds number hydraulic jump},
  series = {Environmental Modelling \& Software},
  volume    = {80},
  journal   = {Environmental Modelling \& Software},
  publisher = {Elsevier},
  address   = {Amsterdam},
  isbn      = {1364-8152},
  doi       = {10.1016/j.envsoft.2016.02.018},
  pages     = {322 -- 335},
  year      = {2016},
  abstract  = {A comparative performance analysis of the CFD platforms OpenFOAM and FLOW-3D is presented, focusing on a 3D swirling turbulent flow: a steady hydraulic jump at low Reynolds number. Turbulence is treated using RANS approach RNG k-ε. A Volume Of Fluid (VOF) method is used to track the air-water interface, consequently aeration is modeled using an Eulerian-Eulerian approach. Structured meshes of cubic elements are used to discretize the channel geometry. The numerical model accuracy is assessed comparing representative hydraulic jump variables (sequent depth ratio, roller length, mean velocity profiles, velocity decay or free surface profile) to experimental data. The model results are also compared to previous studies to broaden the result validation. Both codes reproduced the phenomenon under study concurring with experimental data, although special care must be taken when swirling flows occur. Both models can be used to reproduce the hydraulic performance of energy dissipation structures at low Reynolds numbers.},
  language  = {en}
}