There is no built-in method to model high order in one direction only. If your mesh is a well aligned high order brick mesh (solid279), then you can drop midside nodes in two directions. However there is no automated way to drop midside nodes in one direction though. You can use the EMOD command in APDL to modify the element definition. The documentation for solid279 says "An edge with a removed midside node implies that the temperature varies linearly, rather than parabolically, along that edge."
You are navigating away from the AIS Discovery experience