Understanding wave impact pressure is important in the design of coastal and offshore structures. This is especially important when the structures are under green water loading during an extreme wave event. Both numerical and experimental studies have been conducted to investigate the magnitude and cause of the huge impact pressures exerted on the structures. Green water impact pressure due to plunging breaking waves impinging on a simplified, three-dimensional model structure was investigated in the laboratory. Two breaking wave conditions were tested: one with waves impinging on the vertical wall of the model at the still water level and the other with waves impinging on the horizontal deck surface. Pressure measurements were taken at locations in two vertical planes on the deck surface with one at centerline of deck and the other between the centerline and an edge. Impact pressure was found to be quite different between the two wave conditions even though the incoming waves are essentially identical. Two types of pressure variations were observed-impulsive type and non-impulsive type. Much higher pressure was observed for the deck impingement wave condition, even though the flow velocities were quite close. Void fraction was also measured at selected points. Impact pressure was correlated with the mean kinetic energy calculated based on the measured mean velocities and void fraction. Impact coefficient, defined as the ratio between the maximum pressure at a given point and the corresponding mean kinetic energy, was obtained. For the wall impingement wave condition, the relationship between impact pressure and mean kinetic energy is linear with the impact coefficient close to 1.3. For the deck impingement wave condition, the above relationship does not show good correlation; the impact coefficient was between 0.6 and 7. The impact coefficient was found to be a function of the rate of pressure rise.


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    Title :

    Green water impact pressure on a three-dimensional model structure


    Contributors:

    Published in:

    Experiments in Fluids ; 53 , 6 ; 1879-1894


    Publication date :

    2012


    Size :

    16 Seiten




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English