Conducting Computational Fluid Dynamics Research Articles

Analyzing the performance of hull and water jet propeller under mooring conditions: effects of shallow water depths and varying inflow speeds

PurposeWater jet propulsion is widely used in various military and civilian fields due to its advantages of simple structure and high propulsion efficiency. The process of mooring involves utilizing specially designed equipment to secure a ship at a designated berth. During the process of water jet propulsion, the single propeller operates within a complex and turbulent three-dimensional flow. Hence, studying the coupling between the water jet propeller and the hull is critical to comprehending the characteristics of the device and the distribution of the flow field in detail.Design/methodology/approachFirstly, we conducted computational fluid dynamics (CFD)-based self-propulsion calculations to evaluate the interaction between the hull and the propeller. We subsequently analyzed the propeller's performance and the forces acting on the hull to understand how the presence or absence of the hull influenced the water jet propeller. Finally, we performed calculations and analysis of the cavitation characteristics of the coupling between the hull and the water jet propeller, considering different rotational speeds and water depths at the bottom of the pool.FindingsThe study demonstrated that the presence of the hull boundary layer under the hull-propeller coupling condition led to reduced uniformity of propeller inlet flow and lower efficiency of the propulsion pump. However, it also increased the bias toward low-flow conditions. Additionally, increasing the impeller speed led to a gradual increase in the cavitation volume within the water jet propeller, resulting in a gradual decrease in the propeller's performance.Originality/valueThis research provides the technical support required for effective design and operation of water jet propulsion systems. This paper involves studying and analyzing the performance and flow field of the coupling between the hull and propeller under mooring conditions with a specified hull model.

Numerical simulation of flow and heat transfer of n-decane in composite tube under supercritical pressure

As scramjet propulsion systems face big challenges in thermal protection performance, regenerative cooling techniques have been proposed to improve heat transfer behavior. This study introduced a novel design of composite cooling channel with bends and conducted computational fluid dynamics (CFD) simulations to analyze the flow characteristics, heat transfer behavior, and pyrolysis of hydrocarbon fuel within the tube. Results show that the presence of bends significantly enhances heat transfer, leading to an increased temperature and conversion. The composite tube with 15 bends demonstrated a 19.9% increase in conversion rate compared to the straight tube. Hence, proper structure design can improve the regenerative cooling performance which may promote the development of scramjet propulsion systems.

Computational design of a smoke detector with high sensitivity considering three-dimensional flow characteristics

Early fire detection is essential for preventing catastrophic events, and fire detectors play a critical role in ensuring fire safety. Among the various types of fire detectors, photoelectric smoke detectors are widely used because of their ability to detect smoke at an early stage. The present study investigates the effects of changes in flow directions and inlet size on the smoke detection ability of a photoelectric smoke detector by conducting computational fluid dynamics (CFD) simulations. The results indicated that when the flow direction changes, the components in the optical chamber may hinder the smoke inflow and increase the detector activation time. Moreover, the smoke inlet size was found to affect the carbon monoxide concentration inside the chamber. The velocity magnitude distributions confirmed the correlation between the smoke velocity in the labyrinth structures entering the optical chamber and the detection ability of the smoke detector. These findings suggested that when optimizing the performance of a smoke detector, flow direction, inlet size, and amount of smoke introduced into the optical chamber should be considered. The current study suggested the modified design of the smoke detector to have superior detection ability in both directions compared to the base case in terms of activation time.

Modeling Finned Thermal Collector Construction Nanofluid-based Al2O3 to Enhance Photovoltaic Performance

Extensive research has been conducted to address the issue of the reduced efficiency of solar photovoltaic (PV) cells at high temperatures. To address this problem, a hybrid cooling system has been developed. This system uses a thermal collector to convert waste heat into reusable heat. Selecting the best configuration and operational parameters for the collector is crucial for maximizing system performance. To achieve this, we conducted computational fluid dynamics (CFD) modeling using ANSYS. Various factors affecting the cooling of PV solar cells were analyzed, including the collector design, mass flow rate, and concentration of the Al2O3 nanofluids. Results showed that the 12S finned thermal collector system exhibits the lowest temperature for PV solar cells, at approximately 29.654 oC. The electrical efficiency of PV solar cells is influenced by the concentration of Al2O3 nanofluids. We found that the 12S finned collector system with 1% water/Al2O3 nanofluid achieved the highest efficiency (approximately 11.749%) at a flow rate of 0.09 kg/s. The addition of finned collectors affects efficiency and variations in fluid mass flow rates, and there is no relation between the connector type and different Al2O3nanofluid concentrations. In other words, the cooling system can be optimized to enhance the efficiency of the PV solar cells under high-temperature conditions. Doi: 10.28991/CEJ-2023-09-12-03 Full Text: PDF

