Ventilation Zone Research Articles

Utilising GIS for studying urban entropy, population dynamics, and ventilation disparity: A case study of changing land use, land cover, and socially vulnerable hotspots in Hyderabad, India

Citywide ventilation studies are challenging because they involve complicated interactions between various variables, including anthropogenic variables, housing conditions, and socio-economic considerations. The present paper aims to clarify the complex interactions between these three vital variables and the restricted ventilation zones. The ventilation patterns from 1990 to 2020 are meticulously examined in the first half of this research. This study observed the expansion of built-up areas, which increased from 13.7% in 1990 to 51.8% in 2020. The remainder of the paper explores population dynamics in locations with poor ventilation. In severely ventilated areas, the population increased from 10.7% in 1990 to 16.6% in 2020. The percentage of severely ventilated areas increased from 0.7% in 1990 to 31.6% in 2020, highlighting the urgent need to address ventilation inequities in urban planning. The research uses Spearman correlation analysis, which shows that industrial areas have a substantial positive association with ventilation disparities among anthropogenic factors, indicating the effect of industrial zones on decreased ventilation. The absence of toilets is a powerful and substantial housing variable contributing to poor ventilation. Additionally, the existence of the Total Scheduled Caste population within the socio-economic variables exhibits a strong and significant association, indicating that social issues are intricately linked to ventilation disparities. This research provides critical insights that can inform urban planning and policy decisions to improve ventilation and living conditions in densely populated cities.

Lung Volume and Pneumatization Changes in Children in Early Post-Surgical Period After Correction of Severe Neuromuscular Scoliosis Complicated with Respiratory Failure: Cohort Study

Background. The effect of spinal deformity surgical correction in children with severe neuromuscular scoliosis (NMS) on lung function remains unexplored. Objective. The aim of the study is to — to survey the dynamics of volume and structure of lungs pneumatization in children after surgical correction of severe neuromuscular deformities of the spine complicated by respiratory disorders. Methods. CT scans of lungs from 5 children with right-sided NMS, grade IV (Cobb angle > 50°) and functional respiratory disorders (lung capacity < 30% of normal value according to spirometry data and/or clinical signs of respiratory failure) were retrospectively studied. Right and left lungs volumes, their ratio (asymmetry index), indicators of distribution of tissue density of each lung (as a percentage of total volume) before (not earlier than 2 months) and after (not later than 3 months) surgical correction of scoliosis were determined via the data processing from CT scans of the thoracic spine. Results. All children had both lung volumes below reference values (healthy peers) before surgery. The right lung volume increased by 11% (6.4–40.6%), the left lung — by 41% (22.5–90%) with the asymmetry index approaching the reference values for the corresponding age after correction of spinal deformity (the value of scoliotic deformity decreased (median) from 94 to 68°). The volume of normal ventilation zones increased from 30 to 50% on the right side, and from 41 to 55% on the left side, primarily due to decrease in the volume of hypoventilation zones, but not atelectasis and emphysema. Conclusion. Surgical correction of spinal deformity in children with NMS, grade IV, complicated with respiratory failure led to normalization of lungs volume and tissue density characteristics already in the early postoperative period.

Experimental study of buoyancy-driven ventilation with a single opening between two adjacent building zones

In adjacent building zones connected by a single opening, a thermal plume produces a buoyant layer accumulating in the upper space of the experimental zone. The pressure difference between inside and outside the chamber will lead to air flowing in from outside and buoyant fluid flowing out from inside. This study aims to examine the effect of the vertical opening combination on flow regimes in adjacent building zones. The findings indicate that there may be three different flow regimes depending on the relative positions of the opening in the shared wall and the neutral level. The steady flow in two regimes with double stratification formed in the two zones is modeled separately and the theoretical prediction is compared with the experimental results. The flow regime of natural ventilation in the adjacent zones is only related to the height of the outlet, heat source height and effective opening area of the ventilation zones, but not to the buoyancy flux. The interface changes linearly with the height of the heat source at first until the nozzle is immersed in the buoyancy layer, and then the interface height remains constant. The relative size of the openings will also affect the volume flow rate through them, and keeping the areas of the openings along the flow passage equal will maximize the ventilation rate. These research results can provide layout guidelines for building doors and windows and will help designer improve the natural ventilation effect of adjacent building zones.

