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Showing 3 results for Model Building
Farzad Bazdidi-Tehrani, Akbar Mohammadi-Ahmar, Mohsen Kiamansouri,
Volume 14, Issue 6 (9-2014)
Abstract
The present paper investigated the capability of various non-linear k–ε models for predicting flow field and pollutant dispersion around a cubical model building with a stack vent located on its roof center within the turbulent boundary layer. One quadratic model proposed by Nisizima and Yoshizawa, and two cubic models, proposed by Lien et al. and Ehrhard and Moussiopoulos were examined by comparing their simulation results with the wind tunnel data and standard k–ε model. All the computations were performed by using the self-developed object-oriented C++ programming in OpenFOAM CFD package, which contains applications and utilities for finite volume solvers. The standard k–ε model provided inadequate results for the flow field, because it could not reproduce the basic flow structures, such as reverse flow on the roof. By contrast, the non-linear models were able to predict anisotropic stresses and correctly showed the dominant stress over the roof to be the streamwise Reynolds stress. The non-linear models were able to predict the concentration field better than the SKE model due to inclusion of the quadratic and cubic terms. Among the RANS models, the Ehrhard model showed the best agreement with the experimental data. It was shown that concentrations predicted by all turbulence models were less diffusive than those of the experiment, although the non-linear k–ε models have reduced this difference.
Volume 22, Issue 4 (2-2019)
Abstract
In recent years, in system dynamics society has increased attention to qualitative approaches. One method of extracting models of qualitative system dynamics has been many used is a Group Model Building. In this method, clients are involved in the modeling process. But it has not been systematically studied to assess the effectiveness of Group modeling. Systematically assess is important because the following reasons: 1) understand the impact of this approach on the customer and target organizations; 2) Enhance the effectiveness of a modeling process. In this paper we have evaluated a Group modeling that was used in the design of aviation Technology Park by a questionnaire was filled out by participants after modeling sessions. The results of this survey indicate that participants acknowledged the importance, usefulness and the efficiency of these sessions. Also in the regard of meetings, open discussion, external facilitator and meetings as a group, using cause and effect diagrams, images and graphics to visualize the process, meetings outside the office environment, using workbook and the clear instructions in the meetings are important. Participants Expressed the Informal meetings have been useful.
Volume 24, Issue 4 (12-2020)
Abstract
The systems dynamics emphasize the participation of individuals in modeling as well as modeling evaluation. In recent years, participative model building methods have been developed, both individually and in groups, as well as crowd model building, which are based on the mass participation of people through the Web 2 and social networks. However, so far no systematic study has been done to evaluate the effectiveness and compare these modeling methods. On the other hand, in the development of modeling methods, especially crowd model building; special features and characteristics have been enumerated for each of them, which needs to be carefully examined by evaluating them. Therefore, this article seeks to systematically evaluate and compare the crowd and group model building. For this purpose, these two modeling methods have been studied through an online questionnaire. The results showed that the participants acknowledged the positive effect of crowd and group model building sessions in achieving the goals as well as the importance and usefulness of these sessions. However, the results showed that crowd model building is more useful in recognizing different dimensions of crowdfunding with a divergent view, dissemination of topics, and culture building in society, while group model building has been more useful in deepening peoplechr('39')s knowledge of the dimensions of crowdfunding with a convergent view, increasing the commitment of individuals. The results also showed that the diversity of individuals and the informal structure of the sessions have a significant effect on the success of crowd and group model building.
