Preface

Flow behaviour of powders is a complex field whose importance is often overlooked – in contrast, fluid flow behaviour is rigorously described in most engineering education programmes. However, powders are present at multiple stages of the majority of production processes, and represent a significant portion of industrial and consumer products.

Research has been active on the topic of powder handling and characterisation of powder flow since 1960. It has attracted more attention in recent years as novel formulated and functional products have been developed in powder forms, particularly in pharmaceutical and high value additive manufacturing industries. Additionally, some flow characterisation techniques have been found to be unreliable in describing powder behaviour under a wide range of processing conditions, such as under low stress or at high strain rate. As a result, extensive research has been carried out in the past decade, but the work has not been fully documented in the form of a book. It was therefore felt quite timely to write a book in this context that is based on research led topics and content.

This book starts by describing the important particle properties that influence flow behaviour, and comprehensively outlines the established theories that describe it. The flow behaviour of a given powder may differ drastically when exposed to varying conditions of stress, strain rate and environment, all of which are thoroughly considered in this book. This dependency of powder flow behaviour on processing conditions has led to the development of a significant number of devices to characterise powder flow. This book outlines the method, the property measured and the suitability of each of these testers; from the most established and quantitatively robust techniques to the fast and simple approaches, to the less familiar and recently developed devices. The discussion of the individual assessment methods is complimented by industrial case studies that demonstrate real powder flow problems experienced in practice, and highlights the measurements that can explain and identify the root causes and possible solutions. Furthermore, this book describes the most common approaches for simulating powder flow; a field with increasing importance in understanding how measurements may relate to process behaviour, and the influence of individual particle properties.

This book would not have been possible without the dedication and technical insight of the subject matter experts that authored the individual chapters. Professor Alain De Ryck must be commended for his excellent contribution and his willingness to adapt this to suit the whims of the editorial team. Professors Massimo Poletto, Diego Barletta and Andrea Santomaso handled the challenging task of categorising and describing each individual powder flow tester with aplomb. Professor Charly Wu and Drs Yu Guo, Chunlei Pei, Alexander Krok and Ling Zhang expertly put together a thorough description and critique of the modelling techniques available for describing powder flow. Drs Vincenzino Vivacqua, Giuseppe Raso and Michele Marigo were instrumental in identifying suitable industrial examples of powder flow challenges faced by industry, and the appropriate measurements made to overcome these problems, which provides an extra dimension to this book. Finally, sincere thanks go to Drs Mohammedreza Alizadeh Behrani and Umair Zafar for their tireless efforts and key contributions, delivered in a timely fashion.

We hope you find this book to be an interesting and useful resource, whether you are already knowledgeable in the subject, or just embarking on the sticky journey of powder flow!

Ali Hassanpour

Colin Hare

Massih Pasha