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AD-A139 089 UNCLASSIFIED ESTIMATING THE SEAKEEPING QUALITIES OF DESTROYER TYPE 1/1 HULLS(U) DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BET.. W R MCCREIGHT JAN 84 DTNSRDC/SPD-1074-01 F/G 20/4 NL "H END DATE riLNCD DTIC K

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AD-A139 089

UNCLASSIFIED

ESTIMATING THE SEAKEEPING QUALITIES OF DESTROYER TYPE 1/1 HULLS(U) DAVID W TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER BET.. W R MCCREIGHT JAN 84 DTNSRDC/SPD-1074-01 F/G 20/4 NL

"H

END DATE

riLNCD

DTIC

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MICROCOPY RESOLUTION TEST CHART

NATIONAL BUREAU 01 STANDARDS 1963-A

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DAVID W. TAYLOR NAVAL SHIP RESEARCH AND DEVELOPMENT CENTER

Bethasda. Maryland 20084 ^^^

CO i a

oo

CO ESTIMATING THE SEAKEEPING

QUALITIES OF DESTROYER TYPE HULLS

co

w 0-

BY

W.R. McCREIGHT

on w >< o as H CO w Q

d, O

CO w

=3

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a. w

CO

2 M

1 M H CO Ci)

APPROVED FOR PUBLIC RELEASE: DISTRIBUTION UNLIMITED

SHIP PERFORMANCE DEPARTMENT

January 1984

s DTIC ELECTE MAR 1 9 1984

P B D

D'::NSRDC/SPD-1074-01

DTIC FILE COPY NDW OTNSRDC 5602/30 12*»

laupwwdM 3960(461 84 03 13 ^>51 •-.,V

MAJOR DTNSRDC ORGANIZATIONAL COMPONENTS

DTNSRDC

COMMANDER

TECHNICAL DIRECTOR 01

OFFICER IN-CHARGE CARDEROCK

05

OFFICER IN CHARGE ANNAPOLIS

04

SYSTEMS DEVELOPMENT DEPARTMENT

11

-

SHIP PERFORMANCE DF.-AKTMENT

lb

AVIATION AND SURFACE FFFECTS

DEPARTMENT 16

STRUCTURES DEPARTMENT

17

COMPUTATION. MATHEMATICS AND

LOGISTICS DEPARTMENT 18

SHIP ACOUSTICS DEPARTMENT

19

PROPULSION AND AUXILIARY SYSTEMS

DEPARTMENT 27

SHIP MATERIALS CENTRAL

DEPARTMENT 28

DEPARTMENT 29

SPO 866 90 J NOW DTNSHDC 3960/43 l«tv 7 80)

" "mMMP<

V

^CLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE (When Dele Entered)

REPORT DOCUMENTATION PAGE 1 REPORT NUMBER

DTNSRDC/SPD-1074-01 2 GOVT ACCESSION NO

4 TITLE (end Subtitle) \Ab,4/35 oft

ESTIMATING THE SEAKEEPING QUALITIES OF DESTROYER TYPE HULLS

7 AIJTHOR/JJ

W.R. McCREIGHT

9. PERFORMING ORGANIZATION NAME AND ADDRESS

DAVID W. TAYLOR NAVAL SHIP R&D CENTER BETHESDA, MARYLAND 2008A

II CONTROLLING OFFICE NAME AND ADDRESS

NAVAL SEA SYSTEMS COMMAND (SEA 05R14) WASHINGTON, D.C. 20362

I« MONITORING AGENCY NAME « ADORESSC/1 different Irom Controlling Office)

NAVAL SEA SYSTEMS COMMAND (SEA 55W3) WASHINGTON, D.C. 20362

READ INSTRUCTIONS BEFORE COMPLETING FORM

3 RECIPIENT'S CATALOG NUMBER

5 TYPE OF REPORT 4 PERIOD COVERED

FINAL

6 PERFORMING ORG. REPORT NUMBER

8 CONTRACT OR GRANT NUMBERfJj

10 PROGRAM ELEMENT. PROJECT, TASK AREA « WORK UNIT NUMBERS

Work Unit No. 1-1561-866, Task No. T2A/-Q01

12 REPORT DATE

January 1984 13 NUMBER OF PAGES

44 15 SECURITY CLASS fo/ thle report)

Unclassified 15«. DECLASSIF1CATION DOWNGRADING

SCHEDULE

16 DISTRIBUTION STATEMENT fo/ this Report)

APPROVED FOR PUBLIC RELEASE: DISTRIBUTION UNLIMITED

17. DISTRIBUTION STATEMENT (of the ebetren entered In Block 20, II different Irom Report)

18 SUPPLEMENTARY NOTES

19 KEY WORDS (Continue on reverie tide II neceeemry ltd Identity by block number)

Ship Motion Seakeeping Destroyer Ranking Performance

20 ABSTRACT (Continue on reveree elde II neceeemry end Identity by block number)

•"' -^>A procedure for estimating the relative seakeeping ability of destroyers in head seas has been developed. Several alternate methods of ranking sea- keeping performance are considered. The data base of ship hull forms was greatly expanded beyond that of previous similar work. An improved analysis of seakeeping performance data was carried out considering a large number of parameters describing the hull geometry, including the effect of displacement. 4/

DO , :°NRM

7J 1473 EDITION OF I NOV «5 IS OBSOLETE

S 'N OI02-LF-014.6601 UNCLASSIFIED

SECUHITV CLASSIFICATION OF THIS PACE (When Oar* tnlmrmd)

TABLE OF CONTENTS

Page

LIST OF FIGURES

LIST OF TABLES.

