Eccentric flow channel

Fang, R, R.M. Manglik, and M.A. Jog, Characteristics of laminar viscous shear-thinning fluid flows in eccentric annular channels. Journal of Non-Newtonian Fluid Mechanics, 1999. 84(1) 1—17. 

The afore-mentioned types of flow take place in various combinations, according to the geometry of the bin, and the properties of the bulk material, to give various global patterns of behaviour. Common forms are shown in the various figures. Complications arise when the flow channel is offset from the centreline of the container, or flow becomes eccentric to the container walls. Flow zones and channels follow similar lines to those of concentric systems, but stress evaluation in these cases is usually the domain of the expert. 

The most damaging condition for most silos is the unplanned occurrence of unsymmetrical flow regimes, if the flow channel makes contact with the silo wall. This is conventionally referred to as eccentric discharge. It has caused so many silo disasters that many writers have proposed that it should never be used. But two situations arise it may be necessary to have off-centre discharge outlets for functional reasons, and conditions in the silo (blockage of feeders, uneven thermal or moisture conditions, segregation of contents etc.) may cause unintended eccentric flow. There are numerous causes of such eccentricities. 

Figure 3.23 Flow channel geometry, typical pressure pattern and vertical waU stresses during eccentric discharge.

Before closing this chapter, we feel that it is useful to list in tabular form some isothermal pressure-flow relationships commonly used in die flow simulations. Tables 12.1 and 12.2 deal with flow relationships for the parallel-plate and circular tube channels using Newtonian (N), Power Law (P), and Ellis (E) model fluids. Table 12.3 covers concentric annular channels using Newtonian and Power Law model fluids. Table 12.4 contains volumetric flow rate-pressure drop (die characteristic) relationships only, which are arrived at by numerical solutions, for Newtonian fluid flow in eccentric annular, elliptical, equilateral, isosceles triangular, semicircular, and circular sector and conical channels. In addition, Q versus AP relationships for rectangular and square channels for Newtonian model fluids are given. Finally, Fig. 12.51 presents shape factors for Newtonian fluids flowing in various common shape channels. The shape factor Mq is based on parallel-plate pressure flow, namely,... 

Figure 13.9. Flow of a Bingham material in a planar channel with an eccentric cylinder, Bn 125. (Calculation by J. P. Singh.)...

Evaluated nuclear data used in reactor physics calculation Mismatch of calculated power distribution Uncertainty of fissile content in fuel Assembly hydraulic resistance and orifice uncertainty Intra-assembly flow mal-distribution Geometrical tolerances of fuel rod displacement or expansion on coolant channel flow area Eccentric position of fuel pellet within the cladding Uncertainties from coolant properties... 

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