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Single-Phase Incompressible Flow of Newtonian Fluid
Published in Henry Liu, Pipeline Engineering, 2017
The same engineers who design water pipes, when designing sewers, use the Manning formula as follows: V=1.486nRH2/3Se1/2 where n is the Manning’s roughness coefficient, which is approximately equal to 0.014 for an unpolished concrete surface. The Manning formula was originally developed for designing open channels, not pipe flow. It is not as accurate for sewer pipes flowing full as is the Darcy-Weisbach formula.
A weighting function model for unsteady open channel friction
Published in Journal of Hydraulic Research, 2022
Junwei Zhou, Weimin Bao, Geoffrey R. Tick, Hamed Moftakhari, Qing Cao, Fanghong Ye
From the perspective of the hydraulic variable y, the Manning formula and the modified formula are quite different from each other. Equation (27) illustrates that the Manning formula approximates y as a constant, while Eqs (18)–(23) indicate the modified formula represents y as a time varying variable related to not only roughness factor but also flow unsteadiness. By applying the least square method to Eq. (23), the optimized parameters can be obtained to describe these time varying dependencies. Figure 7 shows that the calculated yt from Eq. (23), termed yw, can match the theoretically inferred value, ysv, extremely well. Hence, Eq. (23) provides a better estimate of the physical dependence on time-varying processes compared to the constant approximation of Eq. (27).
Consideration of submarine landslide induced by 2018 Sulawesi earthquake and tsunami within Palu Bay
Published in Coastal Engineering Journal, 2021
Kaori Nagai, Abdul Muhari, Kwanchai Pakoksung, Masashi Watanabe, Anawat Suppasri, Taro Arikawa, Fumihiko Imamura
The bathymetric and topographic data acquired in 2014 were obtained from the Indonesian Geospatial Information Agency. The data included topographic data with a resolution of 5 m, and the bathymetric data with a resolution of 180 m, both of which were modified to a resolution of 30 m. The density of the first layer representing water was defined 1000 kg/m3 and we assumed the mean density of soil mass as 1500 kg/m3 which equals , based on the study of Macías et al. (2015). The simulation time was 20 min with a time step of 0.01 s, and the bottom stress was determined by using the manning formula. Manning roughness coefficient was set to 0.025 for the entire calculation area. A constant-grid tsunami simulation was performed in the computational domain, with the initial water level of the two-layer model set to +0.7 m, which was the tide level at the time of the earthquake (http://tides.big.go.id:8888/dash/prov/Sulteng.html).
A robust approach for rating curves estimation in open channels using isovel contours
Published in International Journal of River Basin Management, 2021
Arash Ahmadi, Mahmoud F. Maghrebi
This equation presents the challenging issue of determining the exponent values a1, a2, a3, a4, a5 and a6. There are several stages for calculating these values. Firstly, data from measured and theoretical rating curves for different hydraulic cross-sections must be collected. The Manning formula is then utilized to calculate the stage-discharge values for the triangular, rectangular and circular sections at various water levels. The following values are adopted for the cross-sections’ geometry: the circular cross-section’s diameter is 2 m, Hmax=1 m is the width of the rectangular cross-section and the highest water level over the invert, the side slopes of 1(H):1(V) is related to the wall slopes of the triangular channel, in which the highest water level is Hmax=1 m and Manning roughness coefficient is n = 0.015 and bed slope is S0=0.001. An additional cross-section is implemented in order to establish an equation that is accurate for estimating the stage-discharge relationship in compound channels. This additional cross-section is experimentally investigated for discharge estimation from FCF-Series01 (Knight 1992). Table 1 presents the specifications of the compound channel shown in Figure 2.