Learning Forum

[Lee]

        Hello,

        I want to simulate the motion of a piston which contains an oil film(about 50 um thick) at the bottom of it, all fluid parts are shown in Figure 1, each fluid zone is connected by interface.

        The moving zones consist of 4 parts, shown in Figure 2:

(1) the bottom face of piston cylinder, which is labelled as moving face;

(2) fluid zone 2;

(3) fluid zone 3;

(4) fluid zone 4;

        During the motion, piston cylinder is in the suction stage, i.e. the moving parts move along the axis-x with the same velocity V, shown as Figure 3.

        I know this motion involves with dynamic mesh and UDF, besides, if without the fluid zone 2, 3, 4, I can use UDF “CG_MOTION” to realize the motion of piston, but once the three other fluid zones are added, I have no idea how to deal with.

       Any advice would be appreciated.

Regards,

Figure 1

Figure 2

Figure 3

 

[Federico]

Hello Lee, 

if all of your moving zones have the same motion, you can assign the same UDF Motion to each of them. In the Dynamic Mesh Zones settings, you will have the option to define individual center of gravity for each zone to differentiate them (although if you're after Rigid Body motion, it won't make any difference).

If you wanted to have different CG_Motion for each zone, you could create different functions for each of them and give each function a different name (1st argument to DEFINE_CG_MOTION).

I hope this helps. Let me know if you have other questions

[Lee]

Hello Federico,

        Really thanks for your answer, it works!

Regards,