Browsing by Author "Tsai, Jui-Pin"

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Characterizing subsurface hydraulic heterogeneity of alluvial fan using riverstage fluctuations
(2017-04-01)
Wang, Yu-Li
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Yeh, Tian-Chyi Jim
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Wen, Jet-Chau
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Huang, Shao-Yang
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Zha, Yuanyuan
The objective of this study is to demonstrate the ability of riverstage tomography to estimate 2-D spatial distribution of hydraulic diffusivity (D) of Zhuoshui River alluvial fan, Taiwan, using groundwater level data from 65 wells and stream stage data from 5 gauging stations. In order to accomplish this objective, wavelet analysis is first conducted to investigate the temporal characteristics of groundwater level, precipitation, and stream stage. The results of the analysis show that variations of groundwater level and stream stage are highly correlated over seasonal and annual periods while that between precipitation is less significant. Subsequently, spatial cross-correlation between seasonal variations of groundwater level and riverstage data is analyzed. It is found that the correlation contour map reflects the pattern of sediment distribution of the fan. This finding is further substantiated by the cross-correlation analysis using both noisy and noise-free groundwater and riverstage data of a synthetic aquifer, where aquifer heterogeneity is known exactly. The ability of riverstage tomography is then tested with these synthetic data sets to estimate D distribution. Finally, the riverstage tomography is applied to the alluvial fan. The results of the application reveal that the apex and southeast of the alluvial fan are regions with relatively high D and the D values gradually decrease toward the shoreline of the fan. In addition, D at northern alluvial fan is slightly larger than that at southern. These findings are consistent with the geologic evolution of this alluvial fan. (C) 2017 Elsevier B.V. All rights reserved.
Collaborative Production Machine Choice System Based on Hierarchical Case Based Reasoning
(2009)
Tseng, Shian-Shyong
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Chang, Fengming M.
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Lin, Huan-Yu
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Hsu, Chi-Chun
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Ku, Chung-Chao
New cell phone styles and technologies developments are changing quickly. To improve the ability of competition for a company, a new designed cell phone has to be available in the market in the short time. Therefore, production processes including manufacturing machine choice for a new cell phone product have to be determined quickly. Facing the lack of information, it is difficult to choose manufacturing machines for a production process for a new product. Thus, this study proposed a Collaborative Production Machine Choice System (CPMCS) based on a hierarchical case based reasoning approach to solve the problem of machine choice for new cell phone production. A real interaction system is built up also to help users for machine choice in this study. Using non-fixed number of new product features, this system can advise suitable machines for users by case based reasoning approach and help users to find out the right machines for production in the short time.
Constructing the Apparent Geological Model by Fusing Surface Resistivity Survey and Borehole Records
(2019-07-01)
Tsai, Jui-Pin
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Chang, Ping-Yu
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Yeh, Tian-Chyi J.
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Chang, Liang-Cheng
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Hsiao, Chin-Tsai
We constructed an apparent geological model with resistivity data from surface resistivity surveys. We developed a data fusion approach by integrating dense electrical resistivity measurements collected with Schlumberger arrays and wellbore logs. This approach includes an optimization algorithm and a geostatistic interpolation method. We first generated an apparent formation factor model from the surface resistivity measurements and groundwater resistivity records with an inverse distance method. We then converted the model into a geology model with the optimized judgment criteria from the algorithms relating the apparent formation factors to the borehole geology. We also employed a non-parametric bootstrap method to analyze the uncertainty of the predicted sediment types, and the predictive uncertainties of clay, gravel, and sand were less than 5%. Overall, our model is capable of capturing the spatial features of the sediment types. More importantly, this approach can be arranged in a self-updated sequence to enable adjustments to the model to accommodate newly collected core records or geophysical data. This approach yields a more detailed apparent geological model for use in future groundwater simulations, which is of benefit to multi-discipline studies.
Effect of connectivity and wettability on the relative permeability of NAPLs
(2009-02-01)
Chang, Liang-Cheng
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Chen, Hung-Hui
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Shan, Hsin-Yu
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Tsai, Jui-Pin
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土木工程學系
The characteristic relationships among relative permeability (K(r)), saturation (S) and capillary pressure (P) of NAPLs are the important constitutive laws to simulate the NAPLs flow in the subsurface. In this study, a micro model was used to obtain the values of permeability, saturation for the multi-phase flow of five fluid-pairs. The perspective micro model allows one to clearly observe the multiphase flow and allow this study to precisely measure the fluid saturation by digital image analysis. The experimental results showed hysteresis phenomenon of relative permeability versus saturation and that was not interpreted by previous studies. By carefully examining the recorded images, this study found that the degree of the connectivity for the micro channel occupied by wetting phase fluid could influence the relative permeability. Therefore, for the same saturation, the relative permeability in the imbibition is higher than that in the drainage. The results of the K(r)-S experiments for five fluid-pairs also showed that the residual saturation of wetting phase fluid decreased with the wettability increasing but increased with the interfacial tension increasing. Those interpretations and experimental results are valuable references for groundwater remediation and oil reservoir development.
