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EN
Based on the analysis of typical operating modes of modern high-speed trains and transport aircraft, the influence of various schemes of surface relief modification and blowing through it on aerodynamic drag has been thoroughly investigated. A set of several schemes of the combined effect of these two factors is proposed to create an easy-to-use, cheap-to-produce streamlined surface of the desired structure with a reliable and controllable effect of active influence on aerodynamic drag reduction. The potential effect of reducing aerodynamic drag has been verified by numerical and Particle Image Velocimetry experimental modeling. The proposed technological innovations are encouraging and relevant; by reducing energy costs, they increase the commercial and environmental attractiveness of their implementation.
EN
The article presents a laboratory stand for direct measurement of the thrust generated by the undulating propulsion system of a biomimetic underwater vehicle. The laboratory water tunnel enables research and comparison of the generated thrust with the results of the fin and fluid interaction analysis using the Particle Image Velocimetry method. The water tunnel is equipped with an industrial camera for recording changes in the position of markers highlighted with a line laser in the area of analysis. The comparison of the results obtained by the PIV method with the industrial force sensor allows for the analysis of the efficiency of the biomimetic propulsion system as a function of both design and control parameters.
PL
W artykule przedstawiono stanowisko laboratoryjne do bezpośredniego pomiaru naporu generowanego przez napęd falowy biomimetycznego pojazdu podwodnego. Stanowisko umożliwia przeprowadzenie badań i porównanie generowanego naporu z wynikami analizy interakcji płetwy i płynu z wykorzystaniem metody PIV. Stanowisko wyposażone jest w kamerę przemysłową do rejestrowania zmiany położenia markerów podświetlonych liniowym laserem w obszarze analizy. Porównanie wyników uzyskanych metodą PIV z przemysłowym czujnikiem siły pozwala na analizę sprawności biomimetycznego układu napędowego w funkcji zarówno parametrów konstrukcyjnych jak i sterujących.
EN
Purifying air from dust is a very important, current topic. There are many methods to minimize the amount of dust, one of them being chamber filters. This paper presents the research results of a newly designed rectangular chamber filter. The efficiency of the dedusting process is influenced by contamination properties, but also by the construction of the apparatus, inlet, and outlet location, the ratio of certain dimensions, and the gas flow rate. The airflow containing solid particles is a multi-phase, difficult-to-describe issue, therefore an attempt to determine the trajectory of particle movement in the apparatus was carried out using the PIV method. A decrease in the dedusting efficiency was observed with the increase of the gas flow rate, as well as for smaller diameters of the solid particles. The obtained values of the efficiency of the apparatus are comparable with the values obtained for the constructions discussed in other papers.
EN
The PIV (Particle Image Velocimetry) method is one of the optical, non-invasive measurement methods for measuring fluid velocity and it can be used in the study of two-phase gas-liquid flows to determine velocity fields. The velocity distribution of the liquid and gas phases influences the formation of two-phase flow structures and, consequently, the mechanisms of energy and moment exchange in the two-phase flow. The article concerns the application of the PIV method in the assessment of hydrodynamic phenomena occurring during two-phase flow realized in pipe minichannels with internal diameters d > 2 mm. Fluorescent marker particles with a density close to that of water were used in the research. The preliminary tests were carried out on the adiabatic water-air mixture. The research aimed to check the applicability of PIV methods also in non-adiabatic flows. As a result of preliminary studies, the velocity maps of the liquid phase, histograms and velocity profiles in the vertical section of the minichannel tested were obtained.
