Airflow Behavior Research Articles

Reversing transverse dunes: Modelling of airflow switching using 3D computational fluid dynamics

Airflow dynamics across dune surfaces are the primary agent of sediment transport and resulting dune migration movements. Using 3D computational fluid dynamic modelling, this study examined the behaviour of near surface airflow travelling over transverse (reversing) dunes on a beach system. Wind direction was modelled in two opposing directions (both perpendicular to dune crestline) to investigate surface alteration of flow on the dune topography. Surface shear stress, velocity streamlines and potential sediment flux were extracted from the modelling. The work shows that under SW winds the surface (under the configuration measured) underwent almost 10% more aeolian flux than with opposing NE winds of the same magnitude. Differences were also noted in the airflow behaviour with SW winds staying attached to the surface with less turbulence while NE winds had detached flow at dune crests with more localised turbulence. The work provides detailed insights into how 3D airflow behaviour is modified according to incident flow direction of reversing dune ridges and the resulting implications for their topographic modification. These dune types also provide interesting analogues for similarly scaled Transverse Aeolian Ridges found on Mars and the findings here provide important understanding of flow behaviour of such landforms and their potential movement.

Airflow and Thermal Behavior within Peaches Packaging Box Using Computational Fluid Dynamics - A Preliminary Study

Post-harvest cold storage of peaches is an essential element to maintain the quality of the fruits without any loss. This work aims to present a CFD model, to predict airflow patterns and temperature profiles in ventilated packaging systems, during the forced-air cooling of Peaches stored in a cold chamber. Transient CFD simulations are performed for the chamber containing four ventilated boxes and the evaluation of the results show that the temperature removal near the vent holes and the hand holes is relatively high when compared to other regions of the packaging box. This preliminary study reveals the airflow behavior develop an uneven temperature distribution within the box. To overcome the flaws, future work is focused on modifying the vent hole design to improve the airflow phenomenon to maintain the temperature homogeneity throughout the box.
 Keywords: Peach, Computational fluid dynamics, Airflow, Heat transfer, Packaging

The Effect of Multi-staged Swirling Fluidized Bed on Air Flow Distribution

Fluidization is characterized as an activity that transforms fine solids into a liquid-state via contact with either a gas or a liquid. Currently, Swirling Fluidized Bed (SFB) is one of the new system that contribute on flow mixing to the beds due to the gas source which impart on the solid particles. Further the fluidized beds system are used mostly in the chemical process industry, mineral processing, processes energy and etc. Based on the current fluidized bed system there are still lacking in reducing high pressure drop and keep the energy consumption at high efficient condition. Due to this tips, the conceptual design of a multi-stages SFB was proposed to improve fluidization quality and minimize elutriation at the same time without requiring any extra facilities. By using the simulation method (Ansys Fluent) the behavior of velocity component via selected configuration of fix blades number (30) and through to variant of blade horizontal inclination angle (10°, 12° & 15°) the multi-stage SFB will be investigate. Aims of this study is to identify the air flow behavior at first and second stage blade distributor. Therefore, effect with less blades number in producing on high uniformity velocity would be acquired. The present study has found that by using blade inclination angle of 10° the high velocity magnitude (more than 60 m/s) at two different level of stage distributor can be reached. Moreover, it clearly be seen at blade inclination angle, 15° the velocity uniformity was sustain at certain width and less superficial velocity value occurred compared to other configurations.

CFD Methodology for the Optimization of a Centrifugal Fan with Backward Inclined Blades Using OpenFOAM®

This research develops numerical models through computational tools to evaluate the centrifugal fan with backward inclined blades performance in space and time. This study has been carried out in order to reduce costs, resources, and time consumption commonly employed by traditional design studies in science and engineering. OpenFOAM has been employed to compute the model of the airflow and analyze the energy transfer between flow particles and centrifugal fan blades under real working conditions by means of turbulence models and mathematical algorithms based on advanced theories of thermal and fluids mechanics sciences. A multiple reference frame motion approach is computed with MRFsimpleFOAM solver to mitigate computational resources in the analysis of centrifugal forces and velocity components of the airflow displaced in the rotor-stator interaction zone. Tetrahedral cells have been computed to discretize the airflow control volume, where a partial differential equations system is solved. This method has been supported through a mesh independence study performed to improve the quality of the numerical model and perform the approximation of the airflow behavior to the real working conditions of the industrial centrifugal fan. Output data of the turbulence model have been compared with the experimental curve of the instrumented test bench acquired with LabVIEW software. Results have showed a good agreement between the numerical model and the experimental measurements. The length impeller blade parameter has been selected to develop a numerical optimization and to improve the industrial centrifugal fan performance in a virtual environment.

