101-0190-10L  Eddy-resolving Numerical Simulations and Coherent Structures in Hydrodynamics and Env. Hydraulics

SemesterSpring Semester 2021
LecturersS. G. Constantinescu
Periodicitynon-recurring course
Language of instructionEnglish

AbstractThe course requires no background in numerical methods and CFD and it addressed to graduate students and scientists with background in both experimental and numerical research.
ObjectiveThe main purpose of the short course is to present an introduction to coherent structures and their role in explaining the physics of several important categories of flows relevant to hydrodynamics of rivers and environmental hydraulics. The focus is on examples related to hydraulics, river engineering and stratified flows. The relationship between flow instabilities and coherent structures is emphasized.

The use of fully three-dimensional eddy-resolving numerical simulations offers a great instrument for the study of the dynamics of the coherent structures. The course presents an introduction to the main types of eddy-resolving numerical methods (Unsteady RANS, Large Eddy Simulation, Direct Numerical Simulation) and discusses the advantages and disadvantages of these methods, and the numerical requirements related to obtaining accurate solutions. Emphasis is put on hybrid RANS-LES methods and advanced wall models that allow simulating environmental flows at field conditions and study of scale effects.

The main goal of the course is to familiarize the participants with the main ideas and concepts behind eddy resolving methods, their advantages & limitations and to provide examples that show how the results of such simulations can advance our understanding of the relevant processes and mechanisms controlling transport of heat, contaminant and sediment in turbulent flows, turbulent diffusion and dispersion with special emphasis on fluvial processes.
ContentL1. Introduction to turbulence modeling (DNS, LES, RANS)
Introduction to LES modeling (Part 1)

L2. Introduction to LES modeling (Part 2)
Wall models and hybrid RANS-LES methods (DES)

L3. Flow instabilities and coherent structures
In-depth example: open channel flow over 2-D dunes

L4. Flow and sediment erosion mechanisms around surface-mounted solid and porous cylinders (bridge piers, patches of emerged or submerged vegetation).
Shallow wakes past cylinders

L5. Gravity currents: Introduction and main flow regimes
Gravity currents propagating in a porous environment (e.g., vegetated or partially vegetated channel)
Gravity currents propagating over large-scale roughness elements (e.g., dunes)
Gravity currents propagating over an inclined flat surface
Gravity currents propagating over cyclic steps

L6. Shallow mixing interfaces between parallel and non-parallel streams with focus on river confluences and groyne fields, and temperature stratification effects

L7. Dispersion of buoyant and non-buoyant contaminants from bottom river cavities
Flow hydrodynamics and mixing in stratified lakes due to wind forcing

L8. Flow past isolated freshwater mussels and mussel beds
Pump-intake vortices

L9. Class evaluation via a closed book 1.15 hours written exam
Lecture notesPDF files of the material presented in the lectures will be provided
LiteratureRecommended textbook: Rodi, W, Constantinescu, G. and Stoesser, T. (2013) “Large Eddy Simulation in hydraulics” IAHR Monograph, CRC Press, Taylor & Francis Group (ISBN-10: 1138000247) 310 pages