Simulation of subsurface flow through fractured media is significantly influenced by uncertainty in matrix block size, fracture aperture and fracture distribution due to inherent heterogeneity. In recent years, probab...
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Simulation of subsurface flow through fractured media is significantly influenced by uncertainty in matrix block size, fracture aperture and fracture distribution due to inherent heterogeneity. In recent years, probabilistic collocation method (PCM) has emerged as a precise approach for quantifying uncertainty. However, computing uncertainty propagation during simulation of unsteady multiphase transport in porous media could not be performed through previous PCM-based studies or even Monte Carlo simulation. Therefore, this study introduces an innovative numerical modeling framework that improves PCM on sparse grids and integrates it with Smolyak procedure to generate collocation points sets, Karhunen-Loeve and polynomial chaos expansions to assess the uncertainty associated with oil-water flow through fractured media with consideration of gravity imbibition force. By coupling developed numerical framework and solving deterministic equations, uncertainty propagation from initial time-step to final time-step of simulation is computed and the effect of uncertainty in vertical dimension of matrix blocks, a parameter with significant role in gravity imbibition and commonly subject to uncertainty and history matching, on simulation outputs of randomly synthesized 3D porous media is quantified. The confidence interval and aggregated uncertainty in ultimate production are computed, and at each time-step, statistical moments of simulation outputs are obtained. The findings demonstrate that proposed model effectively quantifies uncertainty while significantly reducing CPU time compared to Monte Carlo simulation.
The increasing integration of renewable energy resources (RERs) such as wind and solar onto the electric power grid through power electronic interface is challenging safe and reliable grid operation. Particularly, the...
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ISBN:
(纸本)9781665412117
The increasing integration of renewable energy resources (RERs) such as wind and solar onto the electric power grid through power electronic interface is challenging safe and reliable grid operation. Particularly, the high penetration of the inverter-based RERs (IB-RERs) may drive the grid towards weak grid conditions, which may cause grid stability issues. Grid strength assessment is helpful to identify these weak grid issues. However, it is challenging to assess grid strength while considering the impact of uncertain renewable generation. This paper presents an approach for quantifying the probabilistic characteristics of grid strength under uncertain renewable generation based on the probabilistic collocation method, which is a computationally efficient technique to reduce the computational burden without compromising the result accuracy compared with traditional Monte Carlo simulation. The efficacy of the proposed approach is demonstrated on the modified IEEE 9-bus system.
Increased penetration of distributed generation (DG) driven by Variable Renewable Energy (VRE) sources and integration of modern loads constituted by Electric Vehicles (EV) and behind-the-meter smart appliances pose o...
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ISBN:
(纸本)9781728181929
Increased penetration of distributed generation (DG) driven by Variable Renewable Energy (VRE) sources and integration of modern loads constituted by Electric Vehicles (EV) and behind-the-meter smart appliances pose operational challenges for traditional distribution systems. This paper introduces a framework based on probabilistic collocation method (PCM) to model and analyzes the effects of inherent uncertainties, both in generation, and load, on distribution systems. First, the uncertainties are modeled by statistical distributions that closely mimic their physical behavior and studied through Monte-Carlo (MC) simulations. Later, an analytical PCM based approach is formulated and designed on the modified IEEE 13-node test feeder including VRE. A comparative study demonstrates the effectiveness of the proposed PCM based uncertainty modeling in distribution feeders with lesser computational burden and improved accuracy.
The permeability of natural porous media, such as soils and rocks, usually possesses uncertainties due to the randomness and spatial variation of microscopic pore structures. It is of great importance to develop an ef...
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The permeability of natural porous media, such as soils and rocks, usually possesses uncertainties due to the randomness and spatial variation of microscopic pore structures. It is of great importance to develop an effective methodology to obtain statistical properties of permeability for porous media. In this work, an efficient approach is developed by combining the sphere packing algorithm, lattice Boltzmann method (LBM), and probabilistic collocation method (PCM). The porous media are generated by sphere packings of a specified size distribution, and the isotropy and representative elementary volume are verified by statistical analyses. Fluid flow in the complex pore structures is numerically resolved by LBM, with the permeability calculated by Darcy's law. The uncertainty of permeability can be quantified by PCM with only several porosity samplings required at predetermined collocation points. In addition, the porosity-permeability relationships can be acquired efficiently. Numerical results indicate that, with the proposed approach, the computational efforts are reduced by more than two orders of magnitude compared to the Monte Carlo simulations.
作者:
Xue, LiangDai, ChengWu, YujuanWang, LeiChina Univ Petr
State Key Lab Petr Resources & Prospecting Beijing 102249 Peoples R China China Univ Petr
Coll Petr Engn Dept Oil Gas Field Dev Engn Beijing 102249 Peoples R China SINOPEC Grp
State Key Lab Shale Oil & Gas Enrichment Mech & E Beijing 050021 Peoples R China Peking Univ
Coll Engn BIC ESAT Beijing 100083 Peoples R China
The characterization of flow in subsurface porous media is associated with high uncertainty. To better quantify the uncertainty of groundwater systems, it is necessary to consider the model uncertainty. Multi-model un...
