Xiao Sun¹, Jiangbo Tong¹, Yuliang Zhang^2,*, Haibing Cai³, Wen Zhou⁴, Xiaoqi Jia⁵, Litao Ou⁶

FDMP-Fluid Dynamics & Materials Processing, Vol., , DOI:10.32604/fdmp.2023.045541

Abstract Centrifugal pumps are widely used in the metallurgy, coal, and building sectors. In order to study the hydraulic characteristics of a closed impeller centrifugal pump during its shutdown in the so-called power frequency and frequency conversion modes, experiments were carried to determine the characteristic evolution of parameters such as speed, inlet and outlet pressure, head, flow rate and shaft power. A quasi-steady-state method was also used to further investigate these transient behaviors. The results show that, compared to the power frequency input, the performance parameter curves for the frequency conversion input are less volatile and smoother. The characteristic time is… More >

Teng Teng^1,2, Yuhe Cai³, Linchao Wang^3,*, Yanzhao Zhu²

FDMP-Fluid Dynamics & Materials Processing, Vol., , DOI:10.32604/fdmp.2023.044532

Abstract Liquid nitrogen has shown excellent performances as a good fracturing medium in the extraction of unconventional natural gas, and its application in coalbed methane extraction is currently a research hotspot. This study focuses on the acoustic emission properties of coal specimens treated utilizing liquid nitrogen with varying initial temperatures in a three-point bending environment. Through examination of the load-displacement curves of the considered coal samples, their mechanical properties are also revealed for different initial temperatures and cycling frequencies. The findings demonstrate a gradual decline in the maximum load capacity of coal rock as the temperature rises. Similarly, when subjected to… More >

Xiaohui Wang^1,2,3,*, Kai Zhang¹, Xiaobang Bai⁴, Senchun Miao¹, Zanxiu Wu¹, Jicheng Li¹

FDMP-Fluid Dynamics & Materials Processing, Vol., , DOI:10.32604/fdmp.2023.043272

Abstract This study focuses on a DN50 pipeline-type Savonius hydraulic turbine. The torque variation of the turbine in a rotation cycle is analyzed theoretically in the framework of the plane potential flow theory. Related numerical simulations show that the change in turbine torque is consistent with the theoretical analysis, with the main power zone and the secondary power zone exhibiting a positive torque. In contrast, the primary resistance zone and the secondary resistance zone are characterized by a negative torque. Analytical relationships between the turbine’s internal flow angle θ, the deflector’s inclination angle α0, and the coverage angle α of the… More >

Jianlong Jin, Jingjing Ding, Long Xiong, Ming Bao, Peng Zeng^*

FDMP-Fluid Dynamics & Materials Processing, Vol., , DOI:10.32604/fdmp.2023.027311

Abstract The effects of different contents of a MgO expansive agent and phosphorus slag on the mechanical properties, shrinkage behavior, and the heat of hydration of concrete were studied. The slump flow, setting time, dry shrinkage, and hydration heat were used as sensitive parameters to assess the response of the considered specimens. As shown by the results, in general, with an increase in the phosphorus slag content, the hydration heat of concrete decreases for all ages, but the early strength displays a downward trend and the dry shrinkage rate increases. The 90-d strength and dry shrinkage of concrete could be improved… More >

He Wang^1,*, Ying He²

FDMP-Fluid Dynamics & Materials Processing, Vol., , DOI:10.32604/fdmp.2023.042728

Abstract Magnetohydrodynamic (MHD) induction pumps are contactless pumps able to withstand harsh environments. The rate of fluid flow through the pump directly affects the efficiency and stability of the device. To explore the influence of induction pump settings on the related delivery speed, in this study, a numerical model for coupled electromagnetic and flow field effects is introduced and used to simulate liquid metal lithium flow in the induction pump. The effects of current intensity, frequency, coil turns and coil winding size on the velocity of the working fluid are analyzed. It is shown that the first three parameters have a… More >

