Projects / Programmes
Scale effects in acoustic cavitation in various liquids with dimensionless number definition
| Code |
Science |
Field |
Subfield |
| 2.13.07 |
Engineering sciences and technologies |
Process engineering |
Water power |
| Code |
Science |
Field |
| T210 |
Technological sciences |
Mechanical engineering, hydraulics, vacuum technology, vibration and acoustic engineering |
| Code |
Science |
Field |
| 2.03 |
Engineering and Technology |
Mechanical engineering |
Cavitation, acoustic cavitation, sonotrode, cavitation scaling, various liquids
Researchers (1)
| no. |
Code |
Name and surname |
Research area |
Role |
Period |
No. of publicationsNo. of publications |
| 1. |
35069 |
PhD Martin Petkovšek |
Process engineering |
Head |
2017 - 2019 |
133 |
Organisations (1)
Abstract
Cavitation as a physical phenomenon describes the transition from a liquid to gas and back to a homogeneous liquid at an approximately constant temperature, wherein the phenomenon requires a local pressure drop in the liquid. In the described phenomenon small vapor bubbles, so-called cavitation bubbles are formed, which from crossing from the low pressure area to the area with higher pressure, violently collapse back in a homogeneous liquid.
Cavitation can occurs at all turbomachinery, which has for a working medium a liquid. Cavitation phenomenon is almost inevitable in the fuel injection system, and can also occurs in valves, bearings, etc. In most cases, engineers want to avoid or to prevent the presence of cavitation, because it has a number of negative effects, such as vibration, noise, machine efficiency drop and which is most undesired the cavitation erosion, which can damage a machine or a device so severe that it disables its normal operation.
Initially, cavitation was treated exclusively as undesirable phenomenon, which should be avoided, but nowadays the phenomenon can be also used as a tool in many industrial processes and medical procedures.
Most of the studies in the field of cavitation is made in pure water, where cavitation is relatively well known and relatively well we can be predicted with various numerical methods. Much less research work has been conducted in the field of cavitation in liquids other than water and the fact that in many processes in which we are not dealing with a pure water cavitation occurs, it would be worth exploring the phenomenon in these other liquids such as a variety of solutions, suspensions, colloids , oils, fuels, cryogenics, etc.
In the context of the proposed postdoctoral project we intend to experimentally investigate cavitation in various liquids by means of acoustic cavitation caused by the sonotrode. We will make a comparison between the cavitation in the pure water and various other liquids, such as seawater, fuels and liquid nitrogen. Experimental data are of great importance, as they are needed to develop new and improve existing numerical models, which are still largely based on experimental data from cavitation in water.
Postdoctoral project will be divided into four work packages (WP):
- WP1: Design and construction of the test rig.
The design of the test rig will base on the ultrasonic probe – sonotrode, which tip is immersed into the working liquid. Cavitation tank with a capacity less than 1 liter, in which working liquid will be poured, will allow to change and control the operating conditions.
- WP2: Characterization of cavitation in water.
After the test rig construction (within WP1), we will experimentally evaluate cavitation in water at various operating conditions. Characterization of cavitation in distilled water will serve as a reference for the comparison with other liquids (WP3).
- WP3: Scaling cavitation in various liquids.
Experimental evaluation of cavitation in various liquids at different operating conditions will give us an insight on the possibility of scaling cavitation from a reference liquid to any kind of liquid by knowing its basic rheological properties.
- WP4: Analysis of the results and definition of the dimensionless parameter for acoustic cavitation description.
Based on the results from WP2 and WP3, we will determinate dimensionless parameter, which will aim to describe the state of cavitation, similar to Cavitation number by the hydrodynamic cavitation.
With precise evaluation of cavitation properties in various liquids we will be able to establish a framework for improved methods for predicting cavitation in various liquids. This will lead to more effective machinery and their longer lifetime, as well as to the optimization of processes where cavitation can be used as a tool.
Significance for science
Cavitation as a physical phenomenon is relatively well researched, but still not entirely explained and the current science does not have all the answers of what exactly is happening on the scale of the cavitation bubble, what the impact on its growth and development and how the collapse of the bubble cause damage to the surface of the material. Many questions arise on the scope of cavitation in a number of processes, the mechanisms have an impact on example mixing, cleaning, homogenizing, killing microorganisms, etc. And since we are usually dealing primarily with liquids other than water in real processes, it raises many more questions how the properties of the liquid affect the process of cavitation.
The answers to this problems may be offered only by research-based studies with implementation of vast numbers of experiments. Only on the basis of experimental work will be both the profession and science can progress and develop.
It is clear that the scope of cavitation becomes increasingly interesting because of its use as a tool in many processes, especially for the treatment of various types of water and thus when the understanding of the phenomenon itself, and its mechanisms for cleaning, mixing, homogenization, etc. advanced, many processes can be improved and new opportunities can develop for the use of cavitation in the industry.
Within postdoctoral project we want to develop a mix of experimental, numerical and theoretical approaches to get a better understanding of the processes described in the project.
Significance for the country
Cavitation, hence its undesirable effects, especially cavitation erosion is one of the most pressing problems, which threatens the operation of the turbines, pumps, ship propellers, valves, fuel injection systems and others. Erosion can cause huge costs for treating runners at hydropower plants, ship propellers and others or shorten the lifetime of machines and devices.
With a better physical background understanding of the cavitation, the undesirable effects can be better predicted or even prevented in order to reduce the costs of repairs of machinery and devices that suffer from cavitation. At the same time new opportunities can open for the use of cavitation in the positive purposes in industry and medicine. Cavitation is already effectively employed in a variety of processes and with better knowledge and control of its positive and negative effects, one will be able to make processes more efficient, which will lead to reduction of operating costs.
Intensive research conducted how to utilize the positive effects of cavitation in the field of environmental protection, wastewater treatment, for cleaning ballast water treatment biofuels etc. With knowledge of the properties of cavitation in such complex liquids like eg. waste or sea water, will be able to process more effective and will therefore have a greater impact on the environment, and thereby also on the long-term health and happiness of society.
Most important scientific results
Interim report,
final report
Most important socioeconomically and culturally relevant results
Final report
