Calculation Method for Segmented Discontinuous Solar Temperature Gradient of Enclosed Stacked Box Aqueduct

Abstract

This invention provides a method for calculating segmented discontinuous solar radiation temperature gradients in enclosed stacked aqueducts, relating to the field of aqueduct technology. The method divides the inner cavity of the enclosed stacked aqueduct into a gas-phase coupled heat transfer zone, a gas-liquid phase interface zone, and a fluid heat source anchoring zone based on water level height, constructing a thermo-solid coupled heat transfer model that distinguishes the properties of the media. Through this partitioning, the heat exchange characteristics of different regions can be accurately matched, establishing a segmented discontinuous solar radiation temperature gradient kernel function along the height coordinate. Based on the thermo-solid coupled heat transfer model that distinguishes the properties of the media, the discontinuous solar radiation temperature gradient kernel function is used as a boundary driving source, substituted into the transient nonlinear heat conduction partial differential equation for iterative solution, outputting a discontinuous solar radiation temperature gradient curve containing abrupt step characteristics at the water surface line. This method solves the problem of inaccurate calculation of solar radiation temperature gradients in enclosed stacked aqueducts and is applicable to the calculation of solar radiation temperature gradients in enclosed stacked aqueducts.

Description

Technical Field

[0001] This invention relates to the field of aqueduct technology, and in particular to a method for calculating the segmented discontinuous solar radiation temperature gradient of a closed stacked box aqueduct. Background Technology

[0002] In modern hydraulic and bridge engineering structural design, stress calculations based on solar radiation temperature gradients are essential for large box girder structures (such as box girders and stacked box aqueducts). Traditional engineering standards (such as China's "General Specifications for Design of Highway Bridges and Culverts" JTGD60-2015 and New Zealand's Bridge Standard TNZ) typically use a single continuous multi-segment broken line or a continuous exponential decay curve to describe the temperature gradient distribution along the vertical (Y-axis) of the cross-section. Traditional calculation models input the local highest extreme air temperature and the temperature difference between the structural foundation, and calculate the cross-sectional temperature at different elevations of the structure using a continuous function.

[0003] Traditional continuous temperature gradient models suffer from serious theoretical flaws and applicability issues when applied to closed-cell aqueducts (i.e., complex box-shaped structures containing enclosed air cavities and flowing water), primarily manifested in the following ways:

[0004] The greenhouse effect of the air cavity was ignored: Traditional models assume that the temperature decreases uniformly or exponentially with depth, but there is a closed air cavity below the top plate of the stacked box aqueduct. After the solar heat enters, it generates heat accumulation in the air cavity (greenhouse effect), which causes the temperature in the upper part of the web (air cavity section) to drop extremely slowly, or even remain constant. Traditional models cannot accurately simulate the high temperature maintenance phenomenon in this section.

[0005] The stress abrupt changes at the water-air interface were ignored: the flowing water inside the stacked aqueduct has great thermal inertia and forced convection characteristics, and the water temperature is relatively constant (anchoring effect). At the air-water interface inside the structure, the temperature is not only discontinuous, but also experiences a violent instantaneous temperature jump. Traditional continuous curves force a smooth transition, completely omitting the concentrated tensile / compressive stress abrupt changes that are highly likely to induce structural cracking at this point.

[0006] The stress jumps between the flowing water and the top surface of the lower air chamber were ignored: the regulating water inside the stacked aqueduct has great thermal inertia and forced convection characteristics, and the water temperature is relatively constant (anchoring effect). The lower air chamber region circulates with air, and the temperature of the lower air chamber remains relatively constant. At the top surface of the lower air chamber, the temperature is not only discontinuous, but also experiences a violent instantaneous temperature jump. Traditional continuous curves force a smooth transition, completely omitting the concentrated tensile / compressive stress abrupt change that is highly likely to induce structural cracking at this point.

[0007] Lack of regional and structural specificity: The lack of a quantitative reduction system for different solar radiation characteristics and additional insulation layer (such as EPS / XPS) thickness leads to blind value selection in engineering design.

[0008] The sudden cooling (negative gradient) control condition was not properly quantified: cold waves or sudden rain caused the outer surface to cool suddenly, but the large volume of water inside remained warm (cold outside, warm inside). Traditional negative gradient calculations failed to reflect the reverse tensile damage effect of the water body as a thermal axis on the cold surface concrete (this is the main cause of horizontal cracks in saddle-shaped concrete slabs).

