Airflow Visualization Research Articles

Investigation on indoor airflow and contaminant dispersion of diffuse ceiling ventilation in heating and cooling modes

This paper systematically investigates the indoor airflow and contaminant dispersion of diffuse ceiling ventilation (DCV) for space heating and cooling. A numerical model of the office with DCV is built and validated. The indoor thermal comfort and air quality (IAQ) under different cases are analyzed. Simultaneously, different indices are employed to determine the influence of exhaust positions and air change rates on the system. The results indicate that DCV can provide a satisfying thermal environment both in heating and cooling modes, and there is no reverse flow from the room to the plenum. Besides, the visualizations of indoor airflow, temperature distributions, and mean age of air (MAA) show the different characteristics during heating and cooling. The ranges of contaminant removal effectiveness (CRE) and temperature effectiveness (TE) are 0.87–1.00 and 0.79–1.55 for heating, respectively. For cooling, they are 0.96–1.23 (CRE) and 0.92–1.06 (TE), respectively. Although the TE for heating is slightly higher than that of cooling, the CO2 concentrations and CRE manifest that DCV performs better for space cooling. Moreover, the results show that the exhaust positions influence TE more than CRE, especially for heating. Within the measured air change rates, it is found that the increase of air change per hour (ACH) can aid to the ventilation effectiveness of DCV. Meanwhile, the linear regression equations between ACHs and MAA are obtained. This research is helpful to reveal the flow mechanisms of DCV and guides the design and operation of the system.

Analisis Penggunaan Winglet Pada Pesawat Udara Cessna 150 Dengan Profil NACA 2412

The Cessna 150 is a light aircraft that is widely used in the world of general aviation. One important aspect in designing an aircraft, including the Cessna 150, is the wing design. When there is a meeting of air flows with different pressures from the top and bottom of the aircraft wing, it can cause a vortex to form at each wing tip. The impact of this vortex is that drag force increases, lift force and fuel efficiency decrease and turbulence can occur. One modification to aircraft wings to reduce the impact of these vortices is the use of winglets. This has been widely applied to the latest commercial aircraft to increase aircraft efficiency. The aim of this research is to analyze the use of winglets on a Cessna 150 aircraft with a NACA 2412 profile. This research uses Xflr5 numerical simulation with a 3D geometric configuration. The winglet shape used is cant angle with bend angles of 0°, 15, 30°, 60°, and 90° which were tested at angles of attack of 0°, 3°, 6°, 9°, 12°, 15°, and 18° with an air speed of 46 m/s. The research results show that the NACA 2412 airfoil with winglets is able to increase wing performance efficiency. This is proven by the visualization of air flow in modifications with winglets which can reduce vortices so that the air flow becomes smoother/laminer. In addition, numerical studies show an increase in the value of the lift coefficient (CL), a decrease in the value of the drag coefficient (CD), , and a better / ratio (CL/CD) with the use of winglets, where the winglet efficiency is best at a cant angle with a bend angle of 30°.

Application of Particle Image Velocimetry and Computational Fluid Dynamics Methods for Analysis of Natural Convection over a Horizontal Heating Source

The objective of this article is to address the challenges associated with visualizing air flow over a heating source in an open laboratory environment. The study uses a combination of experimental visualization and numerical simulation techniques to generate a 3D model of the air flow and heat transfer between the heating source and the environment via natural convection. The Particle Image Velocimetry method is used to experimentally visualize the air flow, which is known for its benefits of high speed and accuracy, and for its ability to avoid disturbing the flow of the fluid being investigated. The data obtained from this experimental method are used as input for numerical simulations using the Ansys Fluent program. The numerical simulations identify air vortices and other elements that disrupt the airflow in the laboratory environment. The resulting 3D model accurately represents the actual situation in the laboratory and could be further optimized by adjusting parameters such as the output of the heater and the heating source temperature. These parameters play a crucial role in ensuring thermal comfort in the laboratory environment, which is of utmost importance for user comfort. In conclusion, the study provides valuable insights into the visualization of air flow over a heating source and demonstrates the effectiveness of combining experimental and numerical simulation techniques to generate accurate 3D models of air flow and heat transfer.

