· · · Repository Hydraulic Engineering Reports

Adaptation of COBRAS VOF model for typical breakwater applications and worked out examples of water movement in and around breakwater cross sections.

Experimental research to the influence of the air pressure on the impact pressure cause by breaking waves. The research shows that there are three factors which load the structure during the breaking of waves: the water layer over the structure, the shock due to the impact of the water jet from breaking and the air pocket entrapped in the water mass. The influence of all of the factors is determined.

Shock pressures of high intensity and short duration may occur during breaking of waves on coastal structures, slamming of ships, landing of seaplanes, and water entry of naval projectiles with flat nose. The phenomenon of shock pressures resulting from the impact between a solid and a liquid can better be described as a water hammer phenomenon wherein the elasticity of the solid and the compressibility of the liquid are the governing factors. The water hammer theory predicts the extreme values of shock pressures since it neglects the effect of air that might be entrapped between the solid an the liquid at the moment of impact. Analytical formulations of shock pressures as a water hammer phenomenon and as the compression of a thin layer of air entrapped between the solid and the liquid at the moment of impact are presented in this report. Tests were conducted by dropping a steel, aluminum or plastic plate whose edge was hinged at the water surface into a 3- by 3- by 6-ft steel tank that was partially filled with water. The shock pressures were measured at two locations by means of strain gage and piezoelectric type pressure cells mounted in the plate with special adapters. The ratio between the recorded and theoretical pressures when treated statistically was found to fit the Poisson distribution well. Correlation between the recorded pressures and the shape of the surface of contact between the solid and the liquid at the moment of impact indicated that although shock pressures have a great intensity, they have a short duration and occur only at some spots on the surface of the solid. Therefore (a) they should not be applied as static pressure for checking the stability of the coastal structure as a whole, (b) they may be absorbed by flexible structures, (c) they may cause cracks in rigid structures such as steel caissons filled with rock, and (d) they may affect the stability of structures that have natural frequencies within the range of duration of shock pressures. Equations and diagrams for the prediction of the magnitude and duration of shock pressures resulting from the impact between a solid and a liquid are presented herein.

Description of a VOF model for wave structure interaction (VOF-break). Example calculations for the Zeebrugge breakwater, including prototype measurements of wave penetration into the core of the breakwater. Description of breaking processes on the breakwater.

Ten behoeve van het ontwerp van zeewerende constructies van nieuwe landaanwinningswerken van de Maasvlakte 2 is onderzoek verricht naar onzekerheden in de bepaling van golfrandvoorwaarden onder ontwerpcondities. In dit deelrapport is gekeken naar het effect van stromingen op de golfcondities voor de zeewerende constructies. Hierbij is gebruik gemaakt van bestaande resultaten van stromingsberekeningen onder gemiddelde springtij situaties. Vervolgens zijn een aantal golfberekeningen uitgevoerd met het SWAN model om het effect van stromingen op de golfcondities te bepalen. Tevens is een stappenplan opgesteld voor het uitvoeren van SWAN berekeningen voor ontwerpcondities.