M. Salih Kirkgöz

An experimental investigation of a vertical wall response to breaking wave impact

Abstract Laboratory experiments are conducted to measure the impact pressures and resulting deflections from breaking oscillatory waves on a vertical wall with 1/10 foreshore slope. The maximum impact pressure data on the wall are statistically analysed and the relationships between the magnitudes of impact pressures and forces, and their durations, are investigated. The maximum impact pressures, among the 90 wave impacts, are found to vary between 1.37 × 10 4 and 28.3 × 10 4 Pa . The maximum impact pressures are shown to reasonably satisfy the log-normal probability distribution and they occur most frequently slightly below the still-water level. The greatest wall deflection at the point of measurement is caused by an impact which has a maximum pressure of 3.6 × 10 4 Pa , corresponding to 50% probability in the log-normal distribution. It is found that the longer-lasting low impact forces are more effective in producing the larger wall deflections. In this respect, the maximum impact pressures in the range between 2.5 × 10 4 and 5 × 10 4 Pa obtained in this study are found to be the most effective. The upper limit of this range (when non-dimensionalised by the specific weight of water and deep-water wave steepness) is suggested as a design value for vertical walls.

Impact pressure of breaking waves on vertical and sloping walls

Abstract Laboratory tests are conducted to measure the impact pressures of breaking waves on vertical, 5° forward, and 5, 10, 20, 30, and 45° backward sloping walls. The base structure of the wall has a foreshore slope of 1 10 . Regular waves are used throughout the experiments for all wall angles. The maximum impact pressures on the wall are shown to satisfy the log-normal probability distribution. It is found from the present experiments that the impact pressures and resulting forces on sloping walls can be greater than those on a vertical wall. On the seven different walls tested, the maximum impact pressures occur most frequently slightly below the still-water level. The pattern of the impact pressure history does not change with the slope of the wall, and as the probability of maximum impact pressure decreases, the pressures around the peak pressure region of the impact pressure histories remain longer.

Influence of water depth on the breaking wave impact on vertical and sloping walls

Abstract Experimental data are presented for the impact pressures, impact forces and deflections from oscillatory waves breaking (by plunging) directly on vertical, 10° and 30° backward inclined walls with 1 10 foreshore slope. The influence of the water depth on the maximum impact pressure, maximum impact force and maximum wall deflection is examined and it can be seen that these three quantities reasonably satisfy the log-normal probability distribution for the different water depths. It is also found that, overall, the magnitudes of the maximum impact pressure, maximum impact force and maximum wall deflection decrease rapidly as the water depth in front of the wall becomes smaller or greater than the depth in which impinging of the breaker front is presumed to occur almost with a parallel face to the wall during the wave breaking process. Within the range of present water depth conditions, the most frequent location of the maximum impact pressure for the three walls remains almost at the still-water level. Based on a wall deflection criterion, a range of water depth is determined where the wave breaking is likely to cause serious consequences on the wall.

Experimental and theoretical analyses of two-dimensional flows upstream of broad-crested weirs

Using the particle image velocimetry (PIV) technique, the laboratory experiments are conducted to measure the velocity fields of two-dimensional turbulent free surface flows upstream of rectangular and triangular broad-crested weirs. The experimental flow cases are analyzed theoretically by a computational fluid dynamics (CFD) modeling in which the finite element method is used to solve the governing equations. In the CFD simulation, the volume of fluid (VOF) method is used to compute the free surfaces of the flows. Using the standard k–e and standard k–ω turbulence models, the numerical results for the velocity fields and flow profiles are compared with the experimental results for validation purposes. The computed results using k–ω turbulence model on compressed mesh systems are found in good agreement with measured data. The flow cases are also analyzed theoretically using the potential flow (PF) approach, and the numerical results for the velocity fields are compared with measurements.

Design of a caisson plate under wave impact

Abstract From the laboratory experiments and field studies it has been shown that when a wave breaks directly on a vertical wall, impact pressures of high magnitude and short duration, are produced. Despite the recent advances made in collecting data on impact pressure histories and their spatial distributions, analyses on the structural behaviour of the walls loaded by the impact forces do not seem adequate. In the present study the theoretical analysis of the response characteristics of a caisson plate, having different aspect ratios, under the wave impact loading is investigated. Numerical results for the dynamic values of moments and transverse displacements are obtained by the method of finite elements. Some prerequisite experimental data for wave breaking and resulting impact pressures are provided. The static results for moments and deflections are also computed for comparing them with the dynamic values. The dynamic results are found significantly greater than the static values. The ratio between the dynamic and static values is called “Dynamic magnification factor” that varies with plate aspect ratio. Based on this factor a procedure is proposed which may have practical consequences in the design of caisson plates.

Experimental and Numerical Modeling of Flow over a Spillway

In this study, the experimental data for two different flow rates collected earlier from a laboratory spillway model were used for the validation of the numerical results obtained for the same conditions. The governing equations of flow interacting with the spillway model were solved with finite volume method based on ANSYS-Fluent software package. In order to obtain grid independent numerical solutions, three different concentrations of grids (coarse, medium and fine) were designed and the suitability of the fine grid was tested with Grid Convergence Index (GCI) method. Six turbulence closure models namely; Standard k- (SKE), Renormalization-Group k- (RNG), Realizable k- (RKE), Modified k- (MKW), Shear Stress Transport (SST) and Reynolds Stress Model (RSM) were used for the numerical solution of the velocity field. For the calculation of water surface profile Volume of Fluid Method (VOF) was used. The free surface profiles and velocity field obtained from the numerical simulations were compared with measured values, and the success of the chosen turbulence closure models were discussed.