Concrete box girder temperature field numerical simulation method and system

Abstract

The invention discloses a concrete box girder temperature field numerical simulation method and system. The method comprises the following steps: constructing a concrete box girder temperature field model; determining the speed boundary layer thickness of different positions of the outer surface of the box girder according to the incoming flow wind speed, determining the thermal boundary layer thickness of the outer surface of the box girder according to the speed boundary layer thickness, and obtaining the convective heat transfer coefficient of the outer surface of the box girder under different incoming flow wind speeds according to the wind speed at the thermal boundary layer thickness, the environment temperature and the surface temperature of the box girder; determining heat convection boundary conditions according to the convection heat transfer coefficient, the environment temperature and the internal temperature of the box girder; determining thermal radiation boundary conditions according to solar radiation on the outer surface of the box girder; determining heat conduction boundary conditions according to the environment temperature and the box girder surface temperature; and performing temperature field numerical simulation on the concrete box girder temperature field model based on thermodynamic boundary conditions to obtain a temperature field thermodynamic analysis result. A numerical simulation research framework considering actual wind field distribution of the box girder is adopted, the accuracy of simulation results is improved, and errors are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of box girder temperature field analysis, and in particular to a concrete box girder temperature field numerical simulation method and system. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] As a large, complex structure exposed to the external environment, different parts of the bridge are affected by the external environment to different degrees, resulting in uneven temperature distribution. Early research was mainly based on complex theoretical research, such as the use of Fourier differential equations, finite difference methods and self-programming for thermodynamic theoretical analysis, which brought difficulties to the study of bridge temperature field and temperature strain. At present, existing research is more combined with model tests and numerical simulations.

[0004] A study used BRIGADE / Plus software based on ANSYS CAE secondary development to simulate the temperature field of a single-box single-chamber concrete box girder. The calculated temperature gradient has a high accuracy and can cover the positive temperature gradient throughout the day. However, the calculated result of the negative temperature gradient at night is quite different from the measured value.

[0005] A study used COMSOL software to analyze the temperature field, radiation field, and displacement field of a single-box single-chamber concrete bridge with a span of 50m, and established a full-scale 3D thermodynamic finite element model to study the temperature field of a single-box single-chamber concrete box girder. However, the object of the study was a single-box single-chamber box girder. When analyzing thermal convection, the incoming wind speed was directly used in the empirical formula, and the box chamber was directly exposed to the external environment during modeling, without considering the impact of the temperature distribution inside the closed box chamber on the indoor temperature of the box girder model.

[0006] Some studies have used ANSYS finite element software to construct a 2D finite element model of the mid-span section of a single-box multi-chamber box girder bridge, while taking into account the concrete structure of the box girder and the air inside the box chamber to establish a model, and using site monitoring data to evaluate and verify the model. At present, a large number of studies on bridge temperature fields have been carried out based on experimental testing, numerical simulation and other methods, but there are still some shortcomings.

[0007] First, in terms of numerical simulation research on bridge temperature fields, there are relatively few numerical simulation studies on single-box three-chamber concrete box girders. The single-box multi-chamber structure means that the main beam faces more complex temperature field characteristics, and the current research on single-box multi-chamber concrete box girders ignores the impact of wind fields on the actual temperature distribution of the box girder.

[0008] Secondly, when considering thermal convection boundary conditions, the convection heat transfer coefficient is a function of multiple variables such as wind speed, surface roughness, and geometric structures exposed outdoors, and there is no analytical expression that accurately describes these factors. A study modeled and simulated the hydration heat of a large concrete dam. The results showed that since the convection heat transfer coefficient was derived through an empirical formula, the wind speed used on the surfaces of different bridge structures was a unified incoming wind speed, which led to errors in the simulation results, with an error of about 5%. It can be seen that the incoming wind speed has a significant effect on the convection heat transfer coefficient of the box girder structure surface, which in turn affects the accuracy of the temperature field analysis results. Summary of the invention

[0009] In order to solve the above problems, the present invention proposes a numerical simulation method and system for the temperature field of a concrete box girder, which adopts a numerical simulation research framework that considers the actual wind field distribution of the box girder to determine more accurate convective heat transfer boundary conditions on the surface of the box girder structure, improve the accuracy of the simulation results, and reduce errors.

[0010] In order to achieve the above object, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides a method for numerically simulating a temperature field of a concrete box girder, comprising:

[0012] Construct the temperature field model of concrete box girder;

[0013] Obtain the ambient temperature, box girder internal temperature, box girder surface temperature, solar radiation and wind speed;

[0014] The velocity boundary layer thickness at different positions on the outer surface of the box girder is determined according to the incoming wind speed, the thermal boundary layer thickness on the outer surface of the box girder is determined according to the velocity boundary layer thickness, and the convective heat transfer coefficient of the outer surface of the box girder under different incoming wind speeds is obtained according to the wind speed, ambient temperature and box girder surface temperature at the thermal boundary layer thickness.

[0015] Determine the thermodynamic boundary conditions; among which, the thermal convection boundary conditions are determined according to the convection heat transfer coefficient, the ambient temperature and the internal temperature of the box girder; the thermal radiation boundary conditions are determined according to the solar radiation on the outer surface of the box girder; and the thermal conduction boundary conditions are determined according to the ambient temperature and the surface temperature of the box girder;

[0016] Based on the thermodynamic boundary conditions, the temperature field numerical simulation of the concrete box girder temperature field model was carried out to obtain the thermodynamic analysis results of the temperature field.

[0017] As an optional embodiment, the convective heat transfer coefficient is: Among them, T A is the ambient temperature, T S is the surface temperature of the box girder; U i is the thickness of the thermal boundary layer δ t The wind speed at the place.

[0018] As an alternative embodiment, the thermal boundary layer thickness δ t is: t =Pr -1 / 3 δ; where Pr is the Prandtl number and δ is the velocity boundary layer thickness.

[0019] As an optional embodiment, the velocity boundary layer thickness is: Where α and β are constants that depend on the incoming wind speed; x is the distance from the starting point of the calculation boundary on the box girder surface to the calculation point.

[0020] As an optional implementation, the thermal convection boundary condition is: q c =h c ·(T B -T A );where q c is the heat transfer density of convection; T B is the internal temperature of the box girder; T A is the ambient temperature; h c is the convective heat transfer coefficient.

[0021] As an optional implementation, the process of determining the thermal radiation boundary condition includes:

[0022] According to the ambient temperature T A and the box girder surface temperature T S Determine the radiation heat transfer between the outer surface of the box girder and the external environment: ε u is the emissivity of the outer surface of the box beam, β S is the Boltzmann constant;

[0023] According to the total solar radiation received by the outer surface of the box girder I S Determine the total amount of solar radiation reflected from the ground and the external environment: β G is the reflectivity of the ground and the external environment; δ is the angle between the reflected radiation and the box girder surface;

[0024] According to the absorption rate of solar radiation by the box girder α and the total solar radiation I received by the outer surface of the box girder S The solar radiation on the outer surface of the box girder is determined by the product of the box girder's absorption rate α and the total amount of solar radiation reflected by the ground and the external environment, and the solar radiation component reflected by the ground and the surrounding environment is determined according to the product of the thermal radiation boundary conditions.

