Wyniki wyszukiwania - BazTech

1

Analiza rozkładu pola przepływowego w cienkiej warstwie przewodzącej z defektem eliptycznym

Pawłowski Stanisław, Plewako Jolanta, Korzeniewska Ewa

Przegląd Elektrotechniczny

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2020

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R. 96, nr 1

234--237

PL

W artykule zaprezentowano analityczne rozwiązanie zagadnienia obliczania rozkładu pola przepływowego w cienkiej warstwie przewodzącej z defektem (pęknięciem) o kształcie elipsy. Wyprowadzono wzory na funkcje potencjału i składowych pola elektrycznego oraz przybliżony wzór pozwalający oszacować wpływ defektu na natężenie prądu w ścieżce przewodzącej. Ponadto podano wzory dla pęknięcia nieskończenie cienkiego oraz dokonano oceny wpływu tej idealizacji na oszacowanie natężenia prądu w ścieżce.

EN

The article presents an analytical solution of the problem of calculating the flow field distribution in a thin electroconductive layer defected with the cracks in the shape of an ellipse. The formulas for the functions of the potential and the electric field components as well the approximate formula allowing to estimate the impact of the defect on the current in the electroconductive layer were derived. In addition, formulas for infinitely thin cracks were given and the impact of this idealization on the estimation of current in the electric path was assessed.

2

Numerical Simulation of the Condensing Effect of Different Suction Slots on Fiber Strands in a Compact Siro Spinning Machine with Lattice Apron

Han Chenchen, Gao Weidong, Chen Lifen

Autex Research Journal

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2020

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Vol. 20, no. 1

1--10

EN

Compact-siro spun with lattice apron combines compact spinning and siro spinning, and is widely put into practice. In this paper, compact-siro spun models with the parallel shaped slots, oblique parallel shaped slots and V-shaped slots were simulated. Based on the airflow data in the condensing zone, the geometrical model of single fiber is built, and then the trajectory of single fiber can be got. The morphological changes and movement process of fiber strands in the flow field of condensing zone were verified by the comparison experiments of yarn morphology, hairiness, tensile and evenness properties. The results showed that the V-shaped slot achieved the optimal agglomeration effect and yarn performance. The theory analysis gives foundation and explanation for the experiment, and also provides a theoretical basis for optimizing the properties of compact-siro yarn in production practice.

3

Parametric study on the flow field generated by river barge bow steering systems

Abramowicz-Gerigk Teresa, Burciu Zbigniew, Jachowski Jacek

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2019

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nr 60 (132)

9--17

EN

Low controllability under strong winds presents a problem for the operation of inland vessels, which can be improved using passive bow rudders and transverse thrusters. Bow thrusters can sufficiently improve the manoeuvrability at low speeds, but an unsolved problem is course maintaining and yaw checking of a vessel at medium and high speeds. This paper proposes the use of a bow steering system in which the bow rotors generate a Magnus force. The first physical test model of the system showed promising results and that much more research must be performed before this system can be used in industrial applications. The paper presents the results of a numerical study on the flow field generated by bow rotors. The first stage of a ship’s turn using the bow rotors was used to determine the dependence of the expected steering force on the inflow velocity and rotational speed of the rotors. The influence of the flow generated by the bow steering system on river banks and quay walls during manoeuvres was also discussed.

4

The prediction of hull gesture and flow around ship based on Taylor expansion boundary element method

Gong Jiaye, Li Yunbo

Polish Maritime Research

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2019

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nr 2

198--211

EN

Based on the potential flow theory and traditional boundary element method (BEM), Taylor expansion boundary element method (TEBEM) is introduced in this paper for the prediction of the flow field around ship, as a result, hull gesture and pressure distribution on hull surface are obtained. By this method, dipole strength of every field point is expanded in Taylor expansion, so that approximately continuous hull and free surface boundary condition could be achieved. To close the new equation system, the boundary condition of tangent velocity in every control point is introduced. With the simultaneous solving of hull boundary condition and free surface condition, the disturbance velocity potential could be obtained. The present method is used to predict the flow field and hull gesture of Wigley parabolic hull, Series 60 and KVLCC2 models. To validate the numerical model for full form ship, the wave profile, the computed hull gesture and hull surface pressure of KVLCC2 model are compared with experimental results.

