Transport and waves in parametrically excited fluid layers

The transport and waves in parametrically excited fluid layers play a significant role in an understanding of non-linear surface wave phenomena and tidal resonances. In this thesis, we study resonant waves occurring in a circular channel with various obstacles under external oscillatory excitation. Typically, such sloshing experiments are conducted in rectangular, straight channels. The external excitation is implemented using a rotating table on which the entire experiment, including measurement equipment, is mounted. The excitation is either sinusoidal or ratched motion. The obstacles include a fully blocking barrier and a symmetric or asymmetric hill. The channel circumference is 4.76 m, with water depths ranging from 2 cm to 6 cm. Wave displacements within the channel are measured using 17 ultrasonic sensors equidistantly distributed along half of the channel. Particle Image Velocimetry (PIV) is employed to measure the flow. We also consider a simplified numerical model capable of reproducing the experimental results. This model is based on a long-wave approximation and vertical integration using a profile function (Kármán-Pohlhausen approach). Additionally, we use a wave attractor model to quantitatively explain the development of resonances. These resonances are distributed in bands of the excitation frequency around the linear eigenfrequency. The experimental wave attractor and numerical results are consistent with each other. The waves observed within these resonant frequency bands appear as undular bores or solitary waves. In the fully blocking case, bands of constructive and destructive interference are observed, while in the presence of hills, all eigenfrequencies exhibit resonances of varying intensity. These non-linear wave phenomena are characterized by strong transport properties, which can be studied here due to the fact that the circular channel is not fully blocked. The ratched excitation generated asymmetric wave fields, which also induced asymmetric transport in the channel, leading to the emergence of a mean flow in the channel. A similar mean channel flow is observed for the asymmetric hill; however, wave-induced transport played a lesser role in this case. This is attributed to a large separation vortex on the steep side of the hill, which created a valve effect that rectified part of the oscillatory flow. These results are of interest not only for engineering applications but also for the understanding of tidal flows over seabed topography.