A method for determining equivalent pressure coefficient of mountain thunderstorm strong wind driven rain

Abstract

The application discloses a method for determining equivalent pressure coefficient of mountain thunderstorm strong wind and rain. In view of the problem that the prior art ignores the deviation of load evaluation on the leeward surface caused by the raindrop over-mountain movement, the application establishes a thunderstorm downburst flow and rain coupling numerical field containing a mountain terrain and a building model, uses a discrete phase model to simulate the movement of raindrops with different particle diameters, and identifies whether the raindrops over-mountain. The wind pressure on the building surface and the impact force of the over-mountain and non-over-mountain raindrops are obtained. The wind pressure coefficient and the equivalent rain pressure coefficient are calculated respectively, wherein the equivalent rain pressure coefficient distinguishes the contribution of the over-mountain and non-over-mountain raindrops, and the equivalent total pressure coefficient is obtained by adding the two. The occurrence condition and the particle diameter-distance quantitative law of the raindrop over-mountain movement are disclosed for the first time, the contribution of the over-mountain movement to the rain load on the leeward surface is considered, and unified and accurate equivalent load coefficients are provided for the wind and rain resistance design of mountain buildings. The application can be integrated in a computer system or a storage medium for engineering practice.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary technical field of wind load assessment and computational fluid dynamics in civil engineering. Specifically, it relates to a method, system, and medium for determining the equivalent static load of a building structure under the coupled action of thunderstorm bursts and heavy rainfall in complex mountainous terrain conditions. Background Technology

[0002] With the advancement of urbanization and infrastructure construction in mountainous areas, mountain buildings face serious threats from extreme wind climates. Thunderstorm downbursts are hazardous wind fields characterized by sudden onset and high near-surface wind speeds, often accompanied by heavy rainfall, creating a harsh environment of wind-rain coupling. Existing building load codes and most research methods mainly target conventional atmospheric boundary layer winds, or consider wind or rain loads under flat terrain alone, making it difficult to accurately assess the disturbance of complex mountain terrain on the wind-rain coupling field and its comprehensive effects on buildings.

[0003] Specifically, existing technologies have the following shortcomings: First, in simulating mountain wind fields, existing studies can simulate the impact of topography on pure wind fields, but do not consider rainfall and its interaction with the wind field. Second, in studying wind-rain coupling, existing work can simulate the wind and rain loads on building facades in flat terrain, but their models do not consider the fundamental changes that mountainous terrain brings to the near-surface wind field structure and raindrop trajectories. Most importantly, existing technologies completely ignore a key physical phenomenon that mountainous terrain can cause: driven by strong winds, some raindrops may rise along the mountain slope and cross the ridge, impacting buildings on the leeward side. This "raindrop crossing the mountain" will drastically change the load distribution on the leeward side of the building, and existing methods, because they fail to identify and simulate this phenomenon, result in serious biases or even omissions in the load assessment of leeward-side buildings.

[0004] Therefore, there is an urgent need in this field to propose a method that can accurately simulate the wind and rain coupling field under mountainous terrain, especially to identify and quantify the phenomenon of "raindrop movement across mountains", and thus provide a unified and accurate equivalent wind and rain load coefficient for mountain buildings (especially sloping roof buildings). Summary of the Invention

[0005] The present invention aims to overcome the above-mentioned defects of the prior art and provide a method, system and medium for determining the equivalent pressure coefficient of buildings that can accurately assess the coupled load of thunderstorms and wind and rain in mountainous terrain.

[0006] To achieve the above objectives, the first aspect of this invention provides a method for determining the equivalent pressure coefficient of buildings under strong winds and rain-driving forces during thunderstorms in mountainous terrain. The core of this method lies in constructing a high-fidelity mountain wind-rain coupling numerical field, systematically identifying and quantifying for the first time the "mountain-crossing movement" law of raindrops of different sizes in the mountain wind field, incorporating this law into the calculation of rain load on building surfaces, and ultimately proposing an equivalent total pressure coefficient that comprehensively reflects the coupling effect of wind pressure and rain pressure.

[0007] According to an embodiment of the present invention, the method includes the following steps: establishing a thunderstorm downburst wind-rain coupled numerical field including a mountain terrain model and a building model, wherein the movement of raindrops of different sizes in the wind field of the mountain terrain is simulated by a discrete phase model, and whether the raindrops undergo cross-mountain movement across the ridge is identified; based on the wind-rain coupled numerical field, the wind pressure coefficient at specific locations on the building surface is calculated respectively. and equivalent rain pressure coefficient The equivalent rain pressure coefficient The calculation distinguishes between impact loads generated by raindrops that have undergone mountain-crossing motion and those that have not; according to the formula Calculate the equivalent total pressure coefficient at the location; and conduct a building load assessment based on the equivalent total pressure coefficient.

[0008] This solution addresses the critical issue of existing technologies neglecting the mountainous terrain that causes raindrops to travel across mountains. By introducing a mechanism for identifying and quantifying this mountain-crossing motion into the wind-rain coupled numerical field, it is the first to incorporate leeward rain load into the building load assessment system, fundamentally improving the completeness and accuracy of load assessment for mountainous buildings, especially those located on the leeward side of ridges.

[0009] In some embodiments, the mountain terrain model adopts a cosine mountain model, and its terrain function expression is as follows:

[0010]

[0011] in, The height of any point on the mountain. The height of the mountaintop. The horizontal distance between the mountaintop and the mountainside. , This is the mountain shape coefficient; for axisymmetric mountains, The value is 1.

[0012] This cosine mountain model can accurately describe the topographic features of axisymmetric mountains. By adjusting the height of the mountain peak and the distance to the mid-mountain, it can flexibly represent the geometric shape of mountains of different sizes, providing a mathematical basis for wind field simulation in mountainous terrain.

