Rolling regime

Another example is related to the motion of defects (dislocations in the roll pattern) which constitutes the basic mechanism of wavevector selection. In the normal-roll regime, the stationary structure is characterized by the condition q II H. However, when changing the field direction one can easily induce a temporary wavevector mismatch Aq = q ew — qoid which relaxes via a ghde (v II q) motion of defects. Experiments have confirmed the validity of detailed theoretical predictions, both with respect to the direction (v J. Aq) and the magnitude (consistent with logarithmic divergence at Aq —> 0) of the defect velocity v [42]. 

Droplets appeared on the surface of the pipe (Fig. 5.33b) after increasing the water flow rate up to I/ls = 0.007 m/s. Spedding et al. (1998) referred to this regime as film plus droplet pattern. When the water flow rate increased and superficial liquid velocity was Gls = 0.03 m/s (Fig. 5.33c) droplets began to roll back into the liquid film. Kokal and Stanislav (1989) identified such a regime as annular plus roll wave flow pattern. The experimental facility used in the present study allowed us to achieve values of superficial gas velocities up to 20 m/s in the 49.2 mm pipe. 

The relationship between film thickness of hexadecane with the addition of cholesteryl LCs and rolling speed under different pressures is shown in Fig. 25 [50], where the straight line is the theoretic film thickness calculated from the Hamrock-Dowson formula based on the bulk viscosity under the pressure of 0.174 GPa. It can be seen that for all lubricants, when speed is high, it is in the EHL regime and a speed index 4> about 0.67 is produced. When the rolling speed decreases and the film thickness falls to about 30 nm, the static adsorption film and ordered fluid film cannot be negligible, and the gradient reduces to less than 0.67 and the transition from EHL to TFL occurs. For pure hexadecane, due to the weak interaction between hexadecane molecules and metal surfaces, the static and ordered films are very thin. EHL... 

The unit of Pf here is MPa is the kinetic viscosity of lubricant in mm /s u is the velocity in mm/s, for the oil without polar additives, k is 23.5 X 10". If the tribo-pairs need to be lubricated with the fluid film in the TFL and EHL regime, the lubricant and the rolling speed should be chosen according to the pressure applied as Eq (9) so as to make that the liquid factor L is larger than the failure fluid factor L. Otherwise, the liquid film caimot be maintained under the pressure added. 

MICROS mill can operate both in batch and continuous regime vertical and horizontal types of working vessel arrangement are possible. Ring roll mills were successfully used for mechanochemical synthesis of Ca3(P04)2-nH20 from Ca(H2P04) H20 and Ca(OH)2 [12]. 

FIGURE 432 Korpela s [162] plot of Rar governing the stability of the conduction regime in a vertical rectangular parallelepiped cavity with W/L a 5 and H/L a 40. For Pr < 12.7, the instability leads to stationary, horizontal axis rolls for Pr > 12.7, it leads to unsteady, vertically traveling waves. 

The details of the flow in the mixed convection regime have been clarified by Gilpin et al. [113]. After an initial development of the laminar forced convection boundary layer, rolls with axes aligned with the flow appear at the location marked Onset in Fig. 46. These persist until the end of the transition regime, marked Breakup, after which the motion appears as fully detached turbulent natural convection flow. 

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