Optimum design parameters for a venturi-shaped roof to maximize the performance of building-integrated wind turbines

Venturi-shaped roofs provide advantageous wind conditions for efficiently operating building-integrated wind turbines without losing usable floor area. Despite these advantages, venturi-shaped roofs have been sparsely adopted for buildings due to the lack of understanding of their optimum designs to maximize the performance of building-integrated wind turbines. For the first time in literature, this study investigated four design parameters: support structure, corner modification, tunnel shape, and wind turbine arrangement to estimate the optimum venturi-shaped roof design by conducting Computational Fluid Dynamics (CFD) simulations. The results revealed the advantages of shorter support structures with convex and concave shapes at upwind and downwind ends, creating high wind speeds with low turbulence intensities. Corner modifications to the tunnel's entrance and exit are vital to suppress flow separation at the tunnel's entrance and uniform distributions of wind speed and pressure. This study recommends aerodynamic tunnel shapes that follow a non-uniform rational B-spline (NURBS) to accelerate wind without increasing turbulence intensities. The optimum design parameters performed better in normal and oblique wind directions, confirming their universal applicability. This study proposes integrating all optimum design parameters into a venturi-shaped roof design to alleviate the adverse effects of support structures, which are essential for a stable roof design.

Effective diffusional limitation modeling of a heterogeneous reaction system for computational fluid dynamics application

Diffusional limitation of heterogeneous reaction catalysts is typically fitted or over-generalized without considering the catalyst’s physical parameters upon conducting computational fluid dynamics (CFD) analysis of an industrial-scale chemical reactor. Fitting and over-generalization are done to meet computational cost constraints. However, this reduces the reliability of local thermodynamic state analysis and application of calculated results. This study proposes an effective catalytic diffusion-limited model for reliable and cost-effective three-dimensional CFD simulations to overcome such difficulties. The proposed model utilizes simplified equations to compute the diffusional limitation by incorporating the physical parameters of the catalyst. The model is validated using Ni-based cylindrical catalyst pellets for steam–methane reforming and ammonia decomposition reactions, with in-house experiments supporting the fidelity of the model. For practical implementation, the model is applied to three-dimensional CFD simulations of a commercial-scale solid oxide fuel cell (SOFC) hotbox housing a large-scale reformer. Furthermore, a parametric study for inlet gas temperatures and catalyst size is carried out, which provides useful insights into how operating conditions and catalysts affect the transport phenomena and local thermodynamic state of the SOFC hotbox. Consequently, the practicality and versatility of the presented model are established through experiments and simulations.

A numerical study on urban-like block arrays’ drag force and its correlation with ventilation efficiency

This work conducted Computational Fluid Dynamics (CFD) simulations to investigate the drag force (F) and its relation to ventilation of four groups of urban-like block arrays with planar area index (λP ) ranging from 0.0625 to 0.56. Simulations were performed employing the standard k-ε turbulence model after conducting a grid sensitivity test and validating the computational settings against wind tunnel data. The results showed that cases with larger λp , slab-shaped buildings, and staggered layout have higher values of F. As for the subcases within each group, F shows a significant increase for 0.0625 < λp < 0.25, and then only a slight increase for 0.25 < λp < 0.56; while the drag coefficient (Cd ) shows a linear increase along with λp . The further linear regression analysis showed that the spatially averaged velocity and air change rate are strongly negatively correlated with F, which supports the effectiveness of F in reflecting ventilation efficiency, particularly for evaluating urban block-scale ventilation.

