Search for: water-waves
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    Influence of channel shape on wave-generated parameters by a pressure source in shallow water

    , Article Journal of Waterway, Port, Coastal and Ocean Engineering ; Volume 143, Issue 5 , 2017 ; 0733950X (ISSN) Javanmardi, M ; Binns, J ; Renilson, M ; Thomas, G ; Sharif University of Technology
    The present work is a numerical investigation into the waves generated by a pressure source moving in straight channels with a nonrectangular cross-channel depth profile. Wave fields generated by the moving pressure source are described, and the effects of channel bathymetry on the generated wave characteristics of wave height, wave-breaking location, wave-breaking type and intensity, and peel angle are presented. Four different channel cross-section shapes were investigated, and the results were analyzed. It was concluded that the maximum wave height depended primarily on pressure-source parameters and that the investigated channel shapes did not have a significant effect on the maximum... 

    A technique for detection of interfacial waves forming a two-dimensional pattern

    , Article Fluid Dynamics Research ; Vol. 46, issue. 1 , 2014 ; ISSN: 01695983 Safaie, A ; Fazeli M ; Jamali, M ; Sharif University of Technology
    In this paper, we consider resonant interaction between a surface wave and sub-harmonic interfacial waves forming a two-dimensional pattern at the interface between two fluid layers. The resulting interfacial pattern changes both in time and space. An image processing technique is proposed to extract information about the evolution of the component interfacial waves in a wave flume. The technique proved to give accurate and consistent results when applied to different stages of the interaction. The experimental measurements were used to verify the theoretical predictions. The method can be used for detection of some other wave motions  

    Lattice Boltzmann method for simulating impulsive water waves generated by landslides

    , Article Scientia Iranica ; Vol. 21, issue. 2 , 2014 , p. 318-328 ; 1026-3098 Pak, A ; Sarfaraz, M ; Sharif University of Technology
    Impulsive water waves generated by landslides impose severe damage on coastal areas. Very large mass ows in the ocean can generate catastrophic tsunamis. Preventing damage to dams and coastal structures, and saving the lives of local people against landslide-generated waves, has become an increasingly important issue in recent years. Numerical modeling of landslide-generated waves is a challenging subject in CFD. The reason lies in the difficulty of determining the interaction between the moving solids and sea water, which causes complicated turbulent regimes around the moving mass and at the water surface. Submarine or aerial types of landslide can further complicate the problem. Up to now,... 

    Free water surface oscillations in a closed rectangular basin with internal barriers

    , Article Scientia Iranica ; Volume 15, Issue 3 , Volume 15, Issue 3 , 2008 , Pages 315-322 ; 10263098 (ISSN) Kabiri Samani, A. R ; Ataie Ashtiani, B ; Sharif University of Technology
    Sharif University of Technology  2008
    Thee enclosed basin has certain natural frequencies of seiche, depending on the geometry of the water boundaries and the bathymetry of water depths. Therefore, the variation in the water surface at a point becomes irregular, as caused by the combination of several natural frequencies, which may be considered as the superposition of sinusoidal frequency components of different amplitude. This paper is mainly concerned with the motion of an incompressible irrotational fluid in a closed rectangular basin with internal impervious barriers. An analytical solution is presented for predicting the characteristic of generated waves in these types of basin. The equations of free water surface... 

    Experimental investigation on response and efficiency of moored pontoon type floating breakwaters

    , Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 31, Issue 1 , 2007 , Pages 95-99 ; 03601307 (ISSN) Behzad, M ; Akbari, M ; Sharif University of Technology
    This paper presents the experimental results of an investigation on the response and efficiency of floating pontoon type breakwaters. Random waves modeled by the Pierson Moskowits wave spectrum are used for various configurations of floating breakwaters. The experimental results are presented in graphs for the transmission coefficient as a function of incident wave length and height for breakwaters used in this study. The obtained results for the breakwaters of this study show that by increasing the wave period and length, the transmission coefficient increases, while increase in the mass and draft of the floating breakwater causes the transmission coefficient to reduce. © Shiraz University  