Functional Impairment in Small Airways Associated With the Breathlessness Symptoms in Long-Coronavirus Disease.

This study aimed to determine the association between functional impairment in small airways and symptoms of dyspnea in patients with Long-coronavirus disease (COVID), using imaging and computational modeling analysis. Thirty-four patients with Long-COVID underwent thoracic computed tomography and hyperpolarized Xenon-129 magnetic resonance imaging (HP Xe MRI) scans. Twenty-two answered dyspnea-12 questionnaires. We used a computed tomography-based full-scale airway network (FAN) flow model to simulate pulmonary ventilation. The ventilation distribution projected on a coronal plane and the percentage lobar ventilation modeled in the FAN model were compared with the HP Xe MRI data. To assess the ventilation heterogeneity in small airways, we calculated the fractal dimensions of the impaired ventilation regions in the HP Xe MRI and FAN models. The ventilation distribution projected on a coronal plane showed an excellent resemblance between HP Xe MRI scans and FAN models (structure similarity index: 0.87 ± 0.04). In both the image and the model, the existence of large clustered ventilation defects was not identifiable regardless of dyspnea severity. The percentage lobar ventilation of the HP Xe MRI and FAN model showed a strong correlation (ρ = 0.63, P < 0.001). The difference in the fractal dimension of impaired ventilation zones between the low and high dyspnea-12 score groups was significant (HP Xe MRI: 1.97 [1.89 to 2.04] and 2.08 [2.06 to 2.14], P = 0.005; FAN: 2.60 [2.59 to 2.64] and 2.64 [2.63 to 2.65], P = 0.056). This study has identified a potential association of small airway functional impairment with breathlessness in Long-COVID, using fractal analysis of HP Xe MRI scans and FAN models.

Experimental and numerical study of wind tower integrated with solar heating unit to meet thermal comfort in buildings during cold and sunny climate conditions

Natural ventilation techniques are increasingly being adopted in recent times due to the need to cut down on greenhouse gases emission and energy cost. A classic natural ventilation technique, the wind tower, may be utilised to minimize the load on typical HVAC systems. One of the major disadvantage limiting the deployment of wind tower is the additional heating load it demands on the HVAC system during the winter months. The work focusses on improving the year-round capability of a wind tower by attaching a solar heating unit (SHU) that would heat the incoming ambient air through a conjugate heat transfer system before being circulated into the space to be ventilated. For performance validation, the numerical technique was utilised initially, then an experimental setup was created based on the numerical results to validate for practical situations. Using the CFD simulation, ventilation performance of this tower system was evaluated in terms of mean age of air (MAA) and air change effectiveness (ACE). The commercial ANSYS Fluent was used to solve the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) turbulence model. The results showed that SHU has been able to heat up the incoming air of 18 °C by 5 °C–23 °C which is generally considered as a comfortable temperature range. According to the analyses of airflow rate at different incident angles through the four quadrants of tower, the maximum flow rate (0.45 m3/s) of air steam was observed at 45° incident angle. The ACE values in the inhabited space were typically near to 1.0, indicating that the ventilation air mixed up well in the ventilated zone. The wind tower performance was experimentaly investigated in terms of solar radiation variations, wind velocity variations, temperature variation in SHU and inside wind tower, and air change rate (ACR) on the experimental setup. Experimental study shows a variation of 2–4 °C in the indoor temperature and thereby ensuring optimal thermal comfort. The recommended wind speed for an effective mass flow rate is in the range of 3 m/s, and an average ACR of 25 per hour indicates that the air is being ventilated properly.