Impact of architectural design strategies on the indoor natural ventilation of public residential buildings in Singapore

The architectural design pattern of the public residential buildings developed by Housing and Development Board (HDB) of Singapore has evolved gradually throughout the past decades. However, the fact is that although the new generations of HDB blocks built in recent years are designed to be modernized, the usage of air-conditioning has been increasing in comparison with the old generations. This study aims to investigate the ventilation performance of HDB blocks built in different generations from a historical view. By conducting computational fluid dynamics (CFD) simulations on five typical blocks built in different generations, the area-weighted wind velocities in various rooms of the target units were obtained. The effects of design factors on wind velocity ratio (VR) in corresponding spaces were analyzed and compared. The results show that the old generations with parallel plan layouts generally facilitate cross-ventilation while the new generations with centralized plan layouts usually generate single-sided ventilation which is more sensitive to incoming wind direction. Meanwhile, the window-to-wall ratio and shading depth of the studied facades were validated to have positive and negative relations to the VRs respectively. Though the correlations are insignificant, they show significant disparities between the scenarios under different incoming winds.

Characterization of small abdominal aortic aneurysms' growth status using spatial pattern analysis of aneurismal hemodynamics

Aneurysm hemodynamics is known for its crucial role in the natural history of abdominal aortic aneurysms (AAA). However, there is a lack of well-developed quantitative assessments for disturbed aneurysmal flow. Therefore, we aimed to develop innovative metrics for quantifying disturbed aneurysm hemodynamics and evaluate their effectiveness in predicting the growth status of AAAs, specifically distinguishing between fast-growing and slowly-growing aneurysms. The growth status of aneurysms was classified as fast (≥ 5 mm/year) or slow (< 5 mm/year) based on serial imaging over time. We conducted computational fluid dynamics (CFD) simulations on 70 patients with computed tomography (CT) angiography findings. By converting hemodynamics data (wall shear stress and velocity) located on unstructured meshes into image-like data, we enabled spatial pattern analysis using Radiomics methods, referred to as "Hemodynamics-informatics" (i.e., using informatics techniques to analyze hemodynamic data). Our best model achieved an AUROC of 0.93 and an accuracy of 87.83%, correctly identifying 82.00% of fast-growing and 90.75% of slowly-growing AAAs. Compared with six classification methods, the models incorporating hemodynamics-informatics exhibited an average improvement of 8.40% in AUROC and 7.95% in total accuracy. These preliminary results indicate that hemodynamics-informatics correlates with AAAs' growth status and aids in assessing their progression.

Metrological relations between the spray atomization parameters of a cutting fluid and formation of a surface topography and cutting force

Aerosol formation parameters are very important, as they are responsible for the ability of spray-forming droplets to penetrate the area to which they are applied. Research into modifying these parameters can therefore provide a solution for increasing the effectiveness of cooling and lubrication of the cutting zone during machining. This is particularly important for hard-to-cut materials such as titanium alloys, the machining of which requires the selection of effective cooling/lubricating methods to reduce tool wear or improve the machined surface quality. Previous research indicates that any modification in the air or oil flow rates – which form aerosols during cutting in minimized quantity lubrication (MQL) technique – contribute to an increase or decrease in the penetration of droplets into the cutting zone. It can consequently has a significant impact on machining results. This paper presents results on the effect of volumetric air flow rate P and cutting fluid mass flow rate E during the MQL cutting method on the machined surface topography after turning of Ti6Al4V alloy and the values of the cutting force. On the basis of conducted computational fluid dynamics (CFD) simulation studies, it was shown that the droplet size is more influenced by the change in volumetric air flow rate than cutting fluid mass flow rate and also that as the value of P increases, the droplet diameters decrease and the spray angle increases, which promotes the penetration of the cutting zone. As a result of the analysis of selected 3D surface roughness parameters, as well as contour maps, isometric views and material ratio curves, it was shown that the most favorable machined surface topography is being formed during MQL turning method with a volumetric air flow rate above 20 l/min. Whereby, with conditions of P = 30 l/min and E = 1.182 g/min, the machined surface topography is characterized by a uniform distribution of irregularity peaks and valleys, compared to the MQL turning with other tested values of aerosol formation parameters.

A workflow for viewing biomedical computational fluid dynamics results and corresponding data within virtual and augmented reality environments.

