Τhe efficiency of a Mewis propeller duct by the analysis of ship operational data is examined.The analysis employs data collected with high frequency for a three-year period for two siter vessels,one of them fitted w...Τhe efficiency of a Mewis propeller duct by the analysis of ship operational data is examined.The analysis employs data collected with high frequency for a three-year period for two siter vessels,one of them fitted with a Mewis type duct.Our approach to the problem of identifying improvements in the operational performance of the ship equipped with the duct is two-fold.Firstly,we proceed with the calculation of appropriate Key Performance Indicators to monitor vessels performance in time for different operational periods and loading conditions.An extensive pre-processing stage is necessary to prepare a dataset free from datapoints that could impair the analysis,such as outliers,as well as the appropriate preparations for a meaningful KPI calculation.The second approach concerns the development of multiple linear regression problem for the prediction of main engine fuel oil consumption based on operational and weather parameters,such as ship’s speed,mean draft,trim,rudder angle and the wind speed.The aim is to quantify reductions due to the Mewis duct for several scenarios.Key results of the studies reveal a contribution of the Mewis duct mainly in laden condition,for lower speed range and in the long-term period after dry-docking.展开更多
The importance of reducing ship resistance is growing considerably as a result of the increase in atmospheric emissions and the drive towards green shipping through decarbonization.Until this point,Energy Saving Devic...The importance of reducing ship resistance is growing considerably as a result of the increase in atmospheric emissions and the drive towards green shipping through decarbonization.Until this point,Energy Saving Devices(ESD),in particular,Hull Vane®(HV),have been widely applied as a potential technique for reducing wave-making resistance for vessels with higher Froude Number(Fr).The advantages of HV for a medium-speed vessel,where the wave-making component accounts for almost 50%of total resistance,have yet to be investigated.This study presents the computational analysis of the KCS model(1∶75.5);for a particular trim condition by using the VOF method and RANS solver.The hull acts as a candidate vessel for the class of medium-speed characteristics.A total of 36 numerical simulations were carried out to study the changes in resistance and motion characteristics of the vessel with and without HV.To validate the numerical setup,the experimental work of Hou et al(2020)on the DTMB hull was used.The effectiveness of HV can be comprehended by the reduction percentage in total resistance,trim,sinkage,and transom wave height,in comparison to bare hull condition.The reduction in total resistance extends up to 6%for Fr=0.32 with configuration 2 with negative AoF.The CFD results indicate that there is a reduction in trim up to 57%for the maximum speed with a corresponding Fr=0.34 with a positive angle of foil(AoF).The trim correction effect is increasing with the depth of submergence of HV.Concerning sinkage,there occurs nearly a 31%reduction for Fr=0.34 with a positive AoF.There exists a substantial reduction in the height of the transom wave with the inclusion of HV,the results of which are discussed in detail.From the presented results,retrofitting the Hull Vane®is effective in the selected speed range but pronouncing as the speed of the vessel increases.展开更多
文摘Τhe efficiency of a Mewis propeller duct by the analysis of ship operational data is examined.The analysis employs data collected with high frequency for a three-year period for two siter vessels,one of them fitted with a Mewis type duct.Our approach to the problem of identifying improvements in the operational performance of the ship equipped with the duct is two-fold.Firstly,we proceed with the calculation of appropriate Key Performance Indicators to monitor vessels performance in time for different operational periods and loading conditions.An extensive pre-processing stage is necessary to prepare a dataset free from datapoints that could impair the analysis,such as outliers,as well as the appropriate preparations for a meaningful KPI calculation.The second approach concerns the development of multiple linear regression problem for the prediction of main engine fuel oil consumption based on operational and weather parameters,such as ship’s speed,mean draft,trim,rudder angle and the wind speed.The aim is to quantify reductions due to the Mewis duct for several scenarios.Key results of the studies reveal a contribution of the Mewis duct mainly in laden condition,for lower speed range and in the long-term period after dry-docking.
文摘The importance of reducing ship resistance is growing considerably as a result of the increase in atmospheric emissions and the drive towards green shipping through decarbonization.Until this point,Energy Saving Devices(ESD),in particular,Hull Vane®(HV),have been widely applied as a potential technique for reducing wave-making resistance for vessels with higher Froude Number(Fr).The advantages of HV for a medium-speed vessel,where the wave-making component accounts for almost 50%of total resistance,have yet to be investigated.This study presents the computational analysis of the KCS model(1∶75.5);for a particular trim condition by using the VOF method and RANS solver.The hull acts as a candidate vessel for the class of medium-speed characteristics.A total of 36 numerical simulations were carried out to study the changes in resistance and motion characteristics of the vessel with and without HV.To validate the numerical setup,the experimental work of Hou et al(2020)on the DTMB hull was used.The effectiveness of HV can be comprehended by the reduction percentage in total resistance,trim,sinkage,and transom wave height,in comparison to bare hull condition.The reduction in total resistance extends up to 6%for Fr=0.32 with configuration 2 with negative AoF.The CFD results indicate that there is a reduction in trim up to 57%for the maximum speed with a corresponding Fr=0.34 with a positive angle of foil(AoF).The trim correction effect is increasing with the depth of submergence of HV.Concerning sinkage,there occurs nearly a 31%reduction for Fr=0.34 with a positive AoF.There exists a substantial reduction in the height of the transom wave with the inclusion of HV,the results of which are discussed in detail.From the presented results,retrofitting the Hull Vane®is effective in the selected speed range but pronouncing as the speed of the vessel increases.
