Flow over a cylinder

Aim: To simulate the flow over a cylinder at different Reynolds number. Run a baseline simulation and then calculate the Reynolds number. Then increase the Reynolds number by a factor of 20%, 40%, and 100% then run the transient flow simulation.

Reynolds Number

The Reynolds number is the ratio of inertial forces to viscous forces. The Reynolds number is a dimensionless number used to categorize the fluids systems in which the effect of viscosity is important in controlling the velocities or the flow pattern of a fluid. Mathematically, the Reynolds number is defined as

Re=ρυd/μ

where

ρ=density

v=velocity

d=diameter

μ=viscosity

The Reynolds number is used to determine whether a fluid is in laminar or turbulent flow.

Design parameters:

cylinder diameter: 20mm

cylinder length: 50mm

Flow simulation settings:

working fluid: air

inlet velocity: 10m/sec.

RESULTS:

Baseline simulation:( reynolds number @inlet velocity 10m/sec)

velocity distribution:

pressure distribution:

case 2 : for 20% increased reynolds number :

velocity distribution:

pressure distribution:

case 3: for 40% increased reynolds number :

velocity distribution:

pressure distribution:

case 4 : for 100% increased reynolds number :

velocity distribution:

pressure distribution:

please refer the below google drive link for animation of velocity and pressure profiles.

https://drive.google.com/open?id=1K9Vo9yMWNzZ3CwMr8q1E4ZLgqh-hNOH_

conclusion:

As we increases the reynolds number, the velocity of external flow increases and the time required to attain the steady velocity and pressure profile decreases.