Numerical methodology for the CFD simulation of diaphragm volumetric pumps

Abstract

This paper presents the unsteady numerical methodology for the CFD simulation of Air-Operated Diaphragm Pumps. The model reproduces the unsteady displacement of the diaphragm using dynamic mesh techniques and fully resolves the Fluid Structure Interaction (FSI) responsible for the motion of the check valves. The governing parameters have been modified with User Defined Functions (UDFs), using an implicit scheme for the grid motion that guarantees the stability and realizability of the twodimensional model adopted. The analysis of the instantaneous delivered flow rate, as a function of the discharged outlet pressure, has provided interesting and useful information for the future design of new prototypes. The comparison between numerical results and the experimental performance curves has confirmed the accuracy of the model and the correct mesh selection in the small gaps and passages of the pump internal geometry. The leakage flows, especially in the exhausting valve during the forward stroke, and the ball tapping responsible for instabilities and high-frequency noise during oscillations of the valves has been accurately simulated. At high-delivered pressures, it has been observed a characteristic ripple in the instantaneous flow rate during the deceleration of the diaphragm towards its top-dead-center, associated to a partial reopening of the exhausting valve. A closer look to the dynamics of the balls has revealed a strong coupling between inlet and outlet check valves. In addition, despite of the remarkable level of accuracy (less than 9% of deviation), the recirculating cells found in the flow fields inside the pump suggest the convenience of the development of a full-unsteady 3D model in the near future.

Multiobjective optimization of a tubular pump to improve the applicable operating head and hydraulic performance

“…Different computational domain grids were generated for different grid sizes to reduce the computational time. 32 For most of the first cells near the wall, the y+ values were in the variation of 30 to 200 to ensure correct utilization of the model. The element types were tetrahedron and hexahedron.…”

Influence of Impeller Speed Patterns on Hemodynamic Characteristics and Hemolysis of the Blood Pump

“…The pressure difference between the inlet and the outlet of the blood pump at a specific speed and a flow rate was obtained, and the H-Q curve of the blood pump was drawn. CFD is an effective method to obtain the hydrodynamic characteristics of blood pumps and the cardiovascular system [17,18]. Blood is considered as a Newtonian fluid in large vessels where the shear strain is high; in the present study, blood was basically simplified to a Newtonian fluid for modeling, simulation, and experimental research [6,19].…”

Diagnostics for Periodically Excited Actuators

“…Diaphragm pumps also exhibit significant failure mechanisms. Two main challenges reported in the literature include diaphragm rupture and check valve failure [15], [16]. These two phenomena are related.…”

“…There are relatively few publications that examine the analytical description of diaphragm pump operation and associated degradation in practical environments [15], [17], e.g., in comparison to centrifugal pumps. Moreover, few references deal with diagnostics and condition monitoring of these positive displacement devices [18], [19], [20].…”