If your in-house code solves the divergence-free velocity and pressure formulation, you can specify either velocity or pressure.

Hi Shiyu Xia

You don't need to have both boundary conditions at the same time. Apply one of them, because your geometry automatically sets the other condition the same as pressure. But, if you had any problem switch to another boundary condition and try it again.

regards

Filippo Maria Denaro Ramin Alipour You're totally right. What I really want to ask is how can in the experiment forced those 2 BCs at the same time? Is that even possible?

You don't need to set both the conditions. You only have to set velocity inlet. Under velocity inlet conditions scheme you have provisions to set values for inlet pressure and velocity. The option for same varies from software to software and that option is available in ansys and starccm+ packages.@Shiyu Xia

Rahul Krishna H Hi Rahul, thank you for your answer but my real question is why the experimental paper can put 2 BC at same time?

Especially, at steady state, the velocity he recoded is much much lower than the 30m/s which is BC he applied.

Shiyu Xia

be careful, reading the paper

Article A Photographic Study of Flash-Boiling Atomization

the condition prescribed for the water is Deltap and the estimated water velocity seems simply obtained from Bernoulli.

Filippo Maria Denaro Thank you for your answer.

But, I don't think this velocity is calculated from delta-p at least not from Bernoulli. From Bernoulli, the velocity calculated is 37m/s or higher depends on the temperature for water density 998kg/m^3

The original paper addressed “almost” 30 m/s. I suppose it is an estimation from Bernoulli, maybe for standard density value of water

Dear Shiyu Xia

The reason why you can't is the divergence of term delta P in the Navier stocks equation because it is like depriving the room for balancing the term of velocity throughout the process, and consequently every source of error will result in divergence of the whole. So now how to tackle with? rather than static pressure, the stagnation paper would be used. So that if you are going to insert both simultaneously, go ahead with stagnation pressure that must be calculated from Bernoulli's equation for incompressible or isonthropic flow relation for an ideal gas. Go to the in-house code on change or set the pressure on this premise.

Regards,