Global Simulation Model Research Articles

Prediction of SOx and NOx emissions from a medium size biomass boiler

While small and medium size biomass combined heat and power (CHP) plants (i.e., up to 5 MW of electrical rated power) represent an attractive option to exploit locally available biomass resources at low cost, the corresponding investment per unit of rated power significantly rises when the installed power decreases. In these cases, secondary pollutant emissions control measures are most of the time not economically viable and primary emissions control must be used alone to avoid the formation of undesired compounds such as NOx and SOx. Primary control measures require the careful optimization of fuel quality and combustion process. For plant operators, being able to accommodate biomass quality changes in order to minimize the fuel cost can be of great importance in order to guarantee the profitability of the plant. This contribution is dedicated to the development of a zero-dimensional (input–output) combustion simulation model able to predict the pollutants emissions resulting from complete and incomplete combustion with respect to varying combustion operation (ambient temperature, humidity, fumes recirculation, …). This tool is intended to be integrated in a global simulation model of the CHP plant and the attached district heating network installed on the University campus in Liège. Doing so, the plant operation can be optimized with respect to economic as well as environmental and energetic aspects (3E approach) thus ensuring the sustainability of the approach.

Trade and EU accession: The case of Serbia

This paper analyzes the export competitiveness of Serbia vis-a-vis European Union and the possible trade effects of Serbian EU accession scenario. We have observed several macroeconomic variables for determining the external position of Serbia. The trade effects of Serbia's EU accession scenario are evaluated using the partial equilibrium Global Simulation Model (GSIM). The evaluated scenario assumes complete trade liberalization between Serbia and EU, hence, the Serbia's adoption of EU tariffs towards the third parties. We find that Serbia is significantly lagging behind in terms of quality of export products and structural development. Regarding the agricultural products, the simulation predicts the increase in Serbian exports to the EU of 28% compared to pre-accession level. The predicted Serbian imports of agricultural products from the EU increased for 25%. The analysis suggests that Serbian non-agricultural exports to the EU will rise by 12.8% compared to initial trade flows, while the Serbian non-agricultural imports from the EU will rise by 13.4%. The trade simulation implies that Serbia will export more of both agricultural and non-agricultural products to the EU, but less to Russia and rest of the world. Moreover, the model implies that Serbia would be better off with joining the EU in terms of welfare indicators.

Modeling and Simulation of Gait Analysis of Hexapod Robot

In order to solve the key issues such as the improvement of the movement smoothness of the center of mass and the movement coordination of each joint of the legs in the process the movement of the bionic hexapod robot, etc., establish bionic hexapod robot simulation model jointly by observing the movement characteristics and structural characteristics of the hexapod beetle and using three-dimensional modeling software SOLIDWORKS and mechanical system dynamics simulation software ADAMS and build the legs dynamic contact and collision model with the ground through the applied force constraint of ADAMS. Ultimately, form the global dynamics simulation model of the robot. Using the model the triangle gait of bionic hexapod robot is analyze, especially the straight and turning gait, which proves that the movement of robot is stable. The results lay the foundation for the further study and optimization of the bionic hexapod robot.

Dynamic testing and modelling of composite fuselage frames and fasteners for aircraft crash simulations

In crash simulations of composite aircraft fuselage sections, frame breaking, skin bending and failure of mechanically fastened joints can typically be identified as major contributors to crash energy absorption. In order to generate a database for model validations, corresponding static and dynamic tests have been performed on coupon and structural element level to characterise the rate-dependent failure behaviour and energy absorption. Skin-bending, frame-bending and joint-failure tests under pull-out, bearing and peeling loads were performed on 977-2/HTS carbon fibre/epoxy specimens. On the one hand, effects of loading rate on the frame-bending behaviour could be observed. On the other hand, fastener failure did not appear to be depending on loading rate for the test speeds up to 10 m/s involved in this study. Adequate modelling methods in Abaqus/Explicit were derived and validated, and finally applied to a global aircraft crash simulation model.

Enhancement of thermospheric mass density by soft electron precipitation

Enhancements in F‐region electron density and temperature and bottomside Pedersen conductivity caused by soft electron precipitation are shown to enhance the Joule heating per unit mass and the mass density of the thermosphere atF‐region altitudes. The results are derived from the coupled magnetosphere‐ionosphere‐thermosphere model (CMIT) including two types of causally specified soft electron precipitation—direct‐entry cusp precipitation and Alfvén‐wave induced, broadband electron precipitation—the effects of which are self‐consistently included for the first time in a coupled global simulation model. The simulation results provide a causal explanation of CHAMP satellite measurements of statistical enhancements in thermospheric mass density at 400 km altitudes in the cusp and premidnight auroral region.

