Recent Submissions

  • Computational Fluid Dynamics Study of Shear Thinning Fluid (Drilling Fluid) Viscosity Models in an Open Venturi Channel 

    Welahettige, Prasanna Kumara Welahetti; Lie, Bernt; Vågsæther, Knut (Journal article; Peer reviewed, 2019)
    We aim to develop an improved kick/loss detection technology by developing smart flow-sensor technology for returned flow from the oil well in open Venturi channels. This is a detailed study about a capacity of use of ...
  • A Real-Time Flow-Measuring Algorithm for Open Venturi Channel Non-Newtonian Flow 

    Welahettige, Prasanna Kumara Welahetti; Lie, Bernt; Vågsæther, Knut (Peer reviewed; Journal article, 2019)
    A real-time flow measuring algorithm is developed for the open Venturi channel non-Newtonian flow measurement. Using a single level sensor reading at downstream of the open Venturi channel, a drilling-well return flow rate ...
  • Quantitative genetics state-space modeling of phenotypic plasticity and evolution 

    Ergon, Rolf Otto Torbjørn (Peer reviewed; Journal article, 2019)
    Living organisms adapt to changes in environment by phenotypic plasticity and evolution by natural selection (or they migrate). At detailed genetic levels these phenomena are complicated, and quantitative genetics attempts ...
  • Alumina scale composition and growth rate in distribution pipes 

    Haugland, Ingrid Bokn; Kjos, Ole Sigmund; Røyset, Arne Karstein; Vullum, Per Erik; Aarhaug, Thor Anders; Halstensen, Maths (Peer reviewed; Journal article, 2019)
    Scaling in distribution pipes for secondary alumina is a major issue in aluminium smelters. The scale is formed inside the distribution pipes, and gradually reduces the cross section that is available for alumina transport. ...
  • Nonlinear observer for hydropower system 

    Vytvytskyi, Liubomyr; Sharma, Roshan; Lie, Bernt (Peer reviewed; Journal article, 2019)
    Estimation of unmeasured states plays an essential role in the design of control systems as well as for monitoring of hydropower plants. The standard Kalman filter gives the optimum state estimates for linear systems. ...
  • One-dimensional model of turbulent flow of non-Newtonian drilling mud in non-prismatic channels 

    Welahettige, Prasanna Kumara Welahetti; Lundberg, Joachim; Bjerketvedt, Dag; Lie, Bernt; Vågsæther, Knut (Peer reviewed; Journal article, 2019)
    One-dimensional model of non-Newtonian turbulent flow in a non-prismatic channel is challenging due to the difficulty of accurately accounting for flow properties in the 1-D model. In this study, we model the 1-D Saint–Venant ...
  • OpenHPL for Modelling the Trollheim Hydropower Plant 

    Vytvytskyi, Liubomyr; Lie, Bernt (Peer reviewed; Journal article, 2019)
    An increase of tightly integrated, renewable energy sources with highly varying production leads to a greater need for flexible hydropower plants to “balance” the intermittent production from these sources. From a systems ...
  • Combining measurements with models for superior information in hydropower plants 

    Vytvytskyi, Liubomyr; Lie, Bernt (Peer reviewed; Journal article, 2019)
    Water flow and pressure measurements play essential roles in the operation of hydropower plants. For all methods of measuring flow and pressure, there is a level of uncertainty with regards to sensor noise and sensor ...
  • Computational Fluid Dynamics Study of the Effects of Drill Cuttings on the Open Channel Flow 

    Welahettige, Prasanna Kumara Welahetti; Berg, Christian; Lundberg, Joachim; Lie, Bernt; Vågsæther, Knut (Peer reviewed; Journal article, 2019)
    A three-dimensional computational fluid dynamics (CFD) study was carried out for drilling fluid flow with drill cuttings in open channels. The flow is similar to the return flow when drilling, stream containing drilling ...
  • OMJulia: An OpenModelica API for Julia-Modelica Interaction 

    Lie, Bernt; Palanisamy, Anandhakumar; Mengist, Alachew; Buffoni, Lena; Sjölund, Martin; Asghar, Adeel; Pop, Adrian; Fritzson, Peter (Peer reviewed; Journal article, 2019)
    Modelica is an object oriented, acausal equation-based language for describing complex, hybrid dynamic models. About ten Modelica implementations exist, of which most are commercial and two are open source; the implementations ...
  • Controller Design for a Magnetic Levitation Kit using OpenModelica’s Integration with the Julia Language 

