Question

The frictional loss in a pipe flow experiment using 0.5 m length, 3 mm diameter pipe (e=0.0020 mm) has produced the following data in Table 1 and Figure 13: The approximate Reynolds number range where significant change in flow characteristics occur is: Table 1: Pipe flow data Head loss (m) Velocity (m/s) Rep 1.000 0.054 0.3076 923 -y = 0.2963x1.7868 0.08 0.4507 1352 R = 0.9657 0.102 0.5580 1674 hu (m) 0.122 0.6363 1909 0.100 0.14 1113 0.7300 2190 ty = 0. 1981x R = 0.9981 0.21 0.8726 2618 0.23 0.8849 2655 0.273 0.9179 2754 0.010 0.1000 10.0000 1.0000 Velocity (m/s) 0.363 1.0578 3173 0.65 1.5859 4758 Fig: 13 Plot of velocity vs h

Answer 1

The Reynolds ( Re ) number is a quantity which engineers use to estimate if a fluid flow is laminar or turbulent.

For pipe flows,

RANGE 1: Laminar Flow (see diagram below) Generally, a fluid flow is laminar from Re = 0 to 2100 at which transition flow begins.

RANGE 2: Transition Flow (see diagram below) Flows in the range of Re =2100 to 4000 may fluctuate between laminar and turbulent flow. The fluid flow is on the verge of becoming turbulent.

RANGE 3: Turbulent Flow (see diagram below) The fluid flow has become unstable. In turbulent flow, there is increased mixing that results in viscous losses which are generally much higher than in those in laminar flow.

LAMINAR TRANSITION TURBULENT - 0 Re -2100 -4000

The Red circled portion in the below figures shows the Re range where significant change in flow occurs

Table 1: Pipe flow data Head loss (m) Velocity (m/s) Rep 1.000 0.054 0.3076 923 0.2963x1.7868 0.08 0.4507 1352 R? = 0.9657 0.102 0.5580 1674 Laminar 0.122 0.6363 1909 h (m) 0.100 0.14 0.7300 2190 ty = 0. 1981x1113 0.21 0.8726 2618 R = 0.9981 0.23 0.8849 2655 Transition 0.273 0.9179 2754 0.010 0.1000 10.0000 0.363 1.0578 3173 1.0000 Velocity (m/s) 0.65 1.5859 4758 7Turbulant Fig: 13 Plot of velocity vs h