[0025] As an optional implementation, the heat conduction boundary conditions include:

[0026] First-type boundary condition: The internal temperature of the box girder is set as the first-type boundary condition, denoted as T(Γ,t), i.e., T|Γ1 =T(Γ,t);

[0027] The second type of boundary conditions: q S is the solar radiation on the outer surface of the box girder; n is the direction; k is the thermal conductivity; T is the temperature at any point;

[0028] The third type of boundary conditions: In the formula, h c is the convective heat transfer coefficient; T A is the external environment temperature, T S is the box girder surface temperature.

[0029] In a second aspect, the present invention provides a concrete box girder temperature field numerical simulation system, comprising:

[0030] A model building module is configured to build a temperature field model of a concrete box girder;

[0031] A data acquisition module is configured to acquire ambient temperature, box girder internal temperature, box girder surface temperature, solar radiation and wind speed;

[0032] The module for determining the convective heat transfer coefficient is configured to determine the thickness of the velocity boundary layer at different positions of the outer surface of the box girder according to the incoming wind speed, determine the thickness of the thermal boundary layer on the outer surface of the box girder according to the thickness of the velocity boundary layer, and obtain the convective heat transfer coefficient of the outer surface of the box girder at different incoming wind speeds according to the wind speed, ambient temperature and box girder surface temperature at the thickness of the thermal boundary layer;

[0033] The boundary condition determination module is configured to determine the thermodynamic boundary conditions; wherein the thermal convection boundary conditions are determined according to the convection heat transfer coefficient, the ambient temperature and the internal temperature of the box beam; the thermal radiation boundary conditions are determined according to the solar radiation on the outer surface of the box beam; and the thermal conduction boundary conditions are determined according to the ambient temperature and the surface temperature of the box beam;

[0034] The thermodynamic analysis module is configured to perform temperature field numerical simulation on the temperature field model of the concrete box girder based on thermodynamic boundary conditions to obtain temperature field thermodynamic analysis results.

[0035] In a third aspect, the present invention provides an electronic device comprising a memory and a processor, and computer instructions stored in the memory and executed on the processor, wherein when the computer instructions are executed by the processor, the method described in the first aspect is performed.

[0036] In a fourth aspect, the present invention provides a computer-readable storage medium for storing computer instructions, wherein when the computer instructions are executed by a processor, the method described in the first aspect is performed.

[0037] In a fifth aspect, the present invention provides a computer program product, comprising a computer program, which, when executed by a processor, implements the method described in the first aspect.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] Existing temperature field research directly uses field tests or meteorological stations to monitor wind speed on the surface of bridge structures and substitutes it into empirical formulas to define thermal convection boundary conditions, and rarely considers the impact of wind on different surfaces of bridge structures. Therefore, the present invention proposes a numerical simulation method and system for the temperature field of a concrete box girder, which adopts a numerical simulation research framework that considers the actual wind field distribution of the box girder, determines the velocity boundary layer thickness and thermal boundary layer thickness at different positions on the outer surface of the box girder according to the incoming wind speed, and then obtains the convective heat transfer coefficient of the outer surface of the box girder under different incoming wind speeds according to the wind speed at the thermal boundary layer thickness, the ambient temperature and the box girder surface temperature, thereby determining a more accurate convective heat transfer boundary condition on the surface of the box girder structure, realizing the relationship between the wind speed at the thermal boundary layer thickness on the outer surface of the box girder structure and the incoming wind speed, the distribution characteristics of the wind speed on different structural surfaces, and the impact of wind speed on the convective heat transfer coefficient, thereby improving the accuracy of the simulation results and reducing errors.

[0040] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0042] Figure 1 A technical roadmap of a numerical simulation method for temperature field of a concrete box girder provided in Example 1 of the present invention;

[0043] Figure 2 A schematic diagram of the thermodynamic environment of the temperature field model of a single-box three-chamber concrete box girder provided in Example 1 of the present invention;

[0044] Figure 3 A schematic diagram of velocity boundary and thermodynamic boundary provided in Example 1 of the present invention;

[0045] Figure 4 The temperature field model of the concrete box girder provided in Example 1 of the present invention;

[0046] 5(a)-(b) are schematic diagrams of daily average ambient temperature and daily maximum ambient temperature difference provided in Example 1 of the present invention;

[0047] Figure 6 (a)-(b) is a schematic diagram of the daily average wind speed and wind direction variation pattern provided in Example 1 of the present invention;

[0048] Figure 7 A schematic diagram of a computational fluid domain provided in Example 1 of the present invention;

[0049] Figure 8 A schematic diagram of wind farm grid division provided in Example 1 of the present invention;

[0050] 9(a)-(b) are schematic diagrams of x-direction velocity distribution on the upper surface of the top plate and the lower surface of the bottom plate of the box girder with different grid sizes provided in Example 1 of the present invention;

[0051] 10(a)-(b) are schematic diagrams of thermal boundary layer thickness around the upper surface of the top plate and the lower surface of the bottom plate of the box girder provided in Example 1 of the present invention;

[0052] Fig.11 A cloud diagram of steady-state simulation results provided in Example 1 of the present invention;

[0053] Figures 12(a)-(h) are wind speed distribution diagrams of the top plate, bottom plate, web A, web D, left flange tip, right flange tip, left flange lower side, and right flange lower side of the box girder under different incoming wind speeds provided in Example 1 of the present invention;

[0054] Fig.13 A schematic diagram of wind speed at the thickness of the thermal boundary layer provided in Example 1 of the present invention;

[0055] Fig.14 A schematic diagram of the radiation field grid division provided in Example 1 of the present invention;

[0056] 15(a)-(b) are temperature comparison and error comparison result diagrams of different grid sizes provided in Example 1 of the present invention;

[0057] 16(a)-(d) are hourly measured and finite element calculated temperature records of the top of web D, the middle of web D, the top of web A, and the middle of web A provided in Example 1 of the present invention;

[0058] Figures 17(a)-(d) are comparison diagrams of the temperature gradient distributions of web A, web B, web C, and web D provided in Example 1 of the present invention, which are measured and calculated using finite element method. DETAILED DESCRIPTION

[0059] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0060] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0061] It should be noted that the terms used herein are only for describing specific embodiments, and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that the terms "include" and "comprise" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0062] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0063] Example 1

[0064] This embodiment takes a single-box three-chamber concrete box girder as the research object, establishes a single-box three-chamber concrete box girder temperature field model, conducts a single-box three-chamber concrete box girder dot matrix temperature field model test, and adopts a numerical simulation research framework that considers the actual wind field distribution of the box girder. The research results include the relationship between the wind speed and the incoming wind speed at the thickness of the thermal boundary layer on the outer surface of the box girder structure, the distribution characteristics of wind speed on different structural surfaces, and the analysis of the influence of wind speed on the convective heat transfer coefficient. The actual measured temperature and vertical temperature gradient of the box girder model temperature field verify the effectiveness of using the wind speed reduction factor for temperature field analysis, providing a reference for the temperature field analysis of bridge structures.

