Generation and Propagation of Nonlinear Waves in a Towing Tank

Abstract

The paper presents the results of the research focused on linear and nonlinear wave generation and propagation in a deepwater towing tank equipped with a single flap-type wavemaker of variable draft. The problem of wave generation and propagation has been theoretically formulated and solved by applying an analytical method; linear and nonlinear solutions were obtained. The linear solution has been verified experimentally. The laboratory experiments confirmed that a linear model can be applied to predict the generation and propagation of water waves of low steepness. However, according to the analysis, the discrepancies between wave profiles predicted by applying the linear and nonlinear models rapidly increases with increasing wave steepness. Additionally, the secondary phenomena which occur in the towing tank, including: disintegration of wave profile, wave reflections from the beach and wave damping, were analyzed. Knowledge on the nonlinear processes and phenomena is essential for modeling the environmental conditions during tests carried out to secure the safety of the naval and offshore constructions. The theoretical formulation was derived and the solution was obtained by the Institute of Hydroengineering of the Polish Academy of Sciences IBW PAN while the experimental research was carried out in Ship Hydromechanics Division of the Ship Design and Research Centre CTO S.A.

Prediction of Ship Motions in Irregular Waves Based on Response Amplitude Operators Evaluated Experimentally in Noise Waves

“…The models were tested in different irregular waves representing the demanded sea states and appropriate noise wave realisation [15], [16]. One of the models was tested in regular waves.…”

“…The main source of errors in Type A uncertainty here is the deviation from approximated and measured RAO characteristics, thus the Type A uncertainty u A (Y φ ) is equal to root mean square error of approximation given by equation (16).…”

Fuzzy Control of Waves Generation in a Towing Tank

“…The more advanced techniques were also considered to simulate the generation of nonlinear waves numerically [23][24][25][26][27][28][29][30][31][32][33]. The complete nonlinear theory of the wave maker for the physical towing tank, up to now, is being developed and improved [34][35][36]. Thus, the linear wave maker theory, is validated to link the movements of the wave maker actuator with the profile of the low steepness waves, generated in the real towing tank.…”

“…The wave maker considered, is presented in Figure 2. On the basis of the transfer function derived, for the geometry of the flap-type wave maker [34], the z A is associated with the amplitude of the wave maker flap oscillations at the waterplane a as follows (2).…”

“…η p is a constant coefficient, specific for the facility considered, and is equal to 0.8 [34]. It reflects the efficiency of the mechanical energy transformation into the form of the progressive sinusoidal waves due to the pressure loss in the water gap between the walls of the towing tank and the flap of the wave maker.…”