摘要 :
With the rapid development of utility tunnel in the world, the types and capacity of it in urban underground utility tunnel are becoming very large, and the traditional approach can not meet the needs of development. In order to m...
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With the rapid development of utility tunnel in the world, the types and capacity of it in urban underground utility tunnel are becoming very large, and the traditional approach can not meet the needs of development. In order to make rational use of underground space and solve the problem of laying underground structure in cities, the state has vigorously promoted the construction of utility tunnel. The utility tunnel refers to the public facilities which are built underground and used for centralized laying of municipal utility tunnel in accordance with unified planning, design, construction and maintenance. So far, China has more than 69 city in the construction of utility tunnel, many scholars have conducted research on seismic of utility tunnel, but most of the studies are based on the homogeneous soil without considering the non-uniformity of soil, in fact the place where the condition of geological change greatly is damaged badly of the underground structure, such as the boundary of hard soil and soft soil. Because of the difference of soil mass will produce large relative displacement at the boundary under the action of earthquake, which will cause the structure to be destroyed easily. In this thesis, the ABAQUS finite element software is used to simulate the response characteristics of the utility tunnel under the action of transverse and longitudinal earthquakes. The main research contents of this thesis are as follows:
Introduces the utility tunnel advantages; summarizes the development and seismic research status of utility tunnel at home and abord; summarizes the main content and significance of this study. Discussion several key theories of utility tunnel ABAQUS software modeling, including: the constitutive model of soil, concrete damage plasticity model, the establishment of artificial boundary conditions, the interaction between soil and utility tunnel and the method of ground motion input, in the end, the artificial boundary conditions have been tested and verified. By using the numerical simulation, analyzed the response of utility tunnel in the inhomogeneous field under transverse seismic excitation. The acceleration response law of soil mass, the interaction of soil and utility tunnel, the acceleration response rule of utility tunnel and the law of displacement and stress change in utility tunnel are studied systematically.
By using the numerical model, analyzed the response of utility tunnel in the inhomogeneous field under longitudinal seismic excitation. The acceleration response law of soil mass, the interaction of soil and utility tunnel, the acceleration response rule of utility tunnel and the law of displacement and stress change in utility tunnel are studied systematically.
Finally, the seismic response of the utility tunnel is summarized, which provides a basis for seismic design of the utility tunnel in the inhomogeneous field.
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摘要 :
The stability of the flow under the magnetic force is a special problem in fluid mechanics.The investigation of flow of fluids in ducts, diffusers and also other parts of various machines in the existence of the magnetic field is ...
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The stability of the flow under the magnetic force is a special problem in fluid mechanics.The investigation of flow of fluids in ducts, diffusers and also other parts of various machines in the existence of the magnetic field is important for many technological processes.In this thesis, the influence of magnetic force on the flow stability in rectangular duct, diffuser, and an airfoil has been studied and the energy gradient theory is used to provide the theoretical analysis of the stability of the magnetohydrodynamics (MHD) flow.
In the first part of this thesis, the flow in a rectangular duct with different Hartmann (Ha) number is simulated.The SIMPLE algorithm and the finite volume method are used to solve a system of equations and then the energy gradient theory is used to study the (associated) stability
of MHD flow.According to the energy gradient theory, in pressure driven flow, K represents the ratio of energy gradient in the transverse direction and the energy loss due to viscosity in streamline direction.Position with large value of K will lose its stability earlier than that with
small value of K.The flow stability of MHD flow for different Hartmann (Ha) number, from Ha=1 to 40, at the fixed Reynolds number, Re=190 are investigated.The simulation is validated firstly against the simulation in literature.The results show that, with the increasing Ha number, the centerline velocity of the rectangular duct with MHD flow decreases and the absolute value of the gradient of total mechanical energy along the streamwise direction increases.The maximum of K appears near the wall in both the coordinate axis of the duct.From the energy gradient theory, this position of the maximum of K would initiate flow instability (if any) more than the other positions.The higher the Hartmann number is, the smaller the K value becomes, which means that the fluid becomes more stable in the presence of higher magnetic force.As the Hartmann number increases, the K value in the parallel layer decreases more significantly than in the
Hartmann layer.The most dangerous position of instability tends to migrate towards the wall of the duct as the Hartmann number increases.Thus, with the energy gradient theory, the stability or instability in the rectangular duct can be controlled by modulating the magnetic force.
