there are many.....but if you need the tutorial as well then ANSYS Fluent is the best....

Thank you,  Vikash Kumar Singh Chauhan,for paying attention to my problem.

I have to say ANSYS Fluent is one super powerful tool for simulation.

But as I reviewed nearly all available papers about steam-water direct contact condensation induced water hammer(SWDCCIWH) ,I found that simulations were almost conducted under code like RELAP5,NEPTUNE,WAHA,which were designed for system analysis.Those codes  could give information about systen state but the detailed flow field could not be identified.Comercial CFD softwares have been prevailing for years,but yet no paper about  SWDCCIWH can be found (More specifically,by saying water hammer I indicate pressure surge which is large enough to damage the system instead of gentle pressure oscillation ),

I cannot sure about  what is the barrier that holds those CFD codes back, technical or theoretical?If so ,what is that?

I think in front of CFD, there are still a lot area yet to be exploited. 

Just google and found articles which did use several CFD code on this problem.

https://mediatum.ub.tum.de/doc/1221799/1221799.pdf

http://publications.lib.chalmers.se/records/fulltext/244744/244744.pdf

I suggest using Comsol Multiphysics which includes several models for multi-phase flows. 

    Thank you all for sharing your answers.

     Recently, I have tried to simulate steam-water direct contact condensation through STAR.I chose Multiphase segregated flow ,Large scale model ,coupled with two resistance model  as computing model ,without considering pressure propagation . 

    basic conclusions are listed below:

    1)  Local phenomenon ,like steam slug formation ,temperature evalution,can be very sensitive to parameter change,including mesh size ,initial condition , boundary turbulence  condition ;

    2) Simulation using experimental data with severe pressure peak(magnitude: MPa) ,fails to predict the surge correctly (magnitude: bar ,somtimes KPa),while it is possible for STAR model gentle pressure surge(experimental:bar,simulation:bar).

 During my exploration, I found that the biggest problem should be attributed to  stocastic  nature of two phase flow .

Right now I am still working on this , again appreciating your valuable attention and  looking forward to having further discusstion with you.