Week 2 - Flow over a Cylinder.

Aim : To simulate the flow over the cylinder under steady and tranisent conditions at Renolds Number 100, show the changes in drag and lift coefficients, velocity contours, pressure contours for flow under different inlet conditions of Renold Number 10, 100, 1000, 10000,100000. Also put some light of Karman vortex street formed in flow over the surfaces.

Introduction: The problem statement defines the basic simulation for the objects moving in a fluid region and effect of this fluid on the object. The practical examples of this problem are plane moving in the air, fish inside a river, automobile running on a road, submarines under the oceans. After simulating this problem we are able to simulate the partical examples of above mentioned objects and able to modify the shape and size according to the forces acting on it under the fluid medium.

When an object translate in any fluidic region such as air, liquid there are different forces acting on the object which can retard their motion or lift/deflect the object from its defined path. This phenomenon mainly depends on the shape and size of the object, so before its practical applications the simulation with same geometry and shape can be performed using ANSYS software to test the object in virtual conditions.

Theory: When an object is pass through the air, liquid medium then the flow of this fluid get deflected according to the shape of the object facing the flow movement. Accordingly, there is a variation in fluid forces before and after the object. Due to this deflection of fluid, the flow separation takes place and boundary layer formation starts from the sharp edges of the object which will cause the change in fluid velocity anf pressure above and below the object, causing two forces to act Lift and Drag. Lift force will deflect the object movement to against the gravity whereas the drag force retard the motion of the object in fluid. The level of flow separation depends on the fluid/object velocity under fully submerged conditions.

Part 1: To simulate the flow over the cylinder under steady and transient conditions with Reynolds Number 100 .

The steady condition is the flow condition where the flow parameters does changes with time at aparticular location whereas in transient conditions, the flow parameters varies with time at a particular location under flow movement.

At Reynolds Number 100, the flow velocity is 2.5 m/s

Part 2: To simulate the flow over cylinder under different flow conditions with Reynolds Number 10, 100, 1000, 10000, 100000 and study the effect on flow pattern and forces acting on a cylinder.

1. For Reynold Number 10, Flow velocity = 0.25m/s

2. For Reynold Number 100, Flow Velocity = 2.5m/s

3. For reynold Number 1000, Flow Velocity = 25m/s

4. For Reynold Number 10000, Flow Velocity = 250m/s