#insights

Reducing towing resistance is a major goal in marine engineering, as it improves energy efficiency and reduces operational cost and pollutant emissions on ships. Hydrodynamic analysis and fluid dynamics simulation (CFD) are tools applied in ship design and operation to minimise resistance and optimise performance, as well as other current and future applications in the naval field.

Hydrodynamic analysis

Hydrodynamic analysis consists of studying and understanding the water flows around the ship’s hull. Through measurements of pressures and velocities in towing tanks or through computational modelling, it is possible to identify areas of high resistance and develop solutions to minimise them. This involves optimising the hull shape, reducing surface roughness and improving load distribution to reduce hydrodynamic drag.

Computational Fluid Dynamics (CFD) simulation

Today, CFD is an essential tool for simulating and predicting the behaviour of fluids (water and air) around the ship’s hull. Through the spatial discretisation of the hull environment and the numerical solution of the Navier-Stokes equations, in steady or transient state, a detailed description of the fluid field in its vicinity and its interaction with the hull is obtained.

In particular, it provides the distribution of pressures and viscous stresses, which, once integrated on the hull, provide forces and moments in the vessel; it also allows to know in detail what the flow is like in order, for example, to obtain the uniformity of the flow in the propeller area. CFD simulation allows the evaluation of different design scenarios, which facilitates the optimisation of the hull and the determination of optimal configurations to minimise resistance.

Benefits and applications of hydrodynamic analysis and CFD simulation

The integration of hydrodynamic analysis and CFD simulation provides numerous benefits in reducing resistance on ships through efficient hull design, optimisation of hull form, optimisation of hull design and optimisation of hull shape. load distribution and viscous drag reduction have been routinely applied for a long time.

However, nowadays, the range of studies covered by these disciplines has broadened, such as the minimisation of hull-propeller interaction effects. These techniques are applicable both in the initial design stage and in the optimisation of ships in service, allowing continuous improvements in efficiency and performance.

Today, it is possible, using CFD, to carry out certain studies that are difficult to test in the towing tank. An example of this is the semi-automatic optimisation of hull form by deforming the surface and analysing the effect of this on a previously defined objective function (e.g. reduction of total resistance). It is also possible to estimate the impact of the flow caused by the ship’s forward motion on the propulsion or efficiency of the control systems. The possibility of transient simulations with various navigation scenarios (regular and irregular waves, shallow water, green water, interaction between ships, coupling with the cargo in liquid or grain transports, etc.) or the analysis of the ship’s response in various operating conditions (confined places, interaction between various ships, etc.) is an increasingly used reality.

In addition, and outside the purely hydrodynamic aspects, CFD is also used for various problems that may arise in some ship designs. For example, this technique allows the calculation of wind loads (both from the point of view of aerodynamic resistance and destabilising or even propulsive effects), passenger comfort (particularly important in cruise ships, in order to avoid uncomfortable areas on the decks), structure-aerodynamic interaction in helicopter landing platforms, fires, launching analysis, movement with ice, etc.

Towards a more sustainable future

Reducing resistance is a key objective in naval engineering to improve the efficiency and sustainability of ships. Hydrodynamic analysis and CFD simulation are fundamental and validated tools in this process, providing accurate and detailed information on fluid flows and allowing the optimisation of ship design and operation.

The implementation of these techniques in the shipbuilding industry enables significant advances in efficiency and performance, contributing to the preservation of the marine environment and the mitigation of climate change.