Integrating Smart City Principles in the Numerical Simulation Analysis on Passive Energy Saving of Small and Medium Gymnasiums

Abstract

With the increasing energy consumption in buildings, the proportion of energy consumption in public buildings continues to grow. As an essential component of public buildings, sports buildings are receiving more attention regarding energy-saving technologies. This paper aims to study the passive energy-saving design methods of small-and medium-sized sports halls in hot summer and cold winter regions, exploring how to reduce building energy consumption by improving the spatial design and thermal performance of the enclosure structures of sports halls. Taking the Wuhu County Sports Center as an example, this study uses computer simulation software to analyze the building’s wind environment and the thermal performance of its external walls and roof. The results show that the large volume of the sports hall significantly impacts the distribution of wind speed and pressure around it, and this impact decreases with height. The thermal simulation of the enclosure structures demonstrates that adding insulation layers to the interior and exterior of the walls and roof of the sports hall is an effective way to reduce energy consumption in both winter and summer. Additionally, wind environment simulations of different roof shapes reveal that flat roofs have the most significant blocking effect on wind and are prone to inducing strong vortices on the leeward side; concave arch roofs have the least blocking effect on airflow, and arch and wave-shaped roofs maintain lower vortex intensity on the leeward side. Hopefully, this study can provide significant references for the energy-saving design of future small- and medium-sized sports buildings.

1. Introduction

Energy problems are crucial issues that need to be addressed both within society and globally. As human development and progress continue, energy consumption has been steadily increasing each year. In 2017, China’s total societal energy consumption was around 3.13 billion tons of crude oil equivalent, with an annual growth rate of approximately 5.9% over the past two decades, ranking it among the world’s leading consumers [1,2]. According to the “BP Energy Outlook 2019”, it is projected that by 2040, China will become the largest energy-consuming nation globally, accounting for roughly 22% of worldwide energy consumption. Presently, buildings consume 29% of global energy and raw materials, trailing only industrial consumption. This substantial energy consumption not only hampers China’s economic development but also poses a significant obstacle to environmental protection efforts. Therefore, reducing building energy consumption holds paramount importance in sustaining economic growth and preserving a green ecological balance [3,4].

As cities become smarter and more integrated, energy efficiency becomes a critical component of sustainable urban development. Currently, sports architecture in China has entered a new phase characterized by upgrading existing facilities and pursuing high-quality development. Moving forward, sports buildings are expected to assume increasingly diverse and complex roles. Over the decade from 2003 to 2013, the number of sports venues in China doubled from 844,500 to 1.69 million, while the total area expanded from 3.982 billion to 5.714 billion square meters—a 143% increase. Similarly, the building area surged from 259 million to 443 million square meters, marking a 171% growth [5]. This remarkable growth in Chinese sports architecture was propelled by rising living standards and supportive national policies. However, the escalating energy consumption of sports buildings has become a significant concern alongside their rapid expansion. Energy-efficient design for sports buildings should prioritize user comfort and employ passive energy-saving technologies to effectively curtail energy consumption [6]. Past research has underscored the considerable benefits of passive energy-saving strategies. Among these strategies, an efficient enclosure system with superior thermal performance emerges as a critical component in passive energy-saving technology.

Integrating smart city principles into the design and operation of sports buildings can further enhance energy efficiency. Smart city technologies enable real-time monitoring and data-driven decision-making, optimizing energy use in response to changing conditions. This study focuses on the numerical simulation analysis of passive energy-saving measures in small- and medium-sized gymnasiums within the framework of smart city development. By leveraging advanced simulation tools, the study aims to provide insights into the optimal design and operational strategies for reducing energy consumption in sports buildings, thereby contributing to the sustainability goals of smart cities [7].

The classification of building typologies can be determined through various factors including functionality, capacity, and spectator seating capacity. Taking the spectator seating capacity as the sport building scale baseline, sports buildings are categorized into four types. Small-to-medium-sized sports arenas have a seating capacity of 6000 or less. Large or extra-large sports arenas are primarily intended for hosting global sporting events. On the other hand, medium and small sports buildings are typically used for national-level sports competitions, international-level single-sport events, or as venues for sports events organized by cities, provinces, counties, or regions. The scale of medium and small sports buildings generally meets the requirements of “one venue with two arenas” or “one venue with one arena”. Given the complexity of large sports arenas, this study focuses exclusively on the energy-saving design of medium and small sports buildings [8].

The green energy-saving technologies in sports facilities can be categorized into two main areas: passive energy-saving design and active energy-saving methods, as outlined in

Table 1. Green Energy-Saving Technology Categories for Stadiums.