EN
This paper presents a quick-and-dirty method to assess the risk of negative aeration effects occurring in twin-tube hydraulic shock absorbers used in passenger cars at the early design stage. The method is intended to be implemented as an engineering calculation tool based on the computational fluid dynamics (CFD) two-dimensional (2D)/three-dimensional (3D) steady-state single-phase model. The CFD model was previously validated with the use of the particle image velocimetry (PIV) experiment. The negative aeration effect is a wellknown issue for automotive and railway shock absorbers manufacturers. It results in uncontrolled on-vehicle vibrations and the deteriorated shock absorber damping characteristic. The major aeration contributor in twin-tube hydraulic shock absorbers is the sliding shim intake valve, which requires design optimization to avoid a negative aeration effect. The method validation was conducted with the customized test rig equipped with a transparent cylinder where the specific sliding intake valve was assembled. The proposed method also requires a lumped-parameter model of a twin-tube shock absorber, which allows to simulate boundary conditions in assessing particular reservoirs of a shock absorber, i.e., pressures and flow balance. The method is implemented as a calculation routine that converts CFD pressure regions into a gas concentration indicator (GCI) using the pressure-density characteristic of an oil-gas emulsion of a shock absorber. GCI is calculated based on the sum of particular 2D/3D grid elements. The method application is to minimize the risk of occurrence of negative aeration effects by avoiding expensive and time-consuming experimental tests. This method can also be used for in-production shock absorbers projects as a part of a continuous improvement cycle or in the case of inefficient shock absorbers claimed by a vehicle manufacturer. The application scope of the method can be extended for arbitrary twin-tube designs of shock absorbers in the automotive and railway industries.
EN
Computational Fluid Dynamics (CFD) predictions are becoming an industry standard. They allow for making accurate predictions of complex problems without requiring extensive real-world testing, as well as saving time and money. However, it has been proven many times that the classic Reynolds-averaged Navier – Stokes (RANS) approach has its flaws and fails to provide highly accurate predictions. Even though CFD only approaches a physical solution, which can be reached only in very specific applications, it usually provides enough precision for engineering purposes. To reach a convergence with real-world physics, plenty of factors must be taken into consideration like mesh, boundary conditions, and turbulence models. In order to obtain a CFD simulation that accurately represents real physics, some kind of real-world validation must take place. For aerodynamics, it is usually done in wind tunnels, which are expensive to run but provide controllable conditions to match those specified in CFD. One of the many methods used to validate the calculations is Particle Image Velocimetry (PIV). This study tries to validate CFD of a Formula Student car using PIV, but in real-world conditions, without wind tunnel. The compact size of equipment required for PIV testing and flexibility of CFD boundary conditions allow for that.
PL
Prognozy obliczeniowej dynamiki płynów (CFD) stają się standardem branżowym. Pozwalają na dokładne przewidywanie złożonych problemów bez konieczności przeprowadzania rozległych testów w warunkach rzeczywistych, oszczędzając czas i pieniądze. Jednak wiele razy zostało udowodnione, że klasyczne podejście Reynoldsa uśrednione Navier-Stokes (RANS) ma swoje wady i nie zapewnia bardzo dokładnych prognoz. Mimo że CFD zbliża się tylko do rozwiązania fizycznego i może osiągnąć je tylko w bardzo specyficznych zastosowaniach, do celów inżynieryjnych zwykle zapewnia wystarczającą precyzję. Aby osiągnąć zbieżność z rzeczywistą fizyką, należy wziąć pod uwagę wiele czynników, takich jak siatka, warunki brzegowe i modele turbulencji. Aby mieć symulację CFD, która dokładnie odzwierciedla rzeczywistą fizykę, musi nastąpić pewnego rodzaju walidacja w prawdziwym świecie. Zwykle odbywa się to w tunelach aerodynamicznych, jeśli mówimy o aerodynamice, które są drogie w eksploatacji, ale zapewniają kontrolowane warunki, aby dopasować się do tych określonych w CFD. Jedną z wielu metod stosowanych do walidacji obliczeń jest Velocymetria obrazu cząstek (PIV). To badanie próbuje zweryfikować CFD samochodu Formula Student przy użyciu PIV, ale w rzeczywistych warunkach, bez tunelu aerodynamicznego. Umożliwiają to kompaktowe rozmiary sprzętu wymaganego do testów PIV i elastyczność warunków brzegowych CFD.
