Powder processing and manufacturing operations are rate processes for which the bottleneck is cohesive powder flow. Diversity of material properties, particulate form, and sensitivity to environmental conditions, such as humidity and tribo-electric charging, make its prediction very challenging. However, this is highly desirable particularly when addressing a powder material for which only a small quantity is available. Furthermore, in a number of applications powder flow testing at low stress levels is highly desirable.Characterisation of bulk powder failure for flow initiation (quasi-static) is well established. However, bulk flow parameters are all sensitive to strain rate with which the powder is sheared, but in contrast to quasi-static test methods, there is no shear cell for characterisation of the bulk parameters in the dynamic regime. There are only a handful of instruments available for powder rheometry, in which the bulk resistance to motion can be quantified as a function of the shear strain rate, but the challenge is relating the bulk behaviour to the physical and mechanical properties of constituting particles. A critique of the current state of the art in characterisation and analysis of cohesive powder flow is presented, addressing the effects of cohesion, strain rate, fluid medium drag and particle shape.

The initial aim of this study was to compare OpenFoam and Ansys Fluent in order to verify OpenFoam's Lagrangian Library and erosion capabilities. However, it was found that previous versions of Fluent have been providing wrong results for the discrete phase and the differences with the latest version (Ansys Fluent 15) are shown. A Submerged Jet Impingement Test is an effective method for studying erosion created by solid particles entrained in a liquid. When considering low particle concentrations a Lagrangian modeling of the particulate phase is a reasonable approach. Proper linkage between OpenFOAM's Lagrangian library and the solver PimpleFoam for incompressible transient flows allows two-phase simulations to be undertaken for comparison with Ansys Fluent with the aim of verifying OpenFoam's accuracy. Steady state convergence for the fluid flow is first accomplished and the results are compared, confirming a good agreement between the two packages. A transient simulation was then set up and spherical particles incorporated into the fluid flow. An assessment of the two codes' discrete phase models was carried out, focusing on the differences between impact angles and velocities yielded at the impingement plate's surface employing a similar strategy to that outlined first by Hattori et al [1] and later by Gnanavelu et al. in [2, 3]. In the comparison of OpenFoam with the latest version of Fluent, the main differences between the injection models are highlighted and the coupling possibilities between phases are taken into consideration. Agreement between trends for both impact angles and velocities is satisfactory when the last version of the commercial package is considered and the average discrepancy between numeric values is very low, verifying OpenFoam's Lagrangian library. Two different Jet Impingement Test configurations are also compared and the differences highlighted

Erosion induced by solid particle impingement is a very commonwear mechanism in turbomachinery and Computational Fluid Dynamics is one of the most widely used tools for its prediction. In this article, erosion is modeled in one of the channels of a centrifugal pump using OpenFOAM®,which is an Open Source CFD package. A review of some of the most commonly used erosion models is carried out in an Eulerian-Lagrangian frame along with a comparative study of the erosion rates obtained with each model. Results yielded some disparities between models due to the different factors taken into consideration. The mesh is then deformed to obtain the resulting eroded geometry