Aerodynamic Testing Research Articles

Vehicle aerodynamic simulation analysis and research on bumpy road

PurposeIn order to certify the testing of vehicle Cd on the real road can be replaced by the much simplified steady-state simulation process inside wind tunnel.Design/methodology/approachThe paper opted innovative methods to verify the feasibility of using aerodynamic wind tunnel test for vehicle development purpose, including establishing the typical sinusoidal mapping function for road shapes during vehicle driving process to simplify the complexity of the road and choosing three different kinds of road spectrum amplitudes to establish the vehicle motion model, which can accurately predict the vehicle motion characteristics in the road driving process. The new approach simulates the vehicle aerodynamics on the road by taking into account the pitch angle changes during vehicle motion.FindingsBy comparing the transient drag coefficient on road with the steady-state simulated value in the conventional aerodynamic wind tunnel. This paper provides empirical insights about the flow field analysis around the vehicle on road that can verify the feasibility of using aerodynamic wind tunnel test for vehicle development purpose.Research limitations/implicationsBecause of establishing the typical sinusoidal mapping function for road shapes, the study results may lack generalizability. Therefore, researchers are encouraged to test the proposed propositions further.Practical implicationsThis paper includes implications for the flow field analysis around the vehicle on road that can verify the feasibility of using aerodynamic wind tunnel test for vehicle development purpose.Originality/valueThis paper fulfills an identified need to use aerodynamic wind tunnel test for vehicle development purpose.

High-Precision Digital Image Correlation for Investigation of Fluid-Structure Interactions in a Shock Tube

Background: Structural response measurements are challenging in aerodynamic testing environments due to high-speed requirements, facility vibrations, and the desire for non-intrusive measurements. Objective: This study uses stereo digital image correlation (DIC) to investigate the response of a jointed beam under aerodynamic loading in a shock tube. Methods: The incident shock subjects the beam to an impulsive frontal load followed by periodic transverse loading from vortex shedding. Several considerations necessary to realize high-precision are addressed: first, a hybrid stereo camera calibration accounted for tangential distortions when imaging through thick windows. Second, a measurement bias from Xenon flash-lamp light sources was identified and removed using laser illumination. Third, facility motion was mitigated by vibration isolation and appropriate signal filtering. Finally, aero-optical distortions from turbulence were removed using a low-order reconstruction. Results: The resulting displacement data has a noise floor of approximately ± 1 μm at 20 kHz sampling rate. The reduction of primary noise sources allows a transient structural response on the order of 10–40 μm to be quantified. The highest vibrations occurred when the vortex shedding frequency matched the beam’s natural frequency. Conclusion: the noise reduction techniques described allow for structural measurements requiring high-precision, non-intrusive displacement data to be performed in aerodynamic environments.

Analysis of drag and lift forces for a sedan car using a rear lip spoiler

In this research, aerodynamic tests were carried out using Solidworks Flow Simulation software on a Sedan-type car, implementing different sizes of lip-type spoilers at the rear to obtain the results of the drag and lift coefficients produced by movement. of the air regardless of the design at the rear of the car and analyze if there was improvement in aerodynamics. Analyzing the results, it is obtained that the aerodynamics of the car is improved when a lip-type spoiler is fitted, the lift forces were reduced, whereas the drag forces remained constant for all the different designs.

Perturbation Analysis and Control of Mach Number 2.4-Meter Transonic Wind Tunnel

Because of the large domestic civil aircraft projects started in China a decade ago, there is a greater need to control the accuracy of the Mach number in aerodynamic tests, especially near the designed cruise point of large commercial aircraft. Nowadays the control accuracy of China Aerodynamics Research and Development Center 2.4-meter transonic wind tunnel Mach number is in the range of to when , which is far from the measurement accuracy of drag coefficient required for testing advanced aircraft. This value should result in a better-than-one drag count. As a consequence, it is imperative to improve the control accuracy of Mach number urgently. The nonlinearity, large time delays, and strong coupling of wind tunnel flowfield control, along with the variation of the model angle of attack, could cause the Mach number to deviate from the expected value. To solve these problems, a model predictive control method based on dynamic matrix control algorithm is proposed. This method builds a prediction model based on step response test. The accuracy of Mach number predictive control can be efficiently improved by performance optimization in the form of vector norms, rolling optimization, and feed-forward compensation. This control strategy has been successfully tested in the wind tunnel, and the control accuracy of Mach number has been remarkably enhanced, to the point where it can be controlled to within . This value satisfies the requirements of aerodynamic aircraft testing.