[0013] In some implementations, the step of identifying whether raindrops have undergone "mountain-crossing movement" includes: tracking the trajectory of raindrops released from the windward side of a mountain; if the elevation of the highest point of the trajectory is greater than or equal to the elevation of the ridgeline, then the raindrop is determined to have undergone mountain-crossing movement; and obtaining the distances between raindrops of different particle sizes and different outflow centers through numerical simulation. The proportion of mountain crossings below, among which, It is the horizontal distance between the center of the thunderstorm outflow and the foot of the windward mountain.

[0014] By systematically tracking the trajectory of raindrops and establishing a mountain-crossing motion discrimination criterion based on elevation comparison, this invention achieves for the first time a quantitative assessment of the proportion of mountain-crossing motion of raindrops of different particle sizes at different terrain locations. This provides a data foundation for the accurate calculation of rain load on leeward buildings and overcomes the shortcomings of existing technologies that equate the leeward side of mountain buildings with rain load under plain conditions.

[0015] In some implementations, when At that time, raindrops with a diameter of 1.0 mm undergo a mountain-crossing motion; when At that time, only raindrops with a diameter of 0.6 mm or less undergo the movement across the mountain; when At that time, only raindrops with a diameter of no more than 0.2 mm underwent the movement across the mountain; among them, The diameter of the outflow from the impact burst.

[0016] The aforementioned quantitative law is revealed for the first time in this invention through extensive numerical simulations. This particle size-distance correspondence quantifies the conditions under which raindrops cross mountains, solves the problem that existing technologies completely lacked a solution for determining whether raindrops have crossed mountains, and provides clear key parameters for assessing building loads in different terrain locations.

[0017] In some embodiments, the equivalent rain pressure coefficient In the calculation, the raindrop impact load caused by the mountain crossing movement and acting on the leeward side of the building is included separately, which is different from the raindrop impact load that does not involve mountain crossing movement and only acts on the windward side and roof.

[0018] In some embodiments, the wind pressure coefficient The calculation formula is The equivalent rain pressure coefficient The calculation formula is ,in This refers to the wind pressure value at a specific location on the building surface. The total impact force generated by raindrops that have undergone mountain-crossing motion and those that have not. For the area of ​​force application, For reference pressure, air density, For reference wind speed.

[0019] The equivalent total pressure coefficient unifies the effects of wind pressure and additional rain load into a single index. By referring to the dimensionless method of the traditional wind pressure coefficient, it enables engineering designers to directly apply this coefficient to determine load values.

[0020] In some implementations, the formula for calculating the average rain pressure is:

[0021]

[0022] in, For rain load, To calculate the area;

[0023] The rain load Calculated based on the formula for raindrop impact force:

[0024]

[0025] in, The density of water, The diameter of the raindrop. The final velocity of the raindrop when it hits the wall, and the collision time. .

[0026] The impact force formula based on the collision dynamics of spherical raindrops can accurately calculate the instantaneous impact force generated when raindrops of different sizes hit the building surface at different speeds. This formula comprehensively considers two key parameters, raindrop diameter and impact velocity, and is suitable for quantitative calculation of rain load under various wind and rain coupling conditions.

[0027] In some implementations, the calculation of the wind-rain load ratio factor is also included. Steps:

[0028]

[0029] in, The coefficient is the wind pressure coefficient; Used to quantify the contribution of rain load to the total load and to identify load-sensitive areas on building surfaces.

[0030] The wind-rain load ratio coefficient can quantitatively characterize the proportion of rain load in the total load, and is used to identify key parts of building surfaces that are significantly affected by wind and rain. This is achieved through comparison with numerous operating conditions. This invention provides the first analysis of the distribution patterns of values ​​under different terrain locations. The specific range of values ​​provides a quantitative basis for the design of localized reinforcement against wind and rain.

[0031] In some implementations, the method is tailored to different radial locations of the building within a mountainous wind field. Implemented separately, the radial position includes at least directly below the downburst. At the foot of the windward mountain Windward mountainside Mountain Top leeward mountainside and the foot of the leeward mountain .

[0032] By setting six key radial locations, the system covers all typical working conditions of buildings in mountainous downwind storm fields, forming a complete load database. The radial locations correspond one-to-one with the characteristic points of the mountain terrain, enabling the equivalent pressure coefficient to directly reflect the spatial influence of mountain terrain on building loads.

[0033] A system for determining the equivalent pressure coefficient of a building under thunderstorms and strong winds in mountainous terrain includes: one or more processors; a memory storing instructions executable by the one or more processors; the instructions being executed by the one or more processors to cause the system to implement the method described in any of the preceding claims.

[0034] The system modularizes the above methods into processor-executable instructions, with clear data transfer relationships and interface standards between modules, facilitating rapid implementation in engineering practice.

[0035] A tenth aspect is a computer-readable storage medium having a computer program stored thereon, characterized in that the computer program, when executed by a processor, implements the method as described in any of the preceding claims.

[0036] This storage medium facilitates the portability and distribution of the above methods, and can be reused on different computing devices, thus expanding the application scope of the technical solution. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the cosine mountain cross section used in an embodiment of the present invention.

[0038] Figure 2 This is a schematic diagram of the movement trajectories of raindrops of different diameters (0.2mm, 0.6mm, 1.0mm, 1.8mm, 3.5mm) when the distance between the outflow center of the storm surge and the foot of the windward mountain is R=0.5Djet.

[0039] Figure 3 This is a schematic diagram of the movement trajectories of raindrops of different diameters when the distance between the outflow center of the storm surge and the foot of the windward mountain is R=1.0D.

[0040] Figure 4 This is a schematic diagram of the movement trajectories of raindrops of different diameters when the distance between the outflow center of the storm surge and the foot of the windward mountain is R=2.0Djet.