NOTATION. . . .

ABSTRACT

ADMINISTRATIVE INFORMATION. . .

INTRODUCTION

SEAKEEPING PERFORMANCE MEASURES

HULL FORM AND MOTION DATA BASE.

HULL FORM COEFFICIENTS

REGRESSION ANALYSIS

COMPUTATIONAL PROCEDURE ....

RESULTS

CONCLUSIONS AND RECOMMENDATIONS

REFERENCES

2

5

6

8

10

10

12

U

LIST OF FIGURES

1 - Predicted Versus Computed Rank R for 180 Ship Data Base 15

LIST OF TABLES

1 - Ship Characteristics for Hull Form Data Base

2 - Independent Variables Used in Regression Analysis

3 - Ranks of 20 Ship Data Base Calculated By Five Methods. . . .

A - Sorted Ranks of 20 Ship Data Base Calculated By Five Methods

5 - Constants for Calculating Rank R1

6 Ranks R, for 180 Ship Data Base

Sorted Ranks R. For 180 Ship Data Base

8 - Regression Coefficients For Rank R.

9 - Ranges and Effects of Variables In Regression Equation .

10 - Ranges of Major Coefficients Not In Regression Equation.

16

17

19

20

21

22

23

24

25

26

>*u r- J

NOTATION

a(x)

Coefficients in regression equation for seakeeping rank

Sectional area at longitudinal position x

V

Waterplane area

Waterplane area aft of midships

Waterplane area forward of midships

Midship area

Beam

BM7

!

Vertical distance of longitudinal metacenter above center of buoyancy

Coefficient of variate X in general regression equation

Longitudinal location of cutup, aft of forward perpedicular

Block coefficient

"BA Block coefficient aft of midships

'BF Block coefficient forward of midships

BM V/BL'

Prismatic coefficient

'PA Prismatic coefficient aft of midships

ii

¥ mm .—-

-PF Prismatic coefficient forward of midships

Slamming coefficient

Slamming coefficient for ith ship

-VI

•'VP

Second longitudinal moment of sectional area about the center of buoyancy

Vertical prismatic coefficient

VPA Vertical prismatic coefficient aft of midships

VPF Vertical prismatic coefficient forward of midships

CW

CWA

CWF

Waterplane area coefficient

Waterplane area coefficient aft of midships

Waterplane area coefficient forward of midships

Difference between observed and predicted value of the response

/ F ratio

8

k

Acceleration due to gravity

Number of independent variables in regression equation

Length

XB Longitudinal center of buoyancy, aft of forward perpendicular

JCF Longitudinal center of flotation, aft of forward perpendicular

ill

T7T^^»W>-, •• I

r~"~^

Number of observations used in deriving regression equation

Number of independent variables in regression equation

Probability of slamming

Square of the correlation coefficient

Seakeeping rank calculated by Bales' method

Seakeeping rank calculated by method i

rij Response for ship i in mode j averaged over ship speed and seaway modal period

r, . Average of r. . taken over 20 ship data base

Threshold slamming velocity

Predicted value of seakeeping rank calculated by method 1

rl/3 Significant relative vertical motion at station 3

1/3 Significant relative vertical velocity at station 3

Variance

5lj Largest response for ship i in mode j taken over all ship speeds and seaway modal periods considered.

SS reg

SS res

Sum of squares due to regression

Residual sum of squares

Draft

iv

Seaway modal period

Sectional draft

Ship speed

Independent variables in general regression equation

Dependent variable in general regression equation

Average of Y

Value of Y predicted by regression equation

ASS

a, ß

\

Change in sum of squares explained by regression equation due to addition of an additional term

Constants for converting raw rank into rank

Raw seakeeping rank calculated by Bales' method for ship i

Raw seakeeping rank calculated by method j for ship i

Displaced volume

Displaced volume aft of midships

"p Displaced volume forward of midships

(£w)l/3 Significant waveheight Accession For

NTIS GRA&I DTIC TAB Unannounced Justification.

By Distribution/

Availability Codes

Avail and/or Special

hi-

"•—i

ABSTRACT

A procedure for estimating the relative seakeeping ability of

destroyers in head seas has been developed. Several alternate methods of

ranking seakeeping performance are considered. The data base of ship hull

forms was greatly expanded beyond that of previous similar work. An improved

analysis of seakeeping performance data was carried out considering a large

number of parameters describing the hull geometry, including the effect of

displacement.

ADMINISTRATIVE INFORMATION

This work was funded by the Naval Sea Systems Command under the

Surface Ship Continuing Concept Formulation Program, Task No. T2A/001.

The work, identified under Work Unit Number 1-1561-866, was performed at the

David W. Taylor Naval Ship Research and Development Center.

INTRODUCTION

For many years a need has been felt for including consideration of

seakeeping performance in the early stages of ship design, as opposed to

simply evaluating the performance of the final design. Only with the

appearance of the pioneering work of Bales on optimum seakeeping

performance of destroyer hull forms was there an attempt to give the designer

a simple tool suitable for estimating seakeeping performance on the basis of a

few hull form coefficients. However, Bales' study had several limitations,

most notably the small number of hull coefficients considered, the limited

data base, and the restriction to head seas and to a single displacement. In

this report the effects and relative importance of an increased number of hull

form coefficients are examined, the hull form data base is expanded, and the

effects of varying displacement are included. Alternate figures of merit for

rating seakeeping performance are considered. Recommendations for further

improvements, such as considering sea conditions other than longcrested head

seas and Including the effect of roll, are presented.