Thermal Diagnosis of Ventilation and Cooling Systems in a Sports Hall—A Case Study

Air conditioning systems in buildings consume a significant part of the world’s energy, and yet there are cases wherein users are not satisfied with the quality of the thermal environment. Examples of such special cases are sports halls, which require different thermal conditions within a single zone. Thermal diagnostics for buildings can be used to diagnose problems. The aim of the paper was to analyse the effectiveness of the ventilation and cooling systems of a sports hall with a cubature of 16,300 m3 and to check the possibility of managing the hall’s cooling demands via the existing air conditioning system. Diagnostic measurements were performed, including in situ measurements of ventilation air flows from the diffusers and their temperatures, visualization of the supply air flows, and monthly registration of the indoor temperature in the hall at different set temperatures of the supply and exhaust air. Additionally, a numerical analysis, using EnergyPlus simulations, of cooling demand was performed with regard to the varying uses of the hall. The analysis based on measurement and simulation showed that it is not possible to remove heat gains from the hall with the current available ventilation air flow.

Optical measurement and visualization of transonic airflow in a compressor blade cascade

Optical measurement and visualization of transonic airflow in a compressor blade cascade

The Development and Implementation of Airflow Visualization Studies ("Smoke" Studies) as a Training Tool in Aseptic Hospital Compounding Facilities.

In the compounding facilities of hospital pharmacies, extemporaneous preparations for parenteral administration are produced using aseptic handling. The designated environment for this practice is a clean area, such as a laminar airflow (LAF) cabinet placed in a classified cleanroom complying with good manufacturing practices (GMP) and International Organization for Standardization (ISO) 14644-1 guidelines. The European GMP Annex 1 (Revision 2020) and United States Pharmacopeia (USP) <797> monograph state that airflow visualization studies (“smoke” studies) should be performed to substantiate the cleanroom and LAF cabinet performance and their qualification status. Even though smoke studies are required by these guidelines, current literature does not describe detailed practical protocols and acceptance criteria. The objective of this study was to develop and implement a practical smoke study protocol to ensure compliance with aseptic handling guidelines in hospital pharmacies. First, a literature search was performed to collect information about smoke study protocols and acceptance criteria. Subsequently, a smoke study protocol was developed for a downflow and crossflow LAF cabinet as well as for grade C/B cleanroom areas. As a proof of concept, the smoke study protocol for the downflow LAF cabinet was executed in the at-rest and in-operation states. Video recordings of the smoke studies were analyzed to assess the performance of the cabinet. Finally, the video recordings obtained from the smoke studies were used in a training program for hospital pharmacy operators, which showed that smoke studies might aid in operators’ aseptic handling awareness. To the best of our knowledge, the present study provides for the first time a practical approach for the development of smoke study protocols in a hospital pharmacy setting and shows potential for training operators, process optimization, and continuous quality improvement.

Characterization of nasal aerodynamics and air conditioning ability using CFD and its application to improve the empty nose syndrome (ENS) submucosal floor implant surgery – Part I methodology

BackgroundCFD simulation allows the visualization of airflow in nasal airways, but the predictions are rarely referenced in real surgeries. The limitations include having a reliable nasal geometry with reasonable boundary conditions and how the predictions corresponding to the symptoms. MethodsThe computational domain is developed from the computed tomography images and face profile of an empty nose syndrome patient with inferior turbinate reduction subtype before and after the submucosal floor implant surgery. The aerodynamics and the ability of conditioning the breathing air of the nasal cavities before and after the surgery are predicted using different breathing air conditions. Significant findingsThe surgery redistributes the airflow and improves the symptoms by having higher airflow fraction in sensor-rich inferior turbinate and shear stresses on superior turbinate olfactory region. The surgery enhances heat and water vapor fluxes from the mucus rich interior turbinate. After the surgery, the surface area on disease side with heat flux greater than the threshold 50 W/m2 increases at both anterior and turbinate, where receptors are rich to elevate the sense of the inhaled air. In summer and winter time, both the air temperature and relative humidity at choanae increases after the surgery by the enhanced nasal air conditioning ability.

Improving Nasal Airflow with a Novel Nasal Breathing Stent.

