Water intended for human consumption (i.e. drinking water) or for human-related activities (i.e. irrigation in agriculture) should preferably be free of various harmful pollutants, ranging from chemicals and organic compounds to microbiological hazards. Bacteria have traditionally been in the forefront of research among microbiological contaminants in water, while human and plant viruses were discriminated, due to the lack of appropriate concentration and diagnostic methods for viruses. In this project, we tackled this problem by combining two technologies in an innovative way: hydrodynamic cavitation and gaseous plasma. Cavitation provided a vapor bubble where we created a gaseous plasma rich in OH radicals, other reactive species, and UV radiation. These caused the oxidation of viruses on the bubbles’ surface, so that the destruction efficiency was by orders of magnitude higher compared to separate treatments by cavitation or plasma. The dissemination of the project results will raise public awareness and alert the responsible stakeholders to the waterborne microbe problematics and solutions offered by the project.

Production of mineral wool fibers is a complex process with a large potential for improvements due to the lack of open scientific research. To overcome the limitations of industrial mineral wool research, this postdoc project was initially based on construction of a laboratory spinning machine capable of producing fibers from the same raw materials and under similar conditions to industrial spinners. Using the laboratory machine, the fiberization process was investigated by high-speed imaging and by analysis of geometric and mechanical properties of fibers. Following the laboratory experiment results, we were invited by mineral wool companies in USA, China and Eastern Europe to consult them on improvements of their fiberization technology, which is an excellent opportunity for transfer of scientific knowledge in this research area into industrial practice.

The project will deal with the understanding of cavitation and its undesirable effects (especially cavitation erosion) in various liquids with integration of experimental and theoretical methods in the field of fluid mechanics. Emphasis will be placed on finding links between cavitation in pure water and cavitation in various liquids. Within the project we want to determine the importance of individual rheological properties of fluids, their interactions and influence on the process of erosion.

Cooling systems are one of the most important components in the power plant industry. The cooling system’s task is to ensure a designed negative pressure of condenser which maximizes work potential of the turbine as well as the power on the generator. Degradation of cooling systems, due to fouling, aging or air leakages, leads to deterioration of the negative pressure in condensers. We have designed a modular system for measurement of cooling tower performance, based on a set of stationary sensors and a set of sensors, mounted on mobile and autonomous measurement units.

We acquired a comprehensive insight into »discarded potential of biomass«, to research all aspects and benefits of cascading utilisation of this locally available, natural, and renewable resource, left unexploited to this day. Partners, allied through research-development-production form of circular economy, developed and optimised new, sustainable processes and technologies that helped us dig the way through to useful biomass components. Those proved beneficial in various production sectors – from chemical, textile, paper, wood processing and automotive industries, construction, energy, and engineering – integrated as environmentally acceptable materials and products, highly recyclable and re-usable. That way we built new value chains, allowed ourselves to step firmly onto green products market and strengthened competitiveness of Slovenian economy, improved social partnerships and, at the same time, burdened the environment significantly less.

As part of the IQ DOM program, we have developed technological solutions that are interconnected to form the “Intelligent home of the new generation based on smart devices and wood”. Such a home is built from human-friendly natural materials - especially wood, and at the same time represents a new paradigm in the field of adaptation to humans with non-invasive artificial intelligence. The characteristic of developed technologies or final building blocks is integration, adaptability and advanced, human-friendly intelligence. In the LVTS program group, we made a new generation smart home dryer.

Emerging environmental pollutants are substances that have often long been in the environment, but whose presence and significance are only now being elucidated. Wastewater treatment plants are the primary source of these micropollutants in natural waters. An increasing number of substances to be controlled in surface waters, including pharmaceuticals, are appearing on the priority list of the Water Framework Directive (WFD, 2000). A review of the literature reveals that conventional wastewater treatment plants that can successfully remove solid particles, organic matter, and nutrients from wastewater are not effective in removing these contaminants. In the proposed project we developed an efficient and practical way to monitor average concentrations of priority substances in natural waters in sub ng/L concentrations. Additionally, we explored alternative wastewater treatment technologies to prevent emerging contaminant residues from entering the environment. Due to possible toxic effects these compounds could have in the environment, we investigated cost-effective technologies including cavitation in combination with UV and TiO2 with which we reduced these compounds below the limit, which still causes side effects.

