[bruce]

Dear All,

I calculate "sudden" convergent-divergent nozzle flow using pimpleFoam solver (attached a case) Although the geometry is symmetric the outflow jet seems to explode and make non-symmetric solutions after some time.

The case is incompressible with water as medium. And the BC are,

nu = 1.0e-06 (kinematic visosity)

pressure:
inlet: 100e3 (kinematic pressure, but actuall pressure is 100e6 = 100MPa)
outlet: 0
wall: zeroGradient

Velocity U:
inlet: zeroGradient
outlet: zeroGradient
wall: zeroGradient

I actually test different BC like pressureInletVelocity for U and inletOutlet. And very fine grid. The non-symmetrical nature is still persist.

And, I have attached a complete case which is actually a coarse grid for fast calculation.

Since the pressure is driving the flow. Umax is around 480 m/s as the nozzle is so small.

Remark: the geometry is actually nearly same as cacitationFoam tutorial but i use pimpleFoam to solve water flow.

Could somebody help me to figure out why this happens?

Thanks for help.

[bruce]

I want to add how my simulation looks after some time.