Browsing Τμήμα Μαθηματικών και Στατιστικής / Department of Mathematics and Statistics by Author "Alexandrou, Andreas N."

Now showing items 1-20 of 23

    • Article  

      Cessation of the lid-driven cavity flow of Newtonian and Bingham fluids 

      Syrakos, A.; Georgiou, Georgios C.; Alexandrou, Andreas N. (2016)
      We provide benchmark results for a transient variant of the lid-driven cavity problem, where the lid motion is suddenly stopped and the flow is left to decay under the action of viscosity. Results include Newtonian as well ...
    • Article  

      Determination of the rheological parameters of self-compacting concrete matrix using slump flow test 

      Neophytou, Marina K. A.; Pourgouri, Stella; Kanellopoulos, Antonios D.; Petrou, Michael F.; Ioannou, Ioannis; Georgiou, Georgios C.; Alexandrou, Andreas N. (2010)
      The classification of a concrete mixture as self-compacting (SCC) is performed by a series of empirical characterization tests that have been designed to assess not only the flowability of the mixture but also its segregation ...
    • Article  

      Determining true material constants of semisolid slurries from rotational rheometer data 

      Alexandrou, Andreas N.; Georgiou, Georgios C.; Economides, Eva Athena; Modigell, M. (2016)
      In this work we revisit the issue of obtaining true material constants for semisolid slurries. Therefore, we consider the circular Couette flow of Herschel-Bulkley fluids. We first show how true constants can be obtained ...
    • Article  

      Determining true material constants of viscoplastic materials from rotational rheometer data 

      Alexandrou, Andreas N.; Georgiou, Georgios C.; Economides, Eva-Athena; Zang, Christoph; Modigell, Michael (2018)
      We analyse the circular Couette flow of Herschel–Bulkley fluids to investigate the validity of the assumption that the rate of strain distributions across the gap share a common point. It is demonstrated that this is true ...
    • Article  

      Flow development in compression of a finite amount of a Bingham plastic 

      Florides, G. C.; Alexandrou, Andreas N.; Georgiou, Georgios C. (2007)
      The flow and shape evolution during the compression of a finite amount of a Bingham plastic is investigated by means of numerical simulations. The problem relates to the popular compression test used for the rheological ...
    • Article  

      Flow instabilities of Herschel-Bulkley fluids 

      Alexandrou, Andreas N.; Le Menn, P.; Georgiou, Georgios C.; Entov, V. (2003)
      We investigate numerically the interactions of two-dimensional jets of Bingham plastic and Herschel-Bulkley fluids with a vertical surface at a distance from the die exit. This problem simulates the early stages of filling ...
    • Article  

      On the early breakdown of semisolid suspensions 

      Alexandrou, Andreas N.; Georgiou, Georgios C. (2007)
      Semisolid materials are suspensions of metal alloys which are processed while in a mushy state. In this state, the suspensions behave as viscoplastic materials with time-dependent material properties. During processing, ...
    • Article  

      Parameter estimation for semi-solid aluminum alloys using transient experiments 

      Alexandrou, Andreas N.; Georgiou, Georgios C.; Tonmukayakul, N.; Apelian, D. (2006)
      A rotating vane-cup rheometer is used to determine the rheological properties of semi-solid slurries, and a procedure is established for characterizing the rheology with emphasis given to the proper and self-consistent ...
    • Article  

      Performance of the finite volume method in solving regularised Bingham flows: Inertia effects in the lid-driven cavity flow 

      Syrakos, A.; Georgiou, Georgios C.; Alexandrou, Andreas N. (2014)
      We extend our recent work on the creeping flow of a Bingham fluid in a lid-driven cavity, to the study of inertial effects, using a finite volume method and the Papanastasiou regularisation of the Bingham constitutive model ...
    • Article  

      Predictions of structure breakdown, buildup and shear banding in semisolid suspensions 

      Alexandrou, Andreas N.; Constantinos, N.; Georgiou, Georgios C. (2008)
      When SSM material is subjected to a sudden transient the rate of buildup (aging) is negligible compared to the rate of breakdown (shear rejuvenation). While this is generally true, due to prolonged processing or the geometry ...
    • Article  

      Preface to Special Issue: Papers from HSR 2017—8th International Meeting of the Hellenic Society of Rheology, Limassol, Cyprus, July 12–14, 2017 

      Georgiou, Georgios C.; Alexandrou, Andreas N. (2018)
    • Conference Object  

      Rheological effects of strusture breakdown in semisolid slurries 

      Alexandrou, Andreas N.; Florides, G. C.; Georgiou, Georgios C.; Apelian, D. (2004)
      An essential element for the integration of the semisolid metal (SSM) process in the production of complex commercial components is the availability of accurate mathematical and computational tools that could describe both ...
    • Article  

      Shear rejuvenation, aging and shear banding in yield stress fluids 

      Alexandrou, Andreas N.; Constantinou, N.; Georgiou, Georgios C. (2009)
      The purpose of this work is to simulate shear rejuvenation and aging effects in shear thinning yield stress fluids in a typical rotational rheometer and to provide a common framework to describe the behavior of yield stress ...
    • Article  

      Solution of the square lid-driven cavity flow of a Bingham plastic using the finite volume method 

      Syrakos, A.; Georgiou, Georgios C.; Alexandrou, Andreas N. (2013)
      We investigate the performance of the finite volume method in solving viscoplastic flows. The creeping square lid-driven cavity flow of a Bingham plastic is chosen as the test case and the constitutive equation is regularised ...
    • Conference Object  

      Solution of viscoplastic flows with the finite volume / multigrid method 

      Syrakos, A.; Georgiou, Georgios C.; Alexandrou, Andreas N. (National Technical University of Athens, 2013)
      We investigate the performance of the finite volume method in solving viscoplastic flows. The square lid-driven cavity flow of a Bingham plastic is chosen as the test case and the constitutive equation is regularised as ...
    • Article  

      Squeeze flow of semi-solid slurries 

      Alexandrou, Andreas N.; Florides, G. C.; Georgiou, Georgios C. (2013)
      A standard method used to determine material properties of semi-solid slurries is the squeeze flow experiment
    • Article  

      Squeeze flow of semi-solid slurriesAAA 

      Alexandrou, Andreas N.; Florides, G. C.; Georgiou, Georgios C. (2013)
      A standard method used to determine material properties of semi-solid slurries is the squeeze flow experiment in which a fixed amount of material is squeezed under constant force or velocity. The relation between the force ...
    • Article  

      Squeeze flow of thixotropic semisolid slurries 

      Alexandrou, Andreas N.; Florides, G. C.; Georgiou, Georgios C. (2014)
      An essential element for the integration of a semisolid process in the production of complex commercial components is the availability of accurate mathematical and computational tools that could describe both the rheological ...
    • Article  

      Start-up plane Poiseuille flow of a Bingham fluid 

      Huilgol, Raja R.; Alexandrou, Andreas N.; Georgiou, Georgios C. (2019)
      The start-up flow of a Bingham plastic in a channel is considered and Safronchik’s solution [1] for the initial evolution of the yield surface and the core velocity is revisited. Stricter time bounds for the validity of ...
    • Article  

      Thixotropic flow past a cylinder 

      Syrakos, A.; Georgiou, Georgios C.; Alexandrou, Andreas N. (2014)
      We study the flow of a thixotropic fluid around a cylinder. The rheology of the fluid is described by means of a structural viscoplastic model based on the Bingham constitutive equation, regularised using the Papanastasiou ...