Fluid mechanics


Fluid mechanics is the branch of physics concerned with balance and movement of fluids and fluid systems under the influence of external and internal forces. The fundamental difference between the rigid body and the fluid is the mobility of the molecules. Rigid body moves as a set of mass points of a given shape, the fluid does not have its own shape and, contrary to the rigid body under the action of forces irreversibly deforms, its particles are brought into motion, and flow in current bounded by solid walls or interface (level).  The goal of fluid mechanics is to explain phenomena and processes occurring in fluids and fluid systems using physical laws and predicting the behavior of fluids and fluid systems in certain conditions, to determine the distribution of fluid properties, i.e. pressure, density, velocity, temperature, concentration, etc. and possibly changes in these variables over time in different locations within the liquid.  

Research of two- and multi- phase systems flow, including the movement of solid particles in a fluid is the theoretical basis of many engineering disciplines. The study of fluid and fluid systems mechanics at the Institute of Hydrodynamics ASCR , v. v. i., is focused on theoretical and experimental investigation of the flow of suspension, the movement of particles and sediment in close and open conduits, tanks and reservoirs, mixing processes of fluid systems, as well as on mathematical modelling and numerical simulation, calibration and verification of flow models based on the results of experimental research, on experimental methods, and on analysis of a turbulent flow.

With the development of new techniques and technologies are increasing the possibility of experimental research on a range of non-invasive methods and methods for understanding the structure of current and local values , especially vector velocity and density. Experimental methods, similarly like numerical methods have developed in a separate area of knowledge and it is necessary to pay them adequate attention.

Haidl, J., Mařík, K., Moucha T., Rejl, F. J.,Valenz, L., Zedníková, M. (2021). Hydraulic characteristics of liquid–gas ejector pump with a coherent liquid jet. Chemical Engineering Research and Design, 168(April), 435-442. Messa, G., Malin, M., Matoušek, V. (2021). Parametric study of the beta-sigma two-fluid model for simulating fully suspended slurry flow: Effect of flow conditions. Meccanica. 56(5), 1047-1077.

Skalák, Z. (2021). An optimal regularity criterion for the Navier–Stokes equations proved by a blow-up argumentNonlinear Analysis: Real World Applications58(April), 103207.

Kolář, V., Šístek, J. (2020). Consequences of the close relation between Rortex and swirling strength. Physics of Fluids. 32, 91702.

Messa, G. V., Matoušek, V. (2020). Analysis and discussion of two fluid modelling of pipe flow of fully suspended slurryPowder Technology360(January), 747-768.

Matoušek, V., Kesely, M., Chára, Z. (2019). Effect of pipe inclination on internal structure of settling slurry flow at and close to deposition limit. Powder Technology. 343(February), 533–541.

Šulc, R., Ditl, P., Jašíková, D., Kotek, M., Kopecký, V., Kysela, B. (2019). The effect of Particle Image Velocimetry setting parameters on local velocity measurements in an agitated vessel. Chemical Engineering & Technology. 42(4), 827–834.

Guo, Z., Kučera, P., Skalák, Z. (2018). Regularity criterion for solutions to the Navier–Stokes equations in the whole 3D space based on two vorticity components. Journal of Mathematical Analysis and Applications. 458(1), 755–766.

Matoušek, V., Krupička, J., Kesely, M. (2018). A layered model for inclined pipe flow of settling slurry. Powder Technology. 333(June), 317–326.

Guo, Z., Caggio, M., Skalák, Z. (2017). Regularity criteria for the Navier–Stokes equations based on one component of velocity. Nonlinear Analysis: Real World Applications. 35, 379–396.

Zych, M., Hanus, R., Vlasák, P., Jaszczur, M., Petryka, L. (2017). Radiometric methods in the measurement of particle–laden flows. Powder Technology. 318, 491–500.

  • KalKal – sludge calculator
The software solves the relationship between two basic variables - hydraulic gradient [m/m] and mean flow velocity [m/s] in a pipe flows. The software allows a variety of approaches ranging from semi-empirical to those with significant physical description to be used for calculations in both laminar and turbulent flow regimes. The results are presented in the form of (H-Q) pipe characteristics. The characteristics and efficiency of the pump(s) can then be plotted against the pipeline characteristic in the form of polynomial with user defined degree.