Energy transformation is crucial for sustainable development, with pumped storage playing a key role. Central to this system is the hydraulic turbine, necessitating innovation to overcome traditional issues like cavitation and vibration. This study proposes the traveling wave turbine, integrating a mechanism of traveling wave motion into a vertical rectangular flow channel. Gravitational potential energy of water flow propels the traveling wave plate and the traveling wave mechanism is elegantly modeled as a two-dimensional wave plate. Through numerical simulation, we explore the influence of peak of wave-channel clearance on traveling wave turbine performance. Results show that decreasing peak of wave-channel clearance coefficient enhances time-averaged efficiency, reduces volume loss coefficient, and weakens fluctuations in instantaneous mass flow and power coefficients. High sensitivity to peak of wave-channel clearance changes is observed under a high head condition. Reduction in peak of wave-channel clearance decreases pressure difference between front and rear of the traveling wave plate at t/T = 0 and increases it at t/T = 0.25. Simultaneously, decreasing clearance coefficient leads to reduced fluid velocity at the contraction point, causing a noticeable decrease in vortex scale and intensity.