EN
This paper presents a study on the multi-creteria decision making in the external cylindrical grinding process of 65G steel. An aluminum oxide grinding wheel was used in the experimental process. The experimental matrix was designed according to the Taguchi method with twenty-seven experiments. Five parameters were used to design the experimental matrix including workpiece velocity, feed rate, depth of cut, dressing feed rate, and dressing depth of cut. The surface roughness and Material Removal Rate (MRR) were determined for each experiment. This is the first time that the Weighted Aggregates Sum Product ASsessment (WASPAS) and Proximity Indexed Value (PIV) methods were used to make the multi-criteria decision for grinding process. The weighs of ouput criteria (surface roughness and MRR) were determined by Entropy method. Both WASPAS and PIV methods determined an experiment that simultaneously ensured the “minimum value” of surface roughness and “maximum value” of MRR.
EN
In this study, TOPSIS and PIV methods were applied for multi-criteria decision making in hard turning process. Experiments have been conducted in accordance with an experimental matrix designed by the Taguchi method with a total of twenty-seven experiments. At each experiment, the values of coolant concentration, nose radius, coolant flow, cutting velocity, feed rate and depth of cut have been changed. Surface roughness, flank wear and roundness error have been selected as output criteria. The weights of criteria have been determined by three methods, inclusive of Equal weight, ROC weight and Entropy weight. The combination of multi-criteria decision-making methods with three weighting methods gives six ranking options of the experiments. The purpose of ranking the experiments is to find the experiment at which the three output parameters are ensured to have the minimum value simultaneously.
PL
Metoda PIV (Particle Image Velocimetry) jest jedną z optycznych, nieinwazyjnych metod pomiarowych służących pomiarowi prędkości płynów i może być wykorzystywana w badaniach przepływów dwufazowych gaz-ciecz w celu wyznaczania pól prędkości. Rozkład prędkości fazy ciekłej i gazowej wpływa na formowanie się struktur przepływu dwufazowego, a w konsekwencji na mechanizmy wymiany energii i momentu w przepływie dwufazowym. Artykuł dotyczy zastosowania metody PIV do oceny zjawisk hydrodynamicznych zachodzących podczas przepływu dwufazowego realizowanego w minikanałach rurowych o średnicy wewnętrznej d > 2 mm. W badaniach zastosowano fluorescencyjne cząstki znacznikowe o gęstości zbliżonej do gęstości wody. Badania wstępne wykonano na mieszaninie adiabatycznej typu woda-powietrze. Celem badań było sprawdzenie możliwości zastosowania metod PIV również w przepływach nieadiabatycznych. W wyniku badań wstępnych otrzymano mapy prędkości fazy ciekłej, histogramy i profile prędkości w przekroju pionowym badanego minikanału.
EN
The PIV (Particle Image Velocimetry) method is one of the optical, non-invasive measurement methods for measuring fluid velocity and can be used in the study of two-phase gas-liquid flows to determine velocity fields. The velocity distribution of the liquid and gas phases influences the formation of two-phase flow structures and, consequently, the mechanisms of energy and moment exchange in the two-phase flow. The article concerns the application of the PIV method to the assessment of hydrodynamic phenomena occurring during two-phase flow realized in pipe minichannels with an internal diameter d > 2 mm. Fluorescent marker particles with a density close to that of water were used in the research. The preliminary tests were carried out on the adiabatic water-air mixture. The research aimed to check the applicability of PIV methods also in non-adiabatic flows. As a result of preliminary studies, velocity maps of the liquid phase, histograms and velocity profiles in the vertical section of the tested minichannel were obtained.