Nasal obstruction requires close attention, as it is a risk factor for obstructive sleep apnea (OSA). This study evaluated airflow rates of our newly designed nasal breathing stent (NBS) compared with those of existing nasal dilators in 10 adult men. We hypothesized that the NBS would expand the nasal passage more than the other nasal dilators by means of airflow measurements. We compared airflow measurements between the NBS and three existing appliances and no appliance. Velocity measurements were recorded by analyzing 499 videographic images when each appliance was placed next to a steam generator at 0, 5, and 10 mm from the outlet port for airflow visualization. The peak nasal inspiratory flow (PNIF) rate was measured using an inspiratory flow meter. The NBS resulted in significantly higher airflow velocity measurements at all distances from the outlet port and a higher PNIF rate than the other appliances. Thus, the NBS offers a significantly decreased resistance to air movement compared with other appliances. Future in-depth investigations are required to demonstrate the use of NBS as a nasal dilator in conjunction with continuous positive airway pressure/oral appliance treatments in patients with OSA.

Efficient Graphical Algorithm of Sensor Distribution and Air Volume Reconstruction for a Smart Mine Ventilation Network.

The accurate and reliable monitoring of ventilation parameters is key to intelligent ventilation systems. In order to realize the visualization of airflow, it is essential to solve the airflow reconstruction problem using few sensors. In this study, a new concept called independent cut set that depends on the structure of the underlying graph is presented to determine the minimum number and location of sensors. We evaluated its effectiveness in a coal mine owned by Jinmei Corporation Limited (Jinmei Co., Ltd., Shanghai, China). Our results indicated that fewer than 30% of tunnels needed to have wind speed sensors set up to reconstruct the well-posed airflow of all the tunnels (>200 in some mines). The results showed that the algorithm was feasible. The reconstructed air volume of the ventilation network using this algorithm was the same as the actual air volume. The algorithm provides theoretical support for flow reconstruction.

Palm-Sized Quadcopter for Three-Dimensional Chemical Plume Tracking

In this study, we designed and experimentally verified the placement of odor sensors and an algorithm using the aero-olfactory effect of a palm-sized quadcopter to solve the three-dimensional chemical plume tracking (3D-CPT) problem. Solving 3D-CPT is important in engineering as it helps perform rescue operations during disasters and identify sources of harmful substances. Moreover, the odor sensors must be properly located and a CPT algorithm be applied to improve the tracking performance of a chemical. However, studies regarding the use of quadcopters for solving the 3D-CPT problem are scarce, and the relationship between the odor sensor location and algorithm is debatable. Hence, we utilized particle image velocimetry, an airflow visualization technology, to evaluate the arrival direction of chemicals at different heights. The results showed that odor sensors must be placed on the upper and front surfaces of a quadcopter to monitor the chemicals three-dimensionally. Additionally, we designed a 3D surge-casting algorithm, which is an extension of the CPT strategy of a flying moth, that is, surge casting, to accommodate the proposed odor sensor placement. By conducting 3D-CPT experiments based on different heights of odor sources using the proposed system, we discovered that even in an environment with significant changes in the wind direction the CPT performance is better than that of the conventional 3D-CPT algorithm. Thus, 3D-CPT should be further improved to enable its application in unknown and cluttered environments. In this study, we improved the 3D-CPT performance of a palm-sized quadcopter by designing an appropriate sensor arrangement and algorithm balance.

Turbulence model assessment and heat transfer phenomena inside a rectangular channel under forced and mixed convection

A very high-temperature gas-cooled reactor (VHTR) is an attractive option for hydrogen production due to its high operating temperature. The reactor cavity cooling system (RCCS), a passive safety system of the VHTR, surrounds the reactor vessel with rectangular riser channels and removes decay heat from it. Under emergency operation conditions such as a decrease in the flow rate of the RCCS, the flow condition inside the RCCS riser can become a mixed convection condition accompanying heat transfer deterioration. To design and operate the VHTR with reliable safety, accurate predictions for various convective heat transfer conditions in RCCS riser channels are required. In this study, by comparing the results of an air flow visualization experiment, the predictability of the turbulence models was assessed for the convective heat transfer and complex flow characteristics near the corner region of the rectangular duct confirmed from the experimental study. In this paper, the heat removal rate through the test section of the visualization experiment was quantified under various convective heat transfer conditions, and local temperature measurement data from the experiment were presented to describe the heat transfer deterioration phenomena inside a rectangular riser in turbulent mixed convection. Linear and nonlinear eddy viscosity models were evaluated by comparing the heat transfer coefficient, local temperature, local flow structure including secondary flow, and turbulence quantities obtained from the experiment. Furthermore, improvements to turbulence models for enhancing the prediction of mixed convection heat transfer in rectangular riser ducts were proposed.