[0041] Figure 5 A schematic diagram showing the selection of rain pressure calculation points on the surface of a pitched roof building (arranged along the building's midline).

[0042] Figure 6 The Cpei distribution curves are the equivalent total pressure coefficients of the median of buildings under different rainfall intensities when the building is located directly below a downburst (r=0).

[0043] Figure 7 a and Figure 7 b represents the distribution curves of the equivalent total pressure coefficient Cpei of the building median under different rainfall intensities, when the building is located at the foot of the windward mountain (r=0.5Djet) in flat and mountainous terrain.

[0044] Figure 8 a and Figure 8 b represents the distribution curves of the equivalent total pressure coefficient Cpei of the building median under different rainfall intensities, when the building is located on the windward side of the mountain (r=1.0Djet) in flat and mountainous terrain.

[0045] Figure 9 a and Figure 9 b represents the distribution curves of the equivalent total pressure coefficient Cpei of the building's median, corresponding to different rainfall intensities under flat and mountainous terrains, when the building is located on a mountaintop (r=1.5Djet).

[0046] Figure 10 a and Figure 10 b represents the distribution curves of the equivalent total pressure coefficient Cpei of the building median under different rainfall intensities when the building is located on the leeward side of the mountain (r=2.0Djet) in flat and mountainous terrain.

[0047] Figure 11 a and Figure 11 b represents the distribution curves of the equivalent total pressure coefficient Cpei of the building median under different rainfall intensities when the building is located at the foot of the leeward mountain (r=2.5Djet) in flat and mountainous terrain.

[0048] Figure 12 The distribution curve of the wind-rain load ratio coefficient β on the midline is shown for buildings located at different radial positions under flat terrain and extreme rainfall intensity (200 mm / h).

[0049] Figure 13 The distribution curve of the wind-rain load ratio coefficient β on the midline is shown when the building is located at different radial positions under mountainous terrain and extreme rainfall intensity (200 mm / h). Detailed Implementation

[0050] The objectives, technical solutions, and advantages of this invention are now clearer. The technical solutions in the embodiments of this invention will be described in detail and completely below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention.

[0051] Example 1: Establishment and Verification of Coupled Numerical Field of Mountainous Wind and Rain

[0052] This embodiment describes how to establish a reliable numerical field coupled with thunderstorm downburst and wind in mountainous terrain, which is the basis for subsequent load calculations.

[0053] First, a geometric model of the mountain terrain is established. An axisymmetric cosine mountain is used as the standard terrain model, and its outline is defined by the following function:

[0054]

[0055] In the formula, z is the height of any point on the mountain, in meters; H is the height of the mountain peak of the cosine mountain, in meters; L1 is the horizontal distance between the mountain peak and the mountainside, in meters; C is the mountain shape coefficient. For an axisymmetric cosine mountain, C takes the value of 1.

[0056] In this embodiment, two sets of parameters are set for scaled-down model verification and full-scale engineering simulation. The scaled-down model parameters are as follows: mountain height H is 0.2 meters, distance L1 from the mountainside is 0.5 meters, downburst outflow diameter Djet is 0.4 meters, outflow height Hjet is 1.2 meters, outflow velocity Vjet is 9 meters per second, and the horizontal distance R between the windward foot of the mountain and the outflow center is 0.8 meters. The full-scale model parameters are as follows: H is 400 meters, L1 is 1000 meters, Djet is 800 meters, Hjet is 2400 meters, Vjet is 18 meters per second, and R is 1600 meters.

[0057] Secondly, the computational domain for the downburst flow in the mountainous region is defined. The overall dimensions of the computational domain include the downburst outflow height, outflow diameter, outflow velocity, and the horizontal distance between the windward foot of the mountain and the outflow center. See [link to documentation]. Figure 1 , Figure 1 This is a schematic diagram of the cosine mountain cross section.

[0058] Next, the computational domain was meshed. A structured hexahedral mesh was used to discretize the computational domain, with mesh refinement applied to the mountain surface, near-surface region, and the expected downburst impact zone. To verify mesh independence, three meshes of approximately 12.06 million, 15.4 million, and 18.56 million were generated for the full-scale model. Vertical wind speed profiles at the windward foot of the mountain were extracted and compared. The results showed that the wind profile curves of the 15.4 million mesh and the 18.56 million mesh largely overlapped, with a difference of less than 2%. Therefore, the 15.4 million mesh was selected for subsequent full-scale simulations, ensuring both accuracy and computational efficiency.

[0059] Next, a turbulence model was selected and boundary conditions were set. The continuous phase wind field was simulated using computational fluid dynamics software. The turbulence model chosen was the SSTk-ω model of shear stress transfer, which better handles near-wall flow and separated flow, and is suitable for the complex terrain flow problem of this invention. The boundary conditions were set as follows: the velocity inlet boundary was located at the top center of the computational domain, simulating downburst outflow, with a turbulence intensity of 2% and a hydraulic diameter of Djet equal to the downburst outflow diameter; the pressure outlet boundary was located on the sides and top of the computational domain in the non-inlet region, with a turbulence intensity of 2% and a hydraulic diameter of Djet; the slip wall boundary used a zero shear stress condition; the ground and mountain surfaces used a no-slip wall condition, and an equivalent sand roughness was set to simulate type B terrain (roughness length zo = 0.02 m), implemented through a user-defined function; the symmetry plane boundary utilized the model's axisymmetry and was set as a symmetry plane type to reduce computational load. The solver is a pressure-based solver, and the velocity-pressure coupling uses the SIMPLE algorithm. The momentum equation, turbulent kinetic energy equation, and turbulent dissipation rate equation are all discretized using a second-order upwind scheme.

