Aerodynamic Study Research Articles

Experimental Validation of Total Energy Control System for UAVs

This paper presents an analysis of a Total Energy Control System (TECS) introduced by Lambregts to control unmanned aerial vehicle (UAV) velocity and altitude by using the total energy distribution. Furthermore, an extended Kalman filter (EKF) approach was used to predict aircraft response in terms of angular rates and linear acceleration during a test flight campaign. From both approaches, state equations were obtained to model the aircraft using Matlab-Simulink. From an aerodynamic study, airplane characteristics were obtained in terms of non-dimensional derivatives and compared to those obtained from the experimental methods. It was determined that TECS approach was very accurate; however, disturbance errors could be decreased by adjusting some model parameters. On the other hand, it was difficult to obtain a real estimation from the EKF method due to the presence of turbulence during flight and the relatively low inertia of the scale model. Dynamic characteristics were validated using a low-cost inertial sensor that cab be easily integrated in UAV platforms. The gathered data can be used to predict model characteristics by integrating the information into flight simulators for future design development.

Study of aerodynamics of stream flow in server rooms using numerical modeling

This paper analyzes various schemes of air exchange in server rooms. Top-down and down-top vertical cooling schemes for small server rooms using local AC systems were analyzed. Numerical models were developed for the study of heat and mass transfer and server aerodynamics, which make it possible to evaluate the cooling efficiency of electronic equipment when placed in an arbitrary configuration. To study the thermal and velocity fields, numerical simulation of the stream flow processes was performed using the FlowVision software. This paper shows the advantage of the selected air-conditioning scheme compared to the existing ventilation system. Modeling results may be used for designing small server rooms.

Study of Aerodynamics of a Prospective Descent Module Descending in the Atmosphere of Mars

The paper presents the methods and the calculation results for the flow around a prospective descent module and physicochemical processes in the flow field near the vehicle in the aerodynamic braking mode in the Martian atmosphere. The boundary conditions and the models of chemical processes corresponding to the actual conditions of entering the planet’s atmosphere are investigated.

Aerodynamic efficiency and performance enhancement of fixed-wing UAVs

The present work aims in providing guidelines for the aerodynamic and performance optimization of fixed-wing Unmanned Aerial Vehicles (UAVs) that operate in the low-speed subsonic regime. Using a combination of textbook methods, low-fidelity and high-fidelity aerodynamic analysis tools, an aerodynamics and drag breakdown analysis is made on a reference UAV wing platform. Then, a complete drag bookkeeping study is made on the corresponding reference UAV configuration, providing the contribution of each part to the total drag budget for various angles of attack. Using the results of the aerodynamic investigations as guide, a thorough drag-reduction technologies screening is made based on existing literature, with the discussion also including integration and realization issues. Concluding, the most promising technologies are proposed taking into account the potential benefits as well as the technology readiness. The current work can serve as a base for future, more detailed, aerodynamic and performance enhancement studies for UAVs.

Lift, drag and pitching moment performances of different wing profiles for MAV wings

The wing profile for Micro Air Vehicle (MAV) can be easily developed through the polynomial equation method which is proven in generating good aerodynamic performances. However, the study demands more studies in profile configurations to provide more evidence which interrelated with its aerodynamic performances. Thus, in this works, an aerodynamic study on different wing profiles configurations has been carried out. Profile 1, Profile 2 and Profile 3 were developed through the 3rd order polynomial equations have analyzed based on simulation works by using ANSYS-CFX. Based on the lift distribution analysis, it shows that Profile 3 has a huge advantage in generating better lift distribution (CL) among the wing profiles. Profile 3 able to produce at least 20% to 22.9% better maximum lift coefficient (CLmax) and CL magnitude compared to the other wing profiles. Despite its benevolent in CL performances, Profile 3 has induced the highest drag (CD) penalty among the wing profiles. Profile 3 has consistently produced at least 57.5% higher CD magnitude compared to other wing profiles. However, in terms of moment coefficient (CM) performances, Profile 3 has shown a promising ability in providing better wing stability compared to the other wing profile due to steeper CM slope.

