Wyniki wyszukiwania - Biblioteka Nauki

1

On the peristaltic transport of a micropolar fluid

100%

Dey K. N. , Poria S. , Mazumdar H. P.

Engineering Transactions

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2005

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tom Vol. 53, iss. 1

3-14

EN

In this paper, we study some characteristics of the peristaltic motion of an incompressible micropolar fluid through a circular cylindrical tube. Many authors have investigated the peristaltic motion of non-Newtonian or viscoelastic fluid through a channel or tube due to the relevance of peristaltic action in both mechanical and physiological situations. For example, peristaltic mechanism may be involved in vasomotion of small blood vessels. Here the microstructural effects on the pressure rise, average flow and friction force are investigated.

2

Inertia effect in a flow of a generalized second grade fluid of a power-law type between two fixed surfaces of revolution

86%

Walicka A. , Walicki E.

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2003

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tom Vol. 8, no spec.

187-194

EN

The steady laminar flow of a generalized second grade fluid of a power-law type through a narrow space between two fixed surfaces of revolution, having a common axis of symmetry, is considered. To solve this problem the boundary layer equations are used and expressed for axially symmetric case in a curvilinear orthogonal coordinate system connected with one of the surfaces. The method of averaging inertia and viscoelastic terms is used to solve the formula expressing the pressure distribution in a gap between fixed surfaces of revolution.

3

Flow of a second order/grade fluid due to non-coaxial rotation of a porous disc and the fluid at infinity

86%

Ersoy H. V. , Baris S.

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tom Vol. 7, no 4

1189-1198

EN

The flow of an incompressible second order/grade fluid due to non-coaxial rotation of a porous disk and the fluid at infinity with the common angular velocity is studied. It is shown that there are physically acceptable solutions for both suction and blowing cases, depending on the sign of the material modulus 'alpha'1 . It is observed that the elasticity of the fluid causes the boundary layer thickness to increase in the case of suction, whereas it causes the boundary layer thickness to decrease in the case of blowing.

4

Analiza teoretyczno-doświadczalna pomiaru strumienia objętości płynu za pomocą przepływomierza kolanowego

86%

Malinowski Ł. , Rup K.

Inżynieria Chemiczna i Procesowa

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2006

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tom T. 27, z. 3/1

803-816

PL

Zaproponowano metodę pośredniego pomiaru strumienia przepływu płynu w zastosowaniu do przepływomierzy kolanowych. W celu praktycznej realizacji zaproponowanej metody zbudowano stanowisko doświadczalne. Obliczenia numeryczne wykonano za pomocą pakietu FLUENT 6.1.

EN

An indirect measurement method of volume flow rate in application to elbow meters is proposed. With the aim of practical realisation of the method, experimental set-up was built. Numerical calculations were performed with application of FLUENT CFD software. The results were compared with those obtained experimentally with use of orifice meter.

5

Computational challenges in MEMS

72%

Furuberg L.

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tom Vol. 7, no 1

173-185

EN

Small sensors and actuators made from materials like silicon, quartz or plastic are already parts of our everyday life. In cars there are often silicon sensors measuring acceleration, tyre pressure and car roll-over. There may be microfabricated mechanical components inside your light projector or in your ink-jet printer. In the future, microsystems are believed to be widespread, being used for environment monitoring, safety systems, medical care and biochemical analyses. The small mechanical elements are easily integrated in electrical circuits that control their behaviour, process their output signals or interconnect several active and passive elements in a control system. Behaviour of the mechanical elements is often governed by interacting elastic forces, electromagnetic forces and forces due to surrounding fluids. Computation of the behaviour is therefore complicated. Engineers working with macroscopic constructions like oil-platforms, where mechanical and fluid forces interact, face similar challenges. Experiences and research results from the macroscopic world are therefore of great importance for the design of microsystems. Microsystem elements usually involve micrometer sized features. The small scale introduces effects that are negligible on larger scales, such as strong surface forces. In addition, the continuum hypothesis may break down in some problems, excluding the use of partial differential equations describing the behaviour. There are also fundamental physical effects occurring on small scales that are not yet understood. An important task in microsystems design is to develop reduced-order macromodels that capture the essential behaviour of a mechanical microelement. The complicated electrical circuits controlling the mechanical elements need to be optimised, and this will be too time-consuming without simplified descriptions. We present examples of microsystems, outline current computational technology and some remaining challenges in these fields.

6

Wrażliwość elementów płynowych i elastomerowych na zmiany temperatury

72%

Amborski J. , Osiński J. , Zbrowski A.

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2005

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tom nr 4

89--99

PL

W pracy przedstawiono porównanie wrażliwości na zmiany temperatury tłumików płynowych i z elementem elastomerowym. Wskazano na przyczyny znacznej wrażliwości elementów płynowych wynikający z dużych zmian właściwości cieczy, w szczególności lepkości w funkcji temperatury. Jako rozwiązanie alternatywne rozważono tłumik z elementem elastomerowym o znacznie mniejszej zależności od zmian temperatury. Opracowano również metodę wyznaczania właściwości mechanicznych materiałów elastomerowych, z zastosowaniem opisu wg modelu Mooney'a-Rivlina i prawa Hooke'a.

EN

The paper presents a comparison of temperature sensitivity of hydraulic and elastomer vibration dampers. The sources of great temperatures sensitivity of hydraulic elements are identified as hydraulic fluids properties, especially viscosity as function of temperature. It has been stated that damping force decrease non-linearly with temperature rising. The changes are bigger in lower temperature range (under 0°C) and smaller in higher temperature range (above 40°C) . As an alternative design was proposed an elastomer damper with much smaller temperature sensitivity. There has been also elaborated method of determining the mechanical characteristics of elastomer materials which uses Mooney - Rivlin model and a Hooke law. The tests was conducted in Landing Gear Department of Warsaw Institute of Aviation. The results gave the possibility of definition of two work phases conditions. The first phase is the elastic work, the second one is the friction work. It has been stated that graphite powder improves the work of damper in the friction work range.

7

Topology optimization - broadening the areas of application

72%

Bendsoe M. P. , Lund E. , Olhoff N. , Sigmund O.

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tom Vol. 34, no 1

7-35

EN

This paper deals with recent, developments of topology optimization techniques for application in some new types of design problems. The emphasis is on recent work of the Danish research groups at Aalborg University and at the Technical University of Denmark and focus is on the central role that the choice of objective functions and design parameterization plays for a successful extension of the material distribution approach to new design settings and to new types of physics models. The applications that will be outlined encompass design of laminated composite structures, design for pressure loads, design in fluids, design in acoustics, and design in photonics. A short outline of other design optimization activities is also given.

8

The aircraft piston engine conjugate heat transfer model

58%

Tulwin T.

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2017

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tom Vol. 24, No. 1

349--355

EN

Maintaining high aircraft’s propulsion system reliability requires a good knowledge of engine’s heat transfer conditions at each engine running time. Even though the flow around the cylinder may be steady, the heat flux from the engine is not evenly distributed. This is caused by varied engine head and fins geometry and uneven heat transfer coefficient distribution. The lack of knowledge of the local heat transfer coefficient values and time coefficients for the transient heat transfer make it unfeasible to make an analytical model for a given geometry. One transient Computational Fluid Dynamics simulation does not solve the heat transfer fully. Only a conjugate simulation allows an in-depth analysis of a transient heat transfer. The Combustion and species transport fluid simulation is coupled to the temperature field solid simulation. This work presents the methods and results of such conjugate heat transfer simulation. The change of heat flux parameters in respect to time is shown. The results are verified by the real engine measurements.