[0060] Finally, the model's effectiveness was verified. To verify the accuracy of the numerical model, a physical model experiment was conducted for comparison. The experiment was carried out in a large wind tunnel jet device, using the same geometric dimensions and inflow conditions as the scaled-down numerical model. Seven measuring points were arranged on the mountain surface, and vertical wind speed profiles were measured using a multi-hole probe. The numerical simulation results using the SSTk-ω model showed good agreement with the experimental data at all measuring points, especially in the near-surface region, verifying the reliability of the numerical model in simulating the storm surge wind field under mountainous terrain.

[0061] Further scale effect analysis was conducted. To analyze the influence of different scale models on the simulation results of downburst wind fields under mountainous terrain, wind profiles of full-scale and scaled models under the same turbulence model simulation results were compared. At the foot of the windward mountain and at the same location, the results obtained from the scaled and full-scale simulations were almost indistinguishable. However, after the wind flows over the mountain, the difference between the scaled and full-scale simulation results gradually increases with the increase of radial distance. Especially after the wind crosses the mountaintop, the velocity obtained from the full-scale simulation is significantly greater than that obtained from the scaled simulation. This indicates that the scale effect of downbursts in mountainous terrain is significant due to the complex flow generated by the bluff body around the leeward side of the mountain. Therefore, for numerical simulation of downbursts under mountainous terrain, to obtain results closer to reality, full-scale or smaller scale ratio calculation models should be preferred.

[0062] Example 2: Raindrop Discrete Phase Simulation and Mountain Crossing Motion Analysis

[0063] This embodiment adds discrete phase raindrops to the convergent wind field established in Embodiment 1 to simulate wind-driven rain, and focuses on analyzing mountain-crossing motion.

[0064] First, the initial conditions for raindrops of different sizes are determined. The raindrop spectrum distribution is determined based on the widely used Marshall-Palmer index distribution law, namely:

[0065]

[0066] In the formula, N(D) represents the number concentration of raindrops with diameter D, N0 is a constant, and Λ is the slope factor. Based on the principle of number dominance, five representative particle sizes of 0.2 mm, 0.6 mm, 1.0 mm, 1.8 mm, and 3.5 mm were selected for simulation. The control ranges for these five particle sizes are as follows: 0.2 mm: 0 to 0.4 mm; 0.6 mm: 0.4 to 0.8 mm; 1.0 mm: 0.8 to 1.5 mm; 1.8 mm: 1.5 to 2.5 mm; and 3.5 mm: 2.5 to 6 mm.

[0067] Based on the compositional distribution of raindrops of different sizes in rainfall provided by BEST, and the relationship between different components of each size and rainfall intensity, the distribution weight of each size is determined as follows:

[0068]

[0069]

[0070]

[0071] In the formula, r is the raindrop diameter in millimeters; F represents the percentage of the total volume of raindrops with a diameter smaller than r; I is the rainfall intensity in millimeters per hour; W is the weight of raindrops per unit volume of air in cubic millimeters per cubic meter; B1, B2, p, q, and n are constants, with values ​​corresponding to the rainfall intensity. This embodiment studies downbursts accompanied by heavy rain at a rainfall intensity of 100 millimeters per hour, with the corresponding constant values ​​being B1=1.30, B2=67, p=0.232, q=0.846, and n=2.25. The relative volume fraction and mass flow rate of rain within five representative particle size control ranges can be calculated using this formula.

[0072] Secondly, the simulation operation procedure for the coupled wind and rain field was set up. The wind and rain field was simulated using a wind and rain coupled calculation method. The specific operation procedure is as follows: The continuous phase solution parameters were set to be consistent with the full-scale downburst wind field solution parameters in Example 1; the discrete phase model was opened and set to coupled solution mode. To balance calculation accuracy and efficiency, the discrete phase was coupled once every 20 continuous phase steps; in the discrete phase injection interface, parameters corresponding to the five droplet sizes were set, including raindrop diameter, initial raindrop velocity, and mass flow rate. The initial velocity values ​​of the five droplet sizes were taken as... The incoming flow velocity at the wind field velocity inlet is the same; the gravitational acceleration is set to be downward along the vertical coordinate axis, with a value of 9.8 m / s². The splashing effect after raindrops hit the ground is ignored. For all boundaries of the wall type, the discrete phase boundaries are set to capture type, and the discrete phase boundaries at the velocity inlet boundary and pressure outlet boundary are set to escape type. Monitoring points are set and calculations are performed. After the calculation converges, the motion trajectory of raindrops of different sizes in the wind field is extracted, and the velocity, mass flow rate and impact angle of raindrops of different sizes hitting the wall are obtained.

[0073] Next, we identified and quantified the mountain-crossing motion of raindrops. We defined raindrops as those released from the windward side of a mountain, and tracked their trajectories. If the elevation of the highest point of the trajectory is greater than or equal to the elevation of the ridgeline, the raindrop is considered to have undergone mountain-crossing motion. To study the influence of the mountain on the raindrop trajectory, we examined the raindrop trajectories at distances of 0.5, 1.0, and 2.0 times the outflow diameter from the windward foot of the mountain to the outflow center of the downburst.

[0074] See Figure 2 , Figure 2 This diagram shows the trajectories of raindrops of different diameters at a distance of 0.5 times the outflow diameter from the storm surge outflow center at the windward foot of the mountain. As can be seen from the diagram, when the distance between the storm surge outflow center and the windward foot of the mountain is R = 0.5Djet, raindrops with a diameter of 1.0 mm will move across the mountain driven by the wind. As the raindrop diameter increases, the distance the raindrop travels along the mountain becomes smaller. Raindrops with a diameter of 0.6 mm rise to the mountainside. Raindrops with a diameter greater than 1.0 mm show almost no movement across the mountain.