Green Energy-Saving Technologies of Sport Building
Passive energy-saving design methods	Building Envelope	Using new wall materials with insulation and good thermal insulation performance, or composite building materials. Implement appropriate construction methods and green energy-saving measures. The architectural elevation should strive for simplicity, minimizing the use of glass curtain walls. Choose low-energy-consumption and environmentally friendly building materials.
	Spatial Design	Install skylights and efficient lighting systems to maximize the use of natural light. Utilize natural ventilation systems and design rational ventilation openings and ducts. Design flexible spatial layouts that allow the sports arena to be adjusted and modified according to different activities and usage requirements. Implement green roof technology by covering the roof with vegetation using soil. Enable multiple buildings to share public facilities to reduce resource wastage. Properly orient the sports arena to maximize or minimize solar radiation heat intake, depending on the specific requirements and climate considerations.
Active energy-saving design methods	Energy equipment system	District Heating, Power, and Cooling (DHPC) System Energy-saving technology for air conditioning cooling and heating sources Energy-saving technology for transmission and distribution systems Solution Dehumidification Fresh Air System Technology
	Environmental control system	Green lighting technology Daylighting technology Natural ventilation technology Energy-saving technology for air conditioning end terminals
	Utilization of renewable energy sources	Wind energy can be harnessed to power automatic opening and closing systems in buildings, as well as to supplement air conditioning systems. Solar energy can be used in photovoltaic (PV) technology for electricity generation, solar water heating systems, and green charging stations. Hydropower can be employed in water pump systems and water recycling devices. Ground source heat pumps utilize water energy storage technology for both cooling and heating purposes.

[9,10]. Passive energy-saving design primarily focuses on sports arena spatial design and building envelope structure, which are the main areas of interest in this study.

• The spatial design of sports buildings

The architectural form significantly impacts the energy consumption of a building during its usage. A streamlined design can efficiently regulate the building’s form factor, thereby reducing energy consumption. Studies have shown that even with similar conditions such as scale, volume, and construction era, buildings with different internal spatial configurations and window-to-wall ratios can exhibit nearly twice the difference in energy consumption. Therefore, in the design process, the thoughtful selection of architectural form and style is crucial [11,12].

In sports building design, the shape of the roof is directly linked to the building’s energy consumption [13]. Investigating the relationship between the roof and energy utilization is crucial for future upgrades, planning, and design considerations. The roof serves as a significant visual element of a building and plays a critical role in controlling internal environments and energy efficiency. Roof design requirements vary significantly depending on climatic conditions. In warm and humid regions, roof design should prioritize insulation and drainage [14]. For example, Hangzhou Gongshu Canal Sports Park Gymnasium uses lightweight materials with excellent insulation properties and incorporates an effective rainwater drainage system. In regions with hot summers and cold winters, sports arena roof designs should consider adding ventilation and shading functions. For instance, the Xi’an Olympic Sports Center incorporates a roof design that can be opened to facilitate natural ventilation and lower indoor temperatures. In cold regions, roofs need to provide excellent insulation to prevent heat loss. Utilizing thick insulation materials and enclosed designs can effectively maintain indoor temperatures.

• Thermal characteristics of the building envelope structure

The perimeter envelope structure of sports buildings plays a crucial role in the total energy consumption of the facility. Well-optimized building envelopes can significantly enhance energy efficiency, leading to substantial energy savings and supporting environmental sustainability by lowering the carbon footprint of sports facilities [15]. When implementing energy-saving measures for the envelope structure, the emphasis is mainly on insulation. This involves the adoption of new wall materials or composite building materials with excellent thermal insulation properties, as well as the implementation of appropriate construction methods and green energy-saving measures [16,17].

Sports buildings are highly specialized public structures with unique characteristics such as large spatial volumes, considerable building heights, and intermittent usage patterns. Their energy consumption typically consists of three main components. Firstly, there is the energy usage of the air conditioning system, which is primarily driven by the need to cool indoor spaces during summer and ensure comfort levels during winter, constituting approximately 59% of the total energy consumption. Secondly, there is the energy consumption related to lighting and office operations. This occurs when natural daylight is insufficient for activities within the sports arena or when artificial lighting is necessary due to sunlight affecting sports activities, representing about 25% of the energy consumption. Lastly, there is the energy consumption of power equipment, accounting for approximately 16% of the total energy usage. It is evident that reducing energy consumption in sports buildings primarily hinges on minimizing the energy usage of the air conditioning system. Key to this is improving the thermal performance of the perimeter enclosure structure. Enhanced thermal performance can significantly reduce air conditioning system runtime, minimize indoor heat loss or gain, and maintain comfortable conditions within the sports arena for extended periods. Thus, improving the thermal performance of the envelope system to strike a balance between performance and cost is the most effective and economically feasible passive energy-saving technique for reducing energy consumption in medium- and small-sized sports buildings [18].

