Numerical simulation of coupled cell motion and nutrient transport in NASA’s rotating bioreactor Tzu-Chieh Chao, Diganta B. Das ⇑ Department of Chemical Engineering, Loughborough University, Loughborough LE11 3TU, Leicestershire, United Kingdom highlights  Application of a model of suspended particles to determine cell motion/ behaviour in a rotating bioreactor.  Nutrient transport in bioreactor coupled with cell motion and distribution.  Cell motion/distribution quantified depending on cell types, e.g., cell density, and size. graphical abstract Cell volume fraction distribution: (a) time zero, when all particles are floating on the top of the bioreac- tor; (b)–(d) bioreactor starts rotating, the cells are first mixed on the outer region of the radius and then the cell density slowly increases into the inner part of the bioreactor. article info Article history: Received 4 June 2014 Received in revised form 13 August 2014 Accepted 21 August 2014 Available online 28 August 2014 Keywords: Cell culture Mathematical models Diffusion Nutrient transfer Rotating bioreactor abstract Rotating bioreactor, such as the NASA bioreactor, which was designed by the National Aeronautics and Space Administration (NASA), USA, can be used to mimic micro-gravity conditions and simulate the effects of microgravity on cells growth. The cell growth in the bioreactor depends on the nutrient avail- ability which in turn depends on the cell density and distribution within the bioreactor. In this work, we use a numerical model of suspended particle motion to simulate the cell motion and distribution in a spe- cific variant of the NASA bioreactor, namely, the high aspect ratio vessel (HARV) bioreactor. The nutrient distribution in the bioreactor is simulated based on a convection–diffusion-reaction supplemented by laboratory experiments aimed at obtaining the required data. We present the modelling framework in this paper and discuss the most salient simulated results. For example, the simulation results show that the distributions of the cells in the bioreactor appear as concentric circles and that the cells density is higher in the middle of the HARV bioreactor. These cell distributions imply that they may accumulate in the middle of the bioreactor at sufficiently high cell density. The results also demonstrate that the con- centration of nutrient is fairly uniform in the bioreactor but decreases slightly from the outer radius of the HARV bioreactor to the inner radius. This is possibly caused by the higher consumption of glucose due to the higher cell density in the middle of the radius. We expect that the modelling framework in this paper would help optimise the culture conditions for the cells in HARV bioreactors. Ó 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.cej.2014.08.077 1385-8947/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Tel.: +44 1509222509; fax: +44 1509223923. E-mail address: D.B.Das@lboro.ac.uk (D.B. Das). Chemical Engineering Journal 259 (2015) 961–971 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej