The aim of the research project is to develop a model that would consider unsteady friction of turbulent liquid flow. Such a model could be included in 1D computational code to analyze flow in complex pipelines. A CFD study in an axisymmetric flow domain was conducted to better understand the phenomenon in oscillating flow. Different settings of boundary conditions were used based on experimental investigation, conducted at Delft University, The Netherlands. CFD results show that the unsteady wall friction is space dependent phenomenon. Direct transfer form multidimensional approach to a 1D code is not trivial due to unsteady conditions and temporal shift between maximal velocity and wall shear stress profile. Coupled CFD and 1D Method of characteristics (MOC) numerical simulation is being developed to adequately assess the effect of unsteady friction in 1D approach for different types of unsteady flows. Such a coupled approach should simultaneously adjust the friction factor in 1D code based on properly averaged CFD results.
F.02 Acquisition of new scientific knowledge
COBISS.SI-ID: 14540059A flexible experimental apparatus for investigating water hammer, column separation, fluid-structure interaction, and pipeline filling and emptying has been designed and constructed at the University of Montenegro. Transient pressures were investigated at the pipe end points and at one- and two-third points along the pipe by using single- and multiple-valve actions. The main objective of the paper was to investigate effects of a number of valve actions on pressure magnitudes and timing for several flow situations. Investigations prove that the frequency of pressure waves is increasing as the pipe length is decreasing. The highest the frequency, the faster is the damping of pressure waves (in terms of time) and the importance of the unsteady friction. One of the most interesting outcomes of this paper is that the multiple-valve induced closure events may either attenuate or amplify the severity of pressure oscillations in the pipeline system. Moreover, at particular flow situations, the pressure may be kept constant for some time. All these facts may play an important role in industrial control of valves (smart valves). Finally, an improved numerical discrete gas cavity model (DGCM) with inclusion of the convolution-based unsteady friction term has been successfully validated against the investigated experimental runs including water hammer and column separation cases. The computational results give pressure histories that are in reasonable agreement with the measured results.
F.18 Transfer of new know-how to direct users (seminars, fora, conferences)
COBISS.SI-ID: 14359835The aim of the research project is to develop a model that would consider unsteady friction of turbulent liquid flow. Such a model could be included in 1D computational code to analyze flow in complex pipelines. A CFD study in an axisymmetric flow domain was conducted to better understand the phenomenon in oscillating flow. Different settings of boundary conditions were used based on experimental investigation. Several variations of settings in Ansys Fluent CFD package are introduced and discussed. The geometry and discretization procedure is shown along with full transcript of command lines in Gambit preprocessing tool. 1D-MOC program coded in Matlab is also included. This program is the base for 1D-MOC – 2D-CFD simulation system. Key results are processed and plotted within OriginPro. Based on the given data, one could replicate all the work that is presented.
F.23 Development of new system-wide, normative and programme solutions, and methods
COBISS.SI-ID: 14541339