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Dynamic Optical Rheo Analyzer (DORA)

Dynamic Optical Rheo Analyzer (DORA). DORA Background. D ynamic O ptical R heo A nalyzer (DORA) Gives structural information simultaneously with the rheological measurements Optical Methods used with DORA: Birefringence and Dichroism Optical Anisotropy:

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Dynamic Optical Rheo Analyzer (DORA)

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  1. Dynamic Optical Rheo Analyzer (DORA)

  2. DORABackground DynamicOpticalRheoAnalyzer(DORA) Gives structural information simultaneously with the rheological measurements Optical Methods used with DORA: Birefringence and Dichroism Optical Anisotropy: Orientation and deformation of the microstructure cause anisotropy in the refractive index, i.e. it is a tensor. Makes use of polarization of light.

  3. DORABackground Light Source L Polarization state generator PSG Sample S Polarization state analyzer PSA Detector D Calculation with Stokes Vector and Mueller Matrices: SD = MPSA MSample  MPSG  S0 S0 : Stokes Vector of the incoming light MPSG: Müller Matrix of the polarizer MSample: Müller Matrix of the sample MPSA: Müller Matrix of the analyzer SD : Stokes Vector of the light falling on the detector

  4. DORA – ApplicationsLiquid Crystal Although the Dichroism decreases the orientation angle increases due to the alingment of the crystals in flow direction

  5. DORA – ApplicationsShear Banding of a Micellar Solution Increase in Birefringence at point where stress curve flattens, i.e. onset of shear banding

  6. Particle Image Velocimetry (PIV)

  7. Particle Image Velocimetry (PIV)C-LTD70/PIV

  8. Rheo – PIVParticle Imaging Velocimetry • Particle Imaging Velocity (PIV) • A high power laser and optical arrangement produce a light sheet. • The particles in the fluid scatter the light. • The scattered light that is detected by the camera. • In order to measure the velocity, at least two exposures are needed. • Calculation of displacement vectors • The flow field through the whole gap in a concentric cylinder geometry can be measured.

  9. Rheo – PIVExample: Shear Banding of Micellar Solutions

  10. Flow Curve of Gold Particles suspended in Acetone Reynolds Number Re > 1000 = 165 s-1 Onset of Taylor Vorticities Ta > 41.2 = 22 s-1

  11. CTD Eye for UXF and SER • In UXF and SER the sample is not centered at the middle of the CTD • Active sample size is small strip • Special Optics to focus directly on the sample • Observed sample size: 10x12m; Image size: 1/3” (4.7x3.6mm) • Luminera Camera (Lm075) with 1/3” or any other camera with C-mount • CTD is extended in order that the camera sees the middle of the sample

  12. Dielectric Spectroscopy: The measurement • Electrical current flowing through a sample as a response to an alternating electric field is measured as a function of the field frequency • Dielectric spectrum gives information on structure and behavior of the material Voltage Voltage application DC or AC voltage + Dielectric + Induction of an - electric field - LCR meter Current Measurement of the flowing current

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