well_response: Spectral response for a sealed well
In kitagawa: Spectral Response of Water Wells to Harmonic Strain and Pressure Signals

well_response

R Documentation

Spectral response for a sealed well

Description

This is the primary function to calculate the response for a sealed well.

Usage

well_response(omega, T., S., Vw., Rs., Ku., B., ...)

## Default S3 method:
well_response(
  omega,
  T.,
  S.,
  Vw.,
  Rs.,
  Ku.,
  B.,
  Avs,
  Aw,
  rho,
  Kf,
  grav,
  freq.units = c("rad_per_sec", "Hz"),
  as.pressure = TRUE,
  ...
)

Arguments

`omega`	frequency, (see `freq.units`)
`T.`	effective aquifer transmissivity `[m^2/s]`
`S.`	well storativity, `[unitless]`
`Vw.`	well volume, `[m^3]`
`Rs.`	radius of screened portion, `[m]`
`Ku.`	undrained bulk modulus, `[Pa]`
`B.`	Skempton's coefficient, `[unitless, bounded]`
`...`	additional arguments
`Avs`	amplification factor for volumetric strain `E_{kk,obs}/E_{kk}`, `[]`
`Aw`	amplification factor of well volume change for `E_{kk}`, `[]`
`rho`	fluid density `[kg/m^3]`
`Kf`	bulk modulus of fluid, `[Pa]`
`grav`	local gravitational acceleration `[m/s^2]`
`freq.units`	set the units of `omega`
`as.pressure`	logical; should the response for water pressure? (default is water height)

Details

The response depends strongly on the physical properties given. Default values are assumed where reasonable–for instance, the pore-fluid is assumed to be water–but considerable care should be invested in the choice of parameters, unless the function is used in an optimization scheme.

Assumed values are:

`Avs`	1	amplification factor for volumetric strain
`Aw`	1	amplification factor for water well

The responses returned here are, effectively, the amplification of water levels in a well, relative to the aquifer strain; or

Z = \frac{z}{\epsilon} \equiv \frac{p}{\rho g \epsilon}

If as.pressure=TRUE, then the responses are scaled by rho*grav so that they represent water pressure relative to aquifer strain:

Z = \frac{p}{\epsilon}

Not all parameters need to be given, but should be. For example, if either rho or grav are not specified, they are taken from constants. Parameters which do not end in . do not need to be specified (they may be excluded); if they are missing, warnings will be thrown.

Value

An object with class 'wrsp'

Author(s)

A. J. Barbour

References

See kitagawa-package for references and more background.

Examples

#### dummy example
well_response(1:10, T.=1, S.=1, Vw.=1, Rs.=1, Ku.=1, B.=1)

#### a more physically realistic calculation:
# Physical params applicable for B084 borehole
# (see: http://pbo.unavco.org/station/overview/B084/ for details)
#
Rc <- 0.0508   # m, radius of water-sensing (2in)
Lc <- 146.9    # m, length of grouted region (482ft)
Rs <- 3*Rc     # m, radius of screened region (6in)
Ls <- 9.14     # m, length of screened region (30ft)
#
# calculate the sensing volume for the given well parameters
Volw <- sensing_volume(Rc, Lc, Rs, Ls) # m**3, ~= 1.8
#
Frqs <- 10**seq.int(from=-4,to=0,by=0.1) # log10-space
head(Rsp <- well_response(omega=Frqs, T.=1e-6, S.=1e-5, 
Vw.=Volw, Rs.=Rs, Ku.=40e9, B.=0.2, freq.units="Hz"))

# Access plot.wrsp:
plot(Rsp)

kitagawa documentation built on May 29, 2024, 4:21 a.m.