Defining the thermal conductivity of thermally heterogeneous hollow wall bricks used as elements for increasing the comfort of buildings

The article presents numerical calculation analysis in the scope of determining thermal conductivity coefficient λeq [W/(m·K)] of thermally heterogeneous hollow bricks of thermally heterogeneous structure (a combination of structural material with thermal insulation material). Numerical calculations were conducted by means of professional software TRISCO-KOBRU 86, serving thermal circulation analysis in a 2D field in stationary approach. The analyzed hollow wall bricks may be used, for instance, as a structural layer of layered outer walls of a building. In the article also the results of the Uc thermal conductivity coefficient calculations for double-layer walls with the use of the analyzed hollow wall bricks are presented in regard to thermal requirements.

Effects of a Single Blade Incidence Angle Offset on Adjacent Blades in a Linear Cascade

The paper presents a numerical and experimental investigation of the effect of incindence angle offset in a two-dimensional section of a flat blade cascade in a high-speed wind tunnel. The aim of the current work is tp determine the aerodynamic excitation forces and approximation of the unsteady blade-loading function using a quasi-stationary approach. The numerical simulations were performed with an in-house finite-volume code built on the top of the OpenFOAM framework. The experimental data were acquired for regimes corresponding to the numerical setup. The comparison of the computational and experimental results is shown for the static pressure distributions on three blades and upstream and downstream of the cascade. The plot of the aerodynamic moments acting on all five blades shows that the adjacent blades are significantly influenced by the angular offset of the middle blade.

DATA-BASED PREDICTION OF SOOT EMISSIONS FOR TRANSIENT ENGINE OPERATION

Global vessel traffic is one of the origins responsible for air pollution. Annex VI of the IMO International Convention for the Prevention of Pollution from Ships (MARPOL) focusses on air pollution. Air pollution accrues mainly from energy conversion in combustion engines especially during transient engine operation. One significant pollutant is soot. It represents impure carbon substances in various sizes due to an incomplete combustion of hydrocarbons. This paper focusses on the data-based modelling of soot for transient engine operation in order to predict air pollution in the context of a sophisticated manoeuvring assistance system. In a first step, a stationary approach is investigated and extended for transient engine operation. If one knows about the consequences of his actions, then the role of the human is enforced to decide on energy efficient and emission reduced ship operation, especially during ship manoeuvres.

Street-in-Grid modeling of gas-phase pollutants in Paris city

Regional-scale chemistry-transport models have coarse spatial resolution, and thus can only simulate background concentrations. They fail to simulate the high concentrations observed close to roads and in streets, i.e. where a large part of the urban population lives. Local-scale models may be used to simulate concentrations in streets. They often assume that background concentrations are constant and/or use simplified chemistry. Recently developed, the multi-scale model Street-in-Grid (SinG) estimates gaseous pollutant concentrations simultaneously at local and regional scales, coupling them dynamically. This coupling combines the regional-scale chemistry-transport model Polair3D and the street network model MUNICH (Model of Urban Network of Intersecting Canyons and Highway). MUNICH models explicitly street canyons and intersections, and it is coupled to the first vertical level of the chemical-transport model, enabling the transfer of pollutant mass between the street canyon roof and the atmosphere. The original versions of SinG and MUNICH adopt a stationary hypothesis to estimate pollutant concentrations in streets. Although the computation of NOx concentration is numerically stable with the stationary approach, the partitioning between NO and NO2 is highly dependent on the time step of coupling between transport and chemistry processes. In this study, a new non-stationary approach is presented with a fine coupling between transport and chemistry, leading to numerically stable partitioning between NO and NO2. Simulations of NO, NO2 and NOx concentrations over Paris city with SinG, MUNICH and Polair3D are compared to observations at traffic and urban stations to estimate the added value of multi-scale modeling with a dynamical coupling between the regional and local scales. As expected, the regional chemical-transport model underestimates NO and NO2 concentrations in the streets. However, there is a good agreement between the measurements and the concentrations simulated with MUNICH and SinG. The dynamic coupling between the local and regional scales tends to be important for streets with an intermediate aspect ratio and with high traffic emissions.

Non-Stationary Acceleration Strategies for PageRank Computing

In this work, a non-stationary technique based on the Power method for accelerating the parallel computation of the PageRank vector is proposed and its theoretical convergence analyzed. This iterative non-stationary model, which uses the eigenvector formulation of the PageRank problem, reduces the needed computations for obtaining the PageRank vector by eliminating synchronization points among processes, in such a way that, at each iteration of the Power method, the block of iterate vector assigned to each process can be locally updated more than once, before performing a global synchronization. The parallel implementation of several strategies combining this novel non-stationary approach and the extrapolation methods has been developed using hybrid MPI/OpenMP programming. The experiments have been carried out on a cluster made up of 12 nodes, each one equipped with two Intel Xeon hexacore processors. The behaviour of the proposed parallel algorithms has been studied with realistic datasets, highlighting their performance compared with other parallel techniques for solving the PageRank problem. Concretely, the experimental results show a time reduction of up to 58.4 % in relation to the parallel Power method, when a small number of local updates is performed before each global synchronization, outperforming both the two-stage algorithms and the extrapolation algorithms, more sharply as the number of processes increases.

POSSIBILITY ANALYSIS OF APPLICATION OF GROSS-EQUATIONS, PATHWAYS AND STATIONARY RATES FOR CHEMICAL SYSTEMS IN QUASI-EQUILIBRIUM AND QUASI-STATIONARY APPROACH

Conceptions of pathways, gross-equations and stationary rates were determined for chemical systems in quasi-stationary and quasi-equilibrium approach at different VPR and fast reversible steps.