Couette cell

In the Couette cell the shear stress varies signficantly with radial position across the gap as r2. Should a more uniform stress environment be required then the cone-and-plate geometry may be used [17]. An example apparatus is shown in Figure 2.8.7. 

Typically gap angles of between 7° and 4° are used. The cone is rotated in a similar manner to the Couette cell, however, unlike the Couette cell the cone-and-... 

Fig. 2.8.6 (a) (i) I implementation of vertical cylindrical Couette cell using concentric glass tubes (ii) velocity image taken across a horizontal slice and (iii) velocity profile taken across the cell. Note that the marker fluid in the inner cylinder exhibits rigid body motion... 

MHz, from 20% w/w CTAB-D20 (41 °C) at observed, consistent with an ordered phase, different positions across the annular gap of a while near the outer wall the single peak of an cylindrical Couette cell and at an apparent isotropic phase is seen. In between, a mixed shear rate of 20 s 1. Near the inner wall, where phase region exists (adapted from Ref. [38]). 

Fig. 2.8.13 Velocity probability distributions at different positions across the gap in a 5 mm-9 mm Couette cell at a shear of 0.101 s-1 and following long pre-shearing at high shear rate.

Fig. 4.4.9 (a) A new paradigm for MRI veloci- efficient post-processing of MRI data, (b) metry based on prior knowledge. The introduc- Efficient reconstruction of Taylor-Couette cells tion of mathematical constraints imposed by on the longitudinal plane (r, z) starting from... 

Reactors which generate vortex flows (VFs) are common in both planktonic cellular and biofilm reactor applications due to the mixing provided by the VF. The generation of Taylor vortices in Couette cells has been studied by MRM to characterize the dynamics of hydrodynamic instabilities [56], The presence of the coherent flow structures renders the mass transfer coefficient approaches of limited utility, as in the biofilm capillary reactor, due to the inability to incorporate microscale details of the advection field into the mass transfer coefficient model. 

The vortex flow reactor was a glass Couette cell driven by a Bruker RheoNMR system. The cell consisted of a stationary outer glass tube with an id of 9 mm and a rotating inner glass tube with an od of 5 mm, giving a gap of 2 mm. The Couette was filled with cylindrical bacterial cells, F. nucleatum ( 2 x 20 pm), suspended in water at a concentration of =10" cells mL-1. 

Fig. 5.1.11 MR velocity maps of a cross section through the center of a Couette cell with a 2 mm gap. The inner cylinder is rotating, (a) y component of velocity vy corresponding to the tangential direction with flow out of the plane (black) and into the plane (white).

Berret et al. (1996) have investigated the effect of steady shear, applied using a Couette cell, on the orientation of a face-centred cubic structure in PE0i27PP04aPE0127 (Pluronic F108) using SAXS, and transitions between shear-... 

Fig. 4.25 Experimentally measured SANS patterns for an FCC micellar phase in a dPS-PI diblock (A/ = 55kgmor, 60wt% PS) in core contrast-matched decane/ d-decane mixtures (15wt% polymer) subject to steady shear in a Couette cell at different shear rates (McConnell et al. 1995) (a) y — 0.01 s aligned by inserting the stator (b) y=0.06s 1 (c) y = 0.66s 1 (d) y = 6.60s (e) y = 66.0 s (f) y = 200.0s-1. The wavevectors qv (horizontal) and qe (vertical) for these patterns range from —0.028 to 0.028 A. ...

Fig. 4.37 SANS pattern for a 6wt% solution of a PS-P(E/P) diblock (M,. 129kgmoT, 38.5 wt% PS) in deuterated dodecane, following shear at y = 66.0s"1 in a Couette cell (Phoon et al. 1993). The arrow indicates the direction of flow. The wavevector ranges from -0.01 to 0.01 A...

Mabille et al. [26] described a device capable of producing large amounts of emulsions based on the use of a Couette-cell geometry. 

The premixed double emulsion is sheared in the Couette cell at different shear rates from 0 to 14200 s 1. The obtained double emulsions have diameters ranging from 7 pm to 2 pm and uniformity between 15% and 30%. Figure 15 is a mi-... 

An example of such a spectrum is shown in Fig. 13. It was obtained using a Couette cell comprising a 10-mm-o.d. (8.9-mm-i.d.) NMR tube with a concentric 5-mm NMR tube connected to an external shaft driven by a variable speed motor. The space between the cylinders was filled with water containing a small amount (0.5%) of high molar mass polyethylene oxide, which had the effect of increasing the viscosity and thus ensuring laminar flow. 

Fig. 15. Velocity profiles across a diametral slice obtained in the rotating Couette cell for (a) water and (b) a solution of 5% polyethylene oxide in water, at rotation speed ranging from 0.60 to 10 rad s". Note that the left- and right-hand sides of the annulus yield similar profiles but with oppositely signed velocities. [Reproduced by permission from Rofe et a ., 1994.]...

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