scispace - formally typeset
Search or ask a question
Author

Willi H. Hager

Bio: Willi H. Hager is an academic researcher from ETH Zurich. The author has contributed to research in topics: Froude number & Open-channel flow. The author has an hindex of 47, co-authored 379 publications receiving 8361 citations. Previous affiliations of Willi H. Hager include École Polytechnique Fédérale de Lausanne & Imperial College London.


Papers
More filters
Book ChapterDOI
01 Jan 2019
TL;DR: In this article, sediment is either loaded as bed-load with particles sliding, saltating, and rolling over the river bed, or as a suspended-load, where particles move with the turbulent water flow away from the bed.
Abstract: Transportation of sediment is an important and frequent phenomenon in rivers. Sediment is mobilized as bed-load with particles sliding, saltating, and rolling over the river bed, or as a suspended-load, where particles move with the turbulent water flow away from the bed.

13,877 citations

Journal ArticleDOI
TL;DR: In this article, a large variety of scour elements were considered, ranging from 1 to 60% of the channel width, and flow depths ranging from about 40% of channel width.
Abstract: Scour related to bridge hydraulics received much attention in the past decade, including its relation to flood hydrology and hydraulic processes in addition to steady flow. This paper presents new research on bridge pier and abutment scour based on a large data set collected at ETH Zurich, Switzerland. In total six different sediments were tested, of which three were uniform. Also a large variety of scour elements were considered, from 1 to 60% of the channel width, and flow depths ranging from 1 to about 40% of the channel width. Using similarity arguments and the analogy to flow resistance, an equation for temporal scour evolution is proposed and verified with the available literature data. The agreement of the present scour equation with both the VAW data and the literature data were considered sufficient in terms of river engineering accuracy, provided limitations relating to hydraulic, granulometric, and geometrical parameters are satisfied. These limitations are discussed and refer particularly to e...

385 citations

Journal ArticleDOI
TL;DR: In this article, landslide generated impulse waves were investigated in a two-dimensional physical laboratory model based on the generalized Froude similarity, and four wave types were determined: weakly nonlinear oscillatory wave, nonlinear transition wave, solitary-like wave and dissipative transient bore.
Abstract: Landslide generated impulse waves were investigated in a two-dimensional physical laboratory model based on the generalized Froude similarity. The recorded wave profiles were extremely unsteady and nonlinear. Four wave types were determined: weakly nonlinear oscillatory wave, non-linear transition wave, solitary-like wave and dissipative transient bore. Most of the generated impulse waves were located in the intermediate water depth wave regime. Nevertheless the propagation velocity of the leading wave crest closely followed the theoretical approximations for a solitary wave. Between 4 and 50% of the kinetic slide impact energy propagated outward in the impulse wave train. The applicability ranges of the classical nonlinear wave theories to landslide generated impulse waves were determined. The main wave characteristics were related to the landslide parameters driving the entire wave generation process. The slide Froude number was identified as the dominant parameter. The physical model results were compared to the giant rockslide generated impulse wave which struck the shores of the Lituya Bay, Alaska, in 1958.

298 citations

Journal ArticleDOI
Guido Lauber1, Willi H. Hager1
TL;DR: In this paper, the conditions required for Froude similarity were derived based on a literature review, and the positive and negative conditions were derived for a smooth rectangular and horizontal channel.
Abstract: Dambreak waves in a smooth rectangular and horizontal channel are described. Based on a literature review, the conditions required for Froude similarity are first derived. Then, the positive and ne...

273 citations

Book
29 Feb 1992
TL;DR: In this paper, a classical hydraulic jump in non-rectangular channel is described, followed by a submerged hydraulic jump using a bucket-type energy dissipator and a baffle rock.
Abstract: Part 1: Hydraulic Jump 1 Introduction 2 Classical Hydraulic Jump 3 Sloping Jump 4 Hydraulic Jump in Non-Rectangular Channel 5 Submerged Hydraulic Jump References Part 1 Notation Part 1 Part 2: Stilling Basins 6 Introduction 7 Steps and Sills 8 Baffle Rock 9 Effect of Roughness and Discharge 10 Expanding Channel 11 Bucket-type Energy Dissipator 12 Various Aspects of Stilling Basins 13 Types of Stilling Basins 14 Experiences with Stilling Basins References Part 2 Notation Part 2 Subject Index Author Index

269 citations


Cited by
More filters
Book ChapterDOI
01 Jan 2019
TL;DR: In this article, sediment is either loaded as bed-load with particles sliding, saltating, and rolling over the river bed, or as a suspended-load, where particles move with the turbulent water flow away from the bed.
Abstract: Transportation of sediment is an important and frequent phenomenon in rivers. Sediment is mobilized as bed-load with particles sliding, saltating, and rolling over the river bed, or as a suspended-load, where particles move with the turbulent water flow away from the bed.

