This paper analyses the effects produced by a plasma actuator on flow around a turbine blade profile at Re 7600 and Re 10500. The analysis is undertaken with flow visualizations. The experiments indicate that for low Reynolds number plasma has a significant influence on flow around the blade and that the effects of actuation depend on power added to flow and relative distance between the electrode and the separation line of the actuator.

This paper describes porous rotors manufactured from open cell aluminium foam. Rotor construction and theoretical description of fluid flow through rotating porous material are presented. Nine porous rotors made of materials with three different average pore sizes, with or without inducer, three rotor heights and two inlet diameters were selected and compared to a classical rotor with blades. Measurements involved two parts, measurement of pressure drop on non-rotating rotors while integral flow characteristics were measured on rotating rotors. Pressure drops for selected rotors agree well with theoretically calculated values based on Darcy-Forchheimer equation and Ergun equation. Measurements of integral aerodynamic and acoustic characteristics for selected rotors are presented. At low volume flow rates porous rotors have lower aerodynamic efficiency, comparable dimensionless pressure and lower noise compared to classical rotors with blades.

The quality of the end product in mineral wool production depends on the fiberisation process on the spinning machine. An important process variable is the fluctuation of melt mass flow from the melter. A method for measuring melt mass flow, which is based on the measuring the diameter and flow velocity using computer-aided visualization is presented. The velocity of the molten jet onto the surface is measured by a method based on the advection diffusion equation. A sequence of successive flow images was processed to obtain the required unknown terms. Concentration of the passive tracer was acquired through the greyscale intensity on images at chosen measurement points. Standard numerical procedures were applied to obtain spatial- and time derivatives of the passive tracer concentration. The field measurements were performed by comparison with the weight of the final product. The agreement among field measured values and available comparison method is fair.

Flow field through rotating porous disc was investigated with experimental fluid dynamics and compared with computational fluid dynamics. Open cell aluminum metal foam with 88% porosity was used. On rotating porous disc, integral measurements of static pressure difference in dependence of air volume flow rate were performed. Local measurements of velocity profiles close to disc circumference were performed with hot-wire anemometry. The airflow visualization method using smoke generator and digital camera was performed. Flow structures through porous disc were visualized at three different air volume flow rates. Numerical simulation of homogenous rotating porous disc was performed. Experimental and numerical results were compared. The results showed appropriate comparison of integral and local properties. The presented experimental approach can be used for the investigation and understanding of flow field phenomena on rotating porous materials. The proposed conclusions can be applied for variable applications on rotating porous materials.

The article presents a simple method for the probabilistic assessment of frequency of landslides, which are large enough to evoke hazardous events on natural gas pipelines that cross the site prone to landslides. The mechanical part of the method comprises the calculation of maximum stresses and displacements. Results of the mechanical part are compared with the historical data in the probabilistic part of the in where ground movements due to landslides are treated as random events. The method is intended as a supplement to the models fir quantitative risk assessment on pipelines.

Axial fans often show adverse flow conditions at the fan hub and at the tip of the blades. In the present paper, a modification of conventional axial fan blades with experimental investigation is presented. Patented hollow blades were manufactured from the hub to the trailing edge at the tip of the blades. They enable the formation of self-induced internal flow through internal passages. The internal flow enters the internal radial flow passages of the hollow blades through the openings near the fan hub and exits through the trailing edge slots at the tip of the blade. The influence of internal flow on the flow field of axial fan and the modifications of aerodynamic characteristics of the axial fan have been studied along with recent patents. An experimental investigation of the interaction of two flows with the flow around hollow airfoil NACA series in a low-speed wind tunnel was studied. The determination of flow structure on the hollow airfoil was performed with computer-aided visualization. With the introduction of the internal flow and interaction with the external flow, a reduction of circulation effects on the fan hollow blade was achieved. The introduction of self-induced blowing led to the preservation of the direction of external flow, defined by blade geometry, and enabled maximal local energy conversion. Aerodynamic characteristic of the axial fan reached higher degree of pressure difference and efficiency through the entire fan working conditions. Keywords: Axial fan, hollow blade, aerodynamic characteristic, wind tunnel and computer-aided visualization