[0009] The computational cost is too high: To accurately obtain the above-mentioned complex temperature field, the only current method is to perform complex and time-consuming fluid-solid-fluid thermodynamic coupling (CFD) simulation on the entire bridge. This cannot meet the needs of front-line engineering designers for daily rapid verification and standardized design. Summary of the Invention

[0010] The technical problem solved by this invention: This invention provides a method for calculating the segmented discontinuous solar radiation temperature gradient of a closed stacked box aqueduct, which solves the problem of inaccurate calculation of the solar radiation temperature gradient of a closed stacked box aqueduct.

[0011] The technical solution adopted by this invention to solve the above-mentioned technical problems is: a method for calculating the segmented discontinuous solar radiation temperature gradient of a closed stacked box aqueduct, wherein the closed stacked box aqueduct includes a top plate area, a water-passing inner cavity, and a lower air cavity area, and the method includes the following steps:

[0012] S1. Obtain the three-dimensional structure of the closed stacked box aqueduct and construct a three-dimensional analysis model;

[0013] S2. Based on the three-dimensional analysis model, according to the water level, the water passage cavity of the closed stacked box aqueduct is divided into a gas-phase coupling heat transfer zone, a gas-liquid phase interface zone, and a fluid heat source anchoring zone along the height from high to low, and a thermo-solid coupling heat transfer model that distinguishes the properties of the medium is constructed.

[0014] S3. Under the heating condition, determine the top surface temperature of the closed stacked box aqueduct, calculate the top edge temperature of the gas-phase coupling heat exchange zone, quantify the greenhouse effect of the inner cavity, obtain the temperature of the gas-phase coupling heat exchange zone, quantify the fluid anchoring effect, obtain the temperature of the fluid heat source anchoring zone, quantify the atmospheric temperature, and obtain the temperature of the lower gas cavity region.

[0015] S4. For the stacked aqueduct structure corresponding to the gas-phase coupling heat exchange zone, an exponential decay function or a polynomial function is used to describe the temperature change from the surface to the interior caused by solar radiation. For the stacked aqueduct structure corresponding to the fluid heat source anchoring zone, a linear smooth function is used to describe the uniform temperature gradient protected by fluid anchoring. For the stacked aqueduct structure corresponding to the lower air cavity zone, a linear smooth function is used to describe the temperature gradient of the lower air cavity zone. The Sigmoid family step smoothing operator is used to bridge the temperature change of the stacked aqueduct structure corresponding to the gas-phase coupling heat exchange zone and the uniform temperature gradient of the stacked aqueduct structure corresponding to the fluid heat source anchoring zone, thereby achieving the bridging of the uniform temperature gradient on the top surface of the lower air cavity zone and obtaining the segmented discontinuous solar radiation temperature gradient kernel function along the height coordinate.

[0016] S5. Based on the thermo-solid coupled heat transfer model that distinguishes the properties of the medium, the discontinuous solar radiation temperature gradient kernel function is used as the boundary driving source. The temperature of the top plate area, the temperature of the gas-phase coupled heat transfer area, the temperature of the fluid heat source anchoring area and the temperature of the lower air cavity area are used as boundary conditions. The transient nonlinear heat conduction partial differential equation is substituted into the equation for iterative solution. The transient evolution temperature field of the stacked box aqueduct section along the height direction is extracted, and the discontinuous solar radiation temperature gradient curve containing the abrupt step characteristics at the water surface line is output.

[0017] Furthermore, in S2, a gas-liquid transition bandwidth threshold is set, denoted as... The height of the water level is recorded as The height is recorded as ,when At that time, the current altitude is in the gas-phase coupled heat transfer zone. At that time, the current altitude is in the gas-liquid phase interface region. At that time, the current altitude is within the fluid heat source anchoring zone.

[0018] Furthermore, in S3, the formula for calculating the top surface temperature of the top plate of the closed stacked box aqueduct is as follows: ,in, This indicates the temperature of the top surface of the roof slab. Indicates standard temperature. This represents the correction factor for the sunshine area. This indicates the reduction factor for the insulation board.

[0019] Furthermore, in S3, the formula for calculating the top edge temperature of the gas-phase coupled heat exchange zone is: , This indicates the temperature of the top surface of the roof slab. Represents the natural constant. This represents the combined attenuation constant of the concrete material and the cavity interface. The thickness of the top plate. This indicates the temperature at the top edge of the gas-phase coupled heat exchange zone.

[0020] Furthermore, in S3, the formula for calculating the temperature of the gas-phase coupled heat exchange zone is: ,in, This indicates the temperature of the gas-phase coupled heat exchange zone. This indicates the temperature at the top edge of the gas-phase coupled heat exchange zone. This represents the greenhouse compensation value.