A new method for air exchange efficiency assessment including natural and mixed mode ventilation

The COVID-19 health crisis highlighted the correlation between air exchange efficiency and virus airborne transmission. Air exchange efficiency is a performance index able to characterize ventilation effectiveness in buildings. Some standards, such as ASHRAE 129, clearly define assessment procedures of air exchange efficiency for mechanical ventilation, adopting tracer gas techniques. However, standardized procedures are based on measurements at the exhaust and cannot be adopted for natural and mixed mode ventilation strategies. In the ‘80s, Sandberg suggested that tracer gas decay technique enables to measure simultaneously the nominal time constant (through air change rate measurements) and the mean age of air in several points of the ventilated zone. This paper aims to present practical issues and uncertainty analysis related to the implementation of this approach, in a new commissioning protocol. For this purpose, we compare the new procedure, based on Sandberg’s observation, with the ASHRAE 129 protocol for mechanical ventilation. Results coming from field campaigns show that the difference between air exchange efficiency values obtained using ASHRAE 129 protocol (51.8%) and the new procedure (47.4%) are usually negligible in low airflow rate, considering an average uncertainty of ± 7.0%. Results show that the procedure is robust and that it is technically possible to implement it to natural and mixed-mode ventilation.

Poleward Shift of the Kuroshio Extension Front and Its Impact on the North Pacific Subtropical Mode Water in the Recent Decades

AbstractThe meridional shift of the Kuroshio Extension (KE) front and changes in the formation of the North Pacific Subtropical Mode Water (STMW) during 1979–2018 are reported. The surface-to-subsurface structure of the KE front averaged over 142°–165°E has shifted poleward at a rate of ~0.23° ± 0.16° decade−1. The shift was caused mainly by the poleward shift of the downstream KE front (153°–165°E, ~0.41° ± 0.29° decade−1) and barely by the upstream KE front (142°–153°E). The long-term shift trend of the KE front showed two distinct behaviors before and after 2002. Before 2002, the surface KE front moved northward with a faster rate than the subsurface. After 2002, the surface KE front showed no obvious trend, but the subsurface KE front continued to move northward. The ventilation zone of the STMW, defined by the area between the 16° and 18°C isotherms or between the 25 and 25.5 kg m−3 isopycnals, contracted and displaced northward with a shoaling of the mixed layer depth hm before 2002 when the KE front moved northward. The STMW subduction rate was reduced by 0.76 Sv (63%; 1 Sv ≡ = 106 m3 s−1) during 1979–2018, most of which occurred before 2002. Of the three components affecting the total subduction rate, the temporal induction (−∂hm/∂t) was dominant accounting for 91% of the rate reduction, while the vertical pumping (−wmb) amounted to 8% and the lateral induction (−umb ⋅ ∇hm) was insignificant. The reduced temporal induction was attributed to both the contracted ventilation zone and the shallowed hm that were incurred by the poleward shift of KE front.

Numerical study of the parameters affecting the formation and growth of ventilation in a surface-piercing propeller

The surface-piercing propellers (SPPs) are a specific type of supercavitating propellers that have higher efficiencies at high advance speeds. The SPPs operate on a free surface, so due to the ventilation and air suction into the water, the pressure of the suction surface of the blade approaches atmospheric pressure. Given the importance of better understanding this phenomenon, in this research, the formation and development of ventilation in an SPP5.74 5-blade SPP is numerically investigated by defining proper geometrical and physical parameters. The finite volume method (FVM) has been implemented to numerical modeling and simulating the free surface carried out by the volume of fluid (VOF) two-phase model. The numerical results have compared with the experimental data with similar conditions due to validating the simulation. Also, the simulations were carried out in six different advance coefficients ranges from 0.44 to 0.94. In the results section, different parameters are introduced, including the length and thickness of the ventilation zone, the influence of the advance coefficient on the physics of the ventilation phenomenon have been evaluated in various propeller radius ratios. The results show that in the suction surface and the points where ventilation starts, the pressure tends to the atmospheric pressure, by reducing the advance coefficient, the thickness, and the length of the ventilation zone increase, in this condition, the ventilation zone moves towards the leading edge. In constant advance coefficients, increasing the radius ratio reduces the thickness and the length of the ventilation zone. In high radius ratios and near the tip of the blade, the ventilation is limited to the trailing edge. Moreover, the analysis of the pressure coefficients shows that in the ventilation zone, the pressure coefficient is zero, while in the other areas, it ranges from 0 to 1. With larger advance coefficients, the areas with the zero pressure coefficient tend towards the trailing edge.