[0065] like Figure 1 As shown, this embodiment provides a numerical simulation method for the temperature field of a concrete box girder, comprising:

[0066] Construct the temperature field model of concrete box girder;

[0067] Obtain the ambient temperature, box girder internal temperature, box girder surface temperature, solar radiation and wind speed;

[0068] The velocity boundary layer thickness at different positions on the outer surface of the box girder is determined according to the incoming wind speed, the thermal boundary layer thickness on the outer surface of the box girder is determined according to the velocity boundary layer thickness, and the convective heat transfer coefficient of the outer surface of the box girder under different incoming wind speeds is obtained according to the wind speed, ambient temperature and box girder surface temperature at the thermal boundary layer thickness.

[0069] Determine the thermodynamic boundary conditions; among which, the thermal convection boundary conditions are determined according to the convection heat transfer coefficient, the ambient temperature and the internal temperature of the box girder; the thermal radiation boundary conditions are determined according to the solar radiation on the outer surface of the box girder; and the thermal conduction boundary conditions are determined according to the ambient temperature and the surface temperature of the box girder;

[0070] Based on the thermodynamic boundary conditions, the temperature field numerical simulation of the concrete box girder temperature field model was carried out, and the thermodynamic analysis results of the temperature field were obtained.

[0071] like Figure 2 The figure shows the thermodynamic environment schematic diagram of the concrete box girder temperature field model, which shows the heat transfer process between the concrete box girder and the external environment. The heat exchange process between the concrete box girder and the external environment is similar to almost all heat transfer processes, including three basic heat energy transfer methods such as heat conduction, heat convection and heat radiation. In this process, there is heat convection and heat radiation between the concrete box girder and the external environment, and there is heat conduction inside the box girder, so the heat convection boundary conditions, heat radiation boundary conditions and heat conduction boundary conditions can be used as thermodynamic boundary conditions.

[0072] The thermodynamic boundary behavior between the external environment and the heat transfer system of the concrete box girder can be expressed as the total heat flux q, in W / m 2 , that is, the sum of the heat flows:

[0073] q=q c +q S +q G +q L +q B (1)

[0074] In the formula, q c is the heat convection between the outside air and the box girder surface; q S is the solar radiation on the box girder surface boundary; q G is the radiation component reflected from the ground and the surrounding environment; q L is the long-wave radiation component; q B is the surface-to-surface radiation of the box girder.

[0075] In this embodiment, the process of determining the thermal convection boundary condition is as follows.

[0076] Thermal convection refers to the heat conduction phenomenon that occurs when there is a temperature difference between the surface of an object and the surrounding environment (such as the atmospheric temperature or the temperature of the fluid in the space), which is governed by Newton's cooling equation:

[0077] q c =h c ·(T B -T A )(2)

[0078] In the formula, q c is the heat transfer density of convection (W / m 2 );T B is the internal temperature of the box girder; T A is the ambient temperature; h c is the convective heat transfer coefficient (W / (m 2·℃), the convective heat transfer coefficient is closely related to the wind speed. The greater the wind speed, the greater the convection coefficient.

[0079] Substituting the Nusselt temperature coefficient Nu into the heat transfer coefficient constant term between the box girder surface temperature and the ambient temperature in the windless condition, the convective heat transfer coefficient h for civil engineering is obtained. c :

[0080]

[0081] Where, T A is the ambient temperature (℃), T S is the box girder surface temperature (℃), w is the wind speed and w≤5m / s.

[0082] However, due to the different geometric shapes of the box girder, even at the same incoming wind speed, different surfaces are affected by the wind speed to different degrees; in addition, even on the same surface, such as the upper surface of the roof, the wind speed distribution will be uneven along the geometric width. Just as the fluid dynamic boundary layer is defined as the region where viscous forces exist in the flow, the thermal boundary layer can also be defined as the region where the temperature gradient exists in the flow. The temperature gradient in this region is caused by the heat exchange process between the fluid and the wall.

[0083] like Figure 3 In the velocity boundary and thermodynamic boundary diagram shown in the figure, the surface temperature of the box beam is T S , the fluid temperature at infinity outside the thermal boundary layer is T ∞ , the thickness of the thermal boundary layer is δ t ; At the surface of the box beam, the velocity is zero, and the heat is transferred to the fluid through heat transfer behavior. When the fluid flows through the solid surface at a certain speed, a velocity boundary layer is formed on the solid surface.

[0084] In the velocity boundary layer, since the fluid particles adhere to the solid surface, the velocity on the solid surface is 0, and at the boundary layer thickness δ, the velocity gradually approaches the incoming wind speed U ∞ , there is a velocity gradient within the distance range from the solid surface to δ. At the same time, when a fluid with uniform temperature flows through a solid surface with uneven temperature, a thermal boundary layer is formed between the fluid and the solid surface. The temperature at the solid surface is infinitely close to the solid surface temperature, and the thickness of the thermal boundary layer is δ. t At the point, the temperature gradually approaches the fluid temperature T ∞ , from the solid surface to the thermal boundary layer thickness δ t There is a temperature gradient within the range, and convective heat exchange behavior occurs in this range.

[0085] Therefore, replace w in equation (3) with the thermal boundary layer thickness δ t Wind speed U i , and the ambient temperature TA Considered as fluid temperature T ∞ In order to study the different surfaces of the box girder under the same incoming wind speed U ∞ The following are the different impacts:

[0086]

[0087] Therefore, the thickness of the thermal boundary layer on the box beam surface δ t Substitute the wind speed at the location into equation (4) to obtain the convective heat transfer coefficient of the surface at each location.

[0088] In this embodiment, the thermal boundary layer thickness δ t It is usually defined as the temperature in the boundary layer where 99% of the fluid temperature T ∞ The Prandtl number Pr is used to relate the thermal boundary layer to the velocity boundary layer:

[0089] δ t =Pr -1 / 3 δ(5)

[0090] Wherein, Prandtl number Pr is used to characterize the relative thickness parameter between velocity boundary layer and thermal boundary layer. Except for liquid metal and high viscosity fluid, the velocity boundary layer thickness and thermal boundary layer thickness are usually of similar order of magnitude:

[0091]

[0092] Where v is the fluid's kinematic viscosity and α is the fluid's thermal diffusivity. The fluid's kinematic viscosity v and thermal diffusivity α convey information about the rate at which molecules diffuse through the fluid, and the ratio of the two represents the relative magnitude of momentum and heat diffusion in the fluid. Therefore, Pr can characterize the connection between the velocity field and the temperature field. The Prandtl number Pr and kinematic viscosity v of dry air vary with temperature, and the thermophysical properties of dry air are listed in Table 1.

