Airflow Vortex Research Articles

Turbulence characterization of instantaneous airflow in an aisle of an aircraft cabin mockup

The turbulence characteristics of instantaneous airflows in an aircraft cabin mockup are measured by high-frequency mini particle image velocimetry (mini-PIV) and analyzed by higher-order turbulent statistics. Under maxing ventilation in the aircraft cabin, two jets from the diffusers collide each other in the middle of the aisle. The airflows of collision regions in an aircraft cabin are typically turbulent, with a low velocity magnitude and a high fluctuation. Although the average airflow fields are uniform and have a smaller velocity gradient, the instantaneous airflow fields are remarkably unstable. Turbulence scales are utilized to analyze the spatial and temporal characteristics of the instantaneous airflows. The maximum airflow vortex scale of the collision zone is 11 cm, and the minimum vortex scale is only 8 × 10−4 m. The inertial sub region of the airflow power spectrum in the collision region is approximately 4–10 Hz. The wavelet coefficients of instantaneous fluctuation velocity have a quasi-periodicity of approximately 0.5 s, when the scale factor is 54. The grid size of direct numerical simulation (DNS) is recommended to be less than 0.3 mm, that of the large eddy simulation (LES) should be between 0.3 and 100 mm and that of the Reynolds-average Navier-Stokes (RANS) should be larger than 100 mm and smaller than the characteristic scale of airflows. The LES unsteady simulation time step should be less than 0.1 s, and the time step of RANS method should be less than 0.25 s. The power spectrum exponent of the instantaneous airflows in the aircraft cabin mockup is between 1.2 and 1.8, similar to natural wind, and will thus have a beneficial impact on human comfort.

Numerical investigation of airborne contaminant transport under different vortex structures in the aircraft cabin

Airborne contaminants such as pathogens, odors and CO2 released from an individual passenger could spread via air flow in an aircraft cabin and make other passengers unhealthy and uncomfortable. In this study, we introduced the airflow vortex structure to analyze how airflow patterns affected contaminant transport in an aircraft cabin. Experimental data regarding airflow patterns were used to validate a computational fluid dynamics (CFD) model. Using the validated CFD model, we investigated the effects of the airflow vortex structure on contaminant transmission based on quantitative analysis. It was found that the contaminant source located in a vorticity-dominated region was more likely to be “locked” in the vortex, resulting in higher 62% higher average concentration and 14% longer residual time than that when the source was on a deformation dominated location. The contaminant concentrations also differed between the front and rear parts of the cabin because of different airflow structures. Contaminant released close to the heated manikin face was likely to be transported backward according to its distribution mean position. Based on these results, the air flow patterns inside aircraft cabins can potentially be improved to better control the spread of airborne contaminant.

Numerical Simulation Study on Airflow Structural Characteristics and Vortex Evolution in Human Mouth-Throat Model

Large eddy simulation was used to simulate the airflow movement and vortex evolution in human mouth-throat model in the conditions of the low intensive respiratory patterns, and the airflow structural characteristic and vortex evolution in mouth-throat model was discussed. The results show that two velocity growth points generated in pharyngeal and laryngeal region; the airflow separates in region near the pharynx and the separation zone appears near the anterior wall of pharynx; A turbulence jet appears in the glottal region and the airflow; the jets formatting in pharynx and laryngeal lead to two vorticity growth regions; flat vortex appeared in the throat; a curved vortex like the trachea wall appeared in the anterior wall of trachea, and nearly symmetric reverse vortex pairs appeared in the trachea.

A Case Study on the Air Flow Characteristics of the Hirobo-FALCON 505 Controllable Helicopter's Main Rotor Blade

The aerodynamics of the helicopter rotor is one of the most elating and exigent tribulations faced by the aerodynamicists today. Study through flow visualization process plays a key role in understanding the airflow distinctiveness and vortex interaction of the helicopter main rotor blade. Inspecting and scrutinizing the effects of wake vortices during operation is a great challenge and imperative in designing effective rotor system. This study aimed to visualize the main rotor airflow pattern of the Hirobo-FALCON 505 controllable subscale helicopter and seek for the vortex flow at the blade tip. The experimental qualitative data is correlated with quantitative data to perform scrupulous study on the airflow behavior and characteristics along with its distinctiveness spawned by the main rotor blade. Simulation using design software is performed in analogous stipulations to endow with comparability between the flow visualization results. Throughout the blade span several dissimilar flow patterns have been identified. The main rotor hub has turbulent flow at its center due to low energy of air amassed in this region whereas in the middle portion of the rotor blade, the air encompasses high kinetic energy with a clear straight streamline pattern.

