# fluid-particle: turbulence change

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 December 16, 2002, 00:58 fluid-particle: turbulence change #1 Alisa Guest   Posts: n/a Dear researchers who are Modeling Particulate flow in a turbulent primary liquid flow: I was expecting some modulation of turbulence of the primary liquid flow as I injected particles (then used 2-way coupling). Unfortunately, I don't see any difference of the fluid properties (e.g., turbulence kinetic energy for example) before and after the particle injections in the primary liquid flow.. Can anyone shed some lights in this matter?? Alisa

 December 16, 2002, 21:08 Re: fluid-particle: turbulence change #2 ff_fan Guest   Posts: n/a How are the linear momentum and particle equations coupled? What volume fraction of particles are in the flow, and what is the Stokes number for your particular case?

 December 17, 2002, 00:36 Re: fluid-particle: turbulence change #3 Alisa Guest   Posts: n/a 1) The Momentum equation is: F=Sum[18*mu*Cd*Rep*Ur/(rop*dp^2*24)+Fothers]mp*DelT This term is used as momentum sink in the primary mometum equation and source in the particulate flow equations. Fothers is the sum of pressure force, virtual mass force, saffman lift force. 2) This is a steady state process and the volume fraction of the particles is ~ 1 %, The Stoke number is [rop*uf*dp^2/(9*mu*L0)] ~20 at the plane of injection. Regards, Alisa

 December 18, 2002, 10:32 Re: fluid-particle: turbulence change #4 chidu Guest   Posts: n/a can you also tell us the density of the particle? that will give the mass loading of the particles. if the mass loading is signifacnt, then the particles will affect the flow. you will have to provide more information. regards, chidu...

 December 18, 2002, 16:00 Re: fluid-particle: turbulence change #5 Alisa Guest   Posts: n/a The density of the particles is 950 kg/m^3 (buoyant particle), water as a liquid fluid (density 1000 kr/m^3) The mass flow rate is 1% od the liquid flow rate (mass/s) Now pls advice me what might be wrong? Alisa

 December 19, 2002, 06:54 Re: fluid-particle: turbulence change #6 chidu Guest   Posts: n/a So looks like your mass loading is 0.01 or 1%. This is quite a small mass loading. To see some change in the flow in a global sense you might need mass loadings of atleast 0.1. What is your flow configuration? Also your particle is not that buoyant. It is almost neutral. Basically your Stokes number is high, so I am assuming that the number of particles in the domain are quite small. Is this true? Regards, Chidu...

 December 20, 2002, 08:34 Re: fluid-particle: turbulence change #7 Jan Rusås Guest   Posts: n/a Are you doing a 4-way coupling, meaning that you calculate source terms for k-epsilon or just source terms for the momentum equations (2-way)? Jan

 December 20, 2002, 14:59 Re: fluid-particle: turbulence change #8 Alisa Guest   Posts: n/a Hi Chidu, Do you have any reference to this statement : To see some change in the flow in a global sense you might need mass loadings of atleast 0.1. ?? I believe that I have seen papers where even though the mass loading is less than 10%, there is an effect. When you say, the mass loading has to be atleast 10%, do you also mean that I can't use Lagrangian partic particle tracking?? Will be eagerly waiting for your response. Alisa

 December 20, 2002, 15:05 Re: fluid-particle: turbulence change #9 Alisa Guest   Posts: n/a Hi, I never used 4-way coupling. In fact I am using a software called "FLUENT", I am not sure how difficult it would be to use 4-way coupling in FLUENT. I am only using 2-way coupling. And I am using Cloud particle modeling as well. Do you have any good reference of 4-way coupling? And do you agree with the Chidu, like he/she thinks that to have an effect on the turbulence, I need at least 10% mass loading?? Regards Alisa