Learning Forum

[hmanatunga]

Hi,

I am trying to solve a species transport model (no reactions) coupled with LES k-equation. I have a fuel jet in the middle and a surrounding oxidisier co-flow. The upstream section of the fuel jet includes a converging nozzle. The fuel jet inlet is specified as a mass flow inlet.

I am using PISO with the Ideal Gas law used as the equation of state. 

I have specified the mass flow rate at the fuel-jet inlet, and I am monitoring the mass flow rate at the inlet surface using a surface report. The following plot of this surface monitor (Actual) plotted along with the specified value at the inlet boundary (Target). The total temperature was calculated assuming isentropic conditions. The inlet mach number is very small so the total temp is equal to the static temp. 

Why is the actual value different from the specified value? 

[Rob]

Please can you check the Mass Flux Report in Fluent. Not the surface integral if that's what you were using. 

[hmanatunga]

 

The mass flux report is consistent with the mass flow rate surface integral monitor. Specified value at mass flow rate at the fuel-inlet is around 2E-4 kg/s but the mass flux report at the fuel-inlet is around 1E-4 kg/s. 

 

[Rob]

Please can you post the inlet bc panel? The Forum's been down hence the delay. 

[hmanatunga]

Thank you, Rob. Following are screenshots of the inlet bc panel

[Rob]

With 3D that should work as you're reporting the same surface. How do the other boundaries tie up with the reports? 

[hmanatunga]

Thanks Rob for looking into this. 

inlet-fuel is the only mass flow boundary. There is a co-flow boundary of type velocity-inlet that is defined as 1m/s in the direction normal to the boundary. There is also a larger pressure-inlet surrounding the co-flow boundary with gauge pressure set to 0 Pa (Operating pressure is 101325 Pa) The rest of the domain boundaries are pressure outlets with gauge pressure at 0 Pa. 

Why do you think the reported mass flux through the inlet-fuel different from the one that is specified at the inlet bc panel? Would the non-reflective acoustive wave model have anything to do with this?

I first came across this issue trying to run a non-premixed model of hydrogen jet flame using compressibility effects. 

Below is the latest flux report from my last saved dat file


The latest plot of the surface monitor: It decreases over time