In my study, I have two cases for CFD which I performed on Ansys Fluent,

1) oscillating flow over a solid cylinder (blunt face perpendicular to flow direction)

and

2) solid cylinder (blunt face perpendicular to flow direction) oscillating in the stationary fluid. It involves dynamic meshing.

In both of the above cases, I am using the SST k-w turbulence model for this simulation.

[ ie what should be the input value for Turbulent Kinetic Energy and Specific dissipation rate? ]

What does it means if both these values are equal to 1.0?

I have attached a graph representing drag force as a function of time [calculated from the case (2)]. I want to know what might be the possible reason for this behavior in the initial time.

My UFD (equation for velocity of moving cylinder): V = 1.0 * cos(2*3.1415*1.55*t) m/s.

The initial spike? why does this occur?

The decreasing amplitude?

What would be the expected output if this was calculated for longer time values (amplitude behavior after 5 secs)?

Fluid: incompressible (water)

calculation settings:

time-steps = 500, time-step size = 0.01 sec, maximum iterations = 500.

Meshing (element size = 1.0 mm, element shape = triangles)