5

Chemically reacting ionized radiative fluid flow through an impulsively started vertical plate with induced magnetic field

Ahmed T., Alam M. M., Ferdows M., Tzirtzilakis E. E.

International Journal of Applied Mechanics and Engineering

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2019

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Vol. 24, no. 1

5--36

EN

Numerical studies have been performed to examine the chemically reacting ionized fluid flow through a vertical plate with induced magnetic field. This study is performed for the cooling problem. To obtain the nondimensional non-similar momentum, the induced magnetic field, energy and concentration equations, usual nondimensional variables have been used. The numerical solutions for the velocity fields, induced magnetic fields, temperature distribution as well as concentration distribution are obtained for associated parameters using the explicit finite difference method. The local and average shear stresses, current densities, Nusselt number as well as the Sherwood number are also investigated. The obtained results are discussed with the help of graphs to observe effects of various parameters entering into the problem. Also the stability conditions of the explicit finite difference method are analyzed. Finally, a qualitative comparison of the present results with previously published results has been made.

6

Effect of two distinct patches of Myriophyllum species on downstream turbulence in a natural river

Przyborowski Łukasz, Łoboda Anna Maria, Bialik Robert Józef

Acta Geophysica

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2019

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Vol. 67, no. 3

987--997

EN

Velocity profiles upstream and downstream of two aquatic plant species that are similar in morphology but differ in patch structures were measured in a natural river. Turbulence statistics were analyzed after thorough data filtering. In the wake of the M. alterniflorum, which was a slender, 0.3 m wide and 1.2 m long patch of aspect ratio 1:4, there were distinctive peaks in both, turbulence intensity and turbulent kinetic energy, which indicated increased lateral mixing. In contrast to the M. alterniflorum, turbulence statistics in the wake of the M. spicatum, which was the larger, 2 m wide and 2.4 m long patch of aspect ratio 1:1.5, indicated increased lateral shear of a greater magnitude. The turbulent kinetic energy was diminished in the closest layer to the bed downstream the both plants, although, in the case of M. alterniflorum, the observed values were similar to those upstream. The occurrence of the mixing layer below the height of M. spicatum was visible in the power spectral density plot. In both cases, ejections in the wake diminished in favor of other coherent structures. The shape and configuration of a patch are decisive factors governing the occurrence of flow instabilities downstream of the patch.

7

Simulation and experimental study of SCR injection system

Du J., Zhang Y., Cai Y.

Polish Maritime Research

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2018

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S 2

49--55

EN

According to actual engineering test, we design a linear controlled spray ammonia grille, and apply it to the SCR injection system of ship tail gas treatment. In this paper, the geometric model of ammonia injection grid was built in the flue of diesel engine, and the effects of spray atomization, ammonia uniformity and urea droplet distribution on spray atomization were simulated. Then the test bench was set up to observe the injection status of the ammonia injection grille. The NOx content of the outlet was measured by the original data of the flue gas, and the experimental data were processed. We calculate the denitrification rate by taking the average value to verify the correctness of the spray ammonia grid scheme.

8

Investigation of edge fairing shaping effects on aerodynamic response of long-span bridge deck by unsteady RANS

Haque M. N., Katsuchi H., Yamada H., Nishio M.

Archives of Civil and Mechanical Engineering

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2016

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Vol. 16, no. 4

888--900

EN

Triangular edge fairings are widely used and attached to the edges of rectangular box girder bridge decks to improve their aerodynamic responses. Bridge deck with edge fairing should be shaped efficiently to obtain optimum aerodynamic responses. In this paper, the shaping effect of a triangular edge fairing on aerodynamic behaviour of a bridge deck is presented. A wide range of top and bottom plate slopes is utilized to change the shape of the fairing. The unsteady RANS simulation with the k–ω-SST turbulence model is used to simulate the flow. The flow is discretized by the finite volume method with second-order accuracy in space and time. The mean and rms values of the force coefficients are evaluated and the after-body velocity fluctuations are plotted. The aerodynamic responses are tried to explain by means of pressure and velocity distributions around the bridge deck. A relative comparison of the aerodynamic responses of perforated and solid handrails is also presented. It is found that a lower aerodynamic response can be obtained by properly shaping the triangular edge fairing.

