The effects of oscillation period on groundwater wave dispersion in a sandy unconfined aquifer: Sand flume experiments and modelling

Shoushtari, Seyed Mohammad Hossein Jazayeri, Cartwright, Nick, Nielsen, Peter and Perrochet, Pierre (2016) The effects of oscillation period on groundwater wave dispersion in a sandy unconfined aquifer: Sand flume experiments and modelling. Journal of Hydrology, 533 412-420. doi:10.1016/j.jhydrol.2015.12.032


Author Shoushtari, Seyed Mohammad Hossein Jazayeri
Cartwright, Nick
Nielsen, Peter
Perrochet, Pierre
Title The effects of oscillation period on groundwater wave dispersion in a sandy unconfined aquifer: Sand flume experiments and modelling
Journal name Journal of Hydrology   Check publisher's open access policy
ISSN 0022-1694
Publication date 2016-02-01
Year available 2015
Sub-type Article (original research)
DOI 10.1016/j.jhydrol.2015.12.032
Open Access Status Not yet assessed
Volume 533
Start page 412
End page 420
Total pages 9
Place of publication Amsterdam, Netherlands
Publisher Elsevier BV
Language eng
Subject 2312 Water Science and Technology
Abstract This paper presents a new laboratory sand flume dataset on the propagation of groundwater waves in an unconfined sandy aquifer with a vertical boundary subject to simple harmonic forcing with a wide range of oscillation period from 10.7. s to 909. s. The data is unique in that it covers a much wider range of non-dimensional aquifer depths, nωd/. K (where n is the porosity, ω is the angular frequency, d is the aquifer depth and K is the hydraulic conductivity) than has been previously investigated. Both the amplitude decay rate and rate of increase in phase lag of the water table waves are observed to monotonically increase with increasing oscillation frequency (increasing nωd/ K). This is in contrast to existing theoretical dispersion relations which predict: (1) zero phase lag or standing wave behaviour and (2) an asymptotic decay rate as the frequency increases. Possible influences on the experimental data including sand packing, measurement location, finite amplitude wave effects, unsaturated zone truncation and multiple wave mode effects are unable to explain the discrepancy. The data was also compared against numerical solutions of Richards' equation with and without hysteresis and in both cases, the same qualitative behaviour as the analytic solutions described above is found. The discrepancy between data and predictions remains unexplained and highlights a knowledge gap that requires further investigation. These findings relate directly to practical applications in the field of surface-groundwater interactions such as the influence of wave forcing of coastal aquifers on contaminant transport, sediment mobility and salt-water intrusion all of which are influenced by the dispersion of the groundwater wave.
Formatted abstract
This paper presents a new laboratory sand flume dataset on the propagation of groundwater waves in an unconfined sandy aquifer with a vertical boundary subject to simple harmonic forcing with a wide range of oscillation period from 10.7 s to 909 s. The data is unique in that it covers a much wider range of non-dimensional aquifer depths, nωd/K (where n is the porosity, ω is the angular frequency, d is the aquifer depth and K is the hydraulic conductivity) than has been previously investigated. Both the amplitude decay rate and rate of increase in phase lag of the water table waves are observed to monotonically increase with increasing oscillation frequency (increasing nωd/K). This is in contrast to existing theoretical dispersion relations which predict: (1) zero phase lag or standing wave behaviour and (2) an asymptotic decay rate as the frequency increases. Possible influences on the experimental data including sand packing, measurement location, finite amplitude wave effects, unsaturated zone truncation and multiple wave mode effects are unable to explain the discrepancy. The data was also compared against numerical solutions of Richards’ equation with and without hysteresis and in both cases, the same qualitative behaviour as the analytic solutions described above is found. The discrepancy between data and predictions remains unexplained and highlights a knowledge gap that requires further investigation. These findings relate directly to practical applications in the field of surface–groundwater interactions such as the influence of wave forcing of coastal aquifers on contaminant transport, sediment mobility and salt-water intrusion all of which are influenced by the dispersion of the groundwater wave.
Keyword Groundwater wave
Hysteresis
Richards' equation
Seepage face
Unsaturated flow
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Civil Engineering Publications
Official 2016 Collection
 
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