TY  - JOUR
A1  - Valero, Daniel
A1  - Chanson, Hubert
A1  - Bung, Daniel B.
T1  - Robust estimators for turbulence properties assessment
Y1  - 2019
SP  - 1
EP  - 24
ER  - 
TY  - JOUR
A1  - Valero, Daniel
A1  - Chanson, Hubert
A1  - Bung, Daniel B.
T1  - Robust estimators for free surface turbulence characterization: A stepped spillway application
JF  - Flow Measurement and Instrumentation
N2  - 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.
Y1  - 2020
U6  - http://dx.doi.org/10.1016/j.flowmeasinst.2020.101809
SN  - 0955-5986
VL  - 76
IS  - Art. 101809
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Valero, Daniel
A1  - Bung, Daniel B.
T1  - Reformulating self-aeration in hydraulic structures: Turbulent growth of free surface perturbations leading to air entrainment
JF  - International Journal of Multiphase Flow
N2  - 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.
Y1  - 2018
U6  - http://dx.doi.org/10.1016/j.ijmultiphaseflow.2017.12.011
SN  - 0301-9322
VL  - 100
SP  - 127
EP  - 142
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Bung, Daniel B.
A1  - Valero, Daniel
T1  - Re-aeration on stepped spillways with special consideration of entrained and entrapped air
JF  - Geosciences
N2  - 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.
Y1  - 2018
SN  - 2076-3263
VL  - 8
IS  - 9
SP  - Article number 333
PB  - MDPI
CY  - Basel
ER  - 
TY  - CHAP
A1  - Bung, Daniel B.
A1  - Pagliara, S.
T1  - Proceedings of the International Workshop on Hydraulic Design of Low-Head Structures : Aachen, Germany, February, 20-22, 2013 /  D. Bung ; S. Pagliara (eds.)
Y1  - 2013
SN  - 978-3-939230-04-5
PB  - Bundesanst. für Wasserbau
CY  - Karlsruhe
ER  - 
TY  - CHAP
A1  - Schlenkhoff, Andreas
A1  - Bung, Daniel B.
T1  - Prediction of oxygen transfer in self-aerated skimming flow on embankment stepped spillways
T2  - Water engineering for sustainable environment : 33rd IAHR congress ; 9 - 14 August 2009, Vancouver, British Columbia, Canada
Y1  - 2009
SN  - 9789078046080
SP  - 1 CD-ROM
ER  - 
TY  - CHAP
A1  - Kerpen, N. B.
A1  - Bung, Daniel B.
A1  - Schlurmann, Torsten
ED  - Janssen, Robert
T1  - Physical model investigations of ships passing through a lock
T2  - 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
Y1  - 2010
SN  - 9781742720159
SP  - 93
EP  - 100
PB  - School of Civil Engineeering, The University of Queensland
CY  - Brisbane
ER  - 
TY  - CHAP
A1  - Kerpen, N. B.
A1  - Bung, Daniel B.
A1  - Schlurmann, Torsten
T1  - Physical model investigations of pressure distributions next to ships passing through a lock
T2  - 5th Chinese-German Joint Symposium on Hydraulic and Ocean Engineering : CG JOINT 2010
Y1  - 2010
SN  - 978-7-5618-3671-2
SP  - 514
EP  - 519
PB  - Univ. Press
CY  - Tianjin
ER  - 
TY  - JOUR
A1  - Valero, Daniel
A1  - Schalko, Isabella
A1  - Friedrich, Heide
A1  - Abad, Jorge D.
A1  - Bung, Daniel B.
A1  - Donchyts, Gennadii
A1  - Felder, Stefan
A1  - Ferreira, Rui M. L.
A1  - Hohermuth, Benjamin
A1  - Kramer, Matthias
A1  - Li, Danxun
A1  - Mendes, Luis
A1  - Moreno-Rodenas, Antonio
A1  - Nones, Michael
A1  - Paron, Paolo
A1  - Ruiz-Villanueva, Virginia
A1  - Wang, Ruo-Qian
A1  - Franca, Mario J.
T1  - Pathways towards democratization of hydro-environment observations and data
JF  - Iahr White Paper Series
Y1  - 2021
IS  - 1
SP  - 1
EP  - 9
PB  - International Association for Hydro-Environment Engineering and Research (IAHR)
ER  - 
TY  - CHAP
A1  - Bung, Daniel B.
A1  - Schlenkhoff, Andreas
ED  - Pagliara, Stefano
T1  - Optimization of the reaeration potential on embankment stepped spillways in skimming flow regime
T2  - Hydraulic structures : proceedings of the second International Junior Researcher and Engineer Workshop on Hydraulic Structures, Pisa, Italy, 30 July-1 August 2008
Y1  - 2008
SN  - 978-88-8492-568-8
SP  - 97
EP  - 106
ER  - 
TY  - CHAP
A1  - Bung, Daniel B.
ED  - Theobald, S.
T1  - Optimierung des potentiellen Sauerstoffeintrags auf Treppenschussrinnen mit gemäßigter Neigung
T2  - 9. JuWi-Treffen : Beiträge zum Treffen junger Wissenschaftlerinnen und junger Wissenschaftler deutschsprachiger Wasserbauinstitute
Y1  - 2009
SP  - 73
EP  - 78
PB  - Universität Kassel
CY  - Kassel
ER  - 
TY  - JOUR
A1  - Bung, Daniel B.