13,877 citations

Book ChapterDOI
01 Jan 1997
TL;DR: The boundary layer equations for plane, incompressible, and steady flow are described in this paper, where the boundary layer equation for plane incompressibility is defined in terms of boundary layers.
Abstract: The boundary layer equations for plane, incompressible, and steady flow are $$\matrix{ {u{{\partial u} \over {\partial x}} + v{{\partial u} \over {\partial y}} = - {1 \over \varrho }{{\partial p} \over {\partial x}} + v{{{\partial ^2}u} \over {\partial {y^2}}},} \cr {0 = {{\partial p} \over {\partial y}},} \cr {{{\partial u} \over {\partial x}} + {{\partial v} \over {\partial y}} = 0.} \cr }$$

2,598 citations

Book
01 Dec 1988
TL;DR: In this paper, the basic processes in Atomization are discussed, and the drop size distributions of sprays are discussed.Preface 1.General Considerations 2.Basic Processes of Atomization 3.Drop Size Distributions of Sprays 4.Atomizers 5.Flow in Atomizers 6.AtOMizer Performance 7.External Spray Charcteristics 8.Drop Evaporation 9.Drop Sizing Methods Index
Abstract: Preface 1.General Considerations 2.Basic Processes in Atomization 3.Drop Size Distributions of Sprays 4.Atomizers 5.Flow in Atomizers 6.Atomizer Performance 7.External Spray Charcteristics 8.Drop Evaporation 9.Drop Sizing Methods Index

1,214 citations

01 Jan 1992
TL;DR: In this article, cross-correlation methods of interrogation of successive single-exposure frames can be used to measure the separation of pairs of particle images between successive frames, which can be optimized in terms of spatial resolution, detection rate, accuracy and reliability.
Abstract: To improve the performance of particle image velocimetry in measuring instantaneous velocity fields, direct cross-correlation of image fields can be used in place of auto-correlation methods of interrogation of double- or multiple-exposure recordings. With improved speed of photographic recording and increased resolution of video array detectors, cross-correlation methods of interrogation of successive single-exposure frames can be used to measure the separation of pairs of particle images between successive frames. By knowing the extent of image shifting used in a multiple-exposure and by a priori knowledge of the mean flow-field, the cross-correlation of different sized interrogation spots with known separation can be optimized in terms of spatial resolution, detection rate, accuracy and reliability.

1,101 citations

22 Oct 2007
TL;DR: The fifth edition of "Numerical Methods for Engineers" continues its tradition of excellence and expanded breadth of engineering disciplines covered is especially evident in the problems, which now cover such areas as biotechnology and biomedical engineering.
Abstract: The fifth edition of "Numerical Methods for Engineers" continues its tradition of excellence. Instructors love this text because it is a comprehensive text that is easy to teach from. Students love it because it is written for them--with great pedagogy and clear explanations and examples throughout. The text features a broad array of applications, including all engineering disciplines. The revision retains the successful pedagogy of the prior editions. Chapra and Canale's unique approach opens each part of the text with sections called Motivation, Mathematical Background, and Orientation, preparing the student for what is to come in a motivating and engaging manner. Each part closes with an Epilogue containing sections called Trade-Offs, Important Relationships and Formulas, and Advanced Methods and Additional References. Much more than a summary, the Epilogue deepens understanding of what has been learned and provides a peek into more advanced methods. Approximately 80% of the end-of-chapter problems are revised or new to this edition. The expanded breadth of engineering disciplines covered is especially evident in the problems, which now cover such areas as biotechnology and biomedical engineering. Users will find use of software packages, specifically MATLAB and Excel with VBA. This includes material on developing MATLAB m-files and VBA macros.

578 citations