In the second part of this thesis, the flow in a diffuser with different Hartmann (Ha) number is simulated.The SIMPLE algorithm and the finite volume method are used to solve a system of equations and then the energy gradient theory is used to study the (associated) stability of magnetohydrodynamics (MHD).The flow stability of MHD flow for different Hartmann (Ha) number, from Ha=0.5 to 2, at the fixed Reynolds number, Re=114 are investigated.The results show that, with the increasing Ha number, the centerline velocity of the diffuser with MHD flow decreases and the vortices in the boundary layer is suppressed.The maximum of K appears near the wall of the diffuser in the y-axis direction.As the Hartmann number increases, the K value near the wall in the y-axis direction decreases significantly.Thus, with the energy gradient theory, the stability or instability in the diffuser can be controlled by modulating the magnetic force.
In the third part of this thesis, the flow around the NACA 0012 airfoil at an angle of attack (AOA) of 7° with different Hartmann (Ha) number is simulated.The SIMPLE algorithm and the finite volume method are used to solve a system of equations and then the energy gradient theory
is used to study the (associated) stability of magnetohydrodynamics (MHD) flow.The flow stability of MHD flow for different Hartmann (Ha) number, from Ha=0.01 to 4, at the fixed Reynolds number, Re=1×105 are investigated.The results show that, with the increasing Ha number from Ha=0.01 to 0.5, the vortex in the trailing edge is suppressed and eventually the
vortex disappeared.The increasing magnetic force pushes the fluid flow in the boundary layer which helps the vortex development and helps it to disappear.The influence of magnetic force becomes larger after increasing the Hartmann number from Ha=0.5 to Ha=4, which changes the flow direction and makes the flow become more unstable.Thus from Ha=0.01 till Ha=0.5, the magnetic force plays a good role for the flow stability.As the Hartmann number increases, the K value in the boundary layer decreases more significantly than the outside of the boundary layer, which makes the fluid flow more stable.Therefore, with the energy gradient theory, the stability
or instability of flow around the airfoil can be controlled by modulating the magnetic force.
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摘要 :
The physics of fluid flow deviate from conventional law in low permeability reservoirs because of small pore size，fine throat，high filtration resistance，which results in high injection pressure，low injection capacity，thus low...
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The physics of fluid flow deviate from conventional law in low permeability reservoirs because of small pore size，fine throat，high filtration resistance，which results in high injection pressure，low injection capacity，thus low production with rapid decline. The reservoir heterogeneity i.e.，the presence of high permeable layers and natural fractures within the strata adds another challenges，which in later stage of water flooding turned out to be so called“water channel”，an easy pathway for the circulation of injected water，thus production wells suffering high watercut and rapid decline in oil recovery. These undesired water production through the water channel between injection and the nearby off set production wells cause severe blow to oil recovery. This water channeling phenomena leads to high water cut in production wells，pressure drop and resist the injected fluid to penetrate into low permeable layers (oil rich region) thus ，bypassing the oil in the formation，hence the poor sweep efficiency and total oil recovery.
Here in this thesis we have studied the mechanism of excessive water production occuring through water channels，their diagnostic methods and further formulated the recipe，“Polymer Gel” to plug these water channels. Our approach used to diagnosis water channel is production data analysis from the field and further synthetic model to validate the approach. The gel plugging of these high conductive channels resist the water flow into high permeable layers (channels)，eventually leading to injection fluid diversion，thus allowing both the areal and vertical sweep improvement. A numerical simulation model for water channeling has been presented here to understand the dynamic behavior of the reservoir，which guide us to take timely measures to plug or shutoff these water channels.
Our numerical model is built using COMSOL Multiphysics where the flow is described by the Navier-Stokes equation in the channel region and a Forchheimer-corrected version of the Brinkman equations in the porous region to distinguish the impact of corrected physics. And further，design a numerical simulation model using CMG-STARS replicating the water channeling features for evaluation of conformance control. Our experimental work using sandpack model has also been meaningful in both designing the recipe for plugging the channels as well as understand the physics of gel propagation in porous media，eventually，measure the ultimate recovery . The plugging capacity of polymer gel was 96.6 % for our sand pack of permeability 180x10-3 2?m . The oil recovery during primary water flooding recorded as 49.2%along with 96%water cut，the polymer gel flooding at 0.5 PV resulted in an incremental of 3%of oil . The secondary water flooding resulted in equal fraction of oil and water cut while the tertiary water flooding was able to produce 1.1 %of oil recovery at the water cut of 98%. Thus，the water channeling issue has been studied numerically and then put forward the remedial measure to plug these channel was successfully studied in our lab.
