the effect of vortex on head loss and pressure fluctuation along the penstock of hydroelectric power plant

Objective: this study aimed to assess the hydraulic impacts of intake vortices on energy losses and pressure fluctuations in hydropower penstocks and to evaluate the effectiveness of horizontal perforated anti-vortex plates in mitigating these effects. method: a large-scale laboratory model was used to systematically examine the influence of intake vortices under a wide range of hydraulic conditions. the experiments were conducted by varying the relative submergence depth (s/d = 1.5, 1.75, 2.0, 2.5, and 3.0) and the intake froude number (fr = 0.6, 0.8, 1.0, and 1.2) to generate different vortex strengths. hydraulic parameters, including relative total head loss, relative friction head loss, darcy–weisbach friction coefficient, and pressure fluctuations, were measured along the penstock. pressure fluctuations were recorded at nine measurement sections distributed along the penstock, and the hydraulic performance was compared for cases with and without the installation of an anti-vortex plate. results: the experimental results clearly demonstrated that the installation of an antivortex plate significantly reduced hydraulic losses and pressure fluctuations. on average, the friction coefficient, relative total head loss, and relative friction head loss were reduced to approximately 19.2%, 44.4%, and 20.8% of their corresponding values without the plate, respectively. increasing the submergence ratio led to a notable increase in relative friction head loss, while the friction coefficient decreased. for a fixed submergence depth, higher froude numbers intensified vortex strength, resulting in increased total and friction head losses as well as more pronounced pressure fluctuations along the penstock, despite a reduction in the friction coefficient. the dissipation length of vortices was found to depend strongly on vortex class, with weak class c vortices dissipating within approximately 7 diameters from the intake, class b vortices persisting up to about 18 diameters, and strong class a vortices showing no clear dissipation within the tested penstock length. conclusions: intake vortices have a substantial adverse effect on the hydraulic performance of hydropower penstocks by increasing energy losses and inducing pressure fluctuations. the results confirm that horizontal perforated anti-vortex plates are an effective and practical solution for mitigating vortex-induced losses and stabilizing flow conditions at intakes. furthermore, the findings highlight the critical role of submergence depth and intake froude number in controlling vortex strength and persistence. for strong air-core vortices, considerably longer penstocks or additional mitigation measures may be required to ensure complete vortex attenuation, underscoring the importance of vortex control in the design and operation of hydropower intakes.