Pulsatile axisymmetric jet in Ansys Fluent (transient)
 

Hello all,

I am trying to simulate a pulsating jet in Ansys Fluent (axisymmetric case, jet is entering quiescence atmosphere), so I defined the transition velocity profile by UDF using this definition for velocity:

u = U + U * eps * sin(omega * t).

I am running transient simulation with time step 0.001 s and the computational method is PISO.

The omega is determined based on Strouhal number.

The problem is that the disturbance is not developing to the flow. It seems like the centreline velocity of the jet is just moving up and down regarding the velocity at the inlet, but no fluctuation or disturbance is developing downstream of the jet.

Does anyone have any idea what can be wrong? It basically shows the same results as it was steady jet expect the inlet velocity is changing in time and so also the curve is moving up an down.

Thank you a lot in advance.