Axial fans often show adverse flow conditions at the fan hub and at the tip of the blades. In the present paper, a modification of conventional axial fan blades with numerical and experimental investigation is presented. Hollow blades were manufactured from the hub to the trailing edge at the tip of the blades. They enable the formation of self-induced internal flow through internal passages. The internal flow enters the internal radial flow passages of the hollow blades through the openings near the fan hub and exits through the trailing edge slots at the tip of the blade. The study of the influence of internal flow on the flow field of axial fan and the modifications of aerodynamic characteristics of the axial fan have been made. The numerical and experimental results show a comparison of integral and local characteristics of the axial fan with the internal flow, compared to characteristics of a geometrically equivalent fan without internal flow. The experimental results of local characteristics were performed with a five-hole probe and computer-aided visualization. A reduction of adverse flow conditions near the trailing edge at the tip of the blade was achieved, as well as boundary layer reduction on the blade suction side and the reduction of flow separation. The introduction of self-induced blowing led to the preservation of the direction of external flow, defined by blade geometry, and enabled maximal local energy conversion. The integral characteristic reached higher degree of efficiency.

The paper presents a study of the ability of the visualization methods to measure velocity field in the fluid flow from the concentration field of a passive tracer that is introduced to the fluid. The method is based on the advection diffusion equation. A sequence of successive flow images was processed to obtain the required unknown terms. Concentration of the passive tracer vas acquired through greyscale intensity on images at chosen measurement points. Standard numerical procedures were applied to obtain spatial- and time derivatives of the passive tracer concentration. The method was tested in all experiment with an air jet flowing out of a pipe, where the velocity field in a jet was measured with a hotwire anemometer. Comparison of the results of both methods shows good agreement, albeit with certain deviations that are a consequence of simplified approach of the visualization method. The results prove the suitability of the visualization method for quantitative measurements of flow kinematics. Further studies and improvements of the method could provide a simple and relatively cheap yet reliable tool not only for preliminary assessment of the flow velocity field, but also for velocity, measurements in complex flow structures. (c) 2009 Journal of Mechanical Engineering. All rights reserved.

Experimental investigation of the interaction of internal flow with external flow around hollow airfoil NACA series in a low-speed wind tunnel was conducted and is presented in the paper. The region near the trailing edge of the hollow airfoil was studied in detail and measurements of velocity and turbulence intensities were performed with hot-wire anemometry. Determination of flow structure on the hollow airfoil was performed with computer-aided visualization. It can be concluded from the measurement analysis that higher values of velocities, lower turbulence intensities and a significant decrease of circulation effects on the suction side of the hollow blade were achieved, due to the introduction of internal flow. The results obtained on the hollow airfoil were applied on the rotating axial fan. Influence of the internal flow of the hollow blade on the flow field of the axial fan was studied. With the introduction of the internal flow a reduction of circulation effects on the fan hollow blade was achieved. Aerodynamic characteristic of the axial fan reached higher degree of total pressure difference and normalized efficiency through the entire fan working conditions.

Axial fans often show adverse flow conditions at the fan hub and at the tip of the blades. Modification of conventional axial fan blades is presented. Hollow blades were manufactured from the hub to the trailing edge at the tip of the blades. Hollow blades enabled the formation of self-induced internal flow through internal passages. The internal flow enters the internal radial flow passages of the hollow blades through the openings near the fan hub and exits through the tip trailing edge slots. Study of the influence of internal flow on the flow field of axial fan and modifications of axial fan aerodynamic characteristics is presented. The characteristics of the axial fan with the internal flow were compared to characteristics of a geometrically equivalent fan without internal flow. The results show integral measurements of performance testing using standardized test rig, and the measurements of local characteristics. The measurements of local characteristics were performed with a hot-wire anemometry, five-hole probe and computer-aided visualization. We attained reduction of adverse flow conditions near the blade tip trailing edge, boundary-layer reduction on the blade suction side and reduction of flow separation. Introduction of the self-induced blowing led to the preservation of external flow direction, defined by blade geometry and enabled maximal local energy conversion. The integral characteristic reached higher degree of efficiency.

