Under the structure of the new power system,horizontal low-head tubular hydropower stations experience e-ven more severe variable load operation due to the combined effects of hydraulic impacts caused by frequent load chan-ges and unbalanced hydrodynamic factors induced by the gravity of water bodies.In order to enhance the dynamic per-formance of bulb tubular turbines during variable load conditions,numerical simulations were conducted to analyze the flow characteristics and vibration behavior within the turbine during load increase,considering the free surface and wa-ter body gravity,based on dynamic mesh technology.The results are as follows.Influenced by the free surface and wa-ter body gravity,the pressure distribution within the unit generally increases from the top to the bottom.During the load increase process,as the blade angle increases,the position of incoming flow impact shifts towards the suction sur-face,causing the low-pressure region at the head to gradually shift towards the pressure surface,and the area of the low-pressure region on the suction surface of the blade expands.The runner region becomes the primary vibration area of the tubular turbine due to the combined effect of 0.1fn low-frequency pressure pulsations originating from the tailrace and 3 fn high-frequency pressure pulsations induced by the rotation of the runner.
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