[0075] See Figure 3 , Figure 3 This diagram shows the trajectories of raindrops of different diameters at a distance of 1.0 times the outflow diameter from the foot of the windward mountain to the center of the storm outflow. When R = 1.0Djet, only raindrops with a diameter of 0.6 mm can impact and cross the mountaintop under the driving force of the wind, while raindrops with a diameter of 0.2 mm rise to the mountainside. Raindrops of other diameters are almost unaffected by the mountain topography.

[0076] See Figure 4 , Figure 4This diagram shows the trajectories of raindrops of different diameters at a distance of 2.0 times the outflow diameter from the foot of the windward mountain to the outflow center of the downburst. When R = 2.0Djet, except for a small number of raindrops with a diameter of 0.2 mm that rise along the mountain surface, the trajectories of other raindrops are the same as those of downburst raindrops in flat terrain.

[0077] The analysis in this embodiment leads to the conclusion that the distance between the downburst outflow center and the windward foot of the mountain determines the intensity of raindrop cross-mountain movement. The closer the distance, the more significant the cross-mountain movement, and the easier it is for large-diameter raindrops to impact the leeward side of the mountain; the farther the distance, the weaker the cross-mountain movement, and only small-diameter raindrops can affect the mountain. This conclusion has significant guiding implications for accurately predicting rain loads on mountain buildings at different locations.

[0078] Example 3: Load Calculation and Equivalent Pressure Coefficient Determination for Sloping Roof Buildings

[0079] In this embodiment, a typical double-sloped roof building (slope angle 16 degrees) is placed in a mountainous wind and rain field, and the equivalent pressure coefficient of its surface is calculated.

[0080] First, a geometric model of the building is established. Numerical verification of the surface wind pressure coefficient distribution at 1.0 times the outflow diameter of the downburst outflow center is performed on both a cubic building and a double-sloped roof building with a 16-degree slope. Then, further extended research is conducted on the double-sloped roof structure with a 16-degree slope.

[0081] For the double-sloped roof building model, the average roof height is 0.036 meters, corresponding to a full-scale height of 23.40 meters; the eaves height is 0.031 meters, corresponding to a full-scale height of 20.15 meters; the building height is 0.039 meters, corresponding to a full-scale height of 25.35 meters; the roof slope angle is 16 degrees; and the horizontal cross-sectional dimensions are 0.065 × 0.065 square meters, corresponding to a full-scale dimension of 42.25 × 42.25 square meters.

[0082] Secondly, calculation scenarios were set up. For sloping roof buildings, the wind and rain load effects were simulated under two different terrain conditions and six different radial positions. The six radial positions were 0 times the outflow diameter, 0.5 times the outflow diameter, 1.0 times the outflow diameter, 1.5 times the outflow diameter, 2.0 times the outflow diameter, and 2.5 times the outflow diameter. In downhill storm flows, 0.5 times the outflow diameter corresponds to the windward foot of the mountain, 1.0 times the outflow diameter corresponds to the windward mid-mountain position, 1.5 times the outflow diameter corresponds to the mountaintop position, 2.0 times the outflow diameter corresponds to the leeward mid-mountain position, and 2.5 times the outflow diameter corresponds to the leeward foot of the mountain. This embodiment sets up 12 scenarios, each calculating for five rainfall intensities: 0 mm / h, 32 mm / h, 64 mm / h, 100 mm / h, and 200 mm / h, for a total of 60 calculation scenarios.

[0083] Next, the computational domain was meshed. To examine mesh dependency, for the case of a pitched roof building in a downdraft wind field at a radial distance of 1.0 times the outflow diameter, three sets of meshes with sizes of 15.367 million, 17.68 million, and 21.365 million were used for calculation, and the wind pressure coefficient at the median of the windward side was extracted and compared. When the mesh size increased from 17.68 million to 21.365 million, the wind pressure coefficient curves basically overlapped, indicating that the 17.68 million mesh size met the mesh independence requirement.

[0084] Next, the calculation parameters were set. Based on the verification results of Example 1, the SSTk-ω turbulence model for shear stress transmission was selected for full-scale simulation of the downburst. The Simple method was used to solve the velocity and pressure fields in a coupled manner, and the momentum equation, turbulent kinetic energy equation, and turbulent dissipation rate equation were discretized using a second-order upwind scheme. The raindrop treatment was the same as in Example 2, and five droplet sizes with diameters of 0.2 mm, 0.6 mm, 1.0 mm, 1.8 mm, and 3.5 mm were selected for simulation.

[0085] Next, the influence of topography on the wind load effect on the structure is analyzed. The surface wind pressure coefficient distribution cloud maps of buildings at the same radial position under different topographical conditions are compared, and the wind pressure coefficient curves of the building midline are extracted and compared.

[0086] When the building's radial distance is 0 times the outflow diameter, it is located directly beneath the downburst. The wind pressure coefficient is positive on every side of the building, with the highest coefficient at the junction of the windward and leeward roofs, gradually decreasing towards the midline, reaching a minimum of 0.975 at the front edge of the windward roof and the rear edge of the leeward roof. The wind pressure coefficient varies less around the perimeter of the building, remaining around 0.98.

[0087] When the radial distance of the building is 0.5 times the outflow diameter, the wind pressure coefficient of the windward side of the building is positive and equal in both types of terrain. The wind pressure coefficient of the windward roof is larger in mountainous terrain than in flat terrain, and the wind pressure coefficient of the leeward roof and leeward side of the building is also larger in mountainous terrain.

[0088] When the building's radial distance is 1.0 times the outflow diameter, the windward side of the building in mountainous terrain experiences positive pressure, which decreases with increasing height, and the value is significantly smaller than that in flat terrain. In flat terrain, the maximum positive pressure appears on the windward side at two-thirds of the height, while significant negative pressure values ​​appear at the front and rear edges of the windward roof. In mountainous terrain, the wind pressure coefficients of the windward and leeward roofs do not change much, remaining around -0.2, and no extreme negative pressure values ​​are observed.

