Novapoint Online Documentation

Squat Calculation

Here is presented the calculation formulas and principles of Squat methods used at Novapoint Waterway.

Common values for all calculation formulas include Ship Speed and Ship dimensions.

Ship Speed

Ship speed is general input for all calculation methods. User inputs ship speed in knots. Knots are converted to m/s by formula (1): V (m/s) = knots*[ 1852 ] 3600 ——————- (1)

Ship dimensions

Dimensions include:

  • Ship width, B
  • Ship length between perpendiculars, L (also expressed Lpp)
  • Ship draft, T
  • Ship bulkiness, CB

Formulae

Guliev A calculation formula

Formula for Guliev A cross-section (Canal): Input limitations in Guliev A method are following:

  • 0.6 < CB < 0.8
  • 2.19 < B/T < 3.5
  • 5.5 < L/B < 8.5

Squat is calculated by formula (4): Squat = [GulievB(n; Fh)] B ———————–(4)

  • n= Channel Blockage ratio =

Ak*/Aa

  • Ak*= Channel cross-section area =

(Wh + 2(h2/slope/2))

  • Slope ;= slope 1:n
  • Aa= Ship submerged (water) cross-section area =

0.98(B*T)

  • Fh = Channel Froude's number from formula (3)

“GulievB” in formula (4) is a subroutine to iterate correct parameter for calculation based on channel blockage ratio and Froude's number.

Guliev B Calculation formula

Formula for Guliev Type B cross-section (Trench): Input limitations in Guliev B method are following:

  • 0.6 < CB < 0.8
  • 2.19 < B/T < 3.5
  • 5.5 < L/B < 8.5
  • 1.23 < L/B < 4.55

Squat is calculated by formula (5): Squat = [GulievB(n; Fh)] B ————————–(5)

  • n = n* x K (K points to subroutine)
  • n* = Ak*/Aa
  • Ak*= Channel cross-section area =

(Wh + 2(h2/slope/2))

  • Slope = slope 1:n
  • Aa= Ship submerged (water) cross-section area =

0.98BT

  • Fh = Channel Froude's number from formula (3)
  • t = slope height

“K” and “GulievB” in formula (5) are subroutines to iterate correct parameter for calculation based on channel blockage ratio and Froude's number.

Guliev C calculation formula

Formula for Guliev C cross-section (Shallow open water): Input limitations in Guliev C method are following:

  • 0.6 < CB < 0.8
  • 2.19 < B/T < 3.5
  • 5.5 < L/B < 8.5

Squat is calculated by empirical formula (6): Squat = [0.386319 * Fnh3 - 0.15523 * Fnh2 + 0.37373 * Fnh - 0.00014] * B ———————(6) Fnh ;= Fh = Channel Froude's number from formula (3)

Huuska-Icorels calculation formula

Squat is calculated by formula (2): Squat = ———————–(2)

  • t = Ship draft
  • CO= Coefficient multiplier. Default values: CO1=1.7, CO2=2.0, CO3=

2.4

  • CB = Ship bulkiness
  • b = Ship width
  • lpp = Ship length between perpendiculars
  • Fnh= Fh =

Channel Froude's number, calculated by formula (3)

  • ————————-(3)
  • V = ship speed from formula (1)
  • g= acceleration due to gravity =

9.81m/sec2

  • h = water depth

General

Huuska-Icorels method has one main calculation formula for squat calculation. This method has three multiplier factors called CO that is used in calculation and will give three variation of the calculation. Input limitations in Huuska-Icorels method are following:

  • CB < 0.75
  • B/L < 0.16

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