The Specialist Committee on Powering Performance Prediction Final - PDF document

Proceedings of 25th ITTC – Volume II 397 The Specialist Committee on Powering Performance Prediction Final Report and Recommendations to the 25th ITTC 1. EXECUTIVE SUMMARY � Sverre Steen, (Norway) Chair, Norwegian University of Science and Technology The committee obtained and analyzed � Maria Bobo (Spain) Secretary, Canal de additional geosim model series data that Experiencias Hidroninámicas de El Pardo corroborates the Garcia-Gomez claim that � Gabor Karafiath, (USA) Naval Surface model size influences form factor. Warfare Center – Carderock Division � Mustafa Insel, (Turkey) Istanbul Technical A study of different friction formulations University showed that the form factor scale effect can be � Richard Anzböck, (Austria), Vienna significantly reduced by changing from Model Basin ITTC’57 to another friction formula. However, � Jinho Jang, (Korea) Samsung Heavy it was also found that a change of friction Industries. formula is not likely to improve the quality of � Naoji Toki, (Japan) Mitsubishi Heavy powering predictions significantly. Industries � Dexiang Zhu, (China) CSSRC, Shanghai A load-varying propulsion test only method Branch is not included in the updated powering � Wei Qiu, (Canada), Memorial University performance prediction procedure. of Newfoundland. The ITTC database of model and full scale At the first meeting Maria Bobo was trials data was found to have insufficient elected Secretary of the Committee. quality data to be used in a study of improving powering prediction methods 2.2 Meetings A method to predict the sea margin of ships is included in the procedure for predicting Meetings were held as follows: powering margins. � China Ship Scientific Research Centre, Shanghai Branch, November 2005. 2. INTRODUCTION � Istanbul Technical University, Turkey, October 2006. � Norwegian University of Science and 2.1 Membership Technology, Norway, September 2007 � Memorial University of Newfoundland, The 24th ITTC appointed the Specialist Canada, March 2008. Committee on Powering Performance Prediction with the following membership

Specialist Committee on Powering Performance Prediction 398 propulsion committee would take the lead in 3. TASKS SET FROM THE 24TH ITTC the update of this procedure. The committee was tasked with making the 1. Review and update the Speed/Power Speed/Power Prediction (7.5-02-03-01.4) and Prediction procedure (7.5-02-03-01.4), the Predicting Powering Margins (7.5-02-03- a. Make use of the dataset of over 120 01.5) procedures consistent with the Analysis ships, which has been collected, of Speed/Power Trial Data (7.5-04-01-01.2). We chose not to change the Analysis of b. Complete the outstanding set of Speed/Power Trial Data, and to make the two resistance, open water and load other mentioned procedures consistent. varying self propulsion tests initiated by the 24th ITTC The philosophy of the committee with respect to updating procedures has been that: 2. Make the Speed/Power Prediction (7.5- � A change should reflect a proper balance 02-03-01.4) and the Predicting Powering between current practice and state-of-the- Margins (7.5-02-03-01.5) procedures art. consistent with the Analysis of � A change should reflect physical aspects Speed/Power Trial Data (7.5-04-01-01.2). correctly. � A change should have a significant impact 3. Review and update the procedures for on the predicted power. predicting the resistance and propulsion of high speed marine vehicles, including The report discusses the update of each multihull vessels (7.5-02-05-01 / 02) to procedure sequentially, as they are listed in the assess power requirements, taking into tasks given to the committee. account drag reduction, hull appendage interactions, hull/propulsor interaction and hydrodynamic loads in waves. 5. POWERING PERFORMANCE PREDICTION 4. FOREWORD 5.1 Review of state of the art The committee was tasked with review and update of four procedures: The Specialist Committee on Powering Performance Prediction has been tasked with 1. 1978 ITTC Performance Prediction revising the ITTC recommended procedure for (7.5-02-03-01.4) predicting ship speed and power from model 2. Predicting Powering Margins tests – currently known as the ITTC 1978 (7.5-02-03-01.5 ) Powering Prediction Method, and the 3. procedures for testing and extrapolating Resistance tests of HSMV (7.5-02-05-01 ) resistance and propulsion of High Speed Marine Vehicles. The revision is based on a 4. Propulsion tests of HSMV balance between reflecting current practice and (7.5-02-05-02 ) the results of the most recent developments in the field of model testing and ship power The Propulsion Committee was also given prediction. To get an overview of current the task of updating the Propulsion test for practice a questionnaire has been distributed, HSMV procedure, and in discussions with the and the results are summarised in the next propulsion committee it was decided that the section.

Proceedings of 25th ITTC – Volume II 399 Questionnaire 13 of them use the formula in ITTC 78 method 13 included the roughness correction in To get an overview of current practice with the coefficient CA respect to powering performance prediction 13 use other corrections: Yazaki(1); both for conventional and high speed vessels, a ITTC mod.(1); Marin statistical method questionnaire with 27 questions was distributed (2); Empirical formula (3); Empirical to most ITTC-members. The questionnaire is Database(3); DRT correction(1); divided in one part for conventional ships and Townsin’s formula (1); 0.0004 (1) one part for High Speed Marine Vehicles. 7. 32 org. scale the wake of single-screw 42 replies have been received. These vessels: replies will not be made known outside the 21 use Tanaka Sasajima method (the committee. A short summary of the original ITTC 78 method) questionnaire results is presented here. Some 11 use other methods: Yazaki(3); organizations use more than one methodology Tanaka(1); ITTC mod.(1); Marin listed in the questionnaire, and some statistical method (2); Own Database (3); institutions didn’t reply to all questions, so the Vol. mean wake (1) number of replies doesn’t always add up to 42. 8. 20 org. scale the propeller open water characteristics: 17 use the method as given in the ITTC Conventional Ships 78 method 3 use other methods: ITTC modified.; 1. 41 of 42 organizations conduct model Influence of C V on C L ; Lerbs-Meyne resistance tests. 9. 20 org. usually scale the wake of twin- 2. 37 org. conduct model propulsion tests screw vessels and 3 only for twin-skeg: (the questionnaire does not consider 14 use Tanaka Sasajima method (the waterjets or surface piercing propellers) original ITTC 78 method), and 9 use other methods: Yazaki(1); 3. 31 org. use form factor to predict Tanaka(1); ITTC mod.(1); MARIN resistance from model test data: statistical method (2); Own Database (2); 25 use Prohaska’s method (or similar) Formula (1); w S = w M when w S > w M (1) 14 determine the form factor by towing at very low speed 10. 4 org. have a different practice for twin- 5 use an empirical formula to calculate k , screw ships regarding form factors: and They use a value of k = 0 1 uses its empirical database to find the 11. 22 org. make a special correction for scale value of k effect on appendages (like propeller shafts, 4. 20 org. use form factor in the formulation brackets and so forth). of the tow force for the model self 12 do this by testing with and without propulsion test and 19 do not. appendages and then scaling using a standard scaling factor (for instance 0.5) 5. 29 org. use the ITTC friction line as the 5 calculate the viscous appendage standard resistance in model and full scale using a 8 use Schoenherr’s friction line, local Re , and assumed form 2 use Prandtl-Schlichting’s factor of each appendage 1 uses Hughes (for full ships) 4 use other methods: k for each 1 uses Karman-Schoenherr’s append.(2); Taniguchi (1); R wBH = R wAH 6. 36 org. apply a roughness correction to (2) the full scale frictional resistance: