{"id":346500,"date":"2024-01-25T07:40:37","date_gmt":"2024-01-25T07:40:37","guid":{"rendered":"\/forum\/forums\/topic\/how-to-add-velocity-or-acceleration-to-solids\/"},"modified":"2024-01-25T07:40:37","modified_gmt":"2024-01-25T07:40:37","slug":"how-to-add-velocity-or-acceleration-to-solids","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/how-to-add-velocity-or-acceleration-to-solids\/","title":{"rendered":"How to add velocity or acceleration to solids?"},"content":{"rendered":"

Hi everyone, I am trying to study the effects of a moving body on the pressure drop of a fluid flowing within the moving body. The moving body should be undergoing rigid body motion. I have tried many ways to simulate this but I am having trouble getting it to work properly. I will list the methods I have tried thus far below.<\/p>\n

Method #1:<\/p>\n

I created a DEFINE_ZONE_MOTION UDF that models constant acceleration and added it to “mesh motion” in “cell zone conditions” for my solid. I then used a transient solver to be able to capture the difference in velocity with respect to time. This worked well for lower acceleration values for a while but as I increased the acceleration, the pressure drop started to remain constant, which should not be the case. I tried reducing time step and overall transient time but neither solved this issue.<\/p>\n

An example of the UDF used is this:<\/p>\n

#include “udf.h”<\/strong>
 DEFINE_ZONE_MOTION(acceleration_2_neg,omega,axis,origin,velocity,time,dtime)<\/strong>
{<\/strong>
 real a = 2.0;<\/strong>
 real cruise = 60.0 \/ 3.6;<\/strong>
 real currentvelo;<\/strong><\/p>\n

 if (time <= cruise \/ a)<\/strong>
 {<\/strong>
 currentvelo = a * time * -1.0;<\/strong>
 }<\/strong>
 else<\/strong>
 {<\/strong>
 currentvelo = cruise * -1.0;<\/strong>
 }<\/strong><\/p>\n

 N3V_D (velocity,=,currentvelo,0.0,0.0);<\/strong>
 return;<\/strong>
}<\/strong><\/p>\n

 <\/p>\n

Method #2:
I tried to add a constant translational velocity to “mesh motion” in “cell zone conditions” for my solid. The problem with this is that no matter what magnitude I put as the velocity, the outlet pressure of the fluid remains constant as well.<\/p>\n

Method #3:
I tried using a DEFINE_GRID_MOTION UDF and attached it to the solid via dynamic mesh. However, I can’t get this to run at all because I will encounter a negative cell volume issue. I am reluctant to use dynamic mesh too because it would take way too long to process.<\/p>\n

 <\/p>\n

Are there other possible ways to add rigid body motion to a solid? My mentor suggested to simply use boundary conditions to add a constant velocity to the solid wall but I cannot find any way to do this directly within the software.<\/p>\n

Any help will be greatly appreciated, thank you in advance! <\/p>\n","protected":false},"template":"","class_list":["post-346500","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t