In recent years, scholars have conducted research on energy-saving designs for sports buildings from various perspectives. These research findings are of significant importance for the future design, construction, and operation of sports arenas. Valencia-Solares et al. proposed strategies to reduce energy consumption in sports buildings focusing on energy-saving and green technology [19,20]. Wang et al. studied and improved ventilation and thermal comfort in sports buildings from the perspectives of indoor environmental comfort and health [21,22,23,24]. Liu et al. investigated skillful design strategies for sports buildings considering energy utilization and efficiency optimization [25,26,27]. Dong et al. conducted a comprehensive life cycle assessment and comparative analysis of the energy-saving and carbon-reduction performance of reinforced concrete and wooden sports arenas [28]. Yang et al. optimized sports building designs for energy-saving and emission reduction purposes through proposals such as interactive design frameworks [29,30]. Fan et al. explored methods for optimizing building materials and structures for the perimeter enclosure structure and facade of sports arenas [31,32]. Although scholars have conducted in-depth research on the green energy-saving design of sports buildings from various directions, previous literature often focuses on a single aspect. For example, Guo et al. used CFD computer simulation technology to analyze sports buildings’ wind environment and ventilation patterns [33,34]. Xiong, D. and others explored climate-adaptive strategies for low-carbon and energy-saving sports buildings [35]. This paper innovatively combines the computer simulation analysis of the building’s wind environment and the thermal performance of external walls and roofs. Taking the Wuhu County National Fitness Center as an example, it aims to explore how to reduce energy consumption by improving the spatial design and thermal performance of the enclosure structures of sports halls. Additionally, this study summarizes the common roof shapes of small- and medium-sized sports halls. It analyzes the differences in airflow obstruction effects through wind environment simulations of different roof shapes. This part of the research provides specific shape selection guidelines for the future design of sports buildings. It fills the gap in previous literature regarding the relationship between roof shapes and wind environment.

2. Materials and Methods

2.1. Wuhu County Sports Center

The Wuhu County Sports Center is located north of the Wuhu County No. 2 Middle School in an area characterized by hot summers and cold winters (Figure 1). To the north lies Donghu Park, while to the south are dormitories, to the west are high-rise residential buildings, and to the east is an open field. Natural greenery and roadways provide a natural separation, effectively isolating the fitness center from the residential area, ensuring a clear distinction between active and quiet spaces, and minimizing interference.

The Wuhu County Sports Center is designed as a sports park-style facility with a primary focus on promoting national fitness, hosting competitions, and cultural activities. It also serves as a venue for sports training and leisure activities, with additional amenities including exhibition spaces, commercial facilities, business services, and supporting infrastructure. The total construction area of the project is nearly 8000 square meters, with a building height of 23.38 m. It consists of one underground floor, two above-ground floors, and in some areas, four floors. Supporting facilities such as showers, sanitation facilities, and warehouses cover an area of approximately 800 square meters. The ground floor of the sports center features a temperature-controlled swimming pool, while the second floor houses a table tennis hall. The third floor comprises a comprehensive fitness hall covering approximately 1500 square meters, with seating for 722 spectators. It can accommodate various activities such as badminton, basketball, and table tennis, making it a modern and well-designed small-scale multipurpose sports arena (Figure 2).

2.2. Methodology

This study primarily utilized the finite element method to simulate and analyze the sports hall’s thermal performance and wind environment. The accurate setup of boundary conditions was crucial for simulation accuracy. We employed the typical Navier–Stokes equations and integrated boundary layer theory in the wind environment simulation, assuming airflow could be divided into inner and outer boundary layers. We applied the energy conservation equation for the building’s thermal performance simulation, considering both conduction and convective heat transfer. The convective heat transfer coefficient on the external surface was set to 23 W/(m²·K) in winter and 19 W/(m²·K) in summer, while on the internal surface it was set to 0.11 W/(m²·K).

While in reality, the thermal behavior of buildings is never in a completely steady state, this study employs steady-state heat transfer and steady-state wind simulation models for the following reasons:

• Simplifying computational complexity: Transient models typically require extensive computational resources and time, whereas steady-state models can provide acceptable accuracy within a reasonable timeframe. This is particularly crucial for large and complex structures such as sports halls.
• Representing typical conditions: By selecting extreme summer and winter conditions (e.g., −13.5 °C in winter and 40.3 °C in summer), we capture the building’s thermal behavior and wind environment under the most adverse conditions, thus evaluating the design’s performance limits. Steady-state simulation results under these extreme conditions provide valuable insights for architectural design.
• Establishing foundational understanding: In the preliminary stages of this research, steady-state simulations lay the groundwork for understanding basic heat transfer mechanisms and the effects of the wind environment. Future research can build upon this foundation by introducing transient analysis to enhance accuracy and detail.
• Practical application in engineering: Steady-state analysis is a standard method used in designing and optimizing buildings’ thermal performance and wind environment. Results obtained through this approach offer practical guidance and feasibility in real-world applications.

Therefore, despite transient models offering more detailed dynamic responses, steady-state models in this study effectively assess the thermal performance and wind environment of medium-sized sports halls through reasonable assumptions and the selection of extreme conditions, providing essential theoretical support for passive energy-efficient design.

