Wednesday Sep 26, 2018

 

Developing of Dynamic Under Keel Clearance (DUKC) system

 

Fundamental importance of seaports in different aspects, especially in developing a nation’s economy, cannot be repudiated. Since seaports make a notable contribution to economic development of countries, senior managers devote scrupulous attention for seeking methods to promote efficiency in the overall transport chain. Of the significant parts of promoting efficiency in ports is boosting navigational safety which can be reachable by either hardware or software approach. Regular dredging of approach channels and human resource training or employing well-established computational methods for managing safe transport in ports can be considered as hardware and software methods, respectively.

The current project aims to use a software approach whose goal is to calculate under keel clearance by considering most environmental conditions. Therefore, not only the ship's safety is guaranteed when entering and exiting the harbor, but also it is possible to let vessels having greater draft move in shorter time intervals, promoting transport efficiency in ports. The port of Bushehr located in the Persian Gulf is considered to implement this engineering system.

A decision-making process for a ship arriving at or departing from a port should take place by considering three crucial factors. The first one is arrival or departure time of vessels. Since tidal effects making a major contribution to vessels’ transport can be regarded as a function of time, this factor is generally taken into account as the particularly significant one for each arriving and departing ship. The second factor is ship’s draught, directly depends upon loading conditions of a given vessel. The last one is the ship’s speed through the water. Although increase of the vessel’s speed leads to decrease of UKC due to the squat phenomenon, it is beneficial in the areas of the access channel covered by fluid mud layers, inhibiting the ship from grounding. It is noteworthy that since controlling vessels moving at slow speed is not feasible, vessels’ speed through the water should not be under a specified limit.

Four plausible scenarios can be constructed for organizing this maritime engineering system by considering three factors including time, ship draught and speed for a given vessel.

  1. Determining all aforementioned factors, the user investigates the possibility of a safe navigation.

  2. The system investigates the safe arrival (departure) time for the vessel, after the user specified the ship draught and speed.

  3. The system gives the safe ship draught for arrival (departure) in (from) the port, after the user specified the speed and time.

  4. The system gives the safe vessel’s speed for arrival (departure) in (from) the port, after the user specified time and ship draught.

The calculations based on which the final suggestion will be made for decision-making are performed with both the short time scale (less than 72-hour) and the long time scale (more than 72-hour). In the long time scale calculations, effects of bed forms, water level, tidal speed and squat will be taken into account. These terms are the most important ones for estimating under keel clearance, referring to the results of the previous research. In the short time scale, in addition to the aforementioned factors, the effects of wave, wind and wind set-up will be also considered.

Before the launch of the project, applying soft-computing methods was considered for calculating the aforementioned parameters. The reason behind this decision, except for their high computational speed, was on the assumption that we have comprehensive data available. However, after beginning of the project and gathering data, it was found that there were not extensive data available, especially for modeling wave characteristics. Further, if the models were set up carefully, computational time can be tremendously reduced. Hence, for obtaining the results, usual simulations were conducted.