[0089] When the radial distance of a building is 1.5 times the outflow diameter, a large negative pressure value appears at the two edges of the windward roof of the building on flat terrain, with the extreme negative pressure value approaching -1.5. The absolute value of the wind pressure coefficient on the windward side of the building is smaller on mountainous terrain than on flat terrain, while the absolute value of the pressure coefficient on all sides except the leeward side is larger than that on flat terrain.

[0090] When the building's radial distance is 2.0 times the outflow diameter, on flat terrain, only the windward side of the building has a positive wind pressure coefficient, with the maximum negative pressure occurring at the front edge of the windward roof. On mountainous terrain, the windward roof experiences positive pressure due to the downslope winds, while the leeward roof and leeward side exhibit smaller negative pressure.

[0091] When the radial distance of a building is 2.5 times the outflow diameter, the maximum positive wind pressure on the windward side of a building in flat terrain is at two-thirds of its height, while in mountainous terrain, the maximum positive wind pressure occurs at the upper edge of the windward side. The absolute value of the overall pressure coefficient of the windward roof in mountainous terrain is relatively small.

[0092] Next, the rain load effect on the structure is analyzed. The trajectory of raindrops around the building is analyzed. When the building is within the outflow diameter of the downburst, it will be directly impacted by the falling raindrops. Smaller diameter raindrops are more affected by the wind field around the building, and their trajectories are more turbulent, resulting in fewer raindrops directly impacting the building; larger diameter raindrops are less affected by the wind field around the building, and most raindrops directly impact the building surface at a certain angle.

[0093] As the radial position of the building increases, the building will not be affected by large-diameter raindrops. When the building is located at 1.5 times the outflow diameter, small-diameter raindrops are significantly affected by the wind field on the building surface. Only the windward side of the building is affected by raindrops, while other sides are almost unaffected.

[0094] Next, the rain load is calculated. Raindrop information captured on each surface of the building is extracted using computational fluid dynamics software post-processing, including raindrop diameter, raindrop velocity, and the number of raindrops of different diameters. Assuming the raindrops are spherical and the collision time is... The impact force of the raindrop can be calculated using the following formula:

[0095]

[0096] In the formula, The density of raindrops is taken as the density of liquid water, which is 1 kg per cubic meter. The diameter of the raindrop is in millimeters. Let be the final velocity of the raindrops impacting the wall, expressed in meters per second. Based on the raindrop information captured by the wall, calculate the impact force of each raindrop using the formula above, and sum them to obtain the total rain load at that point. Then calculate the average rain pressure using the following formula:

[0097]

[0098] In the formula, Rain load, measured in Newtons; The area is calculated in square meters.

[0099] Next, an equivalent pressure coefficient system is constructed. To compare with the wind pressure coefficient of a building under the influence of a downburst wind field, the concepts of equivalent rainfall pressure coefficient and equivalent total pressure coefficient are introduced, referencing the wind pressure coefficient. The wind pressure coefficient and equivalent rainfall pressure coefficient are calculated separately: Wind pressure coefficient The calculation formula is Equivalent rain pressure coefficient The calculation formula is The equivalent total pressure coefficient is then expressed by the following formula:

[0100]

[0101] In the formula, This is the equivalent total pressure coefficient. The average wind pressure at that point. The impact force of raindrops on that point. To calculate the area, Indicates reference pressure. Indicates air density, For reference speed, the outflow velocity of the blast wave is set at 18 meters per second in this embodiment.

[0102] Meanwhile, to quantify the effect of additional rain load, a wind-rain load ratio coefficient is introduced. It can be expressed by the following formula:

[0103]

[0104] It represents the ratio of the equivalent rain pressure coefficient to the wind pressure coefficient at the same location.

[0105] See Figure 5 , Figure 5 A schematic diagram showing the selection of points for rain pressure calculation. Along the building's midline, five calculation points are selected on each surface to extract rain pressure and the equivalent pressure coefficient.

[0106] Finally, the distribution patterns of equivalent total load under different terrains are analyzed. To study the influence of terrain and rainfall intensity on the load on the building, the equivalent total pressure coefficient curves of the building's median line are presented at six radial positions, under different terrains and rainfall intensities, as shown below. Figures 6 to 11 As shown.

[0107] See Figure 6 , Figure 6The curves show the equivalent total pressure coefficient of the building's median under different rainfall intensities, with the radial distance equal to 0 times the outflow diameter. When the building is directly beneath a downburst, the roof experiences significant raindrop impact, and the equivalent total pressure coefficient increases with increasing rainfall intensity. At a rainfall intensity of 200 mm / h, the equivalent total pressure coefficient reaches 1.28, which is 1.28 times that under no-rain conditions. The equivalent total pressure coefficient of the roof is evenly distributed under different rainfall intensities, but only the areas near the ground on the building's perimeter walls experience significant raindrop impact.

[0108] See Figure 7 , Figure 7 The equivalent total pressure coefficient curves of the building median under different rainfall intensities are shown, with a radial distance of 0.5 times the outflow diameter. Figure 7 'a' represents flat terrain. Figure 7 b represents mountainous terrain. When the radial distance of the building is 0.5 times the outflow diameter, regardless of whether the terrain is flat or mountainous, the windward side, windward roof, and leeward roof of the building are all subject to significant additional rain loads, with the windward roof experiencing the most pronounced additional rain load. The influence of mountainous terrain on the rain load on the building is relatively small.

