The variables that describe the flow in a pipe are: flow rate, Q ([m.sup.3] [s.sup.-1]); pipe internal diameter, D (m); pipe length L (m),

friction factor (f), which depends on the roughness of the pipe internal surface [epsilon](m) and on the Reynolds number (R); and head loss [h.sub.f](m).

where R is the Atkinson resistance, N[s.sup.2]/[m.sup.8]; [Q.sup.2] is the quantity of airflow, [m.sup.3]/s; k is the

friction factor, kg/[m.sup.3].

Both the

friction factor and seals were tested by CANMET, the Canada Centre for Mineral and Energy Technology in Sudbury, with great success.

The side

friction factor is commonly used as the indicator of skidding, and the lateral acceleration and lateral load transfer ratio are adopted to measure the risk of rollover.

Then, the two meshed components are matched and their interface is modeled by means of surface-to-surface contact elements (CONTA173 and TARGE170) with zero initial gap and isotropic friction (

friction factor f = 0, 0.15, 0.3, and 0.45).

They reported that the maximum Nusselt number and

friction factor are around 3.6 and 3.67 times above the smooth duct, respectively.

CCFL characteristics in vertical pipes can be computed by using the annular flow model with the maximum flow condition of ([partial derivative][J.sup.*.sub.L]/[partial derivative][alpha]) = 0 or ([partial derivative][J.sup.*.sub.L]/[partial derivative][alpha]) = 0 and correlations for the interfacial

friction factor and the wall

friction factor (Richter [9]; Bharathan and Wallis [20]; Sudo [21]; Yamamoto et al.

As shown in Figure 4, the motion of a curved surface slider is characterized by at least three phases, which corresponds to different

friction factors: [[mu].sub.0] is the static friction relative to the onset of motion; [[mu].sub.dyn] = [mu] is the dynamic friction during the sliding with velocity similar to the design one; [[mu].sub.1] is the

friction factor corresponding to the change of velocity sign.

The results show that the

friction factor of flow decreases when the Reynolds number and particle aspect ratio become larger.

The channel

friction factor can be computed along the test section by pressure loss, [DELTA]P, as

The important parameters are Reynolds number (Re),

friction factor (f), Nusselt number (Nu), and thermal enhancement factor (TEF).

The values of

friction factor depend mainly on the particular pair of contacting surfaces, the material properties and the surface roughness of the bodies between the frictions occurs [8, 9].