The performance of sewer network is associated with both clean water infiltration and in-sewer pollutant degradation.Quantifying their contributions in large-scale sewer network remains challenging due to the infeasib...The performance of sewer network is associated with both clean water infiltration and in-sewer pollutant degradation.Quantifying their contributions in large-scale sewer network remains challenging due to the infeasibility of numerous on-site measurements of water flows and water quality concentrations in the whole system.This study developed a physically inverse problem approach to address this challenge,which was tested in an actual sewer network system(25.66 km^(2))with gridding-based in-sewer flow rate and water quality measurements.Bayesian optimization framework was integrated into sewer hydrodynamic and water quality models to inversely estimate source parameters including source flow rates and source discharge concentrations.Employing simulated annealing algorithm can demonstrate 20.6%-54.2% higher accuracy compared with the other methods,due to its progressive instead of fast and steep convergence toward the true solutions.With the developed approach,the infiltrated clean water infiltration and mass loss of chemical oxygen demand(COD)within the sewer network were quantified synchronously.Further,the condition of sewer structural defects was assessed,and a reference value for allowable in-sewer COD degradation was also presented,which was 4%-5%COD mass per hour of sewage hydraulic retention.Therefore,this methodology can provide cost-effective solution for comprehensive assessment of sewer network conditions.展开更多
By using the Finite Element Inverse Approach based on the Hill quadratic anisotrop-ically yield criterion and the quadrilateral element, a fast analyzing software-FASTAMP for the sheet metal forming is developed. The ...By using the Finite Element Inverse Approach based on the Hill quadratic anisotrop-ically yield criterion and the quadrilateral element, a fast analyzing software-FASTAMP for the sheet metal forming is developed. The blank shapes of three typical stampings are simulated and compared with numerical results given by the AUTOFORM software and experimental results, respectively. The comparison shows that the FASTAMP can predict blank shape and strain distribution of the stamping more precisely and quickly than those given by the traditional methods and the AUTOFORM.展开更多
As an advanced near-net shape technology, squeeze casting is an excellent method for producing high integrity castings. Numerical simulation is a very effective method to optimize squeeze casting process, and the inte...As an advanced near-net shape technology, squeeze casting is an excellent method for producing high integrity castings. Numerical simulation is a very effective method to optimize squeeze casting process, and the interfacial heat transfer coefficient(IHTC) is an important boundary condition in numerical simulation. Therefore, the study of the IHTC is of great significance. In the present study, experiments were conducted and a "plate shape" aluminum alloy casting was cast in H13 steel die. In order to obtain accurate temperature readings inside the die, a special temperature sensor units(TSU) was designed. Six 1 mm wide and 1 mm deep grooves were machined in the sensor unit for the placement of the thermocouples whose tips were welded to the end wall. Each groove was machined to terminate at a particular distance(1, 3, and 6 mm) from the front end of the sensor unit. Based on the temperature measurements inside the die, the interfacial heat transfer coefficient(IHTC) at the metal-die interface was determined by applying an inverse approach. The acquired data were processed by a low pass filtering method based on Fast Fourier Transform(FFT). The feature of the IHTC at the metal-die interface was discussed.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2021YFC3200703)the Research Program of China Three Gorges Corporation(Grant No.202403181)the National Natural Science Foundation of China(Grant No.52170103).
文摘The performance of sewer network is associated with both clean water infiltration and in-sewer pollutant degradation.Quantifying their contributions in large-scale sewer network remains challenging due to the infeasibility of numerous on-site measurements of water flows and water quality concentrations in the whole system.This study developed a physically inverse problem approach to address this challenge,which was tested in an actual sewer network system(25.66 km^(2))with gridding-based in-sewer flow rate and water quality measurements.Bayesian optimization framework was integrated into sewer hydrodynamic and water quality models to inversely estimate source parameters including source flow rates and source discharge concentrations.Employing simulated annealing algorithm can demonstrate 20.6%-54.2% higher accuracy compared with the other methods,due to its progressive instead of fast and steep convergence toward the true solutions.With the developed approach,the infiltrated clean water infiltration and mass loss of chemical oxygen demand(COD)within the sewer network were quantified synchronously.Further,the condition of sewer structural defects was assessed,and a reference value for allowable in-sewer COD degradation was also presented,which was 4%-5%COD mass per hour of sewage hydraulic retention.Therefore,this methodology can provide cost-effective solution for comprehensive assessment of sewer network conditions.
基金Project supported by the National Natural Sciences Foundation of China(No. 50335060).
文摘By using the Finite Element Inverse Approach based on the Hill quadratic anisotrop-ically yield criterion and the quadrilateral element, a fast analyzing software-FASTAMP for the sheet metal forming is developed. The blank shapes of three typical stampings are simulated and compared with numerical results given by the AUTOFORM software and experimental results, respectively. The comparison shows that the FASTAMP can predict blank shape and strain distribution of the stamping more precisely and quickly than those given by the traditional methods and the AUTOFORM.
基金supported by the National Science and Technology Major Project of China(2017ZX04080001)the National Key Research and Development Program of China(2016YFB0701204)
文摘As an advanced near-net shape technology, squeeze casting is an excellent method for producing high integrity castings. Numerical simulation is a very effective method to optimize squeeze casting process, and the interfacial heat transfer coefficient(IHTC) is an important boundary condition in numerical simulation. Therefore, the study of the IHTC is of great significance. In the present study, experiments were conducted and a "plate shape" aluminum alloy casting was cast in H13 steel die. In order to obtain accurate temperature readings inside the die, a special temperature sensor units(TSU) was designed. Six 1 mm wide and 1 mm deep grooves were machined in the sensor unit for the placement of the thermocouples whose tips were welded to the end wall. Each groove was machined to terminate at a particular distance(1, 3, and 6 mm) from the front end of the sensor unit. Based on the temperature measurements inside the die, the interfacial heat transfer coefficient(IHTC) at the metal-die interface was determined by applying an inverse approach. The acquired data were processed by a low pass filtering method based on Fast Fourier Transform(FFT). The feature of the IHTC at the metal-die interface was discussed.
