Number of nodes vs number of Cells

- April 16, 2020 at 12:45 pm
  
  Hafiz
  Subscriber
  
  Hello everyone!
  
  I have a few questions.
  
  For tetrahedral mesh in the 3D domain, why the number of cells is higher than the number of nodes?
  
  for example, in my case, For tetrahedral mesh, the ratio is about 5 elements/cells to each node. While, when I generated hexahedra mesh, the ratio is about 1.
  
  Secondly, when we set the size of the element in sizing, why it has a unit of length? Does it refer to the boundary of the face (edge)?
  
  I need detailed information about how the mesh is generated in a 3D case. I much appreciate if any link would also be provided.
  
  Thanks in anticipation.
- April 16, 2020 at 3:57 pm
  
  Rob
  Forum Moderator
  
  What do you need to know? In Mechanical nodes are important, in CFD we use the cells.
- April 16, 2020 at 4:19 pm
  
  Hafiz
  Subscriber
  
  I am trying to insert an image of mesh details in this post but could not.
  
  So, I am explaining here. In my 3D geometry, I generated Hexa mesh and tet mesh one by one separately and compared. Details of these meshes are:
  
  Hexa: Nodes = 2 347 352 Elements = 2 285 837
  
  Tet: Nodes = 646 808 Elements = 3 405 127
  
  So, my question is why the ratio of elements to nodes is ~ 5 for tet mesh? Eventhough, we know that it should be reversed as the ratio of nodes to element is ~ 4 for each tet cell.
  
  How the mesh is generated and nodes are dropped?