Aerodynamic structure of a swirling turbulent flow in a vortex furnace

Insufficient study of the swirling flow structure, stability of high-temperature circulating zones, intensity of fuel and oxidizer mixture formation and other determining phenomena in the vortex furnaces indicates insufficiency of scientific substantiation of the methods for their calculation. Therefore, further detailed studies of aerodynamics of a turbulent swirling flow in a vortex chamber with intersection of the main flow by the inlet tangential jets aimed at the development of promising combustion devices seem to be relevant. The results of numerical simulation of the turbulent swirling flow aerodynamics with preference given to the modern models of turbulence and numerical schemes of high-order approximation are presented.

Study of aerodynamics of the jet spreading over cylindrical surface

The purpose of this work is to study the fields of average values of velocity in a turbulent air jet propagating along a smooth cylindrical surface with an adjustable nozzle width being b, the curvature parameter SR and Re number on both convex and concave surfaces. To identify basic patterns of physical phenomena occurring in the boundary layer, it has been established that in universal coordinates, the wall velocity profiles have a universal nature in the region of a change in the curvature parameter 0 ⩽ SR ⩽ |±0.12|, and virtually coincide with the velocity profiles of a turbulent boundary layer on a flat plate in a uniform flow past, except for the velocity peak region. This is due to the fact that the longitudinal pressure gradient is 104 ÷ 105 times lower than transverse pressure gradient. According to our data, it has been established that the excess static pressure near the streamlined surface with a distance from the nozzle and an increase in jet thickness can reach up to 30–40% of the velocity head.

Aerodynamic study of the corrugated airfoil at ultra-low Reynolds number

In this study, Aeshna cyanea dragonfly forewing mid-cross-section corrugated airfoil was simulated at ultra-low Reynolds number. The corrugated airfoil was compared with its smooth counterpart to study the effect of the corrugations upon the aerodynamic performance. Unsteady two-dimensional laminar flow was solved using FLUENT. This study was divided into gliding phase and flapping phase. In the gliding phase, the corrugated airfoil produced a higher lift force with respect to the profiled airfoil at both tested Reynolds numbers ([Formula: see text], [Formula: see text]) with comparable drag coefficient for all the tested angles of attack. In the flapping phase, both the corrugated airfoil and the flat-plate have a very similar flow behavior which yields a very similar aerodynamic performance at Re[Formula: see text]. A structural analysis was performed to compare the corrugated airfoil with the flat-plate. The analysis revealed the superiority of the corrugated airfoil over the flat-plate in decreasing the deflection under the applied load. The reduced frequency was varied to study its impact on the aerodynamic performance. By increasing the reduced frequency, the thrust and the lift forces increased by [Formula: see text]% and [Formula: see text]%, respectively. Any increase in the reduced frequency will increase lift and thrust forces, but the propulsive efficiency will deteriorate.

Aerodynamic study of moto rcycle racing wheels: A performance evaluation based on numerical CFD simulations

aerodynamic study of moto rcycle racing wheels: A performance evaluation based on numerical CFD simulations

Development and Analysis of Heat Exchanger for Efficient Heat Transfer for L-Shape Wind Tunnel

As automation and mechanical industry growing towards next era, it becoming crucial to design each element of plant with more productive material. Out of many parameters, heat transfer is very important area of study to lower the rate of failure of numerous machines. For heat transfer control there is a need of design of efficient heat exchanger. A heat exchanger can be designed for minimization of heat energy from the wind tunnel. Impact on HE performance is important due to the thermal resistance of wind tunnel. Thermal resistance is the heat property of the tunnel material and dimensions of tunnel. Looking at application level performance, the thermal resistance is crucial element in case of aerodynamic study. The similar study is done for Apolo11 spacecraft which was important in case of landing back to earth as traveling to earth with high speed generated heat which can damage spacecraft body. Such study further leads to various domains like material research, human impact study etc. The most recently, asteroid is passed nearby of earth orbit, where aerodynamic study of NASA evaluated the pre-collision effects where thermal properties are analyzed considering the atmospheric nearby orbit as a tunnel of wind/pressure. Hence, the scenarios must be considered for heat transfer / heat exchanger design specific to the each application domain. This paper discusses about the asteroid bypass which generates heat as a major heat transfer to earth and the automobile specific modeling of heat exchanger for wind tunnel. The focus is kept on heat exchanger design which can be suggested for automobile testing procedure.

