A new model has been developed for describing the rheology of thixotropic fluids. The model accounts for hysteresis effects when the fluid goes through multiple shearing events. To demonstrate the model capability, a series of unsteady, three-dimensional simulations are presented for flow through a plain orifice passage. The thixotropic liquid simulation showed the behavior generally bounded by Newtonian and shear-thinning liquids limits. For high Reynolds number injection conditions, quasi-periodic behavior is noted as in prior studies with Newtonian and shear-thinning fluids. The effect of fluid rheology and response rates is also parametrically considered to demonstrate the role of the model parameters. (C) 2014 Elsevier Ltd. All rights reserved.