[0093] Table 1 Thermophysical properties of dry air

[0094]

[0095] The thickness of the velocity boundary layer is:

[0096]

[0097] In the formula, α and β are constants, depending on the incoming wind speed U ∞ , when the incoming wind speed U ∞ ≤5m / s (laminar flow), α=-0.5, β=5; when U ∞ When >5m / s (turbulent flow), α=-1 / 5, β=0.37; x is the distance from the starting point of the calculation boundary of the solid surface to the calculation point (m).

[0098] The Reynolds number Re is:

[0099]

[0100] Where l is the characteristic linear dimension and v is the kinematic viscosity of the fluid.

[0101] In this embodiment, the process of determining the thermal radiation boundary condition is as follows.

[0102] Solar radiation on the outer surface of the box girder q S for:

[0103] q S =αI S (9)

[0104] Where α is the absorption rate of concrete box girder to solar radiation, I S is the total solar radiation received by the outer surface of the box girder from the sun. In this embodiment, the data measured by the solar radiation sensor is directly used as the total solar radiation I of the outer surface of the box girder. S .

[0105] The solar radiation component q reflected from the ground and surrounding environment G for:

[0106] q G =αI G (10)

[0107] In the formula, I G is the total amount of solar radiation reflected by the ground and the surrounding environment, which is:

[0108]

[0109] In the formula, β G is the reflectivity (albedo) of the ground and the surrounding environment, which represents the ratio of the reflected radiation of a surface to the total radiation incident on the surface. Regardless of the shading effect of the flange plates on both sides of the box girder, there will be reflected radiation on the surface of the box girder structure; δ is the angle between the reflected radiation and the box girder surface.

[0110] Long wave radiation component q L It describes the radiation heat transfer between the outer surface of the box girder structure and the surrounding air:

[0111]

[0112] In the formula, ε u is the emissivity of the outer surface of the concrete box girder structure, which is used to characterize the radiation capability of the medium, β S is the Boltzmann constant, which can be taken as 5.67×10 -8 W / (m 2 ℃ 4).

[0113] Mutual illumination between the surfaces of the box girder structure B It is generated by the surface-to-surface radiation between the structural surfaces. Based on the above parameters, the thermal radiation boundary conditions can be directly determined through COMSOL software.

[0114] In this embodiment, the process of determining the heat conduction boundary condition includes:

[0115] The heat conduction process inside the box girder structure is estimated by the Fourier partial differential equation, which is expressed as:

[0116]

[0117] Where: T is the temperature at any point (x, y, z); k is the thermal conductivity; Q is the internal heat source of the box girder (heat generated per unit volume); ρ is the material density; c is the specific heat of the material; t is the time variable.

[0118] Heat transfer boundary conditions represent the heat transfer behavior between the external environment and the research object, which are usually divided into three categories:

[0119] (1) The first type of boundary conditions.

[0120] There is a certain temperature distribution on the boundary of the heat conduction system under study, which can be a constant value or a function of time and space:

[0121] T| Γ1 =T(Γ,t)(14)

[0122] In this embodiment, the internal temperature of the box girder is set as the first type of boundary condition, expressed as T(Γ,t), which belongs to the non-steady-state condition of the internal environment.

[0123] (2) The second type of boundary conditions.

[0124] When there is heat conduction between the external environment and the research object, the derivative of the given temperature in the normal direction of the heat conduction system boundary is:

[0125]

[0126] In this embodiment, the sealing layers at both ends of the box beam section adopt adiabatic boundary conditions, and there is Since the model is supported by piers, the position of the piers also needs to be set to adiabatic conditions; n is a directional quantity and has no practical meaning.

[0127] (3) The third type of boundary conditions.

[0128] The temperature of the heat conduction boundary and the derivative of the temperature in the normal direction are linearly combined, that is, there is heat exchange between the system and the outside world. Its connotation is a combination of the first and second boundary conditions:

[0129]

[0130] In the formula, h c is the convective heat transfer coefficient; T A is the external environment temperature, T S is the temperature of a boundary of the heat conduction system, which is the surface temperature of the box beam in this embodiment.

[0131] In this embodiment, a temperature field model of a single-box three-chamber concrete box girder is established, such as Figure 4 As shown, the temperature sensors are fixed on the steel skeleton, and the temperature field model of the box girder includes the web A on the sun-facing side, the middle web B on the sun-facing side, the middle web C on the sun-facing side, and the web D on the sun-facing side.

[0132] In this embodiment, the meteorological parameters obtained include: ambient temperature, solar radiation, and wind speed and direction. During the monitoring period, due to the influence of objective conditions (such as battery, signal, hardware failure, etc.), the meteorological sensors had different degrees of data missing (the atmospheric temperature and solar radiation data were missing for 20 days, the air humidity data was missing for 152 days, and the wind speed data was missing for 180 days). For abnormal data, first exclude the data that is obviously inconsistent with the rules, and then fill it according to the surrounding data, use the average value of the previous and next data for interpolation, and use arithmetic progression to fill in the part with large differences.

[0133] This embodiment takes the meteorological parameters measured on site at a certain place as an example. As shown in Figure 5(a)-(b), the ambient temperature in the summer of 2022 where the box girder model is located is higher than that in the summer of 2021. The ambient temperature shows periodic changes over time, and high temperatures are mainly distributed in summer and autumn. The highest value of the daily average temperature occurs in autumn, which is 39.4°C, and the lowest value occurs in winter, which is 5.36°C, which is close to the dates of the highest and lowest temperatures. The overall ambient temperature difference in summer and autumn is slightly higher than that in winter and spring, with a maximum value of 16.9°C. As shown in Figure 6(a)-(b), the daily average wind speed and wind direction change with season and time. The average wind speed in spring and summer is lower than that in autumn and winter, mainly south wind and southerly wind, with a minimum wind speed of 0.45m / s and a maximum wind speed of 5.75m / s.

[0134] To sum up, among the local meteorological parameters, the distribution of daily ambient temperature and solar radiation in different seasons shows obvious seasonality, which is higher in summer and autumn and lower in winter and spring; in terms of wind speed and wind direction, the wind speed is lower in spring and summer and higher in autumn and winter, mainly south wind and southerly wind, showing certain seasonal changes.

[0135] 1. Wind field analysis.

[0136] This example uses a large concrete box girder as the research object and builds a temperature field test model. The upper surface of the model top plate (TOP), the flange tips on both sides (YYL & YYR), the web surface (WebA, WebD) and the lower surface of the bottom plate (BOTTOM) are all parallel or perpendicular to the ground, and the lower surface of the flange (YYLD & YYRD) has a certain inclination angle, such as Figure 7 The difference from the actual bridge shape is that the lane position on the upper surface of the top plate of the actual bridge has a slope of 2.0%.

[0137] Four operating conditions are considered:

[0138] Working condition 1: The average inflow wind speed w is directly used for all external surfaces without considering the actual wind field distribution, so CFD simulation is not required. Working condition 1 is the conventional method used in most current studies and is used as a benchmark in this embodiment.

