Navigation:  Speed/Power Analysis > Ct-based Holtrop Prediction > Output

After clicking OK in the Holtrop Speed/Power Analysis dialog box, a separate report window will open with the displacement hull analysis results providing the following output values:

 

Prediction Parameters

 

Method: a modified version of the 1984 Holtrop analysis.

 

SpeedCheck: a check of the extents of the entered speeds by comparing it to the minimum and maximum FnBch range.

 

HullCheck: a  check of deadrise angle, LCG/Bch ratio, and CLb to be sure that they fall within appropriate ranges.

 

DesignMarginPercent: the user-defined margin used to account for the differences in the current model and the final design.  This can also be used to account for loss of efficiency due to wind, waves, appendages, shallow water, etc.

       

DesignSpeed: the user-defined “operational” speed of the vessel.  This speed is used in the drag reduction sensitivity analysis.

 

WaterType: the type of water used in the displacement hull analysis.  This can be changed in the Orca3D Properties dialog box.

 

WaterDensity: the density of the water used in the displacement hull analysis in the units specified.  This can be changed in the Orca3D Properties dialog box.

 

WaterViscosity: the viscosity of the water used in the displacement hull analysis in the units specified.

 

FormFactor: the factor that accounts for the three-dimensional effects of the hull shape and appendages.

 

CorrAllowance: an allowance used to account for differences in extrapolation methods, hull roughness, and scale effects.

       

Propulsive Efficiency: the user-defined propulsive efficiency used in the analysis.

 

Vessel Data

 

This section provides calculated and user-defined values defining the displacement hull being analyzed.

 

LengthWL: the waterline length of the displacement hull in the units specified.

 

BeamWL: the waterline beam of the displacement hull in the units specified.

 

MaxMoldedDraft: the maximum molded draft of the displacement hull in the units specified.

 

DisplacementBare: the user-defined bare hull displacement in the units specified.

 

WettedSurface: the wetted surface area of the displacement hull in the units specified.

       

MaxSectionArea: the maximum sectional area value for the displacement hull in the units specified.

 

WaterplaneArea: the waterplane area of the displacement hull at its defined condition in the units specified.

 

LCBFwdTransom: the longitudinal center of buoyancy of the displacement hull measured from the transom in the units specified.

 

BulbAreaAtFP: the area of the bulbous bow at the forward perpendicular in the units specified, if applicable.

 

BulbCentroidBelowWL: the distance to the centroid of the bulb measured from the defined waterline in the units specified, if applicable.

 

TransomArea: the area of the transom of the displacement hull in the units specified.

 

HalfEntranceAngle: the half-angle of entrance of the load waterline.

 

SternTypeCoef: the stern type coefficient accounting for the specific shape of the afterbody.

 

Parameter Check

 

This section verifies the following calculated parameters are within a defined range to ensure accurate results.

 

FnMax: the maximum calculated Froude number based on the design speed and the waterline length.

       

PrismaticCoef: the calculated prismatic coefficient of the displacement hull.

 

LwlBwlRatio: the ratio of the waterline length to the beam at the waterline.

 

LambdaCoef: the mean wetted length to wetted beam ratio of the hull.

 

BwlDraftRatio: the ratio of the beam at the waterline to the defined vessel draft.

 

Results Tables

 

The two tables provide the following results for each of the user-defined speeds:

 

Fn: the calculated Froude number using the waterline length and the corresponding speed.

 

Cf (x 1000): the frictional resistance coefficient at the corresponding speed multiplied by 1000.

 

Cr (x1000): the residuary resistance coefficient at the corresponding speed multiplied by 1000.

 

Rbare (N): the predicted bare hull resistance at the corresponding speed.

 

PEtotal (W): the calculated total effective power of the vessel including the design margin at the corresponding speed.

 

Rtotal (N): the total predicted resistance including the user-defined design margin at the corresponding speed.

 

Fv: the volumetric Froude number for the corresponding speed defined as Fnv = Speed/ (g*DisplacedVolume⅓) ½

 

PPtotal (W): the calculated total propulsive power of the vessel dependent on the user-defined propulsive efficiency.  For example:

 

 

 

PPtotal is defined as the total effective power divided by the propulsive efficiency and will be representative of the power defined by the propulsive efficiency input.

 

Prediction Check: at each speed the predicted condition of the vessel is checked against known valid ranges for the modified Holtrop method.  The output is either OK, or specifies “Check=” followed by the number 1 through 3.  The report provides the definition of each type of warning under the Prediction Checks section.  We caution against using results where a prediction warning is found.

 

Sensitivity Analysis

 

The report provides a sensitivity analysis to reduce drag performed at the design speed.  A sensitivity index with a higher value has a greater influence on drag.  A value greater than 1.0 is considered significant.  The third column of the table indicates if the value should be increased or decreased to reduce drag.

 

Results Plots

 

The last page of the report provides plots of bare and total hull resistance versus speed, total effective power and total propulsive power versus speed, and the residuary resistance and frictional resistance coefficients versus speed.