Steady Vs Unsteady flow over a cylinder

FLOW OVER A CYLINDER

AIM :

To simulate the flow over a cylinder at steady and unsteady case and also to find the drag over the cylinder at different reynolds numbers

INTRODUCTION:

Reynolds number is the ratio of interia force to the viscous force .it important because this number says wheather the flow is a laminar or turbulent .so, it must to caluclate the reynolds number . the reynolds number is greater then the 2*10power5 in the pipe then it is called the turbulent flow ,if it is less then that then is called laminar flow .And if the reynolds number is greater then the 5*10power5 for flat plate then it is called the turbulent flow .so the reynolds number plays a very important role in the fluid flow .

VON KARMAN

Von karman is the person who says that when flow over a object how the fluid is disturbed and in which patterns the fluid is flows after the passing the object. As the fluid distubance occur in the flow ,how it propagates in the downstream and in the form of vortices that alternate their direction of rotation.And what are the effects causes as that occurs in the flow .this what the von karman mainly says about of it .

PART - 1

steady flow by taking the reynolds number 100

steady flow is the flow where the flow does not with respect to time .above figure shows the steady flow by taking the reynolds number 100

unsteady flow is the flow where the flow varies with respect to time

the above figure shows unsteady case at reynolds number 100

And the above figure shows vortex shedding of the flow behind the cylinder at transient case .

It shows how the flow disturbs when it flows over the object with respect to time .the vortex shedding is most commonly used inthe applications like chimeny's and other .

PART -2

The following plots shows the drag and lift by using different reynolds number

• Reynolds number 10-DRAG

• REYNOLDS NUMBER 10-LIFT

• REYNOLDS NUMBER -100 DRAG

• REYNOLDS NUMBER -100 LIFT

• REYNOLDS NUMBER -1000 DRAG

• REYNOLDS NUMBER -1000 LIFT

• REYNOLDS NUMBER -10000 DRAG

• REYNOLDS NUMBER -10000 LIFT

• REYNOLDS NHUMBER -100000 DRAG

• REYNOLDS NUMBER -100000 LIFT

As we see above all plots are related to drag and lift ,at different reynolds numbers .

these plots shows how the drag and lift of the cylinder varies with different reynolds numbers .

As coming to main point we observe that from the plots as the reynold number increases the total drag decreases.

Reynolds number effects the drag ,as we know that if the reynolds number increases then the viscous force decreases due to the increase in the inertia forces due to the realtive pressure gradient .and as we know higher reynolds numbers are used in cars and aeroplanes .

ANIMATIONS :

As we see the above figure shows the animation

after doing all the prepocessing processes then after entering in to the solution stage,in this stage after all the data given like the materials ,boundaries ,plots and other information.

after doing all that intailize the process and then go the results ,then go the create and then click on the solution animation and after that give the play back period then click ok after the caluclation is done then click on the animation and play it .this how the animation process is done .

By this end of this challenge i have learned

• how to create the vortex shedding at unsteady state
• how to caluclate the drag and lift at different reynolds numbers
• and how to create the animation
• and also i have learned about the von karmen phenomemnon.