~x

r-w»

SEAKEEPING PERFORMANCE MEASURES

In developing a simplified seakeeplng performance model it is first

necessary to adopt a single numerical measure of seakeeplng performance. In

the present report four such figures of merit are considered. The first is a

modification of Bales' rank R„, the second is based on evaluating the

limiting seakeeping performance in a seaway, the third is based on a simple

average motion response and the fourth is a further variation on the Bales

rank.

Bales developed a measure based on a combination of eight motion

responses for unit significant wave height in head seas which were averaged

over a range of ship speeds and seaways. These responses were: (1) heave

(measured at the longitudinal center of gravity), (2) heave acceleration,

(3) pitch, (4) relative motion at the bow (5) absolute acceleration at the

bow, (6) absolute motion at the stern, (7) relative motion at the stern, (8) a

slamming coefficient, C , measured at station 3. The slamming coefficient

is defined in the following way. The probability of slamming is given by

XPf" ( Cl/3 ) + \ h/3 ) (1)

where t is the local draft, ft is the threshold velocity defined by OchiS

3.66 m/sec (12.0 ft/sec) for a ship 158.5m (520 ft) long and Froude scaled to

other ship lengths to obtain, in metric units, ft = 0.291 . T", and r^/^

and rw-j are the significant single amplitude of relative motion and

relative velocity, respectively. This is rewritten

ps = expj-2Cs/(Cw)1/3| (2)

]

and thus

/—L—y + u_-— (3)

Each of these responses was averaged over a range of Froude numbers,

(V/.gL = 0.05, 0.15, 0.25, 0.35 and 0.45), and modal periods, (T = 6.0, 8.0,

10.0, 12.0 and 14.0 sec.). Then these average responses were combined for each

ship into a raw rank p ,

B

7

E j = l

mint r k=l , 20 ( kj

C s. l

max C , k=l, 20. sk

where r ij

ij

is the jth average response, as enummerated above, for the ith

(A)

of 20 ships and C is slamming coefficient for the ith ship. Summing

the inverse of the averaged responses, except for the slamming coefficient,

yields a measure which is larger for ships with better performance. As can be

seen from Equation 2, a larger C results in a Lower probability of slamming

and consequently each of the averaged responses is normalized with respect to

the best value of that response among the set of 20 ships considered.

Finally, these raw ranks, ,R, are scaled linearly so that they range from

1.0 to 10.0. The resulting Bales rank, R„, considerably exaggerates the

differences between ships since the raw ranks, p_, range from 0.799 to

0.953. This procedure can be justified because interest is in the variations

in performance and the raw rank tends to be dominated by contributions from

responses which do not vary by a large percentage over the data base.

Four alternative figures of merit for rating seakeeping performance

were examined. All are based on the first seven of the responses per unit

wave height described above together with a modified slamming coefficient

18 1

\ri/3/ rri/3/

•1/2

«w>i?3 (5)

where C is as defined previously. This form of the slamming response has

the logical and computational advantage over C that it is also a response

per unit significant wave height such that a large value represents better

performance than a small value and thus is consistent with the form of the

seven other responses. The four methods represent alternate ways of combining

the responses. The first is Bales' method with the redefined slamming

coefficient.

•T Z min{r . , k= 1 ,20} kj

(6)

The second is an attempt to base the ranking on limiting seakeeping

performance. Instead of averaging each of the seaway responses over speed and

heading, the largest value, denoted s. . for the ith ship and jth response,

is taken to represent the ship's performance.

1=1

minis ,,k=l,20} kj

s. . (7)

The motivation for this approach is the observation that the inverse of a

response per unit significant wave height is proportional to the limiting

significant wave height if there is a specified maximum allowable value for

that response. Consequently, 1/s. . is proportional to the minimum limiting

significant wave height over all speeds and modal periods for that response.

The thira rank is simply the average response normalized with respect to the

minimum response,

1 T

8 r . .

iin(rkj ,k=l,20) (8)

The fourth method is the same as the first with each response normalized with

respect to the mean response rather than the minimum.

h = -r t U (9) ij

•i

f"~ "-'Mi

where

20

iJ 20 2^, kj (10)

k=l

These were tried to examine the effects of these alternate normalization

procedures. In all cases the resulting raw ranks are scaled from 1 to 10 for

the worst to the best.

In the evaluation of Equations (6) through (9) the required minimum

and mean responses are evaluated for the 20 hull forms of the original Bales

data base at a displacement of 4300 tons only. These values are then retained

while ranking other hull forms at this displacement and all hull forms at

other displacements so that the ranks will be consistent. Similarly, in

scaling the raw ranks the scaling constants are calculated using only raw

ranks from the original 20 hull form data base at 4300 tons displacement and

are retained for the remainder of the computations.

HULL FORM AND MOTION DATA BASE

A data base consisting of motions data for 45 destroyer-type hull

forms was computed. The characteristics of these hulls are listed in Table

1. The first 20 hulls are the 20 hulls of the Bales data base.1 Hulls 21

through 27 are from various sources, including proposed ships and one

constructed ship. In particular, ships 21 and 22 are Bales optimum and

anti-optimum hulls respectively, ship 25 is the U.S. Coast Guard HAMILTON

Class High Endurance Cutter and ship 26 is ship 6, the best of the original 20

hulls, modified to increase the length to beam ratio 15 percent while holding

the beam to draft ratio constant. The remainder of the hulls are taken from

two systematic series of hulls which have been tested for seakeeping ability,

ships 28 through 31 from a recent unpublished series and ships 33 through 45 are 3

from Schmitke and Murdey .

