Thesis (M. Eng.)--Carleton University, 1988. / Also available in electronic format on the Internet.

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 85-86). Also available on the World Wide Web.

The waves produced by a flap-type wavemaker, hinged in the middle, are modelled using first-order linear wavemaker theory. A simplified closed-loop, discrete-time system is proposed. This includes a proportional plus integral plus derivative (PID) controller, and the wavemaker in order to compare the actual wave spectral density with the desired wave spectral density at a single frequency. Conventional discrete-time control theory is used with the major difference being the use of a relatively long timestep duration between changes in waveboard motion. The system response is calculated for many controller gain combinations by the computer simulation program CBGANES. System stability is analyzed for the gain combinations by using two different methods. One method is an extension of the Routh criterion to discrete-time and the other is a state-space eigenvalue approach. The computer simulation and the stability analysis provide a means for selecting possible controller gains for use at a specific frequency in an actual wave tank experiment. The computer simulation performance response and the two stability analyses predict the same results for varying controller gains. It is evident that integral control is essential in order to achieve a desired response for this long duration timestep application. The variation in discrete timestep duration and in desired spectral density (an indirect indication of frequency variation) provide variation in the constraints on controller gain selection. The controller gain combinations yielding the fastest stable response at a single frequency are for large proportional gain and small integral and derivative gains. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

The goal of this research is to develop an equation describing the two, dimensional motion of an inviscid incompressible fluid in the rectangular wavemaker of constant depth. The boundary value problem of the rectangle is transformed to the upper half plane with the use of Jacobian elliptical functions. The boundary value problem is then transformed to the unit disc. The solution to the mixed value problem of the disc is found using a general solution satisfying the Laplace equation in polar coordinates. In order to solve the coefficients of the general solution, a system of equations is developed using a method similar to the one applied for the coefficients of a Fourier series. The system is converted to matrix form and the coefficients are calculated using Mathematica. Four approximate solutions are calculated for depths of 3.96 m and 4.42 m with N equal to 2 and 10. / Graduation date: 1993

The circular wave basin provides a means of physically modeling the nearshore without the typical problems associated with end walls. Three different coastal processes were examined to demonstrate the use of a spiral wavemaker in a circular wave basin. These were longshore currents, shear waves, and groin circulation. A beach was designed and constructed to concentrate breaking in a narrow region and minimize wave reflection. Currents in the longshore direction were generated by both the motion of the wavemaker and oblique wave approach. Two methods for measuring nearshore currents were employed. First, a 3-D acoustic current meter was positioned at various locations in the cross shore and the local radial and tangential velocities were recorded. Second, a video camera was placed approximately 8 meters above the wave basin to record the motion of a ball in the nearshore. The video tape was digitized by an image processor and the motion of the ball was determined. Measurements of nearshore circulation in the circular wave basin were used to investigate longshore currents, shear waves, and groin circulation. Average measured longshore current profiles in the cross shore were compared with numerical model predictions. An analysis of the existence of shear waves in the circular wave basin was performed by calculating longshore and cross shore current spectra. Particular attention was focused on the low frequency end of the spectra where shear waves are most energetic. Model groins were placed in the circular wave basin and measured currents were compared to predicted circulation patterns. All three applications indicated that the circular wave basin is a useful device for simulating coastal processes in a laboratory environment. / Graduation date: 1992

Thesis (Ph. D.)--Joint Program in Applied Ocean Physics and Engineering (Massachusetts Institute of Technology, Dept. of Ocean Engineering and the Woods Hole Oceanographic Institution), 2001. / Includes bibliographical references (leaves 149-155). / This thesis takes a look at the near boundary flow about fish-like swimming bodies. Experiments were performed up to Reynolds number 106 using laser Doppler velocimetry and particle imaging techniques. The turbulence in the boundary layer of a waving mat and swimming robotic fish were investigated. How the undulating motion of the boundary controls both the turbulence production and the boundary layer development is of great interest. Unsteady motions have been shown effective in controlling flow. Tokumaru and Dimotakis (1991) demonstrated the control of vortex shedding, and thus the drag on a bluff body, through rotary oscillation of the body at certain frequencies. Similar results of flow control have been seen in fish-like swimming motions. Taneda and Tomonari (1974) illustrated that, for phase speeds greater than free stream velocity, traveling wave motion of a boundary tends to retard separation and reduce near-wall turbulence. In order to perform experiments on a two-dimensional waving plate, an apparatus was designed to be used in the MIT Propeller tunnel, a recirculating water tunnel. It is an eight-link piston driven mechanism that is attached to a neoprene mat in order to create a traveling wave motion down the mat. A correlation between this problem and that of a swimming fish is addressed herein, using visualization results obtained from a study of the MIT RoboTuna. The study of the MIT RoboTuna and a two-dimensional representation of the backbone of the robotic swimming fish was performed to further asses the implications of such motion on drag reduction. PIV experiments with the MIT RoboTuna indicate a laminarisation of the near boundary flow for swimming cases compared with non-swimming cases along the robot body. Laser Doppler Velocimetry (LDV) and PIV experiments were performed. / (cont.) LDV results show the reduction of turbulence intensity, near the waving boundary, for increasing phase speed up to 1.2 m/s after which the intensities begin to increase again through Cp = 2.0 where numerical simulations by Zhang (2000) showed separation reappearing on the back of the crests. Velocity profiles who an acceleration of the fluid beyond the inflow speed at the crest region increases with increased phase speed and no separation was present in the trough for the moving wall. The experimental techniques used are also discussed as they are applied in these experiments. / by Alexandra Hughes Techet. / Ph.D.