[0021] Furthermore, in S3, the formula for calculating the temperature of the fluid heat source anchoring zone is as follows: , This indicates the temperature of the fluid heat source anchoring zone, which dynamically anchors the temperature of the inner wall of the submerged section of the stacked aqueduct to the fluid temperature. ,in, Indicates the temperature of the water. This represents the jump amplitude; the formula for calculating the temperature of the lower air cavity region is: , This indicates the temperature of the lower air chamber. This represents the atmospheric temperature, ensuring that the temperature of the lower air cavity region equals the atmospheric temperature.

[0022] Furthermore, in S4, the kernel function for the discontinuous solar radiation temperature gradient segmented along the height coordinate is: ;in, The kernel function represents the discontinuous solar radiation temperature gradient segmented along the height coordinate. This represents the isothermal gradient function of the stacked box aqueduct corresponding to the lower air cavity region. T2 represents the uniform temperature gradient function of the stacked aqueduct structure corresponding to the fluid heat source anchoring zone, which is protected by fluid anchoring. This represents the temperature change function from the surface to the interior of the stacked box aqueduct structure corresponding to the gas-phase coupled heat exchange zone caused by solar radiation. This represents the temperature change function at the top of the stacked box aqueduct structure caused by sunlight. This represents the Sigmoid family of step smoothing operators. ; i takes 1, 2, 3, Indicates the current position relative to At height, This represents the step steepness control coefficient. The value of is negatively correlated with the meniscus thickness caused by the surface tension of liquid and gas at the interface and the capillary climb height of the concrete. Indicates altitude, Indicates the height of the top surface of the lower air cavity region. Indicates the height of the waterline. This indicates the height of the bottom surface of the top plate.

[0023] Furthermore, in S5, the expression for the transient nonlinear heat conduction partial differential equation is: ;in, This indicates the density of concrete. Indicates specific heat capacity. Indicates the rate of temperature change. express Thermal conductivity in the direction of Indicates temperature at Rate of change of direction express Thermal conductivity in the direction of Indicates temperature at Rate of change of direction express Thermal conductivity in the direction of Indicates temperature at Rate of change of direction This indicates the internal heat source of the concrete.

[0024] Furthermore, the method also includes: using the discontinuous solar radiation temperature gradient curve containing the abrupt step characteristics at the water surface line and the top surface of the lower air cavity as a boundary load, mapping it into the static solver for thermodynamic coupling analysis; identifying the strong shear shear and out-of-plane bending secondary stress peaks at the interface between the upper hot and lower cold caused by fluid anchoring, and automatically adding anti-crack structural steel strands at the horizontal intersection position of the stacked box web according to the peak value vector of the secondary stress peak.

[0025] Furthermore, the method also includes: under cold wave cooling conditions, reversibly assigning feature point values ​​to the thermo-solid coupled heat transfer model that distinguishes medium properties, wherein the feature point values ​​include: setting the top surface temperature as the extreme cold temperature, and the extreme cold temperature as... , This indicates the temperature of the top surface of the top plate, and the temperature of the gas-phase coupling heat exchange zone is set to... , This represents the temperature at the top edge of the gas-phase coupled heat exchange zone, and the temperature of the fluid heat source anchoring zone is set to... Temperature of the lower air chamber Therefore, it is necessary to verify whether the sudden increase in horizontal tensile stress meets the design threshold. If it does not, the location of the sudden increase in horizontal tensile stress is the risk point for cracking.

[0026] The beneficial effects of this invention are as follows: This invention provides a method for calculating the segmented discontinuous solar radiation temperature gradient of a closed stacked aqueduct. The method divides the inner cavity of the closed stacked aqueduct into a gas-phase coupling heat transfer zone, a gas-liquid phase interface zone, and a fluid heat source anchoring zone based on the water level. Other areas of the aqueduct include a top plate zone and a lower air cavity zone. A thermo-solid coupling heat transfer model that distinguishes the properties of the media is constructed. A kernel function for the segmented discontinuous solar radiation temperature gradient along the height coordinate is established. The top surface temperature of the closed stacked aqueduct is determined, and the top edge temperature of the gas-phase coupling heat transfer zone is calculated. The greenhouse effect, fluid anchoring effect, and lower air cavity temperature effect are quantified, and the top plate temperature and gas phase temperature are obtained. The temperature of the coupled heat exchange zone, the temperature of the fluid heat source anchoring zone, and the temperature of the lower air cavity zone are used. Based on the thermo-solid coupled heat transfer model that distinguishes the properties of the medium, the kernel function of the discontinuous solar radiation temperature gradient is used as the boundary driving source. The temperature of the top plate, the temperature of the gas-phase coupled heat exchange zone, the temperature of the fluid heat source anchoring zone, and the temperature of the lower air cavity zone are used as boundary conditions. The transient nonlinear heat conduction partial differential equation is substituted into the equation for iterative solution. The transient evolution temperature field along the height direction of the cross section of the stacked box aqueduct is extracted, and the discontinuous solar radiation temperature gradient curve containing the abrupt step characteristics at the water surface line is output. This solves the problem of inaccurate calculation of solar radiation temperature gradient for closed stacked box aqueducts.