Assessment of thermal characteristics of square wavy plates

AbstractIn this paper, the thermal characteristics and air flow behavior over heated square plate of wavy configurations are assessed. Two cases of heated wavy configurations were considered, one having an elliptical and other with the sinusoidal cross‐sectional shape to augment heat transfer rate over the plate. To explore the impact of wavy configurations of plate on convective heat transfer, the Rayleigh numbers in the range of 104 to 1013 were considered. The steady‐state two‐dimensional momentum and energy equations were solved using a validated numerical model. The numerical results in terms of Nusselt numbers, Rayleigh numbers, aspect ratio (AR), and flow/temperature distribution over the plate are presented. The variations in the heat transfer coefficient and temperature contours with Rayleigh number and AR of waves were concentrated for both the elliptical and sinusoidal configurations of the plate. The results obtained indicate that the enhancement in heat transfer rate from the heated plate depends on the Rayleigh number, the AR of waves, plate configuration, and the Prandtl number.

A Review on the Air Flow Behaviour in the Intake Pipe

The air flow behaviour plays an important role to provide the better ram air effect inside the intake manifold for combustion. The aim of this study is to review various research paper on air flow in the intake manifold. The study is mainly focussed on the geometrical influence in the air flow behaviour in the intake pipe. Most of the studies emphasized on the computational fluid dynamics (CFD) software which is utilized as tool to investigate the air flow behaviour in the pipe. The important variables that taken into consideration are the shape of pipe inlet, intake pipe diameter, and bending angle of the intake pipe. By conducting the review on the papers, the possible alternatives could be obtained to overcome the air restrictions in the intake pipe and increase the performance of the engine.

Investigating the Effect of Balcony Types on the Naturally-Ventilated Buildings

Natural ventilation is application of natural drift power of wind. Wind can enter and exit buildings through the openings on facades. Hence, Form of facades can impact the air flow behaviour and consequently natural ventilation because they can change the pressure distribution on facades. Moreover, wind pressure difference between windward and leeward facades of buildings is the most important factor affecting natural ventilation. So, it is worthy to focus on facade details in order to enhance natural ventilation. Particularly, geometrical details of facades such as protrusions and indentations e.g. balconies can be considered effective elements on average pressure distribution on both windward and leeward facades, changing pressure difference between these facades. This difference can drive the air flow towards interior spaces significantly. Although this basic rule has been used by different researchers in order to increase natural ventilation buildings, the most research has been studied buildings with flat facades. Therefore, this study aims to investigate effects of balcony types on the natural ventilation. Three types of balcony are simulated and the wind pressure distribution on the windward and leeward facades are analysed. All these simulations are carried out for normally (perpendicular) and obliquely incident wind. This study is performed with Ansys Fluent 18 for all simulations. The results showed that balcony types can affect the pressure distribution on the windward and leeward facades of buildings, leading to the more or less pressure difference between these two facades. These results show that protrusion (protrusive balcony) can cause more complicated pattern of the wind pressure on facades than the others. Also, Re-entrant balcony causes the more pressure differences between the windward and leeward facades and enhances natural ventilation of buildings more considerably than the protrusive one.

Application of double glazed façades with horizontal and vertical louvers to increase natural air flow in office buildings

The results of previous researches clearly indicate that the main concern in applying double skin façades (DSF) is overheating of the cavity and increasing the cooling energy consumption in warm seasons. The present study intends to consider the excessive heat trapped between two skins of double glazed façades in hot arid climates as a driving force to reinforce the natural airflow across the floors of an office building. To meet this purpose, numerical simulation of airflow and heat transfer inside the cavity of the double glazed façades and the adjacent floors, as well as the effect of different types of solar shading systems in horizontal and vertical modes on the airflow has been investigated using the CFD technique. The results show that the stack effect formed inside the cavity has enough power for air suction from the floors of the building and reinforcement of the natural airflow. The type of shading device has a significant effect on the airflow behavior and the heat transfer rate in the facade. In double skin facades with horizontal louvers, the buoyancy forces inside the cavity are stronger and the ventilation rate in the building floors is higher than the model with vertical louvers. On the other hand, due to the stronger convective flow in the cavity with horizontal louvers, the heat flux on the interior glass is higher than the cavity with vertical louvers and part of the heat inside the cavity is transmitted through the interior skin to the occupied spaces.

