combustion with injection of particles: Gravity ON = calculation of DPM is very slow

NiBa · February 3, 2015, 09:02

Hello everyone i have a combustion with injection of particles. i noticed that when i activate gravity the calculation of DPM is very slow and all the particles are incomplete. does anyone know if it is necessary to activate gravity for my problem?
thank you

edoan · February 3, 2015, 14:27

I think gravity will be important if the density difference between the two phases (rhop-rho) is large enough to make the second term non negligible to the first term.

dup/dt = Fd(u-up) + (g(rhop-rho)/rhop) +F

fishball · February 3, 2015, 20:33

Quote:

Originally Posted by NiBa

Hello everyone i have a combustion with injection of particles. i noticed that when i activate gravity the calculation of DPM is very slow and all the particles are incomplete. does anyone know if it is necessary to activate gravity for my problem?
thank you

You could try to change the Step length factor to speed up the calculation of DPM or Particle time step size for unsteady particle tracking.

NiBa · February 4, 2015, 05:36

do you believe that i should increase or reduce the step length factor?
thank you

fishball · February 9, 2015, 01:26

Quote:

Originally Posted by NiBa

do you believe that i should increase or reduce the step length factor?
thank you

I guess you should try to see between the calculation speed and accuracy, but how much particle, max step and calculation time you are using now?

February 3, 2015, 09:02	combustion with injection of particles: Gravity ON = calculation of DPM is very slow	#1
NiBa Member Nikolaos Babilas Join Date: Nov 2014 Posts: 37 Rep Power: 11	Hello everyone i have a combustion with injection of particles. i noticed that when i activate gravity the calculation of DPM is very slow and all the particles are incomplete. does anyone know if it is necessary to activate gravity for my problem? thank you

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February 3, 2015, 14:27		#2
edoan Member Ethan Doan Join Date: Oct 2012 Location: Canada Posts: 90 Rep Power: 13	I think gravity will be important if the density difference between the two phases (rhop-rho) is large enough to make the second term non negligible to the first term. dup/dt = Fd(u-up) + (g(rhop-rho)/rhop) +F

February 4, 2015, 05:36		#4
NiBa Member Nikolaos Babilas Join Date: Nov 2014 Posts: 37 Rep Power: 11	do you believe that i should increase or reduce the step length factor? thank you