A1  - Valero, Daniel
T1  - Optical flow estimation in aerated flows
JF  - Journal of Hydraulic Research
N2  - 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.
Y1  - 2016
U6  - http://dx.doi.org/10.1080/00221686.2016.1173600
VL  - 54
IS  - 5
SP  - 575
EP  - 580
PB  - Taylor & Francis
CY  - London
ER  - 
TY  - JOUR
A1  - Zhang, G.
A1  - Valero, Daniel
A1  - Bung, Daniel B.
A1  - Chanson, H.
T1  - On the estimation of free-surface turbulence using ultrasonic sensors
JF  - Flow Measurement and Instrumentation
N2  - Accurate determination of free-surface dynamics has attracted much research attention during the past decade and has important applications in many environmental and water related areas. In this study, the free-surface dynamics in several turbulent flows commonly found in nature were investigated using a synchronised setup consisting of an ultrasonic sensor and a high-speed video camera. Basic sensor capabilities were examined in dry conditions to allow for a better characterisation of the present sensor model. The ultrasonic sensor was found to adequately reproduce free-surface dynamics up to the second order, especially in two-dimensional scenarios with the most energetic modes in the low frequency range. The sensor frequency response was satisfactory in the sub-20 Hz band, and its signal quality may be further improved by low-pass filtering prior to digitisation. The application of the USS to characterise entrapped air in high-velocity flows is also discussed.
Y1  - 2018
U6  - http://dx.doi.org/10.1016/j.flowmeasinst.2018.02.009
SN  - 0955-5986
VL  - 60
SP  - 171
EP  - 184
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - CHAP
A1  - Bung, Daniel B.
T1  - Observations on non-aerated flow and air entrainment on moderately sloped stepped spillways
T2  - 7th Chinese-German Joint Symposium on Hydraulic and Ocean Engineering : 8. - 12. Sept. 2014, Hannover
Y1  - 2014
N1  - Kennwortgeschützter Zugang. Passwort bei Prof. Bung, Fachbereich Bauingenieurwesen
SP  - 1
EP  - 8
ER  - 
TY  - JOUR
A1  - Oertel, Mario
A1  - Bung, Daniel B.
T1  - Numerische Strömungssimulationen von Fließgewässern : Praxisanwendungen und zukünftige Entwicklungen
JF  - Korrespondenz Wasserwirtschaft : KW
Y1  - 2015
SN  - 1616-430X
VL  - 8
IS  - H. 3
SP  - 177
EP  - 182
PB  - Gesellschaft zur Förderung der Abwassertechnik
CY  - Hennef
ER  - 
TY  - CHAP
A1  - Oertel, Mario
A1  - Bung, Daniel B.
T1  - Numerische Strömungssimulation von Fließgewässern - Wo stehen wir und was werden wir im Laufe der nächsten Jahre erreichen?
T2  - Simulationsverfahren und Modelle für Wasserbau und Wasserwirtschaft = Simulation techniques and models for hydraulic engineering and water management / 37. Dresdner Wasserbaukolloquium 2014, 13. - 14. März 2014. (Dresdner wasserbauliche Mitteilungen ; H. 50)
Y1  - 2014
SN  - 978-3-86780-349-6
SP  - 19
EP  - 30
ER  - 
TY  - CHAP
A1  - Valero, Daniel
A1  - Bung, Daniel B.
A1  - Erpicum, Sebastien
A1  - Dewals, Benjamin
T1  - Numerical study of turbulent oscillations around a cylinder: RANS capabilities and sensitivity analysis
T2  - Proceedings of the 37th IAHR World Congress August 13 – 18, 2017, Kuala Lumpur, Malaysia
Y1  - 2017
SN  - 2521-716X
SP  - 3126
EP  - 3135
ER  - 
TY  - CHAP
A1  - Oertel, Mario
A1  - Balmes, Jan P.
A1  - Bung, Daniel B.
T1  - Numerical simulation of erosion processes on crossbar block ramps
T2  - E-proceedings of the 36th IAHR World Congress 28 June – 3 July, 2015, The Hague, the Netherlands
Y1  - 2015
SP  - 1
EP  - 8
ER  - 
TY  - CHAP
A1  - Valero, Daniel
A1  - Bung, Daniel B.
A1  - Crookston, B. M.
A1  - Matos, J.
ED  - Crookston, B.
ED  - Tullis, B.
T1  - Numerical investigation of USBR type III stilling basin performance downstream of smooth and stepped spillways
BT  - Session 1: Hydraulic structures
T2  - Hydraulic Structures and Water System Management. 6th IAHR International Symposium on Hydraulic Structures, Portland, OR, 27-30 June 2016
Y1  - 2016
SN  - 978-1-884575-75-4
U6  - http://dx.doi.org/10.15142/T340628160853
SP  - 635
EP  - 646
ER  - 
TY  - CHAP
A1  - Bung, Daniel B.
T1  - Non-intrusive measuring of air-water flow properties in self-aerated stepped spillway flow
T2  - Balance and uncertainty - water in a changing world :  proceedings of the 34th IAHR world congress ; 33rd Hydrology and Water Resources Symposium ; 10th Conference on Hydraulics in Water Engineering ; 26 June - 1 July 2011, Brisbane, Australia
Y1  - 2011
SN  - 978-0-85825-868-6
SP  - 2380
EP  - 2387
ER  -