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1 Fundamental Concepts of Fluid Mechanics for Mine Ventilation
Fig. 1.12 Moody diagram for atmospheric air at 20 °C
1. Laminar flow zone, where f is a linear function of Re.
2. Critical zone (Re: 2000–4000), where the flow is unstable and might have either
laminar or turbulent characteristics.
3. Transition zone, where f depends on the values of both Re and the relative
roughness.
4. Fully developed turbulence zone, where f is just a function of the relative
roughness and thus independent of Re (horizontal asymptote).
Exercise 1.7 Air is flowing downstream through a 500 mm diameter cast iron ventilation duct with a circular cross section. The flow rate is 0.9 m
3 s
−1 and the duct
is inclined 15° to the horizontal. Determine the static pressure loss that takes place
along 100 m of the duct.
Data: Roughness of cast iron duct (E): 0.0015 mm, air density: 1.2 kg m
−3 , dynamic
viscosity of air (μ): 1.86 × 10
−5 N
s
m 2 .
1 Fundamental Concepts of Fluid Mechanics for Mine Ventilation
Fig. 1.12 Moody diagram for atmospheric air at 20 °C
1. Laminar flow zone, where f is a linear function of Re.
2. Critical zone (Re: 2000–4000), where the flow is unstable and might have either
laminar or turbulent characteristics.
3. Transition zone, where f depends on the values of both Re and the relative
roughness.
4. Fully developed turbulence zone, where f is just a function of the relative
roughness and thus independent of Re (horizontal asymptote).
Exercise 1.7 Air is flowing downstream through a 500 mm diameter cast iron ventilation duct with a circular cross section. The flow rate is 0.9 m
3 s
−1 and the duct
is inclined 15° to the horizontal. Determine the static pressure loss that takes place
along 100 m of the duct.
Data: Roughness of cast iron duct (E): 0.0015 mm, air density: 1.2 kg m
−3 , dynamic
viscosity of air (μ): 1.86 × 10
−5 N
s
m 2 .