Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Experimental techniques

Different experimental techniques have been used to characterize the flow conditions before and during the instabilities. They are mainly based on the use of transparent tools, i.e. extrusion dies with glass windows. Such tools have been developed in LSP Erlangen, CEMEF and University of Cambridge. They allow one to perform two kinds of measurements: - Flow Induced Birefringence (FIB): a laser or optical light is passed through the flow between polarizer and analyser. The optical anisotropy created by the flow leads to the observation of extinction bands, related to the stress field.

Thus, FIB is able to provide pertinent information on the stress field, both in stationary or time-dependent flows. This technique was particularly powerful for the characterization of spurt conditions and volume distortions. Moreover, it is also a very efficient tool for assessing the parameters of constitutive equations or to check the validity of numerical simulations. - Laser Doppler Velocimetry (LDV): LDV allows one to measure the local velocity in the flow field. Depending on the system, one or two components of the velocity vector can be measured simultaneously. This method was particularly efficient to identify the boundary conditions (slip or no-slip at the wall) and to detect the presence and the size of vortices in abrupt contraction geometries.

As for FIB, results are also very useful for controlling the validity of rheological laws or finite element simulations. Among the other experimental techniques used in 3PI project, we should include the Multipass Rheometer (MPR) developed by Cambridge. This specific rheometer with two pistons allows one to perform successive experiments with a limited amount of material and to characterize flow conditions under controlled pressure.

Verwandte Informationen

Reported by

CEMEF, Ecole des Mines de Paris
Rue Claude DAUNESSE BP 207
Folgen Sie uns auf: RSS Facebook Twitter YouTube Verwaltet vom Amt für Veröffentlichungen der EU Nach oben