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Absolute Roughness
The Experts below are selected from a list of 153 Experts worldwide ranked by ideXlab platform
Bachir Achour – 1st expert on this subject based on the ideXlab platform

Chezy’s resistance coefficient in an eggshaped conduit
Journal of Water and Land Development, 2018CoAuthors: Imed Loukam, Bachir Achour, Lakhdar DjemiliAbstract:Abstract
When calculating uniform flows in open conduits and channels, Chezy’s resistance coefficient is not a problem data and its value is arbitrarily chosen. Such major disadvantage is met in all the geometric profiles of conduits and channels. Knowing the value of this coefficient is essential to both the design of the channel and normal depth calculation. The main objective of our research work is to focus upon the identification of the resistance coefficient relationship. On the basis of the rough model method (RMM) for the calculation of conduits and channels, a general explicit relation of the resistance coefficient in turbulent flow is established with different geometric profiles, particularly the eggshaped conduit. Chezy’s resistance coefficient depends strongly on the filling rate, the discharge, the longitudinal slope, the Absolute Roughness of the internal walls of the conduit and the kinematic viscosity of the liquid. Moreover, in this work, a simplified method is presented to determine Chezy’s resistance coefficient with a limited number of data, namely the discharge, the slope of the conduit, the Absolute Roughness and the kinematic viscosity. Last but not least, after studying the variation of Chezy’s resistance coefficient as a function of the filling rate, an equally explicit expression is given for the easy calculation of this coefficient when its maximum value is reached. Examples of calculation are suggested in order to show how the Chezy’s coefficient can be calculated in the eggshaped conduit. 
NEW APPROCH FOR THE NORMAL DEPTH COMPUTATION IN A TRAPEZOIDAL OPEN CHANNEL USING THE ROUGH MODEL METHOD
LARHYSS Journal, 2017CoAuthors: M. Lakehal, Bachir AchourAbstract:Normal depth plays a significant role in the design of open channels and in the analysis of the nonuniform flow as well. Currently, there is no analytical met hod for calculation of the normal depth in open channels, including the trapezoidal profile. Current methods are either iterative or approximate. They also consider, unreasonably, Chezy’s coefficient or Manning’s Roughness coefficient as a given data of the problem, despite the fact that these coefficients depend on the normal depth sought. In this study, a new analytical method is presented for calculating the normal depth in an traperzoidal open channel. The method takes into account, in particular, the effect of the Absolute Roughness which is a readily measurable parameter in practice. In a first step, the method is applied to a referential rough model in order to establish the relationships that govern its hydraulic characteristics. In a second step, these equations are used to easily deduce the required normal depth by introducing a nondimensional correction factor. A practical example is considered to better explain the advocated method and to appreciate its simplicity and efficiency.

Chezy’s Resistance Coefficient in a Circular Conduit
The Open Civil Engineering Journal, 2015CoAuthors: Bachir AchourAbstract:In the literature, there is no explicit method for calculating the resistance coefficient of Chezy, especially for a circular conduit. Existing relationships are either implicit or do not take into account all parameters influencing the flow such as kinematic viscosity or the slope of the conduit. In many practical cases, one affects arbitrarily a constant value for Chezy’s coefficient. It is a physically unjustified approach, because Chezy’s coefficient varies with flow parameters, es pecially the filling rate of the conduit and the Absolute Roughness. In this paper, simple and explicit relationships are pre sented for the calculation of Chezy’s resistance coefficient in a circular conduit. These relationships have been established based on the rough model method. The Chezy’s resistance coefficient is expressed in terms of known hydraulic parame ters of the flow in a referential rough model. For fast calculation of Chezy’s coefficient, the simplified method is the most appropriate since it requires only four parameters which are the discharge, the Absolute Roughness, the slope and the kine matic viscosity. The study also shows that the Chezy’s resistance coefficient reaches a maximum whose expression is well defined. Some examples are presented showing how to calculate Chezy’s coefficient in a circular conduit with a minimum practical data.
Stephen Idem – 2nd expert on this subject based on the ideXlab platform

determine the Absolute Roughness of phenolic duct rp 1764
Science and Technology for the Built Environment, 2019CoAuthors: Avinash Paruchuri, Stephen IdemAbstract:An experimental program was conducted to measure the relative and Absolute Roughness of phenolic duct systems connected with a fourbolt flange and cleat joint. Ducts with seven distinct rectangula…

