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1

Determination of the aerodynamic drag of pneumatic life rafts as a factor for increasing the reliability of rescue operations

Jachowski Jacek, Książkiewicz Edyta, Szwoch Izabela

Polish Maritime Research

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2021

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nr 3

128--136

EN

Ensuring the safety of ship crews at sea is of the utmost importance. Life rafts are one of the basic components of any seagoing vessel and ensuring their stability is an important component of maritime research. This study concerns the determination of the aerodynamic drag coefficients of pneumatic life rafts in a full range of wind speed and directions. The drag coefficients are based on full-scale experimental studies and numerical calculations (computational fluid dynamics) carried out with Flow-3D software. Two types of life rafts are analysed in the numerical simulations, namely, a non-deformed raft and a raft deformed under the influence of wind pressure at a given flow velocity. The shape of the deformed pneumatic life raft is recreated on the basis of photographic documentation from experimental studies. The results of the numerical calculations are verified on the basis of full-scale flow experiments carried out at the Low Speed Wind Tunnel T-3 Laboratory at the Institute of Aviation in Warsaw. This study shows that there is a dependence of aerodynamic drag on the degree of deformation of the above-water part of the life raft, as well as the angle of the raft setting to the wind. In real water conditions, this angle depends mainly on the anchor point of the drift anchor and therefore should be considered at the design stage, which will directly reduce the wind leeway of the raft.

2

Modeling of methane and air velocity behavior in an auxiliary ventilated coal heading

Daloğlu Gülnaz, Önder Mustafa, Parra Teresa

Archives of Mining Sciences

|

2021

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Vol. 66, no. 1

69--84

EN

It is commonly known that the cause of serious accidents in underground coal mining is methane. Thus, computational fluid dynamics (CFD) becomes a useful tool to simulate methane dispersion and to evaluate the performance of the ventilation system in order to prevent mine accidents related to methane. In this study, numerical and experimental studies of the methane concentration and air velocity behaviour were carried out. The experiment was conducted in an auxiliary ventilated coal heading in Turkish Hard Coal Enterprises (TTK), which is the most predominant coal producer in Turkey. The simulations were modeled using Fluent-Ansys v.12. Significant correlations were found when experimental values and modeling results were compared with statistical analysis. The CFD modeling of the methane and air velocity in the headings especially uses in auxiliary ventilation systems of places where it is hard to measure or when the measurements made are inadequate.

3

Feasibility study of RANS in predicting propeller cavitation in behind-hull conditions

Zhang Yuxin, Wu Xiao-ping, Lai Ming-yan, Zhou Guo-ping, Zhang Jie

Polish Maritime Research

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2020

|

nr 4

26--35

EN

The propeller cavitation not only affects the propulsive efficiency of a ship but also can cause vibration and noise. Accurate predictions of propeller cavitation are crucial at the design stage. This paper investigates the feasibility of the Reynolds-averaged Navier–Stokes (RANS) method in predicting propeller cavitation in behind-hull conditions, focusing on four aspects: (i) grid sensitivity; (ii) the time step effect; (iii) the turbulence model effect; and (iv) ability to rank two slightly different propellers. The Schnerr-Sauer model is adopted as the cavitation model. A model test is conducted to validate the numerical results. Good agreement on the cavitation pattern is obtained between the model test and computational fluid dynamics. Two propellers are computed, which have similar geometry but slightly different pitch ratios. The results show that RANS is capable of correctly differentiating the cavitation patterns between the two propellers in terms of the occurrence of face cavitation and the extent of sheet cavitation; moreover, time step size is found to slightly affect sheet cavitation and has a significant impact on the survival of the tip vortex cavitation. It is also observed that grid refinement is crucial for capturing tip vortex cavitation and the two-equation turbulence models used – realizable k-ε and shear stress transport (SST) k-ω – yield similar cavitation results.