' *Documented in a NSMB report by Blok with a restricted distribution.

5

~—•

Some of these additional hullforras are somewhat outside the range of

typical forms of actual ships. This is an advantage because the resulting

estimator will be valid for predicting the effect of hull geometry on

seakeeping rank for the extended range of hullforms. The only limitation

compared to Raits' approach is that it will not be possible to use the maxima

and minima of the data base hull coefficients to define a hull as he did in

deriving his optimum and anti-optimum hulls. This Is a somewhat questionable

method of obtaining "practical" hulls in any case due to the correlations

between the various parameters.

The root-mean-square responses in longcrested head seas were computed

for a very large range of speeds and modal periods, in most cases for a

displacement of 4300 metric tons. The modal period range in particular is

extreme but allows the scaling and interpolation of the responses to any

desired displacement by the procedure described below. The responses

calculated are those required for the ranking procedure, that is, the first

seven responses as listed in the section describing this procedure together

with relative motion at station 3 and relative velocity at station 3.

HULL FORM COEFFICIENTS

Bales investigated the effect of a small number of parameters

selected on the basis of experience and intuition, and retained all of them in

his model. These were:

1) Waterplane area coefficient forward of midships, Cy.,;

2) Waterplane area coefficient aft of midships, C,,;

3) Draft-to-length ratio, T/L, where T is draft and L is ship

length;

4) Cut-up ratio, c/L, where c is the distance from the forward

perpendicular to the cut-up point;

5) Vertical prismatic coefficient forward of midships, C„pF;

6) Vertical prismatic coefficient aft of midships, C ;

In this report all of the above coefficients are considered, except

for c/L, together with the following additional coefficients:

i

1)

2)

3)

A)

5)

6)

7)

8)

9)

10)

11)

12)

Length, L;

Beam, B;

Draft, T;

Block coefficient, Cß;

Block coefficient forward of midships, C ;

Block coefficient aft of midships, C_ ;

Prismatic coefficient, C ;

Prismatic coefficient forward of midships, C ; r r

Prismatic coefficient aft of midships, C ;

Vertical prismatic coefficient, Cup;

Waterplane area coefficient, C„;

The height of the longitudinal metacenter above the center of

buoyancy, BMT ;

13) The longitudinal center of buoyancy aft of the forward

perpendicular, L ; CB

14) The longitudinal center of flotation aft of the forward

perpendicular, L ;

15) The second moment of the hull volume about the L„„, denoted

cvr

Various combinations of these were also considered. A full list of the

variables used and their definitions are listed in Table 2. All dimensions

are in metric units. The cut-up ratio c/L was eliminated because (a)

preliminary analysis with an expanded set of coefficients indicated that with

an adequate selection of more conventional coefficients c/L did not appear in

the equation, (b) even with the original set of coefficients c/L had little

effect, and (c) in many cases it is not easy to define the location of c even

from a set of hull lines; with automatic calculation of coefficients by the

computer as used in this investigation it is even more difficult. All of the

coefficients included can be calculated from the principal dimensions L, B,

and T, and the waterplane and sectional area curves.

»-

REGRESSION ANALYSIS

Regression analysis provides a means of determining the relation of a

dependent variable to a number of independent variables. It can be used to

summarize a large mass of data in a compact functional form. In simple terms,

it consists of determining a least squares fit of an assumed functional form

(the regression equation) involving the independent variables to the dependent

variables, together with various measures of the overall goodness of fit, the

importance of the various independent variables, and the validity of the

calculated parameters in the model. For the case of linear regression, the

dependent variable Y is approximated by a linear combination of independent

variables X, plus an error term e

Y = 3 + B.X. + o 1 1 . + B X + e

n n (11)

The coefficients B. are chosen to minimize the total square error

I>2 = E (Y - Y)' (12)

where the summation Is over all observations. The goodness of fit can be

measured by the square of the correlation coefficient

2 1T(Y " Y>' r - l - -** £<Y - Y)2 (13)

where Y is the mean response

-T2> (U)

This gives the proportion of the variance

77,2

8

(15)

•**m» :•

which is explained by the regression equation and clearly a larger value of 2

R is better. The magnitude of the standard deviation, s, is another

indication of the goodness of fit. The significance of each coefficient B.

can be judged using the statistic

F = SS

res

ASS/1

m -1 TT (16)

where

SS = Y* (Y - Y)' res <*—'

(17)

and ASS is the change in the quantity

^2 SS - Y] (Y - Y)

reg £~i (18)

I

due to the addition of the X. term to the regression equation, N is the

number of observations and k. is the number of independent variables in the

equation. This ratio follows an F distribution with 1 and N-k-1 degrees of

freedom. If the computed F ratio exceeds the critical F ratio obtained from a

table for a given significance level the variable is said to be significant at

this level. See, for example, Draper and Smith for a detailed discussion.

The computations were carried out using an available set of computer

programs, the Statistical Package for the Social Sciences . Except where

noted, a stepwise procedure was used in which terms are entered into the

regression equation one at a time, at each step selecting the variable which

gives the greatest reduction in the error subject to the condition that the

tolerance, or proportion of the variance of that variable which is not

explained by the variables already in the equation, is greater than a

specified amount. If at any step a variable in the equation fails a

significance test, it is removed from the equation.