Aerodynamic validation studies on the performance analysis of iced wind turbine blades

Ice accretion on wind turbine blades distorts blade profiles and causes degradation in the aerodynamic characteristic of the blades. In this study ice accretion on turbine blades are simulated under various icing conditions, and the resulting power losses are estimated. The Blade Element Momentum method is employed together with an ice accretion prediction methodology based on the Extended Messinger model in a parallel computing environment. The predicted iced profiles are first validated with the experimental and numerical data available in the literature. 2D flow solutions and aerodynamic loads over iced blade profiles are obtained with 3 different flow solvers of increasing fidelity; XFOIL, an open-source panel code coupled with a turbulent boundary layer model, SU2, an open-source RANS solver, and METUDES, an in-house DDES solver. The power production losses of a 30 kW wind turbine operating with iced blades are then investigated in detail. It is shown that the XFOIL-based tool developed for the performance analysis of iced wind turbines successfully predicts ice profiles on turbine blades under various icing conditions and the consequent power losses. About 20% power loss is predicted for a 30 kW wind turbine exposed to icing conditions for an hour.

CFD modeling of varying complexity for aerodynamic analysis of H-vertical axis wind turbines

Computational fluid mechanics (CFD) is considered as an efficient approach for studying aerodynamic characteristics of vertical axis wind turbines (VAWTs). Currently, 2D Unsteady Reynolds-Averaged Naviere Stokes (URANS) is widely applied, although previous researches revealed its limit accuracy in the aerodynamic analysis. This paper investigates the accuracy and feasibility of various CFD modeling techniques, namely 2D URANS, 2.5D URANS, 2.5D large eddy simulations (LES), 3D URANS and 3D LES, in the aerodynamic study of VAWTs through a comparison with the wind tunnel results. Compared with the URANS method, the LES approach can provide more accurate prediction on the aerodynamic performance for VAWTs operating at the dynamic stall. The significant improved simulation results by 2.5D LES imply that the neglect of tip vortices may not be the major mechanism causing the over prediction in 2D and 2.5D URANS. 2.5D LES can be regarded as a promising and efficient approach to investigate the aerodynamic behaviors of VAWTs, considering the compromise between the accuracy and computational cost among 2.5D LES, 3D LES and 3D URANS. Furthermore, considering the huge amount of time consumed by CFD simulations, a hybrid meta-model is therefore proposed to predict the power coefficient of VAWTs. The prediction results show that the accuracy of the hybrid meta-model satisfies the requirements, and the calculation time is also reduced.

A review of aerodynamic studies on dragonfly flight

In the recent decades, the design and development of biomimetic micro air vehicles have gained increased interest by the global scientific and engineering communities. This has given greater motivation to study and understand the aerodynamics involved with winged insects. Dragonflies demonstrate unique and superior flight performance than most of the other insect species and birds. They are capable of sustained gliding flight as well as hovering and able to change direction very rapidly. Pairs of independently controlled forewings and hindwings give them an agile flying ability. This article presents a review of all published journal articles, listed in the Thomson-Reuters Web-of-Science database (1985–2018), that are related to the flight aerodynamics of dragonflies or micro air vehicles that biomimic them. The effects of dragonfly wing motions and interactions (between forewing and hindwing) that are necessary to generate the appropriate aerodynamic forces in different flight modes are described. The associated power requirements of these modes are also addressed. This article aims to provide a valuable reference to the aerodynamic design and control of dragonfly-inspired biomimetic micro air vehicles.