Physiological and geometrical effects in the upper airways with and without mandibular advance device for sleep apnea treatment

Sleep apnea is a sleep disorder that occurs when the breathing of a person is interrupted during the sleep. This interruption occurs because of the patient has narrowed airways and the upper airways muscles relax, closes in and blocks the airway. Therefore, any forces or reaction originated by the air flow dynamics over the relaxed upper airways muscles could make to close the upper airways, and consequently the air could not flow into your lungs, provoking sleep apnea. Fully describing the dynamic behavior of the airflow in this area is a severe challenge for the physicians. In this paper we explore the dynamic behavior of airflow in the upper airways of 6 patients suffering obstructive sleep apnea with/without a mandibular advancement device using computational fluid dynamics. The development of flow unsteadiness from a laminar state at entry to the pharynx through to the turbulent character in the soft palate area is resolved using an accurate numerical model. Combining the airflow solution with a geometrical analysis of the upper airways reveals the positive effects of mandibular advance device in the air flow behavior (pressure drop). Improved modeling of airflow and positioning of mandibular advance device could be applied to improve diagnosis and treatment of obstructive sleep apnea.

МАТЕМАТИЧЕСКАЯ МОДЕЛЬ ПОВЕДЕНИЯ ВОЗДУШНЫХ ПОТОКОВ НА ТЕРРИТОРИИ ОТКРЫТЫХ УГОЛЬНЫХ СКЛАДОВ

The article discusses the need to use mathematical modeling to study the behavior of air flows in the territory of a port open coal warehouse. To study these processes of the interaction of the movement of air masses on the territory of the port with coal particles, the movement of a point volume of air in an arbitrary space of the air flow, which is inextricable, was considered. This approach allows to take into account all meteorological features of blowing more accurately: wind speed, altitude distribution of speeds, flow turbulization, various geometric parameters of the warehouse. As a result of the numerical implementation of this model by the control volume method, we get the opportunity to analyze the structure of the stream flowing around the coal warehouse and draw conclusions about the nature of dust formation, separation of coal dust particles, displacement of coal dust particles.

Simulation and experimental study on the airflow distribution in rectangular cross-section tunnels

Ventilation is quite important for mine safety. The airflow behavior and the influence of the ventilation parameters on the airflow distribution in rectangular tunnels were investigated by experimental and simulation methods. Then the relationship between the distribution feature of the average velocity and the parameters of tunnel cross-section was analyzed quantitatively by mathematical method. The results showed that the average velocity points show a continuous circular distribution and the simulation results were in accordance with the experimental results. The shape of cross-section is the critical factor influencing airflow behaviour, and the ventilation velocity had little influence on the distribution of the average velocity points. In the region where the velocity was larger than the average velocity, the velocity gradient was small, and as the distance to the wall increased, the velocity increased slowly. While in the region where the velocity was smaller than the average velocity, the velocity gradient was large, and the velocity changed more quickly. Based on the simulation and experimental data, a group of the characteristic equations were developed and the location of the average velocity can be obtained conveniently while the dimension of the tunnel was known.

Combined Heat and Mass Transfer of Fluid Flowing through Horizontal Channel by Turbulent Forced Convection

In the present paper, we report a numerical study of dynamic and thermal behavior of the incompressible turbulent air flow by forced convection in a two-dimensional horizontal channel. This one contains the complicated form of the deflector which has been studied by varying the inclination angle from φ = 40°, φ = 55° to φ = 65°. The baffles are mounted on lower and upper walls of the channel. The walls are maintained at a constant temperature (375 K), the inlet velocity of air is Uint = 7.8 m/s, and the Reynolds number Re = 8.73 × 104. A specifically developed numerical model was based on the finite-volume method to solve the coupled governing equations and the SIMPLE (Semi Implicit Method for Pressure Linked Equation) algorithm for the treatment of velocity-pressure coupling. For Pr = 0.71, the results obtained show that (i) the streamlines and isotherms are strongly affected by the inclinations angles at Re = 8.73 × 104, (ii) the friction coefficient near the baffles increases under the angle exchange effect, and (iii) for a constant Re, the local Nusselt number at the walls of the channel varies with increasing the inclination angle of the deflector. Furthermore, the deflectors are generally used to change the direction of the structure of flow and also to increase the turbulence levels. We can conclude that the contribution of inclined baffles improves the increase of heat and mass transfer in which the Nusselt number at a certain angle increases noticeably.

