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Fluid Mechanics and Hydraulic Transport

Main research domains

  • Solution of theoretical and experimental problems in mechanics of fluid and disperse systems with application especially in pipeline transport and handling of bulk materials, in open channel flow and environmental protection
  • turbulent flow of dilute suspensions in pipe
  • viscoplastic fluid flows in complex geometries
  • hydrodynamics of open channel, flow around obstacles
  • rheology of suspensions and dense fine-grained slurry flow in pipe
  • hydraulic transport, handling and deposition of bulk materials, capsule pipelining, hydrohoists
  • large-scale organized vortical structures in turbulent wakes
  • heat and mass transfer in a pipe and impact flow

Most important results

  • The database used for verification of the models for individual suspensions was created, it incorporated the results of experimental research in these topics:
    • rheological measurement on rotational viscometer of additive and non-additive cement mixtures, bauxite wastes, kaolin and other materials
    • turbulent characteristics (mean velocity distribution, intensities of turbulence power spectra, particle/liquid slip velocity) of dilute suspensions of solid particles (polystyrene, glass, sand) in water
    • hydrodynamic characteristics of dense fine-grained suspensions in smooth and rough pipes (friction losses in dependence on slurry velocity, volume concentration and other physical and chemical parameters of the slurry)
  • The analysis of an extensive experimental ensemble - averaged - data basis on the turbulent wake behind a pair of side-by-side square cylinders revealed the difference between essential features of vortex dynamics, turbulence characteristics and flow topology in one-cylinder and two-cylinder wakes.
  • The approximate formula was derived for axial laminar flow of viscoplastic fluid through an eccentric annulus, which permits description of the asymmetry of a plug, and it calculates the values of the flow rate with relatively high accuracy. The more accurate results were obtained by FEM and an origin and shapes of two plugs were described.
  • Numerical simulations of the apparent slip effect performed for axial laminar flow of several types of non-Newtonian liquids in circular annuli for symmetrical slip layers in the range of 1-20 mm showed non-negligible increase in the average velocity as a consequence of slip. Apparent slip can play an important role in annular geometry especially for small pressure gradients.
  • The exact relationship valid for the Borda-Carnot local losses were derived for viscoplastic liquids described by the Herschel-Bulkley model. The performed calculations show the significance and applicability of the correction coefficients for the kinetic energy and momentum of the liquid stream in the framework of hydraulics of one-dimensional flow.
  • The two-component LDA technique was used to acquire new information about turbulent structure in smooth and rough open channel flow and effect of macro-roughness elements in steep channel flows. From the research following conclusions can be drawn
    • velocity distribution near the rough bottom is more uniform than the log-law profile expected, no effect of channel slope on the dimensionless velocity distributions (U/U*) was found (for the same type of bed roughness)
    • decrease of longitudinal non-dimensional turbulence intensities with increasing grain size of bed roughness was observed in the near bed region.
  • Experimentally it was proved that the real value of impinging velocity is lower than the jet exit velocity corrected by the effect of gravity and the constant free surface velocity of the radial flow is equal to the real value of impinging velocity.
  • The numerical simulation and experimental verification proved that the hydrohoist pipeline system is a suitable way for transporting a large quantity of bulk material under high operational pressure with high concentration and very little wear of the movable parts of pumps and valves. Compared with the conventional systems it is more universal, it attains higher efficiency and longer service life.
  • It was proved that hydrodynamic theory of lubrication model of a capsule-liquid-pipeline system can serve as an appropriate approximation of the lift-off forces, acting on a capsule conveyed by liquid. Further, it was experimentally proved that using of micellar additives (complex soap SEAN) considerably reduces power consumption of a capsule-liquid flow and that capsule-pipelining is a promising way for the long distance transport of highly viscous liquids, large quantity of bulk materials, and in paste slugs modification also for the technological transport and hydraulic back-filling of mines.
  • Flow behaviour of the dense hydromixtures, e.g. ash - gypsum water of volumetric concentration about 50%, was determined - it is possible to approximate the mixture as visco-plastic liquid by Herschel-Bulkley model. The high concentration pipelining is a suitable way of handling and deposition of energetical wastes after desulphurization processes. It is a very progressive and effective method from the economical and environmental points of view.