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 Bow Truster Effect on Ship's Headway

by Capt. Hugues Cauvier - published on 14 July 2022

When the bow thruster has been in operation for a while, pilots often notice that the ship not only turns but also gains speed. But why is this? Opinion by Capt. Hugues Cauvier.

Video CHIRP Pilot Ladders (Landscape)

published on 13 December 2023

We take a look at some of the dangerous ladder arrangements provided by ships when attempting to take maritime pilots on board. Our message is simple: if you are offered an unsafe or non-compliant ladder, do not board!

Opinion Fathom Safety: "A Guide to Pilot Ladder Securing"

by Frank Diegel - published on 7 October 2020

Fathom Safety was established as a not for profit organisation dedicated to improving maritime pilot transfer safety. Here is a guide to pilot ladder rigging. We hope you like it!

Video Introduction to Pilotage

published on 6 January 2021

Pilotage is being able to navigate safely into and out of a harbour/anchorage/port knowing where you are at all times, where your hazards are and a safe route in/out. This is particularly useful if you are heading into somewhere new or a challenging/busy area – or both!

Article GPS interference and jamming on the increase

published on 2 October 2020

Ships have reported an increasing number of cases of significant GPS interference and jamming in recent months. The geographic areas with more than one reported incident include the eastern and central Mediterranean Sea, the Persian Gulf, and multiple Chinese ports.

Video Pilot boarding at Manila, Philippines

published on 23 September 2022

Welcome to our channel Our Life at Wheels!! Pilot boarding procedure, Seafarers vlog, Marino vlog #seafarersarekeyworkers #marinoph #seafarer #marinoworldonline #seaman #seafarersandseamen #chiefmakoi #shorts

Video How Tugboats Keep Ports Running Smoothly

published on 13 January 2025

"The Hidden Heroes: How Tugboats Keep Ports Running Smoothly"Did you know that tugboats are the unsung heroes of our ports? They work tirelessly behind the scenes to ensure the safe and efficient movement of giant ships and cargo vessels. From navigating treacherous waters to providing emergency assistance, tugboats play a vital role in keeping our global supply chain running smoothly. In this video, we're shining the spotlight on these mighty machines and the brave men and women who...