Modeling And Simulating The Design of Air Defense Missile Aerodynamic Systems

This paper is an academic study that discusses how to design air defense missile modeling and simulation, as a missile development strategy for the Indonesian National Army. Aerodynamic is the most important part of missile development, which regulates lift, drag, thrust and other parts that interact directly with air. The success of developing a rocket that has reached level 7 technology mastery readiness (Prototype Tested), can be a starting point to seriously initiate the development of Indonesian Missiles. The initial design process was based on the specifications of the 122 mm caliber defense rocket, the length of 2810 mm, the weight of the 60.8 kg rocket and the 15 kg warhead with an overall range of 30.5 km that would be adjusted to the initial configuration of the air defense missile. Aerodynamic testing will be carried out on Solid Work, Ansys and Missile Datcom software which will be compared with the results of each other. This development strategy can optimize the rocket products that have been successfully developed by Indonesia, because the sustainability of the rocket mastery will be very useful to be used as a basis for missile development, specifically in terminal air defense missiles, which is the weak point of Indonesia’s air defense today.

Aerodynamic testing of rotors and propellers for small unmanned aerial vehicles at Technical University - Sofia

The recent massive introduction of small unmanned aerial vehicles (UAVs) brought the problem of absence of reliable aerodynamic data and models for propulsion systems that work at low Reynolds numbers. At the same time the new capabilities of modern measuring equipment permit detailed experimental investigations of the aerodynamic characteristics of such systems. This paper presents the results of work in this direction, carried out at, or with serious contribution of the Department of Aeronautics at Technical University of Sofia. Two test benches are presented. The first one is for static testing of small helicopter rotors. It is designed also with provisions for installation in suitable wind tunnels. The second one is a test stand for evaluation of electric power plants for unmanned aircraft vehicles. It can be used statically, or may be installed on the roof of an automobile for mobile testing. As an illustration experimental results are given for a specific model helicopter rotor and a small airplane propeller.

Combined Numerical and Experimental Investigations into the Local Fluid Dynamics of Coolant Flow in the Mixed Core of a VVER Reactor

The article presents the results from experimental investigations into local coolant flow fluid dynamics that were carried out on the fragmental model of a VVER-type pressurized water reactor’s mixed core consisting of two types of fuel assemblies (FAs): TVSA-T (one segment) and TVSA-T.mod.2 (two segments). The coolant flow processes in the fuel rod bundle were simulated on an aerodynamic test bench. The pressure field in the flow was measured using a five-channel pneumometric probe. The obtained pressure field in the flow was recalculated for the coolant velocity vector according to the dependences derived during calibration. For drawing up a detailed flow motion pattern, a characteristic model cross section area was separated, which included the space between the assemblies and four fuel rod rows in each TVSA-type fuel assembly. The spatial distribution of coolant flow velocity projections was analyzed, as a result of which it became possible to reveal the regularities associated with the streamlining of spacer-, mixing-, and combined-spacer grids in TVSA assemblies by coolant; to determine coolant cross flows resulting from streamlining of hydraulically nonidentical grids and determine their localization in the experimental model longitudinal and cross sections; and to reveal the effect of accumulating flow hydrodynamic disturbances in the model longitudinal and cross sections resulting from the staggered arrangement of hydraulically nonidentical grids. The results obtained from investigations of inter-assembly interaction of coolant between the neighboring TVSA-T and TVSA-T.mod.2 assemblies have been adopted for practical use at AO Afrikantov OKBM in estimating the thermal reliability of VVER-type reactor cores and have been included in the database for verification of computation fluid dynamics computer programs (CFD codes) and detailed cell-wise numerical analysis of the core of VVER reactors.

