Abstract

The paper presents comparative analysis of unsteady pre§sure course calculation in closed conduits using selected hydraulic resistance models incorporating quasi-steady and unsteady friction models. Calculation was carried out for larninar and turbulent initial flows as tested by I B. L. Holmboe and W. T. Rouleau. The results enabled qualitative and quantitative assessment of methods used to calculate friction losses. The assessment has confirmed that the commonly applied method of hydraulic resistance calculation (compatible with the quasi-steady flow hypothesis) does not guarantee satisfactory agreement between calculated and recorded hydraulic transients. It has been proven that the unsteady friction models based on weighting function of past flow velocity changes show superiority over models based on assumption that the portion of energy losses related to flow unsteadiness is proportional to the first derivative of liquid velocity.