• •

r •"

COMPUTATIONAL PROCEDURE

The ship motion reponses for the range of conditions described above

are computed for each ship in the hull data base using the strip theory ship

motion computer program PHM* and then merged onto a single file. This file is

then used as Input by a ranking program which reads the ship motion data base,

scales the responses for each ship to a specified displacement, interpolates

the data to obtain responses at specified speeds and modal periods, calculates

the seakeeplng ranks as described previously, calculates the hull coefficients

described previously, and generates a data file containing the ranks and hull

coefficients in a format suitable for the regression analysis program. The

scaling and interpolation procedure is based on the fact that for a specific

Froude number VA gL and nondimenslonal modal period T • g/L, linear

displacements per unit waveheight are independent of ship length L. Angular

displacements per unit waveslope are also independent of L, thus angular

displacements per unit waveheight are inversely proportional to L. The -1/2 -1

velocities and accelerations are proportional to L and L

respectively times the shiplength dependence of the displacements. Thus it is

easy to scale the responses appropriately to a new displacement and

interpolate to obtain the responses at the required speed and modal period.

This program has an option for reading in previously generated minimum or

averaged responses and rank scaling factors as described above. The program

also has an option for weighting the responses for different speeds and modal

periods. This option was not used in the current investigation. This

procedure was carried out at displacements of A300, 5800, 7300 and 8800 tons

and the resulting data files were merged. Finally, the regression analysis c

was performed using the SPSS package.

RESULTS

U I

!

The rankings R., R?, R-, and R as defined by Equations (6)

through (9), for ships 1 through 20 at a displacement of 4300 tons are

presented in Table 3, together with the Bales rank R as computed from the

data in his paper. Table 4 presents the same data with the ships sorted by

rank. It can be readily seen that the various ranking methods give nearly the

same results.

*Docuraented by Hubble in a report with a restricted distribution.

10

TTZT

I

Table 5 lists the values of mln{r. ., k-1, 20} required to calculate

the raw ranks p. using Equation (6) for an arbitrary ship and the linear

scaling constants a and ß required to convert this raw rank to the rank R

using the formula

Rj = IP. + ß (19)

The rank R.. , as obtained using raw ranks defined by Equation (6),

calculated at displacements of 4300, 5800, 7300, and 8800 tons are presented

in Table 6. The same data with ships sorted by rank is presented in Table 7.

It Is readily seen from Table 7 that while increasing displacement

increases the ranks of the hull forms, the relative position of the hulls at a

given displacement is not much affected for most hull forms. It is also of

interest to note that the best hull, ship 29, performs better at 4300 tons

displacement than the 20 worst hulls at 8800 tons. However, considering only

the original Bales 20 hull data base, this is no longer the case.

Lon ships with full waterplanes perform best in head seas. The

four best hulls, ships 28 to 31, have the lowest block coefficients in the

series, which results in increased waterplane area for a given displacement.

A stepwise regression analysis was performed on the 180 ship data

base consisting of the 45 hull forms each evaluated at displacements of 4300,

5800, 7300 and 8800 tons. The specified F ratio for entering of variables was

3.89 and for removing variables, 3.889, corresponding to a 5% confidence

level, and the specified tolerance was 0.10. The resulting regression

equation is

!1 = a0 + alBV + a2CVPF + a!CVPA + V'l + '5L

+ a6T/B + a^ /V 2/3

+ VLCB " LCF)V (20)

1/3 + a9072 - LCB)/V"

J + a10LVBT

where Cj = BMj /BL3

11

'

The coefficients a. are listed in Table 8. The standard deviation is 21

0.55975 and the K is 0.99533. Figure 1 presents a plot of R versus R.

for the 180 ship data base. The minimum and maximum values of the variables

are listed in Table 9. The effect, or difference of maximum and minimum

values times the corresponding coefficient, is also presented in Table 9. The

effect, or difference of maximum and minimum values times the corresponding

coefficient, is also presented in Table 9. In applying Equation (20) the

variables should, strictly speaking, lie within these ranges for the equation

to be valid. Other nondimensional variables should also lie within the ranges

for the data base. These limits are listed in Table 10. Note that because of

the correlation of the various hull form parameters it is not possible to

simply regard each coefficient in the regression equation as indicating the

relative importance of that variable independently of the others.

CONCLUSIONS AND RECOMMENDATIONS

A procedure for quickly estimating the relative seakeeping

performance of a destroyer-type ship in head seas has been developed. This

method, which is a considerably improved version of one developed earlier by

Bales , requires only quantities easily calculated from the length, beam,

draft and sectional area and waterplane curves. In applying this method it

should be noted that small differences in predicted rank should not be

considered significant, due to the small errors in fitting the equation to the

data base. Some evidence was also found that the interpolation procedure used

in scaling the motion data base responses to a specific displacement also

introduced some variation in the calculated ranks.

The exact form of the raw performance rank calculation does

not greatly alter the relative ranking of the ships. Variation of hull

displacement also has a relatively small affect on the relative ranking.

Generally for a given displacement, long ships with large waterplane area

perform the best.

12

rrr

r-mm

Extension of the procedure to include the effects of roll is clearly

desirable. However, there will be some difficulty in carrying this out. A

much more extensive data base must be generated. Meaningful measures of roll

response must be selected for inclusion in the rank. The principal

difficulty, however, will be choosing parameters to be included in the

regression equation. It will not be possible to use only overall geometric

quantities of the hull. Mass distribution properties such as the vertical

center of gravity and the roll radius of gyration are obviously important.

Many small details of the hull such as rudder, skeg, and bilge keels will also

be quite important. One possible approach would be to use roll natural period

and roll damping, perhaps as estimated by some simple procedure, as

independent variables in the regression analysis.