Quantifying uncertain system outputs via the multilevel Monte Carlo method — Part I: Central moment estimation

In this work we introduce and analyze a novel multilevel Monte Carlo (MLMC) estimator for the accurate approximation of central moments of system outputs affected by uncertainties. Central moments play a central role in many disciplines to characterize a random system output's distribution and are of primary importance in many prediction, optimization, and decision making processes under uncertainties. We detail how to effectively tune the MLMC algorithm for central moments of any order and present a complete practical algorithm that is implemented as part of a Python library [1]. In fact, we validate the methodology on selected reference problems and apply it to an aerodynamic relevant test case, namely the transonic RAE 2822 airfoil affected by operating and geometric uncertainties.

On theory and methods for advanced detonation-driven hypervelocity shock tunnels.

This study describes theory and methods for developing detonation-driven shock tunnels in hypervelocity test facilities. The primary concept and equations for high-enthalpy shock tunnels are presented first to demonstrate the unique advantage of shock tubes for aerodynamic ground-based testing. Then, the difficulties in simulating flight conditions in hypervelocity shock tunnels are identified, and discussed in detail to address critical issues underlying these difficulties. Theory and methods for developing detonation drivers are proposed, and relevant progress that has advanced the state of the art in large-scale hypersonic test facilities is presented with experimental verifications. Finally, tailored conditions for detonation-driven shock tunnels are described, laying a solid foundation to achieve long test duration. This interface-matching key issue encountered in developing shock tunnels has been investigated for decades, but not solved for detonation drivers in engineering applications.

Aerodynamic and hydroaerothermic tests of cooling tower sprinkler

Industrial water supply systems are designed to supply water to production in the required quantities and of the appropriate quality. They consist of a complex of interconnected structures - water intake devices, pumping stations, installations for cleaning and improving water quality, control and spare tanks, water coolers and a distribution network of pipelines. Depending on the purpose and local conditions, some of the listed structures may not be available in the system. The temperature regime of any production is carried out using recycled water systems, most often equipped with fan and tower cooling towers. The main element of all types of cooling towers, affecting the efficiency of the interaction of the droplet liquid with the ascending air flow and, accordingly, the efficiency of the cooling towers, is the sprinkler. This article describes the design of the polymer drip-film sprinkler of cooling towers, and also presents the results of aerodynamic and hydroaerothermic studies of this nozzle design.

Análisis aerodinámico en CFD de los alerones en automóviles convencionales

In the present study aerodynamic tests were performed by using Solidworks Flow Simulation software (CFD) in 2 different designs of conventional cars, implementing a spoiler in the back of the car to reduce the drag and lift coefficients that occur through the movement of the air regardless of the design in the back of the car and improve aerodynamics. Analyzing the results it is obtained that the aerodynamics of the car is improved when a spoiler is placed to reduce the drag and lift forces.

Investigation of Coolant Local Hydrodynamics in the Mixed Core of the VVER Reactor

The article presents the results of experimental studies of the local hydrodynamics of the coolant flow in the mixed core of the VVER reactor, consisting of the TVSA-T and TVSA-T mod.2 fuel assemblies. Modeling of the flow of the coolant flow in the fuel rod bundle was carried out on an aerodynamic test stand. The research was carried out on a model of a fragment of a mixed core of a VVER reactor consisting of one TVSA-T segment and two segments of the TVSA-T.mod2. The flow pressure fields were measured with a five-channel pneumometric probe. The flow pressure field was converted to the direction and value of the coolant velocity vector according to the dependencies obtained during calibration. To obtain a detailed data of the flow, a characteristic cross-section area of the model was selected, including the space cross flow between fuel assemblies and four rows of fuel rods of each of the TVSA fuel assemblies. In the framework of this study the analysis of the spatial distribution of the projections of the velocity of the coolant flow was fulfilled that has made it possible to pinpoint regularities that are intrinsic to the coolant flowing around spacing, mixing and combined spacing grates of the TVSA. Also, the values of the transverse flow of the coolant caused by the flow along hydraulically nonidentical grates were determined and their localization in the longitudinal and cross sections of the experimental model was revealed. Besides, the effect of accumulation of hydrodynamic flow disturbances in the longitudinal and cross sections of the model caused by the staggered arrangement of hydraulically non-identical grates was determined. The results of the study of the coolant cross flow between fuel assemblies interaction, i.e. between the adjacent TVSA-T and TVSA-T mod.2 fuel assemblies were adopted for practical use in the JSC of “Afrikantov OKB Mechanical Engineering” for assessing the heat engineering reliability of VVER reactor cores; also, they were included in the database for verification of computational hydrodynamics programs (CFD codes) and for detailed cell-based calculation of the reactor core.

