## 1 Introduction  
In July 2021, a new design of our cleanup system called System 002, also known as \"Jenny\", was deployed in the GPGP for a testing campaign. It replaced System 001, which consisted of a 600 m-long passive floating barrier with a 3 m-deep skirt, designed to take advantage of natural oceanic forces, such as currents and winds, to passively capture plastic waste. As opposed to System 001, Jenny was designed to be a 800 m towed (i.e., active propulsion) floating structure composed of a containment boom and a permeable net-like skirt generally inspired by the fishing industry. As a matter of fact, the centuries of existence of fishing and aquaculture have set the ground for the development of most ocean applications involving net-like devices. In essence, the existing knowledge is directly extrapolated onto new technologies along with some additional fine-tuning. In this context, the netting, considered as a basic element of most fishing gears, has been subjected to numerous investigations. Specially, the studies on the hydrodynamic characteristics of the netting highlight the necessity of optimizing them for efficiency purposes. In the specific case of The Ocean Cleanup, the engineering efficiency and the environmental efficiency are the main drivers of the cleanup project, and they translate into two Key Performance Indicators (KPIs): the costs per kilogram of extracted plastic and the CO2 emission per kilogram of extracted plastic. Being a Non-profit organization that supports the preservation of marine ecosystems, The Ocean Cleanup is committed to making efficient use of the obtained donations, by setting a cost KPI target that aims to become financially self-sustaining and minimize the environmental impact of its operations, by setting an environmental KPI target that can lead to a net positive environmental impact. Therefore, understanding the hydrodynamic loads acting on its cleanup systems, which impact the fuel consumption of the towing vessels (implicitly their CO2 emission), becomes imperative. This is especially relevant since the testing phase with System 002 will be followed by a scale-up phase to a fleet of 2 km-long cleanup systems (System 03). It is expected that a larger system will not only increase fuel consumption (implicitly the CO2 emission), but also decrease the system's maneuverability such as changing heading and speed. Consequently, this decreases the capacity to sweep through previously identified plastic hot spots, meaning that the efficiency is potentially reduced. Therefore, the project KPIs, the system performance, and the whole offshore operation will have as a backbone the comprehension of the hydrodynamic behavior of the cleanup systems. Early investigations of the force acting on a plane net moving through water were inspired by fishing activities [1]. The general idea was to show that the resistance, which is the force required to tow the net, is proportional to the area of the plane net, to the square of the velocity of the net relative to the water, and to the angle between the direction of motion and the plane net. Amongst the early numerical models is the work of [PERSON] [2]. They explored the force acting on elongated fishing net twines and ropes under load. Their model took into account the stress-strain characteristics of the net material. Later, [PERSON] [3] carried out a study on the force acting on net cages, mooring cables, and plane nets. The context was about the optimization of the aforementioned force. In their work, [PERSON] and [PERSON] [4] characterized the flow properties in the vicinity of a screen. Chronologically, it is around the early 1990s that the number of this type of study started to increase. For instance, [PERSON] et al. [5; 6], [PERSON] [7] performed extensive studies on floating cage systems dedicated to fish farming. With computing resources becoming more and more accessible, numerical simulations of these structures arose in the literature.