A series of steady-state Computational Fluid Dynamics simulations has been carried out to estimate the liquid flow forces acting on Chinese Hamster Ovary-K1 cells, which are necessary to detach the cells from a non-coated wall surface in a microchannel. The simulation parameters were based on experimental work of Zhang et al. [16]. Simulations were performed for cell sizes of 5 mu m, 12 mu m and 20 mu m with three simply modeled cell shapes respectively. Additionally, a drag coefficient for each modeled cell shape was estimated. The simulation results indicate that the surface-averaged total forces, which are necessary to detach those cells, were in the nanonewton range and increase with cell size. For the force components along and perpendicular to the direction of the flow, the viscous forces accounted for the major proportion. Concerning the velocity gradients, the local energy dissipation rates reach values of at least 4e + 05 W/m(3) at the top of the cell surfaces for each modeled cell shape. The drag coefficient calculations, with Reynolds numbers smaller than 1, have shown an increasing drag coefficient with a decreasing modeled cell size. (c) 2013 Elsevier B.V. All rights reserved.