[0139] Working condition 2: In order to obtain the refined wind field distribution law on the surface of the box girder structure and consider the actual wind field distribution, it is necessary to perform computational fluid dynamics (CFD) simulation on the surface wind field of the box girder temperature field model to obtain the wind field distribution on the surface of the box girder temperature field model structure.

[0140] In addition to analyzing the actual measured data (wind speed), the basic wind speed of 24.9 mm / s is considered during wind load, and 10 different incoming wind speeds U in the range of 1 to 30 m / s are analyzed. ∞ ,As shown in Table 2, the wind speed range of breeze is 1-5 m / s, increasing by 1 m / s, and the wind speed range of strong wind is 10-30 m / s, increasing by 5 m / s.

[0141] Table 2 Working conditions of CFD simulation wind farm

[0142]

[0143] A two-dimensional simulation of the wind field where the box girder is located is performed. The computational fluid domain is a rectangular domain, and the width and height are set to 18 times the box girder width (18D) and 40 times the box girder height (40H). ver ), the blocking rate is 2.5%, such as Figure 7 As shown in the figure, the shear stress transport SST k-ω model is used to carry out the Reynolds-averaged Navier-Stokes (RANS) numerical simulation on the surface of the box girder structure.

[0144] In this embodiment, according to the on-site measurement, the local south wind and southerly wind are dominant, so the right side of the box girder (sunny side, south side) is set as the incoming flow direction, the fluid flows from right to left, and the wind attack angle is 0. Then, the right side of the calculation domain is set as the velocity inlet, and the surface of the box girder structure is set as a stationary wall without slip.

[0145] Figure 7 The schematic diagram of the computational fluid domain is shown. Wind field monitoring points are arranged on the surface of the box girder, among which TOP 1-200 Indicates that monitoring points are arranged on the top surface of the roof. The subscript 1-200 indicates that 200 monitoring points are used. 1-200 It means that 200 monitoring points are arranged on the lower surface of the bottom plate. Similarly, WebA represents web A, WebD represents web D, YYL represents the tip of the left flange, YYLD represents the lower side of the left flange, YYR represents the tip of the right flange, and YYRD represents the lower side of the right flange.

[0146] 2. Verification of grid independence in wind field research.

[0147] Meshing is crucial in numerical simulation. The mesh size directly affects the calculation results of the actual wind field distribution on the box girder surface by fluid dynamics, and is related to the accuracy of the calculation results. In order to discuss the sensitivity of the model to the mesh size, five different mesh sizes were used, and the number of meshes of each size was counted by FLUENT. The specific size and number are shown in Table 3. In order to ensure the mesh quality near the box girder, a 12-layer body-fitting structured quadrilateral mesh was generated in the rigid domain, as shown in Figure 8 As shown, (a)-(e) are coarsened, coarser, regular, finer, and refined, respectively.

[0148] The wind field simulation process was carried out using FLUENT. In order to ensure the accuracy of the wind field distribution around the box girder, 10 -6 Convergence tolerance (including x, y direction speed and ω, etc.).

[0149] Table 3 Wind field analysis grid characteristics

[0150]

[0151] As shown in Figure 9(a)-(b), it can be observed that there are differences in wind field distribution even near different locations on the same surface. The upper surface of the top plate and the lower surface of the bottom plate show a wind speed distribution with high in the middle and low on both sides. According to Table 4, the coarse and fine grid sizes have large deviations, which is manifested in the average absolute error of the coarse grid exceeding 0.1m / s, and the maximum absolute error of the fine grid also exceeding 0.1m / s. The wind field distribution patterns of conventional, coarse and fine grid sizes are relatively close. Coarsening the unit grid will lead to an increase in the calculation error, which in turn causes deviations in the calculation results.

[0152] Table 4 Comparison of calculation errors of different mesh sizes

[0153]

[0154] Note: The error is the difference between the calculation results of different mesh size levels and the regular mesh size.

[0155] In order to balance the wind field distribution law on the box girder surface, the accuracy of the calculation results of different mesh sizes, and the calculation efficiency (the calculation time of the refined mesh is too long), a conventional size mesh was finally selected. The mesh size is about 1 / 3600 of the box girder width in the main parts (top plate, bottom plate and web), and half of the mesh size of the main parts is used at the flange position.

[0156] 3. Calculation of wind speed at the thickness of thermal boundary layer.

[0157] After preliminary CFD simulation, the upper surface of the box girder top plate and the lower surface of the bottom plate were used as examples to calculate the different incoming wind speeds U ∞ The thickness of the thermal boundary layer around the outer surface of the lower concrete box girder is δ t , as shown in Figure 10(a)-(b). On the windward side of the box girder, the thermal boundary layer thickness δ t minimum, and then gradually increases along the lateral width towards the leeward side. This trend applies to all wind conditions and is consistent with Figure 3 The trend is consistent with that shown in Figure 2. t Generally greater than δ at high wind speed t When the wind speed is 1m / s, δ t reaches its maximum value. As the wind speed increases, δ t Decreases rapidly; when the wind speed reaches 10m / s, δ t The rate of decline slowed down.

[0158] Figure 12(a)-(h) shows the average incoming wind speed U ∞ When the speed is 3m / s, 5m / s, 10m / s, 20m / s and 30m / s, the thickness of the thermal boundary layer around the outer surface of the main beam is t Wind speed U i distribution. At the same time, Fig.11 Shows the incoming wind speed U ∞ =3m / s for the steady-state numerical simulation calculation results of the wind field near the box girder model. The specific parameters of these different working conditions are listed in Table 2. It is worth noting that in this embodiment, the positive wind speed means that the wind direction is from left to right, which is different from the incoming wind speed U ∞ On the contrary; on the contrary, negative wind speed indicates that the incoming wind speed U ∞ In addition, at the web and flange tips, the wind speed is positive along the beam height, as shown in Figures 12(c)-(e) and (h).

[0159] Compare U in Case 1 and Case 2 i distribution, working condition 1 directly adopts the incoming wind speed U ∞ As the U of the outer surface of the entire box girder structurei , while condition 2 considers the actual wind field distribution around the temperature field model.

[0160] According to Figure 12(a)-(h), we can see that:

[0161] (1) The U-shaped surface near the outer surface (top plate and bottom plate) of the main structural parts of the single-box three-chamber concrete box girder model i Generally much smaller than U ∞ ; With the incoming wind speed U ∞ The increase of U on the surface of the model structure i It will also increase.

[0162] (2) In general, the U values ​​near the upper surface of the top plate and the lower surface of the bottom plate of the single-box three-chamber concrete box girder model are i Direction and wind speed U ∞ In opposite direction.

[0163] (3) At the same incoming wind speed U ∞ The upper surface of the top plate of the box girder and the lower surface of the bottom plate U i The distribution is different, and the U along the width of the plate i The distribution is also different. Specifically, U i Starting from the windward side of the top plate and the bottom plate to the leeward side, the wind speed first gradually increases after a short descending section, and then returns to the wind speed close to the starting position of the boundary layer on the windward side after the descending section. i It will continue to change, but on a smaller scale.