Local Climate Zone Classification Scheme Can Also Indicate Local-Scale Urban Ventilation Performance: An Evidence-Based Study

Studies on urban ventilation indicate that urban ventilation performance is highly dependent on urban morphology. Some studies have linked local-scale urban ventilation performance with the local climate zone (LCZ) that is proposed for surface temperature studies. However, there is a lack of evidence-based studies showing LCZ ventilation performance and affirming the reliability of using the LCZ classification scheme to demonstrate local-scale urban ventilation performance. Therefore, this study aims to analyse LCZ ventilation performances in order to understand the suitability of using the LCZ classification scheme to indicate local-scale urban ventilation performance. This study was conducted in Shenyang, China, with wind information at 16 weather stations in 2018. The results indicate that the Shenyang weather station had an annual mean wind speed of 2.07 m/s, while the mean wind speed of the overall 16 stations was much lower, only 1.44 m/s in value. The mean wind speed at Shenyang weather station and the 16 stations varied with seasons, day and night and precipitation conditions. The spring diurnal mean wind was strong with the speeds of 3.56 m/s and 2.21 m/s at Shenyang weather station and the 16 stations, respectively. The wind speed (2.21 m/s at Shenyang weather station) under precipitation conditions was higher than that (1.75 m/s at Shenyang weather station) under no precipitation conditions. Downtown ventilation performance was weaker than the approaching wind background, where the relative mean wind speed in the downtown area was only 0.53, much less than 1.0. The downtown ventilation performance also varied with seasons, day and night and precipitation conditions, where spring diurnal downtown ventilation performance was the weakest and the winter nocturnal downtown ventilation performance was the strongest. Moreover, the annual mean wind speed of the 16 zones decreased from the sparse, open low-rise zones to the compact midrise zones, indicating the suitability of using LCZ classification scheme to indicate local-scale urban ventilation performance. The high spatial correlation coefficients under different seasons, day and night and precipitation conditions, ranging between 0.68 and 0.99, further affirmed that LCZ classification scheme is also suitable to indicate local-scale urban ventilation performance, despite without the consideration of street structure like precinct ventilation zone scheme.

Relationships among local-scale urban morphology, urban ventilation, urban heat island and outdoor thermal comfort under sea breeze influence

Many cities are facing the problem of urban heat island (UHI) and UHI mitigation is becoming crucial in urban planning and design. The reasonable wind-sensitive design may be a feasible approach to UHI mitigation and outdoor thermal comfort improvement, as cool wind (i.e. sea breeze) is a good cooling intervention. Consistent with the precinct ventilation zone scheme, this study experimentally investigated relationships among urban morphology, precinct ventilation performance, UHIs and outdoor thermal comfort in a compact high-rise gridiron precinct in the coastal Sydney, Australia.Results indicate that precinct morphological characteristics had a strong modification effect on precinct ventilation. As a result, under different combination of external meteorological conditions and precinct morphological characteristics, there was no significant difference in precinct ventilation performance (i.e. relative wind velocity ratio). The precinct ventilation performance forced by sea breeze could significantly mitigate UHIs. Meanwhile, the precinct ventilation performance forced by the sea breeze could significantly improve relative humidity which could further significantly improve outdoor thermal comfort. The street orientation was no longer a critical factor affecting precinct ventilation performance, UHIs and outdoor thermal comfort at the precinct scale.Overall, this study preliminarily revealed precinct ventilation performance and its influence on UHIs and outdoor thermal comfort. The cooling and humidifying effects of wind background cannot be ignored in microclimate studies and should be considered for microclimate regulation in urban planning and design.

