Steady Vs Unsteady flow over a cylinder

AIM:To Simulate the flow over a cylinder with the given conditions.

In this challenge we have two main parts i.e,

in Part 1 ,

We have to Simulate the flow over the cylinder with the steady and unsteady case and calculate the Strouhal Number for Re= 100.

And in Part 2 ,

we need to simulate and Calculate the coefficient of drag and lift over a cylinder by setting different Reynolds number i.e, 10,100,1000,10000 & 100000 with steady solver and Discussing the effect of Reynolds number on the coefficient of drag, along with that we need to explain the explain the phenomenon of Karman vortex street.

The technical data we have is 2m diameter 2d cylinder with the 20m length to the right side of the cylinder, 40m length to left side of the cylinder, 10m each for bothe above and below the cylnder, and with the inlet velocity of 1m/s.

Procedure

In sketch we will create a drawing acroding to the technical data available above and then we will convert that sketch into surface using pull tool, the following image with the name "Surfaced Component"shows the converted surface element.the sketch can be seen by the following name ''Surface…nent.jpg''

Next Step is to Meshing and giving name to the elements, here the meshing size is 0.25m at this value we can get the optmimum results and also we can not reduce the mesh sieze further because of student versition software limitation. While meshing we use method to change the quadri dominent mesh to triangle dominent mesh, sizing option to increse the capture of the velocity distribution around the cylinder and also infiltaration layers to capture the velocity distribution carefully.

The next step will be set up the physical parameters and setting the fluid propertis, adding monitering points and counter plots etc. in SETUP menu. and after that we wil calculate the coefficient of drag and lift.

Part 1

we will Simulate the flow with the steady and unsteady case and calculate the Strouhal Number for Re= 100 and the mesh size is 0.25mm, for Re=100 the velocity will 0.2 m/s.The follwing are the results for both Steady and unsteady case

Steady state flow with Reynold’s number 100 i.e., velocity=0.2 m/s the flowing are the plots obtained after the simulationFor below uploaded phots with the starting name "steady" are the plots obtained for coeffient of lift, coefficient of drag,residuals, vertex average ,velocity magnitude,Pressure distribution plots and velocity distribution plots .

Unsteady flow with Reynold’s number 100 i.e., velocity=0.2 m/s the flowing are the plots obtained after the simulationFor below uploaded phots with the starting name "trans" are the plots obtained for coeffient of lift, coefficient of drag,residuals, vertex average ,velocity magnitude,Pressure distribution plots and velocity distribution plots.

Part-2

By varying the Reynolds number from 10,100,1000,10000 and 100000 we are going to calculate the the coefficient of lift and Drag and for the above Reynolds number we will get the following velocitys values i.e, 2 m/s, 0.2 m/s, 0.02 m/s, 0.002 m/s, 0.0002 m/s respectively

For the velocity 2 m/s i.e. Re=10 the below uploaded phots with the starting name "velocity 2" are the plots obtained for coeffient of lift, coefficient of drag,residuals, vertex average ,velocity magnitude,Pressure distribution plots and velocity distribution plots .

For the velocity 0.2 m/s i.e. Re=100 the below uploaded phots with the starting name "velocity 0.2" are the plots obtained for coeffient of lift, coefficient of drag,residuals, vertex average ,velocity magnitude,Pressure distribution plots and velocity distribution plots .

For the velocity 0.02 m/s i.e. Re=1000 the below uploaded phots with the starting name "velocity 0.02" are the plots obtained for coeffient of lift, coefficient of drag,residuals, vertex average ,velocity magnitude,Pressure distribution plots and velocity distribution plots .

For the velocity 0.002 m/s i.e. Re=10000 the below uploaded phots with the starting name "velocity 0.002" are the plots obtained for coeffient of lift, coefficient of drag,residuals, vertex average ,velocity magnitude,Pressure distribution plots and velocity distribution plots .

For the velocity 0.0002 m/s i.e. Re=100000 the below uploaded phots with the starting name "velocity 0.0002" are the plots obtained for coeffient of lift, coefficient of drag,residuals, vertex average ,velocity magnitude,Pressure distribution plots and velocity distribution plots .

The effect of Reynold’s number on the drag is “with the increase in Reynolds number will reduce the time required by the flow to come to steady state

Karman Vortex Street : in fluid the repeating pattern of swirling vortices , caused by a process known as vortex shedding which is responsible for the unsteady separation of flow of a fluid around blunt bodies, this phenomenon is called Karman vortex street named after the engineer.