4

Aerodynamic performance of a new double-flap wing sail

Li Dongqin, Zhang Yili, Li Peng, Dai Jingjing, Li Guohuan

Polish Maritime Research

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2019

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nr 4

61--68

EN

As a type of natural energy resource, wind power is used in the modern implementation of wind-assisted technologies as a method for reducing the fuel consumption and environmental pollution of ocean-going ships. In order to promote the full usage of ocean wind energy for cargo ships, an innovative type of ship propulsion-assisted wing sail is proposed in this paper. The propulsion efficiency of this new wing sail can be increased by enlarging its area in both the transverse and vertical directions in good weather conditions, and it can be folded up automatically in poor weather conditions, improving the sailing safety of the ship. The sail parameters relating to the gaps and rotation angles between different parts of the wing sail are compared, and the values giving the best aerodynamic performance are identified using CFD simulation technology. The results for the lift and drag coefficients for the new wing sail at different attack angles are also compared with those of traditional aerofoil sails, including an arc-shaped rigid sail and a variable-camber sail proposed in 2015. From the viewpoint of the sailing performance of the vessel, our results demonstrate that this new type of wing sail has good aerodynamic performance and can reduce fuel costs for commercial vessels.

5

Ractive pollutants dispersion modeling in a street canyon

Merah A., Noureddine A.

International Journal of Applied Mechanics and Engineering

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2019

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Vol. 24, no. 1

91--103

EN

Reactive pollutant dispersion in a 3-D urban street canyon is numerically investigated using a computational fluid dynamics (CFD) code (Ansys-CFX), with the k–ε turbulence model and includes transport equations for NO, NO2, and O3 with simple photochemistry. An area emission source of NO and NO2 was considered in the presence of background O3 with an ambient wind perpendicular to the along-canyon direction. The results showed that the magnitude of NOx (NO+NO2) concentrations on the leeward side of the upstream buildings was much larger than the windward side of the downstream building, due to the entrainment and dispersion of traffic emissions by the primary vortex. The reverse is the case for ozone with higher concentrations on the windward side compared to the leeward side. The model has been validated against no-reactive pollutant experimental data of the wind tunnel experiments of Hoydysh and Dabberdt [1].

6

Performance Investigation of a Double Pipe Heat Exchanger under Different Flow Configuration by Using Experimental and Computational Technique

Kannojiya V., Gaur R., Yadav P., Sharma R.

Archive of Mechanical Engineering

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2018

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Vol. LXV, nr 1

27--41

EN

Heat exchangers are widely employed in numerous industrial applications to serve the heat recovery and cooling purpose. This work reports a performance analysis of a tube in tube heat exchanger for different flow configuration under variable operating conditions. The experimental investigation was performed on a U-shaped double pipe heat exchanger set up whereas Commercial Computational Fluid Dynamics code FLUENT along with k-ε turbulence modeling scheme was implemented for the simulation study. The flow solution was achieved by implementing k-ε turbulence modeling scheme and the simulation findings were compared with the experimental results. The experimental findings were in good agreement with the simulation results. The counter-flow configuration was found to be 29.4% more effective than the cocurrent one at low fluid flow rate. Direct relationship between heat transfer rate and flow rate is observed while effectiveness and LMTD showed inverse relationship with it. The significance of inlet temperature of hot and cold stream has been evaluated, they play crucial role in heat exchange process.

7

Parameter identification of ship maneuvering models using recursive least square method based on support vector machines

Zhu M., Hahn A., Wen Y., Bolles A.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2017

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Vol. 11, no. 1

23--29

EN

Determination of ship maneuvering models is a tough task of ship maneuverability prediction. Among several prime approaches of estimating ship maneuvering models, system identification combined with the full-scale or free- running model test is preferred. In this contribution, real-time system identification programs using recursive identification method, such as the recursive least square method (RLS), are exerted for on-line identification of ship maneuvering models. However, this method seriously depends on the objects of study and initial values of identified parameters. To overcome this, an intelligent technology, i.e., support vector machines (SVM), is firstly used to estimate initial values of the identified parameters with finite samples. As real measured motion data of the Mariner class ship always involve noise from sensors and external disturbances, the zigzag simulation test data include a substantial quantity of Gaussian white noise. Wavelet method and empirical mode decomposition (EMD) are used to filter the data corrupted by noise, respectively. The choice of the sample number for SVM to decide initial values of identified parameters is extensively discussed and analyzed. With de-noised motion data as input-output training samples, parameters of ship maneuvering models are estimated using RLS and SVM-RLS, respectively. The comparison between identification results and true values of parameters demonstrates that both the identified ship maneuvering models from RLS and SVM-RLS have reasonable agreements with simulated motions of the ship, and the increment of the sample for SVM positively affects the identification results. Furthermore, SVM-RLS using data de-noised by EMD shows the highest accuracy and best convergence.