[0164] (4) Box girder web surface U i It is highest at the bottom and then decreases to about 0 m / s toward the top. The distributions of the windward web D and the leeward web A are similar but quite different.

[0165] (5) Surface wind speed U at each part of the leeward side i It is much lower than the parts on the windward side (as shown in Figure 12(c)-(h)).

[0166] 4. Calculation of wind speed reduction coefficient.

[0167] Previous research objects were streamlined steel box girder cross sections. When designing, it was necessary to reduce the impact of wind on the bridge. The surface wind field distribution was relatively uniform, so different incoming wind speeds U ∞ U of the center surface of each part i The wind reduction coefficient of each part is quantitatively evaluated. However, the object of this embodiment is a concrete box beam, and the cross-sectional design does not consider the influence of the wind field. Compared with the prior art, the distribution of the wind field on the same structural surface is quite different (such as Fig.11 ). Therefore, this embodiment uses the average absolute magnitude of the tangential velocity on each surface to quantitatively analyze the actual wind field on the surface of the box girder structure.

[0168] The numerical simulation results of the wind field on the box girder structure surface show that the wind speed U i With the incoming wind speed U ∞ Table 5 shows the wind speed reduction coefficient μ of the outer surface of each part around the temperature field model of the entire concrete box girder, which is defined as U i with U ∞ The ratio is:

[0169] U i =μ·U ∞ (17)

[0170] The convective heat transfer coefficient can be further modified as:

[0171]

[0172] Table 5 Summary of wind speed reduction coefficient μ

[0173]

[0174] In addition to the previously discussed i In addition to the general trend of Fig.13 From Table 5, we can see that:

[0175] (1) On the top surface of the temperature field model, the wind speed U i Reduce the incoming flow velocity U ∞ The wind speed on the surface of the windward side web D is about 20-25% of that on the windward side. The specific wind speed reduction coefficient μ is shown in Table 5.

[0176] (2) Wind speed U under the bottom plate i About U ∞ It is about 17% of μ, which is slightly lower than the μ value at the top plate.

[0177] (3) The wind speeds on the leeward web (WebA), the left flange tip (YYL), the left flange lower side (YYLD) and the right flange lower side (YYRD) are at a relatively low level (μ≤0.1).

[0178] (4) Wind speed U at the right flange tip (YYR) on the entire box girder surface i The highest, but only accounts for U ∞ About 30% of the total area of ​​the box girder, and this part is at the edge of the entire box girder. Relative to the entire box girder structure, the surface area accounts for less than 1%.

[0179] (5) Directly using empirical formulas to analyze the wind field of the box girder structure will greatly overestimate the effect of thermal convection on the surface of the concrete box girder, resulting in a temperature field that is lower than the actual surface temperature.

[0180] 5. Verification of grid independence of radiation field model.

[0181] Before the thermodynamic analysis, five mesh sizes were also used, and the number of meshes of each size was counted by COMSOL. The specific mesh sizes and numbers are shown in Table 6. The radiation simulation process was performed using COMSOL Multiphysics finite element analysis software, and the calculation included the box beam and the box chamber.

[0182] Table 6 Comparison of grid size, number and error in radiation field analysis

[0183]

[0184] The mesh uses tetrahedral elements and triangular meshes at the thermodynamic boundary. In order to ensure the mesh quality near the flange of the box girder, the model is angularly refined and the maximum growth rate is set to 1.2, such as Fig.14 As shown, (a)-(e) are coarse, coarse, regular, fine, and refined, respectively. Different mesh sizes are used for box beams and box chambers. In COMSOL, several default mesh sizes can be modified to be more refined, thereby customizing 5 mesh sizes (from coarse mesh to fine mesh).

[0185] The errors caused by different mesh divisions are analyzed based on the temperature of the model measurement points, as shown in Figure 15(a)-(b). Figure 15(a) shows the distribution of the calculated values ​​and the measured values, and Figure 15(b) shows the error distribution between the calculated values ​​and the measured values. The bottom plate temperature is affected by the pier, so the root mean square error (RMSE) and mean absolute error (MAE) are statistically analyzed except for the bottom plate position, as shown in Table 6. The error analysis shows that the coarsened and coarser grids match better overall (lower MAE), but the calculated temperature at the top position is quite different from the measured value, while the five grids have similar calculation results at the axil position (y=3000mm). The conventional grid matches the measured value better, and the difference with the finer and refined grids does not exceed 10%. Considering the computational efficiency, it was finally decided to use the conventional size grid for subsequent analysis.

[0186] Materials and initial conditions of this example: The concrete material properties are shown in Table 7, assuming that the concrete is isotropic and the properties are independent of time.

[0187] Table 7 Thermodynamic and physical properties of materials

[0188]

[0189] In order to eliminate the influence of initial conditions on numerical simulation, the calculation time needs to be set 72 hours before the target time. For example, if the day with the maximum ambient temperature difference is August 23, 2022, the initial time needs to be set to 0:00 on August 20, 2022 to eliminate the influence of the assumed initial conditions on the box girder temperature field calculation.

[0190] In the model establishment involved in this embodiment, surface-to-surface radiation includes: When performing bridge temperature field analysis, due to the complexity of surface boundary loads, the mutual radiation between the surfaces of the box girder structure can usually be ignored. The semi-cube method provided by COMSOL can solve the problem of surface-to-surface radiation of the box girder while considering the interaction between the surfaces of the units. The ray tracing method can simulate the solar radiation angle at a specified date, time and geographical location, thereby solving the shading effect problem that needs to be considered in long-term bridge temperature field analysis.

[0191] The hemicube method draws five boundaries around the surface cell of interest and pixelates the boundaries. The surrounding faces are then projected onto the pixelated boundaries and the pixels associated with each face are calculated to determine the radiative heat flux from the surrounding faces and the heat flux radiating to the cell. This operation is repeated for each surface, using quadratic calculations to ensure adequate accuracy.

[0192] The numerical model verification includes temperature verification. Specifically, the temperature calculation analysis of the model is performed on the monitoring results of the day with the maximum temperature difference in the field environment. The changes in the field recorded values ​​and finite element calculated values ​​of the temperature sensors at the 8 measuring points within 24 hours over time are analyzed. A comparative analysis is performed on working condition 1 (the benchmark working condition without considering the actual wind field) and working condition 2 (the temperature field model considering the actual wind field), as shown in Figure 16 (a)-(d), and the errors between the measured temperature values ​​and the finite element calculated values ​​at each measuring point are statistically analyzed, as shown in Table 8. MIN ERROR represents the minimum absolute error, and MAX ERROR represents the maximum absolute error.

[0193] Table 8 Error analysis of temperature field finite element calculation (unit: °C)

[0194]

[0195] The error analysis in Table 8 shows that the maximum absolute errors of working conditions 1 and 2 are 6.60℃ and 2.10℃ respectively, and the average error of working condition 1 varies from 0.29 to 3.14℃, and the average error of working condition 2 varies from 0.02 to 1.21℃. The calculation error of working condition 2 is within the acceptable range. In general, the simulation calculation results of working condition 2 are more accurate, with a 71% decrease in RMSE and a 69% decrease in MAE compared with working condition 1.

