After some pondering here is my poorly written starting point.
"Research computing is using computers to enable (improve, speedup, or make possible) all types of research.
It is by its nature an cross-disciplinary space, existing at the intersection of the research feilds conceptual space, computational methods, computing hardware (often in atypical configurations) and physical research equipment, as well as frequently involving atypical issues at the extreme end of large scale, and shared systems.
While all questions in the area are welcome, what best belongs here questions that are both research computing and due to its intersectionality (e.g. scale, HPC, special equipment related etc) does not fit well on any individual topic site. "