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1
Content available Review of numerical models of cavitating flows with the use of the homogeneous approach
Niedźwiedzka A., Schnerr G. H., Sobieski W.
Archives of Thermodynamics
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2016
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Vol. 37, no. 2
71--88
EN
The focus of research works on cavitation has changed since the 1960s; the behaviour of a single bubble is no more the area of interest for most scientists. Its place was taken by the cavitating flow considered as a whole. Many numerical models of cavitating flows came into being within the space of the last fifty years. They can be divided into two groups: multifluid and homogeneous (i.e., single-fluid) models. The group of homogenous models contains two subgroups: models based on transport equation and pressure based models. Several works tried to order particular approaches and presented short reviews of selected studies. However, these classifications are too rough to be treated as sufficiently accurate. The aim of this paper is to present the development paths of numerical investigations of cavitating flows with the use of homogeneous approach in order of publication year and with relatively detailed description. Each of the presented model is accompanied by examples of the application area. This review focuses not only on the list of the most significant existing models to predict sheet and cloud cavitation, but also on presenting their advantages and disadvantages. Moreover, it shows the reasons which inspired present authors to look for new ways of more accurate numerical predictions and dimensions of cavitation. The article includes also the division of source terms of presented models based on the transport equation with the use of standardized symbols.
2
Content available Unsteady convection flow of a magnetomicropolar fluid past a vertical porous plate
Jain N. C., Gupta P., Sharma B.
International Journal of Applied Mechanics and Engineering
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2013
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Vol. 18, no. 1
43--53
EN
The paper deals with an unsteady two dimensional laminar slip flow of a viscous incompressible magnetomicropolar fluid past a semi infinite porous plate embedded in a porous medium. The flow is under the influence of a transverse magnetic field and heat source/sink. The free stream velocity follows an exponentially increasing or decreasing small perturbation law. The porous surface absorbs the fluid with time varying suction velocity. Expressions are obtained for velocity and temperature fields, mean angular velocity, skin friction and the Nusselt number.
3
Content available remote Hadamard incomplete sensitivity and shape optimization
Mohammadi B.
Control and Cybernetics
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2010
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Vol. 39, no 3
615-626
EN
The paper discusses incomplete sensitivity evaluations for shape optimization problems. It also shows how reduced order models can be introduced to extend the validity domain of the approach.
4
Content available remote Unsteady free convection flow along a vertical cone in a stable thermally stratified medium
Bapuji P., Ekambavanan K., Pop I.
International Journal of Applied Mechanics and Engineering
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2009
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Vol. 14, no 4
1073-1092
EN
Unsteady natural convection flow of a viscous and incompressible fluid flow over a vertical cone immersed in a stable thermally stratified medium is theoretically studied in this paper. The dimensionless coupled partial differential boundary layer equations are solved numerically using an efficient and unconditionally stable finite-difference scheme of Crank-Nicolson type. The effects of the Prandtl number and stratification parameter on the velocity and temperature profiles as well as the local and average skin friction and Nusselt numbers on the flow and heat transfer characteristics have been determined and discussed in detail. The present results are compared with available results from the open literature and are found to be in good agreement.
5
Content available remote Numerical solutions for heat and mass transfer effects of an unsteady MHD free convective flow past an infinite vertical plate with constant suction (injection) and heat source
Ambethkar V.
International Journal of Applied Mechanics and Engineering
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2009
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Vol. 14, no 1
67-89
EN
The objective of this work is to study heat and mass transfer in an unsteady MHD free convective flow past an infinite vertical plate with constant suction (injection) and heat source numerically. Dimensionless governing equations of the problem have been solved by using the finite difference technique. Numerical solutions for temperature, velocity, concentration have been obtained for suitable parameters like the Grashof number, mass Grashof number, Prandtl number, Schmidt number and Eckert number. The rates of heat transfer and mass transfer are studied. The results obtained are discussed with the help of graphs and tables to observe the effect of various parameters concerned in the problem under investigation. Effects of suction, the Eckert number and heat source parameter on velocity and temperature distributions are discussed. Stability and convergence of the finite difference scheme is established.
6
Content available remote Flow past an exponentially accelerated vertical plate with heat and mass flux
Muthucumaraswamy R., Sathappan K. E., Natarajan R.
International Journal of Applied Mechanics and Engineering
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2008
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Vol. 13, no 4
979-986
EN
A theoretical solution for an unsteady flow past an exponentially accelerated infinite the vertical plate with prescribed uniform heat and mass flux is analyzed. The plate temperature and the concentration level near the plate are raised at a uniform rate. The dimensionless governing equations are solved using Laplace - transform technique. Velocity, temperature and concentration fields are studied for different physical parameters such as the thermal Grashof number, mass Grashof number, Schmidt number, and time. It is observed that velocity increases with increasing values of [...].
7
Content available remote Hall effects on unsteady free convection slip flow in a rotating fluid along a porous vertical surface bounded by porous medium
Jain N. C., Gupta P.
