Instructions to participants
Case 5.1: ONRT, forces & moments

CASE 5.1 (case 5.1.1 and 5.1.2)

1. Description of case 5.2

  • ONRT hull shape
  • Fixed in surge, sway, roll and yaw. Upright condition (Ø=0). The experimental results are obtained free to trim and sink.
  • Calm water
  • Deep water. The results will be compared to experiments carried out at a water depth to draught ratio 31.25.
  • LWL = 3.147 m (scale 48.9355)
  • Vmodel=1.111 m/s, Fn = 0.20 (corresponding to full scale 15.1 knots)
  • Towing tank temperature during the tests:
    Month Temperature [ºC] Density [kg/㎥] Kinetic Viscosity *10-6 [㎡/s] Test
    5 17.4 998.72 1.0703 Static drift test
    6 19.4 998.32 1.0183 Rudder test
    7 21.3 997.94 0.9726 Pure sway test
    8 23.5 997.4 0.9238 Pure yaw test
    9 24.7 997.09 0.8987 Yaw with drift test
  • Propellers present. The propeller should work at the propeller point so that there is self-propulsion at Vmodel=1.111 m/s, Fn = 0.2 (corresponding to full scale 15.1 knots). During the model tests, the propeller was working at 528rpm (= 8.8 rev/s).
  • Rudder s (spade type) present, but at zero rudder angle (exactly zero) for the pure drift and the drift/yaw tests.
  • The attached fin stabilisers were passive and at zero offset angle during all captive tests.

2. Experimental data

The submissions will be compared to model tests carried out by SNU (Seoul National University Towing Tank Laboratory) in 2018. Reference: J. Seo, D. H. Kim, J. S. Ha, S. H. Rhee, H. K. Yoon, J. Y. Park, W. Seok and K. P. Rhee. “Captive Model Tests for Assessing Maneuverability of a Damaged Surface Combatant with Initial Heel Angle”. 32nd Symposium on Naval Hydrodynamics, Hamburg, Germany 5-10 August 2018.

3. Requested computations

The requested info comes in 2 cases.

  • You can only submit case 5.1.2 when you delivered case 5.1.1
  • You can only deliver case 5.1.2 package 2 when you deliver case 5.1.2 package 1.
  • You can only deliver case 5.1.2 package 3 when you deliver case 5.1.2 package 2.
  • You can only deliver case 5.1.2 package 4 when you deliver case 5.1.2 package 3.

Forces and moments should be supplied as follows:

  • The N-moment (moment around the z-axis) should be supplied w.r.t. the midship.
  • The K-moment (moment around the z-axis) should be supplied w.r.t. the waterline.
  • Only the hydrodynamic forces are to be supplied: the inertial forces are not to be included.
  • Forces and moments are to be given non-dimensional:
Package Drift angle
β=-atan(v/u)
Non-dimensional rate of turn r’ Requested quantities
Case 5.1.1 15° 0 X’, Y’, K’, N’
12° 0 X’, Y’, K’, N’
0 X’, Y’, K’, N’
0 X’, Y’, K’, N’
0 X’, Y’, K’, N’
0 X’, Y’, K’, N’
-3° 0 X’, Y’, K’, N’
-6° 0 X’, Y’, K’, N’
-9° 0 X’, Y’, K’, N’
-12° 0 X’, Y’, K’, N’
-15° 0 X’, Y’, K’, N’
Case 5.1.2, package 1 0 X’, Y’, K’, N’
0.0762 X’, Y’, K’, N’
0.1712 X’, Y’, K’, N’
0.3106 X’, Y’, K’, N’
0.4834 X’, Y’, K’, N’
Case 5.1.2, package 2 0 X’, Y’, K’, N’
0.0782 X’, Y’, K’, N’
0.1755 X’, Y’, K’, N’
0.3108 X’, Y’, K’, N’
0.4849 X’, Y’, K’, N’
Case 5.1.2, package 3 12° 0 X’, Y’, K’, N’
12° 0.0760 X’, Y’, K’, N’
12° 0.1713 X’, Y’, K’, N’
12° 0.3017 X’, Y’, K’, N’
12° 0.4772 X’, Y’, K’, N’

4. Format

Link to an excel file, which a submitter can download.
The yellow fields in the excel sheet should be filled in. The excel sheet should be send to the organizing committee per email address “simman2019host@gmail.com”.

5. Example

For ONRT deep water, we elaborated an actual example of an actual submission compared to actual experimental data.
Table below gives an example of the data that we would be getting for the ONRT for case 5.1.1 and 5.1.2. Submitters should generate an excel sheet in the format of the Table below. The submitter must type the calculated X’, Y’, K’ and N’.

Table: Data from “submission 1”, (this is an actual case, where an empirical method is used to generate the forces and moments).

The organisers will compare the submitted results to experimental data. Comparing the above submission (above table) to experimental data will give the below figure. It is the intention to have many submissions in the same type of figure to learn about the prediction capabilities for which combinations of r’ and β.


Values of submission “prediction method xx” for ONRT in deep water for yaw and drift (case 5.1.2)

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