Equivalent round diameter of spiral flat oval ducts
, 1994CoAuthors: B. Townsend, Stephen Idem, F. KhodabakhshAbstract:Friction factors for spiral flat oval ducts were measured over the Reynolds number range 6 {times} 10{sup 4} to 6 {times} 10{sup 5}, based on hydraulic diameter. Aspect ratios ranged from 1.4 to 5.5. When plotted on a Moody diagram, the data closely followed a single relative Roughness curve. It was shown that the flat oval equivalent round equation in the ASHRAE Handbook (ASHRAE 1993) is within 6.2% of a rigorous solution. Since this accuracy is within the accuracy of duct pressure loss calculations, it is recommended that the subject equation be retained for future editions of the Handbook. The Absolute Roughness of the ducts ranged from 0.055 mm (0.00018 ft) to 0.381 mm (0.00125 ft), averaging 0.158 mm (0.00052 ft) for the eight tests. It is therefore recommended that spiral flat oval duct be categorized as “average“ in the “Duct Design“ chapter of the Handbook.
M. Lakehal – 3rd expert on this subject based on the ideXlab platform

NEW APPROCH FOR THE NORMAL DEPTH COMPUTATION IN A TRAPEZOIDAL OPEN CHANNEL USING THE ROUGH MODEL METHOD
LARHYSS Journal, 2017CoAuthors: M. Lakehal, Bachir AchourAbstract:Normal depth plays a significant role in the design of open channels and in the analysis of the nonuniform flow as well. Currently, there is no analytical met hod for calculation of the normal depth in open channels, including the trapezoidal profile. Current methods are either iterative or approximate. They also consider, unreasonably, Chezy’s coefficient or Manning’s Roughness coefficient as a given data of the problem, despite the fact that these coefficients depend on the normal depth sought. In this study, a new analytical method is presented for calculating the normal depth in an traperzoidal open channel. The method takes into account, in particular, the effect of the Absolute Roughness which is a readily measurable parameter in practice. In a first step, the method is applied to a referential rough model in order to establish the relationships that govern its hydraulic characteristics. In a second step, these equations are used to easily deduce the required normal depth by introducing a nondimensional correction factor. A practical example is considered to better explain the advocated method and to appreciate its simplicity and efficiency.

SIZING AN OPEN CHANNEL WITH HORIZONTAL BOTTOM AND CIRCULAR WALLS USING THE ROUGH MODEL METHOD
LARHYSS Journal, 2017CoAuthors: M. Lakehal, B. AchourAbstract:The dimensioning of the channels and especially the computation of normal depth plays a significant role in the practice of hydraulic engineer. The classical methods usually used are graphical or iterative to determine the linear dimensions of a pipe or a channel. They also consider, unreasonably, Chezy’s coefficient or Manning’s Roughness coefficient as a given data of the problem, despite the fact that these coefficients depend on the linear dimensions sought. This problem can be easily solved by the application of a new method called the rough model method or simply the RMM. In this study, this new analytical method is presented and applied for the calculation of the linear dimensions of an open channel with horizontal bottom and circular sides. These linear dimensions are: the normal depth of flow, the width of the base of the channel and the diameter of circular parts of the channel. The method takes into account, in particular, the effect of the Absolute Roughness which is a readily measurable parameter in practice. In a first step, the method is applied to a referential rough model in order to establish the relationships that govern its hydraulic characteristics. In a second step, these equations are used to easily deduce the required linear dimensions by introducing a nondimensional correction factor. A practical example is considered to better explain the advocated method and to appreciate its simplicity and efficiency.

CALCUL DE LA PROFONDEUR NORMALE DANS UNE CONDUITE OVOÏDALE PAR LA METHODE DU MODELE RUGUEUX
LARHYSS Journal, 2014CoAuthors: M. Lakehal, Bachir AchourAbstract:Normal depth plays a significant role in the design of open channels and in the analysis of the nonuniform flow as well. Currently, there is no analytical method for calculation of the normal depth in open channels, including the egg profile. Current methods are either iterative or approximate. They also consider, unreasonably, Chezy’s coefficient or Manning’s Roughness coefficient as a given data of the problem, despite the fact that these coefficients depend on the normal depth sought. In this study, a new analytical method is presented for calculating the normal depth in an egg shaped conduit. The method takes into account, in particular, the effect of the Absolute Roughness which is a readily measurable parameter in practice. In a first step, the method is applied to a referential rough model in order to establish the relationships that govern its hydraulic characteristics. In a second step, these equations are used to easily deduce the required normal depth by introducing a nondimensional correction factor. A practical example is considered to better explain the advocated method and to appreciate its simplicity and efficiency.