Analysis for determining the impact of air quality and thermal comfort in an enclosed cavity

Quality of the indoor environment has been in the focus of many researchers since decades. People spend about 80–90% of the total time within buildings which may be an office, house, gymnasium, etc. So, there is a need to check the environmental conditions on the basis of thermal comfort as well as the condition of indoor air. Although, condition of air and thermal comfort are considered to be interdependent, as if the quality of air is not good, it will result in uncomfortable dwelling conditions and vice-versa. Many researchers have tried to evaluate the thermal comfort and quality of indoor air theoretically with the help of the thermal sensation scale as per the Fanger model. Although, a limited simulation work is published describing the effect of airflow generated from the ceiling fan on the quality of indoor air in the building envelope. This communication is an attempt to examine the impact of indoor air quality by considering the influence of temperature, velocity and humidity level of air, inside an enclosed cavity for a specific location. This work involves the use of an SST k-ω based turbulence model in order to study the turbulent behavior of airflow generated by ceiling fan. The radiation model has been considered in order to study the temperature variation inside the cavity. It also incorporates the evaluation of relative humidity and PMV-PPD inside the enclosed cavity for attaining comfortable dwelling conditions. Investigation revealed the average predicted mean vote value to be −0.89, which can be considered as an ideal condition for comfortable dwelling.

Effect of the chimney design on the thermal characteristics in solar chimney power plant

Solar chimney power plant (SCPP) is an interesting project to produce clean and sustainable energy. An efficient SCPP system requires a very high chimney, and thus the optimization of the chimney shape presents an important way to enhance the SCPP performance. The aim of this paper is to analyze the effect of the divergent chimney shape on the airflow behavior inside SCPP. A comparison between four chimney shapes is carried out using CFD method: two cylindrical chimneys with different diameters and two divergent chimneys with different shapes. Indeed, both parameters were studied: the ratio of the inlet and outlet diameter of the chimney and the shape of the chimney which both hyperboloid and conical. The SCPP prototype was tested numerically and experimentally to validate the present computational outcomes. The obtained results confirm that the divergence shape affects directly the efficiency of the SCPP system. Moreover, the hyperboloid chimney presents the efficient solution which produces an important power output with keeping the chimney height constant.

Study of Indoor Ventilation Based on Large-Scale [DNS by a Domain Decomposition Method

This paper presents a large-scale Domain Decomposition Method (DDM) based Direct Numerical Simulation (DNS) for predicting the behavior of indoor airflow, where the aim is to design a comfortable and efficient indoor air environment of modern buildings. An analogy of the single-phase convection problems is applied, and the pressure stabilized domain decomposition method is used to symmetrize the linear systems of Navier-Stokes equations and the convection-diffusion equation. Furthermore, a balancing preconditioned conjugate gradient method is utilized to deal with the interface problem caused by domain decomposition. The entire simulation model is validated by comparing the numerical results with that of recognized experimental and numerical data from previous literature. The transient behavior of indoor airflow and its complexity in the ventilated room are discussed; the velocity and vortex distribution of airflow are investigated, and its possible influence on particle accumulation is classified.

The Use of Data Mining Techniques in Predicting the Noise Emitted By the Trailing Edge of Aerodynamic Objects

Aerodynamic is a branch of fluid dynamics that evaluates the behavior of airflow and its interaction with moving objects. The most important application of aerodynamic is in aerospace engineering, designing and construction of flying objects. Reduction of noise emitted by aerodynamic objects is one of the most important challenges in this area and many efforts have been to reduce its negative effects. The prediction of noise emitted from these aerodynamic objects is a low-cost and fast approach that can partially replace the "fabrication and testing" phase. One of the most common and successful tools in prediction procedures is data mining technology. In this paper, the performance of different data mining algorithms such as Random Forest, J48, RBF Network, SVM, MLP, Logistic, and Bagging is evaluated in predicting the amount of noise emitted from aerodynamic objects. The experiments are conducted on a dataset collected by NASA, which is called "Airfoil Self-Noise". The obtained results illustrate that the proposed hybrid model derived from the combination of Random Forest and Bagging algorithms has better performance compared to other methods with an accuracy of 77.6% and mean absolute error of 0.2279.

