Author(s): Mohamed S. Ghidaoui; Sameh G. S. Mansour
Linked Author(s): Mohamed S. Ghidaoui
Keywords: No Keywords
Abstract: Practical applications such as the design of pipeline systems, the study of water quality in closed conduits and the application of transients for inexpensive, wide-coverage data collection require efficient mathematical models that are capable of accurately solving water-hammer problems beyond the first wave cycle. In this paper, the two most promising unsteady shear stress models, namely the instantaneous acceleration (IA) model and the Vardy-Brown (VB) convolution integral model, are investigated. The VB model is physically based and does not contain free parameters (i.e., applicable in the absence of data). Computations show that the VB model produces results that are, generally, in good agreement with laboratory data. In the case where good quantitative agreement between the VB model and data could not be achieved, it is found that this lack of agreement is due to the failure of the flow axisymmetry assumption and not the VB model. The IA model lacks physical basis and contains a free parameter that needs to be determined from data fitting. The value of this parameter is highly dependent on the flow conditions. Therefore, in the absence of elaborate and detailed data, the authors recommend that the IA model be abandoned in favor of the VB model.