9

Numeryczne modelowanie dwuwymiarowego pola przepływu na obszarach zalewowych

Siuta T.

Czasopismo Techniczne. Środowisko

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2011

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R. 108, z. 2-Ś

219-225

PL

W artykule przedstawiono i poddano analizie przykładowe wyniki symulacji numerycznej dwuwymiarowego pola ustalonego przepływu na terenach zalewowych podgórskiej rzeki Raby tuż poniżej zbiornika retencyjnego w Dobczycach. Obliczenia mają charakter poglądowy i mają na celu przedstawienie tych wyników z rozwiązania dwuwymiarowego, których nie można otrzymać za pomocą konwencjonalnych modeli jednowymiarowych, powszechnie stosowanych przy wyznaczaniu stref zalewu. Wyniki obliczeń wykorzystano do wyznaczania potencjalnych stref zalewu, będącego skutkiem przerwania lub przelania się wody przez koronę wału.

EN

In the paper the results of numerical simulation of steady 2D flow field at floodplains of Raba river just downstream of Dobczyce reservoir were presented. The purpose of this calculation is presentation of qualitative hydraulics effects which are unattainable by conventional 1D models widely applied in the field of floodplains determination. This hydraulics effects concern the potential flow due to levee breach or levee overtopping mainly.

10

Characteristics of the flow field in the combustion chamber of the internal combustion test engine

Tutak W., Jamrozik A.

Chemical and Process Engineering

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2011

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Vol. 32, nr 3

203-214

EN

Results of a research study into the velocity field in combustion chamber of internal combustion engine are presented in the paper. Measurements of fresh charge flow velocity in the cylinder axis and near the cylinder squeezing surface were performed. The hot-wire anemometer was used. The measurement results were used for analysis of turbulence field in the examined combustion chamber. It turned out that in the axis of cylinder the maximum of velocity occurs 30 deg before TDC and achieves 6 m/s. In the studied combustion chamber, the maximum value of turbulence intensity was close to 0.2 and it was achieved 35 deg BTDC. Additionally, the maximal velocity dispersion in the following cycles of the researched engine was at the level of 2 m/s, which is 35% of the maximum value of flow velocity. At a point located near the squeezing surface of the piston, a similar level of turbulence, but a the smaller value of the average velocity was achieved. The turbulence field turned out to be inhomogeneous in the combustion chamber.

11

Modelowanie numeryczne pola przepływu wokół budynków

Folusiak M.

Prace Instytutu Lotnictwa

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2008

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Nr 3-4 (194-195)

171-175

PL

W artykule przedstawiono wyniki dwu- i trójwymiarowych symulacji numerycznych opływu budynków wykonanvch z wykorzystaniem pakietu obliczeniowego ANSYS Fluent. Rozpatrzono cztery przypadki obliczeniowe budynków o różnej szerokości.

EN

In this paprer, results of two- and three-dimensional numerical investigations on the flow field near buildings, which were performed using ANSYS Fluent, are presented. For numerical cases of buildings of different width were investigated.

12

Interpretacja wyników pomiaru prędkości przepływu ładunku w komorze spalania tłokowego silnika spalinowego

Tutak W.

Pomiary Automatyka Kontrola

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2008

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R. 54, nr 2

67-70

PL

W opracowaniu przedstawiono interpretację wyników pomiaru prędkości przepływu ładunku w komorze spalania tłokowego silnika spalinowego. Analizie poddano wpływ metody opracowania wyników pomiaru prędkości przepływu na uzyskane wyniki parametrów opisu pola prędkości w komorze spalania silnika tłokowego.

