Couette apparatus

Figure 15.1 Schematic diagram of the Taylor-Couette apparatus used for studies of turbulent flame propagation...

It is also possible to calculate the flow path in a Couette apparatus for non-Newtonian liquids (flowing between rotating cylinders Fig. 31) (see page 56). If an inner cylinder rotates at an angular velocity co and a shear deformation takes place in the gap between the internal and external cylinder (R — i a) we observe a torque M ... 

The Couette apparatus was developed by Maurice Couette in 1890 as a means for measuring the viscosity of a fluid at small imposed angular velocities of the cylinders. 

Fig. 1, Couette apparatus (A) for continuous growth of polyethylene macrofibres from dilute p-xylene solutions. The macrofibre grows on the surface of the Teflon rotor, leaves the vessel through a Teflon pipe, and is wound up on a take-up roll.

Three different isothermal crystallization experiments were performed in this work classical static (i.e., quiescent) crystallization in the DSC apparatus, dynamic crystallization with the apparatus described above, and dynamic-static crystallization. Dynamic isothermal crystallization consisted in completely solidifying cocoa butter under a shear in the Couette apparatus. Comparison of shear effect with results from literature was done using the average shear rate y. This experiment did not allow direct measurement of the solid content in the sample. However, characteristic times of crystallization were estimated. The corresponded visually to the cloud point and to an increase of the cocoa butter temperature 1 t) due to latent heat release. The finish time, was evaluated from the temperature evolution in cocoa butter. At tp the temperature Tit) suddenly increases sharply because of the apparition of a coherent crystalline structure in cocoa butter. This induces a loss of contact with the outer wall and a sharp decrease in the heat extraction. 

In a Couette apparatus, i.e., between two concentric cylinders, of which the outer one of radius 10 cm is rotating at 180 revolutions per minute and the inner stationary one has a radius of 9.5 cm some triglyceride oil is present. The temperature is 20°C. How long will it take before the temperature is raised to 21 °C, assuming that no heat loss from the oil to the environment occurs Tip Some useful data are in Table 9.2. 

FIGURE 3.66 Stress-strain curves for polyethylene fibers grown from solution in Couette apparatus at... 

For definiteness let us assume that the experiment is carried out in a cylindrical CouETTE apparatus. This may be represented by Fig. 10 a, Fig. 10 a. Cylindrical Fig. 10 b. Ellipsoidof polarisability where the outer cylinder is CouETTE apparatus. in the streaming liquid. assumed to rotate with respect... 

Karam and Bellinger [81] and later Grace [89] developed correlations for the shear rate of droplets at burst (y, ) using a Couette apparatus. They expressed their formulation using Taylor s Eq. (6.29a), thus including interfacial tension, viscosity ratio, and drop size. This is presented in the form of a correlation of ... 

A continuous highly oriented fiber may be grown from dilute polyethylene solution subjected to shear flow in a Couette apparatus [70,74]. This device consists of a pair of coaxial cylinders, the inner one of which can be rotated rapidly. A dilute polyethylene solution introduced into the gap between the cylinders is subjected to shear flow. When the appropriate conditions of shear, temperature, and concentration are met, the polymer will crystallize on to a seed fiber held in the flow field. As the extended polyethylene fiber grows, it is wound up at a rate equal to its extensional growth rate, the tip of the growing fiber thus remaining at a fixed position. The resulting fiber consists of a bundle of shish... 

The deformation and breakup of Boger-fluid drops in Newtonian liquids under simple shear flow were investigated by direct visualization using a specially designed Couette apparatus which enables visuahzation from two different directions (i.e. to get a 3-D image). Four types of breakup modes were observed. Boger-fluid drops ean break up in simple shear flows along the flow axis or the vorticity axis. The breakup mode was foimd to depend on drop size, viscosity ratio, interfacial tension, matrix viscosity and drop phase viscoelasticity. 

Polymer melts are shear thinning, and the changing viscosities of polymer melts usually adds complexity in the study of drop deformation and breakup. To simplify the research, we investigated the deformation and breakup of model viscoelastic drops (Boger-fluid) in Newtonian liquids under simple shear flow. A specially designed Couette apparatus that can be used to visualize the drop in two dimensions was used to obtain a 3-D representation of the droplet. Different breakup modes are presented and the effect of drop size on drop breakup mode is discussed. 

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