How to determine number of prism layers and total height
 

Like the title says, how do you know how many prism layers to use and total height of the prism layers? I was able to calculate my near wall length in order to get my y+ value to be less than 1 at the wall, but I'm not sure how to determine the total length. Attached are two images of my inlet face and a zoomed in picture of a prism layer transition. The cells of the last prism layer are much smaller than the first layer of tetras. Is that concerning? Thank you!

generally speaking you want to accomplish 2 things with your selection of total thickness, number of layers and layer ratio. First, you want to resolve the boundary layer (meaning you want to make sure that it is fully immersed in the prism layers). This usually takes a back seat to the second goal which tends to drive your selections more often than not which is to provide a smooth transition (i.e. growing of cells) from your near wall cell layer to the core mesh.

For example you may be able to capture the boundary layer and satisfy wall y+ with 3 layers but in order to 'blend' that mesh with the core mesh that exists away from wall boundaries you may end up needing 10 layers so that each layer grows thicker until your cell sizes are similar to the core mesh.

There is no 'correct' answer. Many different combinations will likely work, you just need to play around with it to understand how best to accomplish your meshing goals.

Not sure if this works with the tet mesher, but with the trimmer, in the Reference Values for mesh models, there is something called "Maximum Core/Prism Transition Ratio", you can enable and control the ratio between last prism layer and cell size in the core mesh, but watch out you cell count can greatly increase