The sea supplies essential natural resources for human consumption worldwide, and especially in Israel. Associate Professor Nitai Drimer lives and breathes the sea since he was fourteen, and today he has become a faculty member in the Faculty of Mechanical Engineering in the hope of revitalizing the field of Naval Engineering, and to restore it as an area of study at the Faculty.
According to Nitai, the marine environment is used for transportation, food and energy production, sport and leisure activities, and constitutes a great potential as an alternative for residential and industrial land. Topics about Israel’s Naval and coastal engineering plans have been on the rise again lately that include: studies on constructing artificial islands as a solution to land scarcity in the country, offshore energy discoveries, the need to expand the sea ports due to the ever growing sizes of ships over the years, security needs that enhance the procurement and operations of the Navy, clearing protected waters from aquaculture farms and moving these establishments offshore to the open sea (Offshore Aquaculture), and expediting development of autonomous watercrafts leaded by Rafael Advanced Defense Systems Ltd.
Since the sea is not the natural environment for man, utilizing it to its hidden potential is founded on engineering technology, which advances steadily but securely. Naval Engineering is based on practical experience and every deviation from the proven scope of experience is done gradually (step-by-step) and backed up with proven engineering research and development. Even though development at sea is critical and essential to Israel, it is not counted among countries leading in this field. The Technion and its Faculty of Mechanical Engineering has the capability and equipment to change this current reality.
Design in Marine environments is the common denominator of design of structures and installations that need to function in a marine environment, such as: ports, offshore platforms for production of natural resources from the sea, watercrafts, floating structures, structures founded on the seabed, and offshore aquaculture facilities. Design in marine environments is based on familiarity and understanding of the sea environment and the ability to analyze of the interaction of the structure and the sea. Factors of the sea action on structures are hydrostatic pressure, waves and currents.
The hydrostatic is relatively simple to analyze, however is critical to the efficient functioning of the structure (buoyancy and stability). עיקר העניין והאתגר מקורו בגלים שעוצמתם אדירה והופעתם אקראית.The greatest challenge originates from waves, with its mighty strength and random appearances. To reach a reliable statistical evaluation of wave data for design, wave data is typically measured over a period of 20 years. At any case the design criteria will be probabilistic. In other words, any structure is designed to withstand an extreme storm that during the design life had a small probability of being exceeded. Most of the marine contractors are familiar with structures that collapsed while being mounted or during service, along with the popular expression “any structure at sea may encounter a sea that will fail it.”
The area at sea that is most difficult for design is along the surf zone (where waves are breaking), where it is unadvisable to construct anything. When a wave propagate from the open water towards shallow waters it becomes steep (high and short) until it loses its stability and breaks. If right before it breaks it collides with a structure, it creates a massive impact of water on the structure, causing pressures with of up to tens of tons per square meter. To illustrate this point, consider that the design load in civil engineering for a crowded hall is about half a ton per square meter, while for port quay, it is about 5 tons per square meter. As a result, creative ways of limiting wave impact are by porous or flexible structures.
Watercrafts can float on the sea surface (Surface Craft) or submerge under the sea surface. Slow marine crafts will maintain balance with the hydrostatic buoyancy force while High speed crafts are lifted by hydrodynamic forces. They can surf on the hull (planning craft), fly above the water supported by underwater foils (hydrofoil) or on an air cushion (hovercraft).
Offshore platforms can be seabed-based or to floating. The floating structure can be moored to grounded anchors or keep position by means of controlled thrusters. The decision as to which option to use is made according to water depth and specifications.
Associate Professor Drimer has worked on design and development of structures for sea farming since 1986, which over time are exposed to extreme sea conditions. For example – The “Ardag” aquafarming company, which was evacuated from the red sea for environmental reasons, had sea cages designed to withstand waves at the height of 4 meters. In its new location offshore the city of Ashdod, the design maximum wave height is about 14 meters. Ardag successfully implemented the innovative SUBflex system (an Israeli technology for submersible net cage systems used in offshore fish farming that has become known globally for its breakthrough in capabilities at high seas).
Together with his father, Moshe Drimer, Nitai designed the Underwater Observatory in Eilat. He is the naval architect of RAFAEL’s unmanned vessels PROTECTOR, and also designed the terminal for RORO (Roll-on/ Roll-off) ships at the Haifa Port. In his role as head of CAMERI – Coastal and Marine Engineering Research Institute at the Technion, he was responsible for laboratory testing of the hydraulic stability of the breakwater for HAYOVEL project at the Port of Ashdod.
Nitai has always been at sea. Ever since he was fourteen years old, he worked as a draftsman at his father’s office – who was a ship engineer – and later served in the Israeli Navy as deputy commander of submarines. He is an experienced surfer and sailor of yachts.
Associate Professor Nitai Drimer offers the Faculty of Mechanical Engineering his love of the sea and vast knowledge in the maritime field. It is hoped that this new appointment will lead to a revitalized future of Naval Engineering at the Technion.