Fluid flow occurring in a venturi tube was numerically simulated with the Fluent software, and several factors to affect the mass flux and an asymmetric flow were analyzed, including the contraction ratio, ratio of the throat section length to diameter, the diffusion angle and the inlet and outlet pressure difference. Results show that the minimum pressure point occurs at the intersection between the contraction and throat sections in the venturi tube. As the contraction ratio increases, vacuum degree ascends, and mass flux rises. While both vacuum degree and mass flux reduces as the diffusion angle increases. In addition, an increment in the contraction ratio shortens a fully developed section of velocity in the diffusion section. At the contraction ratio less than 0.2 or the diffusion angle less than 35°, velocity in the diffusion section shows an asymmetric and skewed flow. However, as the inlet and outlet pressure difference increases, mass flux goes up, and thereby occurring a back-flowing in the throat section. The calculated results were compared with the reference’s data, both error is within 0.5% – -28%.
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