Researchers conducting computational fluid dynamics (CFD) modeling can spend weeks obtaining imaging data, determining boundary conditions, running simulations and post-processing files. However, results are typically viewed on a 2D display and often at one point in time thus reducing the dynamic and inherently three-dimensional data to a static image. Results from different pathologic states or cases are rarely compared in real-time, and supplementary data are seldom included. Therefore, only a fraction of CFD results are typically studied in detail, and associations between mechanical stimuli and biological response may be overlooked. Virtual and augmented reality facilitate stereoscopic viewing that may foster extraction of more information from CFD results by taking advantage of improved depth cues, as well as custom content development and interactivity, all within an immersive approach. Our objective was to develop a straightforward, semi-automated workflow for enhanced viewing of CFD results and associated data in an immersive virtual environment (IVE). The workflow supports common CFD software and has been successfully completed by novice users in about an hour, demonstrating its ease of use. Moreover, its utility is demonstrated across clinical research areas and IVE platforms spanning a range of cost and development considerations. We are optimistic that this advancement, which decreases and simplifies the steps to facilitate more widespread use of immersive CFD viewing, will foster more efficient collaboration between engineers and clinicians. Initial clinical feedback is presented, and instructional videos, manuals, templates and sample data are provided online to facilitate adoption by the community.

Verification of the analytical design model of a subcritical air ejector and assessment of the behavior of the manufactured machine under different operating conditions

ABSTRACT Ejectors are dynamic energy machines that can be designed using analytical methodologies that have been in use for decades. These calculation methods consist of coefficients and equations, which are now untraceable and have not been updated since they were first proposed. Modern literature is devoid of ejector design; therefore, to conduct research on ejectors, it is first necessary to verify the validity of existing computational methods. In this study, we conducted computational fluid dynamics (CFD)-assisted experiments to simulate a subcritical air-to-air ejector with the possibility of controlling the distance of the nozzle mouth from the mixing chamber inlet. It was found that the optimum distance of the nozzle mouth from the mixing chamber inlet (i.e. 7.9 mm) corresponds to the design condition when the ejection coefficient is 1.673 and the secondary medium quantities reach the maximum value of 31.19 kg/h. A change in the position of the nozzle outside the optimum point leads to a deviation in the ejection coefficient and flow rate. The experimental results were compared with those from CFD analysis and the deviation between them did not exceed 2%. Two turbulent flow models, namely k–Ω BSL and k–ε standard, were used for the comparison.

Crop-localised CO2 enrichment improves the microclimate, photosynthetic distribution and energy utilisation efficiency in a greenhouse

In greenhouse cultivation, microclimate control is a highly energy-consuming process, and CO2 enrichment, which is a part of it, requires the direct consumption of fossil fuel energy. To achieve sustainable and economical greenhouse management, we must understand the performance and energy utilisation efficiency of CO2 enrichment in greenhouses. In this study, we conducted computational fluid dynamics (CFD) simulations for two CO2 enrichment methods in a strawberry greenhouse: (1) conventional overall greenhouse enrichment (‘Entire Enrichment’) and (2) crop-localised enrichment (‘Local Enrichment’). The spatial distribution of microclimate parameters was simulated using a CFD model; based on the results, the spatial distribution of the crop photosynthetic rate was also simulated using an environment–plant coupled model group. Furthermore, we quantitatively analysed the efficiency of CO2 enrichment (ECE) by calculating the changes in the photosynthetic carbon assimilation capacity of the crop canopy in relation to CO2 usage, which allowed us to propose a more efficient enrichment strategy. Compared with the Entire Enrichment method, the Local Enrichment method reduced the effects on greenhouse temperature and humidity but increased the average CO2 concentration inside the canopy by 264 μmol mol−1. As a result, Local Enrichment increased the average leaf photosynthetic rate inside the canopy by 1.48 μmol m−2 s−1. According to ECE analysis, Local Enrichment has huge advantages over Entire Enrichment; the mean ECE of Local Enrichment was approximately 4.4 times higher than that of Entire Enrichment (25.7 and 5.9 mmol mol−1, respectively). Moreover, scenario analysis indicated that the Local Enrichment system could be applied to larger greenhouses and improves ECE relative to that in a conventional system. Having compared the two enrichment methods comprehensively, we conclude that the Local Enrichment method could significantly improve the environmental parameters around the crop canopy in relation to photosynthesis and greatly enhance CO2 utilisation efficiency.