Effects of liquid layers and distribution patterns on three-phase saturation and relative permeability relationships: a micromodel study
(2017-12-01)
Tsai, Jui-Pin
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Chang, Liang-Cheng
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Hsu, Shao-Yiu
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Shan, Hsin-Yu
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土木工程學系
In the current study, we used micromodel experiments to study three-phase fluid flow in porous media. In contrast to previous studies, we simultaneously observed and measured pore-scale fluid behavior and three-phase constitutive relationships with digital image acquisition/analysis, fluid pressure control, and permeability assays. Our results showed that the fluid layers significantly influenced pore-scale, three-phase fluid displacement as well as water relative permeability. At low water saturation, water relative permeability not only depended on water saturation but also on the distributions of air and diesel. The results also indicate that the relative permeability-saturation model proposed by Parker et al. (1987) could not completely describe the experimental data from our three-phase flow experiments because these models ignore the effects of phase distribution. A simple bundle-of-tubes model shows that the water relative permeability was proportional to the number of apparently continuous water paths before the critical stage in which no apparently continuous water flow path could be found. Our findings constitute additional information about the essential constitutive relationships involved in both the understanding and the modeling of three-phase flows in porous media.
Estimating Hydraulic Conductivity Fields in Composite Fan Delta Using Vertical Electrical Sounding
(2018-11-01)
Chen, You-Cheng
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Tsai, Jui-Pin
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Chang, Liang-Cheng
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Chang, Ping-Yu
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Lin, Helen
Hydraulic conductivity (K) is crucial for groundwater studies and is conventionally obtained through pumping tests, which are costly due to well installation, resulting in a limited amount of data. Recent studies have addressed this limitation by estimating K through the integration of a pumping-test K and electrical resistivity measurements. While this approach is suitable for local areas, it cannot readily be applied to determine K fields for the composite fan delta. This study proposes and demonstrates an advanced method to estimate the K's spatial distribution of a composite fan delta. The proposed method included data classification, linear regression, and kriging interpolation. Data classification was conducted using a physical-based zonation method. The K and formation factor (F) data pairs were classified into several groups. Linear regression was used to develop K-F mapping for each group. The regression results showed a good correlation between K and F in each group. These K-F mappings were verified by additional pumping tests. These results indicate that estimation errors were between 7 m/day and 58 m/day, and the correlation coefficient of each data group was greater than 0.8. Based on these regression equations and ordinary kriging method, the detailed K spatial distribution of the study area was derived. According to these results, the proposed method is efficient and economical to delineate K's spatial features for regional groundwater systems and can benefit groundwater-related studies.
Experimental study on imbibition displacement mechanisms of two-phase fluid using micro model
(2009-12-01)
Chang, Liang-Cheng
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Tsai, Jui-Pin
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Shan, Hsin-Yu
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Chen, Hung-Hui
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土木工程學系
This study applies a transparent micro model and digital image analysis to the experimental study of the displacement mechanisms for water and air in porous media during imbibition process, and examines the displacement formulas. This study conducts experiments following Lenormand's assumptions as closely as possible. Various displacement mechanisms were observed, and their images were recorded. The displacement mechanisms in imbibition are mainly snap-off, In type imbibition and piston-type motion. The experimental fluid displacement images and associated capillary pressure were then used to verify the displacement formulas. This experimental study shows that, when snap-off occurred, the experimental capillary pressures were close to the Lenormand's estimation of critical capillary pressures where enough surrounding area of the throat was saturated. When I1 and I2 type imbibitions occurred, the experimental capillary pressures were also close to the Lenormand's estimation of critical capillary pressures where enough connecting throats were saturated. The In type imbibition and its associated piston-type motions are the main processes to increase the wetting phase fluid saturation. For the pore-throat distribution applied in this study, snap-off can facilitate the occurrence of In type imbibition and its associated piston-type motion; therefore, snap-off is an important displacement mechanism in facilitating the increase of the wetting phase fluid saturation in the imbibition process. To summarize, this study provides valuable experimental support and suggestions for Lenormand's displacement formulas, which are the basis for many related experimental and numerical studies.
