This paper presents two practical computational procedures to predict the steering and braking forces applied by tractor type escort tugs to large vessels, particularly oil tankers. The essential part of the escort performance prediction methodology is the computation of hydrodynamic forces generated by the tug’s hull and the appendages such as skeg. These forces can be converted into the steering and braking force components which define the escort performance of the tug. The hydrodynamic forces can be estimated by scaled model tests however this approach is not suitable for early design studies because of cost and time restrictions. The first methodology presented in this paper is based on semi-empirical methods, obtained from model test measurements and full-scale test results, and developed in order to be used at early design stages where limited design information is available. A computational technique based on Reynolds-Averaged-Navier-Stokes (RANS) equations is recommended for the later stages of design process in which more precise definition of hull and appendages geometries are available. This approach, which takes local flow characteristics into account, can be used for the optimisation of hull and appendages geometries. In this study, two different approaches are presented and used on a given escort tug

In the present study, the effects of n-butanol injection into intake air (n-butanol fumigation, nBF) on the performance and exhaust emissions were experimentally investigated in a Renault K9K 700 type turbocharged common-rail DI automotive diesel engine. Experiments were performed under five different loads such (140 Nm, 125 Nm, 110 Nm, 95 Nm and 80 Nm) and at 3000 rpm engine speed, for various n-butanol ratios. Here, n-butanol was injected into intake air by using an adapted carburetor, which main nozzle section is adjustable to give approximately 2 %, 4 %, 6 %, 8 % and 10 % (by vol.) n-butanol ratios. The test results showed that effective power values for selected nBF ratios are nearly equal to neat diesel fuel (NDF). However, break specific fuel consumption increases and effective efficiency decreases considerably for all of the operating conditions. NOx emissions decrease, whereas THC and CO increase significantly for all of the selected nBF ratios. Opacity increases for high loads (140 Nm, 125 Nm and 110 Nm) and increment ratios of opacity for high nBF ratios are higher than that of lower nBF ratios. Although opacity decreases under selected low loads (95 Nm and 80 Nm) for low nBF ratios, it starts to increase after 6 % nBF ratio. Also, total fuel cost for selected nBF ratios is higher than NDF. In the present study, the nBF results were also compared with the results of the n-butanol-diesel fuel blends (nBDFBs), which previously investigated experimentally by authors, for three different loads and three n-butanol percentages.

The International Maritime Organization (IMO) has set some criteria for the maneuverability of ships, in order to ensure safety at sea and keep collusions that may lead to pollution to minimum level. In this part of the two-part paper, maneuverability standarts for ships that IMO has specified and the standard maneuvering tests that have to be done to meet these criteria have been investigated. Some information has been provided about why the maneuvering tests are performed and how their results should be interpreted. It is also theoretically explained how to decide whether a ship has the turning ability and straight line stability. Lastly, the internal and external factors that influence the maneuvering performance estimation of ships were examined and some results given in the literature were interpreted briefly.

Since it is not possible to evaluate the maneuvering performance of a ship with a single criterion, each factor that affects the total maneuvering performance must be considered separately. This study, which examines the evaluation of maneuvering performance of ships, consists of two parts. In the first part of the study, some studies in the literature were classified and it was aimed to determine the subjects that were studied rarely. First of all, the studies about maneuvering performance were classified according to the ship type and the studies in the literature related to this subject were mentioned. After that, the linear and nonlinear equations of maneuvering motion were derived. Based on these equations, it was explained how mathematical models used in maneuvering performance analyses are derived and solved. Furthermore, the ways in which the maneuvering performance of ships can be determined and the methods of obtaining the maneuvering coefficients were explained. Finally, the results obtained in some studies were shown and interpreted.