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To date, few studies have been conducted on the characteristics of flow and dispersion caused by indoor radiant floor heating integrated with natural ventilation. In this study, we employed reduced−scale numerical models validated by wind−tunnel experiments to investigate the influence of radiant floor heating integrated with natural ventilation on airflow, heat transfer, and pollutant dispersion within an isolated building. The Richardson number (Ri) was specified to characterize the interaction between the inflow inertia force and the buoyancy force caused by radiant floor heating. Several Ri cases from 0 to 26.65, coupled with cross− or single−sided ventilation, were considered. Model validation showed that the numerical model coupled with the RNG k-ε model was able to better predict the indoor buoyant flow and pollutant dispersion. The results showed that the similarity criterion of Ri equality should be first satisfied in order to study indoor mixed convection using the reduced−scale model, followed by Re−independence. For cross−ventilation, when Ri < 5.31, the incoming flow inertia force mainly dominates the indoor flow structure so that the ACH, indoor temperature, and pollutant distributions remain almost constant. When Ri > 5.31, the thermal buoyancy force becomes increasingly important, causing significant changes in indoor flow structures. However, for single−sided ventilation, when Ri > 5.31 and continues to increase, the buoyancy force mainly dominates the indoor flow structure, causing a significant increase in ACH, thus reducing the indoor average temperature and pollutant accumulation.

Configuration of street canyon and the wind environment have a great influence on the self-ventilation capacity of the canyon, but the couple-effect of these two factors could not be considered in the previous study. The purpose of this study is to clarify the couple effect of street canyon configuration and wind environment on the ventilation and pollutant dispersion inside the street canyon. For this purpose, five wind directions of α = 90°, 60°, 45°, 30°, and 0° (α is the angle between the approaching wind and street canyon) and three canyon configurations (flat, step-up, and step-down canyons) were considered with numerical simulation and wind-tunnel experiment. Meanwhile, ACH (air exchange rate) and NEV (net escape velocity) were used to evaluate the ventilation capacity of the canyon. The results reveal that the wind direction has a vital influence on the ventilation in the different canyon configurations. Under the parallel wind direction (α = 0°), the airflow and ventilation capacity inside the three canyons are similar. Relative difference of ACH, named as RDA ((ACH

A physical model consisting of two parallel street canyons with the fire room located in the windward side of the first street canyon was established. Large eddy simulation (LES) was employed to investigate the effects of air pollutant dispersion caused by the fire-induced buoyancy plume on the indoor and outdoor air quality. The effect of thermal buoyancy was firstly taken into account by burning the smoke cakes in wind-tunnel experiments under different Fr (Froude number) cases. Results show that the diffusion characteristics of smoke plume, temperature and velocity distributions by wind-tunnel measurements agreed well with the numerical models. According to the smoke soot’s effects on two street canyons, the dispersion of fire pollutants can be divided into three regimes. There exist two critical Fr, Frcrit,1 = 0.313 and Frcrit,2 = 0.389, at which the smoke plume begins to influence the 1st and 2nd street canyons, respectively. Moreover, the region areas of w

In general, urban canyons are the areas most clearly affected by traffic pollutants since the ability of the canyon to self-ventilate is inhibited due to blockage of buildings or other urban structures. However, previous studies have aimed to improve the pedestrian-level wind speed with void deck in single buildings or short canyons. This study investigated the effects of void deck height and location, and the building height on the airflow field and the traffic pollutant diffusion in a long canyon with L/H = 10, validated by wind-tunnel experiment data. The results show that the void decks have a significant effect on the airflow and pollutant distribution inside the canyon. Air exchange rates (ACH) of the canyons with the void deck are much larger than that of regular canyons, and the perturbation changes of turbulence (ACH') decrease. For the windward void deck, purging flow rate (PFR) and normalized net escape velocity (NEV*) increase by 6.4 times compared to the regular canyon, and for the leeward void deck, increase by 13 times. In particular, when the void decks are at both buildings, they are increased by 38.3 times. Also, for the canyons with the void deck, traffic pollutants are removed out of the canyon by the strong airflow through the void deck. Therefore, unlike the regular canyons, as the void deck and the building height increases, the strength of the airflow through the void deck becomes stronger, and as a result, the mean pollutant concentration is significantly reduced at both walls and the pedestrian respiration level. The mean pollutant concentration on the wall of the building with the void deck and on the pedestrian respiration plane close to it is near zero. These findings can help ease traffic pollution inside the street canyons composed of high-rise buildings, especially in tropical cities.