Impact of shaft design to thermal comfort and indoor air quality of floors using BIM technology

When studying Indoor Air Quality (IAQ) in commercial buildings by conducting Computational fluid dynamics (CFD) simulations, the solution domain usually includes studied rooms or floor volumes only. The air shafts connected to the studied room and floor were rarely considered. Previous studies, which focused on analysis and simulation of air movement inside ventilation and exhaust shafts, seldom considered how the corresponding air movement affects the connected floors. Field measurement cannot be conducted in inaccessible tenant areas to support CFD simulations. The current practice to calculate solar heat load and distribution for CFD simulation with surrounding buildings included is computationally expensive. The objective of this study is to develop a methodology to investigate how velocity variations along the fresh air shafts affect thermal comfort and IAQ of multiple floors under limited obtainable field measurements. Steady-state CFD simulations were conducted on fresh air shafts and office floors of a typical commercial building. Building Information Modeling (BIM) technology was applied to create models to represent the geometry of fresh air shafts and office floors accurately. In addition, BIM technology not only supports CFD simulations but also provides geometric, semantic and location information for solar analysis. The CFD results were validated using measured results. The impact of shaft design changes on the ventilation performance of the shaft and the indoor air quality on the floors was investigated using validated models. In the case of dividing the shafts into two parts, the overall fresh air distribution, thermal comfort and indoor air quality were improved.

Endothelial Cell Distribution After Flow Exposure With Two Stent Struts Placed in Different Angles.

Stent implantation has been a primary treatment for stenosis and other intravascular diseases. However, the struts expansion procedure might cause endothelium lesion and the structure of the struts could disturb the blood flow environment near the wall of the blood vessel. These changes could damage the vascular innermost endothelial cell (EC) layer and pose risks of restenosis and post-deployment thrombosis. This research aims to investigate the effect of flow alterations on EC distribution in the presence of gap between two struts within the parallel flow chamber. To study how the gap presence impacts EC migration and the endothelialization effect on the surface of the struts, two struts were placed with specific orientations and positions on the EC layer in the flow chamber. After a 24-h exposure under wall shear stress (WSS), we observed the EC distribution conditons especially in the gap area. We also conducted computational fluid dynamics (CFD) simulations to calculate the WSS distribution. High EC-concentration areas on the bottom plate corresponded to the high WSS by the presence of gap between the two struts. To find the relation between the WSS and EC distributions on the fluorescence images, WSS condition by CFD simulation could be helpful for the EC distribution. The endothelialization rate, represented by EC density, on the downstream sides of both struts was higher than that on the upstream sides. These observations were made in the flow recirculation at the gap area between two struts. On two side surfaces between the gaps, meaning the downstream at the first and the upstream at the second struts, EC density differences on the downstream surfaces of the first strut were higher than on the upstream surfaces of the second strut. Finally, EC density varied along the struts when the struts were placed at tilted angles. These results indicate that, by the presence of gap between the struts, ECs distribution could be predicted in both perpendicular and tiled positions. And tiled placement affect ECs distribution on the strut side surfaces.

Numerical analysis on temporal size change of expiratory droplets by considering component variation

When conducting computational fluid dynamics (CFD) simulations to investigate the evaporation characteristics of respiratory particles, the over-simplification of droplet compositions may cause inaccuracies in the results. Although some researchers have conducted parametric studies on droplet components, an investigation using CFD simulation is still lacking. Therefore, this study aimed to determine the effect of different components on the temporal size change of expiratory droplets using CFD simulation. Two droplet sizes (10 μm and 100 μm) were selected, and two types of component combinations were considered, both with a volume fraction of 98.2% for water and 1.8% for non-volatile parts. In Scenario 1, the non-volatile part is composed of NaCl (density: 2200 kg/m3, molecular weight: 58.5 kg/kmol), whereas in Scenario 2, the non-volatile part is composed of NaCl, KCl, lactate, and protein (density: 1000 kg/m3, average molecular weight: 293 kg/kmol). Computations were conducted under constant temperature (25 °C) and different relative humidity (0 and 90%). The results showed that the equilibrium size and equilibrium time were strongly dependent on the droplet components. In subsequent investigations, the effects of different droplet components should be considered in the CFD simulations to obtain more accurate results.

Numerical modelling on anchor-soil-water interaction for dynamic installation of gravity installed anchors

The dynamic penetration process of the gravity installed anchor is complex associated with very high shear strain-rate and large plastic shear strain-softening, potential of water entrainment along the anchor-soil interface, moving boundaries and many others. The present study conducted computational fluid dynamics (CFD) simulations to investigate the anchor-soil-water interaction during the anchor dynamic penetration. By setting very fine boundary layers in CFD simulations, the strength mobilisation of the soil at the anchor-soil interface was thoroughly investigated. The numerical results showed that the disturbed soil is very narrow beside the anchor fluke but expands a wide range below it. In CFD analyses, factors influencing the final penetration depth of the anchor were investigated, including the undrained shear strength, parameters of both strain-rate and strain-softening effects, impact velocities, booster weights, and interface adhesion factors. Based on the present simulation results, a theoretical model was proposed to predict the final penetration depth of the anchor.

