COVID-19 pandemic has recently had a dramatic impact on society. The understanding of the disease transmission is of high importance to limit its spread between humans. The spread of the virus in air strongly depends on the flow dynamics of the human airflows. It is, however, known that predicting the flow dynamics of the human airflows can be challenging due to different particles sizes and the turbulent aspect of the flow regime. It is thus recommended to present a deep analysis of different human airflows based on the existing experimental investigations. A validation of the existing numerical predictions of such flows would be of high interest to further develop the existing numerical model for different flow configurations. This paper presents a literature review of the experimental and numerical studies on human airflows, including sneezing, coughing and breathing. The dynamics of these airflows for different droplet sizes is discussed. The influence of other parameters, such as the viscosity and relative humidity, on the germs transmission is also presented. Finally, the efficacy of using a facemask in limiting the transmission of COVID-19 is investigated. IntroductionAt present, the world is suffering from the severe acute respiratory syndrome coronavirus disease (SARS-CoV-2) commonly known as COVID-19 which is an RNA virus that has a single strand and has similarity to SARS-CoV-1 in terms of evolutionary development and diversification [67,112]. This virus can cause lung inflammation, the main symptoms of COVID-19 patients are dry cough, fatigue, and fever [112]. In March 11th 2020, the WHO announced that COVID-19 became a pandemic. Healthcare infrastructure systems worldwide are overwhelmed due to the coronavirus pandemic because of its long incubation period and high contagiousness [32,52]. Current study shows that about 35% of infected persons do not exhibit overt symptoms [12] and this may unintentionally cause tremendous spread a e-mail:

Hydrodynamic cavitation is the formation, growth and subsequent collapse of vapor bubbles in a moving liquid. It is extremely important to determine conditions of cavitation inception and when it starts damaging industrial equipment. In some cases, such as hydrodynamic cleaning it is important to understand how to improve the cavitation phenomenon in order to enhance cleaning properties. The cavitation number is a parameter used to predict cavitation and its potential effects. In this paper we discuss limitations of this parameter and demonstrate that it cannot be considered sufficient to predict cavitation inception and development in the fluid flow. The experimental setup was designed and built to study cavitation inception in various nozzles. RANS SST k–ω turbulence model was used in this study to model turbulent flow in ANSYS Fluent. CFD calculations were compared to experimental results. It was shown that cavitation inception was sensitive to change in nozzle geometry and, since geometrical parameters are not included in cavitation number formula, scenarios of cavitation inception can be different at the same cavitation number.

The effect of a submerged cavitating jet on as-mined oil sands is investigated in order to assess the potential of this new technological approach to bitumen extraction at low temperatures. A series of laboratory experiments have been performed using a custom-made experimental apparatus that allowed ablation measurements of oil sands samples and provided information regarding the volume of the extracted bitumen, the remaining volume of cleaned sand, the effects of the water temperature, and the time of exposure of the sample to a cavitating jet. A comparison of the results for cavitating and noncavitating jets is provided.

Cavitating jets have been widely studied for over a century, but despite the extensive literature on this subject, the implementation of cavitating jets in many industries is still very limited due to technical challenges. The main purpose of the present paper is to provide recommendations on using the cavitating jets based on a comprehensive literature review on the erosion mechanism in these jets. Self-resonating jets are extensively discussed in the present paper due to their importance in amplifying the erosion effect of cavitating jets. The influence of different jet nozzle geometric parameters and the operating conditions of the cavitating jet flow on the erosion mechanism is also discussed. Finally, well drilling in addition to multiple other industrial applications of cavitating jets are examined.

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