## Background

As a ship moves in the water, it creates standing waves (bow waves) that oppose its movement.

The size of the wave has some negatives impact such as movement resistant, a potential risk to smaller boats, or it can damage shore facilities.

Therefore, a major goal of naval architecture is to reduce the size of the bow wave (reduce the ship resistance) and improve the ship’s fuel economy.

Ship resistance estimation is a complex task. It can be broken down into frictional and residual components[1]. There are three different methods to predict the resistance: empirical methods, model testing, and numerical simulation.

In the last years, numerical simulations using CFD have become a third alternative used in the industry. However, it is required to perform verification and validation procedures.

## Case Study

We compute the flow around a ship hull. As a reference case, we use the Wigley Hull, which has plenty of experimental data to compare with[2].

In this case, we measure the water surface level on the hull surface and its ship resistance (cT), and we compare the numerical results obtained with CFDSOF, against the experimental results available in the literature[2].

Note: the Froude number is equal to 0.267.

The principal factors affecting ship resistance are the friction and viscous effects of water acting on the hull, the energy required to create and maintain the ship’s characteristic bow and stern waves, and the resistance that air provides to ship motion.

The Froude number is an important parameter with respect to the ship’s drag, or resistance, especially in terms of wave-making resistance.

It is usually referenced with the notation Fn and is defined as:

## Simulation Architecture

We will perform free surface fluid simulation using VoF (Volume of Fluid) method.

## Results

Based on the Froude Number, the wave system is generated waves that reduce the wave-making. This is proven by the simulation. The front of the ship faces a high wave, while towards the back, the wave becomes smaller.

To validate the simulation, we compare the water level between simulation and experiment[2]. The results show similar trends between both methods.

The total resistance of the ship is compared between experimental results[2, 3, 4] and computational.

## Reference

[1] Bustos, Diana S. H., Alvarado, Ruben J. Paredes. 2017. Numerical hull resistance calculation of a catamaran using OpenFOAM. Ship Science & Technology. Vol. 11 (29-39).

[2] The Summary of the Cooperative Experiment on Wigley Parabolic Model in Japan. ADP003037, 1983.

[3]  Numerical Modeling of Resistance for a Conceptual Seatrain. CD-adapco Academic Paper Contest, 2011.

[4] Computation of Hydrodynamic Characteristics of Ships Using CFD. International Journal of Materials, Mechanics and Manufacturing, 2017.