Energy Harvesting from Von Karman Vortices in Airflow for Autonomous Sensors

In this paper an innovative energy harvesting system based on a piezoelectric converter to extract energy from airflow and use it to power autonomous sensors is presented. The converter is embedded as a part of a flexure beam that is put into vibrations by Von Karman vortices detached from a bluff body placed upstream. The results of experimental characterization show that higher conversion effectiveness is obtained for flow velocities where the frequency of the vortices matches the resonant frequency corresponding to the first flexural mode of the beam. The possibility to power autonomous sensors has been shown by developing an energy management and signal conditioning electronic circuit plus two sensors for the transmission of a RF signal from which temperature and flow velocity can be extracted. A harvested power of about 100μW with retransmission intervals below 2min have been obtained.

A computer mouse based on highly sensitive micromachined flow sensors

A PC mouse based on micromachined calorimetric flow sensors is presented. Two cylindrical openings in the bottom of the device are equipped with highly sensitive flow sensors (for the x- and y-velocity components). Due to fluid adherence to the boundary (mouse pad), the device motion induces an air-flow vortex in the cavities. A microcontroller processes the sensor signals and sends the velocity information via USB interface to the PC. In order to obtain the optimum cavity dimensions, comprehensive 2D and 3D models of the device were developed. A mouse prototype was build as a plug-and-play device and characterized utilizing a specially developed measurement setup. The measured characteristics are in good agreement with the simulated behavior. The device features very low power consumption and functions independently of the reflectivity and surface roughness of the mouse pad.

Vortex fuel nozzle to reduce noise levels and improve mixing

A fuel nozzle with a ring of fuel spray orifices directing fuel jets at a fuel vortex generator having a fuel deflecting surface disposed downstream a distance from each fuel spray orifice. A mixing chamber is defined between the fuel spray orifices and the fuel deflecting surface having a surface contour oriented to deflect fuel jets into the mixing chamber in counter-rotating adjacent pairs of fuel laden vortices. An air inlet supplies air to the mixing chamber via an airflow vortex generator having an airflow deflecting surface with a surface contour oriented to deflect airflow into the mixing chamber in counter-rotating adjacent pairs of airflow vortices. A fuel-air mixture outlet downstream from the mixing chamber releases the fuel-air mixture into a combustor for ignition.

Single Process Production of 3D Nonwoven Shell Structures — Part 1: Web Forming System Design Using CFD Modeling

The paper describes the application of CFD modeling for designing a nonwoven air-laying system to produce 3D webs from staple fibers. The fibers are opened by an opening unit and carried by airflow to 3D porous moulds to form the web. The most critical parameter of the air duct is the divergent angle that in theory should be less than 7o to avoid airflow vortex. The airflow angle to the surface of a 3D mould is different at different points. To produce a 3D web with acceptable thickness uniformity, the airflow through the moulds must be regulated. This can be achieved by modifying the airflow resistance distribution through the 3D mould.

Resonant and non-resonant waves excited by periodic vortices in airflow over water

This paper describes an experimental study, conducted in the I.M.S.T. air–sea interaction tunnel, of waves excited on a water surface by a periodic train of vortices in the air flow above. The water surface, under some conditions, shows a rapidly developing resonant response, while in the non-resonant case waves propagate both upstream and downstream at speeds different from, but dependent upon, the vortex-convection speed.

ACARD report

Airborne contaminants such as pathogens, odors and CO2 released from an individual passenger could spread via air flow in an aircraft cabin and make other passengers unhealthy and uncomfortable. In this study, we introduced the airflow vortex structure to analyze how airflow patterns affected contaminant transport in an aircraft cabin. Experimental data regarding airflow patterns were used to validate a computational fluid dynamics (CFD) model. Using the validated CFD model, we investigated the effects of the airflow vortex structure on contaminant transmission based on quantitative analysis. It was found that the contaminant source located in a vorticity-dominated region was more likely to be “locked” in the vortex, resulting in higher 62% higher average concentration and 14% longer residual time than that when the source was on a deformation dominated location. The contaminant concentrations also differed between the front and rear parts of the cabin because of different airflow structures. Contaminant released close to the heated manikin face was likely to be transported backward according to its distribution mean position. Based on these results, the air flow patterns inside aircraft cabins can potentially be improved to better control the spread of airborne contaminant.