Hybrid RANS/LES Turbulence Model Applied to a Transitional Unsteady Boundary Layer on Wind Turbine Airfoil

A hybrid Reynolds-averaged Navier Stokes/large-eddy simulation (RANS/LES) turbulence model integrated with a transition formulation is developed and tested on a surrogate model problem through a joint experimental and computational fluid dynamic approach. The model problem consists of a circular cylinder for generating coherent unsteadiness and a downstream airfoil in the cylinder wake. The cylinder flow is subcritical, with a Reynolds number of 64,000 based upon the cylinder diameter. The quantitative dynamics of vortex shedding and Reynolds stresses in the cylinder near wake are well captured, owing to the turbulence-resolving large eddy simulation mode that was activated in the wake. The hybrid model switched between RANS and LES modes outside the boundary layers, as expected. According to the experimental and simulation results, the airfoil encountered local flow angle variations up to ±50°. Further analysis through a phase-averaging technique found phase lags in the airfoil boundary layer along the chordwise locations, and both the phase-averaged and mean velocity profiles collapsed into the Law-of-the-wall in the range of 0 < y + < 50 . The features of high blade-loading fluctuations due to unsteadiness and transitional boundary layers are of interest in the aerodynamic studies of full-scale wind turbine blades, making the current model problem a comprehensive benchmark case for future model development and validation.

AERODYNAMICS OF JETS INTERACTING WITH A FLAT SURFACE

In this paper, the development features of a single free jet of hightemperature nitrogen interacting with a flat surface were studied. Calculation of the heat exchange process during heating by the attacking jets is very difficult to implement analytically due to complexity of the gas-dynamic processes occurring both in a single jet and in a system of jets interacting with the metal. The computational difficulties are aggravated by the fact that when interacting with the surface the jet as such disappears. The flat (fan) flow interacts with the surface: form, aerodynamic properties and thermal state of the flow strongly differ from those of the original jet. The studies were conducted on the basis of numerical simulation in the FloEFD software and computing complex for multiphysical simulation based on solution of the equations of gas dynamics and heat transfer. The solved system of equations consisted of Navier-Stokes equations, equations of energy and continuity and was supplemented by k – ε turbulence model. A three-dimensional model was developed for simulation, the necessary properties, initial and boundary conditions were specified. In the study of aerodynamics of a single high-temperature jet interacting with the surface, the main defining values were: nitrogen flow rate from the nozzle U0 , nitrogen temperature T, internal diameter of the nozzle d0 , distance from the nozzle section to the surface h, distance from the critical point (point of intersection of the jet axis with the surface) along the flow radius r. Data on the gas velocity decrease as the jet develops due to the loss of initial energy to engage the motionless surrounding gas in motion, is presented. The studies have shown that increase in the initial velocity of gas outflow brings the area of higher velocities closer to the surface both in the jet itself and in the fan jet. This factor contributes to heat transfer intensification. In addition, high speeds increase the total thickness of the fan flow and reduce the thickness of hydrodynamic boundary layer, which increases with distance from the critical point.

Design and performance of an aeroacoustic wind tunnel facility at the University of Bristol

This paper provides an overview of the design and performance of the new aeroacoustic wind tunnel facility at the University of Bristol. The purpose of the facility is to enable near- and far-field acoustic and aerodynamic studies on a variety of different aerodynamic components and to examine diverse noise control techniques. The facility comprises a large acoustic chamber, anechoic down to 160 Hz, and a temperature controlled closed-circuit wind tunnel with an open test section. The wind tunnel features two interchangeable rectangular nozzles with a partially shared contraction. Both nozzles are shown to possess a high flow quality with high flow uniformity and low turbulence intensity of 0.09% and 0.12% for the smaller and larger nozzle, respectively. The maximum attainable flow speeds are 40 m/s for the larger nozzle and 120 m/s for the smaller nozzle corresponding to Reynolds numbers of 2.7 million and 8.1 million per meter, respectively. In this paper, we will present various aerodynamic and acoustic results to characterize the performance of the facility. The background noise levels are found to be sufficiently low and the far-field noise measurements from a flat plate, a round cylinder and a NACA 0012 airfoil compare favorably to existing experimental observations.

CFD modeling and optimization of pre-cooling conditions in a cold room located in the South of Tunisia and filled with dates.