[0027] Compared with existing continuous temperature gradient models, this invention has the following advantages:

[0028] 1. Accurate simulation of complex thermal effects: By distinguishing the gas-phase coupled heat exchange zone, gas-liquid phase interface zone, fluid heat source anchoring zone, top plate zone and lower air cavity zone, it effectively captures the greenhouse effect of closed air cavity and the anchoring effect of flowing water, accurately reproduces the temperature step characteristics of gas-water interface and the top surface of lower air cavity, and solves the core problem that traditional continuous temperature gradient models cannot reflect discontinuous temperature distribution.

[0029] 2. Enhance the relevance and rationality of the design: Introduce the correction coefficient for the sunshine area and the reduction coefficient for the insulation board, and establish a quantitative reduction system for different sunshine areas and insulation structures to avoid blind design values; at the same time, by applying the extreme cold temperature conditions in reverse, quantify the risk of horizontal tensile stress under negative gradients, and effectively prevent horizontal cracks in key parts such as saddle plates.

[0030] 3. Reduced computational costs and improved efficiency: It eliminates the need for complex and time-consuming fluid-structure interaction CFD simulations. By iteratively solving piecewise discontinuous temperature gradient kernel functions and transient heat conduction equations, it enables rapid acquisition of transient evolution temperature fields, meeting the daily needs of front-line engineering designers for rapid verification and standardized design.

[0031] 4. Guiding the optimization of structural crack prevention: By identifying stress peaks at the gas-water interface through thermodynamic coupling analysis, a precise basis is provided for adding crack-prevention steel strands at the horizontal junction of the stacked box aqueduct web, which significantly improves the crack resistance and long-term durability of the closed stacked box aqueduct structure. Attached Figure Description

[0032] Figure 1 This is a flowchart illustrating a method for calculating segmented discontinuous solar radiation temperature gradients in a closed stacked box aqueduct provided by the present invention.

[0033] Figure 2 This is a schematic diagram of a closed stacked aqueduct structure provided by the present invention, wherein 1 represents the gas-phase coupling heat exchange zone, 2 represents the liquid surface corresponding to the water level, 3 represents the fluid heat source anchoring zone, 4 represents the lower air cavity, and 5 represents the concrete structure.

[0034] Figure 3 This is a diagram showing the temperature and elevation relationship of a closed-type stacked box aqueduct structure provided by the present invention; wherein, Indicates the top surface temperature. This indicates the temperature at the top edge of the gas-phase coupled heat exchange zone. Indicates the temperature of the water. H (height of section) represents atmospheric temperature, T (temperature) represents cross-sectional height, and H (temperature) represents ambient temperature. This indicates the top surface temperature under cold wave cooling conditions. This indicates the top edge temperature of the gas-phase coupled heat exchange zone under cold wave cooling conditions. Detailed Implementation

[0035] This invention addresses the problem of inaccurate calculation of solar radiation temperature gradient in enclosed stacked box aqueducts by providing a method for calculating segmented discontinuous solar radiation temperature gradient in such aqueducts. The enclosed stacked box aqueduct includes a top plate area, a water-passing cavity, and a lower air cavity area. The method is as follows: Figure 1 As shown, it includes the following steps:

[0036] S1. Obtain the three-dimensional structure of the closed stacked box aqueduct and construct a three-dimensional analysis model.

[0037] Specifically, the three-dimensional analysis model includes the spatial geometric cross-sectional parameters of the closed stacked box aqueduct, the thermal parameters of the materials, and dynamic gas-phase hydrological data, including water level, ambient temperature, solar radiation intensity, and wind speed.

[0038] S2. Based on the three-dimensional analysis model, according to the water level, the inner cavity of the closed stacked box aqueduct is divided into a gas-phase coupling heat transfer zone, a gas-liquid phase interface zone, and a fluid heat source anchoring zone along the height from high to low, and a thermo-solid coupling heat transfer model that distinguishes the properties of the medium is constructed.

