A one-dimensional (1D) system and three-dimensional (3D) component cosimulation method based on the method of characteristic (MOC) and computational fluid dynamics (CFD) was proposed to study the interaction between valve-induced water hammer and pump during the rapid closing of the valve. In a long pipeline system, the pump was treated as a 3D CFD model using Fluent code, whereas the remaining system models (e.g., pipe, valve) were represented by 1D components using MOC. The numerical coupling and integration of both models were realized by a coupled code written using Visual Basic. The coupling theory and procedure were described in detail. MOC-CFD steady coupling in the case of the fully open state of the valve was first conducted. The corresponding results showed that the steady cosimulation can accurately determine the operating conditions. A transient cosimulation for the rapid closing procedure of the valve was conducted to study the interaction. The relative dynamic behavior obtained by MOC-CFD cosimulation was compared with that using MOC calculation alone. Transient simulation demonstrated that MOC-CFD coupling analysis was closer to real conditions because of considering the effect of fluid inertia. The effect was further explained through a comparison of internal and external characteristics between the transient and quasi-steady assumptions.

In this study, three impellers with different blade pressure side (PS) profiles are designed and the influence on the hydraulic and dynamic performance of a low specific speed centrifugal pump is investigated by numerical simulation and experimental research. The results show that blade PS modification introduced in this study can efficiently alleviate the unsteady pressure pulsation of model pump. In order to study the effects of blade modification on the internal flow filed, the volute domain is replaced by an even outlet region for computational fluid dynamic (CFD) analysis. Relative velocity distribution is extracted to visualize the three-dimensional (3D) flow characteristics at the impeller outlet. Results show that the flow at impeller outlet presents a typical jet–wake structure, which is significantly suppressed after the blade modification. The suppression of jet–wake structure, which is attributed to the redistribution of pressure and velocity in the impeller caused by the change of blade work capacity, can directly reduce the intensity of pressure pulsation in the volute by increasing the velocity uniformity at impeller outlet. Given that the existence of jet–wake flow results in large mixing loss and velocity deviation at the impeller outlet, entropy generation rate and slip velocity calculation are introduced here to measure the extent of jet–wake configuration. Results show that both indicators introduced here can be used to quantify the extent of the jet–wake structure at impeller outlet, and thus, indirectly predict the strength of unsteady pressure pulsation in pump volute.

The startup period, one of several transient operations in a centrifugal pump, takes note of some problems with these devices. Sometimes a transient high pressure and high flow rate over a very short period of time are required at the startup process. The pump^’s dynamic response is delayed because of the rotational inertia of the pump and motor. Our research focuses on how to get a large flow in a short time when the pump cannot meet the requirements alone without a large power driver. To achieve a strong response in the startup process, a ball valve is installed downstream of the pump. The pump^’s transient behavior during such transient operations is important and requires investigation. In this study, the external transient hydrodynamic performance and the internal flow of the pump during the transient startup period are studied by experiments and simulations. In order to find an appropriate matching method, different experiments were designed. The content and results of this paper are meaningful for performance prediction during the transient pump-valve startup period.