Numerical simulation of airflow distribution in mine tunnels

Based on 3D modelling of typical tunnels in mines, the airflow distribution in a three-center arch-section tunnel is investigated and the influence of air velocity and cross section on airflow distribution in tunnels is studied. The average velocity points were analyzed quantitatively. The results show that the airflow pattern is similar for the three-center arch section under different ventilation velocities and cross sectional areas. The shape of the tunnel cross section and wall are the critical factors influencing the airflow pattern. The average velocity points are mainly close to the tunnel wall. Characteristic equations are developed to describe the average velocity distribution, and provide a theoretical basis for accurately measuring the average velocity in mine tunnels.

CFD-Based Evaluation of Flowand Temperature Characteristics of Airflow in an Aircraft Cockpit

The rational design of airflow distribution is of great importance for comfort and energy conservation.Several numerical investigations of flow and temperature characteristics in cockpits have been performed to study the distinct airflow distribution.This study developed the coupled heat transfer model of radiation,convection,and heat conduction for the cockpit flight environment.A three-dimensional physical model was created and a shear stress transfer(SST)k-w turbulence model was well verified with a high prediction accuracy of 91%for the experimental data.The strong inhomogeneous flow and temperature distribution were captured for various initial operating conditions(inlet temperature,inlet pressure,and gravitational acceleration).The results indicated that the common feature of the flow field was stable in the middle part of the cockpit,while the temperature field showed a large temperature gradient near the cockpit’s top region.It was also found that there was remarkable consistency in the distributed features,regardless of the applied initial operating conditions.Additionally,the mass flux and the top heat source greatly affected the flow and temperature characteristics.This study suggests that an optimized operating condition does exist and that this condition makes the flow and temperature field more stable in the cockpit.The corresponding results can provide necessary theoretical guidance for the further design of the cockpit structure.

The characteristics of sea fog with different airflow over the Huanghai Sea in boreal spring

Using the observations from ICOADS datasets and contemporaneous NCEP/NCAR reanalysis datasets during 1960-2002,the study classifies the airflows in favor of sea fog over the Huanghai （Yellow） Sea in boreal spring （April-May） with the method of trajectory analysis,and analyzes the changes of proportions of warm and cold sea fogs along different paths of airflow.According to the heat balance equation,we investigate the relationships between the marine meteorological conditions and the proportion of warm and cold sea fog along different airflow paths.The major results are summarized as follows.（1） Sea fogs over the Huanghai Sea in spring are not only warm fog but also cold fog.The proportion of warm fog only accounts for 44% in April,while increases as high as 57% in May.（2） Four primary airflow paths leading to spring sea fog are identified.They are originated from the northwest,east,southeast and southwest of the Huanghai Sea,respectively.The occurrence ratios of the warm sea fog along the east and southeast airflow paths are high of 55% and 70%,while these along the southwest and northwest airflow paths are merely 17.9% and 50%.（3） The key physical processes governing the warm/cold sea fog are heat advection transport,longwave radiation cooling at fog top,solar shortwave warming and latent heat flux between airsea interfaces.（4） The characteristics of sea fog along the four airflow paths relate closely to the conditions of water vapor advection,and the vertical distribution of relative humidity.