Publications related to Knudsen number

Scaling behavior of bedload transport: what if Bagnold was right?

There is a paradox in the relationship between bedload transport rates and flow variables: laboratory and field studies have reported on how bedload transport rates depend on flow variables through a power law, but none of the empirical laws fitted to the ...

2023

Growth, timing, & trajectory of vortices behind a rotating plate

Diego Francescangeli

The presence of aerodynamic vortices is widespread in nature. They can be found at small scales near the wing tip of flying insects or at bigger scale in the form of hurricanes, cyclones or even galaxies. They are identified as coherent regions of high vor ...

EPFL2022

Homogenization-based design of microstructured membranes: wake flows past permeable shells

François Gallaire, Edouard Boujo, Pier Giuseppe Ledda, Giuseppe Antonio Zampogna

A formal framework to characterize and control/optimize the flow past permeable membranes by means of a homogenization approach is proposed and applied to the wake flow past a permeable cylindrical shell. From a macroscopic viewpoint, a Navier-like effecti ...

Cambridge University Press2021

Fluid flow through replicated microcellular materials in the Darcy-Forchheimer regime

Andreas Mortensen, Ludger Weber, David Ingram, Alexandros Athanasiou-Ioannou, Sandra Guardia

We extend here a “bottleneck” flow model derived earlier for incompressible fluids flowing under creeping flow conditions [Despois, J. and Mortensen, A: Acta Materialia 53 (2005) 1381] to flow regimes where inertial losses are no longer negligible, causing ...

Elsevier2017

Basal entrainment by Newtonian gravity-driven flows

Christophe Ancey, Nicolas Andreini, Belinda Margaret Bates

Gravity-driven flows can erode the bed along which they descend and increase their mass by a factor of 10 or more. This process is called "basal entrainment." Although documented by field observations and laboratory experiments, it remains poorly understoo ...

Amer Inst Physics2016

High resolution infrared measurements of single-phase flow of R245fa and R236fa within a compact plate heat exchanger, Part 1: Experimental setup and pressure drop results

John Richard Thome, Raffaele Luca Amalfi

This two-part paper presents experimental work to characterize thermal and hydraulic performances of a compact plate heat exchanger. Upward single-phase heat transfer and pressure drop of low pressure, liquid refrigerants R245fa and R236fa was investigated ...

Pergamon-Elsevier Science Ltd2016

High resolution infrared measurements of single-phase flow of R245fa and R236fa within a compact plate heat exchanger, Part 2: Heat transfer results

John Richard Thome, Raffaele Luca Amalfi

In the second article of the present two-part paper, upward single-phase heat transfer within a compact plate heat exchanger was investigated experimentally. The experimental setup, the data reduction technique and pressure drop results were presented in P ...

Pergamon-Elsevier Science Ltd2016

Impact of rotating and fixed nozzles on vortex breakdown in compressible swirling jet flows

François Gallaire, Leonhard Kleiser

Vortex breakdown of swirling, round jet flows is investigated in the compressible, subsonic regime by means of Direct Numerical Simulation (DNS). This is achieved by solving the compressible Navier-Stokes equations on a cylindrical grid using high-order sp ...

Elsevier2016

Two-Phase Heat Transfer Mechanisms within Plate Heat Exchangers : Experiments, Modeling and Simulations

Raffaele Luca Amalfi

Plate heat exchangers are adopted in many domestic and industrial applications, such as ventilation, air conditioning, evaporation or condensation process, heat pumps and cooling of hydrodynamic circuits in engines. In the present thesis, an extensive expe ...

EPFL2016

Squirming through shear-thinning fluids

Lailai Zhu

Many micro-organisms find themselves immersed in fluids displaying non-Newtonian rheological properties such as viscoelasticity and shear-thinning viscosity. The effects of viscoelasticity on swimming at low Reynolds numbers have already received considera ...

Cambridge University Press2015

A Comparative Study of the Local Heat Transfer Distributions Around Various Surface Mounted Obstacles

Peter Ott, Alexandros Terzis, Robert Wyssmann, Dirk Ullmer

In many engineering applications, heat transfer enhancement techniques are of vital importance in order to ensure reliable thermal designs of convective heat transfer applications. This study examines experimentally the heat transfer characteristics on the ...

Science Press2014

An assessment of ion temperature measurements in the boundary of the Alcator C-Mod tokamak and implications for ion fluid heat flux limiters

Christian Gabriel Theiler

The ion temperature is not frequently measured in the boundary of magnetic fusion devices. Comparisons among different ion temperature techniques and simulations are even rarer. Here we present a comparison of ion temperature measurements in the boundary o ...

2013

A flow sensing model for mesenchymal stromal cells using morphogen dynamics

Dominique Pioletti, Alexandre Terrier, Miguel Gortchacow

The differentiation of mesenchymal stromal cells has been shown to be af- fected by many parameters such as morphogens, flow rate, medium viscosity, and shear stress when exposed to fluid flow. The mechanism by which these cells sense their environment is ...

Elsevier2013

Porous media pressure distribution in centrifugal fields

David Andrew Barry

The simplest use of centrifuges to measure soil properties relies on steady state conditions. Analytical solutions, especially if they are simple, make interpretation of data more direct and transparent. Previous approximations are simplified and have a gr ...

American Geophysical Union2013

Dam Break of Newtonian Fluids and Granular Suspensions : Internal Dynamics Measurements

Nicolas Andreini

The objective of this thesis was to increase our understanding of two-phase geophysical flows (e.g. debris flows) by providing velocity profiles in idealized laboratory avalanches. To that end, we developed a new experimental platform made up of an incline ...

EPFL2012

Turbulent vortex shedding from a blunt trailing edge hydrofoil

Philippe Ausoni

Placed in a fluid stream, solid bodies can exhibit a separated flow that extends to their wake. The detachment of the boundary layer on both upper and lower surfaces forms two shear layers which generate above a critical value of Reynolds number a periodic ...

EPFL2009

Transitional cylindrical swirling flow in presence of a flat free surface

Roland Bouffanais, David Lo Jacono

This article is devoted to the study of an incompressible viscous flow of a fluid partly enclosed in a cylindrical container with an open top Surface and driven by the constant rotation of the bottom wall. Such type of flows belongs to a group of recircula ...

2009

An experimental study of coherent structures, secondary currents and surface boils and their interrelation in open-channel flow

Ismail Albayrak

River and open-channel flows are free surface boundary layer flows with complex 3D, large-scale, turbulent structures. The study of 2D and 3D large-scale turbulent flow structures is a great challenge for physicists, mathematicians and engineers from such ...

EPFL2008

Kármán vortex shedding in the wake of a 2D hydrofoil: Measurement and numerical simulation

François Avellan, Mohamed Farhat, Philippe Ausoni, Youcef Ait Bouziad

The present study deals with the shedding process of the Kármán vortices at the trailing edge of a 2D hydrofoil at high Reynolds numbers. Investigations are performed in order to evaluate the ability of an unsteady numerical simulation to accurately reprod ...

2006