Professor Arnold is nationally and internationally recognised as an authority in both powder technology and bulk solids handling.

His research is so highly regarded scientifically, that he has been awarded the DSc degree, the only engineer so recognised at Wollongong.

His work is particularly noteworthy in pneumatic conveying; he and his colleagues have made significant advances in long distance conveying at low velocities. This has enabled the handling of fragile food (e.g. "rice bubbles") with greatly reduced product damage and therefore enhanced overall recoveries and efficiency.

Professor Arnold is widely consulted in mining, agriculture, chemical and food industries.