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Geotechnical aspects of groundwater recharge in arid regions
Published in H. Rahardjo, D.G. Toll, E.C. Leong, Unsaturated Soils for Asia, 2020
The small-scale field ponding studies consisted of two tests, one with a 100 cm diameter pond and the other with a 50 cm diameter pond. A pond depth of 20 cm was used in both small-scale field tests. Moisture contents were monitored using a capacitance probe at the centers and edges of the ponds, as well as 50 cm radically outward from the pond edges. These capacitance probe-determined moisture contents were supplemented and confirmed by several direct water content measurements. Inflow infiltration rates were obtained by measuring water depth inside the reservoir used to supply the ponds.
Electric and Dielectric Methods for Monitoring Soil-Water Content
Published in L.G. Wilson, Lorne G. Everett, Stephen J. Cullen, Handbook of Vadose Zone Characterization & Monitoring, 2018
The weaknesses of the capacitance technique include: the fact that a calibration curve must be constructed for each site; the large disparity between published calibration curves and expected behavior from Equation 30; the relatively small zone of influence of capacitance probes and their sensitivity to the region immediately adjacent to the probe; the effect of access tubes on its performance; the fact that the effect of electrical conduction on capacitance probe performance is not well documented; and its sensitivity to air gaps surrounding the probes.
Study on particle cluster behavior in the multistage circulating fluidized bed
Published in Particulate Science and Technology, 2022
Xiaolai Zhang, Gongpeng Wu, Yan He, Xuejun Yu
A number of studies on particle clusters have been conducted to characterize cluster properties over the last decades. Various experimental techniques including invasive and noninvasive methods are proposed. Invasive methods such as optical probe and capacitance probe are used to detect clusters and provide local cluster information. Cluster features can be extracted from solid concentration signals by mean of statistic and wavelet decomposition analyses (Chew et al. 2012). Obviously, this method unavoidably disturbs cluster flow and is limited to local measurements. Noninvasive methods mainly refer to visualization measurements such as high-speed video camera (Cocco et al. 2010) and laser sheet technique (Pandey et al. 2004). Instantaneous images of cluster distributions in the riser are collected with the high-frequency record. Coupled with digital image analysis (DIA), clusters are recognized and analyzed in the overall flow regions rather than the local positions. It is more suitable for dilute flow than dense flow due to the limitation of light penetration. Meanwhile, a pseudo two-dimensional (2D) bed is required to acquire clear flow images. Various cluster characteristics (e.g., size, shape, duration, voidage, and frequency) are obtained based on the methods mentioned above.
Study of cluster characteristics in a circulating fluidized bed riser
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Shangyi Yin, Tao Song, Tong Chen, Yuhang Chen, Ping Lu, Qingjie Guo
Summarized from the reported studies so far, the measurement techniques for clusters could be mainly divided into intrusive methods (e.g., optical fiber, capacitance probe)(Cahyadi et al. 2017; Cheng, Dai, and Qi 2016; Dai, Cheng, and Qi 2016) and non-intrusive methods (high-speed video, PIV, electrostatic and vibration sensing, etc.)(Chen et al. 2017; Mondal 2015; Mondal et al. 2016; Sun and Yan 2017; Wu et al. 2018; Yang and Zhu 2015). The former is advantageous for acquiring the instantaneous solids holdup and particle velocity. However, it performs better for describing local flow than mapping the overall gas-solid flow structure, let along its undesirable physical flow disturbances. By contrast, the non-intrusive visualization technique is applicable for obtaining the whole image of flow. Consequently, more attention has been attracted to visualization techniques in recent years. Mondal (2015) proposed the gray value as a threshold to identify clusters from the greyscale images over time and concluded that the properties of clusters are dependent on particle size, bed material mass, superficial gas velocity, and other factors. Besides, Yang and Zhu (2015) introduced a threshold selection method maximizing the inter-class gray values to image processing and demonstrated that a cluster is the combination of a relatively stable cluster core and constantly changing cluster cloud. Furthermore, Wu et al. (2018) proposed a new algorithm to optimize cluster identification and studied the distribution of the flexible filamentous particle clusters.
Agro-hydrologic modelling for simulating soil moisture dynamics in the root zone of Potato based on crop coefficient approach under limited climatic data
Published in ISH Journal of Hydraulic Engineering, 2022
Navsal Kumar, Vijay Shankar, Arunava Poddar
Precise measurement of the water balance components from lysimetric experiments was obtained to estimate the field ETc. The soil moisture change at different depths in the Lysimeter was measured using the capacitance probe. The percolation to the groundwater was represented by drainage from the Lysimeter. ETc was computed using the following water balance equation (Bandyopadhyay and Mallick 2003),