The flow over cavities can produce complex unsteady flowfields that are an important practical concern in aerospace applications. Understanding the flow field in the cavity can help to determine the driving mechanism of the oscillations... more
The flow over cavities can produce complex unsteady flowfields that are an important practical concern in aerospace applications. Understanding the flow field in the cavity can help to determine the driving mechanism of the oscillations to create effective control methods to avoid structural damage. In this study, both two and three dimensional time-dependent Reynolds-Averaged Navier-Stokes simulations are performed for the flow over an open cavity to demonstrate the capability of computational fluid dynamics to accurately predict the supersonic flow field inside a cavity and to assess the adequacy of two dimensional simulations in capturing cavity flow physics accurately. In this particular problem of a supersonic flow over a cavity, the three-dimensional effects cannot be neglected. A two-dimensional simulation would give an insight about the longitudinal mode of the cavity flow without any three-dimensional effects, but it is not enough to understand the real physics of the problem.
The cavitation is an inevitable factor in pumps used in the whole industry, which is a major cause of energy loss and mechanical breakdown. In this study, the cavitation phenomena at the design flow rate were numerically analyzed for two... more
The cavitation is an inevitable factor in pumps used in the whole industry, which is a major cause of energy loss and mechanical breakdown. In this study, the cavitation phenomena at the design flow rate were numerically analyzed for two pumps with different incidence angles. The design flow rate for both models was located near the best efficiency point (BEP). The incidence angle was determined with the impeller inlet diameter and the blade angle. A pump with a smaller incidence angle consistently showed a stable flow pattern as the inlet pressure decreased, whereas a pump with a larger incidence angle contained non-uniform flow streamlines despite a very small amount of the generated cavities. The flow pattern at the impeller inlet was handled by the shape and thickness of the generated cavities which could act as an additional blockage in the pumps. The inception and growth of the cavity with a decrease of inlet pressure were also inferred, which was specifically quantified as the blockage ratio. A pump with a larger incidence angle performed poor cavitation characteristics and obtained the pressure fluctuation and cavity oscillation. The magnitude of pressure fluctuation was indicated using the fast Fourier transform (FFT) analysis. The experimental tests were performed on both pumps to validate the numerical results.
