ABSTRACT Dry storage cask designs for spent nuclear fuel are submitted to the U.S. Nuclear Regulatory Commission (NRC) for certification under Title 10 of the Code of Federal Regulations (10 CFR) Part 72, "Licensing Requirements for the Independent Storage of Spent Nuclear Fuel, High- Level Radioactive Waste, and Reactor-Related Greater Than Class C Waste." The NRC staff technical review of these designs is performed in accordance with 10 CFR Part 72 and the "Standard Review Plan (SRP) for Spent Fuel Dry Storage Systems at a General License Facility" (NUREG-1536, 2010). To ensure that the cask and fuel material temperatures of the dry cask storage system will remain within the allowable limits or criteria for normal, off-normal, and accident conditions, a thermal review is performed as part of the application's technical review. Recent applications increasingly have used thermal-hydraulic analyses and computational fluid dynamics (CFD) codes (e.g., FLUENT) to demonstrate the adequacy of the thermal design. Therefore, in cooperation with the Division of Spent Fuel Storage and Transportation of the Office of Nuclear Material Safety and Safeguards, the Office of Nuclear Regulatory Research developed this guide to provide practical advice for reviewing CFD methods used in vendor applications and for achieving high-quality CFD simulations of a dry cask. To assist in the analysis, the report includes procedures, analysis methods, and acceptable assumptions.