Aerodynamic Study Research Articles

ARCHITECTURAL-BUILDING AERODYNAMICS

This article gives a brief historical digression about the formation of architectural and building aerodynamics as a separate branch of the construction science. The main methods and approaches to the solution of problems of architectural and building aerodynamics are listed; the classification of problems of aerodynamics of structural steel according to the studied objects is given; main peculiarities of the research in selected areas are briefly indicated. The aim of the work is to systematize existing approaches to assessing wind impact on structural steel taking into account some modern international requirements, as well as to choose the optimal method for solving this problem in relation to various structural steel. It is established that, currently, the study about wind impact is especially important for high-rise buildings, structures, and structural steel nonresistant to dynamic loads (long span bridge conduits, gins polarized, thin-shell tubes, etc.), as well as for residential estates with restrained urban conditions. It is necessary to carry-out these aerodynamic studies at the designing stage for the above objects because it is directly related to the issues of reliability and safety.

An improved formulation for speed of sound in two-phase systems and development of 1D model for supersonic nozzle

The Speed of sound is one of the most prominent parameters in the fluid dynamics and aerodynamic studies. A major challenge lies in the fact that two-phase region properties are dramatically different from the single phase condition and the simple models do not satisfy the adequate accuracy required for the sound speed prediction. The present research explores various attempts for calculating the speed of sound and suggests a new practical equation which is correlated with fluid properties and it is developed by genetic Algorithm. The obtained results are encouraging and the final derived model has the most accuracy for the two-phase region covering different types of thermodynamic processes. In addition, the new model and the classic 1D model are combined to perform an analysis of the role of the two-phase sound speed consideration. The temperature and the pressure profiles inside a converging - diverging nozzle are investigated, representing the phase-change phenomena inside the supersonic nozzle. The related Mach number and the nozzle performance are studied using the proposed model.

Aerodynamic noise numerical simulation and noise reduction study on automobile alternator

Aerodynamic noise is the predominant component of automobile alternator noise at high speed, which directly affects the noise characteristic and noise control of alternator. Based on Lighthill acoustic theory, the aerodynamic noise of an automobile alternator was simulated with three-dimensional, Large eddy simulation (LES) and Ffowcs Williams-Hawkings (FW-H) acoustic model, and the aerodynamic noise reduction research was conducted through optimizing the front fan blade spacing angle of alternator with vector composition method while considering high fan flow and optimal noise frequency components for reduced harmonic rotating noise of alternator. The results show that the sound pressure amplitude of the primary aerodynamic noise components simulated with LES are in good agreement with experimental ones, and the dominant harmonic frequency components of aerodynamic noise are in the 4th, 6th, 8th, 10th, 12th and 18th orders and the A-weighted sound pressure level of one-third octave mainly concentrates in 1120-7000 Hz. The average total noise level of alternator noise is decreased by 2.58 dB, and the mass flow of monitoring surface of fan blade is increased by 1.36 g/s with 5.80 dB decrease in the sound level of the 12th and 18th harmonic orders on average with optimized front fan blade spacing angles, which verifies the effectiveness of the noise reduction method proposed in this paper.

Heat-Aerodinamic Efficiency of Helical Tubes

Background . Research and development of new highly efficient heat exchange surfaces. Objective . Determination of the heat-aerodynamic efficiency of the new equally developed surfaces in the form of helical tubes packets. Methods . Experimental and numerical study of heat transfer and aerodynamics of helical tubes chess packages. Results . The specific heat flux which is taken away from packages of helical tubes is 30–65 % bigger than a specific heat flux which is taken away from the corresponding (respective) packages of smooth tubes at equal costs for pumping the heat transfer agent. The maximal sizes are reached for packages of type 3 tubes at \[\sigma _{2}=1,46.\] Conclusion . Application of helical tubes allows increasing the intensity of heat exchange with moderate growth of an aerodynamic drag therefore it is possible to improve mass-dimensional characteristics of heat exchange devices significantly.

Aerodynamic design optimization for low Reynolds tandem airfoil

A series of aerodynamic design optimization studies are performed to investigate the performance of two-dimensional tandem airfoil at low Reynolds number of 220,000. A total of 23 design variables, including decalage, gap, stagger, and airfoil profile variables are considered. Hierarchical evolutionary algorithm together with dynamic metamodel optimization is used to achieve the maximum lift-to-drag ratio for tandem airfoil. The studies investigate the impact of various design variables on optimized tandem airfoil. The results show that tandem airfoil in lower Reynolds flow has better aerodynamic performance at high angle of attack. And the lift-to-drag ratio can be further increased by 11.9% when airfoil profile variables are introduced. Morphing tandem airfoil can overcome low lift-to-drag ratio at lower lift coefficient, and is attractive for unmanned aircraft.