Experimental and numerical investigations on effect of blade trimming on aerodynamic performance of squirrel cage fan

The impeller of squirrel cage fan exerts great effects on the internal flow fields and fan aerodynamic performance. On the premise of maintained impeller-volute tongue distance and production cost reduction, this paper proposes a blade trimming method focusing on axial modification of blade inlet in an attempt to improve the impeller flow condition and further the aerodynamic performance of squirrel cage fan, which is divided into blade full trimming and part trimming. Aerodynamic performance tests and numerical simulations are performed to explore the effect of blade trimming on the fan aerodynamic performance and the related flow mechanisms. The results show that the blade trimming with proper trimming parameter enables the fan to achieve higher fan aerodynamic performance in terms of total pressure efficiency and static pressure rise, between which full trimming is preferable to part trimming. With the optimum full trimming of blade, the axial distributions of mass flow at the impeller inlet and outlet become more uniform. The dimension of inactive zone near the front span is decreased. On the blade pressure surface, the forces are reduced with obvious improvement of gradients near the front span and back span. A better match between impeller and volute tongue is achieved as the decreases of reversed flow coefficients at the impeller inlet and outlet and recirculated flow coefficient in the volute.

A Comprehensive Understanding of Airflow in Non Air conditioned Bus Coaching System

Bus is a Major mode of transport in India and the passenger safety is significant during the travel. This Comprehensive comprehension on the literatures available discusses various parameters used to improve the Vehicle Design, Safety, Fuel Efficiency and decrease in drag of the vehicle. The outcomes obtained from CFD investigation is tabulated, and the exploratory outcomes obtained from aerodynamic tests are contrasted and numerical examination and the outcomes are additionally incorporated. The impact of temperature and the wind stream is likewise considered in this investigation. Various kinds of ventilations given in the transport vehicles are recorded, and the outcomes acquired from the various configurations in the structure is considered for opening and closing of Windows (Combination of windows). The cooling air inside the transport straightforwardly relies upon the outside climate condition. By overhauling the current vehicle transport model, the eco-friendliness will be improved and the drag power will be diminished.

Ultrasensitive all-fiber inline Fabry–Perot strain sensors for aerodynamic measurements in hypersonic flows

This work proposes an ultrasensitive, temperature-insensitive, all-fiber inline Fabry–Perot (FP) strain sensor for aerodynamic coefficients measurements of a hypervelocity ballistic correlation model 2 in a Φ1 hypersonic wind tunnel. The FP sensors fabricated using 157 nm laser micromachining system are structurally simple, small-sized, and high-temperature resistance. 16 FP sensors are installed on a six-force balance, which is mounted inside the model, to sense the aerodynamic forces and moments of the model, and then the model’s aerodynamic coefficients are calculated based on aerodynamic theory according to the test data. A new temperature-compensated method is proposed to improve measurement accuracy of aerodynamic coefficients via eliminating temperature-induced measurement errors. Experimental results show, at high temperatures, the FP sensors based on the balance (FP balance) exhibits a high-repeatability precision of the aerodynamic coefficients measurement of less than 1%, and match well with the results of the traditional method using foil-resistive strain sensors. This enhanced-sensitivity FP sensor is currently the most promising alternative to foil-resistive strain sensors for aerodynamic tests among kinds of fiber-optic strain sensors to the best of our knowledge. The FP balance satisfies the requirements of practical application of aerodynamic characteristic tests, and opens up another test system of the field.

