Accelerated RAPID Model Using Heterogeneous Porous Objects

To enhance the capability of three-dimensional (3D) radiative transfer models at the kilometer scale (km-scale), the radiosity applicable to porous individual objects (RAPID) model has been upgraded to RAPID3. The major innovation is that the homogeneous porous object concept (HOMOBJ) used for a tree crown scale is extended to a heterogeneous porous object (HETOBJ) for a forest plot scale. Correspondingly, the radiosity-graphics-combined method has been extended from HOMOBJ to HETOBJ, including the random dynamic projection algorithm, the updated modules of view factors, the single scattering estimation, the multiple scattering solutions, and the bidirectional reflectance factor (BRF) calculations. Five cases of the third radiation transfer model intercomparison (RAMI-3) have been used to verify RAPID3 by the RAMI-3 online checker. Seven scenes with different degrees of topography (valleys and hills) at 500 m size have also been simulated. Using a personal computer (CPU 2.5 GHz, memory 4 GB), the computation time of BRF at 500 m is only approximately 13 min per scene. The mean root mean square error is 0.015. RAPID3 simulated the enhanced contrast of BRF between backward and forward directions due to topography. RAPID3 has been integrated into the free RAPID platform, which should be very useful for the remote sensing community. In addition, the HETOBJ concept may also be useful for the speedup of ray tracing models.

The Features of Parallel Program for 3-D Modeling of Dynamic Processes in Porous Objects with Heat-Evolution

The 3-D OpenMP parallel version of an algorithm for modeling dynamic processes in porous media with heat-evolution sources is presented. Parallel methods and techniques which were used for significant speed up of final results obtaining are described in detail. The performance results of parallel program for specific configuration of porous object are presented.

Numerical Comparison of Gas Flows through Plane Porous Heat-Evolutional Object with Axisymmetric one when Object's Outlet is Partially Closed

Using numerical experiment the gas flow in the gravity field through a plane porous object with heat sources inside and partial closure of the object's outlet has been investigated and compared with axisymmetric case. The influence of partial closure of the object's outlet on the cooling process of the plane porous objects with a non-uniform distribution of heat sources has been analyzed by means of computational experiment. It has been revealed that effect of the top cover on a cooling process of the plane porous objects is qualitatively the same as in the axisymmetric objects, but quantitative differences are significant.

Numerical Comparison of Heterogeneous Combustion Waves in Horizontal and Vertical Porous Objects under Free Convection

Using numerical experiment one-dimensional unsteady processes of heterogeneous combustion in porous object under free convection in horizontal case have been investigated and compared with vertical case. It is shown that in the case of the horizontal porous object the oxidizer supply, which is the result of natural convection, is not sufficient for the appearance of stable wave of heterogeneous combustion. In contrast to the vertical position of the object, there are no long-lived combustion waves in the horizontal case, which completely burns down the solid combustible material. When the ignition zone is on the border of the object, the combustion wave near the vicinity of the boundary burns the oxygen and becomes extinct. When the ignition zone is in the center of the porous object, two combustion waves arise which may move very slowly, burn oxygen and become extinct.

Numerical Method for Investigation of 1D Processes in Porous Media with Heterogeneous Reactions when Flow Rate of Oxidant Regulates itself

The time-dependent gas flows through porous objects with heterogeneous reactions are considered when the gas pressure at object boundaries is known but the flow rate and velocity of the gas filtration at the inlet to the porous objects are unknown. In such porous objects the flow rate of oxidant, which enters into the reaction zone in porous object, regulates itself. An original numerical method, based on a combination of explicit and implicit finite-difference schemes, have been developed for investigating the unsteady gas flows in such porous objects with zones of heterogeneous reactions. Used approach enables to solve problems of filtration combustion for both forced filtration and free convection, so it can be efficiently applied for modeling the combustion zones in porous media, which may arise from natural or man-caused disasters.