This project is part of the NWO TTW grant recently awarded to a consortium led by Prof. Dr. D. Lohse (University of Twente), “Aqua – Water quality in maritime hydrodynamics”. This program aims to develop the knowledge and technology to significantly improve predictions of the effect of water quality on (a) ship resistance and (b) underwater radiated noise of cavitating ship propellers and pile driving for offshore wind turbines.

This program furthermore aims at achieving a breakthrough on the following three long-standing problems in the Maritime Industry:

1. A lacking understanding of the efficacy of transitional air layers and air bubble injection on friction drag reduction and lacking procedures for reliable model tests or computational simulations;
2. a lacking understanding of the effect of water quality on propeller cavitation inception;
3. An incomplete understanding of the effect of water quality on the radiated underwater noise by a cavitating propeller and by pile driving for wind turbines.

For each of these three issues, “Water quality” refers to the dissolved and free gas content (bubbles), the chemical, and the particulate content of water. The economical and societal impact is that air-lubrication promises net power reductions of up to 15% of the current standard. Another impact of the proposed research is that hull vibration levels can be predicted with higher accuracy, resulting in optimization of propeller efficiency, recently shown to reduce power requirements by 10-15%.

Within this larger program, the project titled “The effect of water quality on the acoustic footprint of ships” will aim at a better understanding of the effect of water quality on ship noise. Such an understanding would significantly improve spatial and temporal predictions of ship noise behavior on a global scale. The first objective of this project is to obtain a high-quality dataset in which all relevant parameters affecting ship noise propagation are measured at sea (Figure 15).

Second, the effect of individual and/or combined environmental parameter(s) on the occurrence and characteristics of micro-bubbles and cavitation will be investigated. Finally, this dataset will be used to direct future research in the laboratory and for the development of process-based models on cavitation and noise propagation.

We are looking for a highly motivated candidate with a PhD in acoustics or a related area with proven ability to publish research in international peer reviewed journals. You have experience in marine acoustic measurements and analysis, and experience with maritime technical research. Performing field-based measurements is an essential part of the project and due to the international character of the research team, it is crucial you are proficient in spoken and written English.

Your position will be hosted by the Department of Ocean Systems (OCS) at the Royal NIOZ on the isle of Texel.

Fixed-term contract: 3 years.

Employment of this position at Royal NIOZ is by NWO (The Netherlands Organization of Scientific Research). We offer a position for 3 (fulltime) years with an excellent salary, a pension scheme, a holiday allowance of 8% of the gross annual salary, a year-end bonus, and flexible work arrangements. You may expect attractive secondary employment conditions. We offer generous relocation expenses for employees coming from abroad and support with finding accommodation.

NIOZ has researchers in the Department Ocean System Research (OCS) study open-ocean processes from a variety of disciplines, ranging from physical and chemical oceanography, marine geology, paleoceanography to deep-sea ecology. We investigate the oceans in the past and present, to assess their future role. We make use of experiments and data collection during sea-going oceanographic research, as well as laboratory experiments and analyses in our home base on Texel. The department works around the globe, from the Antarctic to the Arctic, from the Caribbean to the North Sea. One of the areas we work in is the North Atlantic Ocean.

Researchers within OCS focus on marine inorganic carbon chemistry and the effects of ongoing climate change (e.g. ocean acidification) on seawater properties. Sound propagation is influenced by water chemistry, including seawater pH and concentration of particulate matter. Micro-scale bubbles furthermore determine the far- and nearfield propagation of sound. Cavitation by ships is one of the main sources of underwater noise and with a growing maritime transport sector, there is a pressing need to reduce this noise. Understanding the effect of bubbles, the influence of seawater chemistry and in particular the interaction between them, is necessary to develop strategies to reduce underwater noise.