Experimental Assessment of Wind Loads on Roof-to-Wall Connections for Residential Buildings

Wind hazards are one of the most disastrous events that frequently occur in the United States. Hurricane Irma, which hit the southeast coast in 2017, left a majority of damage concentrated on low-rise buildings and wooden construction in its wake. As revealed by recent hurricane damage reconnaissance, hardware-type roof-to-wall connections are especially vulnerable to high wind suction. There is only limited research on the assessment of wind loads on these roof-to-wall connections, which are important components of the wind load path. Hence, it is essential to have realistic estimates of wind effects on these connections to ensure a safe design. To fill this fundamental knowledge gap, an extensive large-scale aerodynamic testing study has been recently conducted at the NSF-Natural Hazard Engineering Research Infrastructure (NHERI) Wall of Wind (WOW) Experimental Facility (EF) to investigate wind actions resulting from simulated hurricane force winds. A wooden gable roof building of a large length scale of 1:4 was adopted for this study. Seven trusses were used to construct the roof and were connected to the top plate of the side walls. Load cells were mounted at the roof-to-wall connection (RTWC) level to measure the effective net wind-induced forces. The model was tested under different wind directions varying from 0° to 360° with an increment of 5° under varying wind speeds. In addition, three different configurations, i.e., one enclosed and two partially enclosed, were considered to assess different internal pressure scenarios that affect the net load-ing on the roof-to-wall connections and the overall roof system. The RTWC force coefficients distribution along the entire roof was obtained. The results were compared to force coefficients recommended by ASCE 7-16 version for the cases of Main Wind-Force Resisting System (MWFRS) and Component and Cladding (C&C). The experimental results were in between MWFRS and C&C values based on the ASCE provisions in general. However, for partially enclosed case, some values slightly exceeded those based on the ASCE C&C provisions. Also, the overall uplift on the roof was found to be dependent on the location of the opening (i.e., opening on long side versus short side of the building).

Low speed lateral-directional aerodynamic and static stability analysis of a hypersonic waverider

Hypersonic waveriders have the potential to significantly reduce travel times on long haul civilian transport routes. The design of hypersonic aircraft is heavily influenced by the aerodynamic efficiency at the cruise Mach number, resulting in less than ideal geometries for subsonic flight. Waverider aerodynamics and stability in the low speed regime is rarely investigated and not well understood, but is crucial for horizontal take-offs and landings. This paper presents a combination of numerical simulation results and experimental data for the low speed propelled variant of the Mach 8 HEXAFLY-INT waverider. Aerodynamic, control and stability testing for lateral-directional cases was conducted in the University of Sydney 4 foot by 3 foot low speed facility. Computational fluid dynamics simulations are compared with wind tunnel tests for angles of attack between -5 and 15 degrees and angles of sideslip between -8 and 8 degrees. Throughout these ranges, aileron and rudder deflections up to 10 degrees are investigated. Results show that the vehicle aerodynamics are dominated by asymmetric wing and fin vortices, resulting in non-linear aerodynamic forces. At a centre of gravity location of 44.4% of the vehicle length the aircraft is stable directionally, but has lateral instability at angles of attack below -2 degrees. This is attributed to the low mounted wings with anhedral. The instability is minor and is not expected to result in an uncontrollable condition. Lowering the centre of gravity by approximately 2 centimetres, or 17% of the local fuselage height, can correct the instability. Lateral-directional dynamic stability was predicted using static derivatives and was found to be stable through the entire AoA range tested, with no dependence on mass moments of inertia. Both aileron and rudder controls are found to provide sufficient control authority, but the aircraft may benefit from increased rudder size. The results from this study, along with previous work on longitudinal stability and performance show the feasibility of moving to the flight test program, but aircraft dynamic stability must first be investigated.