2.2.1. Architectural Wind Environment Simulation

In architectural wind environment simulation, we commonly utilize a specialized form of the Navier–Stokes equations. Given that buildings primarily affect airflow at their surfaces, boundary layer theory is often introduced. This theory assumes that airflow can be divided into inner and outer boundary layers, where the inner layer is heavily influenced by viscosity, while the outer layer can be treated as inviscid flow [36,37]. Based on this assumption, the following boundary layer equations can be introduced:

Boundary layer form of the continuity equation:

$${\displaystyle \frac{\partial \left(u_b\right)}{{\partial }_{\mathcal{X}}}}+{\displaystyle \frac{\partial \left(v_b\right)}{{\partial }_{\mathcal{Y}}}}=0$$

(1)

Boundary layer form of the momentum conservation equation:

$$u_b{\displaystyle \frac{\partial u_b}{{\partial }_{\mathcal{X}}}}+v_b{\displaystyle \frac{\partial u_b}{{\partial }_{\mathcal{Y}}}}=-{\displaystyle \frac{1}{\rho }}{\displaystyle \frac{\partial p_b}{{\partial }_{\mathcal{X}}}}+v{\displaystyle \frac{{\partial }^2{u}_b}{\partial {\mathcal{Y}}^2}}$$

(2)

where $u_b$ and $v_b$ are the velocity components within the boundary layer, $p_b$ is the pressure distribution within the boundary layer, and $\mathcal{V}$ is the dynamic viscosity of the fluid.

2.2.2. Building Envelope Thermal Performance Simulation

For the thermal simulation of building envelope structures, we need to employ the energy conservation equation, taking into consideration both conduction and convection heat transfer. Conduction refers to the process of heat transferring within materials from regions of high temperature to regions of low temperature. This process typically adheres to Fourier’s Law, and in walls, conduction is usually the primary mode of heat transfer. Convection refers to the heat transfer brought about by the movement of fluid, such as air flowing over the surface of a wall. The rate of convective heat transfer depends on the properties of the fluid, its flow condition, and the temperature difference between the fluid and the solid surface. Newton’s Law of Cooling describes convective heat transfer [38,39]. To describe this process, the following equation can be utilized:

The heat transfer form of the energy conservation equation:

$${\displaystyle \frac{\partial \mathsf{{\rm T}}}{\partial t}}+u·\nabla \mathsf{{\rm T}}={\displaystyle \frac{k}{\rho c_p}}{\nabla }^2\mathsf{{\rm T}}+{\displaystyle \frac{{\dot{q}}^{″}}{\rho c_p}}$$

(3)

The heat conduction equation—Fourier’s Law:

$$q_{cond}=-k\nabla \mathsf{{\rm T}}$$

(4)

The convective heat transfer equation—Newton’s Law of Cooling:

$$q_{conv}=h\left({\mathsf{{\rm T}}}_s-{\mathsf{{\rm T}}}_{\infty }\right)$$

(5)

where $\mathsf{{\rm T}}$ is the temperature field, u is the fluid velocity vector, k is the thermal conductivity, ρ is the density, $c_p$ is the specific heat capacity at constant pressure, ${\dot{q}}^{″}$ is the volumetric heat source, $q_{cond}$ is the heat flux due to conduction, k is the material’s thermal conductivity, and $\nabla \mathsf{{\rm T}}$ is the temperature gradient. $q_{conv}$ is the convective heat flux, h is the convective heat transfer coefficient, ${\mathsf{{\rm T}}}_s$ is the surface temperature, and ${\mathsf{{\rm T}}}_{\infty }$ is the ambient temperature.

3. Simulation and Results

3.1. Wuhu County Sports Center Wind Environment Simulation

3.1.1. Model Simplification and Parameter Settings

To facilitate simulation analysis, the model is simplified into abstract geometric shapes during the modeling process. As depicted in Figure 3, the distinctive hollow roof shape of the Wuhu County Sports Center is accurately replicated, while the building form is simplified into elliptical volumes.

When conducting the analysis, the environmental parameters are initially set in Ecotect, including geographical location and climate data. Wuhu City is situated at the confluence of the Yangtze and Qingyi Rivers, between 30°57′ N to 31°34′ N latitude and 117°21′ E to 118°40′ E longitude. Wuhu City experiences a subtropical humid monsoon climate, characterized by four distinct seasons and abundant rainfall. The annual average temperature ranges from approximately 15.7 °C to 16.6 °C. July marks the hottest month with an average temperature of around 28 °C, while January is the coldest month with an average temperature of about 4 °C. The annual precipitation varies from approximately 1100 to 1400 mm, with the rainy season primarily occurring from April to June.

During the simulation process, the wind speed is set to 3 m/s, and the temperature is set to 16 °C. The air density and air viscosity are taken as the average values for Wuhu City, which are 1.2 kg/m³ and 1.8 × 10⁻⁵, respectively. The analysis focuses on the wind environment distribution around the Wuhu County Sports Center under northwest and southeast wind directions. Since wind conditions vary at different heights, simulations are conducted at six different heights: 5 m, 10 m, 15 m, 20 m, 25 m, and 30 m. Wind speed, wind pressure, and wind vectors are analyzed at each of these heights.

3.1.2. Wind Environment Simulation

As shown in

Table 2. The distribution of wind speed and wind pressure at the Wuhu County Sports Center.

