Question

Compare the maximum thickness of the boundary layer that develops due to uniform flow past a flat plate when the fluid is

(a) air, (b) water, (c) glycerol.

The plate length is 3 m and the approaching fluid velocity is 4 m/s.

Answer 1

given data :

fluid velocity = 4 m/s

plate length = 3 m

answer :

1) The kinematic viscosity of air at 25°C is = 1.57* 10^-5 m2/s.

reynold number =

reynold no. = = 800000

now thickness of boundary layer,

= 0.01646 m = 16.46 mm

repeat the same procedure for water and glycerol.

2)

The kinematic viscosity of water at 25°C is = 8.917* 10^-7 m2/s.

reynold number =

reynold no. = = 13457440

now thickness of boundary layer,

= 0.00401 m = 4.01 mm

3)

The kinematic viscosity of glycerol at 25°C is = 1.1197* 10^-3 m2/s.

reynold number =

reynold no. = = 10717.15

now thickness of boundary layer,

= 0.142286 m = 142.3 mm

summary :

thickness of boundary layer of air is 16.46 mm

thickness of boundary layer of water is 4.01 mm

thickness of boundary layer of glycerol is 142.3 mm