In the proposed project we performed experiments in cryogenic fluids where cavitation was initiated acoustically – by ultrasound. We characterized the development, the dynamics and the erosion of cavitation on an ultrasonic horn, which was operated at elevated pressures in different cryogenic fluids. Although the mechanism for generating fluid cavitation in this method differs from that occurring in flowing systems and hydraulic machines, its nature is believed to be basically similar. Specifically, we focused on investigating a state, which appears somehow intermediately between hydrodynamic and acoustic cavitation, namely a large cavity attached to an ultrasonic horn tip and collapsing with its self-generated subharmonic cycle frequency (the so called “acoustic supercavitation”) and which resembles the conditions in the turbopump inducer.

Briefly, cavitation is the occurrence of vapour cavities inside a liquid. Vapour structures are then entrained by the flow and violently collapse when entering regions of pressure recovery. The concentration of energy at collapse results in high stress levels, which can cause erosion. For a long time it was believed that cavitation should be avoided because of its negative character. Today cavitation is used in many processes (diagnostic and therapeutic medical applications, semiconductor processing and disinfection of water). Regardless whether cavitation is considered undesired or beneficial its erosion potential must always be considered. Cavitation and consequently cavitation erosion is one of the most ubiquitous problems at operation of turbines, pumps, ship propellers and valves. Despite large progress in cavitation erosion research in past years the phenomenon is still far from well understood. This project aimed at coordinating and integrating theoretical, numerical and experimental efforts to understand the processes involved in cavitation erosion from both fluid mechanics and material aspects.

The goal of biological wastewater treatment is complete mineralization, or conversion of organic compounds to carbon dioxide and water, which is not always the case. Some compounds are biorecalcitrant, so other abiotic treatment processes are crucial for their removal from the system, such as e.g. membrane filtration, UV degradation, advanced oxidation processes, and cavitation being a potential option. The aim of the project was to improve wastewater treatment using cavitation. The effects of cavitation were investigated on two levels: i) we used extreme pressures and temperatures from cavitation collapses to disintegrate smaller organic molecules, which are otherwise harder to disintegrate by conventional biological processes; and ii) by disintegrating larger particles we enlarged the specific surface and thus increased the rate of hydrolysis and biodegradation of organic pollutants. Cavitation was coupled with a conventional biological process and demonstrated a greater overall positive effect.

The measurement methods for quantifying kinematic conditions in hydrodynamic systems (turbine machines, pipes, spillways, settling tanks, etc.) currently available allow, in most cases, enable only limited monitoring of the velocity field. Limitations on the use of existing measurement methods are due to their complexity, inability to capture the entire velocity field at once, physical intrusion in the flow and / or high cost. The method developed in the project for the quantification of velocity fields in hydrodynamic systems is based on computer-aided visualization and the application of the physical laws of fluid dynamics and mass transfer. Together with the simultaneous qualitative and quantitative inventory of flow conditions (velocity and pressure field), this method can, through conservation laws as represented by e.g. Navier-Stokes equations, allows a thorough study of the mechanisms of individual phenomena or flow structures, which is a novelty not only in the field of free-surface flows, but in the field of overall fluid dynamics.

Optimal operation of turbopumps is crucial for all liquid fuel rocket engines. To reduce weight, these pumps often operate at critical conditions, where dynamic instability and cavitation are unavoidable. In cryogenic engines, the fuel and oxidizer used are liquid usually hydrogen and liquid oxygen at very low temperatures (about 14 and 90 K, respectively). The first project outcome was the experimental basis containing results of thermodynamic effect in cavitating flow and its influence on the cavity dynamics. The other application was the development of a numerical tool that enabled to take into account the cavitation erosion effects. We carried out direct measurements of thermodynamic effects in the developed cavitating flow.

