This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.The von Willebrand factor (vWF), a large multimeric protein, is essential in hemostasis. Under
normal conditions, vWF is present in blood as a globular polymer. However, in case of an injury, vWF is able
to unwrap and bind to the vessel wall and to flowing platelets. Thus, platelets are significantly slowed down
and can adhere to the wall and close the lesion. Nevertheless, it is still not clear how the unwrapping of the
vWF is triggered. To better understand these complex processes, we employ a particle-based hydrodynamic
simulation method to study the behaviour of vWF in blood flow. The vWF is modelled as a chain of beads
(monomers) connected by springs. In addition, the monomers are subject to attractive interactions in order to
represent characteristic properties of the vWF. The behaviour of vWF is investigated under different conditions
including a freely-suspended polymer in shear flow and a polymer attached to a wall. We also examine the
migration of vWF to a wall (margination) depending on shear rate and volume fraction of red blood cells
(RBCs). Furthermore, the stretching of the vWF in flow direction depending on its radial position in a capillary
is monitored. Our results show that attractive interactions between monomer beads increase margination
efficiency and significantly affect the extension of vWF at different radial positions in blood vessels
