The aim of this study is to examine different blowing configurations of
 multiple swirling jets for use it in terminal units of ventilation
 applications. The influence of several parameters such as the inclined vanes
 of diffuser and the sense of rotation of the single or multiple swirling
 jets, their number and their arrangement on the flow resulting dynamically
 and thermally is experimentally investigated. Flow rate was adjusted at
 Reynolds numbers, Re0, ranging from 104 to 30.103. The current study is
 carried out under uniform heat flux condition for each diffuser at Reynolds
 number of 30.103, the air being the working fluid. Experiences concerning the
 fusion of several jets show that the resulting jet is clearly more
 homogenized under swirling influence. The findings of this study show that
 the gap between the jets and their sense of rotation relative to the central
 jet, affects the quality of the homogenization of ambiance. Among the studied
 different configuration, the one which consists of a swirling central jet
 controlling the behavior of six swirling jets in counter-rotation is shown to
 be the most effective in terms of thermal destratification.

/pdf/improvement-of-thermal-homogenization-using-multiple-1ydx327veu.pdf

Improvement of thermal homogenization using multiple swirling jets

Laser-Doppler anemometry application in measurements of the 3-D swirl turbulent flow velocity in the cylindrical pipe, behind the axial fan, have been analysed. This paper presents a brief overview of uncertainty sources in the laser-Doppler anemometry measurements. Special attention is paid to estimation of laser-Doppler anemometry measuring volume positioning in cylindrical pipe flow due to optical aberrations, caused by the pipe wall curvature. The hypothesis, that in the central part of the pipe (r/R < 0.6) exists a small, or negligible pipe wall influence on laser-Doppler anemometry measuring position, is investigate. The required corrections, for measurements of axial, tangential, and radial velocity components such: shift of measuring volume and its orientation are analysed and determined for used test rig and for some other pipe geometries.

/pdf/estimation-of-laser-doppler-anemometry-measuring-volume-3whzbp4g7g.pdf

Estimation of laser-Doppler anemometry measuring volume displacement in cylindrical pipe flow

This review paper provides data about research activities at the School of the turbulent swirling flow at the Faculty of Mechanical Engineering, University of Belgrade, conducted in the period 1941 up to date. An overview is provided of the main directions in this research area. First papers dealt with the turbulent swirling flow in hydraulic turbines to be continued by the experimental and analytical approaches on the axial fans pressure side. The complexity of 3-D, non-homogeneous, anisotropic turbulent velocity fields required complex experimental and theoretical approach, associated with the complex numerical procedures. Analytical approaches, complex statistical analyses and experimental methods and afterwards CFD employed in the research are presented in this paper. The 150 scientific papers, numerous diploma works, several master of science (magister) theses, six Ph. D. theses and two in progress, 40 researchers, national and international projects are the facts about the School. Scientific references are chronologically presented. Numerous abstracts from scientific conferences, presentations, projects with industry and lectures are not given here.

/pdf/the-school-of-the-turbulent-swirling-flow-at-the-faculty-of-3v18ov7qco.pdf

The school of the turbulent swirling flow at the Faculty of Mechanical Engineering University of Belgrade

Hydraulic losses in the region between the guide vanes and runner of a Kaplan turbine are commonly either neglected or considered a part of the total guide vanes losses. This paper focuses on the determination of these losses for a relevant range of operating modes of the Kaplan turbine model. The research was performed by numerical simulations using two turbulence models, wherein some of the results were validated by the available experimental data. The impact of swirl flow parameters, defined for referent inlet of the researched vaneless passage, on the hydraulic losses was considered. Based on the numerical and experimental results, a novel formula for determination of these losses is proposed. The contribution of the studied losses to the total turbine losses is also identified.

Determination of hydraulic losses in the flow passage between the guide vanes and runner of the Kaplan turbine

Velocity Distribution in an Annular Diffuser Fitted with Twisted Hub for Different Area Ratios

Results of the theoretical and experimental investigations of the turbulent mean swirl flows characteristics change along straight conical diffuser of incompressible fluid (air) are presented in this paper. The main swirl flow characteristics review is given. In addition: the specific swirl flow energy, the energy loss, the mean circulation, the swirl flow parameter, the ratio between the swirl and axial flow loss coefficients change along the diffuser are presented. Among other values: the Boussinesq number, outlet Coriolis coefficient and swirl flow loss coefficient dependences on inlet swirl flow parameter are also given. The swirl flow specific energy and outlet Coriolis coefficient calculation procedure are presented in this paper, as well as experimental test bed and measuring procedures. The swirl flow fields were induced by the axial fan impeller. Various swirl parameters were achieved by the impeller openings and rotational speeds.

/pdf/investigation-of-the-turbulent-swirl-flows-in-a-conical-1lydilnhb8.pdf

Investigation of the turbulent swirl flows in a conical diffuser

Results of experimental investigations of the turbulent swirl flow in three straight conical diffusers with various diffuser total angles are presented in this paper.   All three diffusers have the inlet diameter 0.4 m and total divergence angles 8.6°, 10.5° and 12.6°. The incompressible swirl flow field is generated by the axial fan impeller, and for each diffuser several regimes were achieved by changing rotation number. Original classical probes were used for measurements. The distributions of the average main swirl flow characteristics along the diffuser are shown. Distributions of the inlet Boussinesq number, outlet Coriolis coefficient, ratio of the swirl and completely axial flow loss coefficients at conical diffuser on the inlet swirl flow parameter are also presented.

/pdf/experimental-investigations-of-the-turbulent-swirl-flow-in-12otmyfyyg.pdf

Experimental investigations of the turbulent swirl flow in straight conical diffusers with various angles

Fluid flow in curved channels with various cross-sections, as a common problem in theoretical and applied fluid mechanics, is a very complex and quite undiscovered phenomenon. Defining the optimum shape of the fluid flow boundaries, which would ensure minimum undesirable phenomena, like "dead water" zones, unsteady fluid flow, etc., is one of the crucial hydraulic engineering’s task. Method of kinetic balance is described and used for this purpose, what is illustrated with few examples. .

/pdf/fluid-boundaries-shaping-using-the-method-of-kinetic-balance-9b7i8a8j93.pdf

H Miroslav Benisek

Papers

Investigation of the turbulent swirl flows in a conical diffuser

The school of the turbulent swirling flow at the Faculty of Mechanical Engineering University of Belgrade

Experimental investigations of the turbulent swirl flow in straight conical diffusers with various angles

Fluid boundaries shaping using the method of kinetic balance