Vol. 22, No 3, 2018 < Volumes
(ISSN 1428-6394)



hMichal Saczek, Karol Wawrzak, Artur Tyliszczak and Andrzej Boguslawski Hybrid MPI/Open-MP Acceleration Approach for High-Order Schemes for CFD

The paper presents a hybrid MPI + OpenMP (Message Passing Interface/Open Multi-Processor) algorithm used for parallel programs based on the high-order compact method. The main tools used to implement parallelism in computations are OpenMP and MPI which differ in terms of memory on which they are based. OpenMP works on shared-memory and the MPI on distributed-memory whereas the hybrid model is based on a combination of those methods. The tests performed and described in this paper present significant advantages provided by a combination of the MPI/OpenMP approach. The test computations needed for verifying possibilities of MPI, Open-MP and Hybrid of both tools were carried out using an academic high-order SAILOR solver. The obtained results seem to be very promising to accelerate simulations of fluid flows as well as for application using high order methods.


hKrzysztof Rogowski and Klaudia Rogowska Velocity Field around Darrieus Wind Turbine Rotor Using Actuator Cell Model and Other CFD Methods

The main purpose of this work is to analyze the usefulness of the active cell model (ACM) developed by the author of this article to estimate the flow field around a single-bladed vertical-axis wind turbine (VAWT) with the Darrieus-type rotor. The obtained flow velocity fields were compared with the experimental values taken from the literature available on the Internet. Additionally, the flow fields around the rotor and the aerodynamic forces were determined using the following approaches: the k-ε RNG turbulence model, the scale-adaptive simulation (SAS) and the laminar model. The velocity profiles behind the turbine rotor obtained with all numerical approaches are consistent with the experiment. The aerodynamic blade loads obtained using numerical methods also appear to be satisfactory.


hPaweł Ziółkowski, Michał Stajnke, Paweł Jóźwik, Zbigniew Bojar, Piotr Józef Ziółkowski and Janusz Badur Numerical Analysis of Species Diffusion and Methanol Decomposition in Thermocatalytic Reactor Based on the Intermetallic Phase of Ni{3}Al for Low Reynolds Numbers

Numerical modelling of hydrogen production by means of methanol decomposition in a thermocatalytic reactor using corrugated foil made of the Ni3 Al intermetallic phase is shown in the paper. Experimental results of the flow analysis of mixtures containing helium and methanol in a thermocatalytic reactor with microchannels were used for the initial calibration of the CFD calculations (calculations based on the Computational Fluid Dynamics method). The reaction of the thermocatalytic methanol decomposition was modelled based on experimental data, considering the size of the active surface. The drop in the methanol concentration at 212 P. Ziółkowski, M. Stajnke, P. Jóźwik, Z. Bojar, P. J. Ziółkowski and J. Badur the inlet to the reactor, ten millimetres in front of the thermocatalytic region, is associated with the diffusion of streams of other components, mainly hydrogen and carbon monoxide. The commercial CFD code was expanded by User Defined Functions (UDFs) to include surface chemical reaction rates in the interphase between the fluid and the solid. Extrapolation of data by means of the implemented numerical model enabled the assessment of the minimum length of microreactor channels and prediction of the optimal dimension at the system outlet. The results obtained by means of numerical calculations were calibrated and compared with the experimental data, confirming a satisfactory consistency of the data.


hBeata Jaworska-Jóźwiak Decreasing Wall Shear Stress in Hydromixture Flow after Deflocculant Application

The aim of the paper is to present the influence of selected deflocculants on decreasing the hydromixture viscosity and as a consequence decreasing the wall shear stresses in a flowing medium. Adding deflocculants to improve the conditions encountered in a pipeline during the hydromixture flow is called chemical processing. The experimental studies presented in the article were performed for a hydromixture with a mass concentration of 20% and 43% consisting mostly of solids with the averaged diameter equal to 45.5 μm. The measurements were performed for varied doses of deflocculants in three proportions in a wide range of shear rates. The results of experiments have confirmed that the influence of the deflocculant on the wall shear stress is complex as there is an opposing phenomenon strongly depending on the doses of deflocculant samples. The results of the experiments are discussed and major conclusions are drawn.


hSergey Leble and Ekaterina Smirnova Tsunami-Driven Plane Acoustic Waves in the Atmosphere

A problem of analytical-numerical modeling of the plane wave propagation from an ocean surface to the atmosphere is considered. We are interested in the thermosphere impact of tsunami waves. We suppose that the transport of energy and the momentum from lower atmosphere to thermosphere heights is due to acoustic waves. A set of expressions for the atmosphere variables (pressure, velocity, entropy) as a function of the atmosphere parameters, time and height is derived and illustrated by plots. The surface water wave parameters, typical for tsunami also enter final expressions for the atmosphere and ionosphere variables.


hV. Uruba, P. Procházka and V. Skála On Streamwise Structures in Boundary Layer under Adverse Pressure Gradient on Inclined Plate

The presented study is focused on experimental investigation of a boundary layer on a flat plate in an adverse pressure gradient. The flat plate is placed in a regular flow, the pressure gradient is generated by the plate inclination. The preceding studies deal with the structure of the wake behind the plate, the presented study concentrates on the flow structure close to the suction surface of the plate. The dynamical behavior of the flow structures is studied in details with respect to the topology in the streamwise direction. In spite of the fact that the time-mean flow field is close to 2D, more or less constant along the span, the instantaneous structures topology is fully 3D. Rather oblique structures are detected instead of those oriented in the streamwise direction. The patterns are travelling in the streamwise direction along the plate.


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