[0039] Specifically, a threshold for the gas-liquid transition bandwidth is set, denoted as... The height of the water level is recorded as The height is recorded as ,when At that time, the current altitude is in the gas-phase coupled heat transfer zone. At that time, the current altitude is in the gas-liquid phase interface region. At this point, the current altitude is within the fluid heat source anchoring zone. Through zoning, the heat exchange characteristics of different areas can be precisely matched. The gas-phase coupling heat exchange zone corresponds to the enclosed cavity above the water surface, where heat from the top plate creates a greenhouse effect. The gas-liquid phase interface zone exhibits temperature step characteristics. The fluid heat source anchoring zone corresponds to the submerged area below the water surface, utilizing the large heat capacity and stable temperature of water to achieve temperature anchoring, effectively distinguishing the heat conduction patterns of different media. Based on these zoning, the enclosed stacked aqueduct includes a top plate zone, a gas-phase coupling heat exchange zone, a gas-liquid phase interface zone, a fluid heat source anchoring zone, and a lower gas cavity zone.

[0040] S3. Under the heating condition, determine the top surface temperature of the closed stacked box aqueduct, calculate the top edge temperature of the gas-phase coupling heat exchange zone, quantify the greenhouse effect of the inner cavity, obtain the temperature of the gas-phase coupling heat exchange zone, quantify the fluid anchoring effect, obtain the temperature of the fluid heat source anchoring zone, quantify the atmospheric temperature, and obtain the temperature of the lower gas cavity region.

[0041] Specifically, the formula for calculating the top surface temperature of a closed stacked box aqueduct is as follows: ,in, Indicates the top surface temperature. This indicates the standard temperature, which is typically 25 degrees Celsius. This represents the correction factor for sunshine area. The correction factor for sunshine area in high-radiation areas ranges from 1.1 to 1.2, the correction factor for sunshine area in standard areas ranges from 1.0, and the correction factor for sunshine area in low-radiation areas ranges from 0.8 to 0.9. This represents the reduction factor for the insulation board. When there is no insulation board, the reduction factor is 1.0. When there is an insulation layer, the thickness of the insulation board is assumed to be... centimeters, when d is greater than 3, When d is not greater than 3, It is 0.7.

[0042] The formula for calculating the top edge temperature of the gas-phase coupled heat exchange zone is: , This indicates the temperature of the top surface of the roof slab. Represents the natural constant. This represents the combined attenuation constant of the concrete material and the cavity interface. The thickness of the top plate. This indicates the temperature at the top edge of the gas-phase coupled heat exchange zone. The value ranges from 2 to 3, which ensures that, given a top plate thickness of 0.5 meters, Approximately One-third of it.

[0043] The formula for calculating the temperature of the gas-phase coupled heat exchange zone is: ,in, This indicates the temperature of the gas-phase coupled heat exchange zone, i.e., the temperature of the enclosed cavity above the water surface. This indicates the temperature at the top edge of the gas-phase coupled heat exchange zone. This represents the greenhouse compensation value, for the purpose of simplifying calculations. It can be approximated as equal to Temperature uniformity across the cross-section of the gas-phase coupled heat exchange zone.

[0044] The formula for calculating the temperature of the fluid heat source anchoring zone is as follows: , This indicates the temperature of the fluid heat source anchoring zone, which dynamically anchors the temperature of the inner wall of the submerged section of the stacked aqueduct to the fluid temperature. ,in, Indicates the temperature of the water. This indicates the jump amplitude, i.e., the temperature jump in the gas-liquid phase interface region.

[0045] The formula for calculating the temperature of the lower air cavity region is: , This indicates the temperature of the lower air chamber. It indicates atmospheric temperature.

[0046] S4. For the stacked aqueduct structure corresponding to the gas-phase coupling heat exchange zone, an exponential decay function or a polynomial function is used to describe the temperature change from the surface to the interior caused by solar radiation; for the stacked aqueduct structure corresponding to the fluid heat source anchoring zone, a linear smooth function is used to describe the temperature gradient protected by fluid anchoring; for the stacked aqueduct structure corresponding to the lower air cavity zone, a linear smooth function is used to describe the temperature gradient of the lower air cavity zone; using the Sigmoid family step smoothing operator, the temperature change of the stacked aqueduct structure corresponding to the gas-phase coupling heat exchange zone and the uniform temperature gradient of the stacked aqueduct structure corresponding to the fluid heat source anchoring zone are bridged to achieve the uniform temperature gradient bridging of the top surface of the lower air cavity zone, thus obtaining the segmented discontinuous solar radiation temperature gradient kernel function along the height coordinate;

[0047] Specifically, the kernel function for the discontinuous solar radiation temperature gradient along the height coordinates for the temperature of the top plate area, the temperature of the gas-phase coupled heat exchange zone, the temperature of the fluid heat source anchoring zone, and the temperature of the lower air cavity area is as follows: ;in, The kernel function represents the discontinuous solar radiation temperature gradient segmented along the height coordinate. This represents the isothermal gradient function of the stacked box aqueduct corresponding to the lower air cavity region. T2 represents the uniform temperature gradient function of the stacked aqueduct structure corresponding to the fluid heat source anchoring zone, which is protected by fluid anchoring. This represents the temperature change function from the surface to the interior of the stacked box aqueduct structure corresponding to the gas-phase coupled heat exchange zone caused by solar radiation. This represents the temperature change function at the top of the stacked box aqueduct structure caused by sunlight. This represents the Sigmoid family of step smoothing operators. ; i takes 1, 2, 3, Indicates the current position relative to At height, This represents the step steepness control coefficient. The value of is negatively correlated with the meniscus thickness caused by the surface tension of liquid and gas at the interface and the capillary climb height of the concrete. Indicates altitude, Indicates the height of the top surface of the lower air cavity region. Indicates the height of the waterline. This indicates the height of the bottom surface of the top plate.

