The spiral concentrator has been extensively used in the industry for decades. Gaps, however, appear to remain in understanding and explaining its unique flow pattern. Spiral is marked by the existence of high shear rate. Gravity, drag, frictional force between particles and trough, centrifugal force and lift force act in a particular manner to generate a unique flow pattern called secondary circulation. The present work attempts to explain how geometrical features and different forces help in generation of secondary circulation in pure fluid. A new concept of force 'balance from classical solid mechanics has been introduced to explain the generation of secondary flow and behavior of particles on the spiral trough. A modified form of Bagnold force equation has been presented along with simulation results. (C) 2016 Elsevier B.V. All rights reserved.