Aerodynamic study of a generic car model with wheels and underbody diffuser

Being a continuous subject of research, this study presents new aspects regarding the relevance of underbody diffusers in road vehicle aerodynamics. Using a generic car model on wheels as a reference, the effect of the wheels on the body fitted with an underbody diffuser was studied, where the diffuser length and angle were varied within ranges which are applicable for hatchback passenger cars. The results show that the vortices which originate from the rear wheelhouses have a major impact on the aerodynamics of the underbody diffuser, which results in increasing of drag and lift of the body. For cases studied, the average drag and lift increment due to the addition of wheels were (ΔcD)mean = 0.058, respectively (ΔcL)mean = 0.243. The lift of the body on wheels decreases with both diffuser length and diffuser angle, and there are situations when it may become negative as for a body without wheels. The results show also the possibility to reach a minimum drag according with normalised diffuser length.

Design and analysis of a task-based parallelization over a runtime system of an explicit finite-volume CFD code with adaptive time stepping

FLUSEPA (registered trademark in France No. 134009261) is an advanced simulation tool which performs a large panel of aerodynamic studies. It is the unstructured finite-volume solver developed by Airbus Safran Launchers company to calculate compressible, multidimensional, unsteady, viscous and reactive flows around bodies in relative motion. The time integration in FLUSEPA is done using an explicit temporal adaptive method. The current production version of the code is based on MPI and OpenMP. This implementation leads to important synchronizations that must be reduced. To tackle this problem, we present the study of a task-based parallelization of the aerodynamic solver of FLUSEPA using the runtime system StarPU and combining up to three levels of parallelism. We validate our solution by the simulation (using a finite-volume mesh with 80 million cells) of a take-off blast wave propagation for Ariane 5 launcher.

PdFOAM: A PIC-DSMC code for near-Earth plasma-body interactions

Understanding the interaction of the near-Earth space environment with orbiting bodies is critical, both from a design and scientific perspective. In Low Earth Orbit (LEO), the interaction between the Ionosphere and orbiting objects is well studied from a charging perspective. Not well understood is the effect of the Ionosphere on the motion of LEO objects i.e. ionospheric aerodynamics. This paper presents the implementation, validation, and verification of the hybrid electrostatic Particle-in-Cell (PIC) - Direct Simulation Monte Carlo (DSMC) code, pdFOAM, to study both the neutral and charged particle aerodynamics of LEO objects. The 2D aerodynamic interaction of a cylinder with a fixed uniform surface potential of −50 V in mesothermal O+ and H+ plasmas representative of ionospheric conditions is investigated. New insights into the role of bounded ion jets and their effect on surface forces are presented. O+ bounded ion jets are observed to cause a 4.4% increase in direct Charged Particle Drag (dCPD), while H+ ion jets produce a net reduction in H+ dCPD by 23.7% i.e. they cause a thrust force. As a result, this paper concludes the study of charged aerodynamics in LEO requires a self-consistent modelling tool, such as pdFOAM.

Computational aerodynamic study of a supersonic reference projectile

In the present paper results of computational aerodynamic study of a reference projectile in supersonic flow is presented. Pressure distribution along the projectiles nose in longitudinal and circumferential direction was studied using numerical simulations. Static aerodynamic coefficients in the freestream Mach numbers of 3 and 4 at an angle of incidence of -4 to 20 degrees were computed. For validation, the numerical solution was initially compared for the conic part with the experimental results and found to be in good agreement. Nose related aerodynamic features were initially studied in the first part of the study. Further complete projectile’s aerodynamic analysis is carried out. The present paper covers the results obtained in the study conducted for the projectile’s geometry. Significant flow features were investigated, including correct capturing of bow shock’s location, low pressure density/pressure variations in the low pressure regions along with its influence on the stagnation zone. Further evaluation of peak pressure values associated with the stagnation region on the nose was made. Also, static aerodynamic coefficients were computed to depict projectile’s static stability.

An adaptive fully-Lagrangian meshless method for incompressible laminar flow airfoil studies

Laminar incompressible flow around a NACA0012 airfoil placed in a free-stream at various incidences has been revisited with the use of a fully-Lagrangian meshless method based on a Smoothed Particle Hydrodynamics (SPH) formulation. Spatial adaptivity has been incorporated in the scheme via splitting and merging of SPH particles employing zonal criteria. In addition, a novel algorithm has been proposed here so that particle merging may be achieved, ensuring the robustness, accuracy and efficiency of the computational simulations. The results obtained have been benchmarked against available data from mesh-based methods. Good agreement has been found both in steady and unsteady flow regimes. Overall, the present work demonstrated the effectiveness and competitiveness of this meshfree approach for detailed studies in aerodynamics.