[0048] S5. Based on the thermo-solid coupled heat transfer model that distinguishes the properties of the medium, the discontinuous solar radiation temperature gradient kernel function is used as the boundary driving source. The temperature of the top plate area, the temperature of the gas-phase coupled heat transfer area, the temperature of the fluid heat source anchoring area and the temperature of the lower air cavity area are used as boundary conditions. The transient nonlinear heat conduction partial differential equation is substituted into the equation for iterative solution. The transient evolution temperature field of the stacked box aqueduct section along the height direction is extracted, and the discontinuous solar radiation temperature gradient curve containing the abrupt step characteristics at the water surface line is output.

[0049] Specifically, the expression for the transient nonlinear heat conduction partial differential equation is: ;in, This indicates the density of concrete. Indicates specific heat capacity. Indicates the rate of temperature change. express Thermal conductivity in the direction of Indicates temperature at Rate of change of direction express Thermal conductivity in the direction of Indicates temperature at Rate of change of direction express Thermal conductivity in the direction of Indicates temperature at Rate of change of direction This represents the internal heat sources of concrete, including those from solar radiation penetration and early cement hydration. The initial conditions and heat transfer boundary conditions of the transient nonlinear heat conduction partial differential equation are driven in real time by the piecewise discontinuous solar radiation temperature gradient kernel function. Iterative solutions are obtained using finite element software such as ANSYS and ABAQUS. This approach eliminates the need for complex and time-consuming fluid-structure interaction (CFD) simulations. By iteratively solving the piecewise discontinuous temperature gradient kernel function and the transient heat conduction equation, it enables rapid acquisition of the transient temperature field, meeting the daily needs of frontline engineers for rapid verification and standardized design.

[0050] Furthermore, the method also includes: using the discontinuous solar radiation temperature gradient curve containing the abrupt step characteristics at the water surface line and the top surface of the lower air cavity as a boundary load, mapping it into the static solver for thermodynamic coupling analysis; identifying the strong shear shear and out-of-plane bending secondary stress peaks at the interface between the upper hot and lower cold caused by fluid anchoring, and automatically adding anti-crack structural steel strands at the horizontal intersection position of the stacked box web according to the peak value vector of the secondary stress peak.

[0051] Furthermore, the method also includes: under cold wave cooling conditions, reversibly assigning feature point values ​​to the thermo-solid coupled heat transfer model that distinguishes medium properties, wherein the feature point values ​​include: setting the top surface temperature as the extreme cold temperature, and the extreme cold temperature as... , This indicates the temperature of the top surface of the roof plate under cooling conditions, with the temperature of the gas-phase coupling heat exchange zone set as follows: , This indicates the temperature at the top edge of the gas-phase coupled heat exchange zone under cooling conditions, and the temperature of the fluid heat source anchoring zone is set to... Temperature of the lower air chamber This process verifies whether the sudden increase in horizontal tensile stress meets the design threshold. If not, the location of the sudden increase in horizontal tensile stress is the risk point for cracking. This effectively prevents horizontal cracks in critical components such as the saddle plate.

[0052] Example:

[0053] A closed stacked box aqueduct structure, such as Figure 2 As shown, the structure includes a concrete structure 5, a gas-phase coupled heat exchange zone 1, a liquid surface 2 corresponding to the water level, a fluid heat source anchoring zone 4, and a lower air chamber 4. The lower air chamber 4 is equipped with vents (not shown in the figure) to ensure that the temperature of the lower air chamber is consistent with the ambient background temperature. The temperature curves corresponding to its boundary conditions are shown below. Figure 3 As shown, it includes the boundary temperatures under the warming condition and the boundary temperatures under the cold wave cooling condition.

