Rough Channels

Evelyn Waugh, the British author of Brideshead Revisited, and more important, the author of Vile Bodies, in which one character, Miles Malpractice, describes a rough Channel crossing as exactly like being inside a cocktail shaker, drank stingers as a signature. ... 

Latent heat High, depth Subcooling parameter Thermal conductivity Surface roughness Channel length Mass flow rate Power, number of sample Number of channels Pressure, precession limit Heat rate Heat flux... 

For Re 2 X 10, the relative roughness that corresponds to the boundary between the smooth and rough channels is k /rQ 0.08. The latter shows that the hydraulic characteristics of the present micro-channels (Table 3.4) are close to characteristics of smooth micro-channels. 

Structure of the turbulent high-speed deflagration propagating in a very rough channel stoichiometric Hj/Oj mixture at 150 torn... 

Figure 8.4.9 shows the time sequence of schlieren photographs of DDT in very rough channel. If is clearly seen... 

Keulegan (K13) applied the semiempirical boundary-layer concepts of Prandtl and von K arm an to the case of turbulent flow in open channels, taking into account the effects of channel cross-sectional shape, roughness of the wetted walls, and the free surface. Most of the results are applicable mainly to deep rough channels and bear little relation to the flow of thin films. 

Keulegan (Kl3), 1938 Extension of Prandtl-von KdrmSn turbulent flow theories to turbulent flow in open channels. Effects of wall roughness, channel shape, and free surface on velocity distribution are considered. 

FIGURE 2.19 Electron micrograph of (a) the rough channel features on a PMMA master as generated by laser-ablation (b) the smooth channel features on the PDMS replica cast from the PMMA master [367]. Reprinted with permission from the American Chemical Society. 

To verify the flow regime and the laminar-turbulent transition, a bronze block was replaced by an transparent altuglas plate. Visualisation with dye revealed a very stable flow for Reynolds numbers up to 2500 for both smooth and rough channels. On the contrary, large eddies were visualised for Reynolds numbers over 3800. Between these two values a stable flow region following turbulent structures were observed. 

Figure 19(a) Poiseuille number as a function of Reynolds number for a rough channel... 

Figure 6.12 Different types of channels in 2D-SACE machining. Machined using a 0.2 mm cylindrical stainless steel tool-cathode in 30 wt% NaOH (a) well-defined linear channel edges and smooth channel surface (b) jagged outline contours with smooth channel surface (c) heat affected edges with smooth channel surface (d) heat affected edges with rough channel surface (e) deteriorated microchannels. Reprinted from [23] with the permission of the Journal of Micromechanics and Microengineering.

Koplik, J., I. Ippolito, and J.P. Hulin. 1993. Tracer dispersion in rough channels A two-dimensional numerical study. Phys. Fluids A 5 1333-1343. 

To my pleasant surprise. Dr. Bonhoeffer decided that I present our paper at Oxford. My trip to England, disregarding the extremely rough channel crossing, turned out to be a tremendous success. It also proved of great impact to me in the following year. 

Morris, H.M. (1968). Hydraulics of energy dissipation in steep rough channels. Virginia Poly technical 19. Virginia Polytechnic Institute Blacksburg. 

Peterson, Jr., D.F., Mohanty, P.K. (1960). Flume studies on flow in steep, rough channels. Proc. 

After validation, the LPBM has been employed to simulate the electroosmotic flows in microgeometries. Besides the straight channel, complex geometries have also been considered, including a rough channel, porous arrays, and even random porous media. The simulation results are also compared with the existing experimental data. 

Although the electroosmotic flow in smooth straight microchannels has been much studied, the results are some way from realistic applications because there are much roughness and cavitations on the wall surfaces instead of ideal smoothness. Sometimes the roughness or cavitation could be used for some special function in microchannel flows. To the author s knowledge, there is only a small amount of published literature which presents an analysis of the EOF in rough channels [1]. This section will introduce... 

The heterogeneously charged rough channel is also simulated here. The chaimel surface zeta potential remains at = —50 mV, and the roughness surface zeta potential ij/r is changed from —10 to —120 mV. The asymmetric potential boundaries destroy the symmetry of the flow. Larger values of the surface zeta potential induce larger velocities near the surface. The flow rate... 

Both roughness and cavitations are fundamental aspects of the surface of a rough channel. In macroscopic flow, no divisions have been made between them. However, in microchannel flow, some difference has been reported on the flow friction between roughness and cavitations. Here the electroosmotic flows in microchannels with cavitations are simulated and analyzed, which has been seldom studied before. 

Rough channels Surface features to enhance transport... 

S. Chibbaro, L. Biferale, K. Binder, D. Dimitrov, F. Diotallevi, A. Milchev, and S. Sued, Hydroklnetic simulations of nanoscopic precursor films in rough channels,/ Stat Mech.—Theory Exp. (2009]. 

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