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ENGR5002 / Week 4
ENGR217 2019 Q B3Past paperOld spec ENGR2172:125 marks30 min

ENGR217 Summer 2019 Q B3[VALID] official answers

Answer ALL parts (a) - (c).

[A Moody diagram is needed for (c). Data Book: water ρ=1000 kg m−3\rho = 1000\ \mathrm{kg\,m^{-3}}. The old data sheet uses the Fanning friction factor, HL=4fLDu22gH_L = \dfrac{4 f L}{D}\dfrac{u^2}{2g}; the current module uses the Darcy factor fD=4ff_D = 4f.]

Formulas you may need
  • Reynolds number: Re=ρvDμ=vDνRe = \dfrac{\rho v D}{\mu} = \dfrac{v D}{\nu}; laminar Re<2400Re < 2400, turbulent Re>4000Re > 4000 (on the formula sheet)
  • Darcy-Weisbach: Δp=fDLDρv22\Delta p = f_D \dfrac{L}{D}\dfrac{\rho v^2}{2} (on the formula sheet)
  • Moody chart / Colebrook: 1fD=−2log⁡10(k/D3.7+2.51RefD)\dfrac{1}{\sqrt{f_D}} = -2\log_{10}\left(\dfrac{k/D}{3.7} + \dfrac{2.51}{Re\sqrt{f_D}}\right) (learn this; a Moody chart would be supplied)
  • Fanning to Darcy: fD=4fFanningf_D = 4 f_{Fanning} (learn this)
  1. (a)
    When a fluid flows steadily along a pipe, there are two possible patterns of flow. Who originally investigated these flow patterns? Describe these two flow patterns, and explain how you could predict which pattern of flow is likely to occur in a given situation.
    [6]
  2. (b)
    Hot water at 50∘C50^\circ\mathrm{C} is flowing along a pipe 800 mm diameter at a mean speed of 2.3 m/s. At this temperature the kinematic viscosity of the water is ν=5.55×10−7 m2/s\nu = 5.55 \times 10^{-7}\ \mathrm{m^2/s}. Will the flow be laminar or turbulent?
    [4]
  3. (c)
    Water at 12∘C12^\circ\mathrm{C} is supplied to a 40 mm diameter steel pipe at 9 bar gauge pressure. The pipe is 125 m long, the roughness is k=0.02k = 0.02 mm, and at the end of the pipe the water is discharged to atmosphere. Estimate the volume flow rate of the water. (Kinematic viscosity for the water is ν=1.22×10−6 m2/s\nu = 1.22 \times 10^{-6}\ \mathrm{m^2/s}).
    [15]