Momentum Source

Lucia · January 6, 2015, 22:55

Hi, I'm new to CFD and encountering some problem when I want to add a momentum source term.

The source term I want to add is +[angular vel ^2]x[position vector] to the left hand side of NS Equation (and it must be a positive term), which happens due to pressure correction in a transient simulation with increasing angular velocity. My questions:

1. Which momentum source options should I use? I've tried simple dimensional analysis [normal and derivatives] and they have different units with my source
2. If I use this feature, does that mean I'm adding the term to the LHS of NS Equation?
3. Since the value varies with angular velocity and the position vector (the position of the fluid at specific time), which field function (and coordinate) should I use?

Thanks,

Lucia · January 8, 2015, 00:39

Anyone? Any advice will be very welcomed

shuai_manlou · January 17, 2015, 23:42

I am a fresh man in Star CCM+, and i don't know how to add momentum source in this solver. But in Fluent, momentum source can be added by User Defined Functions into cells.
1. the momentum source will not be necessarily in LHS, and can be included in external forces (vector f) in RHS in N-S equations
2. in Fluent, the postion vector can be expressed by x[ND_ND], the angular velocity can be defined by yourself. Thus, you can just define the expression of momentum sources and hooked in the Fluent solver

This is what i know, hope it's helpful

January 6, 2015, 22:55	Momentum Source	#1
Lucia New Member Lucia Antonius Join Date: Jul 2014 Posts: 3 Rep Power: 12	Hi, I'm new to CFD and encountering some problem when I want to add a momentum source term. The source term I want to add is +[angular vel ^2]x[position vector] to the left hand side of NS Equation (and it must be a positive term), which happens due to pressure correction in a transient simulation with increasing angular velocity. My questions: 1. Which momentum source options should I use? I've tried simple dimensional analysis [normal and derivatives] and they have different units with my source 2. If I use this feature, does that mean I'm adding the term to the LHS of NS Equation? 3. Since the value varies with angular velocity and the position vector (the position of the fluid at specific time), which field function (and coordinate) should I use? Thanks,

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January 8, 2015, 00:39		#2
Lucia New Member Lucia Antonius Join Date: Jul 2014 Posts: 3 Rep Power: 12	Anyone? Any advice will be very welcomed

January 17, 2015, 23:42		#3
shuai_manlou Member CAO Liushuai Join Date: Apr 2012 Posts: 30 Rep Power: 14	I am a fresh man in Star CCM+, and i don't know how to add momentum source in this solver. But in Fluent, momentum source can be added by User Defined Functions into cells. 1. the momentum source will not be necessarily in LHS, and can be included in external forces (vector f) in RHS in N-S equations 2. in Fluent, the postion vector can be expressed by x[ND_ND], the angular velocity can be defined by yourself. Thus, you can just define the expression of momentum sources and hooked in the Fluent solver This is what i know, hope it's helpful