Abstract: To meet the requirement of trajectory nappe in the flood release tunnel 2^# in Changheba hydropower station, we designed a new-type bucket combing narrow slit and swallow-tail by physical model. The characteristics of slit-type bucket and swallow-tail bucket were comprehensively considered. The flow pattern in bucket, water jet, and energy dissipation and erosion control in the downstream of these three bucket types were compared. Results suggest that this new-type bucket has the advantages of both swallow-tail bucket and slit-type bucket. It improves the flow pattern in bucket, and optimizes water jets form and alleviates downstream scouring. Besides, it adapts to the requirement of trajectory nappe in the flood release tunnel 2^#. The research result could be a reference for similar projects.

Key words: flood release tunnel, swallow-tail bucket, slit-type bucket, combined bucket, energy dissipation