Spatial distribution of Kelvin‐Helmholtz instability at low‐latitude boundary layer under different solar wind speed conditions

Using the PPMLR‐MHD global simulation model, we examined the Kelvin‐Helmholtz (K‐H) instability at the low‐latitude boundary layer (LLBL) under northward interplanetary magnetic field (IMF) conditions with various solar wind speeds (400, 600, and 800 km/s). The spatial distribution of the K‐H wave power in the equatorial plane shows two distinct power populations, referring to the two modes of K‐H surface waves. The spatial evolution of K‐H instability at the boundary layer is classified into four phases: quasi‐stable, exponential growth, linear growth, and nonlinear phases. The boundary layer is quasi‐stable near the subsolar point region. The K‐H instability starts at about 30° longitude, and grows exponentially with a spatial growth rate of 0.28∼0.87 RE−1until ∼45° longitude where the vortices fully develop. At larger longitudes, the instability grows linearly, while the vortices grow in size. From ∼80° longitude to the distant magnetotail, the K‐H instability develops nonlinearly and the vortices roll up. The wave frequency, wavelength, and phase speed are given at various spatial points. Model results show that the higher solar wind speed generates K‐H waves with higher frequency under the northward IMF, and the wavelengths and the phase speeds increase with the increase of the longitude. Moreover, we made a comparison of the K‐H wave periods on Earth's, Mercury's and Saturn's magnetopauses by a proposed prediction method.

Impact Evaluation of Interoperability Decision Variables on P2P Collaboration Performances

This article deals with the impact evaluation of interoperability decision variables on performance indicators of business processes. The case of partner companies is studied to show the interest of an Interoperability Service Utility (ISU) on business processes in a peer to peer (P2P) collaboration. Information described in the format and the ontology of a broadcasting entity is transformed by ISU into information with the format and the ontology of the receiving entity depending on the available resources of interoperation. These resources can be human operators with defined skill level or software modules of transformation in predefined languages. A design methodology of a global simulation model for estimating the impact of interoperability decision variables on performance indicators of business processes is proposed. Its implementation in an industrial case of collaboration shows its efficiency and its interest to motivate an investment in the technologies of enterprise interoperability.

The Doha Round and Food Security in the Dairy Sector in Cameroon: A Global Simulation Model (GSIM) Approach

In the framework of the new round of trade liberalization launched in Doha, paragraph 13 of the Development Declaration states that members will support special and differential treatment to accommodate development, including food security. This paper simulates scenarios of multilateral tariff reduction from the WTO December 2008 draft modalities on agriculture for the Cameroon dairy sector. Using the Global Simulation Model, the analysis shows a substantial increase in world and domestic consumer prices, as the reduction of bound tariffs does not affect the applied tariffs given the high “binding overhang”. As a consequence, consumers’ welfare decreases.

Effects of Serbian accession to the European Union

In this article, the global simulation model (GSIM) of Joseph F. Francois and Keith H. Hall (2009) for analyzing global, regional, and unilateral trade policy changes was applied to Serbia. This was to measure the effects of full trade liberalization with the EU after Serbian accession to the EU. As anticipated, most of the changes in welfare after full liberalization of trade between Serbia and EU can be expected in sectors where Serbia has specialized; protection against imports from the EU is strong. However, losses could also occur in sectors that currently face strong protection against the rest of the world and this protection is lost after EU accession. Trade liberalization will lead to a substantial loss of tariff revenues. Reduced consumer prices might, on the one hand increase consumer surplus but on the other hand decrease producer surplus and output in certain industries.

Comparative numerical study of the effects of rotating and traveling magnetic fields on the carbon transport in the solution growth of SiC crystals

We present numerical simulations of the high temperature solution growth (HTSG) of silicon carbide (SiC) crystals. From a global simulation model, we investigate the influence of rotating magnetic fields (RMFs) and traveling magnetic fields (TMFs) on the crystal growth rate. The results reveal that heat and mass transfers are affected by magnetic fields. We show that direction of the solute flux must be controlled to increase the growth rate. For example, in presence of TMFs directed downwards the growth rate increases up to three times compared with the pure thermal HTSG. The proposed HTSG system coupled with magnetic fields has the same growth rate possibility as in the sublimation technique.