This study conducted the numerical models validated by wind-tunnel experiments to investigate the issues of Re-independence of indoor airflow and pollutant dispersion within an isolated building. The window Reynolds number (Rew ) was specified to characterize the indoor flow and dispersion. The indicators of RRC (ratio of relative change) or DR (K_DR) (difference ratio of dimensionless concentration) ≤ 5% were applied to quantitatively determine the critical Rew for indoor flow and turbulent diffusion. The results show that the critical Re (Recrit) value is position-dependent, and Recrit at the most unfavorable position should be suggested as the optimal value within the whole areas of interest. Thus ReH,crit = 27,000 is recommended for the outdoor flows; while Rew,crit = 15,000 is determined for the indoor flows due to the lower part below the window showing the most unfavorable. The suggested Rew,crit (=15,000) for indoor airflow and cross ventilation is independence of the window size. Moreover, taking K_DR ≤ 5% as the indicator, the suggested Rew,crit for ensuring indoor pollutant diffusion enter the Re-independence regime should also be 15,000, indicating that indoor passive diffusion is completely determined by the flow structures. The contours of dimensionless velocity (U/U0) and concentration (K) against the increasing Rew further confirmed this critical value. This study further reveals the Re-independence issues for indoor flow and dispersion to ensure the reliability of the data obtained by reduced-scale numerical or wind-tunnel models.

Polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), two typical persistent organic pollutants, are the research focus due to their mutagenesis, carcinogenesis, teratogenesis, and bioaccumulation. The content distribution and residual characteristics of PAHs and PCBs were investigated in the sediments from the Sanya River. Source apportionment was further explored based on the analysis of the spatial distribution, and the ecological risk evaluation was carried out with the sediment quality criteria and standards. The results indicate that the content of ΣPAHs and ΣPCBs in the sediment range from 265.00 μg·kg

There is an increasing concern on the effect of the outdoor environment on the indoor air quality (IAQ) through ventilation. In urban areas, the physical phenomenon that the air pollutants pass over the neighborhood scale–street scale–indoor scale, and affect the health of the residents belongs to multiscale problems. The adopted multiscale method models the problem in nesting grid system approach by solving from top (entire domain with relative coarse grids) to down (subsequent sub-domains with finer grid). In this paper, a 3-D multiscale model with Richardson number (Ri) equal to 0.85 was firstly established to investigate the above multiscale phenomenon, then evaluated by comparing with the full-scale intensive simulation, since our previous study showed that when Ri ≤ 0.85 the standard k-ɛ turbulence model can better predict the flow and temperature fields. The numerical error analysis of the multiscale method was conducted by considering the effects of two aspects (boundary condition interpolation schemes and sub-domain partitioning) on the regularity of error production and transfer. Results show that the applied multiscale method can save 83.8% computing time. Furthermore, it can be concluded that among the three interpolation schemes for the boundary reconstruction the linear and spline interpolation methods are appropriate while the nearest method should not be applied because of its 1st-order accuracy. If insensitive interfaces are chosen as the partitioning interfaces of the lower-scale domain the computational accuracy of the multiscale method can be greatly improved.

