Browsing NTNU Open by Author "Thorsen, Mats Jørgen"

Now showing items 1-14 of 14

    • A numerical study on vortex-induced vibrations and the effect of slurry density variations on fatigue of ocean mining risers 

      Thorsen, Mats Jørgen; Challabotla, Niranjan Reddy; Sævik, Svein; Nydal, Ole Jørgen (Journal article; Peer reviewed, 2019)
      Ocean mining emerges as a way of meeting future demands for valuable minerals. Risers conveying ore from the seabed to the surface must withstand large wave and current loads. In addition, vortex-induced vibrations (VIV) ...

    • An Analytical Model of the Effect of Internal Density Waves in Risers Subjected to Vortex Shedding 

      Thorsen, Mats Jørgen; Sævik, Svein (Chapter, 2018)
      Risers used for deep sea mining will be subjected to vortex-induced vibrations (VIV) caused by ocean currents. The internal flow, consisting of e.g. mineral ore and water, will have a non-uniform density. This traveling ...

    • An Analytical Treatment of Buckling and Instability of Tensile Armors in Flexible Pipes 

      Sævik, Svein; Thorsen, Mats Jørgen (Journal article; Peer reviewed, 2017)
      The present paper addresses aspects related to local buckling and instability of tensile armors in flexible pipes. Analytical models for evaluating the tensile armor buckling capacity in both transverse (radial and lateral) ...

    • An Analytical Treatment of Buckling and Instability of Tensile Armors in Flexible Pipes 

      Sævik, Svein; Thorsen, Mats Jørgen (Journal article; Peer reviewed, 2017)
      The present paper addresses aspects related to local buckling and instability of tensile armors in flexible pipes. Analytical models for evaluating the tensile armor buckling capacity in both transverse (radial and lateral) ...

    • Capacity of Deep Water Flexible Risers 

      Thorsen, Mats Jørgen (Master thesis, 2011)
      A flexible riser operating in deep water will experience large environmental forces. Due to the length of the riser, dynamic tension from drag forces will be substantial. The tensile force is transferred directly into the ...

    • Non-linear time domain analysis of cross-flow vortex-induced vibrations 

      Thorsen, Mats Jørgen; Sævik, Svein; Larsen, Carl Martin (Journal article; Peer reviewed, 2017)
      A previously proposed hydrodynamic load model for time domain simulation of cross-flow vortex-induced vibrations (VIV) is modified and combined with Morison's equation. The resulting model includes added mass, drag and a ...

    • Numerical Analysis of Combined VIV and Slug Flow in Time Domain 

      Knudsen, Tor Huse; Sævik, Svein; Thorsen, Mats Jørgen (Chapter; Peer reviewed, 2016)
      Vortex induced vibrations (VIV) and slug flow are two important aspects for marine risers conveying a multiphase flow, and should be carefully examined due to the influence on the fatigue life of the structure. This article ...

    • Simulating fundamental and higher harmonic VIV of slender structures 

      Ulveseter, Jan Vidar; Thorsen, Mats Jørgen; Sævik, Svein; Larsen, Carl Martin (Journal article; Peer reviewed, 2019)
      Vortex-induced vibrations (VIV) of slender marine structures are complicated response processes, where a number of distinct frequency components might be simultaneously active. These are categorized as fundamental and ...

    • Simulating riser VIV in current and waves using an empirical time domain model 

      Thorsen, Mats Jørgen; Sævik, Svein (Chapter; Peer reviewed, 2017)
      The theoretical background of an empirical model for time domain simulation of VIV is reviewed. This model allows the surrounding flow to be time varying, which is in contrast to the traditional frequency domain tools. The ...

    • Stochastic modelling of cross-flow vortex-induced vibrations 

      Ulveseter, Jan Vidar; Thorsen, Mats Jørgen; Sævik, Svein; Larsen, Carl Martin (Journal article, 2017)
      Semi-empirical models are commonly used to predict vortex-induced vibrations (VIV). Empirical parameters are often based on forced harmonic motion tests of short rigid cylinders in one degree of freedom, which is a significant ...

    • Time Domain Analysis of Vortex-Induced Vibrations 

      Thorsen, Mats Jørgen (Doctoral thesis at NTNU;2016:231, Doctoral thesis, 2016)
      This thesis deals with the development of a new empirical model of the hydrodynamic loads associated with vortex-induced vibrations (VIV) of slender circular cylinders. The most commonly used VIV analysis tools operate in ...

    • Time domain simulation of riser VIV in current and irregular waves 

      Ulveseter, Jan Vidar; Thorsen, Mats Jørgen; Sævik, Svein; Larsen, Carl Martin (Journal article; Peer reviewed, 2018)
      A semi-empirical prediction tool for time domain analysis of cross-flow and in-line vortex-induced vibrations (VIV) is proposed. The model combines concepts from previous publications in a new way, which allows for time ...

    • Time domain simulation of vortex-induced vibrations in stationary and oscillating flows 

      Thorsen, Mats Jørgen; Sævik, Svein; Larsen, Carl Martin (Journal article, 2016)
      This paper focuses on the further development of a previously published semi-empirical method for time domain simulation of vortex-induced vibrations (VIV). A new hydrodynamic damping formulation is given, and the necessary ...

    • Vortex-induced vibrations of a vertical riser with time-varying tension 

      Thorsen, Mats Jørgen; Sævik, Svein (Journal article; Peer reviewed, 2017)
      Numerical simulations of a vertical tensioned riser in a sheared flow are performed, where the riser top end oscillates sinusoidally in the vertical direction. The oscillating top-end motion causes tension variations and ...