Publications associées à Dynamic force coefficients identification on air-lubricated herringbone grooved journal bearing

The effects of kinematics, flexibility, and planform on the vortex formation and aerodynamic performance of flapping wing flight

In this thesis, the aerodynamic challenges in flapping wing flight are addressed. In particular, the effects of different wing kinematics, flexibilities, and planforms on the the leading edge vortex development and aerodynamic performance are investigated. ...

EPFL2023

Triple Crossed Flexure Pivot Based on a Zero Parasitic Center Shift Kinematic Design

Simon Nessim Henein, Etienne Frédéric Gabriel Thalmann

Thanks to their absence of play, absence of contact friction and possible monolithic fabrication, flexure pivots offer advantages over traditional bearings in small-scale, high accuracy applications and environments where lubrication and wear debris are pr ...

2022

Experimental and numerical investigation of the unbalance behavior of rigid rotors supported by spiral-grooved gas journal bearings

Jürg Alexander Schiffmann, Elia Iseli

The forced response of rigid rotors, supported by herringbone-grooved gas journal bearings are investigated numerically and experimentally. The rotor configurations are varied by using end cylinders, attached at both sides of the shaft. Three rotors with d ...

ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD2022

Coupling metric-affine gravity to a Higgs-like scalar field

Sebastian Zell

General relativity (GR) exists in different formulations. They are equivalent in pure gravity but generically lead to distinct predictions once matter is included. After a brief overview of various versions of GR, we focus on metric-affine gravity, which a ...

American Physical Society2022

Extended Windage Loss Models for Gas Bearing Supported Spindles Operated in Dense Gases

Jürg Alexander Schiffmann, Kévin Rosset

Generic models are proposed to evaluate the skin friction coefficient acting on enclosed rotating disks and cylinders under various flow regimes. In particular, a model taking into account the inner radius of the disk is developed. The models are compared ...

2020

Flexure Pivot Oscillators for Mechanical Watches

Etienne Frédéric Gabriel Thalmann

It appears that the concerted efforts of the watchmaking industry are leading towards a limit in mechanical watch accuracy. The general consensus in horology is that the time base's quality factor, a dimensionless number that characterizes the oscillator d ...

EPFL2020

Experimental Study of Sliding Friction Damper for High-Performance Steel Structures

Martina Paronesso, Dimitrios Lignos

Passive energy dissipation devices are widely utilized in buildings to minimize structural and non-structural damage under seismic loading. Commonly used devices include, among others, yield, viscous and friction dampers. While the use of yield dampers, su ...

Earthquake Engineering Association2020

Flexible Support for Gas-Lubricated Bearing Bushings

Jürg Alexander Schiffmann

Herringbone-grooved journal bearings (HGJBs) for high-speed turbo-machinery are often supported on O-rings due to their favorable stiffness and damping characteristics for stability and alignment reasons. They yield limited lifetime at high temperatures, i ...

2020

Inflationary perturbations with Lifshitz scaling

Sergey Sibiryakov

Instead of Lorentz invariance, gravitational degrees of freedom may obey Lifshitz scaling at high energies, as it happens in Horava's proposal for quantum gravity. We study consequences of this proposal for the spectra of primordial perturbations generated ...

IOP PUBLISHING LTD2019

Control of Dissipation Sources: A Central Aspect for Enhancing the Mechanical and Mechanobiological Performances of Hydrogels

Dominique Pioletti, Naser Nasrollahzadeh Mamaghani, Peyman Karami

Development of mechanically durable and biologically inductive hydrogels is a major challenge for load-bearing applications such as engineered cartilage. Dissipative capacity of articular cartilage is central to its functional behavior when submitted to lo ...

2019

Inconsistency of an inflationary sector coupled only to Einstein gravity

Daniel Garcia Figueroa

From a model-building perspective, the inflationary sector might very well have no direct couplings to other species, apart from inevitable gravitational interactions. Within the context of General Relativity, a thermal universe can still emerge after infl ...

IOP PUBLISHING LTD2019

Aeroelastic deformation of a perforated strip

Pedro Miguel Nunes Pereira de Almeida Reis, Mark Andrew Guttag

We perform a combined experimental and numerical investigation into the static deformation of perforated elastic strips under uniform aerodynamic loading at high-Reynolds-number conditions. The static shape of the porous strips, clamped either horizontally ...

2018

Horava Gravity is Asymptotically Free in 2+1 Dimensions

Sergey Sibiryakov, Diego Blas Temino, Mario Herrero Valea

We compute the beta functions of marginal couplings in projectable Horava gravity in 2 + 1 spacetime dimensions. We show that the renormalization group flow has an asymptotically free fixed point in the ultraviolet (UV), establishing the theory as a UV-com ...

American Physical Society2017

Measurement of the dynamics in ski jumping using a wearable inertial sensor-based system

Kamiar Aminian, Julien Favre, Julien Chardonnens

Dynamics is a central aspect of ski jumping, particularly during take-off and stable flight. Currently, measurement systems able to measure ski jumping dynamics (e.g., 3D cameras, force plates) are complex and only available in few research centres worldwi ...

Taylor & Francis2014

MEMS Inertial Sensor to Measure the Gravity Gradient Torque in Orbit

Kaustav Ghose

Since the dawn of the Space Age, over six thousand satellites have been launched into Earth orbit. The function of determining the orientation of a satellite in orbit, so that it can point its antennas and instruments in the required direction is known as ...

EPFL2012

Experimental Contribution to the Mechanics of Herringbone Grooved Journal Air Bearings

Ivan Ognjanovic

Gas Lubricated Herringbone Grooved Journal Bearings (HGJB) have long been used in equipment such as navigation systems, optical scanners for laser printers and high speed cameras and disk spindle for flyhead testers. All such applications are characterized ...

EPFL2011

Consistent Extension of Horava Gravity

Sergey Sibiryakov, Diego Blas Temino

We propose a natural extension of Horava's model for quantum gravity, which is free from the notorious pathologies of the original proposal. The new model endows the scalar graviton mode with a regular quadratic action and remains power-counting renormaliz ...

2010

Comment on "Strong coupling in extended Horava-Lifshitz gravity" [Phys. Lett. B 685 (2010) 197]

Sergey Sibiryakov, Diego Blas Temino

We show that, contrary to the claim made in arXiv:0911.1299, the extended Horava gravity model proposed in arXiv:0909.3525 does not suffer from a strong coupling problem. By studying the observational constraints on the model we determine the bounds on the ...

2010

Fluid-structure coupling for an oscillating hydrofoil

François Avellan, Mohamed Farhat, Philippe Ausoni, Olivier Braun, Cécile Münch-Alligné

Fluid-structure investigations in hydraulic machines using coupled simulations are particularly time-consuming. In this study, an alternative method is presented that linearizes the hydrodynamic load of a rigid, oscillating hydrofoil. The hydrofoil, which ...

Elsevier2010

Open-loop control of compressible afterbody flows using adjoint methods

Philippe Meliga

The flow past an axisymmetric body is generically unstable to a steady and a time-periodic global instability, the latter being thought to lead the low-frequency unsteadiness of the wake even at larger Reynolds numbers. The present paper examines how the g ...

2010