Coefficient roughness

A simplified estimate can be made by first converting the flow at actual conditions to the flow at standard conditions (i.e., at 70 F and 1 atm). The calculation basis for the linear velocity assumes a roughness coefficient of 0.0005 and a kinematic viscosity for air of 1.62 x lO fF/sec. From the ideal gas law, the following expression is developed ... 

Leikis et al,223 used the Parsons-Zobel method to obtain the roughness factor fpz for pc/Ag electrodes. It was found that /pz 1.2, which was explained by the geometric inhomogeneity of the pc-Ag electrode surface. A more detailed analysis is given in Section II.2. Thus it should be noted that in the case of pc electrodes with appreciable differences of EamQvalues for the various planes (AEff o > 100 mV), it is impossible to obtain the true roughness coefficient, the actual Ea=0, and the inner-layer capacity. 

Here e is the roughness coefficient, D is the inside diameter of the pipe, NRe is the Reynolds number of the fluid, and / is the friction factor for turbulent flow inside the pipe. 

The dimensions of n are seen to be TL m. As it is unreasonable to suppose that the roughness coefficient should contain the dimension T, the Manning equation is more properly adjusted so as to contain (g)v2 in the numerator, thus yielding the dimension of Ly for n. In order to avoid converting the numerical value of n for use with English units, the formula itself is changed so as to leave the value of n unaffected. Thus, in foot-pound-second units, the Manning formula is... 

For simplicity, the following treatment is based on channels of rectangular section. The section will be considered sufficiently wide and shallow that we may confine our attention to a section 1 ft wide, through which the velocity is essentially uniform. It is important to bear in mind that all the following development is based on a constant value of the discharge per unit width q and on one value of the roughness coefficient n. Commencing with Eq. (10.121), we may observe that, as V = q/y,... 

TABLE 6.5 Roughness Coefficients (Manning s n) for Closed Conduits... 

The coefficients C or n are determined experimentally for different types of channel linings. A tabulation of Manning roughness coefficients is shown in Table 2-1. For further discussion of these two equations, the reader is referred to Henderson (1966), Dunne and Leopold (1978), or Linsley et al. (1982). 

Then use Table 2-1 to obtain a value of 0.013 for the Manning roughness coefficient for ordinary concrete lining in a channel. 

Over the EPR all their works postulated the logarithmic mean flow distribution (1.1) with a roughness coefficient z0 to be determined empirically. Several relations were suggested for the latter [155] ... 

Bennovitsky, E.L. (1988) Derivation of functional dependences for roughness coefficient of partially vegetated beds, Water resources (Wodnije resourci), N 1, 68-74. (in Russian)... 

Moskow, S., Druskin, V., Habashy, T., Lee, P., Davydycheva, S. A finite difference scheme for elliptic equations with rough coefficients using a cartesian grid non-conforming to interfaces. SIAM J. Numer. Anal., 36, no. 2, 442-464, 1999. 

The Barton-Bandis (BB) model represents the change in the normal and shear stiffness due to the stress change by using JRC (Joint Roughness Coefficient) and JCS (Joint Compression Strength). By using the JRC and JCS (MPa) which is the mean values for each set /, the initial normal stiffness of joint, K i (MPa/mm), is calculated for each set /,... 

For Case HM, pairs of joint roughness coefficient (JRC) and joint compressive strength... 

Zhou Chuangbing Xiong Wenlin. 1996. Relation between joint roughness coefficient and fractal dimension. J. Wuhan Univ. of Hydr. Elec. Eng. 29(5) pp. 1-5... 

---