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Water liquid-vapor ejector CFD via Fluent software, solution convergence matter?

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Old   November 8, 2017, 08:42
Question Water liquid-vapor ejector CFD via Fluent software, solution convergence matter?
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hamed
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Hi everyone,
im simulating the water liquid vapor ejector via Fluent software which motive fluid is high pressure and temperature of saturated liquid water around 160C and suction fluid is low pressure and temperature of saturated vapor around 40C. my problem is when i run the simulation the liquid water expanded to nozzle exit and mixing section and reaches to its maximum velocity suddenly water vapor intrude the nozzle section and make huge shock waves and turbulence which makes big fluctuation in continuity and turbulence equation in residuals. once secondary flow reaches near the nozzle throat the primary fluid again start to expand till mixing section and again secondary flow intruder to the nozzle, this cycle repeated t as iterations goes on and doesn't allow the residuals like continuity and turbulence equations reaches to the lower values like 10^-4 or 10^-5. the mass flow rates and pressure and velocity shows same values in each same point of each iteration cycle. for example the maximum value of the velocity is 40m/s for water liquid when its already expanded to mixing section but it changes to another value when secondary fluid intruded inside of nozzle. but the values is same in repeated iterations. i wanted to know first why this phenomena happens in my simulation and second if this is common phenomena should i consider my simulation has converged?!
here i have attached the velocity vector picture at different states as i explained and residuals monitoring values.
i would appreciate it so much before if you can guide me about this problem.
Thanks & Best Regards
Attached Images
File Type: png vel.PNG (12.8 KB, 10 views)
File Type: png vector.PNG (41.7 KB, 10 views)
File Type: png residu.PNG (35.1 KB, 13 views)
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