@article{ValeroChansonBung2019, author = {Valero, Daniel and Chanson, Hubert and Bung, Daniel B.}, title = {Robust estimators for turbulence properties assessment}, pages = {1 -- 24}, year = {2019}, language = {en} } @article{ValeroChansonBung2020, author = {Valero, Daniel and Chanson, Hubert and Bung, Daniel B.}, title = {Robust estimators for free surface turbulence characterization: A stepped spillway application}, series = {Flow Measurement and Instrumentation}, volume = {76}, journal = {Flow Measurement and Instrumentation}, number = {Art. 101809}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0955-5986}, doi = {10.1016/j.flowmeasinst.2020.101809}, year = {2020}, abstract = {Robust estimators are parameters insensitive to the presence of outliers. However, they presume the shape of the variables' probability density function. This study exemplifies the sensitivity of turbulent quantities to the use of classic and robust estimators and the presence of outliers in turbulent flow depth time series. A wide range of turbulence quantities was analysed based upon a stepped spillway case study, using flow depths sampled with Acoustic Displacement Meters as the flow variable of interest. The studied parameters include: the expected free surface level, the expected fluctuation intensity, the depth skewness, the autocorrelation timescales, the vertical velocity fluctuation intensity, the perturbations celerity and the one-dimensional free surface turbulence spectrum. Three levels of filtering were utilised prior to applying classic and robust estimators, showing that comparable robustness can be obtained either using classic estimators together with an intermediate filtering technique or using robust estimators instead, without any filtering technique.}, language = {en} } @article{ValeroBung2018, author = {Valero, Daniel and Bung, Daniel B.}, title = {Reformulating self-aeration in hydraulic structures: Turbulent growth of free surface perturbations leading to air entrainment}, series = {International Journal of Multiphase Flow}, volume = {100}, journal = {International Journal of Multiphase Flow}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0301-9322}, doi = {10.1016/j.ijmultiphaseflow.2017.12.011}, pages = {127 -- 142}, year = {2018}, abstract = {A new formulation for the prediction of free surface dynamics related to the turbulence occurring nearby is proposed. This formulation, altogether with a breakup criterion, can be used to compute the inception of self-aeration in high velocity flows like those occurring in hydraulic structures. Assuming a simple perturbation geometry, a kinematic and a non-linear momentum-based dynamic equation are formulated and forces acting on a control volume are approximated. Limiting steepness is proposed as an adequate breakup criterion. Role of the velocity fluctuations normal to the free surface is shown to be the main turbulence quantity related to self-aeration and the role of the scales contained in the turbulence spectrum are depicted. Surface tension force is integrated accounting for large displacements by using differential geometry for the curvature estimation. Gravity and pressure effects are also contemplated in the proposed formulation. The obtained equations can be numerically integrated for each wavelength, hence resulting in different growth rates and allowing computation of the free surface roughness wavelength distribution. Application to a prototype scale spillway (at the Aviemore dam) revealed that most unstable wavelength was close to the Taylor lengthscale. Amplitude distributions have been also obtained observing different scaling for perturbations stabilized by gravity or surface tension. The proposed theoretical framework represents a new conceptualization of self-aeration which explains the characteristic rough surface at the non-aerated region as well as other previous experimental observations which remained unresolved for several decades.}, language = {en} } @article{BungValero2018, author = {Bung, Daniel B. and Valero, Daniel}, title = {Re-aeration on stepped spillways with special consideration of entrained and entrapped air}, series = {Geosciences}, volume = {8}, journal = {Geosciences}, number = {9}, publisher = {MDPI}, address = {Basel}, issn = {2076-3263}, pages = {Article number 333}, year = {2018}, abstract = {As with most high-velocity free-surface flows, stepped spillway flows become self-aerated when the drop height exceeds a critical value. Due to the step-induced macro-roughness, the flow field becomes more turbulent than on a similar smooth-invert chute. For this reason, cascades are oftentimes used as re-aeration structures in wastewater treatment. However, for stepped spillways as flood release structures downstream of deoxygenated reservoirs, gas transfer is also of crucial significance to meet ecological requirements. Prediction of mass transfer velocities becomes challenging, as the flow regime differs from typical previously studied flow conditions. In this