[0109] See Figure 8 , Figure 8 The equivalent total pressure coefficient curves of the building median under different rainfall intensities are shown, with a radial distance of 1.0 times the outflow diameter. Figure 8 'a' represents flat terrain. Figure 8 b represents mountainous terrain. When a building is located at a radial distance of 1.0 times the outflow diameter, the windward side of the building experiences a significant additional rain load in mountainous terrain. With a rainfall intensity of 200 mm / h, the maximum equivalent total pressure coefficient reaches 1.25, approximately 1.22 times that of the same location without rain. However, in mountainous terrain, the additional rain load on the building is relatively small. The maximum equivalent total pressure coefficient occurs at the bottom of the windward side and decreases with increasing height, while the top of the windward side is almost unaffected by the additional rain load.

[0110] See Figures 9 to 11 , Figure 9 The equivalent total pressure coefficient curves of the building median under different rainfall intensities are shown, with a radial distance of 1.5 times the outflow diameter. Figure 9 'a' represents flat terrain. Figure 9 b represents mountainous terrain; Figure 10 The radial distance is 2.0 times the outflow diameter, where Figure 10 'a' represents flat terrain. Figure 10 b represents mountainous terrain; Figure 11 The radial distance is 2.5 times the outflow diameter, where Figure 11 'a' represents flat terrain. Figure 11b represents mountainous terrain. When the building is positioned at 1.5, 2.0, and 2.5 times the outflow diameter, the maximum equivalent total pressure coefficient on the windward side of the building in flat terrain is approximately 1.2 times that in the same location without rain. However, in mountainous terrain, the equivalent total pressure coefficient curves under different rainfall intensities almost completely overlap, indicating that the building is almost unaffected by additional rain loads. Overall, the wind-rain coupling effect on the building increases with increasing rainfall intensity, and the trend of increasing equivalent total pressure coefficient with increasing rainfall intensity is more pronounced in flat terrain than in mountainous terrain.

[0111] Example 4: Influence of radial distance on rain load effect and quantitative analysis of wind-rain load ratio coefficient

[0112] Based on the equivalent pressure coefficient calculation results of Example 3, this embodiment further analyzes the distribution law of additional rain load at different radial positions of the building, focusing on the wind-rain load ratio coefficient. The proportion of rain load contribution revealed.

[0113] Under extreme conditions with a rainfall intensity of 200 mm / hour, the wind-rain load ratio coefficients at six radial locations of buildings on flat terrain were calculated. Compare the value curves. See [link / reference] Figure 12 , Figure 12 The curve shows the wind-rain load ratio distribution of a building under the action of a downburst on flat ground, with a rainfall intensity of 200 mm / hour.

[0114] On the windward side, the largest The values ​​all appear at the bottom, and increase with height. The value gradually decreases. As the radial distance increases, the value of the windward side... The value shows a trend of first increasing and then decreasing. When the radial distance of the building is 0 times the outflow diameter, the windward side of the building is almost unaffected by the additional rain load. As the radial distance increases, the additional rain load on the windward side of the building gradually increases. When the radial distance of the building is 1.0 times the outflow diameter, the windward side... Maximum value, maximum The value reached 22.5%. As the radial distance continued to increase, the windward side... The value gradually decreases. When the building is located radially at 2.5 times the outflow diameter, the windward side... The value drops to its lowest point, and the windward side is at its maximum. The value is 4%.

[0115] When the building is within the outflow diameter of the downburst, the roof The value decreases as the radial distance increases. Specifically, when the building is located directly in the center of the downburst, the roof... The value reaches a maximum of 28%. When the building is within the horizontal spread range of the downburst, the roof is almost unaffected by rain load. At different radial locations, the leeward side of the building is unaffected by rain load.

[0116] For the largest of the entire building The location where the value appears can be summarized as follows: when the building is within the outflow diameter of the downburst, the building's maximum value... The value appears at the junction of the windward and leeward roofs; the maximum value of the building is when it is within the horizontal spread range of a downburst. The value appears at the bottom of the windward side.

[0117] See Figure 13 , Figure 13 The graph shows the wind-rain load ratio distribution curve for a building under the influence of a downburst storm in a mountainous area, with a rainfall intensity of 200 mm / h. When the building is directly below the downburst storm, only the area near the ground on the windward side experiences a significant additional rain load. When the radial distance of the building is greater than or equal to 0.5 times the outflow diameter, the windward side... The value decreases as the radial distance increases. When the building is located at a radial distance of 0.5 times the outflow diameter (i.e., at the foot of the windward slope), the value on the windward side... Maximum value, maximum The value is 16%. When a building is located on a windward slope, the maximum windward side... The value is 12%. When a building is located on a mountaintop, the bottom of the windward side still experiences a significant impact from raindrops, with a maximum... The value is 4%. When a building is on the leeward side of a mountain, the windward side is almost unaffected by raindrops. Regarding the raindrop impact on the roof, the building experiences raindrop impact not only when it is within the outflow diameter of the downburst, but also when it is located on the leeward side of a mountain, although the impact force is smaller. The value is only 1%.

[0118] The above The value analysis results can be used to identify key parts of the building surface that are greatly affected by wind and rain, and provide quantitative basis for local reinforcement design of locations such as the bottom of the windward side, the junction of the roof, the eaves and corner areas.

[0119] Example 5: System Implementation

[0120] The method for determining the equivalent pressure coefficient of the present invention can be implemented by a software system. The system includes: one or more processors; and a memory storing instructions executable by the one or more processors; the instructions are executed by the one or more processors to cause the system to implement the method described in Embodiments 1 to 4.

[0121] The core solution module of this system encapsulates the computational fluid dynamics and discrete phase model solution processes described in Examples 1 to 4, automatically calling commercial or open-source solvers for calculations. This module integrates specific turbulence model settings, a two-way coupling algorithm, and post-processing data extraction scripts. It can automatically calculate the wind pressure coefficient, equivalent rainfall pressure coefficient, equivalent total pressure coefficient, and wind-rain load ratio coefficient at each monitoring point, and generate load distribution cloud maps and curves (such as...). Figures 6 to 13 ), and a structured report containing key coefficient values.