8

Reversed Robin Hood syndrome in the light of nonlinear model of cerebral circulation

Piechna A., Cieslicki K.

International Journal of Applied Mechanics and Engineering

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2017

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Vol. 22, no. 2

459--464

EN

The brain is supplied by the internal carotid and vertebro-basilar systems of vessels interconnected by arterial anastomoses and forming at the base of the brain a structure called the Circle of Willis (CoW). An active intrinsic ability of cerebral vascular bed maintains constant Cerebral Blood Flow (CBF) in a certain range of systemic pressure changes. This ability is called autoregulation and together with the redundant structure of the CoW guarantee maintaining CBF even in partial occlusion of supplying arteries. However, there are some situations when the combination of those two mechanisms causes an opposite effect called the Reversed Robin Hood Syndrome (RRHS). In this work we proposed a model of the CoW with autoregulation mechanism and investigated a RRHS which may occur in the case of Internal Carotid Artery (ICA) stenosis combined with hypercapnia. We showed and analyzed the mechanism of stealing the blood by the contralateral side of the brain. Our results were qualitatively compared with the clinical reports available in the literature.

9

Thermal analysis of Double Stator Switched Reluctance Machine (DSSRM) with and without a squirrel cage rotor

Abbasian M., Jalali H.

Archives of Electrical Engineering

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2017

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Vol. 66, nr 1

189--198

EN

Double Stator Switched Reluctance Machine (DSSRM) is a novel switched reluctance machine with limited information about its heat distribution and dissipation. This paper presents a two dimensional (2-D) thermal analysis of Double Stator Switched Reluctance Machine (DSSRM) to observe actual heat distribution in the parts of the machine, using Finite Element Method (FEM). Two topologies for the rotor of DSSRM are considered, Non-Squirrel Cage Double Stator Switched Reluctance Machine (NSCDSSRM) and Squirrel Cage Double Stator Switched Reluctance Machine (SC-DSSRM). The heat distribution of these two topologies is analyzed, using Computational Fluid Dynamics (CFD). Finally the results are presented and compared.

10

The assessment of the calculation method for determining characteristics of one straight ﬁn labyrinth sea

Szymański A., Dykas S., Majkut M., Strozik M.

Transactions of the Institute of Fluid-Flow Machinery

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2016

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nr 134

89--107

EN

The method for the selection of a calculation scheme for the evaluation of the ﬂow behaviour of labyrinth seal with one straight ﬁn, against smooth wall, was presented. Experimental results were obtained from measurement data carried out on the in house, vacuum test section. The advantage of the test rig is a circular shape of the labyrinth specimen, providing similar shape to conﬁguration operated in practise. In computational ﬂuid dynamics study diﬀerent types of mesh resolution were tested, with variable volume discretization in the area of a labyrinth ﬁn tip. Moreover, a wide range of turbulence models basing on k-ε and k-ω, exploiting the (Reynolds Average Navier Stokes) scheme, for the ﬂow pattern evaluation, were examined. All obtained results were compared with literature data, covering research conducted on similar conﬁgurations. The presented study shows challenges as well as the possibilities of calculation simpliﬁcation and compares results obtained by means of simulations and experiment. The proposed method is characterised by excellent agreement of computational results with experiment data.

11

Zastosowanie metody odwrotnej w celu zwiększenia możliwości pomiarowych metody anemometrii obrazowej (PIV)

Stryczniewicz W.

