2D v.s. Axisymmetric

Atit

I am modeling the flow in a vertical circular tube. Then the domain is simply a rectangle. I specified the 'space' as axisymmetric by using 'define>model'. The B.C. for the edge of regtangle along the x-axis is 'axis'. I also specified the gravity as "-9.807" in x-direction and "0" in y-direction. After simulation, I got the unexpected result. After changing many settings, I want to check something, then I set '2D' space in 'define>model'. I got the same result as 'axisymmetric' space???

To outline this, I record the results in axisymmetric model, then just simply change the model to 2D (only one single change I did), and run the case again. I found that the results are exactly the same. Can anyone explain this to me please? Had I missed to set anything to make them different?

Thank you for your consideration.

Atit