International Journal of Applied Mechanics and Engineering
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2007
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Vol. 12, no 3
609-627
EN
The present analysis is made to investigate the effects of Hall current on the free convection flow of an incompressible, viscous fluid through a porous medium in a rotating system past an infinite vertical porous plate in the presence of a heat sink and a transversely applied uniform magnetic field. Solutions of velocity and temperature fields are obtained using the perturbation technique. Expressions for the skin motion and heat transfer are also derived. It is found that the increase in the magnetic parameter (M) decreases both the primary skin friction [...] and secondary skin friction [...] while an increase in the Hall parameter (m) decreases [...] but increases [...].
8
Content available Numeryczne badanie wpływu orientacji wzmocnienia na własności aerosprężyste laminatowych płyt wolnonośnych
Olejnik A., Kachel S., Rogólski R., Leszczyński P.
Biuletyn Wojskowej Akademii Technicznej
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2006
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Vol. 55, nr 4
45-70
PL
Niniejszy artykuł dotyczy zagadnienia optymalizacji aerosprężystego układu powierzchniowego w odniesieniu do struktury laminatowej. Przy wspomaganiu komercyjnego pakietu obliczeniowego wykonano serie analiz w zakresie statyki, dynamiki i flatteru wolnonośnych płyt wykonanych z laminatu węglowego. Próba znalezienia optymalnych cech aerosprężystych rozpatrywanych modeli polega na dobraniu najbardziej korzystnej orientacji ułożenia tkaniny względem kierunku odniesienia. Celem doboru różnych kątów ukierunkowania tkaniny jest wybranie konfiguracji o najlepszych własnościach ze względu na odkształcalność statyczną i niestateczność dynamiczną spowodowaną drganiami samowzbudnymi. Dla zaprezentowanych konfiguracji konstrukcyjnych wykonano cykl obliczeń w celu określenia wielkości odkształceń oraz krytycznych prędkości flatteru. Wyniki analiz przedstawiono na rysunkach oraz wykresach ilustrujących zmianę badanego parametru w obliczeniowym zakresie kątów orientacji wzmocnienia.
EN
This paper concerns optimization of aeroelastic surface-shaped system in relation to laminated structure. By the use of one commercial computing program, some analyses were performed on static displacement, dynamics and flutter of cantilevered plates made of carbon fiber laminate. The trial to estimate optimal aeroelastic properties of the considered models consists in matching the best carbon fabric orientation in respect of main reference direction. There could be many laminate orientations in range of 0-90° and the main task is to select the one that gives best properties in respect of static deformations and dynamic instability due to flutter. Some numerical computations were performed for the discussed structure configurations in order to determine displacement sizes and critical flutter airspeeds. The results were shown in the pictures and diagrams illustrating the change of the examined parameter in a computational range of reinforcement orientation angles.
9
Content available remote Transient free convection flow of viscous dissipative fluid past a semi-infinite inclined plate
Ganesan P., Palani G.
International Journal of Applied Mechanics and Engineering
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2003
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Vol. 8, no 3
395-402
EN
An analysis is performed to study the transient free convection flow of a viscous incompressible fluid past a semi-infinite inclined plate with viscous dissipation. The dimensionless governing equations are unsteady, coupled and non-linear integro partial differential equations. An analytical method fails to give a solution. Hence an implicit finite difference scheme of Crank-Nicolson method is employed. The effect of the dissipation parameter on the velocity, temperature, skin friction and Nusselt number are studied in detail. It is observed that greater viscous dissipative heat causes a rise in the temperature irrespective of the Prandtl number.
10
Content available The Modeling of unsteady turbulent flows in turbomachines
Magagnato F.
TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk
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2001
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Vol. 5, No 4
477-494
EN
The suitability of existing models for the simulation of flow through turbomachines is investigated and compared with a recently proposed adaptive turbulence model. Discussed are the improvements in accuracy that can be achieved by using non-linear turbulence models and unsteady calculations. The adaptive turbulence model is based on two equation turbulence modeling. It uses the temporal and spatial scales of the flow field to automatically adapt itself to the unresolved turbulent fluctuations. At its asymptotic limits it reduces either to a Direct Numerical Simulation – when the turbulent scales are in the order of the Kolmogorov micro scale – or to a standard two equation model – when the fluctuations are not resolved at all. In order to compare the quality of the presented models two cases have been considered: the flow past a cylinder and a subsonic as well as transonic flow past the VKI turbine blade. Calculations have been performed for each case using all the models and the results have been compared with measurements. The unsteady calculations gave better agreement with the experimental data demonstrating the superiority over steady state calculations for turbomachines.
11
Content available remote Unsteady combined convection through a porous medium bounded by an infinite vertical isothermal plate
Soundalgekar V. M., Lahurikar R. M., Jaiswal B. S.
International Journal of Applied Mechanics and Engineering
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2001
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Vol. 6, no 4
833-842
EN
A finite-difference solution to the unsteady free and forced convection flow of a dissipative fluid through a homogeneous porous medium past an infinite vertical isothermal plate is derived. Velocity and temperature profiles are shown graphically whereas the numerical values of the skin-friction and the rate of heat transfer are listed in a table. It is observed that the velocity decreases when the permeability parameter 'sigma' or the Grashof number G or the Eckert number E increase. Temperature and the rate of heat transfer are found to increase with increasing 'sigma' but the skin-friction decreases with increasing 'sigma'. The skin-friction decreases with increasing 'sigma'. The skin-friction increases but the rate of heat transfer decreases with increasing G, E (Eckert number) or time t.
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