Dose to Highly Functional Ventilation Zones Improves Prediction of Radiation Pneumonitis for Proton and Photon Lung Cancer Radiation Therapy

We hypothesized that the radiation dose in high-ventilation portions of the lung better predicts radiation pneumonitis (RP) outcome for patients treated with proton radiation therapy (PR) and photon radiation therapy (PH). Seventy-four patients (38 protons, 36 photons) with locally advanced non-small cell lung cancer treated with concurrent chemoradiation therapy were identified, of whom 24 exhibited RP (graded using Common Terminology Criteria for Adverse Events v4.0) after PR or PH, and 50 were negative controls. The inhale and exhale simulation computed tomography scans were deformed using Advanced Normalization Tools. The 3-dimensional lung ventilation maps were derived from the deformation matrix and partitioned into low- and high-ventilation zones for dosimetric analysis. Receiver operating curve analysis was used to study the power of relationship between RP and ventilation zones to determine an optimal ventilation cutoff. Univariate logistic regression was used to correlate dose in high- and low-ventilation zones with risk of RP. A nonparametric random forest process was used for multivariate importance assessment. The optimal high-ventilation zone definition was determined to be the higher 45% to 60% of the ventilation values. The parameter vV20Gy_high (high ventilation volume receiving ≥20 Gy) was found to be a significant indicator for RP (PH: P = .002, PR:P = .035) with improved areas under the curve compared with the traditional V20Gy for both photon and proton cohorts. The relationship of RP with dose to the low-ventilation zone of the lung was insignificant (PH: P = .123, PR: P = .661). Similar trends were observed for ventilation mean lung dose and ventilation V5Gy. Multivariate importance assessment determined that vV20Gy_high, vV5_high, and mean lung dose were the most significant parameters for the proton cohort with a combined area under the curve of 0.78. Dose to the high-ventilated regions of the lung can improve predictions of RP for both PH and PR.

Numerical Studies of the Aerodynamic Features of Dead-end Entries with Side Junction

Investigations of aerodynamic processes occurring in dead-end short entriesaired by turbulent diffusion have been performed. The numerical simulation of the processes of air movement through the entry, flow stalling at the junction with the dead-end entry (for side junction), and the formation of vortices at the dead end have been carried out. The study has been done for a wide range of air flows submitted for computation of air consumption and for various geometric parameters of the dead-end entry. The sizes of the vortex structures and the flow rates in the dead endshave been determined. Based on the results of processing the simulation data, we obtained graphs of the dependences between the length of the ventilated zone of the dead end and its height and width.

Wind-sensitive urban planning and design: Precinct ventilation performance and its potential for local warming mitigation in an open midrise gridiron precinct

Urban heat island (UHI) phenomenon is a severe issue faced by many cities and the reduction of urban ventilation is one of the significant causes. Reasonable urban planning and design can allow cooler wind penetration and thereby UHI mitigation. Upon the local climate zone, the precinct ventilation zone is developed at the local scale with the consideration of wind influence during planning and design. Nevertheless, the precinct ventilation performance (PVP) and its potential influence on precinct outdoor thermal environment (POTE) and precinct outdoor thermal comfort (POTC) have not been well understood. As a result, this study aims to examine PVP and its associated influence on POTE and POTC. This is achieved by a case study within an open midrise gridiron (OMG) precinct in Sydney, Australia during summertime. Result indicates the combinations of the OMG precinct with different external meteorological conditions (EMC) resulted in significant variations in PVP, POTE and POTC. Street orientation in the OMG precinct was not a determinant of PVP, POTE and POTC variations. Compared with the inland wind, sea breeze resulted in weaker UHII within the OMG precinct and more areas underwent cool island effects. Nevertheless, wind could not fully explain the variation of POTE and POTC, while it still had cooling potentials under specific conditions. When the sea breeze prevailed, wind exhibited its cooling potential under the combination of negative UHII and shading as well as that of positive UHII and solar exposure. Forced by the inland wind, precinct ventilation could still have cooling potential under positive UHII and solar exposure combination. Moreover, for cities like Sydney with not high air moisture, moisture increase could result in UHI mitigation and POTC improvement, which was also a way of sea breeze cooling under certain conditions. Afterwards, some implications for local warming mitigation through precinct planning and design have been presented. Overall, this study provides the understandings of the PVP and its associated influence on POTE and POTC within the OMG precinct, and can practically inform urban planners and designers with the wind-sensitive urban planning and design for local warming mitigation.