This study investigates the effects of wind direction on the airflow and pollutant dispersion inside a long street canyon using computational fluid dynamics (CFD). A 3D CFD model for predicting the flow and dispersion in a canyon is first developed using the FLUENT code and then validated against wind tunnel experiments. Then, the airflow and traffic pollutant dispersion in an isolated canyon with a street-length-to-building-height ratio of 10 are numerically simulated for seven wind directions (α = 0°, 15°, 30°, 45°, 60°, 75° and 90°, where α is the angle between the approaching flow and street axis). The results demonstrate that the mean (ACH) and turbulent (ACHʹ) air exchange rates (ACHs) for the canyon are close when α = 0°, 15°, 30°, 45° and 60°, whereas the magnitude of ACHʹ is significantly greater than that of ACH when α = 75° and 90°. Additionally, the ACH reaches its maximum and minimum values when α = 30° and 90°, respectively. The computed velocity and concentration fields clearly reveal the variation in the in-canyon flow pattern and pollutant distributions on the canyon walls and footpaths due to the wind direction. Evaluating the maximum, minimum and average concentrations on the canyon walls and footpaths for each of the seven wind directions, we determine: On the leeward-oriented wall, the wall-averaged concentration increases greatly with α, and the values of the wall-maximum are highest when α = 75° and lowest when α = 0°. By contrast, on the windward-oriented wall, both the wall-averaged and wall-maximum concentrations are highest when α = 0°. Finally, at the human respiration height, the highest concentration on the footpath next to the leeward-oriented wall occurs when α = 75°, whereas the highest concentration on the footpath close to the windward-oriented wall is observed when α = 0°.

A mistake of applying pseudo-first-order (PFO) kinetic model in the three papers has been pointed out. Also a correct PFO kinetic equation is given. In addition, a suggestion is made for avoiding using erroneous PFO kinetic equations in adsorption systems.

In the design and development of liquid breeder blankets, a number of duct geometries are considered, such as the multiple channel, U-turn duct and T-shaped duct. In the presence of the magnetic field, the motion of electrically-conducting liquid metal leads to Megnetohydrodynamic phenomena, as results of the liquid metal flow profile changes inside the flow channels and additional pressure drop of liquid breeder blankets. A three-dimensional liquid-metal (LM) magnetohydrodynamic (MHD) flows in a U-turn duct with large aspect ratio of the duct cross-section of the connecting channel and in a U-turn conduit with manifold in the connecting region is studied, respectively. Here, the effects of the electrical conductivity of the separating wall in the manifold and different Hartmann numbers on the flow features are considered. Since the 3-D currents are induced due to the complicated geometrical flow path, the electrical conductivity of the separating wall plays a key role in the distribution of mass flow rate among the parallel ducts in manifold. Thus, in the present study, the distribution of the mass flow rate is analyzed for different electrical conductivity of the structural walls. Furthermore, since the aim of the optimal design of liquid-metal blanket is to achieve a proper velocity distribution and reduce the pressure drop caused by the flow opposing Lorentz force, the investigation of the effect of the duct geometry on the pressure distribution in this study is significant.

Objective: To study the change of serum tumor markers and lesion cancer cell proliferation gene expression after Nimotuzumab combined with cisplatin and radiotherapy treatment of middle-advanced cervical cancer. Methods: A total of 78 patients with middle-advanced cervical cancer who were treated in our hospital between August 2013 and February 2016 were collected and divided into the control group (n=39) who received routine radiotherapy and chemotherapy and the observation group (n=39) who received Nimotuzumab combined with cisplatin and radiotherapy according to the single-blind randomized control method, and both groups were treated for 6 weeks. Before treatment and after 6 weeks of treatment, enzymelinked immunosorbent assay (ELISA) was used to detect serum tumor marker levels, and fluorescence quantitative PCR method was used to detect the lesion proliferation gene mRNA expression. Results: Before treatment, the differences in serum tumor marker levels and lesion proliferation gene mRNA expression were not statistically significant between two groups of group. After 6 weeks of treatment, serum tumor markers SCC, CA125 and CA19-9 levels of observation group were lower than those of control group, lesion pro-proliferation genes B7- H4, HIF-1毩, Sp2 and PCNA mRNA expression were lower than those of control group, and lesion anti-proliferation genes PTEN, FHIT and STC1 mRNA expression were higher than those of control group. Conclusion: Nimotuzumab combined with cisplatin and radiotherapy can effectively reduce the serum tumor marker levels, and also inhibit the lesion cancer cell proliferation in patients with middle-advanced cervical cancer.