Prace Instytutu Lotnictwa

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2016

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Nr 2 (243)

93--107

PL

W pracy przedstawiono koncepcję zwiększenia możliwości pomiarowych metody anemometrii obrazowej (Particie Image Velocimetry - PIV) poprzez zastosowanie zastosowaniu wyniku symulacji numerycznej w procesie analizy danych pomiarowych. Badania przeprowadzono w celu weryfikacji następującej hipotezy: uzyskanie zgodności wyniku pomiaru metodą PR" oraz wyniku numerycznej symulacji przepływu umożliwi wyznaczenie parametrów przepływu, będących poza zakresem pomiarowym metody PIV'. W ramach pracy przeprowadzono testy numeryczne, w których dokonano estymacji parametrów przepływu wokół profilu NAC A0009. Identyfikacj ipodległa prędkość przepływu strumienia niezaburzonego. W celu sprawdzenia poprawności zaproponowanej procedury estymacji parametrycznej, algorytm przetestowano na symulowanych danych pomiarowych. Wyniki badań testowych dowodzą poprawności opracowanych procedur oraz stanowią przyczynek do rozpoczęcia pracy nad nową metodyką analizy wyników7 pomiarów metodą PIV.

EN

In the presented paper an application of the inverse method for improvement of the measurement capability of the Particle Image Velocimetry method have been discussed. The paper introduces a new approach for PIV data analysis. In a course of the research following thesis has been verified: fitting of the experimental PIV data and a direct numerical problem solution, will lead to determination of flow parameters unobtainable for PIV method. In order to verify the proposed methodology numerical tests has been performed. The parameters of the flow over NACA0009 airfoil has been estimated. The parameter of has been estimated with developed optimization algorithm. The presented results proved the feasibility of proposed methodology and contributes to development of new PIV data post-processing procedure.

12

Simulation of the steady-state behaviour of a new design of a single planar Solid Oxide Fuel Cell

Pianko-Oprych P., Zinko T., Jaworski Z.

Polish Journal of Chemical Technology

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2016

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Vol. 18, nr 1

64--71

EN

The aim of the work was to develop a mathematical model for computing the steady-state voltage – current characteristics of a planar Solid Oxide Fuel Cell and to determine the performance of a new SOFC design. The design involves cross-flow bipolar plates. Each of the bipolar plates has an air channel system on one side and a fuel channel system on the other side. The proposed model was developed using the ANSYS-Fluent commercial Computational Fluid Dynamics (CFD) software supported by additional Fuel Cell module. The results confirm that the model can well simulate the diagonal current path. The effects of temperature and gas flow through the channels and a Membrane Electrode Assembly (MEA) structure were taken into account. It was shown that a significant increase of the MEA temperature at high current density can lead to hot spots formation and hence electrode damage.

13

Three-dimensional modelling of thermal stresses in a planar solid oxide fuel cell of a novel design

Zinko T., Pianko-Oprych P., Jaworski Z.

Informatyka, Automatyka, Pomiary w Gospodarce i Ochronie Środowiska

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2016

|

nr 1

69--72

EN

The presented modelling investigation was carried out to analyze thermal stresses and expansion in an anode supported planar Solid Oxide Fuel Cell (pSOFC). The temperature distribution was based on previously developed thermo-electrochemical model predicting fuel cell operation. The design of a single pSOFC consisted of three ceramic layers of membrane electrode assembly: anode, electrolyte, cathode and two cross-flow bipolar plates with 26 ribs. The gases flowed diagonally from one cell corner to the opposite one. The fuel and air flows were cross-wise opposed on each bipolar plate side. The study allowed to indicate the most vulnerable to thermal damage area of the fuel cell in the operating conditions. The results will be useful in further design modification and performance optimization of the SOFC.

PL

Przeprowadzone symulacje numeryczne miały na celu analizę termicznych naprężeń i ocenę stopnia wydłużenia płaskiego stałotlenkowego ogniwa paliwowego typu pSOFC (ang. planar Solid Oxide Fuel Cell). Rozkład temperatury w ogniwie wyznaczono w oparciu o wcześniej opracowany model termiczno-elektrochemiczny [11]. Nowatorskie rozwiązanie ogniwa typu pSOFC objęło ceramiczną konstrukcję, w skład której weszły porowate elektrody – anoda i katoda, elektrolit oraz dwie płytki bipolarne z 26-cioma żebrami. Przepływ paliwa i powietrza odbywał się krzyżowo i przeciwprądowo, po przekątnej ogniwa. Wyniki symulacji pozwoliły na określenie obszarów ogniwa narażonych na uszkodzenie w wyniku wysokich wartości naprężeń termicznych. Uzyskane rezultaty FEM umożliwią dalszą modyfikację konstrukcji płaskiego ogniwa w celu optymalizacji wydajności pSOFC.

