Search results for "viskositeetti"

Online measurement of floc size, viscosity, and consistency of cellulose microfibril suspensions with optical coherence tomography

2021

AbstractIn this study, cellulose microfibril (CMF) suspensions were imaged during pipe flow at consistencies of 0.4%, 1.0%, and 1.6% with optical coherence tomography (OCT) to obtain images of the structure and the local velocity of the suspension. The viscosities obtained by combining pressure loss measurement with the OCT velocity data showed typical shear thinning behavior and were in excellent agreement with viscosities obtained with ultrasound velocity profiling. The structural OCT images were used to calculate the radial and the axial floc sizes of the suspension. A fit of power law to the geometrical floc size–shear stress data gave the same power law index for all consistencies, sug…

Theory overview of Heavy Ion collisions

2016

This presentation discusses some recently active topics in the theoretical interpretation of high energy heavy ion collisions at the LHC and at RHIC. We argue that the standard paradigm for understanding the spacetime evolution of the bulk of the matter produced in the collision is provided by viscous relativistic hydrodynamics, which can be used to systematically extract properties of the QCD medium from experimental results. The initial conditions of this hydrodynamical evolution are increasingly well understood in terms of gluon saturation, and can be quantified using Classical Yang-Mills fields and QCD effective kinetic theory. Hard and electromagnetic probes of the plasma provide addit…

Rheological and Flocculation Analysis of Microfibrillated Cellulose Suspension Using Optical Coherence Tomography

2018

A sub-micron resolution optical coherence tomography device was used together with a pipe rheometer to analyze the rheology and flocculation dynamics of a 0.5% microfibrillated cellulose (MFC) suspension. The bulk behavior of the MFC suspension showed typical shear thinning (power-law) behavior. This was reflected in a monotonously decreasing floc size when the shear stress exceeded the yield stress of the suspension. The quantitative viscous behavior of the MFC suspension changed abruptly at the wall shear stress of 10 Pa, which was reflected in a simultaneous abrupt drop of the floc size. The flocs were strongly elongated with low shear stresses. With the highest shear stresses, the flocs…

Measuring the non-linear hydrodynamic response of higher flow harmonics in Pb-Pb at sqrt(s_NN)=2.76 TeV

2017

Ultrarelativistisissa raskasionitörmäyksissä syntyvän kvarkki-gluoniplasman (QGP) dynamiikkaa on relativistisella hydrodynamiikalla kuvattu erittäin vakuuttavasti. Teorian vapaa parametri, keskimääräinen viskositeetti-entropiasuhde, on kuitenkin vielä tarkasti määrittämättä. Alustamalla törmäyksen alkutila teoreettisesti sekä soveltamalla relativistista hydrodynamiikkaa QGP:n evoluution mallintamiseen, saadaan viskositeettia tarkastelemalla käsitys QGP:n rakennesosien välisten vuorovaikutusten vahvuuksista, minkä lisäksi voidaan ymmärtää plasman evoluutioon vaikuttavia tekijöitä. Tavanomaisesti QGP:n viskositeetti määritetään vertailemalla teoreettisen alkutilan eksentrisyyden lineaarista s…

Puukuitususpension putkistovirtaus, viskositeetti ja häviökorrelaatiomalli

2010

We measured pressure loss and velocity profile from pine and birch suspension flow in two straight PVC-tubes. The suspension consistencies were 0,5 %–4,0 % and tubes' radius were 105,2 mm and 191,6 mm. The velocity profiles were measured with pulsed ultrasonic Doppler velocimetry technique. Unusual laminar shaped profiles were discovered at low flow rates of birch suspension. With these profiles it was possible to calculate the actual viscosity for fiber suspension. In the analysis we discovered that the viscosity didn't depend on the flow velocity or geometry. It was possible to write a material law that describes the viscosity as a function of shear rate with two material related paramete…

C1,α regularity for the normalized p-Poisson problem

2017

We consider the normalized p -Poisson problem − Δ N p u = f in Ω ⊂ R n . The normalized p -Laplacian Δ N p u := | Du | 2 − p Δ p u is in non-divergence form and arises for example from stochastic games. We prove C 1 ,α loc regularity with nearly optimal α for viscosity solutions of this problem. In the case f ∈ L ∞ ∩ C and p> 1 we use methods both from viscosity and weak theory, whereas in the case f ∈ L q ∩ C , q> max( n, p 2 , 2), and p> 2 we rely on the tools of nonlinear potential theory peerReviewed

Discrete element model for viscoelastic materials with brittle fracture : applications on glacier dynamics

2017

The stress-strain state and stabilization of viscoelastoplastic, imperfect moving web continuum

2014

On modelling and stability of axially moving viscoelastic materials

2013

Viskositeetin mittaaminen pietsosähköherätteisellä värähtelijällä

2010

Tässä pro gradu -tutkielmassa käsitellään nesteen viskositeetin ominaisuuksia ja erityisesti pietsosähköherätteisiin komponentteihin perustuvia tapoja mitata nesteen viskositeettia sähköisesti. Motivaationa tutkielman tekoon oli löytää menetelmä, jolla voidaan mitata nesteiden viskositeettia luotettavasti. Nesteiden viskositeetti aiheuttaa värähtelijöihin sähköisen vastuksen, jolloin taajuuden, impedanssin ja vaihekulman resonanssiarvoja tarkastelemalla voidaan viskositeettia mitata. Teoriaosuudessa keskityttiin viskositeetin ominaisuuksien lisäksi suorakaiteen muotoisen palkin, CMBP, värähtelydynamiikkaan värähtelevä pallo -mallin ja simulaatiotulosten avulla. Kokeellisessa osiossa tutkitt…