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Copyright of Study on Optical Communications / Guangtongxin Yanjiu is the property of Study on Optical Communications Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

【Objective】In order to study the temperature distribution and airflow requirements of high-speed optical modules, aiming to optimize the heat dissipation design and ensure the stable operation of optical modules.【Methods】The article adopts Flotherm simulation analysis to establish the numerical wind tunnel model of the optical module. The temperature distribution of each component during normal operation is obtained. The working air flow of the fan is also obtained when the system is stabilized, which are in line with the heat dissipation requirements in the specification of Multi-Source Agreement (MSA). In order to facilitate the testing and installation, the ”L” type wind tunnel fixture is designed. The actual surface temperature of each chip and the actual working wind flow rate of the wind tunnel are tested experimentally to verify the accuracy of the simulation results.【Results】The results show that in the case of the maximum temperature of 70 ℃, for the surface temperature of each chip, the difference between the simulation and the measured temperature is less than 2 ℃, with an error of less than 5%. For the airflow rate required for the heat dissipation of the entire optical module, the difference between the simulation and measured results is 0.2 Cubic Feet per Minute (CFM), with an error within 7%.【Conclusion】It can be shown that the simulation and measurement methods are feasible and the error is small, which provides an important reference value in the design and testing of heat dissipation of high-speed optical modules.

Large silo shell grids are used in a large number of coal storage sheds in power plants and other industries, where holes are cut in the ends as required by the process. Numerical wind tunnel analysis for the static wind effects of these semi-open structures are carried out by using the wind engineering calculation function of FLUENT. Based on the secondary development of the STADS and FLUENT interface program, the model conversion and the automatic reading and loading of wind pressure are completed through menu operation and parameter control, and the running speed of the program is optimized. With a dry coal shed in Bangladesh with an open upper section and a steel mill in India with an open lower section as research subjects, the wind pressure coefficients and wind speed vectors for different wind angles are given considering the combined effect of internal and external wind pressure. According to the wind pressure distribution law and the wind pressure similar partitioning criterion, the internal and external wind pressure partitioning body type coefficients of the upper and lower semi-open silo shell grids are provided, and the calculation results can be provided as reference for the structural design of similar structural projects. [ABSTRACT FROM AUTHOR]

In order to clarify the wind-induced vibration response law of variable cross-section cylindrical shell steel tower, a finite element calculation model based on fluid-structure coupling theory was established. The fluctuating wind speed corresponding to the basic wind pressure in different return periods was simulated by autoregressive model(AR) method. The numerical wind tunnel method was successfully used to calculate the dynamic response of variable cross-section cylindrical shell steel tower under the fluctuating wind. At the same time, the reliability of the numerical results was verified by field wind vibration monitoring. The results show that the displacement response amplitude gradually increases along the height direction under the action of fluctuating wind. The greater the wind speed, the greater the displacement response of the structure. However, the difference between the structural response under the wind speed of 50-year and 100-year return period is not very large, but it does not exceed the displacement limit of the structure. The stress decreases gradually along the height direction, and there is a sudden change of stress at the position of the variable section. The greater the wind speed is, the greater the stress is, and the difference of stress along the height direction is smaller and smaller. Under the action of wind speed in 50-year and 100-year return period, the allowable material stress value of desulfurization tower under working temperature exceeds 113 MPa. Therefore, for the evaluation of wind resistance performance of this kind of steel tower, stress control is mainly used at the bottom and variable section, and displacement control is mainly used at the top. [ABSTRACT FROM AUTHOR]

In order to study the two-dimensional vortex-induced vibration of streamlined box girder of Changshan Bridge, based on the method of numerical wind tunnel, Gambit was used to establish the flow field of bridge section and divide the grid. The vortex-induced vibration model of bridge section was simplified to a vertical single-degree-of-freedom spring system and solved. The results of study show that the vortex of streamlined box girder is generated at the wind inlet of the bridge section, and gradually moves to the tail of the section through the upper section of the bridge, and falls off in the tail flow of the section. The converted wind speed that is easy to cause vortex-induced vibration is 8~20. The research conclusions provide reference for the prevention of vortex-induced resonance and vortex-induced vibration emergency treatment of bridges. [ABSTRACT FROM AUTHOR]

