Learning Forum

[Babin Mohan Dass]

Hallo Engineers,

I am working on the co-rotating twin screw extruder project. In which the CAD model of the screw is imported for the assembly and placed on the origin, the first screw is positioned (0,0,0) at 0° and the second screw is located at a distance of 21,5 mm at 90° according to the alignment of the twin screws (0,0,21.5), respectively. Then the cylinder is imported, and the volume is extracted for the polyflow. To specify the boundary conditions, Group NS was created along the volume. Once this was done,. The meshing was done for the volume and screw as well. The tetrahedron mesh was done for the volume, and the patch conforming method was done for the volume. 
Polyflow Setup
I chose the steady state problem for the FEM task under the Generalised Newtonian Isothermal Flow Problem subtask. Then, I defined the boundary conditions: inflow (fn, fs) is imposed, and outflow (fn,fs) is imposed. Since there was a natural flow, the polymer needed to calculate those conditions were given. screw wall for the first screw is followed by cartesian velocities imposed.
·        1^st Point of axis: (0,0,0)
·        2^nd Point of axis: (0,0,1) 
·        Angular velocity: 10.472 rad/sec
screw wall for the second screw is followed by cartesian velocities imposed.
·        1^st Point of axis (0,0,21.5) 
·        2^nd Point of axis-(1,0,21.5): Here “1” is mentioned since it rotates along -x axis. Also, the points shouldn’t be close; -for example, one can’t enter (0,0,0) or (0,0,0). 
Angular velocity: 10.472 rad/sec
Shear rate dependence of Viscosity is considered with Carreau-Yasuda Model. Units for the setup is set as mm/g/sec/c

While viewing the post, Processor,. The shear rate was supposed to be high on the pitch of the screw and the barrel wall, where the screw pitch and barrel wall will be in contact. In my situation, the clearance between both was 0.24 mm, where the higher shear rate occurs. I am getting more than the required values; for example, the maximum shear rate which I got was 1552000,01 s^-1, which seems to be extremely high. Also, the polymer flow inside the region seems to be inaccurate. Here, I have also uploaded the results from the postprocessor. Please look at this and let me know where exactly the problem lies Here are my Opinion about this issue Also, please correct me if I am wrong.

My thoughts about the Issue Could the problem lie in the CAD data? If so, there is no geometry error while Geometry Check in Spce claim. While I am viewing the results in Post-Processor, the wireframe seems to be disconnected, as the picture represents the error. This is my Opinion about this. But I would like to seek your suggestions on where the problem lies in Cad Data/Setup; if so, please check the given setup that I have given for these conditions. Also, please check on the given boundary conditions, which I have given. All the answers and suggestions are most welcome in this case to review my mistake. Here, I have uploaded the images of the data. The first image shows the wireframe in the postprocessor, where one can see the gaps (my Concern over this Problem). The respective images shows the result of the polymer flow, where one can notice the Issue

 

 

[Prashanth]

Hello: Your moving part orientation might be wrong. So, please cross check them settings. We have many twin screw example cases in polyflow help page with detailed instructions.