Gongcheng Kexue Yu Jishu/Advanced Engineering Science

With the development of computer technology, grid division technology is becoming more mature. Considering the frequent occurrence of floods due to climate change, the broad extents of calculation domains, the wide range of actual terrain, and the study area usually has narrow and long gullies and wide flooding areas, this paper proposes a structured non-uniform grid model with hierarchical topological relationships combined with a high-resolution model based on GPU acceleration to simulate the surface water flow process. High-quality grids affect the calculation accuracy and efficiency of the model. The principle of grid division is designed based on the gradient change of terrain elevation, and key terrain features are detected in the computational domain that requires high-resolution grids to reliably solve shallow water equations. Moreover, local area grids can be statically encrypted, so that the sensitive area of the water level calculation can be captured more accurately, while reducing the number of calculation grids and reducing the calculation cost. The numerical model adopts Godunov-type finite volume method for spatial discretization, uses the second-order TVD-MUSCL format to improve the temporal and spatial accuracy of the model, and uses GPU parallel technology to greatly increase the running speed of the model without reducing the calculation accuracy. The performance of high-resolution models on non-uniform grids is demonstrated by the more accurate simulation of flood inundation time and inundation area through ideal and practical cases. The results show that the numerical model based on the non-uniform grid has good stability, compared with the uniform grid, its running speed is about 2-3 times under the premise of ensuring the simulation accuracy and the efficiency is further improved on the basis of GPU acceleration. The new model is suitable for simulating large-scale flood evolution and urban inundation processes in complex areas, which has good potential in actual large-scale flood simulation.

Urban and rural mixed organic waste, including perishable waste and partial agricultural waste, are high yield, complex composition, high water content and nutrient content. Aerobic fermentation is one of the key technologies for the utilization of this resource, but the application is limited in China due to the low conversion efficiency and unknown risk of by-products. Therefore, in view of the bottleneck problem of aerobic fermentation of organic waste in China, the resource utilization technologies of urban and rural mixed organic waste were compared and analyzed, the advantages of aerobic fermentation in the treatment of organic solid waste was clarified, the transformation mode of organic matter in the process of aerobic fermentation was deeply analyzed, and the main problems faced by aerobic fermentation in the treatment of organic waste was revealed. Accordingly, the main factors affecting the efficient stabilization and resource utilization of aerobic fermentation products was further identified. The concept of rapid stabilization and resource utilization of urban and rural mixed organic waste, named as detecting the regulation principle of microbial metabolic network during organic waste aerobic fermentation, was proposed. Meanwhile, intelligent integrated rapid stabilization technology and equipment (intelligent screen display-online monitoring-feedback control) was also developed overcome the technology of directional humification and pollution enhancement in microbial factory, the technology of deep processing-quality evaluation- attribute complementary of resource products to utilize resource products by their characteristics was constructed. In order to provide technical support for the resource treatment of urban and rural mixed organic waste in China, researches and demonstration projects will be carried out to meet the major needs of national science and technology, such as in-situ reduction of organic waste by aerobic fermentation, pollution control in the process, and resource utilization of the end products.

When Levy type rigid bracing dome is impacted by unexpected load, its structure may collapse continuously, resulting in property loss and casualties, therefore, it is necessary to analyze its progressive collapse performance. According to characteristics of rigid bracing dome, the threshold coefficients of members and its calculation formula were given, and the discriminant criteria and types of progressive collapse were proposed. Damage coefficient based on response difference was proposed, and importance coefficient of members was given. Member importance of levy type rigid bracing dome were analyzed and sorted based on importance coefficient of members. Based on the discriminant criteria of progressive collapse and the results of importance analysis of members, the method and process of progressive collapse analysis were proposed. Progressive collapse performance of structure was analyzed. The influence of both rise span ratio and initial prestress on the progressive collapse performance was discussed. The method of progressive collapse resistance against rigid bracing dome was proposed. The research showed that the progressive collapse types of levy type rigid bracing dome could be divided into non collapse, local collapse and overall collapse. The outer ring bar obtains the largest importance coefficient, followed by the inner ring bar. The smaller rise span ratio is or the larger the initial prestress, the smaller importance of the member will be. When the outer ring member, inner ring member or node is damaged, the structure will collapse continuously, while other members will not collapse. Strengthening the joints and ring members can improve resistance of structure against progressive collapse.

In order to study the interlaminar mechanical behavior of regenerated composite pipes with thin-walled lining, tangential and normal tensile failure tests are carried out on the composite pipes with corroded defects and thin-walled stainless steel lining. Based on the test results, a finite element analysis model is established for the repaired pipes with corroded defects. The test results of test specimen under the effect of tangential force show that with the increase of pipe steel corrosion extent with corrosion defects, bonding layer and the base pipe steel strip gradually decreases, the ultimate strength of the interface between the layers increase gradually, and with the increase of the corrosion loss rates, the interface cohesive force has a slight increase. But with the increase of proportion of binding material failure, this increased trend gradually flatten out. The tangential failure of interlayer interface is mainly due to the failure of cohesive force of binder. The test results under normal force show that the failure modes of each specimen are basically the same, and the failure is mainly the failure of cohesive force of the bonding layer. A bilinear constitutive model of tangential stress and relative displacement at interlayer interface of composite pipes is established by difference method. The relation between normal stress and relative displacement at interlayer interface can also be simplified to bilinear constitutive relation. The finite element analysis model is used to analyze the specimen, and the analysis results are in good agreement with the test results. The bilinear interfacial cohesive force model can accurately simulate the interlaminar mechanical properties of thin-walled composite pipes in the finite element model analysis. The research content and results can provide a theoretical basis for the trenchless continuous lining repair technology of buried pipeline.

Progressive cavity pumps (PCP), which uses the ordinary nitrile rubber, are widely used in heavy oil production, and it is prone to failure of the core-burning perforation of the stator bushing. The expensive hydrogenated nitrile rubber is resistant to high temperatures but does not have precise use depth and cross-sectional parameters. In order to solve above problems, first of all, the rubber hyperplastic constitutive model of ordinary nitrile rubber and hydrogenated nitrile rubber is fitted based on the thermal aging and tensile tests. And then, a new finite element model is established based on the one-way decoupling method to decompose the delayed heat generation phenomenon. Finally, the influences of working well depth, interference, and wall thickness on the lagging heat generation are studied, and the orthogonal table of the three factors is listed. The research results show that ordinary nitrile rubber is better than hydrogenated nitrile in working temperature below 70 ℃ (corresponding to the working depth of 1 667 m), but it will suffer serious aging in the deep working temperature or the high temperature environment, which is the main reason for core burn and perforation failure in current applications. Hydrogenated nitrile rubber begins to age at a working temperature of 150 ℃ (corresponding to the working depth of 4 333 m), which is more stable than ordinary nitrile in mechanical properties, so it is reliable. Due to liquid column pressure and rubber aging, the maximum stress between the bushing and the rotor is decreases first and then increases with the increase of working depth. With the increase of the interference, the sealing performance of the PCP improves, and the maximum temperature of the sleeve section increases exponentially. For every 2 mm increase in the thickness of the rubber bushing, the true displacement of the inner wall increases by 0.059～0.067 mm on average, corresponding to the growth rate of 19%～28%. It is concluded that the working depth of 1 667 m is the boundary between the two types of rubber PCP. The interference is the minimum value of 0.5 mm, and the maximum wall thickness is 12 mm under the condition of no leakage. The research results provide theoretical support for reasonably matching the parameters of the stator rubber bushing, which optimizing the stator rubber material, and improving the working performance of the PCP throughout the life cycle.