    Wave interaction pitch response of tension leg structures

    , Article 13th International Congress on Sound and Vibration 2006, ICSV 2006, Vienna, 2 July 2006 through 6 July 2006 ; Volume 5 , 2006 , Pages 3508-3515 ; 9781627481502 (ISBN) Tabeshpour, M. R ; Ataie Ashtiani, B ; Seif, M. S ; Golafshani, A. A ; Sharif University of Technology
    Because of fluctuation in leg tension, pitch motion is very effective in fatigue and life safety of leg elements in tension leg structures (TLSs). In this paper exact solution for pitch vibration of a TLS interacting with ocean wave is presented. The legs are considered as elastic springs. The flow is assumed to be irrotational and single-valued velocity potentials are defined. The effects of radiation and scattering are considered in the boundary value problem. Because of linear behavior of legs during wave excitation, ignoring coupling effects with other degrees of freedom, the analytical solution of pitch response has good agreement with the real behavior of the structure  

    Comprehensive study on the results of tension leg platform responses in random sea

    , Article Journal of Zhejiang University: Science ; Volume 7, Issue 8 , 2006 , Pages 1305-1317 ; 10093095 (ISSN) Tabeshpour, M. R ; Golafshani, A. A ; Seif, M. S ; Sharif University of Technology
    Compliant offshore structures are used for oil exploitation in deep water. Tension leg platform (TLP) is a suitable type for very deep water. The nonlinear dynamic response of TLP under random sea wave load is necessary for determining the maximum deformations and stresses. Accurate and reliable responses are needed for optimum design and control of the structure. In this paper nonlinear dynamic analysis of TLP is carried out in both time and frequency domains. The time history of random wave is generated based on Pierson-Moskowitz spectrum and acts on the structure in arbitrary direction. The hydrodynamic forces are calculated using the modified Morison equation according to Airy's linear... 

    Simple model for exact heave motion of tension leg platform

    , Article WSEAS Transactions on Mathematics ; Volume 5, Issue 5 , 2006 , Pages 500-506 ; 11092769 (ISSN) Tabeshpour, M. R ; Golafshani, A. A ; Seif, M. S ; Sharif University of Technology
    In this paper the dynamic response of the leg of a tension leg platform (tether) subjected to the load simulated as ocean wave at the top of the leg is presented. The structural model is very simple but several complicated factors such as foundation effect, buoyancy and simulated ocean wave load are considered. Two continuous models are proposed to present the structural system and the mentioned effects. The problem is solved by means of non-harmonic Fourier expansion in terms of eigenfunctions obtained from a non-regular Sturm-Liouville system  

    Seismic analysis of a system of dam-massed foundation-reservoir under inclined excitation

    , Article JVC/Journal of Vibration and Control ; 2021 ; 10775463 (ISSN) Sotoudeh, P ; Ghaemian, M ; Sharif University of Technology
    SAGE Publications Inc  2021
    One of the acceptable assumptions in engineering practice is vertical propagation of earthquake waves. When the source of earthquake is located very deep in the ground, this assumption is valid, but for sources located in shallow ground, it loses its viability. In this study, linear seismic analysis of a system of concrete dam-massed foundation-reservoir is performed under inclined earthquake excitation. Both P- and SV-type earthquakes are considered for the purpose of the seismic analysis. To consider the effects of inhomogeneous waves for the case of SV wave propagation, post-critical angles are also considered in the analysis. To investigate the effects of earthquake frequency content on... 

    Experimental investigation of instability of fluid mud layer under surface wave motion

    , Article Physics of Fluids ; Volume 34, Issue 3 , 2022 ; 10706631 (ISSN) Aleebrahim, M. A ; Jamali, M ; Sharif University of Technology
    American Institute of Physics Inc  2022
    Motivated by environmental impacts of surface-wave induced mixing of fluid mud with clear water in nearshore areas, this paper presents quantitative measurements of excitation of interfacial waves over a bed mud layer by a surface wave in a wave flume. After an initial fluidization process, a quasi-standing interfacial wave comprised of four interfacial waves was observed at the interface as a result of a resonant wave interaction with the surface wave. The interfacial waves were subharmonic to the surface wave and traveled at the maximum possible angle from it. The growth rate and kinematic properties of the interfacial waves were measured, and good agreement with theoretical predictions of... 