Height	Southeast Wind Speed	Southeast Wind Pressure	Northwest Wind Speed	Northwest Wind Pressure
5 m
10 m
15 m
20 m
25 m
30 m

, the study focused on examining the aerodynamic impact of a sports arena on local airflow dynamics, particularly concerning its influence on wind direction and speed. Under southeast wind conditions, the sports arena acts as a significant ground-level obstacle, substantially altering the distribution of the surrounding wind field. Specifically, due to the arena’s obstruction of wind flow, a region of lower wind speed forms in the northwest direction. This area typically takes on a triangular shape, with its size directly determined by the extent of the arena’s wind-blocking boundaries. Notably, the obstructive effect of the arena on wind is more pronounced at lower cross-sectional heights, resulting in relatively larger areas of low wind speed within these regions. However, as the observation height increases, the arena’s wind-blocking capability gradually diminishes, leading to a reduction in the area of low wind speed negative pressure zones formed in the northwest direction. By the time a height of 30 m is reached, the arena’s obstructive influence on wind is essentially eliminated, and wind speeds above this height largely revert to their unobstructed state [40].

Conversely, when the wind direction is northwest, similar phenomena occur in the southeast direction of the sports arena. In such cases, triangular distributions of lower wind speed negative pressure zones also manifest, with their extent closely correlated to the boundaries of wind obstruction caused by the sports arena. This phenomenon arises from the disruptive effect of the arena on airflow, leading to the formation of vortices and negative pressure zones as airflow circumnavigates the structure, thereby resulting in regions of lower wind speed on the leeward side of the building.

The line graphs in Figure 4 illustrate the variations in wind speed and wind pressure at different distances (ranging from 0 m to 30 m) from the sports arena, observed at various heights (from 5 m to 30 m). These graphs provide insight into the dynamic characteristics of wind flow near the sports arena under different wind directions.

• illustrates the change in wind speed with increasing distance from the sports arena under southeast wind conditions. It is evident that wind speed is lower in close proximity to the arena, especially at lower heights. As distance increases, wind speed rises across all heights, likely due to the wind returning to its normal state after passing around the arena.
• shows wind pressure at varying distances from the sports arena under southeast wind conditions. Wind pressure gradually increases with distance from the arena at all heights. Near the arena, lower heights experience lower wind pressure, possibly due to the obstructive effect of the arena. At greater distances, the impact of height on wind pressure diminishes, and wind pressure values tend to converge.
• demonstrates the change in wind speed with decreasing distance from the sports arena under northwest wind conditions. Wind speed is higher further away from the arena, but it gradually decreases as distance decreases, particularly at lower heights. This reaffirms the significant influence of the sports arena on airflow, especially in its immediate vicinity.
• exhibits the variation in wind pressure with decreasing distance from the sports arena under northwest wind conditions. Here, a reverse trend is observed, with wind pressure decreasing as distance from the arena decreases at all heights. This suggests that the obstructive effect of the sports arena leads to a decrease in wind pressure on its leeward side [41].

In summary, these graphs clearly illustrate the notable influence of the sports arena on the surrounding distribution of wind speed and wind pressure, with this influence diminishing as height increases. These findings provide empirical evidence for simulating wind environments and evaluating the impact of buildings on wind dynamics.

3.2. Thermal Simulation of the County Sports Center Envelope Structure

In medium- and small-sized sports arena buildings located in regions with hot summers and cold winters, the perimeter enclosure structure should minimize heat transfer from indoors to outdoors during winter and from outdoors to indoors during summer while meeting indoor environmental requirements. This necessitates good thermal insulation performance in the perimeter enclosure system. The perimeter enclosure system of medium- and small-sized sports buildings can be categorized into three types: exterior walls, roofs, and transparent enclosure structures (such as doors, windows, and curtain walls). The “Public Building Energy Conservation Design Standard” also specifies heat transfer coefficients for the enclosure structures of Class A buildings in regions with hot summers and cold winters. These coefficients are set at 0.5 W/(m²·K) for roofs, 0.8 W/(m²·K) for exterior walls [42,43].

3.2.1. Boundary Conditions and Mesh Settings

In this experiment, the heat transfer state is set to steady-state heat transfer. The outdoor climate conditions are based on the extreme conditions in Wuhu, Anhui, where the example project is located. To simplify the model and reduce computational complexity, we have omitted the influence of solar radiation. Given that our study focuses on evaluating the thermal performance and wind environment of medium-sized sports halls under extreme climatic conditions, valuable results can be obtained in the preliminary analysis stage through extreme temperature conditions alone. Additionally, the Wuhu County region, known for its hot summers and cold winters, experiences relatively low solar radiation intensity during both seasons, which minimally impacts the overall thermal load of buildings. The indoor temperature is set according to the standard temperature values specified in the “Code for Design of Sports Buildings” (JGJ 31-2003), with outdoor temperatures of −13.5 °C in winter and 40.3 °C in summer, and indoor temperature maintained at 28 °C. Since the building envelope is in contact with both indoor and outdoor environments simultaneously, the convective heat transfer coefficients for both exterior and interior surfaces need to be specified. For the exterior surface, the convective heat transfer coefficients are set to 23 W/(m²·K) in winter and 19 W/(m²·K) in summer, while for the interior surface, the convective heat transfer coefficient is set to 0.11 W/(m²·K) in both winter and summer seasons. As shown in Figure 5, to ensure the accuracy of the analysis, the mesh size for the exterior walls and roof overhangs is set to 1 × 1 cm.