Thermal and aerodynamic study is performed on a cold store room installed in the south of Tunisia and filled with about 11 tons of dates to be cooled from harvest conditions to about 5°C. The main object of this study is to define the suitable precooling conditions leading to homogeneous storage temperature inside the room. The considered cold room is of about 67m3 of volume and equipped with an evaporator giving the required refrigeration capacity. Three-dimensional CFD model is established taking into consideration the local environmental parameters. The model SST k-ω is used to analyze the air turbulences. For normal design of the cold store room and during a precooling period of 40h, the air velocity and temperature are determined in the different locations inside the room and vary between 0.25-7m/s and 3-6°C. While the product temperature remains higher than the required storage conditions of about 12°C. A new cold store room design is proposed using specific aerodynamic air deflector profiles. That permits to improve the heat transfer between the cold air and product. The precooling period is reduced of about 10h and the average product temperature reaches 6°C.

An aerodynamic simulation study for the best positioning of a device to improve Operation Room air quality

BACKGROUND: Proper air ventilation and filtration in Operating Rooms (OR) are two prevention measures to avoid Surgical Site Infections (SSI), which cause increase of hospital staying, cost and death. For identifying how system ventilation variations may impact on the quality of OR air, ad hoc researches need be conducted. The aim is to study how a mobile air particle filtering system may impact on the air quality of the OR when placed in two different positions. METHODS: This descriptive study was conducted during April-May 2018 in an Italian University Hospital. We measured inflow and outflow air ventilations of both an OR and a mobile novel air decontamination-recirculation system unit having a patented crystalline ultraviolet C reactor and a high efficiency particulate air filter. OR was redesigned using the software Solidworks 2017 3D. Using experimental data, the interaction of airflows was graphically simulated by placing the device both next to the main OR entrance, with its airflow towards the surgical bed, and next to the latter, with the airflow towards the main entrance. RESULTS: The device has been able to modify the main flow of a normal air diffusion from the ceiling vents and has created a low pressure effect that drags the air into contact with potentially contaminated surfaces. Air contamination can occur when OR door is opened. If the device is positioned with its air intake next to the door, entry of particulate is facilitated, reducing the effectiveness of the positive pressure inside the OR. To avoid possible contamination caused by the device airstream, we have oriented its air intake towards the operating table. if the door is opened, the airstream helps to prevent the entry of contaminants. CONCLUSIONS: Different positioning of extra flows can significantly impact on air dynamic. Ad-hoc environmental measures are necessary for the most efficient positioning of the device.

Structural analysis of offshore wind turbine blades using finite element method

Wind energy is one among the most promising renewable energy sources, and hence there is fast growth of wind energy farm implantation over the last decade, which is expected to be even faster in the coming years. Wind turbine blades are complex structures considering the different scientific fields involved in their study. Indeed, the study of blade performance involves fluid mechanics (aerodynamic study), solids mechanics (the nature of materials, the type of solicitations …), and the fluid coupling structure (IFS). The scope of the present work is to investigate the mechanical performances and structural integrity of a large offshore wind turbine blade under critical loads using blade element momentum. The resulting pressure was applied to the blade by the use of a user subroutine “DLOAD” implemented in ABAQUS finite element analysis software. The main objective is to identify and predict the zones which are sensitive to damage and failure as well as to evaluate the potential of composite materials (carbon fiber and glass fiber) and their effect on reduction of rotor’s weight, as well as the increase of resistance to wear, and stiffness.

Experimental Study of Aerodynamics and Wingtip Vortex of a Rectangular Wing in Flat Ground Effect

The ground effect on the aerodynamics and tip vortex flow of a rectangular wing is investigated experimentally at Re = 2.71 × 105. The results show that there is a large lift increase with reducing ground distance. By contrast, only a small drag increase is observed in ground effect except in close ground proximity for which a great drag increase appears. The tip vortex also moves further outboard and upward with reducing ground distance. Near the ground, there is the presence of a corotating ground vortex (produced by the rolling up of the boundary layer developed on the ground surface), leading to an increased vortex strength. In extreme ground proximity, a counterrotating secondary vortex (SV) (induced by the crossflow of the tip vortex), relative to the tip vortex, appears which causes a reduced vortex strength and a lowered lift-induced drag, as well as a vortex rebound. The impact of ground effect on the vortex flow properties is also discussed. The lift-induced drag, computed based on the crossflow measurements via the Maskell wake integral method, in ground effect is also compared against the inviscid-flow predictions and wind tunnel total drag force measurements.