    Stability analysis of parametric resonance in spar-buoy based on Floquet theory

    , Article Ocean Engineering ; Volume 266 , 2022 ; 00298018 (ISSN) Aziminia, M. M ; Abazari, A ; Behzad, M ; Hayatdavoodi, M ; Sharif University of Technology
    Elsevier Ltd  2022
    Parametric resonance is a phenomenon caused by time-varying changes in the parameters of a system which may result in undesirable motion responses and instability. Floating bodies like ships and spar-buoys are prone to Mathieu instability mainly due to the instantaneous change of the metacentric height. With the fast-growing developments in Ocean Renewable Energy systems, spar-buoys are commonly used for wave energy convertors and floating wind turbines. Undesirable, unstable motions as a result of the parametric resonance can be problematic as it may cause inefficiency in operations and structural risk integrity. In this research, a new approach has been developed to investigate these... 

    Development of a Model to Investigate Energy Production Potential from Sea Applying GIS Technique

    , M.Sc. Thesis Sharif University of Technology Rahimi, Rahman (Author) ; Abbaspour, Majid (Supervisor)
    The growing requirements for renewable energy production lead to the development of a new series of systems, including wave and tidal energy conversion systems. Due to their sensitivity and the impact of the aggressive marine environment, the selection of the most adequate location for these systems is a major and very important task. Several factors, such as technological limitations, environmental conditions, administrative and logistic conditions, have to be taken into account in order to support the decision for best location. The aim of the present study is to provide an Atlas of IRAN Offshore Renewable Energy Resources (hereafter called ‘the Atlas’) to map out wave and tidal resources... 

    Effect of Aquatic Plants on Hydrodynamic and Dispersion in the Wave Motion

    , Ph.D. Dissertation Sharif University of Technology Tofighi, Mohammad Ali (Author) ; Jamali, Mirmosadegh (Supervisor)
    Aquatic plants play an important role in water environment. Increasing drag force, distorting the velocity and turbulence structures and other related parameters, are the results of the presences of plants. These changes affect the dispersion and mass transport in the aquatic areas. This thesis presents laboratory visualizations and measurements of wave motion, and passive solute surface dispersion (longitudinal and lateral) in arrays of cylinders, a model for emergent, rigid aquatic plants. In the range of (where is Keulegan–Carpenter number, is the maximum oscillatory velocity perpendicular to the cylinder axis, is the period of oscillation, and is the diameter of the cylinder), and (where... 

    Integrating constrained random waves in endurance time analysis of offshore structures subjected to sea waves

    , Article Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE, 1 July 2012 through 6 July 2012 ; Volume 2 , July , 2012 , Pages 677-684 ; 9780791844892 (ISBN) Matin Nikoo, H ; Estekanchi, H ; Zeinoddini, M ; Golestani, M ; Sharif University of Technology
    This paper introduces a novel methodology for design and assessment of offshore structures exposed to irregular sea waves. For this, Constrained NewWave (CNW) is integrated with the Endurance Time Analysis (ETA) methodology, which is basically developed for the performance based analysis of onshore structures to earthquake loads. In this approach, the offshore structure is simulated in time-domain under a set of calibrated intensifying wave functions. They are devised to represent a gradually increasing roughness of the sea state by time. A performance index such as base shear, drift or stress in a critical structural members are monitored until they reach to a predefined maximum value. A... 

    Incremental wave analysis and its application to performance-based assessment of jacket platforms

    , Article Journal of Constructional Steel Research ; Volume 67, Issue 10 , October , 2011 , Pages 1649-1657 ; 0143974X (ISSN) Golafshani, A. A ; Bagheri, V ; Ebrahimian, H ; Holmas, T ; Sharif University of Technology
    In this paper, a relatively novel approach is established to estimate different limit states and accurate behavior of jacket platforms against environmental wave loading. This novel approach which is called Incremental Wave Analysis (IWA) can be an appropriate substitute to current pushover practice. The IWA can take into account the effects of variation in wave height and wave-in-deck loading in the estimating of platforms' behavior. This paper aims to introduce the applications of this approach in deterministic assessment of offshore platforms, comprehensively. The IWA can estimate the collapse-prevention limit state of jacket platforms properly. In addition, an appropriate parameter for... 