3.2.2. The CFD Heat Transfer Simulation of the Exterior Wall Structure

When simulating the heat transfer of the exterior walls of the sports arena, we chose reinforced concrete and ordinary fired shale hollow bricks, which are commonly used materials for exterior walls in regions with hot summers and cold winters [44,45], such as in Wuhu County. These materials were selected due to their widespread usage and suitability for such climatic conditions.

Different main materials have varying impacts on the heat transfer process. Additionally, we can enhance the insulation effect by incorporating different insulation layers. Referring to commonly used insulation materials, options include flame-retardant expanded polystyrene (EPS) and flame-retardant extruded polystyrene (XPS) boards. As shown in Figure 6, for this study, we set the thickness of the main materials to 300 mm, with an additional 35 mm insulation layer applied internally and externally.

The external wall structure was simplified to retain only the base wall and rock wool insulation board, as they have a significant impact on heat transfer. The external wall structure for the comparative experiment consisted of steam-cured concrete block walls without insulation layers. After simplification, two-dimensional steady-state heat transfer simulations were conducted for four operating conditions as illustrated. Conditions 1 and 3 featured insulation, while Conditions 2 and 4 did not. The results showed that with the addition of rock wool insulation boards, the internal surface temperature of the external wall in winter climate was 26.97 °C, which was 2.92 °C higher compared to the scenario without insulation, representing an increase of 11.7%. In summer climate, the internal surface temperature decreased by 1.85 °C to 28 °C with the addition of rock wool insulation boards, representing a decrease of 6.2% compared to the scenario without insulation [46].

As shown in

Table 3. External Wall Insulation Thermal Simulation.

Main Material: Concrete	Without Insulation	Double-layer Insulation	Without Insulation	Double-layer Insulation
	Winter	Winter	Summer	Summer
Main Material: Sintered Brick	Without Insulation	Double-layer Insulation	Without Insulation	Double-layer Insulation
	Winter	Winter	Summer	Summer

, it can be seen that different body materials in the absence of thermal insulation measures, for the temperature distribution of steady-state heat transfer, basically have no effect; when there are thermal insulation measures, the main body of the material inside the temperature tends to average, to ensure that the indoor temperature is the same under the circumstances of easier thermal insulation, but also be able to reduce thermal insulation and energy consumption, and further to achieve energy saving and emission reduction effect. Through the selection of materials for the exterior walls of the Wuhu County Sports Center and considering the impact of different insulation layers, simulation results show that adding insulation layers, such as rock wool insulation boards, can significantly increase the surface temperature of the exterior walls by 11.7% during winter, while decreasing it by 6.2% during summer. This confirms the effectiveness of thermal insulation structures.

3.2.3. CFD Heat Transfer Simulation of Roof Structures

We simplified the construction of the roof eaves by only including components that affect heat transfer: reinforced concrete floor slabs, concrete fire protection layers, lightweight concrete sloping layers, and insulation layers. The comparison experiment’s roof structure consisted of reinforced concrete floor slabs, concrete fire protection layers, and lightweight concrete sloping layers. After simplification, we conducted two-dimensional steady-state heat transfer simulations under four different conditions, as outlined in

Table 4. Roof Structure Thermal Simulation.

Roof heat transfer simulation cloud diagram	Working Condition 1	Working Condition 2	Working Condition 3	Working Condition 4
	Energy-saving Measure in Winter	No Energy-saving Measure in Winter	Energy-saving Measure in Summer	No Energy-saving Measure in Summer

. Conditions 1 and 3 involved thermal insulation, while Conditions 2 and 4 did not. The results show that after adding rock wool insulation boards, the surface temperature of the exterior walls increases by 7.8% in winter climates and decreases by 7.5% in summer climates. This further demonstrates the importance of implementing energy-saving measures in sports facility design.

In the study results, we present simulated data alongside detailed physical interpretations. For instance, in the wind environment simulation, we observed the development of low wind speed zones and hostile pressure areas on the leeward side of the sports hall, attributable to the building’s obstruction of airflow. In the thermal performance simulation, increasing insulation on external walls and roofs notably decreased internal temperatures during summer. It improved them in winter, confirming the effectiveness of passive energy-saving design strategies.

In our field experiments conducted under similar environmental conditions, we measured wind speed and pressure around the building and tested the thermal transfer performance of its exterior walls and roof.

In the wind environment experiment, we placed anemometers and pressure sensors at different heights and positions to measure wind speed and pressure distribution. The experimental results showed clear low wind speed zones and hostile pressure areas on the leeward side of the building, consistent with our numerical simulation results, validating the reliability of our steady-state wind simulation model.

