Low Flow Field Research Articles

Developing Groundwater Variability Probes and Wireless Sensor Networks for Characterizing the Subsurface Low Flow Field

Groundwater monitoring plays a key role in understanding solute transport processes, including pollutant fate and transport mechanisms, detection of leaks from groundwater storage containers, and development of early warning systems for flooding and bank stability. Furthermore, incorporating these monitoring fields into remote stations with wireless data transmittal has proven useful in real-time data analysis and field forecasting. A promising new technology called the groundwater variability probe (GVP) was developed, tested, and integrated into a wireless field station with inclusion of soil moisture probes and pressure transducers for monitoring hydraulic conditions within a pond bank. The GVP is capable of measuring real-time centimeter-scale velocity magnitude, flow direction, hydraulic conductivity, and dispersion coefficient measurements simultaneously. We found that the GVP can effectively measure seepage velocity in dispersion-dominated regimes from 26 to 460 cm ${\rm day}^{\mathrm {{-1}}}$ range and flow direction to within ±10°. The hydraulic conductivity was determined using Darcy's law. The GVP-derived velocity measurements were found to be within expected ranges of hydraulic conductivity. Dispersion coefficients of the plume were derived and found to be similar to values reported in the literature. A wireless sensor network was installed on a wet retention pond bank, allowing remote real-time access for monitoring changes in soil moisture, groundwater velocity, and stage fluctuations, providing insights into correlations with in-situ storm events.

Study on subway particle capture by ferromagnetic mesh filter in nonuniform magnetic field

Abstract A two-step method to understand the dust particle capture process in a magnetic field gradient was presented in this study. Dust capture depended strongly on the magnetic force exerting on the particles, which imply large particle size, slow flow velocity and large magnetic field gradients would increase the deposition. Aggregates of sub-micron particles observed in the captured dust sample were composed mainly of iron compounds. Low velocity was beneficial for capture of 1 μm particles, while high velocity facilitated the capture of larger particles (⩾2.5 μm). Complex weaving aided the particle collection in a relatively low flow field while simple weaving was more favorable at higher flows. Predictions of the magnetic capture efficiency of the entire filter were established qualitatively and quantitatively based on a subdomain simulation employing a cubic structure. Wire magnetization is useful for small particles with a fine filter, while relatively large particles such as 10 μm and 2.5 μm were good for medium and coarse mesh filters. Investigation of screen mesh weaving and the distance between magnets provided an optimum filter screen configuration and optimum operating parameters. The experimental results agreed quite well with the simulation work.