Features of spatiotemporal groundwater head variation using independent component analysis
(2017-04-01)
Hsiao, Chin-Tsai
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Chang, Liang-Cheng
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Tsai, Jui-Pin
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Chen, You-Cheng
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土木工程學系
The effect of external stimuli on a groundwater system can be understood by examining the features of spatiotemporal head variations. However, the head variations caused by various external stimuli are mixed signals. To identify the stimuli features of head variations, we propose a systematic approach based on independent component analysis (ICA), frequency analysis, cross-correlation analysis, well selection strategy, and hourly average head analysis. We also removed the head variations caused by regional stimuli (e.g., rainfall and river stage) from the original head variations of all the wells to better characterize the local stimuli features (e.g., pumping and tide). In the synthetic case study, the derived independent component (IC) features are more consistent with the features of the given recharge and pumping than the features derived from principle component analysis. In a real case study, the ICs associated with regional stimuli highly correlated with field observations, and the effect of regional stimuli on the head variation of all the wells was quantified. In addition, the tide, agricultural, industrial, and spring pumping features were characterized. Therefore, the developed method can facilitate understanding of the features of the spatiotemporal head variation and quantification of the effects of external stimuli on a groundwater system. (C) 2017 Elsevier B.V. All rights reserved.
Fusion of Time-Lapse Gravity Survey and Hydraulic Tomography for Estimating Spatially Varying Hydraulic Conductivity and Specific Yield Fields
(2017-10-01)
Tsai, Jui-Pin
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Yeh, Tian-Chyi Jim
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Cheng, Ching-Chung
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Zha, Yuanyuan
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Chang, Liang-Cheng
Hydraulic conductivity (K) and specific yield (S-y) are important aquifer parameters, pertinent to groundwater resources management and protection. These parameters are commonly estimated through a traditional cross-well pumping test. Employing the traditional approach to obtain detailed spatial distributions of the parameters over a large area is generally formidable. For this reason, this study proposes a stochastic method that integrates hydraulic head and time-lapse gravity based on hydraulic tomography (HT) to efficiently derive the spatial distribution of K and Sy over a large area. This method is demonstrated using several synthetic experiments. Results of these experiments show that the K and Sy fields estimated by joint inversion of the gravity and head data set from sequential injection tests in unconfined aquifers are superior to those from the HT based on head data alone. We attribute this advantage to the mass constraint imposed on HT by gravity measurements. Besides, we find that gravity measurement can detect the change of aquifer's groundwater storage at kilometer scale, as such they can extend HT's effectiveness over greater volumes of the aquifer. Furthermore, we find that the accuracy of the estimated fields is improved as the number of the gravity stations is increased. The gravity station's location, however, has minor effects on the estimates if its effective gravity integration radius covers the well field.
High Recharge Areas in the Choushui River Alluvial Fan (Taiwan) Assessed from Recharge Potential Analysis and Average Storage Variation Indexes
(2015-04-01)
Tsai, Jui-Pin
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Chen, Yu-Wen
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Chang, Liang-Cheng
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Kuo, Yi-Ming
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Tu, Yu-Hsuan
High recharge areas significantly influence the groundwater quality and quantity in regional groundwater systems. Many studies have applied recharge potential analysis (RPA) to estimate groundwater recharge potential (GRP) and have delineated high recharge areas based on the estimated GRP. However, most of these studies define the RPA parameters with supposition, and this represents a major source of uncertainty for applying RPA. To objectively define the RPA parameter values without supposition, this study proposes a systematic method based on the theory of parameter identification. A surrogate variable, namely the average storage variation (ASV) index, is developed to calibrate the RPA parameters, because of the lack of direct GRP observations. The study results show that the correlations between the ASV indexes and computed GRP values improved from 0.67 before calibration to 0.85 after calibration, thus indicating that the calibrated RPA parameters represent the recharge characteristics of the study area well; these data also highlight how defining the RPA parameters with ASV indexes can help to improve the accuracy. The calibrated RPA parameters were used to estimate the GRP distribution of the study area, and the GRP values were graded into five levels. High and excellent level areas are defined as high recharge areas, which composed 7.92% of the study area. Overall, this study demonstrates that the developed approach can objectively define the RPA parameters and high recharge areas of the Choushui River alluvial fan, and the results should serve as valuable references for the Taiwanese government in their efforts to conserve the groundwater quality and quantity of the study area.