[0196] The verification of the numerical model includes the verification of the temperature gradient, which specifically includes: the analysis of the calculation curves in Figure 16 (a)-(d) shows that the calculation results of Condition 1 are lower than the measured values, especially at the top position of the web D on the sunny side (Figure 16 (a)). Therefore, it is necessary to further analyze the temperature distribution obtained by finite element calculation. As shown in Figure 17 (a)-(d), the temperature gradient distribution of each web measured is compared with the temperature gradient obtained by finite element calculation (Condition 1, Condition 2). It can be clearly seen that the calculation results of the reference condition 1 are significantly lower in the temperature gradient distribution. In particular, the temperature gradient calculation at the top position of the sunny side of the web D is lower, and the simulation calculation result is 9.7℃ lower than the measured value, which overestimates the influence of thermal convection on the top plate, resulting in a lower temperature gradient calculation result, and there are safety hazards in the analysis of the actual situation. In contrast, the calculation results of Condition 2 are more consistent with the measured values, and the prediction errors are all within 3℃.

[0197] Previous temperature field studies directly used field tests or meteorological station wind speed monitoring on the bridge structure surface and substituted it into empirical formulas to define thermal convection boundary conditions, and rarely considered the impact of wind on different surfaces of the bridge structure. This embodiment introduces a thermodynamic finite element research framework that considers the actual wind field distribution of a single-box three-chamber concrete box girder, and analyzes the temperature field of the concrete box girder to obtain the following conclusions:

[0198] (1) The CFD simulation results show that the thickness of the thermal boundary layer δ on the outer surface of the box girder structure t The wind speed at the location is generally lower than the incoming wind speed U ∞ , especially on the leeward side. ∞ Under the value, the U i Different values ​​will cause U to appear even on the same surface. i Distribution differences.

[0199] (2) Wind speed on the entire bridge structure surface U i Size and incoming wind speed U ∞ Positive linear correlation. i with U ∞ It is a linear relationship, indicating that the inflow wind speed U ∞ By multiplying it with the pre-calculated wind speed reduction factor μ, the U at any position on the outer surface of the concrete box girder can be easily calculated. i However, wind field simulation shows that the actual wind direction on the upper surface of the box girder top plate and the lower surface of the bottom plate is opposite to the incoming wind direction.

[0200] (3) Directly using the convective heat transfer coefficient calculated using the incoming wind speed will significantly overestimate the incoming wind speed U ∞The influence on the surface of the concrete box girder makes it difficult for the numerical simulation method to obtain the maximum temperature gradient. The absolute size of the bridge has a low impact on the wind field, and only affects the distribution of the wind field on its lower surface at the bottom plate position. When calculating the wind speed reduction coefficient μ, this influence can be ignored compared to the overestimation of the empirical formula. Therefore, when analyzing the wind field on the surface of the box girder structure, in order to obtain the wind speed reduction coefficient μ, a smaller analysis model can be used to reduce the complexity of meshing.

[0201] (4) The wind speed reduction coefficient μ obtained by simulating this embodiment is verified by using 8 temperature measurement points in the box girder temperature field model. The results show that compared with the calculation results of the use condition 1, the RMSE of the use condition 2 is reduced by 71%, and the MAE is reduced by 69%, which has high engineering application value. The calculation results of the web temperature gradient using the reference condition 1 are inconsistent with the actual situation, especially the simulation calculation results of the top measurement point of the web D on the sunny side are 9.7°C lower than the actual measurement, which is unsafe. The calculation results of the condition 2 considering the actual wind field are more consistent with the actual measurement, and the prediction error is within 3°C.

[0202] (5) Combining relevant research and the results of this embodiment, it can be seen that wind speed and wind direction should be considered simultaneously when analyzing the bridge temperature field. In the numerical simulation analysis, it is necessary to consider the incoming wind speed and incoming wind direction at the bridge site and then analyze the actual wind field distribution characteristics of the bridge to weaken the negative impact of regional meteorological conditions differences (caused by different wind conditions) on the prediction effect of the bridge temperature field.

[0203] Example 2

[0204] This embodiment provides a concrete box girder temperature field numerical simulation system, including:

[0205] A model building module is configured to build a temperature field model of a concrete box girder;

[0206] A data acquisition module is configured to acquire ambient temperature, box girder internal temperature, box girder surface temperature, solar radiation and wind speed;

[0207] The module for determining the convective heat transfer coefficient is configured to determine the thickness of the velocity boundary layer at different positions of the outer surface of the box girder according to the incoming wind speed, determine the thickness of the thermal boundary layer on the outer surface of the box girder according to the thickness of the velocity boundary layer, and obtain the convective heat transfer coefficient of the outer surface of the box girder at different incoming wind speeds according to the wind speed, ambient temperature and box girder surface temperature at the thickness of the thermal boundary layer;

[0208] The boundary condition determination module is configured to determine the thermodynamic boundary conditions; wherein the thermal convection boundary conditions are determined according to the convection heat transfer coefficient, the ambient temperature and the internal temperature of the box beam; the thermal radiation boundary conditions are determined according to the solar radiation on the outer surface of the box beam; and the thermal conduction boundary conditions are determined according to the ambient temperature and the surface temperature of the box beam;

[0209] The thermodynamic analysis module is configured to perform temperature field numerical simulation on the temperature field model of the concrete box girder based on thermodynamic boundary conditions to obtain temperature field thermodynamic analysis results.

[0210] It should be noted that the above modules correspond to the steps described in Example 1, and the examples and application scenarios implemented by the above modules and the corresponding steps are the same, but are not limited to the contents disclosed in the above Example 1. It should be noted that the above modules, as part of the system, can be executed in a computer system such as a set of computer executable instructions.

[0211] In further embodiments, there is also provided:

[0212] An electronic device includes a memory and a processor, and computer instructions stored in the memory and executed on the processor, wherein when the computer instructions are executed by the processor, the method described in Embodiment 1 is performed. For the sake of brevity, it will not be described in detail here.

[0213] It should be understood that in this embodiment, the processor may be a central processing unit CPU, and the processor may also be other general-purpose processors, digital signal processors DSP, application-specific integrated circuits ASIC, off-the-shelf programmable gate arrays FPGA or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0214] The memory may include a read-only memory and a random access memory, and provide instructions and data to the processor. A portion of the memory may also include a non-volatile random access memory. For example, the memory may also store information about the device type.

[0215] A computer-readable storage medium is used to store computer instructions, and when the computer instructions are executed by a processor, the method described in Example 1 is completed.

[0216] The method in Example 1 can be directly embodied as a hardware processor, or a combination of hardware and software modules in the processor. The software module can be located in a mature storage medium in the field such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory, or an electrically erasable programmable memory, a register, etc. The storage medium is located in the memory, and the processor reads the information in the memory and completes the steps of the above method in combination with its hardware. To avoid repetition, it is not described in detail here.