14

Aerodynamika autobusu miejskiego w ujęciu CFD

Paszko M.

Autobusy : technika, eksploatacja, systemy transportowe

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2016

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R. 17, nr 6

1071--1073

PL

W niniejszym artykule przedstawiono możliwości wykorzystania metod CFD (Computational Fluid Dynamics) w procesie badania aerodynamiki nadwozia typowego, współczesnego autobusu miejskiego. Przedstawiono również proces budowy przestrzennego, numerycznego modelu procesów aerodynamicznych przebiegających w trakcie opływu nadwodzia autobusu miejskiego na przykładzie pakietu Ansys Workbench.

EN

Paper discussed the general usability of the Computional Fluid Dynamics (CFD) in process of studying aerodynamics of the commercial busses.

15

Modelowanie ustalonych procesów przepływowo-cieplnych w kotle fluidalnym

Taler D., Madejski P., Taler J.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

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2015

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z. 87 [291], nr 2

169--178

PL

W pracy zostały przedstawione wyniki komputerowej symulacji pracy przegrzewacza pary w stanach ustalonych. Analizowany przegrzewacz charakteryzuje się złożonym kształtem przekroju poprzecznego rur i jest stosowany w kotłach z cyrkulującą warstwą fluidalną. W trakcie obliczeń cieplno-przepływowych niezbędne jest wyznaczanie rozkładu temperatury materiału na całej długości przegrzewacza. Do przeprowadzenia obliczeń pracy przegrzewacza w stanach ustalonych stworzono własny model matematyczny, napisany w języku Fortran, którego wyniki zostały porównane z wynikami otrzymanymi w programie Star-CCM+. W modelu własnym zastosowano bilansową metodę elementów skończonych, która pozwala na dokładne odwzorowanie rozkładu temperatury przy niewielkiej liczbie komórek siatki. Do wyznaczenia właściwości przepływającej pary została zastosowana jawna metoda różnic skończonych. Wyniki uzyskane z zastosowaniem opracowanego własnego modelu wykazały się bardzo dobrą zgodnością z wynikami uzyskanymi dzięki modelowaniu CFD.

EN

The paper presents the results of computational steady-state simulations of the superheater. Analyzed superheater is characterized by complex shape of cross-section of tubes and is used in boilers with circulating fluidized (CFD). During the thermal and flow calculations of the superheater with a complex cross-section shape, the temperature distribution of the material need to be determined over the entire length of the superheater. To perform the calculations of superheater operation in the steady state was created its own mathematical model, prepared in Fortran language, which the results were compared with the results obtained in the Star-CCM + software. In this model, to solve the equation of heat conduction was applied the balance finite element method, which allows for the accurate determination of the temperature distribution using a small number of grid cells. To determine the properties of flowing steam the explicit finite difference method was applied. The results obtained by the own model compared with the results obtained by CFD modeling show very good agreement.

16

Numerical Simulations and Experimental Study on Reduction of Wind Tunnel Turbulence Intensity

Kulak M., Karczewski M., Olasek K., Jankowski K.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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2015

|

nr 147

25--38

EN

Having an upgraded wind tunnel in the Institute of Turbomachinery (IMP) at the Lodz University of Technology, a series of CFD simulations has been performed in order to indicate the areas of possible flow quality improvement. It was decided to introduce the honeycomb section in order to diminish the lateral turbulence. Additionally, CFD simulations were performed in order to gain information about the level of turbulence reduction and the associated pressure loss. The paper presents results from both: the measurements of turbulence intensity before and after the installation of the honeycomb in the IMP wind tunnel, as well as the associated simulation results conducted for a WT model (virtual WT) in ANSYS CFX 13.0/14.0. Results of above research were presented on XX Fluid Mechanics Conference KKMP2012.