Recent Decadal Change in the North Atlantic Subtropical Underwater Associated With the Poleward Expansion of the Surface Salinity Maximum

AbstractYu et al. (2017, https://doi.org/10.1002/2017GL075772) reported that the annual mean sea surface salinity maximum (SSS‐max) in the North Atlantic expanded northward by 0.35 ± 0.11° per decade over the 34‐year data record (1979–2012). The expansion shifted and expanded the ventilation zone northward and increased the production of the Subtropical Underwater (STUW). As a result, the STUW became deeper, thicker, and saltier. In this study, the seasonal characteristics of the poleward expansion of the North Atlantic SSS‐max and their effects on the STUW are examined. The results show that the SSS‐max expansion occurred primarily during boreal spring (April, May, and June) and expanded northward by 0.43 ± 0.21° per decade over the 34‐year period. The annual volume of the STUW increased by 0.21 ± 0.09 1014 m3 per decade over the same period, and the spring (April, May, and June) volume increased by 0.31 ± 0.02 1014 m3 per decade (a relative increase of 48 ± 1%). The characteristics of the decadal changes in STUW were attributable to the increased subduction rate associated with the northward expansion of the SSS‐max. The annual subduction rate increased by 0.29 ± 0.07 Sv per decade over the 34 years, and the greatest increase of 1.73 ± 0.61 Sv per decade occurred in April. The change in subduction associated with the expansion of the SSS‐max appeared to be consistent with the Atlantic Multidecadal Oscillation.

Numerical investigation of the immersion ratio effects on ventilation phenomenon and also the performance of a surface piercing propeller

Surface Piercing Propellers (SPP) show high efficiency at high advance speeds. Regarding operational conditions, this kind of propellers generate an air layer when entering the water due to the rotation of the propeller; this phenomenon is called ventilation. The ventilation phenomenon divided into some mechanism with respect to air cavity length on the propeller surface; among them are partially ventilation mechanism and fully ventilation mechanism which has great importance. In this study, using numerical simulation, we have investigated ventilation patterns and also the performance of a five-blade SPP propeller (SPP 5.74) at immersion ratio of 33, 40, 50and 70% respectively. We used Sliding Mesh Technique for modeling. Also, we applied the volume of fluid method to simulate the open surface pattern. To validate numerical results, the four-blade propeller, 841-B was simulated, and then the results of thrust and torque coefficients compared with Olofsson experimental results and validated accordingly. The findings indicate that the maximum value for thrust and torque coefficient would occur at immersion ratio of 70% and the maximum propeller efficiency occurs at immersion ratio of 33% and advance coefficient of 1.1; Moreover, the critical advance coefficient (at the partially and the fully ventilation boundary) increases by a reduction in immersion ratio, so that critical advance coefficients are 0.6 and 0.76, respectively at immersion ratios of 70 and 33%. Meanwhile, as advance coefficient increases, length of ventilation zone will decrease, and consequently the propeller will be laid on partial ventilation zone.

Do building energy codes adequately reward buildings that adapt to partial occupancy?

Most building energy codes’ performance path implicitly reward buildings that perform well under steady and near-capacity occupancy conditions, even though these are not typical operating conditions. Partially, as a result, our buildings tend not to be designed with features that allow optimal energy performance in the common circumstance of partial and fluctuating occupancy. The objective of this paper is to examine current building energy codes in this regard. The paper uses a simulation-based approach to demonstrate two strategies that target occupancy-adaptability: demand-controlled ventilation and smaller-than-required lighting control zones with occupancy-controlled lighting. In this paper, a code-compliant EnergyPlus archetype office building in Toronto, Canada was used to evaluate these design features under different occupancy conditions. The results confirm that both demand-controlled ventilation and smaller lighting control zones are most advantageous at lower occupancy levels. Accordingly, the paper concludes with generalized recommendations for code modifications to properly credit buildings with greater adaptability to partial occupancy.

