The Experts below are selected from a list of 4722 Experts worldwide ranked by ideXlab platform
Klaus Sedlbauer - One of the best experts on this subject based on the ideXlab platform.
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vepzo velocity propagating zonal model for the estimation of the Airflow Pattern and temperature distribution in a confined space
Building and Environment, 2012Co-Authors: Victor Norrefeldt, Gunnar Grun, Klaus SedlbauerAbstract:Abstract The goal of this paper is to build a locally refined non-isothermal Airflow model. This model should not need prior knowledge of the expected Airflow Pattern to allow the evaluation of many different configurations. For this a new zonal model, the VEPZO (VElocity Propagating ZOnal) model has been developed including the Airflow velocity as a property of a zone and a viscous loss model to compute the Airflow between the zones. The velocity information from a zone is passed to the flow models and is therefore propagated into the room. Instead of using the power law equation or specialized jet or plume correlations to model the Airflow between two zones, an equation derived from the forces acting on a flow path is used. These forces generate an acceleration or deceleration of the Airflow. Losses are modelled by viscous dissipation. Two other models, the singular loss and the buoyant singular loss model are presented too. These models can be used to model flow paths through e.g. windows or doors. Results using the VEPZO model are compared with data from two case studies used to validate other zonal models. Airflow and temperature distributions are comparable to the results calculated by other zonal models. Furthermore, the VEPZO model is compared to an experimental setup with several interacting heat sources, showing the strength of the approach not needing specialized correlations for these elements. The VEPZO model is implemented in the equation-based and object-oriented language Modelica and can therefore be interfaced to other physical models.
Victor Norrefeldt - One of the best experts on this subject based on the ideXlab platform.
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vepzo velocity propagating zonal model for the prediction of Airflow Pattern and temperature distribution in enclosed spaces
International Modelica Conference, 2012Co-Authors: Victor Norrefeldt, Gunnar GrunAbstract:This paper presents the VEPZO-model (VElocity Propagating ZOnal model), the first three dimensional Airflow model for indoor spaces that has been implemented in Modelica. The model predicts Airflow and temperature distribution in a room. The main feature of the VEPZO model is that each zone has a characteristic velocity depending on entering and leaving Airflows. This characteristic velocity is propagated into space ensuring the propagation of driving Airflows. The VEPZO model can be interfaced to other models of the Modelica.Standard library. In an application example a displacement ventilation in a twin-aisle aircraft cabin is investigated. The temperature in the occupied zones is predicted between 20.6 and 23.0 °C.
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vepzo velocity propagating zonal model for the estimation of the Airflow Pattern and temperature distribution in a confined space
Building and Environment, 2012Co-Authors: Victor Norrefeldt, Gunnar Grun, Klaus SedlbauerAbstract:Abstract The goal of this paper is to build a locally refined non-isothermal Airflow model. This model should not need prior knowledge of the expected Airflow Pattern to allow the evaluation of many different configurations. For this a new zonal model, the VEPZO (VElocity Propagating ZOnal) model has been developed including the Airflow velocity as a property of a zone and a viscous loss model to compute the Airflow between the zones. The velocity information from a zone is passed to the flow models and is therefore propagated into the room. Instead of using the power law equation or specialized jet or plume correlations to model the Airflow between two zones, an equation derived from the forces acting on a flow path is used. These forces generate an acceleration or deceleration of the Airflow. Losses are modelled by viscous dissipation. Two other models, the singular loss and the buoyant singular loss model are presented too. These models can be used to model flow paths through e.g. windows or doors. Results using the VEPZO model are compared with data from two case studies used to validate other zonal models. Airflow and temperature distributions are comparable to the results calculated by other zonal models. Furthermore, the VEPZO model is compared to an experimental setup with several interacting heat sources, showing the strength of the approach not needing specialized correlations for these elements. The VEPZO model is implemented in the equation-based and object-oriented language Modelica and can therefore be interfaced to other physical models.
Hongtao Wang - One of the best experts on this subject based on the ideXlab platform.
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a wind tunnel simulation of the effects of stoss slope on the lee Airflow Pattern over a two dimensional transverse dune
Journal of Geophysical Research, 2007Co-Authors: Zhibao Dong, Guangqiang Qian, Wanyin Luo, Hongtao WangAbstract:[1] Secondary Airflow plays an important role in dune formation and development. The lee Airflow Pattern over transverse dunes is important in determining the shape, alignment, and spacing of dunes and is influenced significantly by the lee slope angle. In this paper we present the results of scaled wind tunnel simulations of the effects of stoss slope on the mean lee Airflow Patterns of transverse dunes. The leeward velocity field was measured nonintrusively using particle image velocimetry to assess the Airflow Pattern. We found that the flow separated over the dunes with a leeward angle close to the slip face angle of natural transverse dunes and was insensitive to stoss angle. Separation cells were characterized by a back eddy. Reattachment distance, height, area, and aspect ratio were used to characterize the separation cell. The first three parameters increased with increasing stoss angle for angles less than 15° but remained constant or decreased slightly with angles greater than 15°. On the basis of the leeward velocity profiles, six flow regions corresponding to those in previous models were recognized. These regions are initially bounded by kinks but gradually transition downwind and merge to recover a uniform velocity profile after a significant distance. We suggest that the separation cell is most developed when the angle of stoss slope reaches 15°, but the significance of this angle in the evolution of transverse dunes needs further exploration.