EN
Propeller cavitation is a main source of fluctuating pressure and noise induced by propellers, and the tip vortex cavitation is the principal source. The present study measures the flow fields near the blade tip using the 2D-PIV technique. The experimental setup and scheme are introduced. We monitor the process of generation and shedding of the propeller tip vortex in real time and analyse the dynamic structure of the tip vortex by testing the propeller wake field under different phases of the axial plane. The distribution characteristics of radial and axial velocity are also analysed. The influence range and the vorticity of the tip vortex and trailing vortex are obtained. All of the measured quantitative data are useful for future propeller design.
11
Content available remote Rozkład prędkości przepływu w obszarze sondy anemometru z falą cieplną
PL
W pracy przedstawiono badania pola prędkości wokół trójwłóknowej sondy termoanemometrycznej stosowanej do pomiaru prędkości przepływu metodą fal cieplnych. Porównano wartości prędkości wyznaczone za pomocą metody fal cieplnych ze zmierzonymi metodą PIV. Badania przeprowadzono w tunelu aerodynamicznym zamkniętym, w zakresie prędkości przepływu powietrza od 15 do 40 cm/s. Do badań zastosowano sondę termoanemometryczną trójwłóknową, o włóknach wzajemnie równoległych, umieszonych poziomo i zorientowanych prostopadle względem wektora prędkości przepływu. Zgodnie z przewidywaniami zaobserwowano występowanie zjawiska cienia aerodynamicznego w całym obszarze sondy, które sprawia, że zmierzone wartości prędkości są wyraźnie mniejsze od prędkości napływu. Porównano podłużne profile prędkości zmierzone metodą PIV z wartościami wyznaczonymi metodą fal cieplnych. Prędkość przepływu na drodze pomiędzy detektorami fali wyznaczona metodą fal cieplnych jest zbliżona do średniej wartości prędkości wyznaczonej metodą PIV. Natomiast prędkość na drodze od nadajnika fali do pierwszego detektora wyznaczona metodą fal cieplnych jest wyraźnie mniejsza od wartości wyznaczonej metodą PIV. Wynika to z różnicy faz pomiędzy napięciem a prądem na nadajniku fali temperaturowej. Uzyskane na obecnym etapie wyniki nie pozwalają na opracowanie efektywnej metody korekcji wpływu zjawiska cienia aerodynamicznego na wyniki pomiarów falą cieplną.
EN
The paper presents tests of the velocity field around the triple thin wire probe used to measure the flow velocity with the thermal waves method. Velocity values determined using the thermal wave method were compared to those achieved with the PIV method. The tests were carried out in a closed circuit wind tunnel, in the range of air flow velocity ranging from 15 to 40 cm/s. A three thin wire probes with mutually parallel wires, horizontally placed and oriented perpendicularly to the flow velocity vector was used for the tests. As expected, the velocity wake phenomenon was observed throughout the probe area, which means that the measured velocity values are clearly lower than the inflow velocity. The longitudinal velocity profiles measured with the PIV method were compared to the values determined with the thermal wave method. The value of flow velocity on the distance between the wave detectors determined with the thermal wave method is similar to the average velocity value determined with the PIV method. However, the velocity within the area between the wave emitter and the first detector determined with the thermal wave method is clearly lower than the value determined with the PIV method. This is due to the phase lag between voltage and current at the wave transmitter. The results obtained at this stage do not allow for the development of an effective method of correcting the effect of the wake on the results of thermal wave measurements.
PL
W artykule zaprezentowano badanie doświadczalne z dziedziny wentylacji, przeprowadzone w Małopolskim Laboratorium Budownictwa Energooszczędnego z wykorzystaniem metody Stereo Particle Image Velocimetry (Stereo PIV). Opisano wyposażenie laboratorium badawczego obejmujące system PIV, a także metodę. Zaprezentowano wstępne wyniki doświadczeń ze strumieniami powietrza wypływającego z nawiewnej kratki wentylacyjnej, stosowanej w typowym budownictwie mieszkaniowym.
