Friction transition regime

Churchill also provided a single equation that may be used for Reynolds numbers in laminar, transitional, and turbulent flow, closely fitting/= 16/Re in the laminar regime, and the Colebrook formula, Eq. (6-38), in the turbulent regime. It also gives unique, reasonable values in the transition regime, where the friction factor is uncertain. 

The isothermal friction coefficients for the three inlet types showed that the range of the Reynolds number values at which transition flow exists is strongly inlet-geometry dependent. Furthermore, healing caused an increase in the laminar and turbulent friction coefficients and an increase in the lower and upper limits of the isothermal transition regime boundaries. The friction coefficient transition Reynolds number ranges for the isothermal and nonisotliermal (three different heating rates) and the three different inlets used in their study are summarized in Table 8-6. 

This value also suggests that flow is in the transition regime. The corresponding friction factor is ... 

In between there is a transitional regime (II). After a high level of friction with recognisable wear the system moves without any change in the external stress into a low level of friction and wear. The... 

Figure 3 Dynamic recrossmgs m the low and high friction regimes. Recrossmgs back to the reactive state lead to a lowering of the rate constant below the transition state theory value.

As first shown by Caldeira and Leggett [1981], in the tunneling regime friction reduces the transition probability by the factor... 

The Stribeck curve gives a general description for the transition of lubrication regime, but the quantitative information, such as the variations of real contact areas, the percentage of the load carried by contact, and changes in friction behavior, are not available due to lack of numerical tools for prediction. The deterministic ML model provides an opportunity to explore the entire process of transition from full-film EHL to boundary lubrication, as demonstrated by the examples presented in this section. 

Beattie, D. R. M., 1975, Friction Factors and Regime Transitions in High Pressure Steam-Water Flows, ASME Paper 75-WA/HT-4. (3)... 

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