Experimental study of local effectiveness in the case of balanced mechanical ventilation in small offices

In this paper different mechanical ventilation methods were analysed in a test room, having similar dimensions with a small office room. A series of measurements were performed with mixing, displacement and personalized isothermal ventilation having one or two occupants in the room. The main goal of this research was to investigate the air cleaning performance of different ventilation strategies in the breathing zone. The CO2 emission of involved persons was determined and it was shown that one person released 13.4 l/h CO2 while two persons released 23.63 l/h CO2. Taking into account the spread of viruses and the requirements related to separation of persons in public buildings, measurements were carried out with “open” working desk and with “screened” desk as well. Using the balance equation of pollutants, the equation which describes the CO2 concentration variation in the closed space was developed and used for calculations. Air flow visualization was done for different ventilation modes. The local ventilation effectiveness was determined for each ventilation mode based on the measured and calculated CO2 concentrations depending on the provided fresh air flow, air distribution and occupants number. In the case of screened desk the personalized ventilation shows the highest local effectiveness (1.6–2.7 in comparison with 0.6–1.4 in the case of mixing and displacement ventilation).

Pumping ventilation of corner and single sided rooms with two openings

Corner rooms with two or more open windows in perpendicular facades can be naturally ventilated in cross-ventilation or pumping ventilation. These two airflow regimes also occur in rooms with two openings in the same façade, in the form of single sided pumping or cross sided ventilation. This paper presents an experimental and numerical simulation study of the scale and occurrence of these two flow regimes for rooms in a rectangular building exposed to wind. Flow visualization and tracer gas measurement of effective airflow were performed in an atmospheric boundary layer wind tunnel using a rectangular model of a three-story building (1/20 scale) with a ventilated middle floor. Experimental results show that pumping ventilation occurs when the wind is perpendicular to the façade (single sided rooms) or aligned with the building corner (corner rooms). In addition to these two perfectly aligned wind directions, pumping also occurs for a range of incoming wind angles: ±19° for single sided; and ±9° for corner rooms. As a result, for isolated rectangular buildings that have, at least, one single sided and two corner rooms in each facade, pumping ventilation can potentially occur in two or more rooms for 62 % of incoming wind directions. To investigate the transition between steady cross-ventilation and unsteady pumping ventilation, three-dimensional computational fluid dynamics large eddy simulations were performed to obtain wind generated pressures in the ventilation openings. Results show that the transition from cross-ventilation to pumping occurs when the steady pressure becomes smaller than the unsteady component. These results are used to develop a pressure based simplified model for corner ventilation that can predict effective airflow from external wind generated pressures with an average error below 10.2 %.

Airflow visualization and air purifier positioning optimization in potentially COVID-19 contaminated classrooms

Given the pandemic infection risk in classrooms and given the potential to purify COVID-19 prone air, this research team has visualized the flow of air to find the optimal position in a room. Through Schlieren imaging the air flow was studied to establish the circulation in the tested room. With a variation of air purifier positions in a model classroom, the imaging sensors have taken profiles of airflow and therefore contributed to identifying the optimal placings in heated classrooms. Given a random position of a potentially infected and COVID-19 infectious person, the systematic research measured concentrations of artificially produced particles that emulated aerosol distributions. The research established contaminations stabilizing after a quarter of an hour. The concentrations are only a fraction of the emitted effluents. In this way, the risk of superspreading can be mitigated and so the results allow continued academic work during the Corona pandemic

Airflow visualization and performance assessment for a roof ridge ventilator under wind using Schlieren photography technique