EN
The article presents an experimental study in the field of ventilation, carried out in the Malopolska Laboratory of Energy Efficient Buildings. Stereo Particle Image Velocimetry (Stereo PIV) method was used in the experiment. The specification of the equipment of the research laboratory including the PIV system was included, as well as a brief description of the method. Preliminary results of the tests of the air stream flowing out of the ventilation grille used in typical housing construction have been presented.
PL
Przedstawiono wybrane prace pomiarowe pól prędkości wiatru wykonane za pomocą systemu PIV (Particle Image Velocimetry) w Laboratorium Inżynierii Wiatrowej Politechniki Krakowskiej. Podano zasady pomiaru, scharakteryzowano główne elementy systemu oraz opisano podstawowe zalety i trudności realizacji pomiarów taką techniką. Określono podstawowe obszary badawcze inżynierii wiatrowej, w których pomiary tą techniką mogą mieć praktyczne zastosowania.
EN
The article presents chosen measurement works of wind velocity fields by means of a PIV system (Particle Image Velocimetry) fulfilled in Wind Engineering Laboratory of Cracow University of Technology. The principles of PIV system measurement are presented, the main elements of the system are characterised and fundamental advantages and difficulties of a measurement execution by this type of a technique are described. The basic research fields of wind engineering are defined, in which the measurements of this technique could have practical applications.
EN
The elimination of hazards caused by cavitation phenomena is an important issue to be considered in the design of process equipment including flow machinery. These hazards are: cavitation erosion, efficiency decrease as well as vibration and noise. One of the most intensive and dangerous forms of cavitation is vortex cavitation that accompanies the operation of hydraulic machines in which components comprised of rotating blades are applied. Velocity fields around cavitation vortices generated by the model of a propeller blade were experimentally studied in a cavitation tunnel. Flow images were recorded using a high-speed camera and processed using particle image velocimetry (PIV) complemented with computer-aided techniques that had been developed for the purpose of this research. These techniques included the removal of image distortions on the basis of a calibration mask, determination of instantaneous velocity distributions and removal of air-bubble traces from flow images. Experimental studies result examples were presented in the form of velocity fields determined in the longitudinal plane as well as in three transverse planes remote from the blade. Instabilities of the cavitating vortex stream and of the local liquid-flow velocity in its surrounding were detected. The effect of the angle of attack of propeller blade on the instability of the vortex stream and the effect of the presence of the cavitating vortex kernel on the local velocities of the surrounding liquid, were determined.
EN
In order to improve the performance of the shell and tube heat exchanger, a porous baffle and a splitter bar are employed in this research. Through the arrangement of the porous baffle in the tube-side inlet and the splitter bar in the tube, the flow distribution of liquid in the heat exchanger is improved. PIV technology is used to investigate the unsteady flow in the tube-side inlet and the outlet of different models. The porous baffle significantly improves the flow of fluid in the shell and tube heat exchanger, especially by eliminating/minimizing the maldistribution of fluid flow in the tube-side inlet. The performance of the arc baffle is better than that of the straight baffle. The splitter bar has a minimal effect on the flow field of the tube-side inlet, but it effectively improves the flow in the tube bundle and restrains the vortex generation in the tube-side outlet.
PL
W artykule przedstawiono podstawy metody pomiarowej Particle Image Velocimetry (PIV), stosunkowo nieinwazyjnej techniki wyznaczania pól prędkości płynów. Podjęto próbę nakreślenia stanu badań oraz ich implementacji w Polsce. Opisano możliwości zastosowania metody PIV w różnych dziedzinach nauki i przemysłu, m.in. do badania przepływów powietrza w pomieszczeniach. Zwrócono uwagę na ich wpływ na parametry klimatu wewnętrznego i komfort pomieszczeń. Stwierdzono związek pomiędzy poprawnością i użytkowalnością instalacji wentylacyjnych, klimatyzacyjnych i grzewczych a efektywnością energetyczną budynków. Zawarty w artykule przegląd literatury światowej potwierdza duży potencjał metod PIV w mechanice płynów i związanych z nią gałęziach przemysłu.