Is "Slow Inhalation" Always Suitable for Pressurized Metered Dose Inhaler?

To achieve adequate inhalation therapy, a proper inhalation technique is needed in clinical practice. However, there is limited information on proper inhalation flow patterns of commercial inhalers. Here, we quantitatively estimated airway deposition of two commercial pressurized metered dose inhalers (pMDIs) to determine their optimal inhalation patterns. Sultanol® inhaler (drug particles suspended in a propellant, suspension-pMDI) and QVAR™ (drug dissolved in a propellant with ethanol, solution-pMDI) were used as model pMDIs. Aerodynamic properties of the two pMDIs were determined using an Andersen cascade impactor with human inhalation flow simulator developed by our laboratory. As indices of peripheral-airway drug deposition, fine particle fractions (FPFPA) at different inhalation flow rates were calculated. The time-dependent particle diameters of sprayed drug particles were determined by laser diffraction. On aerodynamic testing, FPFPA of suspension-pMDI significantly decreased depending on the increasing inhalation flow rate, while solution-pMDI achieved higher and constant FPFPA in the range of the tested inhalation flow rates. The particle diameter of solution-pMDI markedly decreased from 5 to 3μm in a time-dependent manner. Conversely, that of suspension-pMDI remained at 4μm during the spraying time. Although "slow inhalation" is recommended for pMDIs, airway drug deposition via solution-pMDI (extra-fine particles) is independent of patients' inhalation flow pattern. Clinical studies should be performed to validate instruction for use of pMDIs for each inhaler for the optimization of inhalation therapy.

Setting up the mathematical model of gas fuel combustion taking into account computational domain geometry refinement

The problem of gaseous fuel combustion in a land-used gas turbine engine combustion chamber was formulated, and the results of the numerical solution were described. The paper assumes that the gas-air mixture is a single-phase, multicomponent and reactive flow. The Reynolds averaging approach to the Navier-Stokes equations was used to describe the turbulent flow in the combustion chamber. The SST model of turbulence was used to close the averaged system .A combined EDM/FRC combustion model was used to determine the rate of formation of mixture components. A technique was proposed for setting up the mathematical model taking into account three parameters: the turbulent Prandtl and Schmidt numbers and the coefficient limiting the burning rate. Based on a comparison of the results of preliminary calculations and experiments, it was suggested that the difference in these data is due to technological deviations and the application of a heat-protective coating to the walls of the flame tube. The geometry of the computational domain was changed based on the airflow coefficient obtained in the aerodynamic tests. The setting up of the mathematical model was carried out both on the initial and on the refined geometry. The verification of the mathematical model was carried out using the results of experiments on three structural variants of the flame tube. The results of calculations carried out with the use of refined data showed that a change in geometry made it possible to more correctly describe combustion in a turbulent flow: the theoretical results on the average non-uniformity obtained on the refined geometry of the studied region practically coincide with the experimental data. Due to updating the geometry of the computational domain, it was possible to establish the location and magnitude of the maximum non-uniformity. Using the results obtained in this work, a mathematical model was developed to describe the combustion of gaseous fuel in the combustion chamber of a gas turbine engine. The proposed model can be used to further optimize the design of the combustion chamber.

A Novel Fast-moving Device Driven by Hydraulic System for Aerodynamic Heating Tests

In order to avoid the measurement error brought by heating before aerodynamic heating tests in a hypersonic wind tunnel, it’s essential that the testing model should be insert into the flow field quickly. This paper presents a novel fast-moving device driven by a hydraulic system which was based on gas-liquid boosting cylinder and servo proportional valve. The control system of the fast-moving device has adopted IPC centralized-control, electro-hydraulic servo, AC servo and industrial field bus technologies, so mutual independent multiple freedom motion control circuits have been built. By using the high-speed data acquisition and analog output, reading CPU work frequency etc., the control system has solved the difficult question of fast insertion and timing. A series of experimental results show the device satisfies the speed and impact requirements, which can move the testing model into the flow field quickly during aerodynamic heating tests and operate stably.