Intermittency index

The intermittent nature of the local solids flow behavior in a riser can be quantified on the basis of the intermittency index defined as [Brereton and Grace, 1993a]... 

The general trend of the intermittency index obtained experimentally for, as an example, U = 6.5 m/s and Jv = 42 kg/m2 s (case (a)) and 62 kg/m2 s (case (b)), is given in Fig. 10.17. The results indicate that the intermittency index varies between 0.1 to 0.7. These values imply that the gas-solid flow in the riser is never solely in the ideal... 

Figure 10.16. Illustration of the definition of intermittency index for three limiting cases (after Brereton and Grace, 1993a) (a) Ideal cluster flow (b) Core-annular flow (c) Uniform dispersed flow.

Johnsson Johnsson, 2001 1.7 X 1.4 X 13.5 Local particle concentration, probability density, intermittency index... 

Figure 9. Idealised clustering and core-annular flow patterns and the corresponding plots of intermittency index versus radius (Brereton and Grace, 1992b).

The intermittency index defined above varies from a value of zero, for a uniform steady flow of any mean density, to a value of unity for a flow of the same density in which the flow consists of clusters of particles, at loose packed density, surrounded by particle free gas. Figure 11 plots the intermittency index versus radial position and height in the developing flow region. Figure 12 shows instantaneous traces from the capacitance probe signal. 

Figure 11. Development of radial profiles of intermittency index for the profiles of Figure 10, Brereton and Grace, 1992).

Some machines, e.g., Bosch GKF, Index, Impressa and Zanasi, are called intermittent motion machines because they exhibit an interrupted filling sequence. That is, indexing turntables must stop at specific stations to execute the various operations described above. Continuous motion machines, e.g., MG2 and Matic, execute these functions in a continuous cycle. Eliminating the need to decelerate and accelerate from one station to the next makes possible higher machine speeds with the continuous motion machines (24). 

Fuel Requirements,— Locomotive cranes are for the most part steam operated and on account of the intermittent nature of their operation average fuel consumption is the most reliable index of power requirements. With coal of average grade, the average fuel requirements for standard sizes of locomotive cranes are ... 

The Gaussian intermittent noise has an autocorrelation function given by Eq. (20) and power-law index given by 277 2. The statistics of this sequence is... 

The Levy-walk intermittent noise is characterized by an uncorrelated waiting-time sequence and a Levy or an inverse power-law waiting-time distribution function such as given by Eq. (97) with 1 < a < 2. This interval for the scaling index insures that although the second moment diverges, the first moment is finite. The presence of a Levy-walk process in a given time series can be detected by means of the asymptotic relation Eq. (99), which we refer to as... 

---