EN
The article presents the basics of measuring method Particle Image Velocimetry (PIV), a relatively non-intrusive technique for determining fluid velocity fields. An attempt was made to outline the state of research and implementation of these research in Poland. The possibilities of applying the method in the fields of science and industry are described in examples for the study of indoor airflows were characterized. It was pointed out on their impact on the indoor climate parameters and indoor comfort. A relationship was found between the correctness and usability of ventilation, air conditioning and heating systems and the energy efficiency of buildings. Contained in the article the review of world literature seems to confirm the great potential of PIV methods in fluid mechanics and connected with it branches of industry.
EN
Shell-and-tube heat exchangers are widely used in chemical and process engineering. Assessing hydrodynamics of fluid flow in their shell-side is a highly complex task. This results from the complex geometry of the shell-side itself, defined by such parameters as the tubesheet layout, tube diameter, baffle spacing or baffle cut. Shell-and-tube heat exchangers are the subject of many studies in which design and flow parameters are analysed. However, only a few studies concentrate on issues strictly related to the identification of streams of the liquid flowing in the shell-side of apparatus on an industrial scale. In this article, the authors present the results of an experimental visualization study, utilizing Particle Image Velocimetry (PIV). The experiment used a laser sheet technique along and across a tube bundle. The main results of the measurements and analyses concentrate on identifying the flow pattern of streams in the shell-side and assessing stagnation vortices and their consequences. Finally, detecting bypass streams and leakage streams flowing through design gaps between the shell and the tube bundle as well as between the baffles and the tubes in the bundle are presented.
18
PL
Przedstawiono wyniki pomiarów naprężeń turbulentnych powstających w cieczy w pobliżu mieszadła Rushtona. Stwierdzono, że naprężenia turbulentne osiągają największe wartości w pobliżu końców łopatek mieszadła. Poza niewielkim obszarem w pobliżu mieszadła wartości naprężeń turbulentnych szybko zmniejszają się.
EN
The paper presents measurement results of turbulent stresses occurring in liquid near the Rushton impeller. It was found that turbulent stresses reached the highest values near impeller blades tips. Outside the small area near the impeller, the turbulent stresses values quickly decreased.
EN
The paper presents the use of the PIV method in experimental studies on the speed distribution of oil particles contained in oil mist delivered into a cutting zone with minimum quantity (MQL). During investigations an orthogonal sample was of an aluminum alloy PA7N was machined using HS18-0-1 high-speed steel cutter. The oil mist was delivered into the cutting zone by a single spray nozzle directed at the tool rake surface. Two angular settings of the spray nozzle were applied in relation to the surface of the machined sample. Based on the images obtained by the PIV method, the distribution of the oil particles in the cutting area was determined according to the setting the spray nozzle. Studies have indicated more favorable conditions for the delivery of oil mist at the angle of spray nozzle at 85°. These conclusions were confirmed by measuring the cutting force in tangential direction to the machined surface.
PL
Ruch złoża jest podstawowym parametrem opisującym procesy zachodzące w aparatach bębnowych. Wzrokowa ocena oraz analiza statycznych obrazów uniemożliwia określenie charakterystycznych stref w ruchomym złożu. W programach typu PIV wyznaczane są lokalne pola prędkości cząstek co umożliwia zdefiniowanie ch arakterystycznych stref, a tym samym stanów zachowania się złoża. Dodatkowo an alizując wektory prędkości można określić silę z jaką cząstki opadają na złoże, co ma istotne znaczenie w wielu procesach przemysłowych, np. mieleniu.
EN
The movement of bed is a basic parameter describing the processes occurring in rotating drums. Visual assessment and analysis of static images does not identify the characteristic areas in the moving bed. The PIV programs determine velocity fields of particles which allow one to define the characteristic areas and thereby the states behavior of the bed. In addition, analysis of velocity vectors allows one to determine the force with which the particles fall on the bed, which has a significant meaning in many industrial processes, e.g. grinding.
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