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Calculate pressure and flow profile along a lateral line (Backstep procedure)

Source: R/calc_backstep.R
calc_backstep.Rd

calc_backstep calculates the pressure head and flow rate profile along an irrigation lateral line, starting from the distal end (last emitter) and stepping backwards to the inlet.

Usage

calc_backstep(
  end_pressure,
  diameter,
  spacing,
  n_emitters,
  slope = 0,
  emitter_coef,
  emitter_exp,
  flow_unit = c("m3/s", "l/h", "m3/h", "l/s"),
  ...
)

Arguments

end_pressure

Pressure head at the end of the lateral line (last emitter) in meters of water column (mca).

diameter

Diameter of the pipe in meters (m).

spacing

Emitter spacing in meters (m). Can be a single value or a vector of spacings.

n_emitters

Total number of emitters on the lateral line.

slope

Elevation change (slope) per meter of pipe (m/m). Positive values indicate uphill slope, negative for downhill.

emitter_coef

Emitter discharge coefficient.

emitter_exp

Emitter discharge exponent.

flow_unit

Flow measurement unit. Options are "m3/s", "l/h", "m3/h", or "l/s". Default is "m3/s".

...

Additional arguments passed to calc_head_loss (e.g., method, roughness, hazen_coef).

Value

A data frame containing the profile of the lateral line:

  • emitter: Emitter index (1 is the first emitter near the inlet, n is the last).

  • pressure_head: Pressure head at each emitter (mca).

  • emitter_flow: Flow rate discharged by each emitter.

  • section_flow: Flow rate in the pipe section just upstream of the emitter.

  • head_loss: Friction head loss in the pipe section upstream of the emitter (m).

Examples

# Simple lateral line with 5 emitters, 1m spacing (returns flow in m3/s)
calc_backstep(
  end_pressure = 10, diameter = 0.012, spacing = 1, n_emitters = 5, slope = 0,
  emitter_coef = 8.84e-7, emitter_exp = 0.50
)
#>   emitter pressure_head emitter_flow section_flow    head_loss
#> 1       1      10.00566 2.796244e-06 1.397885e-05 0.0022621971
#> 2       2      10.00339 2.795928e-06 1.118260e-05 0.0016965918
#> 3       3      10.00170 2.795691e-06 8.386677e-06 0.0011310346
#> 4       4      10.00057 2.795532e-06 5.590986e-06 0.0005655093
#> 5       5      10.00000 2.795453e-06 2.795453e-06 0.0000000000

# Using Flamant method and returning flow in l/h (common for drip irrigation)
calc_backstep(
  end_pressure = 10, diameter = 0.012, spacing = 0.3, n_emitters = 12, slope = 0,
  emitter_coef = 3.18, emitter_exp = 0.50, flow_unit = "l/h", method = "flamant"
)
#>    emitter pressure_head emitter_flow section_flow    head_loss
#> 1        1      10.01233     10.06224    120.69472 2.733187e-03
#> 2        2      10.00960     10.06087    110.63247 2.313165e-03
#> 3        3      10.00729     10.05971    100.57161 1.923577e-03
#> 4        4      10.00536     10.05874     90.51190 1.565219e-03
#> 5        5      10.00380     10.05795     80.45316 1.239011e-03
#> 6        6      10.00256     10.05733     70.39521 9.460351e-04
#> 7        7      10.00161     10.05685     60.33788 6.875937e-04
#> 8        8      10.00093     10.05651     50.28102 4.653006e-04
#> 9        9      10.00046     10.05627     40.22451 2.812465e-04
#> 10      10      10.00018     10.05613     30.16824 1.383329e-04
#> 11      11      10.00004     10.05606     20.11211 4.112654e-05
#> 12      12      10.00000     10.05604     10.05604 0.000000e+00