[0054] Under heating conditions, the temperature of the top surface of the stacked box aqueduct is: The top edge temperature of gas-phase coupled heat exchange zone 1 is Under the premise that the greenhouse effect has a relatively small impact, the temperature of gas-phase coupled heat exchange zone 1 is... Approximately A temperature jump is performed at point 2 corresponding to the water level, jumping to... Since the lower air chamber 4 is equipped with a vent, its temperature is the background ambient temperature. Based on the temperatures under the above-mentioned heating scenario, as boundary conditions, the transient nonlinear heat conduction partial differential equation is substituted into iterative solutions using finite element software. The transient evolution temperature field along the height direction of the stacked box aqueduct section is extracted, and the discontinuous solar radiation temperature gradient curve containing the abrupt step characteristics at the water surface line is output.

[0055] In addition, under the condition of cold wave cooling, the temperature of the top surface of the stacked box aqueduct is The top edge temperature of gas-phase coupled heat exchange zone 1 is The remaining temperatures are consistent with the heating scenario. Based on all temperatures under the cooling scenario, iterative solutions are performed using finite element software to verify whether the sudden increase in horizontal tensile stress meets the design threshold. If it does not meet the threshold, the location of the sudden increase in horizontal tensile stress is the risk point for cracking. This effectively prevents horizontal cracks in critical components such as the saddle plate.

Claims

1. A method for calculating segmented discontinuous solar radiation temperature gradient in a closed-loop stacked box aqueduct, characterized in that, The enclosed stacked box aqueduct includes a top plate area, a water-passing inner cavity, and a lower air cavity area. The method includes the following steps: S1. Obtain the three-dimensional structure of the closed stacked box aqueduct and construct a three-dimensional analysis model; S2. Based on the three-dimensional analysis model, according to the water level, the water passage cavity of the closed stacked box aqueduct is divided into a gas-phase coupling heat transfer zone, a gas-liquid phase interface zone, and a fluid heat source anchoring zone along the height from high to low, and a thermo-solid coupling heat transfer model that distinguishes the properties of the medium is constructed. S3. Under the heating condition, determine the top surface temperature of the closed stacked box aqueduct, calculate the top edge temperature of the gas-phase coupling heat exchange zone, quantify the greenhouse effect of the inner cavity, obtain the temperature of the gas-phase coupling heat exchange zone, quantify the fluid anchoring effect, obtain the temperature of the fluid heat source anchoring zone, quantify the atmospheric temperature, and obtain the temperature of the lower gas cavity region. S4. For the stacked aqueduct structure corresponding to the gas-phase coupling heat exchange zone, an exponential decay function or a polynomial function is used to describe the temperature change from the surface to the interior caused by solar radiation. For the stacked aqueduct structure corresponding to the fluid heat source anchoring zone, a linear smooth function is used to describe the uniform temperature gradient protected by fluid anchoring. For the stacked aqueduct structure corresponding to the lower air cavity zone, a linear smooth function is used to describe the temperature gradient of the lower air cavity zone. The Sigmoid family step smoothing operator is used to bridge the temperature change of the stacked aqueduct structure corresponding to the gas-phase coupling heat exchange zone and the uniform temperature gradient of the stacked aqueduct structure corresponding to the fluid heat source anchoring zone, thereby achieving the bridging of the uniform temperature gradient on the top surface of the lower air cavity zone and obtaining the segmented discontinuous solar radiation temperature gradient kernel function along the height coordinate. S5. Based on the thermo-solid coupled heat transfer model that distinguishes the properties of the medium, the discontinuous solar radiation temperature gradient kernel function is used as the boundary driving source. The temperature of the top plate area, the temperature of the gas-phase coupled heat transfer area, the temperature of the fluid heat source anchoring area and the temperature of the lower air cavity area are used as boundary conditions. The transient nonlinear heat conduction partial differential equation is substituted into the equation for iterative solution. The transient evolution temperature field of the stacked box aqueduct section along the height direction is extracted, and the discontinuous solar radiation temperature gradient curve containing the abrupt step characteristics at the water surface line is output.

2. The method for calculating the segmented discontinuous solar radiation temperature gradient of a closed stacked box aqueduct according to claim 1, characterized in that, In S2, a gas-liquid transition bandwidth threshold is set, denoted as... The height of the water level is recorded as The height is recorded as ,when At that time, the current altitude is in the gas-phase coupled heat transfer zone. At that time, the current altitude is in the gas-liquid phase interface region. At that time, the current altitude is within the fluid heat source anchoring zone.

3. The method for calculating the segmented discontinuous solar radiation temperature gradient of a closed stacked box aqueduct according to claim 1, characterized in that, In S3, the formula for calculating the top surface temperature of the top plate of the closed stacked box aqueduct is as follows: ,in, This indicates the temperature of the top surface of the roof slab. Indicates standard temperature. This represents the correction factor for the sunshine area. This indicates the reduction factor for the insulation board.