Experimental study of ice accretion on S826 & S832 wind turbine blade profiles

To optimize the aerodynamic performance and reduce production losses of wind turbine operating in icing conditions, it is necessary to better understand the ice accretion physics along wind turbine blade. This paper describes a case study of ice accretion physics and its effects on aerodynamic performance of S826 and S832 airfoils for dry and wet ice conditions. Both these airfoils have different geometric characteristics and are suitable for horizontal axis wind turbine blade. Icing tunnel experiments are carried out at Cranfield University to understand and simulate the ice accretion on both profiles. Results show that difference in geometric characteristics of both airfoils affects the ice accretion and more complex ice shapes are observed in case of S832 profile compared to S826. Analysis show that ice thickness is higher in case of dry rime ice conditions as compared to wet ice, whereas more complex ice shapes are observed for wet ice conditions. Computational Fluid Dynamics (CFD) based numerical analysis are carried out to study the airflow and droplets behaviour and to estimate the aerodynamic performance of both clean and iced profiles. No numerical simulations of ice accretion are carried out. CFD analysis show a change in airflow behaviour for iced profiles which leads to a decrease in aerodynamic performance, when compared with the clean profiles. The change in aerodynamics performance is higher for S832 than S826 particularly for wet ice conditions.

Influence of the collector concavity on the airflow behavoir within solar chimney power plant

ABSTRACTSolar Chimney Power Plant (SCPP) is a large-scale system which is designed to produce electricity from the solar energy. This thermal device is characterized by a high investment cost and a low thermodynamic efficiency. The optimization of these thermal systems is required. The solar collector is one of the important parts of the solar chimney power plant. The collector is considered as a heat generator by using the greenhouse effect. In this paper, a novel design of the collector is proposed in order to increase the overall efficiency of the SCPP. In fact, impact of the collector concavity on the system performance is studied. Using CFD method, two-dimensional steady simulations were performed while varying the concavity ratio of the collector (CC). The specific ratio is defined as the curvature radius of the collector roof divided by the collector radius. The airflow behavior is examined by analyzed the static temperature, the magnitude velocity, the static pressure and the overall percentage of the power output rise. The numerical simulations were validated using experimental data gathered from a small prototype build at the National School of Engineers of Sfax, Tunisia. The predicted outcomes showed that a concave collector could enhance the overall performance of the solar chimney power plant.

CFD study of aerodynamic sensitivity to air deviation angle for a hatchback vehicle

Movement is the base of most nowadays activities. For this purpose, vehicles that have specific characteristics for various needs were developed. The current legislation enforces an aerodynamic homologation process to assess a vehicle’s CO2 footprint. This process has to be done in specific conditions, with airflow at 0 degree deviation. The increasing concerns toward pollution will soon lead to the introduction of new rules meant to closely simulate real life vehicle usage, like the RDE test. The current paper has the purpose to analyse, using the CFD method, the influence of the directionality of the airflow (i.e. front-at 0 degree deviation and at various deviation angles) on the aerodynamic performance of a vehicle. The paper studies the airflow behaviour of a hatchback body type vehicle for airflow direction angles between 0 and 20 degrees, through Cd parameter. The focus of the analysis was on air direction (± angles) and simulating time. Due to vehicle asymmetry, the results were different in case of positive and negative values of the airflow angle. The simulation time leads to slightly different Cd due to different averaging periods. Obtained results indicate the necessity of future investigations towards the optimisation of aerodynamic elements in crosswind conditions.

Tecnologías de impresión 3D: evaluaciones de FDM y Polyjet en la fabricación de autopartes de automóviles

El objetivo del estudio fue evaluar las tecnologías de impresión 3D realizadas por Modelado Deposición Fundida (FDM) y PolyJet, a partir de ensayos mecánicos con materiales de Acrilonitrilo Estireno Acrilato (ASA) y VeroWhitePlus RGD 835 para la selección del material y tecnología adecuada en la fabricación de ductos de aire aplicados a autopartes automotrices. Con el fin de alcanzar el objetivo se realizaron pruebas de tracción mecánica a probetas fabricadas por ambas tecnologías; según la norma ASTM D638-14 para las pruebas de tracción y para los ensayos a flexión con la norma ASTM 790; para evaluar el comportamiento del flujo del aire en ducto se seleccionó como caso de estudio el ducto de aire empleado en la camioneta pick up Toyota Stout 2200 modelado por medio del software Ansys Student. Los resultados mostraron que el material VeroWhitePlus RDG 835 utilizado en la construcción del ducto por medio de la tecnología PolyJet presentó los mejores resultados con límite de fluencia a la tracción de 4.7 MPa y esfuerzo máximo de flexión de 28 MPa.