Influence of Roughness

1) For low vapor pressure, only one capillary bridge is formed at the outmost asperity. To calculate the capillary force, the asperity is usually assumed to have a spherical shape and the formalism developed in the previous section is applied. Since the asperity has a small radius of curvature, the capillary force will be low. For the remaining part, the asperity creates an effective gap between the two surfaces, which prevents liquid from condensing unless a certain minimal vapor pressure is reached (see Exercise 5.2) [484, 553, 557). 

2) At intermediate vapor pressure, more and more capillary bridges are formed. To quantify the capillary force, the force of one asperity is either multipUed by the number of asperities or a distribution of asperities is assumed [496, 498, 500, 549]. 

3) At high vapor pressure, the menisci merge into one continuous capillary bridge. The mean, apparent shape of the interacting surfaces dominates the total capillary forces. 

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Dippeiy and Sabersky [Int. ]. Heat Mass Transfer, 6, 329 (1963)] present a complete discussion of the influence of roughness on heat transfer in tubes. 

In a remarkable paper K. I. Shchelkin discovered the influence of roughness of the walls on the transition from combustion of a gas to detonation. He explained this influence by turbulization of the gas. Following this Ya.B. noted the role of the velocity profile, i.e., the non-uniform distribution of velocity over the tube cross-section. It has now become clear that both factors are very significant. Roughness of the walls has significant influence also on the losses, on the detonation speed, and on the limits. 

Schematic representation of two sets of electrodes of palladium (a) and textile electrode (b) and the influence of roughness of the electrode surface on the measured impedance (Z). 

Figure 14. Influence of roughness on flow regime in microchannels (After [26])...

Estimation of the relative influence of roughness on different binding mechanisms... 

The curves were calculated for spheres with constant diameter x=2R 0/xm. The corresponding values of can be determined from Figure 66(b). For van der Waals forces two additional curves were plotted for jR = 0.5 /xm and jR = 50/xm, since—because of their short range character—the influence of roughness on van der Waals forces is very pronounced. 

The electrostatic attraction forces of electrical conductors and of insulators with excess charges are smaller than the van der Waals forces. However, the influence of roughness is less pronounced and disappears completely for nonconducting particles facing a plane with an opposite charge of the same density. 

There are insnfficient data in the literatnre to provide a reliable estimate of the effect of roughness on friction loss for non-Newtonian flnids in tnrbnlent flow. However, the influence of roughness is normally neglected, since the laminar bonndary layer thickness for such fluids is typically much larger than for Newtonian fluids (i.e., the flow conditions most often fall in the hydraulically smooth range for common pipe materials). An expression by Darby et al. (1992) for / for the power law flnid, which applies to both laminar and turbulent flow, is... 

In the book [117], some data are given on the hydrodynamic characteristics of bodies of various shapes these data mainly pertain to the region of precrisis self-similarity. The influence of roughness of the cylinder surface and the turbulence level of the incoming flow on the drag coefficient is discussed in [522]. In [211], the relationship between hydrodynamic flow characteristics in turbulent boundary layers and the longitudinal pressure gradient is studied. Analysis of the transition to turbulence in the wake of circular cylinders is presented in [333]. 

Schwartz, H. 1980. Two dimensional feature shape indices. Mikroskopie (supplement) 37 64-67. Schwartz, L.M., P.N. Sen, and D.L. Johnson. 1989. Influence of rough surfaces on electrolytic conduction in porous media. Phys. Rev. B 40 2450-2458. 

R. L. P. Voisinet, Influence of Roughness and Blowing on Compressible Turbulent Boundary Layer Flow, Naval Surface Weapons Center TR 79-153, Silver Spring, MD, June 1979. 

In 2003, Tsionsky, Daikhin, Urbakh, and Gileadi [21] published a very thorough treatment of the metal/solution interface as examined by the electrochemical quartz crystal microbalance, with emphasis on the misinterpretations of data that can occur if the basic physics and chemistry at the interface are not understood. Topics covered include the electrical double-layer/electrostatic adsorption, the adsorption of organic and inorganic species, metal deposition, and the influence of roughness on the response of the QCM in liquids. 

The influence of roughness in the nanometer scale on cell behavior is controversial, and can be due to the changes that it induces in other physicochemical properties, such as wettability and Z-potential [33]. This will mainly influence the layer of proteins that are adsorbed on those surfaces. This... 

E. Cuesta, J.C. Rico, P. Fernandez, D. Blanco, G. Valino. Influence of roughness on surface scanning by means of a laser stripe system, Int. J. of Advanced Manufacturing Technology. 43 (2009)1157-1166. 

Figure 4.14. Adhesion between bodies of different size, compared to gravity, showing Uradicy s rule and the influence of roughness.

Influence of Roughness on Adhesive Force. Using the equivalent radius of curvature, let us now estimate the adhesive force between smooth spherical particles and a rough steel surface finished by surface grinding to various finishes, Classes 5-13. The quantities defining the roughness of this surface are listed in Table V.2. 

Forces of Particle Adhesion with Allowance for Roughness. The concepts developed in [150-152] relative to the influence of roughness on adhesion now enable us to turn again to a consideration of how the adhesive force varies with particle size. 

The influence of roughness on the adhesive interaction of cylindrical particles is evaluated in accordance with Eq. (V. 11), which we will represent in the following form ... 

On the rough steel surface, the force of adhesion of the spherical particles was somewhat greater than on the smooth glass surface, thus providing indirect evidence of the influence of roughness on the magnitude of adhesive interaction. 

An increase in surface roughness led to an increase in i det only in the case of fine particles with a diameter of 20 jum surface roughness did not have any great effect on det for coarser particles (above 50 jum). This is in accord with views as to the influence of roughness (see Fig. V.2) on adhesion. Roughness may shield the adherent particles from the stream or may change the nature of the stream action on these particles. 

Daikhin LL GUeadiE, Katz G, Tsionsky VM, Urbakh M (2002) Influence of roughness on the admittance of the quartz crystal miciobalance immersed in liquids. Anal Chem 74 554—561... 

One the first attempts at understanding the influence of roughness on wetting is due to Wenzel (1936). We assume that the local contact angle is given by Young s relation [equation (9.1)], and we seek to determine the... 

In common practice, it is assumed that the influence of roughness is the same on both intensities, in other words that/ Aa/f Bb = L When the kinetic energy analyzer is used in the constant-analyzer energy mode (CAE) (cf. the section on Lens System and Energy Analyzer), which is required for quantitative analysis, the residual kinetic energy of the electron reaching the detector is the same whatever its initial kinetic energy therefore, T>Aa/T>Bb = 1- The above equation may then be rewritten... 

D. A. Ramsey and K C. Ludema, The influences of roughness on film thickness... 

The influence of roughness and materials on the friction trends was firstly investigated, particularly imder mixed and boimdary lubrication conditions [5]. Rectangular contacts between the flat surfaces of discs and cylindrical specimens, all with the same shape, were tested. Some wear effects were found after tests under mixed lubrication. 

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