Query.RankingModelId property
SharePoint 2013
Applies to: Microsoft SharePoint Server 2010 search
Gets or sets the identifier (ID) of the ranking model to use for the query.Assembly: Microsoft.Office.Server.Search (in Microsoft.Office.Server.Search.dll)
Do not use this property with FAST Search Server 2010 for SharePoint; if used, it will be ignored. You instead specify the rank profile using the Sort class.