On advective model of the ventilated thermocline

A model of an advective thermocline is proposed for the case of continuously stratified Sverdrup circulation with a ventilated layer caused by the divergence of flows in the Ekman layer: an immiscible layer with homogenized vorticity and a layer of abyssal liquid, which applies to anticyclonic gyre waters. The results of calculations for the Atlantic Ocean (region 15-52°N, 00-63°E) made with this model are presented. With an abyssal density of 28.0, the values of the surface density and density of the unventilated layer grow to the north from 24.2 to 27.0 and from 27.8 to 27.9, respectively, with an almost zonal distribution, i.e. ventilation zones have latitudinal circles. From calculations of the depths of wind circulation, it follows that the ventilating layer is as deep as 900 m in the north-western region and raises to 250 m in the southern and eastern parts of the basin. The same tendency is traced for the depth of the gyre, but here there is an increase in depth from 500 to 1500 m. The active dynamics in the ventilating layer and the shadow area on the eastern border are noted. The structure of the thermocline is demonstrated with a typical zonal section, characterizing a much larger isopycnic increment for ventilated layers than in non-ventilated layers.

PIV measurement and CFD simulations of an air terminal device with a dynamically adapting geometry

Air quality is an important factor for human well-being, and it is crucial that when using mechanical ventilation system, air is properly distributed so it reaches every user of a ventilated zone. To improve ventilation systems, and in consequence the air quality, this paper focuses on studying the impact of an air terminal device (ATD) with a dynamically changing geometry on the effectiveness of a variable air volume (VAV) ventilation system. VAV system characterizes a change in the airflow magnitude through the system when the heat gains lower, which may be a risk for human health as air may not reach the furthest parts of a zone. To combat this threat, an ATD with a dynamically changing geometry was installed. As a ventilation quality indicator, the air throw was taken under consideration. Thanks to the new ATD, the steady air throw should be maintained despite the changes in flow in the ventilation system. To achieve this, the research was divided into two stages. The first stage included a series of computational fluid dynamics simulations that considered the alteration of the airflow and the air terminal device diameter. Afterwards, verifying laboratory measurements were conducted on a laboratory stand using a particle image velocimetry (PIV) system that included an air terminal device with a changing geometry. The results of the simulations and the PIV measurements showed that the changes in the geometry of the air terminal device improve the ventilation effectiveness of a VAV system, allowing the system to maintain a constant air throw despite the changing airflow magnitude through the system.

Enhancing urban ventilation performance through the development of precinct ventilation zones: A case study based on the Greater Sydney, Australia

Along with ongoing urban development, cities are experiencing significantly different climates compared with surrounding rural or suburban areas. Among various causes, the traditional modification towards urban surface structures has been evidenced as an explanation for the variations of urban climate. This affirms the significances of urban morphology in urban climate study and management. However, urban morphology that focuses on the homogeneity of urban form is always very intricated, so that it is essential to clearly describe and differentiate the interactions between urban morphology and climatic conditions. Focusing on guiding ventilation performance-based planning, therefore, this paper aims at characterizing urban surface structures for the systematic studies of local ventilation performance. In specific, based on the pluridisciplinary method, this paper developed the protocol for the precinct ventilation characterization. The precinct ventilation zone system was derived according to ‘compactness + building height + street structure’, based on which 20 distinctive types of precinct ventilation zones in the Greater Sydney, Australia were presented. The classification system in this paper can provide wind-related researchers, engineers, designers and planners with intuitive understandings of the ventilation performance, thereby further assisting decision makers to formulate sound planning regulations with the inclusion of urban ventilation.

Influence of chosen technical constraints on stability of 3D geological model-based schedule in a complex longwall operation

In Polish underground mining digital 3D geological models and mine structure models are becoming popular as an aid in creating design and schedules of mine workings. Article highlights development made in generating and optimizing mining operations. Having created a model it is possible to test schedule scenarios using a number of constraints. One of the constraint limiting coalmines is ventilation, which may be magnified by high content of methane in coal deposits. In this article two methods of introducing ventilation constraints have been presented. One limits number of longwall shearers working simultaneously in excavations ventilated by the shaft. The other limits tonnage of coal which can be extracted in each ventilation zone. Scenarios governed by the second method turned out to result in more stable exploitation than a base scenario. More precise calculations are possible if a model contains an accurate prognosis of methane emissions that would be caused by extraction of the coal deposit. The aim of the paper is to present possibilities of analysing and upgrading mining operations with the help of digital solutions.