Effects of Stratification on Multi-layered Tsunami Waves
Widely used tsunami warning systems are based on numerical simulations and consider a single layer system, i.e. it is considered that the whole depth of ocean water is having a single density, which is not a realistic approximation. In order to develop a
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Effects of Stratification on Multi-layered Tsunami Waves Monzur A. Imteaz, Fatemeh Mekanik, and Amimul Ahsan
Abstract Widely used tsunami warning systems are based on numerical simulations and consider a single layer system, i.e. it is considered that the whole depth of ocean water is having a single density, which is not a realistic approximation. In order to develop a generalized numerical model for multi-layered tsunami wave system, a three-layer system was developed earlier. Six governing equations, two for each layer were derived from Euler equations of motion and continuity for three layers, assuming long wave approximation, negligible friction and interfacial mixing. Developed governing equations were converted to a numerical model using staggered Leap-Frog scheme for the computations of water level and discharge in each layer in one-dimensional propagation. Developed numerical model results were earlier validated (through converting it to a pseudo two- layer model) with a two-layer model, which was rigorously verified by analytical solution. This paper presents effects of stratification on the amplification and water levels of tsunami waves. For the representation of the magnitude of stratification, a new dimensionless number named “stratification number” has been proposed. The model has been simulated for several combinations of layer densities. It is found that with the increase in stratification number magnitude of wave surface level as well as wave amplitude decrease.
M.A. Imteaz (*) • F. Mekanik Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, Hawthorn, Melbourne, VIC 3122, Australia e-mail: [email protected] A. Ahsan Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, Hawthorn, Melbourne, VIC 3122, Australia Department of Civil Engineering (Green Engg. & Sust. Tech. Lab, Institute of Advanced Technology), University Putra Malaysia, Selangor, Malaysia C.W. Finkl (ed.), Coastal Hazards, Coastal Research Library 6, 735 DOI 10.1007/978-94-007-5234-4_23, # Springer Science+Business Media Dordrecht 2013
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Introduction
Tsunamis can cause widespread coastal hazards including loss of lives, damages to infrastructures, damages to coastal ecosystems and agriculture. On top of that recently occurred tsunami in Japan proved how tsunami havoc can impact on extremely sensitive coastal nuclear establishments and indirectly cause widespread nuclear pollutions. These coastal hazards can be minimized through proper and efficient tsunami warning system. During 2011 Tohoku earthquake (magnitude 9.0) and subsequent tsunami, Japanese tsunami warning system failed to produce accurate predictions (Nature 2011). Widely used tsunami warning systems are based on numerical simulations and consider a single layer system, i.e. it is considered that the whole depth of ocean water is having a single density, which is not a realistic approximation. In order to develop a generalized numerical model for multi-layered tsunami wave syste
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