A computational study on the influence of insect wing geometry on bee flight mechanics.

ABSTRACTTwo-dimensional computational fluid dynamics (CFD) is applied to better understand the effects of wing cross-sectional morphology on flow field and force production. This study investigates the influence of wing cross-section on insect scale flapping flight performance, for the first time, using a morphologically representative model of a bee (Bombus pensylvanicus) wing. The bee wing cross-section was determined using a micro-computed tomography scanner. The results of the bee wing are compared with flat and elliptical cross-sections, representative of those used in modern literature, to determine the impact of profile variation on aerodynamic performance. The flow field surrounding each cross-section and the resulting forces are resolved using CFD for a flight speed range of 1 to 5 m/s. A significant variation in vortex formation is found when comparing the ellipse and flat plate with the true bee wing. During the upstroke, the bee and approximate wing cross-sections have a much shorter wake structure than the flat plate or ellipse. During the downstroke, the flat plate and elliptical cross-sections generate a single leading edge vortex, while the approximate and bee wings generate numerous, smaller structures that are shed throughout the stroke. Comparing the instantaneous aerodynamic forces on the wing, the ellipse and flat plate sections deviate progressively with velocity from the true bee wing. Based on the present findings, a simplified cross-section of an insect wing can misrepresent the flow field and force production. We present the first aerodynamic study using a true insect wing cross-section and show that the wing corrugation increases the leading edge vortex formation frequency for a given set of kinematics.

Aerodynamic properties of Wind Turbine Towers based on Wind Tunnel Experiments

The presented investigations aim to suggest more realistic models to predict the dynamic behavior of wind turbine structures. Two key issues are addressed: the aerodynamic damping and the cross-wind vibrations.Based on experimental studies in the boundary layer wind tunnel, aerodynamic information for both effects has been obtained. A scaled model of a wind energy tower (1:150) in combination with complementary models have been tested in a test bench designed to carry out HFFB, dynamic wind pressure and forced-oscillation experiments. Reynolds number based scale effects on the tower model have been studied previously.In the predictions of cross-wind vibrations, the length related correlation of vortices shedding from cylindrical structures plays an important role. Therefore, wind dynamic pressures were measured along static tower and cylinder models using pressure taps to determine realistic values of the vortex shedding correlation length.Motion-induced wind vibrations can be significantly influenced by the aerodynamic damping. Using the forced-oscillations method, experiments have been performed under controlled system oscillation with varying wind speed in prism models and tower model. The measured base model forces were correlated with the model motion using spectral methods to obtain the corresponding aerodynamic stiffness and damping coefficients.Both aerodynamic studies will allow more detailed models for the design of new wind tower structures. The acquired information will be applicable in MB-simulations to obtain more realistic and accurate wind turbine performances

Experimental study of canard UAV aerodynamics

The present paper presents the aerodynamic characteristics of a canard fixed-wing unmanned aircraft TERES-02. A wind tunnel experiment is conducted using a specially designed model of the aircraft. The model is produced through the methods of rapid prototyping using a FDM 3D printer. Aerodynamic corrections are made and thorough analysis and discussion of the results is carried out. The obtained results can be used to determine the accuracy of numerical methods for analysis of aircraft performance.

Flow structure diagnostics in a four-vortex furnace model using PIV-method

In this paper the flow structure in a four-vortex furnace of a pulverized coal boiler has been studied. The results of an experimental study of inner aerodynamics carried out on a laboratory isothermal model of a combustion device are presented. Using the particle image velocimetry method, flow velocity distributions have been obtained in a number of sections. A spatial flow structure consisting of four stable conjugate vortices with vertical flow rotation axes has been visualized.

High Humidity Aerodynamic Effects Study on Offshore Wind Turbine Airfoil/Blade Performance through CFD Analysis

Damp air with high humidity combined with foggy, rainy weather, and icing in winter weather often is found to cause turbine performance degradation, and it is more concerned with offshore wind farm development. To address and understand the high humidity effects on wind turbine performance, our study has been conducted with spread sheet analysis on damp air properties investigation for air density and viscosity; then CFD modeling study using Fluent was carried out on airfoil and blade aerodynamic performance effects due to water vapor partial pressure of mixing flow and water condensation around leading edge and trailing edge of airfoil. It is found that the high humidity effects with water vapor mixing flow and water condensation thin film around airfoil may have insignificant effect directly on airfoil/blade performance; however, the indirect effects such as blade contamination and icing due to the water condensation may have significant effects on turbine performance degradation. Also it is that found the foggy weather with microwater droplet (including rainy weather) may cause higher drag that lead to turbine performance degradation. It is found that, at high temperature, the high humidity effect on air density cannot be ignored for annual energy production calculation. The blade contamination and icing phenomenon need to be further investigated in the next study.