[0217] A computer program product includes a computer program, and when the computer program is executed by a processor, the method described in embodiment 1 is implemented.

[0218] The present invention also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product includes computer executable instructions, such as instructions included in a program module, which are executed in a device on a real or virtual processor of the target to perform the process / method as described above. Typically, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform specific tasks or implement specific abstract data types. In various embodiments, the functions of program modules can be combined or divided between program modules as needed. Machine executable instructions for program modules can be executed in local or distributed devices. In distributed devices, program modules can be located in local and remote storage media.

[0219] The computer program code for implementing the method of the present invention can be written in one or more programming languages. These computer program codes can be provided to the processor of a general-purpose computer, a special-purpose computer or other programmable data processing device, so that the program code, when executed by the computer or other programmable data processing device, causes the function / operation specified in the flow chart and / or block diagram to be implemented. The program code can be executed completely on a computer, partially on a computer, as an independent software package, partially on a computer and partially on a remote computer or completely on a remote computer or server.

[0220] In the context of the present invention, computer program codes or related data may be carried by any appropriate carrier to enable a device, apparatus or processor to perform the various processes and operations described above. Examples of carriers include signals, computer readable media, etc. Examples of signals may include electrical, optical, radio, acoustic or other forms of propagation signals, such as carrier waves, infrared signals, etc.

[0221] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with this embodiment can be implemented in electronic hardware or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0222] Although the above describes the specific implementation mode of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A numerical simulation method for temperature field of concrete box girder, characterized in that: include: Construct the temperature field model of concrete box girder; Obtain ambient temperature, box girder internal temperature, box girder surface temperature, solar radiation and wind speed; The velocity boundary layer thickness at different positions on the outer surface of the box girder is determined according to the incoming wind speed, the thermal boundary layer thickness on the outer surface of the box girder is determined according to the velocity boundary layer thickness, and the convective heat transfer coefficient of the outer surface of the box girder under different incoming wind speeds is obtained according to the wind speed, ambient temperature and box girder surface temperature at the thermal boundary layer thickness. Determine the thermodynamic boundary conditions; among which, the thermal convection boundary conditions are determined according to the convection heat transfer coefficient, the ambient temperature and the internal temperature of the box girder; the thermal radiation boundary conditions are determined according to the solar radiation on the outer surface of the box girder; and the thermal conduction boundary conditions are determined according to the ambient temperature and the surface temperature of the box girder; Based on the thermodynamic boundary conditions, the temperature field numerical simulation of the concrete box girder temperature field model was carried out, and the thermodynamic analysis results of the temperature field were obtained.

2. A concrete box girder temperature field numerical simulation method according to claim 1, characterized in that: The convective heat transfer coefficient is: Among them, T A is the ambient temperature, T S is the surface temperature of the box girder; U i is the thickness of the thermal boundary layer δ t The wind speed at the place.

3. A numerical simulation method for temperature field of a concrete box girder according to claim 1, characterized in that: Thermal boundary layer thickness δ t is: t =Pr -1 / 3 δ; where Pr is the Prandtl number and δ is the velocity boundary layer thickness; The velocity boundary layer thickness is: Where α and β are constants that depend on the incoming wind speed; x is the distance from the starting point of the calculation boundary on the box girder surface to the calculation point.

4. A concrete box girder temperature field numerical simulation method as claimed in claim 1, characterized in that: The thermal convection boundary condition is: q c =h c ·(T B -T A );where q c is the heat transfer density of convection; T B is the internal temperature of the box girder; T A is the ambient temperature; h c is the convective heat transfer coefficient.

5. The method for numerically simulating the temperature field of a concrete box girder according to claim 1, characterized in that: The process of determining thermal radiation boundary conditions includes: According to the ambient temperature T A and the box girder surface temperature T S Determine the radiation heat transfer between the outer surface of the box girder and the external environment: ε u is the emissivity of the outer surface of the box beam, β S is the Boltzmann constant; According to the total solar radiation received by the outer surface of the box girder I S Determine the total amount of solar radiation reflected from the ground and the external environment: β G is the reflectivity of the ground and the external environment; δ is the angle between the reflected radiation and the box girder surface; According to the absorption rate of solar radiation by the box girder α and the total solar radiation I received by the outer surface of the box girder S The solar radiation on the outer surface of the box girder is determined by the product of the box girder's absorption rate α and the total amount of solar radiation reflected by the ground and the external environment, and the solar radiation component reflected by the ground and the surrounding environment is determined according to the product of the thermal radiation boundary conditions.

6. A numerical simulation method for temperature field of a concrete box girder according to claim 1, characterized in that: The heat transfer boundary conditions include: First-type boundary condition: The internal temperature of the box girder is set as the first-type boundary condition, denoted as T(Γ,t), i.e., T| Γ1 =T(Γ,t); The second type of boundary condition: n·(k▽T) Γ2 =q s (Γ,t);q S is the solar radiation on the outer surface of the box girder; n is the direction; k is the thermal conductivity; T is the temperature at any point; The third type of boundary condition: n·(k▽T) Γ3 =h c (T A -T S );where h c is the convective heat transfer coefficient; T A is the external environment temperature, T S is the box girder surface temperature.

7. A concrete box girder temperature field numerical simulation system, characterized in that: include: A model building module is configured to build a temperature field model of a concrete box girder; A data acquisition module is configured to acquire ambient temperature, box girder internal temperature, box girder surface temperature, solar radiation and wind speed; The module for determining the convective heat transfer coefficient is configured to determine the thickness of the velocity boundary layer at different positions of the outer surface of the box girder according to the incoming wind speed, determine the thickness of the thermal boundary layer on the outer surface of the box girder according to the thickness of the velocity boundary layer, and obtain the convective heat transfer coefficient of the outer surface of the box girder at different incoming wind speeds according to the wind speed, ambient temperature and box girder surface temperature at the thickness of the thermal boundary layer; The boundary condition determination module is configured to determine the thermodynamic boundary conditions; wherein the thermal convection boundary conditions are determined according to the convection heat transfer coefficient, the ambient temperature and the box beam surface temperature; the thermal radiation boundary conditions are determined according to the solar radiation on the outer surface of the box beam; and the thermal conduction boundary conditions are determined according to the ambient temperature and the box beam surface temperature; The thermodynamic analysis module is configured to perform temperature field numerical simulation on the temperature field model of the concrete box girder based on thermodynamic boundary conditions to obtain temperature field thermodynamic analysis results.

8. An electronic device, characterized in that: The method comprises a memory and a processor and computer instructions stored in the memory and executed on the processor, wherein when the computer instructions are executed by the processor, the method according to any one of claims 1 to 6 is completed.

9. A computer-readable storage medium, characterized in that: Used to store computer instructions, which, when executed by a processor, complete the method described in any one of claims 1 to 6.

10. A computer program product, characterized in that The invention comprises a computer program, which, when executed by a processor, implements the method according to any one of claims 1 to 6.

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