Axial fans often show adverse flow conditions at the fan hub and at the tip of the blade. The modification of conventional axial fan blade is presented. Hollow blade was manufactured from the hub to the tip. It enables the formation of self-induced internal flow through internal passages. The internal flow enters the passage of the hollow blade through the opening near the fan hub and exits through the trailing edge slots at the tip of the hollow blade. The study of the influence of internal flow on the flow field of axial fan and modifications of axial fan aerodynamic characteristics is presented. The characteristics of the axial fan with the internal flow were compared to characteristics of a geometrically equivalent fan without internal flow. The results show integral measurements of performance testing using standardized test rig and the measurements of local characteristics. The measurements of local characteristics were performed with a hot-wire anemometry and a five-hole probe. Reduction in adverse flow conditions near the trailing edge at the tip of the hollow blade, boundary-layer reduction in the hollow blade suction side, and reduction in flow separation were attained. The introduction of the self-induced blowing led to the preservation of external flow direction defined by the blade geometry, which enabled maximal local energy conversion. The integral characteristic reached a higher degree of efficiency.

Axial flow fan blades deform during operation due to the variousforces that act on them. That is why, we can ask ourselves about the influence of the blade deformation on the integral and local characteristics. In the paper we present a study of influence of axial flow fan blade deformation. The paper deals with measurements of the blade deformation at the known integral working conditions. Results - deformations of fan blade tip were used for numerical study of the influence of the changed blade form on the fan's aerodynamic characteristic. Fan integral characteristics were measured in accordance with the ISO-DIS 5801:2006 standard and were carried out on the wind tunnel of the Hidria Institute Klima, Godovic. Other measurements of the blade deformation were done on the measuring station on the Faculty of Mechanical Engineering, University of Ljubljana, with the help of computer aided visualization. Deformations were measured in three working points, which were defined with fan integral parameters. Results of the measurements helped to determine modified form of the blade, which was then used for the numerical simulation for the same fan integral parameters. The study of deformation influence, based on the numerical simulation, was carried out. (c) 2008 Journal of Mechanical Engineering. All rights reserved.

The paper presents a model for the assessment of the influence of line markers on risk on transmission pipelines with natural gas. The impact of line markers on risk is determined as a function of the line marker recognisability, which in turn depends on the ability to discern a line marker from a distance. The model is based on physical properties of line markers, especially on their colour, measures and the colour of the environment. These properties served to quantitatively assess the discernability of two most frequently encountered types of line markers. Calculated distances at which a particular line marker is discernible were compared to the average distances between two line markers. Risk reduction factors were derived from the comparison between the calculated results and the data from the appropriate hazardous event database. Results of the model indicated significant dependence of the risk reduction factor due to line markers on the distance between two line markers and the weather conditions. The model shows its flexibility through its distinct dependence on local conditions along the pipeline route. It can serve as a supplement to the existing models for quantitative risk assessment on pipelines used in natural gas transportation.

Lopatice ventilatorja se zaradi sil, ki delujejo nanje, med obratovanjem deformirajo. Stacionarne deformacije in fluktuacije lopaticnega vrha - temena - okoli ravnotezne lege omogocajo oceno obremenitve lopatice na lokaciji pritrditve - v korenu - in oceno vpliva deformacije na aerodinamske lastnosti ventilatorja. V prispevku je predstavljena metodologija merjenja deformacije lopatice aksialnih ventilatorjev, zasnovane na racunalnisko podprti vizualizaciji. Preizkus je bil izveden na aksialnem ventilatorju z osnovno in spremenjeno izvedbo vpetja lopatic. Merjenje je bilo opravljeno na za to namenjenem preizkusevaliscu na Fakulteti za strojnistvo Univerze v Ljubljani, kjer smo s kamero zajemali digitalizirane posnetke v izbranih casovnih intervalih. Deformacije ventilatorske lopatice so bile merjene v optimalni obratovalni tocki ventilatorja za oba opazovana primera vpetja lopatic. Na temenu profila lopatice so bili vrednoteni odmiki izbranih tock - markerjev - glede na referencno toeko na ohisju ventilatorja. V okolju programske opreme MatLab je bil izdelan program prepoznavanja markerjev in izracunavanja deformacij lopatic rotorja ventilatorja. Z razvito vizualizacijsko metodo je bila izvedena primerjalna analiza obeh nacinov vpetja lopatic v pestu ventilatorja. Potrjena je bila primernost uporabljene eksperimentalne metode, ki omogoca enostavno in zanesljivo zaznavanje deformacij rotorskih lopatic.