    Assessment of offshore platforms under extreme waves by probabilistic incremental wave analysis

    , Article Journal of Constructional Steel Research ; Volume 67, Issue 5 , 2011 , Pages 759-769 ; 0143974X (ISSN) Golafshani, A. A ; Ebrahimian, H ; Bagheri, V ; Holmas, T ; Sharif University of Technology
    In this study, a novel probabilistic framework named Probabilistic Incremental Wave Analysis (PIWA) is established in order to assess the performance of jacket offshore platforms under extreme waves. The PIWA can take into account the uncertainties in three main elements consisting of sea state parameters, structural response and collapse capacity. The main advantage of the PIWA approach is reflected in decoupling of the wave hazard and structural analyses via an intermediate variable known as the wave height intensity measure. Despite the fact that most of the uncertainties associated with structural response are concentrated in wave hazard, this will enable the PIWA to estimate the... 

    Develop of a fully nonlinear and highly dispersive water wave equation set; analysis of wave interacting with varying bathymetry

    , Article Prediction and Simulation Methods for Geohazard Mitigation - Proceedings of the International Symposium on Prediction and Simulation Methods for Geohazard Mitigation, IS-KYOTO 2009, 25 May 2009 through 27 May 2009, Kyoto ; 2009 , Pages 213-218 ; 9780415804820 (ISBN) Najafi Jilani, A ; Ataie Ashtiani, B ; Sharif University of Technology
    Extended Boussinesq-type water wave equations are derived in two horizontal dimensions to capture the nonlinearity effects and frequency dispersion of wave in a high accuracy order. A multi-parameter perturbation analysis is applied in several steps to extend the previous second order Boussinesq-type equations in to 6th order for frequency dispersion and consequential order for nonlinearity terms. The presented high-order Boussinesq-type equation is applied in a numerical model to simulate the wave field transformation due to physical processes such as shoaling, refraction and diffraction. The models results are compared with available experimental data which obtained in a laboratory wave... 

    Simulation of wave generated by landslides in Maku dam reservoir

    , Article Prediction and Simulation Methods for Geohazard Mitigation - Proceedings of the International Symposium on Prediction and Simulation Methods for Geohazard Mitigation, IS-KYOTO 2009, 25 May 2009 through 27 May 2009 ; 2009 , Pages 91-96 ; 9780415804820 (ISBN) Yavari Ramshe, S ; Ataie Ashtiani, B ; Sharif University of Technology
    In this work, impulsive wave generation and propagation generated by landslides are studied numerically for a real case. Maku dam reservoir, in the northwestern of Iran is considered as the case study. Generated wave heights, wave run-up, maximum wave height above the dam crest and the probable overtopping volume have been evaluated, using a two-dimensional numerical model (LS3D). This model is validated using available three-dimensional experimental data for simulating impulsive wave caused by sub-aerial landslides. Based on the results, the generated wave height for first and second scenarios are 12 m and 18 m respectively. The wave height of 8 m is observed close to dam body. Because of... 

    Experimental study on the interfacial instability of particle-laden stratified shear flows

    , Article Journal of the Brazilian Society of Mechanical Sciences and Engineering ; Volume 40, Issue 4 , April , 2018 ; 16785878 (ISSN) Khavasi, E ; Firoozabadi, B ; Sharif University of Technology
    Springer Verlag  2018
    Turbidity currents are one of the more frequently observed types of stratified flows. In these currents, the density difference is created as a result of suspended particles. The interfacial instability of turbidity current is studied experimentally in the present research. Both Kelvin–Helmholtz and (asymmetric) Holmboe instabilities are observed during the experiments; the first one was downstream, and the second one was upstream of the obstacle. Kelvin–Helmholtz instability is observed by approximately zero (phase) speed with respect to the mean flow. With the aim of measuring spectral distribution of velocity fluctuations, the effects of some parameters are studied on interfacial waves;... 

    Estimation of near-field characteristics of tsunami generation by submarine landslide

    , Article Ocean Engineering ; Volume 35, Issue 5-6 , 2008 , Pages 545-557 ; 00298018 (ISSN) Najafi Jilani, A ; Ataie Ashtiani, B ; Sharif University of Technology
    Underwater landslide can trigger impulsive waves with high amplitude and run-up, which may cause substantial damage. In this work, the experimental investigations are performed to study the impulsive wave characteristics caused by underwater landslides. The effects of landslide geometry and kinematics on wave characteristics are studied by performing 84 laboratory experiments. The influences of thickness, volume and shape of failure mass on the characteristics of initial wave are discussed. The impacts of water body conditions such as the slope of sliding bed and the initial submergence of underwater landslide are also examined. The present experimental data as well as the available data in...