Flow over a cylinder
Aim :
To simulate the external flow of Air over cylinder at different reynolds number and study the velocity and pressure profile
Introduction:
Air is flowing over the external surface of (over) the cylinder at certain velocity. The reynolds number is calculated and then Reynolds number is increased in order of 20% , 40% , 100% from base simulation and corresponding velocity & pressure profile is to be studied.
Fluid Medium : Air @ 20 deg C
Pressure : 101325 Pa
Properties of Air in the above state:
1. Dynamic Viscosity : 18.13 X 10^-6 Pa.s
2. Density : 1.225 kg/m^3
Geometric of cylinder :
1. Diameter : 0.05 m
2. Length of cylinder = 0.450 m
Calculation :
Re = ( Density of fluid * Velocity of fluid * Diameter of body ) / ( Dynamic viscosity of fluid )
Length of Computation domain = 0.45 m
CASE 1 : Baseline simulation :
V = 6 m/s along X direction.
Re = ( 1.225 * 6 * 0.05 ) / (18.13*10^-6)
= 20270 ( no unit )
Velocity distribution
Pressure distribution
CASE 1 : Re @ 120 %
Re_20 = 1.2 * 20207 = 24324 ( no unit )
V_20 = 7.2 m/s
Length of Domain = 0.45 m
Flow through time (FTT) = 0.45 / 7.2 = 0.0625 seconds
End time = 2 * FTT = 0.125 seconds
Coefficient of drag = 2.2432 N
Velocity distribution
Pressure distribution
Video link :
CASE 3 : Re @ 140 %
Re_40 = 1.4* 20207 = 28378 ( no unit )
V_40 = 8.4 m/s
Length of Domain = 0.45 m
Flow through time (FTT) = 0.45 / 8.4 = 0.0535 seconds
End time = 2 * FTT = 0.1071 seconds
Coefficient of drag = 3.053 N
Velocity distribution
Pressure distribution
Video Link:
CASE 4: Re @ 200 %
Re_100 = 2 * 20207 = 40540 ( no unit )
V_100 = 12 m/s
Length of Domain = 0.45 m
Flow through time (FTT) = 0.45 / 12 = 0.0375 seconds
End time = 2 * FTT = 0.075 seconds
Coefficient of drag = 6.228 N
Velocity distribution
Pressure distribution
Result :
As the Reynold number increases the velocity of flow also increases. Corresponding drag force also increases as square of the velocity.
Velocity Profile reveals that velocity increases above and below the cylinder , but becomes very less or zero at opposite side of input.
Pressure doesnt change after the flow , but increases on input side.