PL

W ramach rewitalizacji tunelu aerodynamicznego w Instytucie Maszyn Przepływowych (IMP) Politechniki Łódzkiej, przeprowadzono serię symulacji numerycznych mających na celu wyznaczenie obszarów pozwalających na potencjalną poprawę jakości przepływu. Podjęto decyzję o montażu prostownicy ulowej celem zmniejszenia intensywności turbulencji. Dodatkowo, przeprowadzono symulacje numeryczne określające osiągalny poziom redukcji turbulencji oraz strat ciśnienia. Artykuł zawiera wyniki pomiarów doświadczalnych intensywności turbulencji w kanale, przed i po montażu prostownicy ulowej w tunelu aerodynamicznym IMP oraz odpowiadające im rezultaty symulacji numerycznych wirtualnego modelu tunelu (przeprowadzone z użyciem ANSYS CFX 13.0/14.0). Powyższe wyniki zostały zaprezento-wane na konferencji KKMP2012.

17

Numerical simulations of gap flow above rotating disk

Wasilczuk F., Flaszyński P., Doerffer P.

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

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2015

|

Vol. 19, No 2

89--100

EN

A rotating disk can be considered a basic configuration for the investigations of the impact of various conditions on the flow through the clearance between the shrouded turbine blade and the casing. Numerical calculations using Fine/Turbo Numeca were conducted to examine the influence of the rotational velocity and the pressure difference across the disk on the flow conditions, especially the mass flow through the clearance. The results were validated using the experimental data. Moreover, the flow field was investigated to reveal the vortices induced in the flow. The calculations showed a significant drop of the mass flow with a rise of the rotation velocity. Additionally, the vortex created upstream of the disk at higher rotation velocities was observed. The phenomenon of separation at the edge of the disk was investigated.

18

Implementation of an Eulerian method of determination of surface water collection efficiency for atmospheric icing problems

Sznajder J.

Prace Instytutu Lotnictwa

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2015

|

Nr 1 (238)

91--105

EN

In the presented article numerical implementation of a method of determination of water collection efficiency of a surface in two-phase flow of air and dispersed water droplets of concentration typical for icing problems is presented. An assumption of one-directional coupling between phases, frequently used for similar problems was adopted. In this approach the airflow influences the water droplet phase flow, and itself is not influenced by the droplet flow. Two-dimensional flow model was adopted in Eulerian approach, solving the droplet phase equations of motion in the whole computational domain. The water droplet phase flow was modeled using three variables representing droplet concentration and two components of velocity and three equations: the droplet continuity equation and two equations for the conservation of momentum in two perpendicular directions. The variables and equations describing the motion of the water droplet phase were introduced as User-Defined Scalars and User-Defined Equations to the commercial Fluent solver. It was assumed, that the droplet motion is the result of drag, gravity and buoyancy forces. The test computations were performed for the NACA 23012 airfoil, for two cases of droplet diameter and droplet phase concentration. The computation results were compared with experimental results. The comparisons demonstrate close agreement of the computed results (mass of captured water in unit time, surface distribution and local maximum value) for low values of Liquid Water Content, defined in FAR25 airworthiness regulations. For higher values of Liquid Water Content, typical for the phenomenon of “Supercooled Large Droplets” the present method overestimates the value of captured water per time, but the maximum value of the collection efficiency and the extent of the surface capturing water is predicted correctly. Also investigations of the effects selected aerodynamic and flow parameters on the mass of collected water were conducted.