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摘要 :
The tropical cyclone is a majestic, yet violent atmospheric weather system occurring over tropical waters.Their majesty produces the significant range of spatial scales: from the mesoscale to the larger synoptic-scale.Their asso...
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The tropical cyclone is a majestic, yet violent atmospheric weather system occurring over tropical waters.Their majesty produces the significant range of spatial scales: from the mesoscale to the larger synoptic-scale.Their associated violent winds, heavy rainfall and storm surges are often the cause of damage and destruction in their path.
In this study two tropical cyclones (TCs) KOMEN in 2015 during the peak-monsoon and ROANU in 2016 during the pre-monsoon seasons are analyzed by using the Advanced research of the Weather Research and Forecasting (WRF-ARW) Model to examine its ability to reproduce the heavy rainfall over western Myanmar due to the interaction between the tropical cyclone and topography.In addition, the Indian Institute of Technology-Delhi (IIT-D) based surge model is used to understand the phenomena of the storm surge and to investigate its ability to generate the surge over western Myanmar.
To understand the mechanism of heavy rainfall, an attempt has been made to simulate a heavy rainfall event on 25 July-1 August 2015 over western Myanmar using (WRF-ARW) model version (3.7) with Yonsei University scheme (YSU) for planetary boundary layer and WRF Single-Moment 3-class for microphysics scheme (WSM3) on a single domain at 3 km horizontal resolutions.The initial and boundary conditions to simulate the TC KOMEN are obtained from the National Center for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) global final (FNL) analysis dataset on resolution of 1° × 1° grids and six-hourly intervals has been used to frnd the link between rainfall and prevailing atmospheric dynamics on surface during the heavy rainfall event.
The model performance was assessed by examining the different predicted parameters like geopotential height, upper and lower level circulations, convergence, vorticity, temperature, heat flux, moisture, and rainfall.The strength of convective instability is also analyzed with the convective available potential energy (CAPE).The large-scale circulation features, moisture, and temperature are compared with those in the National Centers for Environmental Prediction analyses.The model derived rainfall was validated with Department of Meteorology and Hydrology (DMH) observed rainfall.The results indicate that the WRF model was able to simulate reasonably well the heavy rainfall event.The model suggested that the strong westerly wind flow transported high amount ofmoistnre from the Bay of Bengal towards the west coast of Myanmar and adjoining areas and this high rainfall events over western part of Myanmar might be characterized by the positive vorticity, strong convergence and low level jet which support the moisture flux and instability at low level.
To get the accurate forecast of heavy rainfall, TC track forecast is important.Thus, the impact of different microphysics and boundary schemes and terrain settings on the heavy rainfall over western Myanmar associated with TC ROANU (2016) are investigated using the WRF model.The impact of MP and PBL schemes are investigated by using the initial and boundary conditions to simulate the TC ROANU are obtained from the NOAA National Operational Model Archive and Distribution System (NOMADS) global forecast system (GFS) dataset on resolution of 0.5° × 0.5° grids and every six-hourly intervals has been used for the diagnostic analysis.
The results show that the mierophysics scheme of Purdue Lin scheme (LIN) produces the strongest cyclone.Six experiments with various combinations of microphysics and boundary schemes indicated that a combination of WRF Single-Moment 6-class (WSM6) scheme and Mellor-Yamada-Janjic (MYJ) best fits to the Joint Typhoon Warning Center (JTWC) data. WSM6-MYJ also performs the best for the track and intensity of rainfall and obtains the best statistics skill scores in the range of maximum rainfall intensity for 48-h.Sensitivity experiments on different terrain settings with normal Rakhine Mountain (NRM), with half of Rakhine Mountain (HRM), and without Rakhine Mountain (WoRM) are designed with the use of WSM6- MYJ scheme.The track of TC ROANU moved northwestward in WoRM and HRM.In these two experiments, the amount of rainfall was larger than NRM.Due to the presence of Rakhine Mountain, TC track moved into Myanmar and the peak rainfall occurred on the leeward side of the Mountain.In the absence of Rakhine Mountain, a shift in peak rainfall was observed in north side of the Mountain.A rich source of moisture most likely originates from divergence of TC wind and horizontal moisture flux (wind) are shown to be the key factor behind the heavy rainfall over western Myanmar.
In order to accurately and on time numerical prediction of a surge due to TC, it is a crucial task for disaster mitigation.This study used the (IIT-D)-based surge model to explore the various factors of a surge in Myanmar.Case studies were done wi
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