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7.5-02-03-02.1, Revi- Benchmark Data Are Collected and Described Sion 01 ITTC – Recommended 7.5-02 -03-02.1 Procedures and Guidelines Page 1 of 10 Testing and Extrapolation Methods Effective Date Revision Propulsion, Propulsor 2008 02 Open Water Test Table of Contents 3.3.6 Temperature ................................. 7 Open Water Tests........................................... 2 3.4 Calibrations ....................................... 7 1. PURPOSE OF PROCEDURE ............... 2 3.4.1 General remarks ........................... 7 2. PARAMETERS: ...................................... 2 3.4.2 Propeller dynamometer: ............... 7 3.4.3 Rate of revolutions ....................... 8 2.1 Data Reduction Equations ............... 2 3.4.4 Speed ............................................ 8 2.2 Definition of Variables ..................... 2 3.4.5 Thermometer ................................ 8 3. PROCEDURE .......................................... 3 3.5 Test Procedure and Data Acquisition ................................................... 8 3.1 Model and Installation ..................... 3 3.6 Data Reduction and Analysis........... 9 3.1.1 Model ........................................... 3 3.7 Documentation .................................. 9 3.1.2 Installation .................................... 3 3.2 Measurement Systems ...................... 5 4. VALIDATION ......................................... 9 3.3 Instrumentation ................................ 6 4.1 Uncertainty Analysis ........................ 9 3.3.1 General remarks ........................... 6 4.2 Benchmark Tests ............................ 10 3.3.2 Thrust ........................................... 6 3.3.3 Torque .......................................... 7 5. REFERENCES ...................................... 10 3.3.4 Rate of revolution......................... 7 3.3.5 Speed ............................................ 7 Updated by Approved Propulsion Committee of 25th ITTC: 25th ITTC 2008 Date February 2008 Date 09/2008 ITTC – Recommended 7.5-02 -03-02.1 Procedures and Guidelines Page 2 of 10 Testing and Extrapolation Methods Effective Date Revision Propulsion, Propulsor 2008 02 Open Water Test Open Water Tests 1. PURPOSE OF PROCEDURE T K = P TP ρ.nD24 The purpose of the procedure is to ensure Total thrust coefficient for a ducted propeller consistency of methodology and acquisition of unit correct results from Propeller Open Water K = K +K Tests. TT TP TD Propeller Efficiency in The propeller open water characteristics are JKT Open Water η0 = used in the analysis of the Propulsion Tests and 2Kπ Q the estimation of the required power. The pro- VA cedure addresses model scale only and does not Advance Coefficient J = nD consider extrapolation and full scale prediction. Reynolds Number of propeller based on chord length 0.7 R The procedure is generally applicable for 1 open water tests performed with conventional Vc 2 + ()7.0 πnD 2 2 Re = 7.0 ()AR propellers, ducted propellers and tip-plate pro- ν pellers. For podded propeller open water test procedure please refer to 7.5-02-03-01.3- Podded Procedure Propulsor Tests and Extra- 2.2 Definition of Variables polation c0.7R Chord length at 0.7R (m) D Propeller diameter (m) 2. PARAMETERS: n Rate of revolutions of the model pro- peller (rps) 2.1 Data Reduction Equations Q Propeller torque (Nm) T R Propeller radius (m) Thrust Coefficient K = T ρ.nD24 T Propeller thrust (N) Q TD Duct (or nozzle) thrust (N) Torque Coefficient K = Q ρ.nD25 TP Ducted propeller thrust (N) TT Total thrust of a ducted propeller Ducted Propeller unit (N) V Speed of advance of the model propel- T A Duct Thrust Coefficient K = D ler (m/s) TD ρ.nD24 ρ Mass density of water (kg/m3) Ducted Propeller Thrust Coefficient υ Kinematic viscosity (m2/s) ITTC – Recommended 7.5-02 -03-02.1 Procedures and Guidelines Page 3 of 10 Testing and Extrapolation Methods Effective Date Revision Propulsion, Propulsor 2008 02 Open Water Test 3. PROCEDURE The fairings forward and aft of a conven- tional pushing propeller should be modelled 3.1 Model and Installation according to Fig.1. 3.1.1 Model For a pulling propeller, the nose cone should be modelled accordingly. The model propeller should be manufac- tured in accordance with Standard Procedure 7.5-01-02-02, Propeller Model Accuracy. Figure 1 Geometry of Model Fairings cient length to ensure that the inflow over the 3.1.2 Installation propeller hub is parallel to the shaft should be mounted upstream of the propeller model, 3.1.2.1 Conventional Propellers Fig.1. In the case of a pulling propeller, the nose cone should be modelled according to the 3.1.2.1.1 Towing Tank actual propeller geometry. The connection be- tween the cap and the hub should be smooth The propeller model is to be mounted on a and without a gap. The size and shape of the drive shaft. A streamlined nose cap of suffi- nose cap should be recorded. In some cases the ITTC – Recommended 7.5-02 -03-02.1 Procedures and