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To study the effect of the width-to-narrow ratio on the forward and reverse flow characteristics of the Tesla valve, five different models of the Tesla valve with different width-to-narrow ratios are established in this paper. The numerical calculations of forward and reverse flow under different working conditions are carried out by the CFD method in the laminar flow regime, and the reliability of the numerical calculation method is verified by comparing it with the experimental results. The results show that: in forward flow, the main flow-through channel is not related to the width-to-narrow ratio, the flow rate of the straight channel increases with the increase of the width-to-narrow ratio, and the static pressure in the diversion section is in the shape of "∞"; while in reverse flow, the main flow-through channel is weakly related to the width-to-narrow ratio, the flow rate of the arc channel is not increased with the increase of the width-to-narrow ratio, and the static pressure in the diversion section is in the shape of "bench". As the width-to-narrow ratio decreases, the pressure drop during forward and reverse flow becomes more significant. [ABSTRACT FROM AUTHOR]

In order to reveal the influence of starting acceleration on starting process of a pump as turbine system, this paper carries out a numerical calculation of the three-dimensional viscous unsteady flow of pump as turbine circulating piping system under three starting acceleration conditions, and obtains the external and internal flow characteristics of each overflow component during the starting process, and also analyzes the energy loss of each component in the piping system in depth with the help of entropy production method and Q criterion method. The results show that during system start-up, the flow rate and outlet static pressure curves of the pump as turbine are hysteresis relative to the rotational speed, the head curve is similar to a linear rise during slow and medium speed start-up, while it shows a parabolic rise during rapid start-up, the entropy production and vorticity in the impeller domain of the pump as turbine are mainly distributed between the blades, and the distribution decreases during start-up. In addition, the pump similarity law does not apply to the performance prediction during the transient start of the pump as turbine. [ABSTRACT FROM AUTHOR]