Ktisis Cyprus University of Technologyhttps://ktisis.cut.ac.cyThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Tue, 21 Jan 2020 19:31:41 GMT2020-01-21T19:31:41Z5051Pressure induced by the interaction of water waves with nearly equal frequencies and nearly opposite directionshttps://ktisis.cut.ac.cy/handle/10488/12648Title: Pressure induced by the interaction of water waves with nearly equal frequencies and nearly opposite directions
Authors: Pellet, Lauranne; Christodoulides, Paul; Donne, Sarah; Bean, Chris; Dias, Frédéric
Abstract: We present second-order expressions for the free-surface elevation, velocity potential and pressure resulting from the interaction of surface waves in water of arbitrary depth. When the surface waves have nearly equal frequencies and nearly opposite directions, a second-order pressure can be felt all the way to the sea bottom. There are at least two areas of applications: reflective structures and microseisms. Microseisms generated by water waves in the ocean are small vibrations of the ground resulting from pressure oscillations associated with the coupling of ocean surface gravity waves and the sea floor. They are recorded on land-based seismic stations throughout the world and they are divided into primary and secondary types, as a function of spectral content. Secondary microseisms are generated by the interaction of surface waves with nearly equal frequencies and nearly opposite directions. The efficiency of microseism generation thus depends in part on ocean wave frequency and direction. Based on the second-order expressions for the dynamic pressure, a simple theoretical analysis that quantifies the degree of nearness in amplitude, frequency, and incidence angle, which must be reached to observe the phenomenon, is presented.
Mon, 01 May 2017 00:00:00 GMThttps://ktisis.cut.ac.cy/handle/10488/126482017-05-01T00:00:00ZAssessing ocean wave energy potential and microseismshttps://ktisis.cut.ac.cy/handle/10488/3992Title: Assessing ocean wave energy potential and microseisms
Authors: Pellet, Lauranne; Dias, Frederic; Christodoulides, Paul
Abstract: Ocean gravity waves driven by wind and atmospheric pressure generate pressure variations on the sea floor, which are at the origin of microseism. These microseisms can be recorded as a “noise” in seismic recordings by coastal seismic stations. Two types of microseism can be recorded: primary and secondary. We are interested in the secondary microseisms, which have a frequency twice that of the causative wave and amplitude independent of the depth. From the records of coastal seismic stations, we are able to determine wave characteristics (period, height).
So we need to know the sea states that allow pressure variations large enough to generate microseisms. We also need to understand how pressure variations vary in space and time and how they are linked to the sea floor. We will present the results obtained for the oceanic pressure in different cases. We will also show the conditions on different parameters to obtain pressure variation able to generate microseisms. Finally, we will study the pressure with respect to different parameters in order to illustrate our theoretical results.
Thu, 01 May 2014 00:00:00 GMThttps://ktisis.cut.ac.cy/handle/10488/39922014-05-01T00:00:00ZInteraction of waves with nearly equal frequencies and oceanic microseismshttps://ktisis.cut.ac.cy/handle/10488/10013Title: Interaction of waves with nearly equal frequencies and oceanic microseisms
Authors: Christodoulides, Paul; Pellet, Lauranne; Bean, C.; Donne, S.; Dias, Frederic
Fri, 01 Jan 2016 00:00:00 GMThttps://ktisis.cut.ac.cy/handle/10488/100132016-01-01T00:00:00ZInteraction of ocean waves of nearly equal frequencies and the effect on pressurehttps://ktisis.cut.ac.cy/handle/10488/13380Title: Interaction of ocean waves of nearly equal frequencies and the effect on pressure
Authors: Christodoulides, Paul; Pellet, Lauranne; Donne, Sarah; Bean, Chris; Dias, Frédéric
Abstract: We study the superposition of a train of freely traveling waves in a form that includes the possibility for each wave of complex amplitude An to have a ‘sister’ wave of complex amplitude Bn with equal frequency and opposite direction. For an ideal, incompressible and homogeneous fluid, we consider three-dimensional flows that are irrotational and spaceperiodic. Through a weakly nonlinear analysis we obtain full second-order expressions for the free-surface elevation, the velocity potential and the dynamic pressure. Then we generalize and unify all related expressions in the literature, without any assumption on the water depth. When the frequencies of the surface waves of nearly opposite directions are nearly equal, a second-order pressure can be felt all the way to the sea bottom. Hence, in particular, we apply a theoretical analysis on the dynamic pressure obtained, and we quantify the degree of nearness in amplitude, frequency and incidence angle that must be reached to observe the phenomenon. Such phenomena of the second-order pressure, independent of the depth, have been supposed to be at the origin of so-called secondary microseisms. A comparison with real data for pressure induced by waves in the ocean is also presented.
Wed, 01 Mar 2017 00:00:00 GMThttps://ktisis.cut.ac.cy/handle/10488/133802017-03-01T00:00:00ZOcean waves and microseismshttps://ktisis.cut.ac.cy/handle/10488/10010Title: Ocean waves and microseisms
Authors: Christodoulides, Paul; Pellet, Lauranne; Bean, C.; Donne, S.; Dias, Frederic
Mon, 01 Aug 2016 00:00:00 GMThttps://ktisis.cut.ac.cy/handle/10488/100102016-08-01T00:00:00Z