In Taiwan, natural ventilation devices are installed in many high-ceiling buildings, and such devices become a natural smoke vent system when a fire breaks out. The improved ridge ventilators can lead to hot air exclusion while avoiding the effect of wind. Four modes of wind were adopted to carry out the model experiments in this research. Considering that ventilators have complex and curved geometries, the Schlieren photography technique was used to effectively display the flow pattern of hot air. Thermocouples were installed to measure temperatures at each opening. The Schlieren images and temperature values indicate that the heat flowed upwards significantly when the wind was calm. When the traditional ridge ventilator was installed, the wind had an inhibitory effect on the exhaustion of hot air in an internal space. After the improved ridge ventilators were installed, the wind blew like moderate breeze, and the removal effect of hot air was improved. The experimental results indicated that heat accumulation was not obvious. However, the outside air would gush into a building when the intensity of the wind became a strong breeze. The results showed the performance of traditional and improved roof ridge ventilators in different wind fields.

Development of an onboard airflow visualization system for flow field measurement around a propeller of a multicopter UAV

Development of an onboard airflow visualization system for flow field measurement around a propeller of a multicopter UAV

Visualização da ventilação natural em ensaios na mesa d´'água comparado a simulações computacionais

No processo de projeto nota-se a existência de uma lacuna entre a teoria e a prática, principalmente com relação à ventilação natural. Isso requer o uso de métodos que auxilie a visualização do fluxo de ar nos edifícios e sua transferência para os projetos. Muitas das ferramentas confiáveis de predição da ventilação natural, como o túnel de vento e os softwares de Dinâmica dos Fluídos Computacional (Computational Fluid Dynamic – CFD), são complexas e caras, dificultando o seu uso durante o ensino e na prática dos projetistas. Diante disso, o objetivo dessa pesquisa é verificar se ferramentas simplificadas representam o escoamento do ar no projeto arquitetônico de maneira fiel. Para isso, a visualização da ventilação natural através de experimentações simplificadas é comparada com ferramentas complexas e de alta confiabilidade, como simulações CFD. O método foi dividido em 3 etapas. Primeiramente, foi construído um modelo físico modular, baseado na literatura especializada. Em seguida, ensaios na mesa d'água foram executados. Por fim, simulações computacionais em uma ferramenta simplificada (software Fluxovento) e em uma mais complexa baseada na Dinâmica dos Fluídos Computacional (software CFX) foram realizadas. Os resultados demonstram a compatibilidade entre as simulações CFD e os ensaios na mesa d´água, indicando que o ensino com essa ferramenta torna acessível o entendimento de conceitos básicos da ventilação natural. Já no Fluxovento, diferenças significativas foram registradas na análise do fluxo de ar, dificultando o entendimento da ventilação natural. Ressalta-se a característica modular do modelo para elaborar novos casos em estudo de ventilação natural.

Smoke-mediated visualization of airflow of the booth as a negative pressure machine for a patient lying a stretcher, to whom the medical staff can approach from the window on the side curtain. A medical staff’s action is simulating the practice of tracheal intubation or suctioning that frequently generate aerosols from the patient

Smoke-mediated visualization of airflow of the booth as a negative pressure machine for a patient lying a stretcher, to whom the medical staff can approach from the window on the side curtain. A medical staff’s action is simulating the practice of tracheal intubation or suctioning that frequently generate aerosols from the patient

Smoke-mediated visualization of airflow at the chest of a dummy from the FFU of positive pressure booth without a front curtain. The air flow came from the backside of the dummy sitting in the booth

Smoke-mediated visualization of airflow at the chest of a dummy from the FFU of positive pressure booth without a front curtain. The air flow came from the backside of the dummy sitting in the booth

Smoke-mediated visualization of airflow at the chest of a dummy sitting at a position with an angle of 45° to the air stream from the FFU in the positive pressure booth with a stair-cut front curtain. The airflow came from the backside of the dummy sitting in the booth without the turbulence

Smoke-mediated visualization of airflow at the chest of a dummy sitting at a position with an angle of 45° to the air stream from the FFU in the positive pressure booth with a stair-cut front curtain. The airflow came from the backside of the dummy sitting in the booth without the turbulence