Herschel Bulkley Model Essay

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1. Introduction Fluids are around us everywhere. For example, fluids, which we exposed to it every day, like the air we breathe and the water we drink. These behave in a familiar way, taking the shape of their container and flowing easily. These fluids called the non-Newtonian fluids-This name backs to the physicist newton-. On the other hand, there is some fluids do not have the same properties which called the non-Newtonian fluid. This report defines the non-Newtonian fluids, the types of them, give some examples and talk about some of the application on them. 2. Definition Non-Newtonian fluids are fluids that do not obey the Newton law of viscosity. In these fluids the viscosity varies when shear rate varies in a non-linear way. …show more content…

Rheological mathematical models There are several rheological mathematical models applied on rheograms in order to transform them into information on fluid rheological behavior. For non-Newtonian fluids, the three models presented below are mostly applied (Seyssiecq & Ferasse, 2003). i. Herschel Bulkley model The Herschel Bulkley model is applied on fluids with a nonlinear behavior and yield stress. It is considered as a precise model since its equation has three adjustable parameters, providing data (Pevere & Guibaud, 2006). The Herschel Bulkley model is expressed in equation 5, where 0 represents the yield stress. τ = 0 +  *  n (5) The consistency index parameter () gives an idea of the viscosity of the fluid. However, to be able to compare -values for different fluids they should have similar flow behavior index (n). When the flow behavior index is close to 1 the fluid´s behavior tends to pass from a shear thinning to a shear thickening fluid. When n is above 1, the fluid acts as a shear thickening fluid. According to Seyssiecq and Ferasse (2003) equation 5 gives fluid behavior information as follows: 0 > 0 & n = 1  Bingham plastic behaviour 0 = 0 & n < 1  Pseudoplastic

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