Calm Water Resistance

Having accurate calm water resistance (Video) data early in the project can make a difference between a successful ship design project that is on time, and one that needs heavy revisions late in the project, or even worse, underperforms on sea trials.

Our CFD service offers a quick and reliable way to access accurate resistance data. It can be used to get a first evaluation of calm water resistance, as well as to make small modifications to the hull geometry and measure their impact to the overall hull design.

We often work with clients in an interactive way, where multiple iterations are needed to get to the final solution.

We typically get back to you within 3 working days with the new evaluation. This makes it easy for you to move forward with your project with good hydrodynamic performance in which you have confidence.

Wake fraction field from calm water resistance simulation
CFD simulation of ship resistance for a tanker

When to use calm water resistance CFD simulations ?

1. Ship hull design

There are multiple ways how having high quality CFD results can help you in the process of ship design.

First and foremost, at the outset of the project it offers an easy way to get accurate calm water resistance data so that you can reduce the number of interactions within the project with respect to the hull shape and main engine characteristics.

Second, being quick and relatively inexpensive, the calm water resistance service gives you room to improve your hull design while you can still make changes to the geometry of the hull itself.

This allows you to reduce the resistance, while maintaining the necessary hydrostatic characteristics of the vessel. For faster vessels, the running trim can also be optimised, and the influence of the position of the longitudinal center of gravity observed.

2. Appendage design

Appendages can often increase the resistance of the vessel more than expected, and it is a very good idea to quantify the increase. CFD technology allows us to see the individual resistance of each appendage by measuring the resistance force separately on each part of the vessel’s geometry.

This gives an insight into the resistance contribution of each appendage and the hull itself, and allows you to make changes to optimise resistance and/or performance of appendages.

These include rudders, struts, skegs, hydrofoils, thruster tunnels, interceptors, trim tabs, wedges, sea-chests, fin stabilizers and any other you can think of.

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3. Project revisions with ship resistance simulations

Sometimes things do not go as planned and it is necessary to make changes to the hull or appendages late in the project. CFD simulations of calm water resistance can reduce the towing tank fees in this stage, while giving more information about the possible changes that could solve the problem.

Whether it is a change in the bulbous bow, or shape of the stern, or perhaps a trim wedge, CFD can give a quick and accurate answer to the question “Will it help?”.

4. Simulations for retrofit projects

Retrofits of the hydrodynamic aspects of the vessel are typically done for one of the two reasons:

  1. The ship changed its function and a change is needed to satisfy the new function,
  2. The owner is looking for a way to reduce expenses, or increase profitability of the vessel on its existing operational profile.

In the first option, it is often required to check how the change of the hull or appendage geometry will affect  resistance. Conducting calm water resistance CFD simulations is a quick way to get accurate data on the impact of the changes.

In the second scenario, the return of investment of a retrofit directly depends on the cost of the retrofit, which includes the project phase. CFD can help reduce the project phase cost by reducing towing tank test expenses.

Pressure field distribution on a ship in steady resistance simulation
Streamlines from a ship resistance simulation

Maneuvering Simulations Using the Overset Grid Technology in foam-extend. 


CFD Validation and Grid Sensitivity Studies of Full Scale Ship Self Propulsion 


Fully Automated Ship Resistance Prediction using the Naval Hydro Pack


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