Guidelines Page 4 of 10 Testing and Extrapolation Methods Effective Date Revision Propulsion, Propulsor 2008 02 Open Water Test nose length may be less than 1.5 D as long as shaft should be arranged parallel to the calm the flow is parallel. water surface and the carriage rails. A typical set up for a towing tank is shown in Fig. 2. In order to eliminate a pressure build-up at the downstream end of the hub and the fixed The propeller immersion has to be selected shaft housing, the rotating part of the hub such that air drawing from the water surface is should be positioned in such a way to avoid avoided at any test condition. As a guideline, any kind of pressure build-up. The arrangement an immersion of the propeller shaft of at least used should be recorded and included in the 1.5 D is recommended, where D is the diameter test report. of the propeller. The immersion of the shaft centre line should be recorded and included in The drive shaft housing should not be too the test report. close to the model propeller blades. A distance of not less than 1.5 D to 2.0 D is recommended, where D is the propeller diameter. The drive Distance Immersion Cu rren t Meter Propeller Dynamometer Diameter Figure 2 Typical Set Up for Tests on Conventional Propellers in a Towing Tank Distance Load Cell Strut Immersion Cu rren t Meter Duct Diameter Propeller D ynam ometer Figure 3 Typical Set Up for Tests on Ducted Propellers in a Towing Tank ITTC – Recommended 7.5-02 -03-02.1 Procedures and Guidelines Page 5 of 10 Testing and Extrapolation Methods Effective Date Revision Propulsion, Propulsor 2008 02 Open Water Test 3.1.2.2 Ducted Propellers When a current meter is used to measure the speed of advance of the propeller model, The clearance between the propeller tips the immersion of the current meter should cor- and the inner surface of the duct should be kept respond to the immersion of the propeller shaft. at the recommended design value. Depending The distance between the propeller and the on model scale, this value sometimes cannot be current meter should be selected to ensure that achieved. Then, a maximum of 1.0 mm clear- the propeller model is not influenced by the ance for a scaled model propeller of about current meter. A distance between the current 250mm diameter is considered to be satisfac- meter and propeller model of at least 10 D is tory. The relative longitudinal position of the recommended, where D is the diameter of the propeller and the duct should be adjusted to the model propeller. design value. The dimensions of the tank should be large The duct is usually supported by a strut enough to avoid blockage and should be in- which has a streamlined section shape. Only cluded in the test report. the force acting on the duct should be measured during the test. A typical set up for a towing 3.1.2.1.2 Cavitation Tunnel tank is shown in Fig.3. The set-up for a cavita- tion tunnel is similar to that for a towing tank. The propeller model is to be mounted on a drive shaft. A streamlined nose cap of suffi- The duct thrust is usually measured by a cient length to ensure that the inflow over the load cell with a shielded strut, or a strain gauge propeller hub is parallel to the shaft should be positioned between the duct and the strut. An- mounted upstream of the propeller model, other method is to measure the drag force act- Fig.1. The connection between the cap and the ing on the strut separately as a function of ad- hub should be smooth and without a gap. The vance velocity. size and shape of the nose cap should be re- corded. In some cases the nose length may be 3.2 Measurement Systems less than 1.5 D as long as the flow is parallel to the shaft axis. The choice of propeller diameter Fig 4. shows the scheme of a typical meas- should be made such that scaling effects are uring system avoided within the blockage constraints of a given cavitation tunnel. The following quantities are measured: • Model speed The dimensions of the cavitation tunnel • Propeller thrust should be included in the test report. For test- • Propeller torque ing in the cavitation tunnel significant cavita- • Propeller rate of revolution tion should be avoided and open water tests • Duct thrust (if fitted) should be carried out under atmospheric condi- • Water temperature (for calculation of tion. viscosity) ITTC – Recommended 7.5-02 -03-02.1 Procedures and Guidelines Page 6 of 10 Testing and Extrapolation Methods Effective Date Revision Propulsion, Propulsor 2008 02 Open Water Test ENVIRONMENTAL CARRIAGE PROPELLER DUCT/POD CONDITIONS SPEED TEMPERATURE PROPELLER MEASUREMENT DYNAMOMETER MEASUREMENT DYNAMOMETER TACHOMETER/ THERMOMETER PROBE THRUST, DUCT /POD TANK WATER MODEL SPEED TORQUE, THRUST TEMPERATURE RATE OF REVOLUTION SIGNAL CONDITIONING and DATA ACQUISITION COMPUTER Figure 4 Typical Measurement System 3.3 Instrumentation 3.3.2 Thrust 3.3.1 General remarks The propeller thrust is measured using the propeller open water dynamometer.
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