Learning Forum

[Ammar Ahmed]

Hello everyone, I am trying to simulate swrilling flow through a coaxial swirl injector. I am giving pressure inlet conditions. Vlume of fluid is used and the fluid(water and ethanol) enters the injector's inlet at total guage pressure of 6 MPa  and 0 MPa initail guage pressure with operating pressure set to 101325 Pa. What i cannot understand is how my pressure that is achieved is around 7.7 MPa. Because according to my understanding pressure drops when it passes thorugh a constricted region and turbulence is high. The boundary conditions are:
Top six faces as single pressure inlet with turbulence 10% and hydraulic dia about 5mm
bottom six faces as single pressure inlet with turbulence 10% and hydraulic dia as 4mm
The geometry with result is shown below:

[Sameer Kulkarni]

Hello,

As far as I can see, the maximum pressure is about 7.6 MPa and not the average pressure. If you take the average, then it should be lower I assume. And one more thing, when you apply the swirl to the fluid, basically you are trying to impart the radial pressure gradient to the fluid. Therefore, this type of behaviour could be expected.

[Sameer Kulkarni]

You can also check the mesh quality and the resolution. If the maximum pressure exists on a small region, then it would not make much difference in the overall results.

[Ammar Ahmed]

Thankyou for your reply, yes i validated a research paper on this. However, how do I ensure I get specific output pressure with specified inlet conditions, because in this case, I am expecting to achive a pressure drop of 1 to 2 MPa, which means I should get 5.5 or 5 MPa at outlet.  

[Sameer Kulkarni]

What is the current average pressure at the outlet? And how did you determine that?

[Ammar Ahmed]

This is the static pressure contour formed and average values is about 276 kPa near the top of vertical walls of domain and it is calculated by surface integral facet average.

 

[Sameer Kulkarni]

Thanks for the sharing the screenshot. To obtain the required pressure at the outlet, you can just apply the required pressure at the outlet. I beleive you would need to choose pressure-outlet boundary condition.

[Ammar Ahmed]

thankyou i think thi will help out a great deal.

[Ammar Ahmed]

thankyou very much for the help it resolved all my issues.