A Review of Laboratory and Numerical Techniques to Simulate Turbulent Flows

Abstract

Turbulence is still an unsolved issue with enormous implications in several fields, from the turbulent wakes on moving objects to the accumulation of heat in the built environment or the optimization of the performances of heat exchangers or mixers. This review deals with the techniques and trends in turbulent flow simulations, which can be achieved through both laboratory and numerical modeling. As a matter of fact, even if the term “experiment” is commonly employed for laboratory techniques and the term “simulation” for numerical techniques, both the laboratory and numerical techniques try to simulate the real-world turbulent flows performing experiments under controlled conditions. The main target of this paper is to provide an overview of laboratory and numerical techniques to investigate turbulent flows, useful for the research and technical community also involved in the energy field (often non-specialist of turbulent flow investigations), highlighting the advantages and disadvantages of the main techniques, as well as their main fields of application, and also to highlight the trends of the above mentioned methodologies via bibliometric analysis. In this way, the reader can select the proper technique for the specific case of interest and use the quoted bibliography as a more detailed guide. As a consequence of this target, a limitation of this review is that the deepening of the single techniques is not provided. Moreover, even though the experimental and numerical techniques presented in this review are virtually applicable to any type of turbulent flow, given their variety in the very broad field of energy research, the examples presented and discussed in this work will be limited to single-phase subsonic flows of Newtonian fluids. The main result from the bibliometric analysis shows that, as of 2021, a 3:1 ratio of numerical simulations over laboratory experiments emerges from the analysis, which clearly shows a projected dominant trend of the former technique in the field of turbulence. Nonetheless, the main result from the discussion of advantages and disadvantages of both the techniques confirms that each of them has peculiar strengths and weaknesses and that both approaches are still indispensable, with different but complementary purposes.

Numerical modeling of two‐phase flows in the presence of dynamic and thermal interactions

“…The proposed model was determined to produce reasonably accurate results. Ferrari et al 30 considered different methods and current trends in turbulent flow modeling achieved by both laboratory and numerical simulations. A specific feature of this review is that the reader is provided with the opportunity to choose the appropriate methodology for a particular case and to use the bibliography provided as a detailed guide.…”

Acoustic tomography for velocity estimation in high temperature flows

“…Typically gas temperature and velocity are measured using either "contact" or "non-contact" techniques. Contact techniques involve the use of thermocouples, resistance thermometers, and thermistors for temperature measurement [1], and Pitot tubes and hot wire or hot film anemometers for velocity measurement [2]. However, these techniques are intrusive and, if too many sensors are installed, they can significantly alter the fluid flow field.…”

“…As such, they have the drawbacks of being costly and challenging to implement. They also require the presence of an optical path, such as a transparent tubing or an optical access [2], which is rarely possible in an industrial context. The major challenge in determining these variables, is related to the aggressivity of the environment, due to the temperature and the chemical and physical composition of the working fluids.…”