PL

W pracy przedstawiono implementację numeryczną metody wyznaczania współczynnika masy wody uderzającej w powierzchnię w dwufazowym opływie powietrza i rozproszonych kropel wody o koncentracji typowej dla sytuacji spotykanych w problemach związanych z oblodzeniem atmosferycznym. Przyjęto często stosowane założenie o jednokierunkowym sprzężeniu przepływów, tzn. że przepływ powietrza oddziałuje na przepływ fazy wodnej natomiast przepływ fazy wodnej nie ma wpływu na przepływ powietrza. Przyjęto dwuwymiarowy model zjawiska w ujęciu Eulerowskim, rozwiązując równania przepływu fazy wodnej w całym obszarze obliczeniowym. Przepływ fazy wodnej zamodelowano przez wprowadzenie trzech zmiennych reprezentujących koncentrację fazy i dwie składowe prędkości przepływu oraz trzech równań: równania ciągłości fazy wodnej i dwóch równań zachowania składowych pędu w kierunku dwóch osi układu współrzędnych. Zmienne i równania opisujące ruch fazy wodnej wprowadzono jako Skalary Definiowane Przez Użytkownika i Funkcje Definiowane Przez Użytkownika w komercyjnym programie obliczeniowym Fluent. Założono, że ruch fazy wodnej jest wynikiem działania sił: oporu, ciężkości i wyporu na krople wody. Przeprowadzono obliczenia testowe dla opływu profilu NACA 23012 i dwóch przypadków wartości średnicy kropel i koncentracji fazy wodnej. Uzyskane wyniki porównano z wynikami eksperymentu. Wyniki porównań wykazują dobrą zgodność uzyskanych wyników (masy osiadającej wody na jednostkę czasu, rozkładu powierzchniowego i maksymalnej wartości) dla umiarkowanych wartości zawartości rozproszonej wody w powietrzu, opisanych przez regulacje FAR 25. Dla zawartości wody znacznie przekraczającej te wartości, typowych dla zjawiska „Supercooled Large Droplets” prezentowana metoda przeszacowuje wartość przechwytywanej wody, ale prawidłowo wyznacza maksymalną wartość współczynnika przechwytywania wody i obszar przechwytujący krople. Przeprowadzono również obliczenia wpływu wybranych parametrów aerodynamicznych na ilość przechwytywanej wody przez profil.

19

Modelowanie kawitacji przy opływie profilu z zastosowaniem zmiennej liczby kawitacji

Homa D., Wróblewski W.

Modelowanie Inżynierskie

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2015

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T. 24, nr 55

42--49

PL

W artykule przedstawiono modelowanie przepływu z kawitacją w przypadku opływu wokół profilu hydraulicznego. Liczba kawitacja została dobrana w taki sposób, by zaobserwować różne typy struktur kawitacyjnych. Użyto modelu wielofazowego typu one–fluid oraz założono izotermiczność przepływu. Do zamodelowania powstawania fazy gazowej użyto modelu Schnerr & Sauer. Ze względu na niestacjonarność zjawiska zastosowano symulacje typu transient. Porównano wyniki symulacji z danymi eksperymentalnymi dla różnych typów kawitacji. Przeanalizowano rozkłady udziału objętościowego pary w punktach monitorujących wzdłuż profilu oraz okresy zmian struktur kawitacyjnych. Do symulacji użyto profilu ClarkY. Obliczenia przeprowadzono z użyciem kodu OpenFoam z wykorzystaniem solvera interPhaseChangeFoam.

EN

The paper concerns cavitation modelling in case of flow over a hydrofoil. Cavitation number was set to the values that enable to observe different types of cavitation. Multiphase model of one-fluid type was used and isothermal flow was assumed. To simulate vapor volume transport the Schnerr & Sauer model was used. As the investigated phenomenon is unsteady transient type of calculation was used. The calculation results for different cavitation types were compared with the available experimental data. The distribution of vapor volume fraction in monitor points over the foil as well as changes in the frequency of cavitation structures were analysed. The simulation was run on ClarkY foil. The calculations were performed using OpenFoam open source code with interPhaseChangeFoam solver.

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CFD computation of the savonius rotor

Rogowski K., Maroński R.

Journal of Theoretical and Applied Mechanics

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2015

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Vol. 53 nr 1

37--45

EN

In this paper, Computational Fluid Dynamics (CFD) analysis of a two-dimensional two- -bucket Savonius rotor, using ANSYS Fluent solver, is presented. Computational methods of fluid dynamics are used to estimate the aerodynamic forces acting on the rotor, the torque and the power extracted by the Savonius rotor. In addition, an analysis of the results for different turbulence models is performed. Numerical investigations are compared with the experiment of the Sandia National Laboratories.