Model Testing- Resistance & Propulsion

For a few minutes, take the privilege of seeing yourself as the owner of one of the world's biggest shipping companies. And adding to your imagination, lets say you have set an order for a ship the kind of which had never sailed before (it may be cruise ship, container ship, yacht, whatever you choose). The amount of money you would have planned for this project would be in the order of thousands of billions (may be more!). You hire a design company, get your design ready, find the world's most sophisticated shipyard to build your ship and launch it at the sea. Obviously you don't let your ship sail just like that! You carry out sea trials to analyse her performance, and Bam! Your ship's design speed was 24 knots and she could practically reach only 12 knots speed! Why do you think this happened? 

Correct! Your ship was of a new kind, and never before a prototype of your ship had been tested in a small scale for its performance evaluation. Before the A380 was designed and built, a lot of work had gone into model testing the aircraft for all possible conditions and circumstances that it would face up there. New ship designs are also model tested at towing tanks for evaluating their performance so that any ship owner wouldn't have to face what you just did a minute ago. 

This article is about how the model of a ship is tested for estimating its resistance and propulsion requirements, which finally gives the hull designer a platform to optimize the hull form for lesser resistance, choose the correct engine for the ship and  allows the propeller designer to design the perfect propeller for the ship.

Following presentation will give a clear theoretical explanation to procedure involved in carrying out model tests for Resistance calculation. Please wait till the prezi is loaded. It is recommended to view in fullscreen mode.

The following videos will give you a clear idea as to how Resistance Tests are carried out. The first video gives an insight about the even keel test carried out as a part of resistance calculation. 

The following video shows how trim test is carried out. The model is made to trim about the trim post and the readings of its motion and flow around it, which is finally evaluated.

                                 

The following video gives us a proper perception as to how models are run using a carriage to calculate the  resistance from the values obtained from the Dynamo meter.

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LSD

Article By: Tanumoy Sinha

Author's Note: The following article explained about the steps you should carry out if you were to test a model in a towing tank. The article is written keeping in mind the reader has got some basic idea about the concepts of resistance. The next part of this series of articles will focus on the different types and procedures carried out in the propulsion tests. I have written this article based on my experience and technical knowledge on the same as a Naval Architect. The picture and the video used above does not belong to LSD, and full credit for the same goes to their respective owners. If you have any queries or doubts, write to me at learnshipdesign@gmail.com