EN

The paper presents measurement results of flow field of fresh charge in the combustion chamber of the internal combustion engine. Possibilities of interpretation results of flow velocity measurement in combustion chamber of internal combustion engine are presented in the paper. The data handling method of flow velocity measurement result influence on obtained turbulence field in combustion chamber parameters are analyzed. The results of research show that non-repeatability of flow velocity in the combustion chamber have influence on description of turbulence parameters.

13

Investigation of wet steam flow in LP steam turbine using a novel integrated probe: experimental results

Wang L., Cai X., Ouyang X.

Archives of Thermodynamics

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2002

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Vol. 23, no 4

49-57

EN

In low-pressure (LP) steam turbine, the wetness fraction of steam causes dangerous erosion of turbine blades and decrease of turbine efficiency. In the study of wet steam flow, wetness, droplet size and velocity are of the main concern. These parameters are closely correlated to the vapour phase of the flow field and have to be measured simultaneously. Following this line, a novel integrated probe system has been successfully developed, based on light scattering technique, correlation theory and common methods for flow field measurement. By using this system, experiment has been performed in a 200 MW and a 350 MW condensing steam turbine. Part of the results are presented and some newly detected phenomena are put forward and discussed.

14

Deviation and profile losses in a turbine cascade at off-design incidences

Willinger R., Haselbacher H.

Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka

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1999

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nr 115

431--443

EN

This paper presents details of an investigation of the two-dimensional flow field in a linear turbine cascade at off-design incidences. The cascade geometry corresponds to the tip section of a moving blade row of a gas turbine of recent design. Six different inlet flow angles, ranging from high positive incidence to high negative incidence, have been investigated experimentally. A three hole pressure probe was traversed immediately downstream of the trailing edge plane. Further work concerned the computation of the cascade flow field with a finite-element based Navier-Stokes solver. The k/ɛ-model was used to account for the turbulent behavior of the flow. The measurement and computational results are compared with an established profile incidence loss correlation.

15

Tarcie, strefa martwa, strefa plastyczna w matematycznym modelowaniu procesu wyciskania.

Śliwa R. E., Miszuris W.

Rudy i Metale Nieżelazne

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1999

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R. 44, nr 11

575-580

PL

Przedstawiono klasyczny problem osiowosymetrycznego wyciskania monomateriału w aspekcie udoskonalenia modelu matematycznego pod kątem uwzględnienia teoretycznego opisu zachowania się pola płynięcia w otoczeniu granicy maksymalnych ścinających naprężeń. Zaproponowano kinematycznie dopuszczalne pole płynięcia zastosowane w Metodzie Górnej Oceny do obliczenia granicy powstającej strefy martwej. Pokazano, że zaproponowany model prowadzi do najlepszego oszacowania siły wyciskania w porównaniu z wszystkimi radialnymi, kinematycznie dopuszczalnymi polami płynięcia (które nie uwzględniają osobliwego zachowania się prędkości odkształceń). W analizie zawarto wpływ tarcia na granicy metal-narzędzie. Przedstawiono również problem związany z określeniem kąta pomiędzy styczną do granicy strefy plastycznej a osią symetrii matrycy (wskaźnik kształtu strefy plastycznej) oraz określono jego wpływ na obliczaną wartość siły wyciskania.

EN

In the paper classic problem of axisymmetrical extrusion through a conical die is investigated. New results concerning behaviour of the plastic flow field in the neighbourhood of the maximal shear stress surface are introduced to improve description of the dead zone formation. As a result, a modified mathematical model of the process is presented. Basing on in the problem of the dead zone shape determination is investigated by using the Upper Bound Method. It is shown that the proposed model leads to the better evaluation of the extrusion pressure in comparison with other radial kinematicaly admissible velocity fields (without taking into account singular behaviour of the strain rate). Through investigations the phenomenon of friction along the boundary tool-metal has been taken into consideration. The another problem presented in the paper is investigation of the assumptions concerning determination of the angle between the tangent to a plastic zone boundary and the symmetry axis (indicator of shape of plastic zone) with respect to the value of extrusion pressure.