This paper presents Computational Fluid Dynamics (CFD) simulations to evaluate the impacts of the upstream building height and stack location on the dispersion of the pollutant released from a rooftop stack. The simulations are performed with the 3D, steady, Reynolds-Averaged Navier-Stokes (RANS) equations coupled with Realizable k-e turbulence model and the species transport equation. The flow development and pollutant dispersion are investigated numerically considering four different upstream building height (HB1) to emitting building height (HB2) ratios (HB1/HB2 = 0.5, 1.0, 2.0 and 3.6) and four different stack locations measured from the upwind edge of the emitting building (Xs) under the approaching wind perpendicular to the building faces. The results obtained reveal that: (1) the flow field characteristics around the buildings, especially the vortex flow above the emitting building roof and the vortex pattern between the upstream and emitting buildings, depend significantly on the upstream building height and much less on the location of the short stack; (2) for an upstream building of lower or equal height with the emitting building, the pollutants from a rooftop stack are immediately transported downwind the stack by the longitudinal flow; (3) when a stack is located inside the wake recirculation zone of the upstream building, the pollutants from the stack are swept by the upwind flow towards the leeward side of the upstream building and the distribution of pollutant concentrations is highly sensitive to both the upstream building height and the stack location. For different upstream building heights, suitable locations for fresh air intakes on the sides of buildings are also proposed based on the pollutant distribution patterns obtained.

Two-dimensional numerical simulations were performed using the FLUENT code to investigate the impacts of the shape and height of building roofs on flow and pollutant dispersion inside an isolated street canyon. The numerical model was validated against wind tunnel measured data. Five different roof shapes (vaulted, trapezoidal, slanted, upward wedge-shaped, and downward wedge-shaped roofs) and three different roof heights ( = 1/6, 1/3, and 1/2, where is the roof height and H is the building height) were considered in the simulations. The numerical results revealed that the vortical flow structure and pollutant distribution within an isolated canyon depend significantly on the shape and height of building roofs. A large unique clockwise vortex is established in the canyon, and thus the pollutants accumulate in the leeward side of the canyon for the vaulted and downward wedge-shaped roofs at = 1/6, 1/3, and 1/2, the trapezoidal roof at = 1/6 and 1/3, and the slanted and upward wedge-shaped roofs at ...

In this study, the pollutant dispersion within street canyons is studied by experiments conducted in an environmental wind tunnel. The vehicular exhaust emissions are modeled using a line source. The pollutant (smoke) concentrations inside the canyons are measured based on a light scattering technique. The pollutant concentrations within the four different street canyons containing the galleries and the three-level flat-roofs under both the isolated and urban environments are obtained and discussed. For each of the four canyon configurations investigated, it is found that there is an obvious discrepancy between the pollutant dispersion patterns under the isolated environment and the urban environment. The three-level flat roof is found to significantly influence the pollutant distribution pattern in a street canyon. In order to clarify the impacts of the wedge-shaped roofs on the pollutant dispersion inside an urban street canyon of an aspect ratio of 1.0, the pollutant distributions inside urban street canyons of three different wedge-shaped roof combinations are measured and analyzed. It is revealed that the pollutant distribution pattern inside the urban street canyon of an aspect ratio of 1.0 is influenced greatly by the wedge-shaped roof, especially, when an upward wedge-shaped roof is placed on the upstream building of the canyon. Images from this study may be utilized for a rough evaluation of the computational fluid dynamics (CFD) models and for helping architects and urban planners to select the canyon configurations with a minimum negative impact on the local air quality.

The influence of roof thermal effects on the dispersion of pollutants discharged from a rooftop stack in the wake of a high-rise building was investigated by means of wind-tunnel experiments. Six Ri cases and two stack emissions (S1 and S2) were considered. The distributions of temperature and pollutants, and visualization of pollutant diffusion were measured experimentally. Results show that as the Ri increases, the dimensionless temperature in the vertical center plane decreases, with its mean value reducing by 57%. According to the CRP value, the influence of Ri on pollutant distributions can be divided into two stages, namely the strongly influenced stage (0 ≤ Ri ​≤ ​0.78) and the weakly influenced stage (0.78 ≤ Ri ​≤ ​1.15). The mean pollutant concentration in the leeward wall and inner street canyon decreases rapidly with the Ri increasing (0 ≤ Ri ​≤ ​0.78), but changes little when Ri ​≥ ​0.78. Under the stack S2 emission, with Ri increasing, the obvious downwash effect gradually weakened, until Ri ​≥ ​0.97 the downwash effect disappeared eventually. Moreover, the visualization of pollutant diffusion further confirmed the above analysis results. This highlights the understanding of the influence of roof thermal effect on the local atmospheric environment.

