Hanwha Ocean's deep dive into underwater stealth

A colossal acoustic water tank is aiding Korean shipbuilding company Hanwha Ocean in reducing submarine noise. The tank replicates vessel sounds and uses a Masker-Air System to mitigate vibrations.

The Acoustic Water Tank at Hanwha Ocean's R&D Institute in Siheung, Gyeonggi [SEO JI-EUN]

SIHEUNG, Gyeonggi — An eerie tranquillity pervades the colossal Acoustic Water Tank nestled within Hanwha Ocean's R&D Institute at Seoul National University's Siheung Campus, a unique research facility for the shipbuilding company in Korea.

At first glance, the tank could be mistaken for an expansive aquarium or a swimming pool, with dimensions spanning 25 meters in length, 15 meters in width, and reaching a depth of 10 meters. The underwater expanse, akin to the height of a three-story building, holds approximately 30,000 tons of water, equivalent to 10,000 household bathtubs, all while accommodating a ship-like structure.

The tranquil environment serves as an ideal environment for acoustic research. Its vital function is the study of reducing underwater noise emitted by submarines, which is crucial for their stealth and survivability. The tank's unique design elements including a double-wall structure and specialized inner wall materials contribute to the endeavor, helping to minimize sound reflections.

The Acoustic Water Tank at Hanwha Ocean's R&D Institute in Siheung, Gyeonggi [HANWHA OCEAN]

A tank to minimize noise

With the press of a button, the structure's internal speakers roar to life, replicating the sounds of the massive engines and motors of a vessel. Shortly after, a curtain of bubbles rises along the hull's surface, mitigating the vibrations from the ship's internal machinery — demonstrating the effectiveness of the Masker-Air System.

“Silent navigation is crucial for submarines and naval vessels as it is directly connected to the matter of life and death,” said Lee Won-byoung, a principal researcher of the Naval Ship R&D Team at Hanwha Ocean R&D Institute. “While I cannot disclose the exact reduction in hertz for our specific experiment, it's clear that introducing air bubbles effectively reduces noise.”

Adjacent to the tank sits an automated crane system. These automated cranes traverse in various directions, emitting sonar waves toward a designated target submerged within the tank. While the Masker-Air System focuses on noise reduction, this system seeks to pinpoint the location of a target using emitted frequencies.

“As the experiment is sensitive, typical working hours may introduce external noises,” Lee said, “but thanks to automated systems, scenarios can be preset, allowing data collection during quiet hours like late evenings or early mornings, thus enhancing research efficiency.”

At the Acoustic Water Tank, researchers replicate underwater conditions within a controlled space. The focus here is on developing cutting-edge technologies to minimize underwater radiated noise from submarines, enhancing their survivability by evading enemy detection.

Beyond its military applications, the facility aligns with environmental conservation efforts. International organizations like the International Maritime Organization (IMO) have expressed concern about artificial underwater noise and advocate for regulations to protect marine ecosystems, with ship operations being a notable concern.

“As the research aims to reduce noise spreading underwater, it can be utilized to prepare for international regulations, not only for special-purpose ships and military vessels but also for commercial ships,” said Lee.

The Cavitation Tank at Hanwha Ocean's R&D Institute in Siheung, Gyeonggi [HANWHA OCEAN]

The Siheung R&D Institute is also home to the world's largest Cavitation Tank. Within its 13-meter-long, 2.4-meter-high, and 2.8-meter-wide observation section, it tests crucial components like propellers under the rush of water that can reach speeds of up to 15 meters per second. Innovative technologies that employ air bubbles to dampen noise generated by propellers are developed here. The tank's competitive edge lies in the size of the observation section, making it the largest among commercial water tanks globally and offering state-of-the-art research capabilities.

The Towing Water Tank at Hanwha Ocean's R&D Institute in Siheung, Gyeonggi [HANWHA OCEAN]

The institute is also equipped with the Towing Water Tank, matching the world's largest with dimensions of 300 meters in length, 16 meters in width, and 7 meters in depth. The tank creates artificial waves for testing ship resistance, movement, steering, and other performance aspects. In May 2022, Hanwha Ocean utilized 3D printing technology with ABS material to produce a 10-meter Twin Skeg ship model, reducing the typical three-week model ship production time by up to 40 percent.

Hanwha Ocean's commitment to innovation extends to autonomous navigation, with a goal to develop Level 4 autonomous sailing vessels by 2030, utilizing advanced technologies.

Venturing into global defense market

Following its rebranding from Daewoo Shipbuilding & Marine Engineering to Hanwha Ocean in May, the shipbuilder unveiled its R&D facility to the press for the first time last Friday. With a recent decision to conduct a 2-trillion-won rights offering, the company is pouring 900 billion won in defense technologies. The company seeks to secure overseas defense production hubs and acquire global unmanned and advanced technology companies.

“When it comes to defense-related matters, we always talk about achieving a distinct advantage,” said Kang Joong-kyoo, director of the R&D Institute. “We no longer see a competitive landscape against domestic companies like 'H' [HD Hyundai]. We place great importance on overseas defense exports, which is why attracting foreign shipyards is part of our strategy.

“We will meticulously use the 2 trillion won to build an outstanding company, with its birthplace being the Siheung R&D Institute,” Kang added.

BY SEO JI-EUN [seo.jieun1@joongang.co.kr]