## Resistance & Powering
The resistance estimation method that I am using in the spreadsheet I have developed is based on; - a residuary resistance estimation method developed by Sui Fung and Larry Leibman for transom hulled vessels that was presented at the FAST 1995 conference.
- a frictional resistance estimation based on the ITTC 1957 curve,
- an appendage
resistance estimation based on a method outlined in the US Navy's
Design Data Sheet 051-1 (
**DDS 051-1**) "Prediction of Smooth-Water Powering Performance for Surface-Displacement Ships", and - a wind resistance and still air drag estimation based on a method attributed to RADM David W. Taylor, as described in the book "Principles of Naval Architecture".
F-TSH method, the method presented in the 1993 SNAME
Chesapeake Section paper as the Fung & Leibamn or F&L
method, and the revised method presented in at the FAST 1995 conference
as the revised Fung & Leibman or F&L 2 method.I selected the In the In this method; Cr = exp{ S [ B Where; - X1 =
**Fn**^{d} - X2
= cos (l *
**Fn**^{e}) * exp (a/**Fn**^{2}) - X3
= {0.034977 * [
**D**/(**L**/100)^{3}]}^{0.5} - X4 =
**AT** - X5 =
**Cp**^{2} - X6 =
**BT** - X7 =
**B/T** - X8 = LN( 90 -
**ie**) - X9 =
**Cm** **D**= Displacement- l
= [ a
_{1}* Cp + a_{2}***D**/(**L**/100)^{3}] - a = - 0.2000
- a
_{1}= 0.7500 - a
_{2}= 0.0350 - d = - 0.7000
- e = - 1.9300
- n = 69 (eg. the number of terms in regression model excluding the constant)
- S = the summation operator from i = 0 to i = n (eg. it means sum all these terms together)
- P = the multiplication operator from j = 0 to 9 (eg. it means multiply all these terms together)
- B
_{i}= the regression coefficients (as summarized in the table below)
The range of applicability for this method is; **Fn**between 0.15 & 0.90**DLR**between 16.239 & 359.180**LCB**between 0.481 & 0.591**ie**between 2.600 & 31.730**L/B**between 2.520 & 17.935**B/T**between 1.696 & 10.204**Cp**between 0.526 & 0.774**Cm**between 0.556 & 0.994**Cwp**between 0.662 & 0.841**TA**between 0.00 & 0.740**TB**between 0.000 & 1.000**TT**between 0.000 & 0.770**Cws**(Wetted Surface Coefficient) between 14.324 & 23.673
page where;BackgroundCf =
0.075/(log10 (Rn) - 2)^{2}Where Rn = and is is defined as;Reynold's numberRn = v L / nWhere; v = the vessel's speedL = the vessels lengthn = the kinematic visosity of
water (all in consistant units)
DDS 051-1 as shown in
the two figures below.These figures show the
recommended Appendage Drag Coefficients from
- only the still air drag generated solely from the ship's forward motion (condition 1), or
- the still air drag generated from the ship's forward motion plus a certain amount of head wind acting on the front of the vessel (condition 2)
As noted on the
Where; **Raa**= The total added air resistance**B**= the Beam of the ship (in meters)**V**= the apparent relative wind velocity (for condition 1 this would be equal to the forward speed of the ship, but in condition 2 this would include both the speed of the ship and any additional head wind) (in meters per second)_{R}
I have selected this version of the equation for use as it doesn't require an estimate of frontal area, which may not be fully known in early stage design. In the future I may consider updating this section however, to ensure that the resistance of vessels with non-traditional deckhouse sizes are adequately addressed.
FFG 7, DD 963,
a DDG 51 class vessel, a CG 47 class vessel, and the
resistance for these vessels as estimated using the above
methods. For reference I have also included an estimate of the
resistance for these vessels based on the more complex Holtrop &
Mennen/NSMB method.As can be seen from these
figures both the |
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