This comment mainly deals with a mistake of applying pseudo-first-order kinetic model for testing the kinetic behaviors of adsorption.

This comment concern a mistake of applying pseudo-first order kinetic equation for adsorption systems.

A two-dimensional numerical model for simulating airflow and pollutant dispersion inside an urban street canyon was first developed using the FLUENT code, and then it was validated against a wind tunnel experiment. Then the effects of strength and position of pollutant sources on pollutant dispersion within an urban street canyon were investigated numerically. The numerical results showed that the dimensionless pollutant concentrations within the urban street canyon were independent from the source strength. The results also revealed that the pollutant distributions inside the urban street canyon with a two-lane road were influenced significantly by the positions of the two sources: 1) the closer the two sources were to the street center of the canyon, the lower the pollutant concentrations on the leeward wall and at the human respiration level in the leeward footpath became; 2) the pollutant concentrations on the windward wall and at the human respiration level in the windward footpath were not sensitive...

This comments concern a mistake of applying pseudo-first-order kinetic equation for evaluating kinetic parameters of adsorption.

A two-dimensional numerical model for simulating flow and pollutant dispersion in an urban street canyon is firstly developed using the FLUENT code and then validated against the wind tunnel results. After this, the flow field and pollutant dispersion inside an urban street canyon with aspect ratio W/H = 1 are examined numerically considering five different shapes (vaulted, trapezoidal, slanted, upward wedged, and downward wedged roofs) as well as three different roof height to building height ratios (Z H /H = 1/6, 1/3, and 1/2) for the upstream building roof. The results obtained reveal that the shape and height of an upstream roof have significant influences on flow pattern and pollutant distribution in an urban canyon. A large single clockwise vortex is generated in the canyon for the vaulted upstream roof at Z H /H = 1/6, 1/3, and 1/2, the trapezoidal and downward wedged roofs at Z H /H = 1/6 and 1/3, and the slanted and upward wedged roofs at Z H /H = 1/6, while a main clockwise vortex and a secondary counterclockwise vortex are established for the trapezoidal and downward wedged roofs at Z H /H = 1/2 and the slanted and upward wedged roofs at Z H /H = 1/3 and 1/2. In the one-vortex flow regime, the clockwise vortex moves upward and grows in size with increasing upstream roof height for the vaulted, trapezoidal, and downward wedged roofs. In the two-vortex flow regime, the size and rotational velocity of both upper clockwise and lower counterclockwise vortices increase with the upstream roof height for the slanted and upward wedged roofs. At Z H /H = 1/6, the pollution levels in the canyon are close among all the upstream roof shapes studied. At Z H /H = 1/3, the pollution levels in the canyon for the upward wedged roof and slanted roof are much higher than those for the vaulted, trapezoidal, and downward wedged roofs. At Z H /H = 1/2, the lowest pollution level appears in the canyon for the vaulted upstream roof, while the highest pollution level occurs in the canyon for the upward wedged roof.

The dispersion of particles emitted from the surface of a circular cylinder placed in a gas flow at the Reynolds number of 200 000 is numerically investigated using the discrete vortex method coupled with a Lagrangian approach for solid particle tracking. The wake vortex patterns, the temporal-spatial distributions and trajectories as well as the dispersion functions for particles with various Stokes numbers (St) ranging from 0.001 to 1.0 are obtained. The numerical results reveal that: (1) Solid particles on the cylinder surface are picked up and then transported away from the cylinder by the wake vortex flow. (2) Solid particles emitted from the cylinder surface always follow the vortices in the cylinder wake, and the response of particles to wake vortices is directly related to their Stokes numbers (particles with St = 0.001, 0.0038, 0.01 can distribute both in the vortex core and around the vortex periphery, whereas those with St = 0.1, 1.0 can not enter the vortex core and congregate mainly around the vortex periphery). (3) The particles move in rolling state in the wake region, and the dispersion intensity of particles in the lateral direction decreases remarkably as the Stokes number of particles is increased from 0.001 to 1.0.