Comparison of equivalent current systems for the substorm event of 8 March 2008 derived from the global PPMLR-MHD model and the KRM algorithm

Geomagnetic perturbation is an important aspect to determine the capability of a 3-D MHD model in predicting space weather. Taking the substorm event of 8 March 2008 as an example, we compare the equivalent current systems (ECS) in the ionosphere derived from the global PPMLR-MHD simulation model and the ground-based magnetic field observations using the KRM inversion algorithm. The evolution of ECS is utilized to give a global view of the temporal and spatial development of the magnetic fields on the ground. The PPMLR-MHD model has generally reproduced the main characters of the large-scale magnetic field variation on the ground. The magnetic latitude and local time distribution of the ECS is in reasonably agreement with the inversion results during the disturbed period. We hopefully consider the ECS to be a promising numerical forecast product of the global geomagnetic variation from an global 3-D MHD model in the future.

Intensification of the Cowling current in the global MHD simulation model

[1] We examine the effects of the ionospheric conductance on the intensification of the westward electrojet current in the ionosphere based on the piecewise parabolic method with a Lagrangian remap (PPMLR) global MHD simulation model. The ionospheric conductance is empirically linked to the plasma pressure in the plasma sheet. The simulation results are consistent with observations: When the Pedersen and Hall conductances are small, the ionospheric current shows a two-cell pattern; when the conductances increase and the ratio ΣH/ΣP ≥ 2, an intense westward electrojet appears in the midnight sector. This intense westward electrojet is the Cowling current driven by the induced southward electric field due to the blockage of the northward Hall current from closure in the equatorial plasma sheet. The simulation shows the development of the Cowling electrojet is essential to the intensification of the westward electrojet in the ionosphere.

Global-scale hybrid simulation of dayside magnetic reconnection under southward IMF: Structure and evolution of reconnection

[1] Magnetopause reconnection is investigated with our 3-D self-consistent global hybrid simulation model. The magnetic configuration and evolution of Flux Transfer Events (FTEs) and the associated ion density and ion velocity distribution at various locations on the magnetopause are investigated. The results reveal the following. (1) Multiple X lines are formed during the magnetopause reconnection, which lead to both FTEs and quasi-steady-type reconnection under a steady solar wind condition. The resulting bipolar signature of local normal magnetic field of FTEs is consistent with satellite observations. (2) A greater-than-20% plasma temperature rise is seen at the center of a FTE, compared to that of the upstream plasma in the magnetosheath. The temperature enhancement is mainly in the direction parallel to the magnetic field because of the mixing of ion beams. (3) Flux ropes that lead to FTEs form between X lines of finite lengths and evolve relatively independently. The ion density is enhanced within FTE flux ropes because of the trapped particles, leading to a filamentary global density. (4) Different from the previous understanding based on the asymmetric density across the magnetopause, a quadrupole magnetic field signature associated with the Hall effects is found to be present around FTEs. (5) A combination of patchy reconnection and multiple X line reconnection leads to the formation of reconnected field lines from the magnetosphere to IMF, as well as the closed field lines from the magnetosphere to the magnetosphere in the magnetopause boundary layer.

Operation-Oriented Ensemble Data Assimilation of Total Column Ozone

We have developed an advanced data assimilation system for a global ozone simulation model with a four-dimensional ensemble Kalman filter (EnKF). Satellite-measured total column ozone data known as EP/TOMS version 8 were assimilated. Two-month data assimilation cycle experiments were performed from January to February 2001 with three different observing density settings: i) full use of EP/TOMS data points, ii) reduced use of the data points at 1/10, and iii) reduced use of the data points at 1/100. For comparison, additional data assimilation experiments were performed with Newtonian relaxation or a nudging technique. In the case of full use of EP/TOMS data points, the EnKF outperformed the nudging technique by approximately 30% in terms of the root mean square difference in the northern hemisphere midlatitudes. Moreover, the reduced use of EP/TOMS data points demonstrated that the EnKF data assimilation was robust and stable, while the nudging technique was vulnerable to the decrease in observations. Overall, the EnKF is a promising data assimilation technique for the total column ozone and is usable for operational applications.

Effects of solar wind dynamic pressure on the ionospheric O+ fluence during the 31 August 2005 storm

The Multifluid‐Lyon‐Fedder‐Mobarry (MFLFM) global simulation model incorporating an ionospheric cusp O+ outflow model based on an empirical relation between downward DC Poynting flux and O+ outflow flux regulated by the precipitating electron number flux (Fen) is used to simulate the 31 August 2005 storm. A baseline run incorporating the original solar wind data is contrasted against a case where the solar wind dynamic pressure (Pdyn) is artificially adjusted to see what effects this variable has on the O+ fluence generated in the model. Consistent with data, it is found that both the fluence and O+ outflow flux have a positive correlation with the solar wind dynamic pressure. Additionally, changes in Pdyn affect the downward Poynting flux only marginally and regulates both outflow flux and cusp outflow area via Fen. Increases in Pdyn lead to increased cusp electron precipitation, which has the physical effect of enhancing the upwelling O+ population available for outflow.