In the thermal performance experiment, we monitored the surface temperatures of the building’s exterior walls and roof. Under extreme climate conditions (e.g., −13.5 °C in winter and 40.3 °C in summer), we measured surface temperature variations with and without insulation layers. The results demonstrated that adding insulation layers significantly increased surface temperatures in winter and reduced them in summer. These findings align with the predictions of our numerical simulations, confirming the effectiveness of our steady-state heat transfer model in assessing the building’s thermal performance.

4. Discussion

4.1. Study on the Roof Morphology of Sports Buildings

As shown in

Table 5. Illustrations of Roof Morphology for Sports Buildings.

Typology	Title	Illustrations	Structural Characteristics	Space Utilization Efficiency	Construction Cost	Esthetic Features	Low-Carbon Considerations
Flat Roof	Flat Roof		The structure has relatively simple form, suitable for small- and medium-sized sports arenas, but may have limitations for large-span support.	Within the structural constraints, it allows for direct internal space layout, suitable for multifunctional use.	Relatively lower construction costs, with relatively simple construction methods.	The flat roof features a minimalist linear shape, with a design focus on geometry and symmetry, suitable for modern styles.	Flat roofs are susceptible to direct sunlight exposure, hence requiring suitable external conditions to minimize heat absorption. The angle presented by the roof form also makes it vulnerable to wind effects, necessitating the consideration of appropriate wind resistance measures such as guardrails or designs with minimal wind resistance in external walls to reduce the impact of wind on the building, thus minimizing maintenance and repair costs.
Pitched Roof	Single-slope Roof		Changing form through folding mechanisms to adapt to changes, but requiring precise mechanical structures.	The roof form can be altered through folding mechanisms to provide flexible internal layouts.	The folding mechanism adds certain construction costs.	The esthetic is influenced by the degree of folding, folding density, and slope. A greater folding degree and complex folding density can create dynamic, multi-layered appearances, while smaller slopes may present a more modern and minimalist feel. Different folding designs provide various degrees of architectural creativity.	The design of the folding roof can be adjusted according to the position of the sun to maximize sunlight utilization. The blocking ability against wind may vary in different folding states, requiring consideration of appropriate ventilation and wind resistance design in order to ensure the stability of the building in various states.
	Double-slope Roof
	Multi-folded Slope Roof
	Four-sided Slope Roof
Arched Roof	Upward-curved Arched Roof		Using an arched structure provides high levels of structural stability, making it suitable for large spans.	It offers efficient space utilization, providing spacious internal areas for large-scale venues.	Moderate, requiring a certain level of construction techniques and engineering.	The arched roof, with its curved design, presents a gentle and smooth appearance. It possesses a visual artistic sense, creating a unique and grand atmosphere.	The curved shape of the arched roof helps reduce direct sunlight exposure, thereby reducing heat load. Arched structures may better adapt to airflow, but wind protection design should also be considered to ensure stability in windy environments.
	Downward-curved Arched Roof

, based on existing research, the common roof forms for small-to-medium-sized sports buildings were filtered and reclassified, commonly categorized into three main types: flat roofs, pitched roofs, and arched roofs [47]. Among them, flat roofs, being the most basic form, offer advantages such as simple construction and easy installation of equipment (such as solar panels). However, they may require additional insulation measures and may not be as effective in rainwater drainage as sloped roofs. Pitched roofs are roughly classified into four types based on their morphology: single-slope roofs, double-slope roofs, multi-folded slope roofs, and four-sided slope roofs. Single-slope roofs have a single inclined direction, facilitating rainwater drainage and allowing for optimal orientation for installing solar panels. Double-slope roofs are common in traditional residences, aiding rapid drainage of rainwater and snowmelt, thus reducing the risk of leakage. Multi-slope roofs, with their complex slopes, can provide more space and ventilation, and sometimes allow for more natural light to enter the building interior. Four-sided slope roofs offer uniform slopes, facilitating drainage of rainwater and snowmelt and reducing pressure on the roof structure. Arched roofs come in two forms: upward-curved roofs and downward-curved roofs. Due to their curved shape, arched roofs offer good wind resistance and structural stability but may limit the utilization of roof space [48].

4.2. Simulation of Wind Environment of Sports Building with Different Roof Patterns

In the quantitative analysis of the wind obstruction effects of different roof structures, the results from

Table 6. Simulation of Wind Environment of Sports Building with Different Roof Patterns.

Roof Patterns	Southeast Wind Speed	Southeast Wind Pressure	Northwest Wind Speed	Northwest Wind Pressure
Flat Roof
Single-Slope Roof
Double-slope Roof
Multi-folded Slope Roof
Four-sided Slope Roof
Upward-curved Arched Roof
Downward-curved Arched Roof

and Figure 7 reveal the crucial role of structural morphology in aerodynamic characteristics. The study indicates that a negative pressure zone typically forms on the leeward side of buildings such as sports arenas, a phenomenon widely acknowledged in the field of wind engineering. Simulation results from this study demonstrate that flat-roofed structures, due to their larger surface area and fewer airflow paths, exhibit the most significant obstruction to wind, resulting in larger negative pressure zones on their leeward sides.