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The characterization of flow in subsurface porous media is associated with high uncertainty. To better quantify the uncertainty of groundwater systems, it is necessary to consider the model uncertainty. Multi-model uncertainty analysis can be performed in the Bayesian model averaging (BMA) framework. However, the BMA analysis via Monte Carlo method is time consuming because it requires many forward model evaluations. A computationally efficient BMA analysis framework is proposed by using the probabilistic collocation method to construct a response surface model, where the log hydraulic conductivity field and hydraulic head are expanded into polynomials through Karhunen-Loeve and polynomial chaos methods. A synthetic test is designed to validate the proposed response surface analysis method. The results show that the posterior model weight and the key statistics in BMA framework can be accurately estimated. The relative errors of mean and total variance in the BMA analysis results are just approximately 0.013% and 1.18%, but the proposed method can be 16 times more computationally efficient than the traditional BMA method.
In this study, the probabilistic collocation method (PCM) is proposed to construct a stochastic correlation model of wind speeds at neighbouring wind farms and solve probabilistic power flow (PPF) of South Australia (...
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In this study, the probabilistic collocation method (PCM) is proposed to construct a stochastic correlation model of wind speeds at neighbouring wind farms and solve probabilistic power flow (PPF) of South Australia (SA) grid. Based on the historical sampled wind source data, the model is developed to reduce the number of uncertain parameters of the power system model by considering the spatial correlation of wind speeds between neighbouring wind farms. Furthermore, this model aims to increase the computational efficiency of PCM when dealing with PPF simulation. Finally, the computation efficiency and accuracy of the PCM, compared with traditional Monte Carlo simulation method, are validated by the simulation results of aggregated power flow model of SA case studies.
The probabilistic collocation method (PCM) has drawn wide attention for stochastic analysis recently. Its results may become inaccurate in case of a strongly nonlinear relation between random parameters and model resp...
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The probabilistic collocation method (PCM) has drawn wide attention for stochastic analysis recently. Its results may become inaccurate in case of a strongly nonlinear relation between random parameters and model responses. To tackle this problem, we proposed a location-based transformed PCM (xTPCM) and a displacement-based transformed PCM (dTPCM) in previous parts of this series. Making use of the transform between response and space, the above two methods, however, have certain limitations. In this study, we introduce a time-based transformed PCM (tTPCM) employing the transform between response and time. We conduct numerical experiments to investigate its performance in uncertainty quantification. The results show that the tTPCM greatly improves the accuracy of the traditional PCM in a cost-effective manner and is more general and convenient than the xTPCM/dTPCM.
In this study, a hybrid sequential data assimilation and probabilisticcollocation (HSDAPC) approach is proposed for analyzing uncertainty propagation and parameter sensitivity of hydrologic models. In HSDAPC, the pos...
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In this study, a hybrid sequential data assimilation and probabilisticcollocation (HSDAPC) approach is proposed for analyzing uncertainty propagation and parameter sensitivity of hydrologic models. In HSDAPC, the posterior probability distributions of model parameters are first estimated through a particle filter method based on streamflow discharge data. A probabilistic collocation method (PCM) is further employed to show uncertainty propagation from model parameters to model outputs. The temporal dynamics of parameter sensitivities are then generated based on the polynomial chaos expansion (PCE) generated by PCM, which can reveal the dominant model components for different catchment conditions. The maximal information coefficient (MIC) is finally employed to characterize the correlation/association between model parameter sensitivity and catchment precipitation, potential evapotranspiration and observed discharge. The proposed method is applied to the Xiangxi River located in the Three Gorges Reservoir area. The results show that: (i) the proposed HSDAPC approach can generate effective 2nd and 3rd PCE models which provide accuracy predictions;(ii) 2nd-order PCE, which can run nearly ten time faster than the hydrologic model, can capably represent the original hydrological model to show the uncertainty propagation in a hydrologic simulation;(iii) the slow (R-s) and quick flows (R-q) in Hymod show significant sensitivities during the simulation periods but the distribution factor (alpha) shows a least sensitivity to model performance;(iv) the model parameter sensitivities show significant correlation with the catchment hydro-meteorological conditions, especially during the rainy period with MIC values larger than 0.5. Overall, the results in this paper indicate that uncertainty propagation and temporal sensitivities of parameters can be effectively characterized through the proposed HSDAPC approach. (C) 2016 Elsevier Ltd. All rights reserved.
In this paper probabilistic collocation method (PCM) is introduced to solve a stochastic model representing wind farms in South Australia (SA). The model is based upon historical acquisition of wind source data, and c...
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ISBN:
(纸本)9781509043033
In this paper probabilistic collocation method (PCM) is introduced to solve a stochastic model representing wind farms in South Australia (SA). The model is based upon historical acquisition of wind source data, and considering the spatial correlation of wind speeds at neighboring wind farms. This correlation is used to reduce the number of uncertain parameters of the model, and then reducing the cost of PCM computation. In addition, fuzzy logic optimization is applied to PCM to improve the accuracy of the model output. The paper concludes with presentation of an aggregated DC load flow model of SA that is used as an example to compare the computation efficiency of the PCM and traditional Monte Carlo (MC) simulation method.
The Karhunen-Loeve (KL) expansion and probabilistic collocation method (PCM) are combined and applied to an uncertainty analysis of rock failure behavior by integrating a self- developed numerical method (i.e., t...
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The Karhunen-Loeve (KL) expansion and probabilistic collocation method (PCM) are combined and applied to an uncertainty analysis of rock failure behavior by integrating a self- developed numerical method (i.e., the elastic-plastic cellular automaton (EPCA)). The results from the method developed are compared using the Monte Carlo Simulation (MCS) method. It is concluded that the method developed requires fewer collocations than MCS method to obtain very high accuracy and greatly reduces the computational cost. Based on the method, the elasto- plastic and elasto-brittle-plastic analyses of rocks under mechanical loadings are conducted to study the uncertainty in heterogeneous rock failure behaviour.
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