Optimal contract wall for desired orientation of fibers and its effect on flow behavior

The orientation of suspended fibers in the turbulent contraction is strongly related to the contraction ratio, which in some cases may be detrimental to the actual production. Here for a certain contraction ratio, the contraction geometry shape is optimized to obtain the desired fiber orientation. In view of the nonlinearity and the complexity of the turbulent flow equations, the parameterized shape curve, the dynamic mesh and a quasi-static assumption are used to model the contraction with the variable boundary and to search the optimal solution. Furthermore the Reynolds stress model and the fiber orientation distribution function are solved for various wall shapes. The fiber orientation alignment at the outlet is taken as the optimization objective. Finally the effect of the wall shape on the flow mechanism is discussed in detail.