IMS-UNIPD @ CLEF eHealth Task 2: Reciprocal ranking fusion in CHS

In this paper, we describe the results of the participation of the Information Management Systems (IMS) group at CLEF eHealth 2021 Task 2, Consumer Health Search Task. We participated in the three subtasks: Ad-hoc IR, Weakly Supervised IR, Document credibility. The goal of our work was to evaluate the reciprocal ranking fusion approach over 1) manual query variants; 2) different retrieval functions; 3) w/out pseudo-relevance feedback; 4) reciprocal ranking fusion.