For acquisition of accurate aerodynamic parameters of the pipeline suspension bridge, the numerical wind tunnel model for the typical girder section of the oil and gas pipeline suspension bridge was built, and SST k-ε model was used as the numerical wind tunnel turbulence model. The bypass flow pressure field distribution acquired from the numerical wind tunnel shows that the negative pressure area on the upper and lower surfaces of the pipeline is obvious, the largest positive pressure area appears on the windward side of the pipeline, and the pressure difference between the windward side and the leeward side of the truss girder in the inflow direction is particularly obvious. The bypass flow velocity field distribution shows that the pipeline and truss girder exert significant blocking effect on the wind speed, and the flow separation and vortex shedding phenomena occur apparently on the pipeline, windward railings and truss girder. According to the root mean square pressure of the flow field, vortex vibration is most likely to occur in the inflow side truss. Through the analysis of the three component coefficients of different pipeline diameters and different girder widths at the wind attack angles of －3°, 0° and 3°, it is concluded that the girder width has little influence on resistance coefficient and lift coefficient, and the torsion coefficient decreases with the increase of the girder width at －3° wind attack angle. The pipeline diameter definitively influences the three component coefficients, that is, with the increase of pipeline diameter, the resistance coefficient increases gradually, while the lift coefficient and torsion coefficient decrease gradually. The research results are expected to provide wind-resistant data support for the design of suspension bridge deck structure and the piping layout.

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Wind-induced interference effect commonly occurs among arched plastic greenhouse group. To describe such influence and finally determine the wind load shape coefficients considering the interference effects, we conducted a series of numerical simulations based on computational fluid dynamics (CFD). Combining the Reynolds-averaged N-S equations and the Realizable k-ε turbulence model, the surface wind pressure characteristics of the models for single greenhouse and greenhouse group under different wind direction angles and distances were studied separately. In combination with the actual production, 5 rows and 6 columns symmetrical layout was adopted as the greenhouse group’s model with different gap distances (2, 4, 6, 8, 10 and 12 m) and wind direction angles (0, 30, 45, 60 and 90 degrees). In order to achieve quantitative analysis of the wind-induced interference effects, the interference factor was introduced in this paper as an important contrast parameter. According to the characteristics of the greenhouse structure, the greenhouse partition was reasonably set to realize the key research of wind pressure characteristics in wind-sensitive areas. In the numerical wind tunnel simulation, unstructured grids suitable for greenhouse group’s model were used to divide the computational domain. The calculation parameters such as blocking ratio, inlet and outlet conditions, and near-wall treatments and so on were appropriately set. By comparing with wind tunnel test results of similar models, the present numerical simulations were verified. According to the simulation results, the arrangement of greenhouse group causes the wind-induced interference effects, which will change wind pressure characteristics of the greenhouses. The effects can result in amplification effects (the outer area of the greenhouse group) and the shielding effects (the middle area of the greenhouse group), among which the amplification effects threatens the safety of the structure and cannot be ignored. The interference effects is significantly affected by the wind direction angle and the gap distance, and specifically it decreases with the increase of distance, and tends to be stable when the distance between greenhouses is about 10 m. Based on the analysis of the variation law of the mean wind pressure coefficients and wind direction angles on the greenhouse group’s roofs, it is obvious that the interference effects weakens the wind pressure ventilation ability of the greenhouse group as a whole. From the point of view of advantageous to wind pressure ventilation, the suggestions on planning and layout of the greenhouse group are put forward, that is, the long axis direction of the greenhouses should be perpendicular to the dominant wind direction in summer of the area where the greenhouse group is located and the gap distance should be increased appropriately. Finally, according to the wind-induced interference effects, the wind load shape coefficients for arched plastic greenhouses (the rise-span ratio is 3:8) are given, which are convenient for design. The wind load shape coefficients of greenhouses which are located in the outer area of the greenhouse group: At 0 wind direction angle, +0.41 on the windward side, -0.78 on the middle roof, -0.26 on the leeward side and -0.48 on both sides of gables; at 90 degrees wind direction angle, +0.36 on the windward gable, -0.44 on the roof. The wind load shape coefficients of greenhouses which are located in the middle area of the greenhouse group: At 0 wind direction angle, +0.30 on the windward side, -0.71 on the middle roof, -0.26 on the leeward side and -0.48 on both sides of gables; at 90 degrees wind direction angle, +0.34 on the windward gable, -0.35 on the roof. Wind-induced interference effects exists in arched plastic greenhouses arranged in group, and wind pressure changes on the greenhouses caused by wind-induced interference effects should be considered in design. [ABSTRACT FROM AUTHOR]