CFD becomes an everyday tool in the development process of water turbines and pumps. The development of new models for steady state and unsteady calculations is very fast, but unfortunately some procedures in the development process are still very time-consuming. Some special numerical analysis takes more than a month of the CPU time although a huge number of processors are used. Hereafter are presented some new ideas on how computational time for steady state and unsteady calculations for incompressible fluids can be reduced by orders of magnitude for some particular cases. In the development process of new hydraulic turbines when high energetic and cavitation characteristics are expected, usually a huge number of different geometries and a lot of operating regimes should be analysed. To obtain accurate results the mesh needs to follow some quality criteria and should be fine enough. Considering all above mentioned facts, the computational time can be a bottleneck for efficient accomplishment of industrial projects.
COBISS.SI-ID: 26520615
The paper presents an experimental study of suspension flow patterns and velocity field inside two types of circular settling tanks with continuous operation. The two tanks differ in inlet- and outlet configurations. Research was focused on the influence of flow field on the sedimentation efficiency of both settling tanks. Experiment was carried out on a settling tank sections made of plexi-glass that represented radial slices of prototype circular settling tanks. Kinematic flow properties inside settling tank sections were determined by computer-aided visualization in order to analyse the whole instantaneous flow field at once. Sedimentation efficiency was assessed by measurements of inlet- and effluent suspension concentrations. Pronounced density current evolved in both tanks, which under certain conditions enhanced sedimentation. Flow field showed qualitative changes during operation and proved to be significantly dependent on average suspension density in the inner chamber of the settling tank. Some important properties of the flow field could also be reconstructed from the spatial distribution of the remaining sludge. Centrally fed settling tank with peripheral effluent generally performed better in terms of sedimentation efficiency mainly due to insufficient height of the effluent baffle in the peripherally fed settling tank.
COBISS.SI-ID: 12106523
A visualization method was employed for accurate non-intrusive measurement of velocity fields at a physical model of a sharp-crested rectangular sideweir under subcritical flow. The experimental observation of velocity vectors at various horizontal planes over the entire width of the main channel confirms that the flow conditions at sideweir are non-uniform. The coefficients of non-uniform velocity distribution were in the range from 1 to 1.1. The present study focuses on the relation between the longitudinal components of the overflow velocities and the corresponding cross-sectional average velocities in the main channel, detailed as a function of flow depth and of location along the sideweir crest. For different sideweir geometries, these coefficients varied between 1 and 1.2.
COBISS.SI-ID: 12227611
This paper presents a non-contact method for velocity field calculation from a series of images containing illuminated planar layer of fluid with a pollutant mixed in.Velocity field is calculated using a model similar to optical flow based on the advection-diffusion equation.The model which was also implemented into our software, ADM flow, is evaluated on different sets of synthetic images.Calculated velocity fields are in a good agreement with the true velocity fields, mostly deviating by less than 10 % in magnitude and 1° in flow direction.
COBISS.SI-ID: 13484571
This paper presents a non-contact method for velocity field calculation from a series of fluid flow images with illuminated planar layer of the flow and a mixed-in pollutant for flow visualization. The velocity field is calculated using a model similar to optical flow that is based on the advection-diffusion equation. The model is evaluated using a set of synthetic airfoil flow visualization images generated by a combination of computational fluid dynamics and inverse advection-diffusion equation approaches. The calculated velocity fields are in a good agreement with the true velocity fields.
COBISS.SI-ID: 13570587