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Dimethyl ether (DME) is a green fuel that commercially produced in an adiabatic fixed bed reactor by methanol dehydration. In the present work, a shell and tube fixed bed reactor is modeled and optimized for DME production. The reactor is modeled based on mass and energy conservation equations as well as auxiliary equations. In order to estimate the DME production and temperature profile along the reactor, a one dimensional heterogeneous model consist of a set of nonlinear differential and algebraic equations has been solved numerically. Also, The DME production in the isothermal reactor is maximized by adjusting the optimal temperature distribution along the reactor using genetic algorithm. Then, the performance of the proposed isothermal reactor is compared with industrial adiabatic fixed bed reactor. Results showed the higher DME production rate and methanol conversion in the optimized reactor.

This article presents an investigation of water entry of two types of catamarans by smoothed particle hydrodynamics method. Constant velocity is considered for each model. For the first model, J3, water entry simulation of demi hull, wave-piercing hull and whole hull is performed. Pressure distribution and free surfaces of each test are presented. Comparison between pressure distribution of the whole hull and other parts shows a principal difference in flow regime around the bodies. Pressure coefficient of the whole body is larger than other body and has an increasing-decreasing behavior versus time. The second case study includes an INCAT model which is also simulated at a constant velocity. Pressure distribution of the INCAT model is compared against that of J3 model. Because of different geometries of the models, there are differences in their surrounding flow and pressure distributions. Mean pressure distribution and peak pressure of the J3 model are found to be greater than those of the INCAT model. Therefore, one may claim that a rounded corner body lick as INCAT model is perhaps better than a sharp body lick as J3 model.

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