Video

Theory behind Turning dynamics of ships

published on 6 May 2020 - 2304 -

Show comment section |

Found on YouTube. Created by

"ISSIMS GmbH - Marine Prediction Technology"

SAMMON Lecturing Video describing

"Theory behind turning dynamics of ships"

-------------------------------------------------------------
SAMMON - the IDEAL tool to identify manoeuvring capabilities of a ship - SAMMON - learning the EFFECTIVE way

Comment by Gunter Schütze via LinkedIn:
"Prof. Benedict a very interesting video by HS Wismar / Maritime Simulation Center Warnemünde ( MSCW) & Innovative Ship Simulation and Maritime Systems GmbH (ISSIMS). Excellent and understandable the dynamic effects of the forces and moments in turning circle explained. A really good illustration for students, nautical officer and Captains to lead them to the dynamic basics and to refresh the knowldege. I can only recommend this video. Thanks for sharing."

Germany, Wismar

ISSIMS GmbH
Innovative Ship Simulation And Maritime Systems

Education

Join the conversation...

Knud Benedict Germany

on 21 December 2020, 11:49 UTC

Thanks to Gunter for the recommendations and Michael for bringing in ideas and questions. To answer your questions, I like to explain the following:
1) The transverse force Y(ß) can be explained by two models:
a. Either it can be seen from its nature as a Lift force, i.e. the same force who lifts an airplane wing up in the air, works now horizontally on the ship hull due to the drift angle ß. It is generated by the uneven force distribution caused by an additional circular flow around the body (wing, or here the ship’s hull). This lift force has it maximum close to the wing nose – this means for the ship it is working more to the bow, so it turns the ship: I made an additional movie on that effect at out ISSIMS website on YouTube (“Effect of Drift Force and unstable moment”, https://youtu.be/agQPMQNwhxU.)

b. A second way is to look at the effect of the transverse speed along the ship length (This as named as “Slender body theory”). You are right that the transverse speed distribution is constant. However, the force due this inflow is not constant: because of the friction in the flow there is a boundary layer around the ship which is getting thicker to the stern and therefore the transverse forces are smaller at the stern than on the bow – this model also explains why the bow turns to increase the drift angle, which is called as unstable moment.
2) The "additional force at the stern" Y(r) is not just the aft component of the above evenly distributed drift force. The rotation /Rate of Turn creates a linear transverse speed distribution with maximum at bow / stern and minimum / zero at the ships center. This has an effect which can be explained by the wing/lift model under a) as curved centerline of the wind profile
3) You are right: A centripetal force is a force that makes a body follow a curved path. Its direction is always orthogonal to the motion of the body and towards the fixed point of the instantaneous center of curvature of the path - so in case of the ship motion on a circle these are the forces due to drift Y(ß) and turning Y(r). These forces are balanced by the centrifugal forces (which is Ycentrifugal in the movie). The ship is able to move in a steady state motion - This is also an equilibrium condition at constant speed and also constant rate of turn.
I do hope my explanations are of some help for professional as you are. And I should underline that these are attempts of us as humans to understand the nature – that’s why I mentioned two models (there are even more…). And they are not “Laws” - even the equations of Newton and Einstein are not Laws, but they represent our current views and approaches to describe the nature with our brain in order to think and plan ahead (– and have to be checked and approved continoulsy in daily life). In this way I made some comments in my movie about “digital twins” as key maritime innovations (https://youtu.be/jYRq6xRrVUw) you can have I look if you like.

[show more]

Mr Michael Nicholson Shipmove Ltd., United Kingdom

on 7 May 2020, 09:43 UTC

I either; don't fully understand, or disagree. 1) Why must the working force (transverse force) Y(B) be acting close to the bow. The rudder is providing a moment, I don't see why/how the ship also provides a turning moment. The drift angle of the ship to its bodily movement is uniform. Surely the forces would be distributed evenly?
2) Is the "additional force at the stern" Y(r) not just the the aft component of the above evenly distributed drift force.
3) The use of the term Equilibrium, is this correct? For an object to describe an arc or a circle requires an acceleration towards the centre, caused by centripetal force. This is not in equilibrium. Equilibrium would be a straight line at uniform speed.

Video Pivot Point Demo - HS Wismar

published on 10 July 2020

SAMMON Lecturing Video describing
"Pivot Point Demonstration"
-------------------------------------------------------------
SAMMON - the IDEAL tool to identify manoeuvring capabilities of a ship - SAMMON - learning the EFFECTIVE way

Video SAMMON Intro Ships Manoeuvring Predictions

published on 11 July 2020

SAMMON Introduction into Ships Manoeuvring Prediction
- newly made Video to display the principles of SAMMON

Video Knud Benedict Presentation on “Digital Twins” at IMLA SMU Seminar

published on 28 October 2020

This is the recording of the presentation with the title:
“Digital Twins" as Key Maritime Technology Innovations for MET - and for Operation of Intelligent Ships
It was held at the MET Training Course by Shanghai Maritime University on Oct 27 2020 on the occasion of IMLA 40th anniversary

Opinion A Corrected Version on Positioning of Pivot Point

by Capt. Santosha K. Nayak - published on 18 November 2020

Understanding the fundamentals of the pivot point is highly required for understanding the alteration of the courses. Pivot point is an imaginary point on the vessel which turns on a circular path on the perimeter of vessel’s turning circle when the vessel makes a turn. The knowledge about the position of the pivot point in a manoeuvring situation provides the ship handler with the information on the geometry of motion of the ship.

Video Berthing, Anchoring & other Mooring Operations | Berthing (Part 1)

published on 8 September 2021

Course Name: Berthing, Anchoring & other Mooring Operations
Topic Name: Berthing

Article Study: increasing competition in ports and the underlying pressure

published on 2 October 2021

A study of increasing competition in ports and the underlying pressure to improve port performance. This thesis is the final deliverable for the completion of the degree of Master of Science in Transport, Infrastructure and Logistics (TIL) at the faculty of Civil Engineering and Geo-sciences at the Delft University of Technology.

Video SAMMON Demo Planning FtLauderdale Arrival with comments

published on 20 January 2021

This updated video shows how easy it is to develop an arrival plan with the SAMMON Planning Tool. As a sample the arrival from appraoch until the berth to Ft. Lauderdale is used under strong current of 2kn. At the simulator training courses where we used this tool for preparation of a manoeuvring plan during the briefing sessions all nautical officers involved stated afterwards: "Why don't we have this tool on our ships?"

Article Pilots and VTS operators working together to improve maritime safety

published on 2 February 2022

The Norwegian Coastal Administration has signed an agreement with Aboa Mare to provide a new
course for pilots and VTS operators. By practising together in a simulator, maritime safety along the
Norwegian coast will be reinforced.

Video Boarding a Ship in Port Geraldton, Australia

published on 28 July 2021

Big thanks to Geraldton Port Authority for allowing Bill and I to go out in one of their pilot boats and board a ship. It was a beautiful day for it.

Article Med Marine Delivers Two Med-16 Pilot Boats To Nigeria

published on 5 May 2021

Med Marine and IBK Ltd. signed a two-vessel contract for MED-P16 series last November for Nigerian Ports Authority’s operations in Lagos, Nigeria. A year after that, Nigerian Ports Authority takes the delivery of the two high- quality pilot boats. Both units have been despatched on a specialised transport vessel to Nigeria from Turkey.