Another useful development of the present work would be to derive

regression equations for criteria-based rankings for specific design projects

based on a (pre-computed) hull and motion data base together with the

seakeeping criteria for the specific design.

Finally, extension of even the present approach to other hull forms

would also be of considerable value to the Navy.

1 I

REFERENCES

1. Bales, N.K., Optimizing the Seakeeping Performance of Destroyer-Type

Hulls, Thirteenth Symposium on Naval Hydrodynamics, Tokyo, Japan,

October, 1980.

2. Ochi, M.K., Extreme Behavior of a Ship in Rough Seas, Trans. Society

of Naval Architects and Marine Engineers, Vol. 79 (1964).

3. Schmitke, R.T., and D.C. Murdey, Seakeeping and Resistance Trade-Offs

in Frigate Hull Form Design, Thirteenth Symposium on Naval

Hydrodynamics, Tokyo, Japan, October, 1980.

4. Draper, N.R., and H. Smith, Applied Regression Analysis, John Wiley

and Sons, New York, 1966.

5. Nie, N.H., C.H. Hull, J.G. Jenkins, K. Steinbrenner and D.H. Brent,

Statistical Package for the Social Sciences, 2nd. Ed., McGraw-Hill,

New York, 1975.

6. Hohlen, Mina, SPSS-6000 Release 8.0 Update Manual, Document 457,

Vogelback Computer Center, Northwestern University, Evanston, 111.,

July 1979.

14

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I If)

u

'

TABLE 2 - INDEPENDENT VARIABLES USED IN REGRESSION ANALYSIS

2/3

V

\'A

\'A/AW

V

AWF7

2/3

!/3

B/L

iML

BM,

BMLV"

BM V

BL3

BMJ2

BL3

B\/?l/3

BT

B/T

B/V 1/3

CB ' LBT

c .&. BA LBT

C 2V,

TOT

cp X

2V_ JPA L. s JPA'

JPF LAV

CPF-

n =j^(x-LCB)2a(x)dx

VP TAw

A VPA TAWA

F VPF TAwf

\ JW LB

!AW "WA LB

I 17

-~r:~ g

TABLE 2 (Continued)

1111 —

"WF LB

L/B

L/T

L/71/3

L2

BT

LCF^ .'/ J

LCB" •LCF

(LCB " LCF^

(LCB " V 1.

~2~ LCB

L 2 1 •(•!••

1/3

T.

B

T/'. 1/3

1/3

,2/3

L3BT Cr

BMtV (T - '•<,)

ft*)' (T - K»)

"CB A/

LCB7 T/B

W ,1/3 T/L Y/v

JCF

LCF-

TC.

R) i«

!

!

if in o ^ p^ t> y, K<=»if'">r»cc'ir. *'*'K«Cflrfl>.

LT\ tf\ «0 lf\ CT O lf\ -J CV CC If. K O N. ,-) fv- J-XN-O ^ rWrtlfirl04ff''MKT<NO*ff'ClM.9>>C

^^a,'Clfffo'4^'Noa^o^JU>(^',l^J^0,

»-j if H ^ ^. o i^ t tf i0 j o c c t r« n ^ j) H

cosc'^cru,'accro<rifitn(i;cc<roa)rr:rcr>-!r K K .» ro J- o s j t ir j Hirtrj^jNK)

t<? 40 (v.C'<T«i,fv.»-N:^oifa.-vt.c.-»cr^«e- os!\,rircirrjO(7»<acswfi,Mf1jj *~u<Cf\.<£o^ocevi Kjc: if if n J f~ «c fv.

KSjrifojicirtif.jr'ifo-jc^Nj

nni'HNSsi n is c T- ~z> o c o v 3 x c

# T <r r- C - r > n T a *i = t. v r J« *! * r

5> 1\ » u r. -t — c• r -t ~ * "Vi

c -0

«i cv, f- ju OJNOCO C^N^ j u it s «r o c ,j -J «-< ** »•> »-I r-

i

19

n o ir ri c «-< <T M c\. o a ."^ r*- «-< O cr ^ tv• ir rj o as *• . . . .

Q, vrivrNC1»-1^ or ,j»-irc,r. sice''? Jf^

a

w * if S o r a- « j ^ o ip Mf K r * K c (TK'

«H «H »-I »-I.-I »-I »-< »H fVJ v>4 v-4

e-iCc«-o *-• vc IT f «^ ^ i ff * * •> W o K C

o^Kittfi^eKfo**'1'»'»1**"*

c-tror r SP> wv ii'ii1 •> #*#**'' w ftj *•«

to \r ir. h- e- r- »< «r .y «- ir •r j- e- f

i pa

as

9 L x. <v r. r •*• c- ^»cxy^iT"— -t IT ^- x o o if r c 4 •* J u' ~ t O >* A* Jf> C C 'J* —• < c

» =? t\ r, z> -5 .* c *i r- c O»J-'M,ON3 c x •: • > >* > r * ••> =: i f T A r j » N ^ c

= 7« S X r» 4 <6 i. a •» •» -a •* » •*' <"" X X »i

a t m • N •- X t, I * m c & t- X x C « .» J. .»)

20

A** i

TABLE 5 - CONSTANTS FOR CALCULATING RANK

Response j minir, ., k= 1, 20}

1 0.22430351

2 0.21245666

3 0.47220716

4 0.89245372

5 0.74351939

6 0.49375601

7 0.42188321

8 0.093131903

56.047364

-44.362856

21

T77

TABLE 6 - RANKS R, FOR 180 SHIP DATA BASF.

