DGA Hydrodynamics (DGA Techniques Hydrodynamiques, or DGA-TH) is one of the oldest test centre of the DGA and, at the same time, the most modern one today. With around 200 employees (57% of them being engineers), it’s also one of the smallest.
History of DGA Hydrodynamics
Indeed, it was initially created back in 1906, long before the DGA was created. The project was driven by general engineer Emile Bertin, in order to test in live conditions the hulls of the ships under development. Such a facility was also seen as necessary to catch up with the British superiority in the field.
The first hydrodynamic test facility was then established in the South-West of Paris. At that time, it was the first one in the world to be equipped with concrete water tanks. In the following years, the facilities expended significantly. A wave basin was created in the 1930s, a rotating arm tank in 1939 and a cavitation tunnel in 1948, all in the area of what is now the headquarters of the French Armed Forces in Balard, Paris (the so called French Pentagon).
In the hydrodynamic field, the dimensions of the facilities do matter. Larger and longer tanks allow to reduce the simulation errors caused by the scale effect on water. In the 1980s, the Balard facilities were considered too small, and it was decided to transfer the DGA-TH in Val-de-Reuil, a small town located 100 km West of Paris. The decade-long transfer began in 1988.
In 2004, the 600 meters long towing tank was inaugurated. Today, the DGA-TH facilities are still evolving with the inclusion of more powerful simulation and computing capabilities and an increase use of digital technology.
For this reason, while DGA-TH was originally created in 1906, its new site in Normandy is seen nowadays as DGA’s most modern facility.
What are the missions of DGA Hydrodynamics ?
The main mission of the DGA Hydrodynamics in Val-de-Reuil is to provide hydrodynamic and hydro-acoustic expertise and testing for the benefit of the French Navy and French industry programs:
- DGA-TH provides advice and expertise during the development phase of the programs, helping the DGA, the Navy and the shipbuilder in developing realistic technical specifications for a new class of ship.
- During the design stage of a ship, DGA-TH makes sure the performances are compatible with the mission’s requirements. It is a phase of optimization of the design. Most of the time, three exchanges are required in order to optimize the design of a surface ship. A new submarine design requires much more feedback though.
- During the shipbuilding phase and after completion, DGA Hydrodynamics controls that the future and actual performances match the initial requirements.
The strategic goal of the DGA-TH is to help in the technical management of the French Navy programs. Its unique means and expertise help both the French Navy and French shipyards to prepare future developments and strategies.
But the DGA Hydrodynamics center is also a valuable tool of international cooperation. The DGA-TH facilities are indeed available for many export programs such as the Shortfin Barracuda for the Royal Australian Navy, or the different Scorpène SSK variants in past years.
The DGA-TH is also focused on European cooperation. France and the United Kingdom are in fact sharing their respective facilities (DGA Hydrodynamics in Val-de-Reuil and QinetiQ ocean basin in Haslar) for the conception of their sovereign naval programs.
The various aspects of hydrodynamics
Hydrodynamics is the study of fluids and of the forces applied on a solid moving body immersed in fluids. More specifically, hydrodynamics is the study of the interactions between a ship (or any seaborne vehicle) and the sea itself.
Different aspects of hydrodynamics are covered by the DGA-TH facilities and simulation technology:
- Resistance to forward movement: an important area of expertise in order to anticipate and afford maximum speed. Digital calculation is increasingly used for this purpose.
- Ship’s maneuverability: it assesses the control surface efficiency; evaluates the impact of different depths on the control surface and the diving and surfacing safety.
- Sea-keeping qualities: that’s the study the effect of swell and waves on the ship’s movements, its structural strength, its weapon system, its ability to recover aircraft, etc.
- Hydro-acoustics: it is the study of the radiated noise, the hydrodynamic noise and cavitation noise of ships and propellers, and help reducing them.
- Ship’s stability: this area of expertise studies the resistance of a ship against capsizing, combat damages, the impact of additional weights high up in the vessel, etc. Once again, digital simulation is now of great use for this task.
- Propulsion: DGA Hydrodynamics is in charge of all the French Navy combat ships and submarines propellers design. They are the only entity (public or private) in France with the expertise and test facilities allowing for efficient and quiet propellers design, in an iterative process with the contractors in charge of the propeller’s manufacturing.
- Towed devices, weapons and underwater objects: DGA-TH studies the attitude and behavior of various naval equipment. This aspect covers towed-arrays, sonobuoys, weapon separation (e.g. torpedo launch from a tube), submarine decoys, etc.
Hydrodynamics covers a wide range of expertise during the entire development of a new class of ship. For the FDI program, hydrodynamic tasks spread over a three years period, and are due to finish in the following days or weeks. They covered the design of the hull itself, the validation of the inverted bow, and even the design of the spray rail at the bow.
For submarine designs, the hydrodynamic work is far greater and virtually never stops during all the design, construction and trial phases of the program. Depending on the design, ten to fifteen years of hydrodynamic tasks are required for a submarine program. Between the French SSNs, the SSBNs and the export SSKs, the DGA-TH team is almost always involved in the support of at least one submarine program.
FDI, Scorpène, Barracuda, SNLE3G, PANG aircraft carrier: the many programs covered by DGA-TH
The high level of expertise of the DGA-TH is of great use for both military and civilian programs. In the past, Balard and Val-de-Reuil centres helped with the design of the Normandie and France ocean liners, but also several sailing yachts competing in the America’s Cup.
But with the recent burst of military activities, both in France and on the export market, DGA-TH is nowadays only focusing on defense programs.
After completing hydrodynamic expertise and testing for the Indian and Brazilian Scorpène programs and the French Suffren (Barracuda program), DGA-TH is nowadays focusing on several French and international designs:
- The FDI frigates, at least until the end of 2019.
- The SNLE3G, the next generation of SSBN for French Navy.
- The PANG (porte-avions nouvelle generation, or Next Generation Aircraft Carrier), the DGA-TH providing digital simulations in order to virtually test the different configurations under study.
- The Shortfin Barracuda design for the Royal Australian Navy Attack-class submarine. Even if it will be a derivative of the Suffren-class, the Attack-class will incorporate unique features that require proper testing and simulations.
For the moment, export programs cover around 15% of the DGA-TH activity, but the work on the Shortfin Barracuda is due to increase in coming years.
In the second part of this report (coming soon), we will give you a unique insight of the impressive equipment used by the DGA Techniques Hydrodynamiques