[0122] The system can be deployed on high-performance computing servers, local workstations, or cloud computing platforms, and users can operate it through a client or web interface.

[0123] Example 6: Computer-readable storage medium

[0124] This embodiment provides a computer-readable storage medium storing a computer program thereon. When executed by a processor, the computer program implements the methods described in Embodiments 1 to 4. The storage medium may be a disk, optical disk, solid-state drive, read-only memory, or random access memory, etc.

[0125] The methods, systems, devices, and media described in this invention can be widely applied to wind-resistant design of building structures in mountainous terrain, especially low-rise buildings and large-span roofs, which are sensitive to wind loads. This invention can more accurately predict wind-rain coupled loads, providing a reliable basis for structural design and possessing significant engineering application value and market prospects.

Claims

1. A method for determining the equivalent pressure coefficient of buildings under thunderstorms and strong winds that drive rain in mountainous terrain, characterized in that, Includes the following steps: A coupled numerical field of thunderstorm downburst wind and rain, including a mountain terrain model and a building model, is established. The movement of raindrops of different sizes in the wind field of the mountain terrain is simulated by a discrete phase model, and whether the raindrops undergo cross-mountain movement across the ridge is identified. Based on the aforementioned wind-rain coupling numerical field, the wind pressure coefficient at specific locations on the building surface was calculated. and equivalent rain pressure coefficient The equivalent rain pressure coefficient The calculations differentiated between impact loads generated by raindrops that had undergone mountain-crossing motion and those that had not. According to the formula Calculate the equivalent total pressure coefficient at the location; Building load assessment is performed based on the aforementioned equivalent total pressure coefficient.

2. The method for determining the equivalent pressure coefficient of buildings under thunderstorms and strong winds in mountainous terrain according to claim 1, characterized in that, The mountain terrain model adopts a cosine mountain model, and its terrain function expression is as follows: ； in, The height of any point on the mountain. The height of the mountaintop. The horizontal distance between the mountaintop and the mountainside. , This is the mountain shape coefficient; for axisymmetric mountains, The value is 1.

3. The method for determining the equivalent pressure coefficient of buildings under thunderstorms and strong winds in mountainous terrain according to claim 1, characterized in that, The step of identifying whether raindrops have undergone "mountain-crossing movement" includes: tracking the trajectory of raindrops released from the windward side of the mountain; if the elevation of the highest point of the trajectory is greater than or equal to the elevation of the ridgeline, then the raindrop is determined to have undergone mountain-crossing movement; and obtaining the distances of raindrops of different particle sizes from different outflow centers through numerical simulation. The proportion of mountain crossing movements, among which, It is the horizontal distance between the center of the thunderstorm outflow and the foot of the windward mountain.

4. The method for determining the equivalent pressure coefficient of buildings under thunderstorm strong winds and rain-driving in mountainous terrain according to claim 3, characterized in that, when At that time, raindrops with a diameter of 1.0 mm undergo a mountain-crossing motion; when At that time, only raindrops with a diameter of 0.6 mm or less undergo the movement across the mountain; when At that time, only raindrops with a diameter of no more than 0.2 mm underwent the movement across the mountain; among them, The diameter of the outflow from the impact burst.

5. The method for determining the equivalent pressure coefficient of buildings under thunderstorms and strong winds in mountainous terrain according to claim 1, characterized in that, The equivalent rain pressure coefficient In the calculation, the raindrop impact load caused by the mountain crossing movement and acting on the leeward side of the building is included separately, which is different from the raindrop impact load that does not involve mountain crossing movement and only acts on the windward side and roof.

6. The method for determining the equivalent pressure coefficient of buildings under thunderstorms and strong winds in mountainous terrain according to claim 1, characterized in that, The wind pressure coefficient The calculation formula is: The equivalent rain pressure coefficient The calculation formula is: ,in This refers to the wind pressure value at a specific location on the building surface. The total impact force generated by raindrops that have undergone mountain-crossing motion and those that have not. For the area of ​​force application, For reference pressure, air density, For reference wind speed.

7. The method for determining the equivalent pressure coefficient of buildings under thunderstorm strong winds and rain-driving in mountainous terrain according to claim 6, characterized in that, The formula for calculating the average rainfall pressure is: ； in, For rain load, To calculate the area; The rain load Calculated based on the formula for raindrop impact force: ； in, The density of water, The diameter of the raindrop. The final velocity of the raindrop when it hits the wall, and the collision time. .

8. The method for determining the equivalent pressure coefficient of buildings under thunderstorm strong winds and rain-driving in mountainous terrain according to claim 1, characterized in that, It also includes calculating the wind-rain load ratio coefficient. Steps: ； in, The coefficient is the wind pressure coefficient; Used to quantify the contribution of rain load to the total load and to identify load-sensitive areas on building surfaces.

9. The method for determining the equivalent pressure coefficient of buildings under thunderstorm strong winds and rain-driving in mountainous terrain according to claim 1, characterized in that, The method is applicable to different radial positions of buildings in mountain wind fields. Implemented separately, the radial position includes at least directly below the downburst. At the foot of the windward mountain Windward mountainside Mountain Top leeward mountainside and the foot of the leeward mountain .

10. A system for determining the equivalent pressure coefficient of buildings under thunderstorms and strong winds that drive rain in mountainous terrain, characterized in that, include: One or more processors; The memory stores instructions that can be executed by the one or more processors; The instructions are executed by the one or more processors to cause the system to implement the method as described in any one of claims 1 to 9.

11. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method as described in any one of claims 1 to 9.

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