Ship

1 2 3 •» 5 6 7 a 9

11 12 13 1- 15 lb 17 16 19 2 0 21 22 23 2* 25 26 27 28 29 30 31 32 33 3* 35 3b 37 38 39 ki *1 -•2 *3 ** 1.1

4300 tons 5800 tons

7. &moi 7.58579 *. 133?«. 3.22289 5.33692

i J.bOuJ J ••.•»0139 b.e3325 5.C2392 3.61591 5.-3713 *.b6*9* 1. 0 0 0 C d b.?3b7S 9.t3b?b *, 32626 3. 731.7c 3.fc735b 2. E 3 3 !» 7 t. 19?«.8

7300 tons 8800 tons

1*.5lb59 -1. 8*t9J

&,&ä*9* l.*5H3 *.5l33*

1*.793^3 11.712-7 19. 06**1 19.15367 I7.w92w6 17.293-3 5.5 155 - *. 67936 2.6,31b

10.7*717 9.25b3b 7.25*36

li.50343 1Ü.2o333 8. *52b2

1>.87611 l5.t991o 13. ».3368 3. 8u363 8. 1573«

12 12

a 7

ID 15

9 11

9 13 1.,

9 5

11 It

8 13

8 7 8

2Q 1

1 J 5 3

21 17 25 26 23 23

9 8 6

15 1«. 12 16 1«. 12 21 21 18

3 13

o 315 3 573*1 62*71 *652u 13528 51377 1*753 73631 7622? 60778 113*3 25 509 06195 53299 65753 3*326 99o&5 33*0C

22963 33* 10 *S91J 993*» 96522 20265 99383 3270«» 13187 773*9 u230b 79**5 38790 2719: 91793 57252 9**15 3*133 16515 01296 7*25* 30993 *9o98 59313 d6*10 237J8 o3233

17.2 17.1 12.7 11.3 1*.* 20.5 13.3 16.2 1*. C 18.5 1*.3 13.* 8.7

16. J 19.7 12.9 18.7 11.9 11.1 13. i) 25.9 5.*

1*. 9 3.5

13. 27 22. 31 32. 29. 28 12. 12.5 10.1 23.6 16.9 16.6 23.1 13. 3 16.7 26.b 26.9 23.7 12.2 17.*

5579 122* 1937 3088 9*35 365* 9J66 2179 3975 *!»5 1 9321 3860 6019 9197 953*. 5015 9272 939* 938C 7059 2*07 7303 ±2*2 12*8 677* 7662 all3 5221 *3*9 67U7 3371 3778 7988 2*72 953* 67Q6 5*63 1079 0 5 76 -.897 lb*2 82C3 98Ü1 o**8 8859

21.5*9*9 21.31736 16.53637 1*.93391 13.5**5U 25.2C995 17.3363? 20.39315 13.12*13 22.95986 13.379*2 17.36363 12.20565 23.3*131 2*.38926 16.775*3 23.258*7 15.67??6 1*.383*1 17.02190 3J.97*79 3.7025*

13.63*1* 11.78232 16.3*375 32.80913 26.6W05P 37.72539 33.26109 35.003*9 3-*. 1113«. 15.72313 15.97559 13.U1562 25.12702 23.31873 23.86029 23.91178 22.57L39 20.39333 31.37223 32.00958 23.38670 16.07073 21.66331

22

TT^

TABLE 7 - SORTED RANKS R FOR 180 SHIP DATA BASE

4300 tons

Ship

29 19.15367 ?8 19.064tl 30 17.*9218 11 17.29843

«•1 15.37611 *2 15.69910 26 l«i.79393 21 1*». 51659 43 13.'•3368 2? 11.71247 38 11.60313 35 10.7*717 39 10.26808

& 10.00000 15 9.-*3636 36 9.25556 17 8.73470 10 8.61691 «0 8. r52b2 15 8.157CJ

? 7.58579 1 7,54101

3 7 7.25t»36 8 6.80826

23 6.:>8<*9* 14 6.53675 32 5.51580 11 5.t3713

5 5.33692 9 5.02092

33 4.37936 12 •• .o 8«*94 25 «•.5133««

7 4.48139 16 «».32626 20 4.192U4

3 «•.1382«« <•*• 3.80363 19 J.67356

(* 3.22289 19 2.888*7 34 2.64816 24 1.45185 13 1.00000 22 -1.84690

5800 tons 7300 tons 8800 tons

hip Rl Ship 1 s Ship Rl

29 26. 02306 29 32, 34349 29 38. 26109 28 25. 7 7 809 28 31. 9 5221 28 37. 72689 30 23. 79 44 5 30 29. :>87W 30 3b. 30019 31 23. 38790 31 2». 93871 31 34. 11101 42 21, 59313 26 27. 27662 26 32. 80913 41 21. 49698 k2 26. 9 8203 42 32. 30958 26 21. 32704 11 26, bl642 41 31. 37223 21 20. «•8910 21 25. 92407 21 30. 97479 (•3 16. 66411] <i3 23. 79801 43 2e. 38670 27 17. 13187 27 22. 0 611 3 27 2b. 6405e 38 16. 01296 35 20. 69531 6 2b. 20995 55 15. 94415 6 ?0. 53654 35 25. 1270?