paper, detailed air-water flow measurements are conducted on stepped spillway models with different geometry, with the aim to estimate the specific air-water interface. Re-aeration performances are determined by applying the absorption method. In contrast to earlier studies, the aerated water body is considered a continuous mixture up to a level where 75\% air concentration is reached. Above this level, a homogenous surface wave field is considered, which is found to significantly affect the total air-water interface available for mass transfer. Geometrical characteristics of these surface waves are obtained from high-speed camera investigations. The results show that both the mean air concentration and the mean flow velocity have influence on the mass transfer. Finally, an empirical relationship for the mass transfer on stepped spillway models is proposed.}, language = {en} } @inproceedings{BungPagliara2013, author = {Bung, Daniel B. and Pagliara, S.}, title = {Proceedings of the International Workshop on Hydraulic Design of Low-Head Structures : Aachen, Germany, February, 20-22, 2013 / D. Bung ; S. Pagliara (eds.)}, publisher = {Bundesanst. f{\"u}r Wasserbau}, address = {Karlsruhe}, isbn = {978-3-939230-04-5}, pages = {X, 230 S. + 1 CD-ROM}, year = {2013}, language = {en} } @inproceedings{SchlenkhoffBung2009, author = {Schlenkhoff, Andreas and Bung, Daniel B.}, title = {Prediction of oxygen transfer in self-aerated skimming flow on embankment stepped spillways}, series = {Water engineering for sustainable environment : 33rd IAHR congress ; 9 - 14 August 2009, Vancouver, British Columbia, Canada}, booktitle = {Water engineering for sustainable environment : 33rd IAHR congress ; 9 - 14 August 2009, Vancouver, British Columbia, Canada}, organization = {International Association for Hydraulic Engineering and Research}, isbn = {9789078046080}, pages = {1 CD-ROM}, year = {2009}, language = {en} } @inproceedings{KerpenBungSchlurmann2010, author = {Kerpen, N. B. and Bung, Daniel B. and Schlurmann, Torsten}, title = {Physical model investigations of ships passing through a lock}, series = {Hydraulic structures: useful water harvesting systems or relics? : Third International Junior Researcher and Engineer Workshop on Hydraulic Structures (IJREWHS'10) : Edinburgh, Scotland, U.K., 2-3 May 2010}, booktitle = {Hydraulic structures: useful water harvesting systems or relics? : Third International Junior Researcher and Engineer Workshop on Hydraulic Structures (IJREWHS'10) : Edinburgh, Scotland, U.K., 2-3 May 2010}, editor = {Janssen, Robert}, publisher = {School of Civil Engineeering, The University of Queensland}, address = {Brisbane}, organization = {International Junior Researcher and Engineer Workshop on Hydraulic Structures <3, 2010, Edinburgh>}, isbn = {9781742720159}, pages = {93 -- 100}, year = {2010}, language = {en} } @inproceedings{KerpenBungSchlurmann2010, author = {Kerpen, N. B. and Bung, Daniel B. and Schlurmann, Torsten}, title = {Physical model investigations of pressure distributions next to ships passing through a lock}, series = {5th Chinese-German Joint Symposium on Hydraulic and Ocean Engineering : CG JOINT 2010}, booktitle = {5th Chinese-German Joint Symposium on Hydraulic and Ocean Engineering : CG JOINT 2010}, publisher = {Univ. Press}, address = {Tianjin}, organization = {Chinese-German Joint Symposium on Hydraulic and Ocean Engineering <5, 2010, Tianjin>}, isbn = {978-7-5618-3671-2}, pages = {514 -- 519}, year = {2010}, language = {en} } @article{ValeroSchalkoFriedrichetal.2021, author = {Valero, Daniel and Schalko, Isabella and Friedrich, Heide and Abad, Jorge D. and Bung, Daniel B. and Donchyts, Gennadii and Felder, Stefan and Ferreira, Rui M. L. and Hohermuth, Benjamin and Kramer, Matthias and Li, Danxun and Mendes, Luis and Moreno-Rodenas, Antonio and Nones, Michael and Paron, Paolo and Ruiz-Villanueva, Virginia and Wang, Ruo-Qian and Franca, Mario J.}, title = {Pathways towards democratization of hydro-environment observations and data}, series = {Iahr White Paper Series}, journal = {Iahr White Paper Series}, number = {1}, publisher = {International Association for Hydro-Environment Engineering and Research (IAHR)}, pages = {1 -- 9}, year = {2021}, language = {en} } @inproceedings{BungSchlenkhoff2008, author = {Bung, Daniel B. and Schlenkhoff, Andreas}, title = {Optimization of the reaeration potential on embankment stepped spillways in skimming flow regime}, series = {Hydraulic structures : proceedings of the second International Junior Researcher and Engineer Workshop on Hydraulic Structures, Pisa, Italy, 30 July-1 August 2008}, booktitle = {Hydraulic structures : proceedings of the second International Junior Researcher and Engineer Workshop on Hydraulic Structures, Pisa, Italy, 30 July-1 August 2008}, editor = {Pagliara, Stefano}, organization = {International Junior Researcher and Engineer Workshop on Hydraulic Structures <2, 2008, Pisa>}, isbn = {978-88-8492-568-8}, pages = {97 -- 106}, year = {2008}, language = {en} }