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A wind tunnel simulation of the effects of stoss slope on the lee Airflow Pattern over a two‐dimensional transverse dune
Journal of Geophysical Research, 2007Co-Authors: Zhibao Dong, Guangqiang Qian, Wanyin Luo, Hongtao WangAbstract:[1] Secondary Airflow plays an important role in dune formation and development. The lee Airflow Pattern over transverse dunes is important in determining the shape, alignment, and spacing of dunes and is influenced significantly by the lee slope angle. In this paper we present the results of scaled wind tunnel simulations of the effects of stoss slope on the mean lee Airflow Patterns of transverse dunes. The leeward velocity field was measured nonintrusively using particle image velocimetry to assess the Airflow Pattern. We found that the flow separated over the dunes with a leeward angle close to the slip face angle of natural transverse dunes and was insensitive to stoss angle. Separation cells were characterized by a back eddy. Reattachment distance, height, area, and aspect ratio were used to characterize the separation cell. The first three parameters increased with increasing stoss angle for angles less than 15° but remained constant or decreased slightly with angles greater than 15°. On the basis of the leeward velocity profiles, six flow regions corresponding to those in previous models were recognized. These regions are initially bounded by kinks but gradually transition downwind and merge to recover a uniform velocity profile after a significant distance. We suggest that the separation cell is most developed when the angle of stoss slope reaches 15°, but the significance of this angle in the evolution of transverse dunes needs further exploration.
Gunnar Grun - One of the best experts on this subject based on the ideXlab platform.
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vepzo velocity propagating zonal model for the prediction of Airflow Pattern and temperature distribution in enclosed spaces
International Modelica Conference, 2012Co-Authors: Victor Norrefeldt, Gunnar GrunAbstract:This paper presents the VEPZO-model (VElocity Propagating ZOnal model), the first three dimensional Airflow model for indoor spaces that has been implemented in Modelica. The model predicts Airflow and temperature distribution in a room. The main feature of the VEPZO model is that each zone has a characteristic velocity depending on entering and leaving Airflows. This characteristic velocity is propagated into space ensuring the propagation of driving Airflows. The VEPZO model can be interfaced to other models of the Modelica.Standard library. In an application example a displacement ventilation in a twin-aisle aircraft cabin is investigated. The temperature in the occupied zones is predicted between 20.6 and 23.0 °C.
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vepzo velocity propagating zonal model for the estimation of the Airflow Pattern and temperature distribution in a confined space
Building and Environment, 2012Co-Authors: Victor Norrefeldt, Gunnar Grun, Klaus SedlbauerAbstract:Abstract The goal of this paper is to build a locally refined non-isothermal Airflow model. This model should not need prior knowledge of the expected Airflow Pattern to allow the evaluation of many different configurations. For this a new zonal model, the VEPZO (VElocity Propagating ZOnal) model has been developed including the Airflow velocity as a property of a zone and a viscous loss model to compute the Airflow between the zones. The velocity information from a zone is passed to the flow models and is therefore propagated into the room. Instead of using the power law equation or specialized jet or plume correlations to model the Airflow between two zones, an equation derived from the forces acting on a flow path is used. These forces generate an acceleration or deceleration of the Airflow. Losses are modelled by viscous dissipation. Two other models, the singular loss and the buoyant singular loss model are presented too. These models can be used to model flow paths through e.g. windows or doors. Results using the VEPZO model are compared with data from two case studies used to validate other zonal models. Airflow and temperature distributions are comparable to the results calculated by other zonal models. Furthermore, the VEPZO model is compared to an experimental setup with several interacting heat sources, showing the strength of the approach not needing specialized correlations for these elements. The VEPZO model is implemented in the equation-based and object-oriented language Modelica and can therefore be interfaced to other physical models.
Hans Martin Mathisen - One of the best experts on this subject based on the ideXlab platform.
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displacement ventilation the influence of the characteristics of the supply air terminal device on the Airflow Pattern
Indoor Air, 1991Co-Authors: Hans Martin MathisenAbstract:Displacement ventilation is acknowledged to be an efficient system for the removal of contaminants and excess heat from occupied zones of rooms. However, Airflow rates, temperature and the design of the air supply device strongly influence the parameters which determine thermal comfort. This paper reviews experiments and theoretical models which show the connection between these parameters. The width and shape of the air supply device have been varied, and a porous media has been used on the inlet area of the air supply device. The velocity and temperature profiles have been measured. The results presented show also that the flow can be described with respect to width and form of the profiles for temperature and velocity. The flow does not operate like a turbulent jet due to thermal stratification. It is shown that the Archimedes number of the supply air is the parameter which determines the air velocity in the area close to the floor. (The Archimedes number is here defined as the ratio between buoyancy and inertia forces.) The results show that it is possible to remove considerable amounts of excess heat from a room, typically 40-50 W/m2, without exceeding the limits for thermal comfort. However, this requires relatively high Airflow rates and supply air terminal units at least along one of the walls.
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Displacement Ventilation ‐ the Influence of the Characteristics of the Supply Air Terminal Device on the Airflow Pattern
Indoor Air, 1991Co-Authors: Hans Martin MathisenAbstract:Displacement ventilation is acknowledged to be an efficient system for the removal of contaminants and excess heat from occupied zones of rooms. However, Airflow rates, temperature and the design of the air supply device strongly influence the parameters which determine thermal comfort. This paper reviews experiments and theoretical models which show the connection between these parameters. The width and shape of the air supply device have been varied, and a porous media has been used on the inlet area of the air supply device. The velocity and temperature profiles have been measured. The results presented show also that the flow can be described with respect to width and form of the profiles for temperature and velocity. The flow does not operate like a turbulent jet due to thermal stratification. It is shown that the Archimedes number of the supply air is the parameter which determines the air velocity in the area close to the floor. (The Archimedes number is here defined as the ratio between buoyancy and inertia forces.) The results show that it is possible to remove considerable amounts of excess heat from a room, typically 40-50 W/m2, without exceeding the limits for thermal comfort. However, this requires relatively high Airflow rates and supply air terminal units at least along one of the walls.