An error of applying pseudo-second-order kinetic model for determining kinetic parameters of adsorption has been pointed out. Also, this discussion presents a corrected pseudo-second-order kinetic equation.

This comment concerns mistakes of applying pseudo first and second-order equations for evaluating the kinetic parameters of adsorption.

A two-dimensional numerical model for evaluating the wind flow and pollutant dispersion within a street canyon was first developed using the FLUENT code, which was then validated against a wind tunnel experiment. Then, the effects of the upstream building width and upwind building arrangement on the airflow and pollutant dispersion inside an isolated street canyon were investigated numerically. The numerical results revealed that: (1) the in-canyon vortex center shifts downwards as the upstream building width increases; (2) the recirculation zone covers the entire upstream building roof for the cases when W/H = 0.5, 1.0, 1.5, and 2.0 (W is the upstream building width and H is the building height), whereas the flow reattaches the upstream building roof for the cases when W/H = 2.5 and 3.0; (3) when the upstream building width is shorter than the critical width WC (= 2H), an increase in the upstream building width leads to an increase in the pollution level on the leeward wall of the canyon and a decrease i...

Solid curtains can be installed in subway tunnels for the promotion of air ventilation in ventilation ducts in association with the piston effect caused by a running train. With an aim to analyze the effects of solid curtains on duct ventilation performance in a subway tunnel, the current study adopts the tunnel and subway train geometries which are exactly the same as those in a previous model tunnel experiment, but newly incorporates two ventilation ducts connected vertically to the tunnel ceiling and two solid curtains placed at an upstream position of a duct near the tunnel inlet and at a downstream position of another duct near the tunnel outlet, respectively. A three-dimensional CFD model adopting the dynamic layering method for tracking the motion of a train, which was validated against the reported model tunnel experiment in a previous study, is employed to predict the train-induced unsteady airflows in the subway tunnel and in the ducts. The numerical results reveal that the duct ventilation performance in a subway tunnel strongly depends on the operation of the solid curtains. The suction mass flow of the air through the duct near the tunnel inlet and the exhaust mass flow of the air through the duct near the tunnel outlet are increased considerably in the case with the solid curtains in comparison with those in the case without the solid curtains.

A mistake of applying pseudo-first order kinetic model for determining kinetic parameters of adsorption has been pointed out. Also, this discussion gives a corrected pseudo-first order kinetic equation.

According to the problem that the concrete realization process of cloud manufacturing service mode was researched not enough, the process of manufacturing capability semantic modeling and intelligent service matching was studied in cloud manufacturing platform. Firstly, the properties and characteristics of manufacturing resources and demand were analyzed; then intelligent matching algorithm based on ontology semantic similarity was put forwarded, this algorithm comprehensive the advantage of semantic distance, properties, structure and examples four kinds of similarity algorithm, multistage matching, step by step refinements, realized the intelligent matching of supply and demand. Finally, the supply and demand intelligent matching process was build, based on analyzing the manufacturing resource and demand attributes and characteristics.

An unsteady three-dimensional analysis of the ventilation performance is carried out for different ventilation strategies to find out a ventilation method with a high performance in a subway tunnel. The natural ventilation performance associated with a train-induced air flow in a subway tunnel is examined. The dynamic layering method is used to consider the moving boundary of a train in the current CFD method. The geometries of the modeled tunnel and the subway train are partially based on those of the Seoul subway. The effects of the structure of the ventilation duct and the geometry of the partitions on the ventilation performance are evaluated. The results show that the combined ventilation ducts (to be designed), and the partitioning blocks installed along the middle of tunnel (already in existences) are helpful for air exchange. This study can provide some guidance for the design of ventilation ducts in a subway system.