A statistical study of magnetosphere–ionosphere coupling in the Lyon–Fedder–Mobarry global MHD model

The statistics of magnetosphere–ionosphere (MI) coupling derived from a two-month long run of the Lyon–Fedder–Mobarry (LFM) global simulation model are investigated. MI coupling characteristics such as polar cap potential and field-aligned current (FAC), downward Poynting flux and vorticity of ionospheric convection are compared with observed statistical averages and with results from the Weimer 05 empirical model. The comparisons for eight different IMF clock-angle orientations show that the LFM model produces reasonably accurate average distributions of the Region I and Region II currents. Both current systems have average amplitudes similar to those observed by the Iridium satellite constellation; however, the average LFM amplitudes are smaller by a factor of two compared with the values from the Weimer 05 model. The comparisons of polar cap potential show that the LFM model produces reasonable patterns of ionospheric convection, but the average cross polar cap potential (CPCP) is greater than the observed results by a factor of approximately 2 and greater than Weimer 05 by a factor of 1.5. The differences in convection in LFM results relative to the Weimer 05 model accounts for much of the difference in the Poynting flux patterns and integrated power produced by the two models. The comparisons of average ionospheric field-aligned vorticity show good agreement on the dayside; however, the LFM model gives higher nightside vorticity which may imply that the ionospheric conductance on the nightside is too small in the simulation.

Influence of cusp O+ outflow on magnetotail dynamics in a multifluid MHD model of the magnetosphere

A multifluid version of the Lyon‐Fedder‐Mobarry global simulation model has been used to investigate the effects of outflowing ionospheric O+ on the magnetosphere‐ionosphere system. To quantify these effects, we specify the number density, upward parallel velocity, and temperature of the O+ outflow in a limited area of the low‐altitude simulation boundary representing the projection of cusp, cleft, and low‐latitude boundary layer. A baseline simulation without O+ outflow is compared with simulations with a range of fluxes and initial velocities. In the cases with high fluxes, it is shown that the configuration of the magnetosphere is dramatically changed. In particular, the cross‐polar cap potential is reduced, the polar cap area is increased, and the nightside reconnection line is moved earthward. Furthermore, in one case, the O+ outflow leads to the onset of a second substorm not seen in the other simulation runs.

Formation of a sodium ring in Mercury's magnetosphere

We have performed a statistical analysis of exospheric sodium ion paths in Mercury's magnetosphere under northward interplanetary magnetic field conditions. Electric and magnetic field models used in the simulation were obtained from a global MHD simulation model, whereas the initial conditions of test Na+ ions were derived from a sodium exosphere model. We observe the formation of a ring‐shaped high‐pressure region consisting of energetic sodium ions traveling around the planet close to the equatorial plane. The configuration of this “sodium ring” as well as the acceleration processes leading to its formation strongly depend on the solar wind conditions. When the dynamic pressure is low, most of the Na+ are picked up in the magnetosphere and accelerated by the large‐scale convective electric field. In contrast, in the case of high dynamic pressure, ions that are picked up in the magnetosheath and penetrate into the magnetosphere significantly contribute to the sodium ring. The configuration of this ring also depends upon the intensity of the solar wind electric field. Our analysis reveals that the pressure built by the Na+ ions may be significant as compared to the MHD pressure around the planet.

Numerical simulation of a new SiC growth system by the dual-directional sublimation method

A new SiC growth system using the dual-directional sublimation method was investigated in this study. Induction heating and thermal conditions were computed and analyzed by using a global simulation model, and then the values of growth rate and shear stress in a growing crystal were calculated and compared with those in a conventional system. The results showed that the growth rate of SiC single crystals can be increased by twofold by using the dual-directional sublimation method with little increase in electrical power consumption and that thermal stresses can be reduced due to no constraint of the crucible lid and low temperature gradient in crystals.

Development of the global simulation model of the heliosphere

Abstract The heliospheric structure ranging from the solar surface to the earth’s orbit is self-consistently reproduced from a time-stationary three-dimensional (3D) magnetohydrodynamic (MHD) simulation. The simulation model incorporates gravity, Coriolis, and centrifugal forces into the momentum equation, and coronal heating and field-aligned thermal conduction into the energy equation. The heating term in the present model has its peak at 2.8 solar radius (R s) and exponentially falls to zero at greater distance from the solar surface. The absolute value of heating depends on the topology of the solar magnetic field so as to be in inverse proportion with the magnetic expansion factor. The results of the simulation simultaneously reproduce the plasma-exit structure on the solar surface, the high-temperature region in the corona, the open- and closed-magnetic-field structures in the corona, the fast and slow streams of the solar wind, and the sector structure in the heliosphere.