Learning Forum

[Lee]

Hello,

        I encountered a problem when I used the UDF “DEFINE_CG_MOTION” and “DEFINE_ZONE_MOTION”, the warning message below popped up during simulation: Warning: incompatible interaction between moving mesh and dynamic mesh model.

Model and settings description:

(1) As shown in Figure 1, the whole model consists of 3 fluid zone: fluid_1, fluid_2 and fluid_3, each zone is connected with interface. Fluid_2, fluid_3 and wall_bot_f1 are moving with a velocity v, now, I use “DEFINE_CG_MOTION” to control the motion of moving face, and “DEFINE_ZONE_MOTION” for fluid_2 and fluid_3.

(2) Interface settings: Interface_1: wall_bot_f1 and wall_top_f2;

Interface_2: wall_bot_f2 and wall_top_f3;

(3) Dynamic mesh settings:

Deforming: wall_f1

Rigid body: wall bot_f1;

Rigid body: Interface_1;

Rigid body: Interface_1-non-overlapping;

Although the simulation can run normally, I am curious about this problem, what makes this happen? Does this problem influence the simulation result? How to solve it?

I need your help and advice, thanks.

Regards,

[Federico]

Can you provide more context as to why you are using CG_Motion for one and ZONE_Motion for the others?

[Lee]

Hi, Federico,

        There are two reasons:

1.If I use CG_MOTION for fluid_2 and fluid_3, too much surfaces I must set as rigid body in dynamic mesh, as shown in Figure 2;

2."Warning: multiple subdivision required on zone 23. Subdivide using Constant Ratio"

and "negative volume" error will pop up, as shown in Figure 3.

Figure 2

Figure 3