This study has investigated numerically the effects of the ventilation duct number and duct geometry on duct ventilation performance in a subway tunnel. A three-dimensional numerical model using the dynamic layering method for the moving boundary of a train, which was validated against the model tunnel experimental data in a previous study, is adopted to simulate train-induced unsteady tunnel flows. For the tunnel and subway train geometries that are exactly the same as those used in the model tunnel experimental test, but with the ventilation ducts being connected to the tunnel ceiling, the three-dimensional tunnel flows are simulated numerically under five different ventilation duct numbers and two different duct geometries. The numerical results reveal that: (1) for a given total area of openings, the ventilation duct number has little influence on the total mass flow of the air sucked into the tunnel through the ventilation ducts while the total mass flow of the air pushed out of the tunnel through the ducts increases remarkably with the increase in the duct number; (2) with the increase of the distance between a specific ventilation duct and the tunnel inlet the suction mass flow through the duct decreases significantly while the exhaust mass flow through the duct increases greatly, i.e., the location of a specific duct has a strong impact on the total suction and exhaust mass flows through the ventilation duct; (3) as the linkage angle between the tunnel ceiling and the upstream side wall of a duct is changed from 90° to 45°, the size of the re-circulation area inside the duct is much reduced when the train approaches the duct and thus the amount of air pushed out of the duct is greatly increased (i.e. the exhaust effect through the duct is remarkably strengthened).

CFD calculations are carried out using the standard, RNG and realizable κ-ε turbulence models to simulate the airflow and pollutant dispersion inside an isolated street canyon. The computed air velocity vector fields and pollutant concentration contours show that all the three studied κ-ε models produce a very similar clockwise vortex structure that carries the pollutants released from the line source on the street floor towards the leeward side of the canyon. The calculated non-dimensional pollutant concentration distributions on both the leeward and windward walls of the canyon are compared with the wind tunnel measured data. It is revealed that (1) on the windward wall of the canyon, the calculated pollutant concentrations using the standard, RNG and realizable κ-ε models are all in perfect agreement with the experimental observations, (2) the RNG and realizable κ-ε models provide almost the same results for pollutant concentration distributions on the leeward wall of the canyon, (3) the RNG and realizable κ-ε models overestimate greatly the pollutant concentration values on the leeward wall of the canyon, whereas the concentration distributions predicted by the standard κ-ε model on the leeward wall are in reasonable agreement with the wind tunnel data.

This comment concerns a mistake of applying pseudo-second-order kinetic equation for calculating the kinetic parameters of adsorption, a citation error and figure plagiarism.

The objective of this study is to investigate numerically the characteristics of train-induced unsteady airflow in a subway tunnel with natural ventilation ducts. A three-dimensional numerical model using the dynamic layering method for the moving boundary of a train is first developed, and then it is validated against the model tunnel experimental data. With the tunnel and subway train geometries in the numerical model exactly the same as those in the model tunnel experimental test, but with the ventilation ducts being connected to the tunnel ceiling and a barrier placed at the tunnel outlet, the three-dimensional train-induced unsteady tunnel flows are numerically simulated. The computed distributions of the pressure and the air velocity in the tunnel as well as the time series of the mass flow rate at the ventilation ducts reveal the impact of the train motion on the exhaust and suction of the air through ventilation ducts and the effects of a barrier placed at the tunnel outlet on the duct ventilation performance. As the train approaches a ventilation duct, the air is pushed out of the tunnel through the duct. As the train passes the ventilation duct, the exhaust flow in the duct is changed rapidly to the suction flow. After the train passes the duct, the suction mass flow rate at the duct decreases with time since the air pressure at the opening of the duct is gradually recovered with time. A drastic change in the mass flow rate at a ventilation duct while a train passes the corresponding ventilation duct, causes a change in the exhaust mass flow rate at other ventilation ducts. Also, when a barrier is placed at the tunnel outlet, the air volume discharge rate at each ventilation duct is greatly increased, i.e., the barrier placed at the tunnel outlet can improve remarkably the ventilation performance through each duct.