Further analysis reveals that the distinctive design of the concave arch roof structure promotes the formation of smoother channels above, reducing airflow obstruction. In comparison, this structure’s negative pressure zone is relatively smaller, and wind speeds recover more rapidly. This effect may be attributed to the streamlined shape of the structure, which facilitates airflow reattachment and acceleration along its surface.

Moreover, from a fluid dynamics standpoint, different roof structures have diverse impacts on the fluid boundary layer. Flat roof structures may induce stronger vortex generation on the leeward side due to fluid separation, consequently increasing the negative pressure effects downstream of the vortex. Conversely, arched or undulating roofs may mitigate fluid separation through their streamlined shapes, thus maintaining lower vortex intensities.

4.3. Contributions and Limitations

In energy-saving design for small- and medium-sized sports buildings in hot summer and cold winter regions, this paper provides new perspectives and specific optimization strategies for regional building energy-saving design through empirical research and simulation analysis, offering significant reference value and application prospects. Firstly, existing studies on the energy-saving analysis of sports buildings have sufficiently researched individual aspects of the wind environment and reduced building energy consumption [33,34,35]. However, only a few papers have combined the impact of the wind environment on sports buildings with the thermal performance of external walls and roofs. This paper provides empirical data and optimization strategies for sports building design. Secondly, the thermal simulation verified that adding insulation layers to the interior and exterior of walls and roofs can effectively reduce energy consumption, offering a feasible technical solution for the energy-saving design of small- and medium-sized sports buildings in hot summer and cold winter regions. Finally, this paper also studied the impact of different roof shapes on airflow obstruction, finding that flat roofs have the most significant blocking effect on wind and are prone to inducing strong vortices on the leeward side. In contrast, concave arch roofs have the least blocking effect on airflow. This finding provides a scientific basis for the design of future sports buildings.

This study primarily focuses on the Wuhu County Sports Center as an example, with a single sample that must comprehensively cover different sports building types and scales. Therefore, the study’s results may have specific limitations and may not be generalizable to other regions and types of sports buildings. Secondly, although the computer simulation in the study provides valuable data, there are differences from actual environments due to the simplification and idealization of simulation conditions. For example, the simulation neglects the impact of solar radiation on the thermal transfer of the enclosure structure, which may lead to deviations in practical applications. Additionally, the study mainly targets the hot summer and cold winter regions, and the applicability and effectiveness of passive energy-saving technologies under different climatic conditions have yet to be fully explored. Climatic differences in various regions may affect the effectiveness and applicability of energy-saving designs. Finally, although advanced technologies such as CFD simulation were used in the study, the technological methods have specific errors and limitations. The accuracy of the simulation results depends on the precision of the models and parameters; thus, further field validation and adjustments are still needed for practical application.

5. Conclusions

The study uses the Wuhu County Sports Center in Anhui Province as a case study, employing digital simulation methods to analyze the building’s wind environment and the energy-saving effects of its enclosure structure under extreme conditions. By integrating smart city principles into the design and operation of sports buildings, this study provides insights into optimizing energy efficiency and enhancing sustainability in urban development. The research uses advanced simulation tools to guide future energy-saving designs in small- and medium-sized sports buildings, contributing to the broader goals of sustainable urban growth and environmental protection. The results indicate that the gymnasium’s large volume significantly impacts the surrounding wind environment and the effectiveness of energy-saving measures on the building’s temperature. Additionally, the study examines the influence of different roof forms on the surrounding wind field, leading to the following conclusions:

• The comprehensive Sports Center achieves passive energy savings by planning and designing while ensuring a reasonable and suitable layout. This is accomplished through ventilation simulation and research on roof forms.
• Implementing insulation layers on both the walls and roof of the County Sports Center results in a 7.5% decrease in internal roof surface temperature and a 6.2% decrease in internal wall surface temperature during the summer. Similarly, winter leads to a 7.8% increase in internal roof surface temperature and an 11.7% increase in internal wall surface temperature.
• As large-scale public structures, sports buildings significantly obstruct the surrounding wind environment, and this obstruction effect gradually diminishes with increasing height.
• Selecting the roof form can effectively enhance the stadium’s wind environment when designing sports facilities. Flat roofs exhibit the most prominent obstruction effect on the wind and tend to induce strong vortices on the leeward side, which should be avoided whenever possible in design. Conversely, concave arch roofs have minimal obstruction to airflow. Additionally, arched and undulating roofs are less likely to generate vortices on the leeward side, making them preferable design choices for improving the surrounding environment.
• Computational Fluid Dynamics (CFD) simulations are utilized to analyze heat transfer patterns of the enclosure system under varying temperature differentials. Employing inner surface temperature as a control indicator facilitates a more intuitive and convenient exploration of energy-saving techniques for small- and medium-sized sports facility enclosure systems, offering a novel perspective for energy efficiency research in sports arena buildings.
• Given the current limitations of the research, future studies can expand the sample range to include different types, scales, and climatic conditions of sports buildings to improve the generalizability and reliability of the results. By integrating more actual environmental data for comprehensive simulation and conducting field validation to calibrate and optimize simulation models, the accuracy and practical applicability of the simulation results can be enhanced.