Joint Impact of Scaling and Hysteresis on NAPL Flow Simulation
(2009-12-01)
Chen, Hung-Hui
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Chang, Liang-Cheng
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Shan, Hsin-Yu
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Tsai, Jui-Pin
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土木工程學系
The hysteresis of capillary pressure versus saturation (P-S) relation is an important constitutive relation in multiphase flow, since the P-S relation is widely used to predict P-S relations in the simulation of the non-aqueous phase liquids (NAPLs). This work examined the performance of the scaling rule on predicting the P-S relationship and then studied the joint impact of the scaling and hysteresis on the multiphase NAPL flow simulation. Various experimental P-S values of distinct fluid pairs were compared with the scaled P-S curves using the scaling rule. The comparison indicated that the prediction of P-S is more accurate when the water-air P-S curve is used to scale other P-S curves. The joint impact of the scaling and hysteresis on the NAPLs flow simulation was then investigated by numerical simulation studies. The NAPL simulator was used to simulate the outcome of several scenarios based on a system with water-NAPL-air in a hypothetical sand tank. For both gasoline and trichloroethylene, the difference of the injected NAPL volume between no hysteretic and hysteretic simulations over a given time period was the smallest when the water-air P-S curve was used to scale other P-S curves. Simulation results of this study are valuable references for predicting the distribution of NAPLs.
Spatial-temporal pattern recognition of groundwater head variations for recharge zone identification
(2017-06-01)
Tsai, Jui-Pin
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Chang, Liang-Cheng
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Chang, Ping-Yu
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Lin, Yuan-Chien
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Chen, You-Cheng
The delineation of groundwater recharge zones is crucial for the conservation of groundwater quality and quantity. To objectively estimate groundwater recharge zones, many field surveys are required that are costly in both time and money. To facilitate the assessment of recharge zones with high efficiency and low expense, this study proposes a 'fast-filter' approach based on empirical orthogonal function analysis and applies it in a synthetic case study and to Taiwan's Yilan Plain. In the synthetic case study, we demonstrate that the proposed method can effectively identify the recharge area by considering the head variations driven by rainfall recharge. For the case of Yilan Plain application, the field investigations (i.e., collected wellbore logs and electrical resistivity tomography [ERT] surveys) and a groundwater simulation model support the recharge zones estimated by the proposed method. The study results show that within the estimated recharge zone, all of the collected wellbore logs consist of coarse grains, and thick and continuous high resistivity zones were shown in the ERT profile images. Moreover, the groundwater model indicates that the recharge within the estimated recharge zone is 57.6% of the total recharge despite that the area of the estimated zone is only 26.8% of the study area. Therefore, the proposed method is shown to delineate recharge zones at low cost. (C) 2017 Elsevier B.V. All rights reserved.
The assessment of high recharge areas using DO indicators and recharge potential analysis: a case study of Taiwan\'s Pingtung plain
(2015-03-01)
Tsai, Jui-Pin
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Chen, Yu-Wen
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Chang, Liang-Cheng
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Chen, Wen-Fu
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Chiang, Chung-Jung
Identifying high groundwater recharge areas is important for the conservation of groundwater quality and quantity. A common practice used by previous studies is to estimate groundwater recharge potential (GRP) using recharge potential analysis (RPA) under different environments. These studies use the estimated GRP to identify the high potential groundwater recharge sites. However, the RPA parameters are subjectively defined for these previous studies. To remove the supposition, this study proposes a systematic approach that defines the RPA parameter values based on the theory of parameter identification. This study uses dissolved oxygen (DO) indicators to calibrate the RPA parameters. This calibration improves the correlation coefficient between the DO indicators and computed GRP values from 0.63 to 0.87. By comparing the initial values, these results indicate that the estimated RPA parameters better represent the field infiltration characteristic. This result also indicates that defining the RPA parameter values based on DO indicators is necessary and important for accuracy. These calibrated parameters are used to estimate the GRP distribution of Taiwan\'s Pingtung Plain. The GRP values are delineated into five levels. High and excellent GRP areas are defined as high recharge areas, which compose about 26.74 % of the study area. Based on the proposed method, the estimated GRP distribution can accurately represent the study area\'s field recharge characteristics. These study results can be a good reference for groundwater recharge analyses, specifically if well data is limited or difficult to obtain.