The objective of this study is to investigate numerically the effect of wedge-shaped roofs on wind flow and pollutant dispersion in a street canyon within an urban environment. A two-dimensional computational fluid dynamics (CFD) model for evaluating airflow and pollutant dispersion within an urban street canyon is firstly developed using the FLUENT code, and then validated against the wind tunnel experiment. It was found that the model performance is satisfactory. Having established this, the wind flow and pollutant dispersion in urban street canyons of sixteen different wedge-shaped roof combinations are simulated. The computed velocity fields and concentration contours indicate that the in-canyon vortex dynamics and pollutant distriburtion are strongly dependent on the wedge-shaped roof configurations: (1) the height of a wedge-shaped roof peak is a crucial parameter determining the in-canyon vortex structure when an upward wedge-shaped roof is placed on the upwind building of a canyon; (2) both the heights of upstream and downstream corners of the upwind building have a significant impact on the in-canyon vortical flow when a downward wedge-shaped roof is placed on the upwind building of a canyon, due to flow separation as wind passes through the roof peak; (3) the height of upstream corner of the downwind building is an important factor deciding the in-canyon flow pattern when a wedge-shaped roof is placed on the downwind building of a canyon; (4) the characteristics of pollutant dispersion vary for different wedge-shaped roof configurations, and pollution levels are much higher in the “step-down” canyons relative to the “even” and “step-up” ones.

Based on the CFD technique, fifteen cases were evaluated for the airflows and pollutant dispersions inside urban street canyons formed by slanted roof buildings. The simulated wind fields and concentration contours show that W/H, W/h and h/H (where W is the street width, and H and h are the heights of buildings at the leeward and windward sides of the street, respectively) are the crucial factors in determining the vortex structure and pollutant distribution within a canyon. It is concluded that (1) in a symmetrical canyon, at W/H =0.5 two vortices (an upper clockwise vortex between the slanted roofs and a lower counter-clockwise one) are developed and pollutants accumulate on the windward side of the street, whereas at W/H=2.0 only one clockwise vortex is generated and thus pollution piles up on the leeward side, (2) in a step-up canyon with W/H =0.5 to 2.0 (at h/H =1.5 to 2.0) and a step-down canyon with W/h=1.0 (at h/H =0.5 to 0.667), the pollution level close to the lower building is higher than that close to the taller building since a clockwise vortex is generated in the step-up canyon and a counter-clockwise one in the step-down canyon, (3) in a narrow step-down canyon with W/h=0.5 (at h/H =0.667) very poor ventilation properties is detected, and inside a wider step-down canyon with W/h=2.0 the vortex structure and consequently pollutant distribution varies greatly with h/H.

A numerical investigation on the particle dispersion in the wake of particle-laden gas flows past a circular cylinder at Reynolds number of 10 5 is presented. In the numerical method, the Discrete Vortex Method with the diffusion velocity model is employed to calculate the unsteady gas flow fields and a Lagrangian approach is applied to track individual particles. A dispersion function is defined to represent the dispersion scale of the particle. The distributions of gas velocities and vortex blobs, the trajectories and dispersion functions as well as distributions for particles with various Stokes numbers ranging from 0.01 to 1000 are obtained. The numerical results show that: (1) very small sized particles with St = 0.01 can distribute both in the vortex core and around the vortex periphery, whereas intermediate sized particles with St = 1.0, 10 are distributed around the vortex periphery, and very large sized particles with St = 1000 do not feel the gas flow; (2) only at small Stokes number ( St = 0.01, 0.1) the particles do not impact with the cylinder; (3) the particle's dispersion intensity decreases precipitously as St is increased from 0.01 to 10.

In the recent paper, entitled “Outdoor ventilation performance of various configurations of a layout of two adjacent buildings under isothermal conditions” by Ayo et al. (2015) (Building Simulation, 8: 81–98), an expression is presented for evaluating the temporal average of positive air exchange rate (AER+) in a three-dimensional canyon. This comments show that this expression for the temporal average of AER+ is incorrect. Also, this discussion gives a corrected expression for the temporal average of AER+.

A mistake of applying pseudo second-order kinetic equation for evaluating kinetic parameters of adsorption has been pointed out, as well as a quotation error. Also, this discussion gives a corrected pseudo second-order kinetic equation and makes a suggestion for citing the original paper for the pseudo first-order kinetic equation.