4. The method for calculating the segmented discontinuous solar radiation temperature gradient of a closed stacked box aqueduct according to claim 1, characterized in that, In S3, the formula for calculating the top edge temperature of the gas-phase coupled heat exchange zone is: , This indicates the temperature of the top surface of the roof slab. Represents the natural constant. This represents the combined attenuation constant of the concrete material and the cavity interface. The thickness of the top plate. This indicates the temperature at the top edge of the gas-phase coupled heat exchange zone.

5. The method for calculating the segmented discontinuous solar radiation temperature gradient of a closed stacked box aqueduct according to claim 1, characterized in that, In S3, the formula for calculating the temperature of the gas-phase coupled heat exchange zone is: ,in, This indicates the temperature of the gas-phase coupled heat exchange zone. This indicates the temperature at the top edge of the gas-phase coupled heat exchange zone. This represents the greenhouse compensation value.

6. The method for calculating the segmented discontinuous solar radiation temperature gradient of a closed stacked box aqueduct according to claim 5, characterized in that, In S3, the formula for calculating the temperature of the fluid heat source anchoring zone is: , This indicates the temperature of the fluid heat source anchoring zone, which dynamically anchors the temperature of the inner wall of the submerged section of the stacked aqueduct to the fluid temperature. ,in, Indicates the temperature of the water. This represents the jump amplitude; the formula for calculating the temperature of the lower air cavity region is: , This indicates the temperature of the lower air chamber. It indicates atmospheric temperature.

7. The method for calculating the segmented discontinuous solar radiation temperature gradient of a closed stacked box aqueduct according to claim 1, characterized in that, In S4, the kernel function for the discontinuous solar radiation temperature gradient segmented along the height coordinate is: ;in, The kernel function represents the discontinuous solar radiation temperature gradient segmented along the height coordinate. This represents the isothermal gradient function of the stacked box aqueduct corresponding to the lower air cavity region. T2 represents the uniform temperature gradient function of the stacked aqueduct structure corresponding to the fluid heat source anchoring zone, which is protected by fluid anchoring. This represents the temperature change function from the surface to the interior of the stacked box aqueduct structure corresponding to the gas-phase coupled heat exchange zone caused by solar radiation. This represents the temperature change function at the top of the stacked box aqueduct structure caused by sunlight. This represents the Sigmoid family of step smoothing operators. ; i takes 1, 2, 3, Indicates the current position relative to At height, This represents the step steepness control coefficient. The value of is negatively correlated with the meniscus thickness caused by the surface tension of liquid and gas at the interface and the capillary climb height of the concrete. Indicates altitude, Indicates the height of the top surface of the lower air cavity region. Indicates the height of the waterline. This indicates the height of the bottom surface of the top plate.

8. The method for calculating the segmented discontinuous solar radiation temperature gradient of a closed stacked box aqueduct according to claim 1, characterized in that, In S5, the expression for the transient nonlinear heat conduction partial differential equation is: ;in, This indicates the density of concrete. Indicates specific heat capacity. Indicates the rate of temperature change. express Thermal conductivity in the direction of Indicates temperature at Rate of change of direction express Thermal conductivity in the direction of Indicates temperature at Rate of change of direction express Thermal conductivity in the direction of Indicates temperature at Rate of change of direction This indicates the internal heat source of the concrete.

9. The method for calculating the segmented discontinuous solar radiation temperature gradient of a closed stacked box aqueduct according to claim 1, characterized in that, The method further includes: using the discontinuous solar radiation temperature gradient curve containing the abrupt step characteristics at the water surface line and the top surface of the lower air cavity as a boundary load, mapping it into the static solver for thermodynamic coupling analysis; identifying the strong shear shear and out-of-plane bending secondary stress peaks at the interface between the upper hot and lower cold caused by fluid anchoring, and automatically adding anti-crack structural steel strands at the horizontal intersection position of the stacked box web according to the peak value vector of the secondary stress peaks.

10. The method for calculating the segmented discontinuous solar radiation temperature gradient of a closed stacked box aqueduct according to claim 1, characterized in that, The method further includes: under cold wave cooling conditions, reversibly assigning feature point values ​​to the thermo-solid coupled heat transfer model that distinguishes medium properties, wherein the feature point values ​​include: setting the top surface temperature as the extreme cold temperature, and the extreme cold temperature as... , This indicates the temperature of the top surface of the top plate, and the temperature of the gas-phase coupling heat exchange zone is set to... , This represents the temperature at the top edge of the gas-phase coupled heat exchange zone, and the temperature of the fluid heat source anchoring zone is set to... Temperature of the lower air chamber Therefore, it is necessary to verify whether the sudden increase in horizontal tensile stress meets the design threshold. If it does not, the location of the sudden increase in horizontal tensile stress is the risk point for cracking.

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