Nonlocal flow behavior of microstructured fluids – application to the Poiseuille geometry A. Perrot, N. Challamel, V. Picandet Laboratoire d’Ingénierie des MATériaux de Bretagne, (LIMATB) Université de Bretagne Sud – Université Européenne de Bretagne Centre de Recherche de Saint-Maudé, BP 92116, 56321 Lorient, Cedex, France 1 Introduction It is now well accepted in solid mechanics that the microstructure nature of the material at the microscale may be the source of enriched macroscopic constitutive laws at the macroscale [1- 3]. Two families of constitutive laws are generally distinguished, namely nonlocal integral- based constitutive laws, and gradient constitutive laws [4, 5]. Recently in the field of research applied to the complex rheological modeling, some spatial nonlocal concepts have been also introduced to explain the flow cooperativity phenomenon [6-8]. The nonlocal aspect of the material parameters has been introduced through a cooperativity length scale. The cooperativity length scale is used to compute a nonlocal viscosity parameter. It can be shown that such a model is in fact equivalent to the consideration of a non-homogeneous viscosity parameter through the flow. Bingham or Herschel-Bulkley models are simple models able to provide a correct description of the flow behaviour of industrial pastes such as concrete, foam, ceramics… They are used to model the dependence of the shear stress on the shear rate. However, those models fail to describe local behaviour or phenomenon including shear banding, spatial cooperativity or scaling and wall effects. For example, the examination of the flow properties of highly concentrated suspensions such as concrete provides geometry dependent results [9, 10]. Also, the gap dependency can be associated to scaling effect linked to the ratio of the maximal particle diameter (or fiber length) and gap size. Then, it is considered than the gap size of a rheometer device must be ten times the maximal particle diameter in order to achieve