6 15. 51377 38 20. 11J 79 15 2k. 38926 15 11, 85 75 8 15 19. 79534 38 25. 91178 39 14, 74254 36 18. .98706 36 25. 31870 36 11. 34133 39 18 ,8057b 17 23. 25847 17 13. 99665 17 18. 79272 10 22. 95S86 10 13. 8 0 77« 10 18, 5 4451 39 22. 57439 *5 13. 0 323 3 15 17. ,*8859 45 21. 66031 40 12. 80998 1 17. 2 5579 1 21. ?4949

1 12. 63153 2 17. 11224 2 21. 31736 2 12. 57641 40 lb, 74897 37 20. 8602<»

57 12. 16515 37 16. b&463 8 20. 39315 8 11. 73631 8 16. 22179 kl 2J , 39038

14 11. 5 3299 14 16. P9197 14 20. 34101 23 10. 96522 23 14, i k2k2 23 18. 63416

5 10. 1 352 H 5 1«*. '4 94 35 5 14. 5445* 11 10, 11849 11 14. 39321 11 18, 37942

9 9. 76225 9 14. 08975 9 16. 12410 52 9. 27190 12 13. 43860 12 17. 36368 12 9. 25309 7 13. 39066 7 17. 3363?

7 9. 1475^ 20 13. .07059 20 17. 02193 25 8. 99883 25 13 ,0677* 26 lb, 84375 33 8. 91798 16 12 ^6015 16 lb. 77548 16 8. 8*4026 3 12. .71937 3 16. 53637 20 «. 8 3410 32 12. fc3778 44 lb. 07073

3 8. 62471 33 12. .57988 33 16. 97559 44 8. 2 370 8 44 12. 28448 32 15. 72318 19 8. 0 3405 18 11, 99394 18 16. 67226

4 7. «•6520 4 11. 33089 4 14, 93091 19 7. 22960 19 11. 19080 19 14. 88311 14 6. 57252 34 10. 12472 34 13. 41562 24 5. 20265 13 8, 76019 13 12. 20 565 13 5. 06196 24 8. bl248 24 11. 78202 22 1. 9934«* 22 6, ^7303 22 8. 70254

23

TABLE 8 - REGRESSION COEFFICIENTS FOR RANK R 1

9.43595

3.10450 x 10"

-8.42980

-37.5995

590.435

0.287418

-57.3460

'10

-6.08436

9.18775 x 10

-6.03225

-6.41495 x 10

-5

-3

I '

24

j

m

TABLE 9 - RANGES AND EFFECTS OF VARIABLES IN REGRESSION EQUATION

BMLV

CVPF

CVPA

BM 7

BL"

L

T/B

2/3

(LCB " LCF)V

(* - LCB)A

1/3

V_ BT

Maximum

.57447E+07

.82136

.69651

.52757E-01

187.25

.39201

4.6232

-9355.3

.41964E-01

406.00

Min imum

.85042E+06

.54486

.45657

.36905E-01

108.07

.19182

2.6691

-87181.

-.45002

149.00

Effect

15. 19

2.33

9.022

9.360

22.76

11.48

11 .89

7.150

2.968

1.649

25

r^^ ....

TABLE 10 - RANGES OF MAJOR COEFFICIENTS NOT IN REGRESSION EQUATION

2/3

V Vv'

^A

\A/AW

B

B/L

BML

BML72

BV2

73

BLJ

BM^V

BT

L2

B/T

1/3

Max imum

3133.9

.2 6880E+08

7.4791

1937.2

.62729

.16616E+08

1311.3

.44826

.11248E+0D

3.1295

25.850

.18621

669.7 5

.49274E+11

452.51

32.719

.67114E-02

5.2133

Minimum

1166.3

.48883F.+07

4.4867

693.83

.55174

.2 9080E+07

472.49

.37271

.19803E+07

1.8176

12.686

.89295-01

202.91

.35643E+10

154.68

1 2 . 58 5

.24631E-02

2.5509

26

—————

TABLE 10 (Continued)

B/V

CB

CBA

CBF

""PA

CPA7

'PF

C 7 LPF

VI

CVP

r SlA

CWF

L/B

L/T

1/3

1/3 L/V

L IT C B BM, V

Max imum

1.2628

.55266

.60320

.53763

.68714

.75355

6463.4

.66037

5664.2

1692.9

.74431

.82675

.99277

.69802

11.199

36.000

9.1473

86.341

Minimum

.78682

.39786

.45327

.33129

.57263

.60989

2556.2

.52162

2186.2

518.39

.50278

.69857

.83004

.55957

5.3702

22.000

6.7027

34.231

••

27

' —.-:

, LCB

LCBV

1

1 LCFV

1 /J/3 LCF/v

l. LCB " LCF

1 <LCB " VV

1 -. j T - LCB

1

T LCF

B i

• (T - LCB) '

,

(T - g' f T

I r/L

i TCB

1/3

TABLE 10 (Continued)

Maximum

7454.7

97.368

.83516E+06

4.7566

104.43

.89572E+06

5.1016

-2.2321

-.13844

.85901

-4.7973

7368.0

-20106.

6.5317

.45107E-01

4.5614

Minimum

1171.8

56.423

.23648E+06

3.4996

60.466

.25343E+06

3.7503

-10.164

-.49654

-9.2120

-16.081

-79014.

-.13793E+06

3.5788

.27578E-01

2.1562

28

"^

1

TABLE 10 (Continued)

TC„ v2

R) TV B

T/V

V

vl/3

„2/3

1/3

V"

7.

V./V A

VF/7

Maximum

20.806

3362.4

.31908

8577.3

20.470

419.02

.73571E+08

.63104E+12

5031.0

.58655

4228.5

.49298

Minimum

4.6494

803.94

.22197

4191.2

16.123

259.95

.17566E+08

.73623E+11

2125.2

.50706

1732.9

.41346

29

_.

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