CROPS was a large-scale integrating FP7 EU research project in the theme Nanotechnologies, Materials and new Production Technologies within the call Automation and robotics for sustainable crop and forestry management. The project developed a set of modular tools for robotic applications in permanent plantations. We led the work package on precision spraying, where for the first time a robotic sprayer detected a disease, positioned the nozzle and performed spraying of disease focci.

In today's rapidly changing and developing world we should at the society level look for the sustainable protection of the environment. Among this, a sufficient amount of clean energy is required. Hydropower is among the most important clean energy resources, but most of the water resources in the developed world are already exploited, with the notable exception of most rivers with low available head. Rivers with low head in Slovenia and Europe are still not exploited for energy production due to high costs of power plant erection. High efficiency of these power plants at a reduced need for submersion depth allows the use of alternative water sources, the same is true for power plants that operate on the principle of sea tide. The project developed methodology for the design of water turbines that will operate with a low head and low submersion depth. With modern experimental and numerical methods, we have shown that it is possible to improve the design of water turbines operating at low head and low submersion depths. For this, we performed numerical and experimental studies of cavitation.

Projects aims at the development of small plant protection sprayer for orchards and vineyards. Development included design and manufacture of ultrasonic sensor for detection of canopies. Sprayer was tested in orchards and has proved pesticides reduction over conventional designs.

Different problems from cavitation are encountered in practice. Effects are mostly related to vibration, noise, erosion, changes in flow hydrodynamics, increase of hydrodynamic drag, light and thermal effects. Especially the former are still relatively unknown, but are of great significance due to high temperatures that occur on the micro scale level. Cavitation was studied on more scale levels. Firstly, we considered acoustic cavitation, where we studied thermodynamic effects of single bubbles. Cavitation was generated with ultrasound in a small vessel. With aid of high-speed thermo camera analyses of local thermal effects in boundary layer that occur prior and post bubble collapse were studied. A transfer of knowledge from studies of single bubble effects to the cavitation cloud scale followed. Cavitation in form of clouds was generated hydro-dynamically in the vicinity of a submerged body in a cavitation tunnel. With measurements, which were performed within the scope of the project, we first determined and evaluated the thermodynamic effects, which led to better and more general simulation methods.

Attempts to reduce the sound-power level of an existing clothes dryer by investigating the aerodynamic noise sources were performed. The critical points were determined on the basis of spatial sound-intensity measurements and sound-pressure-level spectra measurements. The changes to produce the modified dryer, involved corrections to the secondary-flow fan's inlet region. A modified design of the heat exchanger was considered. The velocity and the acoustic properties of the heat exchangers were measured to help in the selection of the heat exchanger in accordance with the aeroacoustics theory that connects turbulent fluctuations and noise generation.

Cavitation in hydraulic machines cause surface erosion of the flow tract, noise, mechanical vibrations, and modification of flow field. The current state of the art of cavitation detection employs acoustic emission, pressure pulsation, mechanical vibration sensors, etc. Characteristically for all mentioned methods is an indirect observation of cavitation, which do not contain direct information about cavitation space structure and have relative low accuracy level. In contrast to mentioned methods, the aim of the proposed project was to develop a new, direct method of cavitation detection and monitoring on vital parts of the hydraulic machines with aid of a computer-aided visualization which on-line provided information about cavitation in hydraulic machines useful for inspection and monitoring. It enabled machines to operate in the regions with just allowed cavitation conditions.

Optimal cooling tower operation of thermo-energetic objects like steam power plants, heating plants, nuclear plants and thermo-energetic systems in process and petrochemical industry increases efficiency of plants in general. Reconstruction of cooling towers with the aid of new technologies leads to the high economical savings and many ecological advantages. Inside this project we used a new method of measurement of thermodynamical characteristics, that no longer demanded for the cooling tower to be stopped. Efficiency was expected to increase by 1.5 to 2 %, not depending on the output power of the plant. High savings in energy and money were expected due to high output power of the thermo-energetic systems.