Numerical study of aerodynamics and brown coal combustion in the vortex furnace with air excess variation

The results of numerical modelling of 3D turbulent two-phase reacting flow with account for all the principal heat and mass transfer processes during the pulverized brown coal combustion in the vortex furnace of a power plant boiler unit have been presented. For two computational cases where air excess coefficient α was varied (set to 1.15 and 1.25), the detailed aerothermochemical 3D structure of reacting flow in the furnace volume has been revealed. The comparison of integral heat engineering parameters and NOx emissions obtained in the two cases has shown a slightly improved vortex furnace performance in the case α=1.25.

Wind tunnel as a tool in bird migration research

Wind tunnels, in which birds fly against an artificially generated air flow, have since long been used to evaluate aerodynamic properties of steady bird flight. A new generation of wind tunnels has also allowed the many processes associated with migratory flights to be studied in captivity. We review how wind tunnel studies of aerodynamics and migratory performance together have helped advancing our understanding of bird migration. Current migration theory is based on the power‐speed relationship of flight as well as flight range equations, both of which can be evaluated using birds flying in wind tunnels. In addition, and depending on wind tunnel properties, performance during gliding and climbing flight, and effects of air pressure, humidity and turbulence on bird flight has been measured. Long‐distance migrant species have been flown repeatedly for up to 16 h non‐stop, allowing detailed studies of the energy expenditure, fuel composition, protein turnover, water balance, immunocompetence and stress associated with sustained migratory flights. In addition, wind tunnels allow the fuelling periods between migratory flights to be studied from new angles. We end our review by suggesting several important topics for future wind tunnel studies, ranging from on of the key questions remaining, the efficiency at which chemical power in converted to mechanical power, to new useful avenues, such as improving and calibrating the techniques used for tracking of individual birds in the wild.

Experimental and numerical study of the flow field around a small car

This paper presents the aerodynamic study of a small car, which participated in Shell Ecomarathon Europe competition in the Urban Concept Hydrogen class. The goal is to understand the flow field around the vehicle. First, the flow is studied numerically using computational aerodynamics. The numerical simulation is carried out by means of CFD Fluent in order to obtain the drag force experienced by the vehicle and also the flow field. Then the flow field around the car is studied in a wind tunnel by means of particle image velocimetry (PIV). The comparison of the flow fields obtained numerically and experimentally shows good correspondence. The obtained results are very helpful for future car development and permit to improve the drag and to obtain a good stability.

Optimization of a high pressure turbine blade tip cavity with conjugate heat transfer analysis

The current study aims to understand the aero-thermal performance of a cooled cavity tip in a single stage transonic turbine. The squealer tip of the uncooled turbine blade was reduced to an aerodynamic loss with suppressing leakage flow. However, the aerodynamic loss study of the cooled turbine blade tip is rare. It is necessary to study the tip cavity of the cooled turbine blade. Depth, front blend radius and aft blend radius of the cavity were set as design variables, and 30 cases were chosen using design of experiments. These cases were calculated with conjugate heat transfer method. Approximation model was made using the Kriging method, and tip cavity shape was optimized with multidisciplinary design optimization. Average total pressure loss behind the trailing edge and cooling effectiveness of blade tip surface were set to the objective function. The aerodynamic optimization model decreased 1.6 % of total pressure loss, the heat transfer optimization model increased 1.3 % point of cooling effectiveness and aero-thermal optimization model were found. Volume of tip cavity becomes larger when three design variables are grown. Amount of tip leakage flow and its distribution over the tip region increases and total pressure loss and cooling effectiveness increase. In terms of heat transfer, blade tip without cavity is advantageous. Total pressure loss coefficient, however, also increases over 5 %. To improve both aero-thermal characteristics of cooled blade tip, the design using the multidisciplinary design optimization is recommended.

Development and Experimental Verification of Sliding Elements of Transparent Loggia Enclosures in High-Rise Building

Originally open balconies and loggias of high-rise residential building showed a significant aerodynamic load - discomfort for users. Subject of the contract cooperation with the investor was therefore development, experimental verification and optimization of the strength and functional parameters of sliding elements of transparent loggia enclosures from the effect of the dynamically changing wind pressure (pressure - suction), as well as the elimination of undesirable acoustic expressions. This paper introduces the aerodynamic study of the building with the objective of quantifying the maximum load on sliding elements from the effects of wind as the boundary condition for their dimensioning. It describes the final design of transparent sliding elements and their experimental verification in a large pressure chamber in laboratory. The elimination of undesirable acoustic expressions was successfully implemented through design optimization with use of acoustic camera.