Ran Wang¹, Aimin Gong^1,*, Shanqing Shao¹, Baoli Qu², Jing Xu³, Fulai Wang¹, Feipeng Liu^3,*

FDMP-Fluid Dynamics & Materials Processing, Vol., , DOI:10.32604/fdmp.2023.042566

Abstract The mechanical properties of cementitious sand and gravel damming material have been experimentally determined by means of microscopic SEM (Scanning Electron Microscopy) image analysis. The results show that the combination of fly ash and water can fill the voids in cemented sand and gravel test blocks because of the presence of hydrated calcium silicate and other substances; thereby, the compactness and mechanical properties of these materials can be greatly improved. For every 10 kg/m³ increase in the amount of cementitious material, the density increases by about 2%, and the water content decreases by 0.2%. The amount of cementitious material used… More >

Yan Liu¹, Tianli Sun², Bencheng Wang^1,*, Yan Feng²

FDMP-Fluid Dynamics & Materials Processing, Vol., , DOI:10.32604/fdmp.2023.041852

Abstract A numerical model of hydraulic fracture propagation is introduced for a representative reservoir (Yuanba continental tight sandstone gas reservoir in Northeast Sichuan). Different parameters are considered, i.e., the interlayer stress difference, the fracturing discharge rate and the fracturing fluid viscosity. The results show that these factors affect the gas and water production by influencing the fracture size. The interlayer stress difference can effectively control the fracture height. The greater the stress difference, the smaller the dimensionless reconstruction volume of the reservoir, while the flowback rate and gas production are lower. A large displacement fracturing construction increases the fracture-forming efficiency and… More >

Lian Liu^1,2, Liang Li^1,2, Kebo Jiao^1,2,*, Junwei Fang^1,2, Yun Luo^1,2

FDMP-Fluid Dynamics & Materials Processing, Vol., , DOI:10.32604/fdmp.2023.030109

Abstract Ultra-deep reservoirs play an important role at present in fossil energy exploitation. Due to the related high temperature, high pressure, and high formation fracture pressure, however, methods for oil well stimulation do not produce satisfactory results when conventional fracturing fluids with a low pumping rate are used. In response to the above problem, a fracturing fluid with a density of 1.2~1.4 g/cm³ was developed by using Potassium formatted, hydroxypropyl guanidine gum and zirconium crosslinking agents. The fracturing fluid was tested and its ability to maintain a viscosity of 100 mPa.s over more than 60 min was verified under a shear… More >

Fei Wang, Qinpeng Meng, Jinchi Zhao, Xin Wang, Yuhong Liu, Qianru Zhang^*

FDMP-Fluid Dynamics & Materials Processing, Vol., , DOI:10.32604/fdmp.2023.026917

Abstract Buildings with large open spaces in which chemicals are handled are often exposed to the risk of explosions. Computational fluid dynamics is a useful and convenient way to investigate contaminant dispersion in such large spaces. The turbulent Schmidt number (Sc_t) concept has typically been used in this regard, and most studies have adopted a default value. We studied the concentration distribution for sulfur hexafluoride (SF₆) assuming different emission rates and considering the effect of Sc_t. Then we examined the same problem for a light gas by assuming hydrogen gas (H₂) as the contaminant. When SF₆ was considered as the contaminant… More >

Tian Li^1,2,*, Hao Liang¹, Zerui Xiang², Jiye Zhang¹

FDMP-Fluid Dynamics & Materials Processing, Vol., , DOI:10.32604/fdmp.2023.043618

Abstract A relatively high aerodynamic drag is an important factor that hinders the further acceleration of high-speed trains. Using the shear stress transport (SST) k-ω turbulence model, the effect of various vortex generator types on the aerodynamic characteristics of an ICE2 (Inter-city Electricity) train has been investigated. The results indicate that the vortex generators with wider triangle, trapezoid, and micro-ramp arranged on the surface of the tail car can significantly change the distribution of surface pressure and affect the vorticity intensity in the wake. This alteration effectively reduces the resistance of the tail car. Meanwhile, the micro-ramp vortex generator with its… More > Graphic Abstract