This work examines how the angle to the flow of a 1-hole catalyst particle impacts its catalytic performance. Computational fluid dynamics (CFD) simulations are reported for flow past a single equilateral hollow cylinder under methane steam reforming conditions, for 1000 <= Re <= 10,000, and for approach angles from 0 degrees to 90 degrees. The simulations show that at 0, the flat end of the particle causes separation and formation of a large wake region, while a jet-like flow results through the center hole. These flows result in a pattern of vortices behind the particle, with reverse flow along the particle length. These features are distorted as the approach angle increases, with boundary-layer formation on the upstream side of the particle and a complex vortex pattern on the downstream side. The flow through the particle hole decreases with incidence angle. Surface heat and mass fluxes decrease for the flat ends and the inside curved surface, and increase on the outside curved surface. Both reactant consumption and energy uptake show maxima as a result of the changes in transfer rates through the various particle surfaces, caused by the incident flow. (C) 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.