    Thiele, Bernhard; Lie, Bernt; Sjölund, Martin; Pop, Adrian; Fritzson, Peter (Peer reviewed; Journal article, 2019)
    This paper presents a practical application of computer aided control systems design using a new OpenModelica API (OMJulia) which allows to conveniently operate on Modelica models from the Julia language. Julia is a rather ...
  • Structural analysis in Julia for dynamic systems in OpenModelica 

    Vytvytskyi, Liubomyr; Lie, Bernt (Peer reviewed; Journal article, 2019)
    In control theory for dynamic systems, the information about observability and controllability of states plays a key role to evaluate the possibility to observe states from outputs, and use inputs to move states to a desired ...
  • Surrogate and Hybrid Models for Control 

    Lie, Bernt (Peer reviewed; Journal article, 2019)
    With access to fast computers and efficient machine learning tools, it is of interest to use machine learning to develop surrogate models from complex physics-based models. Next, a hybrid model is a combination model where ...
  • Flood Management of Lake Toke: MPC Operation under Uncertainty 

    Menchacatorre, Itsaso; Sharma, Roshan; Furenes, Beathe; Lie, Bernt (Peer reviewed; Journal article, 2019)
    A deterministic reference tracking model predictive control (MPC) is in use at Skagerak Kraft for flood management of Lake Toke in Norway. An operational inflow estimate is used to predict the optimal gate opening at Dalsfos ...
  • State Estimation of a Thermal Model of Air-cooled Synchronous Generator 

    Pandey, Madhusudhan; Øyvang, Thomas; Lie, Bernt (Peer reviewed; Journal article, 2019)
    In this paper, we extend a previous study on a totally enclosed thermal model of a synchronous generator, with temperature state estimation using experimental data. The extension includes a new formulation of the system ...
  • Models for control of thermal energy in buildings 

    Johansen, Casper Amandus; Lie, Bernt; Skeie, Nils-Olav (Peer reviewed; Journal article, 2019)
    A large fraction of the world’s energy production is used for HVAC in buildings. It is therefore important to develop improved strategies for ef?cient use of energy in buildings. Storage of intermittent energy production ...
  • Pressure wave propagation in Managed Pressure Drilling- model comparison with real life data 

    Berg, Christian; Stakvik, Jon Åge; Lie, Bernt; Vågsæther, Knut; Kaasa, Glenn-Ole (Peer reviewed; Journal article, 2019)
    Drilling for oil and gas is a complex process, involving pumping of fluid through kilometers of pipes. Even though the drilling fluid has a high speed of sound (˜1000 m/s), the large lengths involved make pressure wave ...
  • Enhanced Power Capability of Generator Units for Increased Operational Security using NMPC 

    Øyvang, Thomas; Nøland, Jonas Kristiansen; Sharma, Roshan; Hegglid, Gunne John; Lie, Bernt (Peer reviewed; Journal article, 2019)
    The ever-increasing penetration of intermittent energy sources introduces new demanding operating regimes for the bulk power generation in the power grid. During a worst-case power system disturbance scenario, the generator ...
  • STEAM FOR STEM - INCLUDE "ART" in STEM (Science, Technology, Engineering and Mathematics) 

    Halvorsen, Hans-Petter; Tretjakova, Rasma; Timmerberg, Josef; THIRIET, Jean; Mylvaganam, Kanagasabapath (Chapter, 2019)
    After a fairly recent study discussed in IEEE Spectrum, with the catchy title, “want-girls-attracted-to-tech-put-a-for-art-in-stem”, on the strategies of attracting more female students to opt for studies in STEM (Science, ...
  • Parameter estimation for externally simulated thermal network models 

    Brastein, Ole Magnus; Lie, Bernt; Sharma, Roshan; Skeie, Nils-Olav (Peer reviewed; Journal article, 2019)
    Obtaining accurate dynamic models of building thermal behaviour requires a statistically solid foundation for estimating unknown parameters. This is especially important for thermal network grey-box models, since all their ...

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