Sedimentation Tanks for Treating Rainwater: CFD Simulations and PIV Experiments

The removal of solids is the most important step when treating rainwater. The article evaluates two designs of sedimentation tanks that can be used for the continuous separation of fine particles from water: OS—standard sedimentation tanks, and OW—swirl sedimentation tanks. The tanks were studied by conducting computational fluid dynamics (CFD) modeling and particle image velocimetry (PIV) experiments. The settling process in sedimentation tank was carried out at varying operating flow rates. A tank with a modified structure was used for the tests, where water was supplied by a nozzle placed at an angle. This solution made it possible to obtain a rotational flow that transported the suspended particles towards its wall, where downward axial velocity resulted in the settling of particles. Based on the research, it was observed that the flow patterns showed inward flow at the bottom of the tank and an upward flow and the lifting of the settled particles near the hatch at the bottom. The presented experimental measurements provided detailed insight into flow patterns, and valuable calibration and verification data for further CFD modeling. Traditional PIV techniques are useful in the case of standard design, whereas CFD is invaluable for supporting this work and for investigating the design of novel sedimentation tanks.

Fire hazard assessment, performance evaluation, and fire resistance enhancement of bridges

Although the performance of bridge structures under prescriptive fire scenarios has been the subject of numerous studies, performance-based approaches are yet to be developed to achieve an efficient and economical design. This paper presents a performance-based framework that identifies bridges at high fire risk, produces realistic fire scenarios, provides an open source tool to apply the realistic fire load to the thermomechanical model and evaluate the structural performance of the bridge. It also provides guidance to improve the fire resistance of the bridge. The proposed framework is implemented by simulating the I-65 overpass fire accident in 2002, Birmingham, Alabama, USA. Firstly, fire risk of the bridge is estimated by considering various criteria such as the social and economic impact of fire, structural vulnerability, and the likelihood of fire. Secondly, a realistic fire scenario is developed using the real fire accident data by conducting computational fluid dynamics (CFD) simulations. Thirdly, the newly developed open source FSDM framework is utilised to apply the realistic fire load to the thermomechanical model and finally, the fire resistance of the bridge structure is estimated. The unprotected bridge failed after 12 min of fire exposure which is found in compliance with the actual failure time of the bridge during the accident. Further thermomechanical analyses are performed applying different thicknesses of fire protection to estimate the suitable amount of fire protection to achieve improved fire resistance. It is observed that the fire resistance of the bridge can be enhanced up to 60 min by providing a fire protection of 12 mm thickness. This framework presents an important methodology for the highway department and bridge engineers to identify bridges at high fire risk and accurately determine the amount of fire protection required to reduce the fire risk and enhance the fire resistance of these bridges.

Ventilation Characteristics and Performance Evaluation of Different Window-Opening Forms in a Typical Office Room

As most existing office buildings in China lack fresh air systems for ventilation, natural ventilation with windows remains the main means of improving indoor air quality and adjusting indoor thermal comfort. However, knowledge of the ventilation characteristics of various window-opening forms in actual buildings is limited and current methods for evaluating ventilation performance lack a comprehensive consideration of ventilation rate and thermal comfort. In this study, the ventilation characteristics of different window-opening forms were systematically compared by conducting computational fluid dynamics (CFD) simulations. A full-scale experiment was conducted in a typical office room in a university in Tianjin to validate the CFD simulation. Two ventilation modes (wind-driven cross-ventilation and temperature-driven single-sided ventilation), three window-opening angles, and seven window types were investigated. Additionally, the ratio of the ventilation rate to the absolute value of thermal sensation was used to quantify the indoor natural-ventilation performance. The results showed that a sliding window with a full opening has the highest discharge coefficients of 0.68 and 0.52 under wind-driven cross-ventilation and temperature-driven single-sided ventilation, respectively, and top-hung windows opening both inwards and outwards have better ventilation performance than other window types under the two ventilation modes. This study is applicable to the design and practice of natural ventilation.