Aerodynamic Testing Research Articles

Three-Dimensional Ice-Accretion Measurement Methodology for Experimental Aerodynamic Simulation

Determining the adverse aerodynamic effects due to ice accretion often relies on dry-air wind-tunnel testing of artificial, or simulated, ice shapes. Recent developments in ice-accretion documentation methods have yielded a laser-scanning capability that can measure highly three-dimensional features of ice accreted in icing wind tunnels. The objective of the current study was to evaluate the aerodynamic accuracy of ice-accretion simulations generated from laser-scan data. Tests were conducted in the NASA Glenn Icing Research Tunnel, where ice accretions were measured with laser scanning before the molding process. Aerodynamic performance testing was conducted at the University of Illinois low-speed wind tunnel at a Reynolds number of and a Mach number of 0.18 with an airfoil model designed to accommodate artificial ice shapes. The ice-accretion molds were used to fabricate one set of artificial ice shapes from polyurethane castings. The laser-scan data were used to fabricate another set of artificial ice shapes using rapid-prototype manufacturing. The iced-airfoil results with both sets of artificial ice shapes were compared to evaluate the aerodynamic simulation accuracy. The data showed that the laser-scan and rapid-prototype manufacturing approach was capable of replicating small ice features within the reported accuracies of the laser-scan measurement and rapid-prototyping methods, thus providing a new capability for high-fidelity ice-accretion documentation and artificial ice-shape fabrication for icing research.

Open-jet boundary-layer processes for aerodynamic testing of low-rise buildings

Investigations on simulated near-surface atmospheric boundary layer (ABL) in an open-jet facility are carried out by conducting experimental tests on small-scale models of low-rise buildings. The objectives of the current study are: (1) to determine the optimal location of test buildings from the exit of the open-jet facility, and (2) to investigate the scale effect on the aerodynamic pressure characteristics. Based on the results, the newly built open-jet facility is well capable of producing mean wind speed and turbulence profiles representing open-terrain conditions. The results show that the proximity of the test model to the open-jet governs the length of the separation bubble as well as the peak roof pressures. However, test models placed at a horizontal distance of 2.5H (H is height of the wind field) from the exit of the open-jet, with a width that is half the width of the wind field and a length of 1H, have consistent mean and peak pressure coefficients when compared with available results from wind tunnel testing. In addition, testing models with as large as 16% blockage ratio is feasible within the open-jet facility. This reveals the importance of open-jet facilities as a robust tool to alleviate the scale restrictions involved in physical investigations of flow pattern around civil engineering structures. The results and findings of this study are useful for putting forward recommendations and guidelines for testing protocols at open-jet facilities, eventually helping the progress of enhanced standard provisions on the design of low-rise buildings for wind.

Flow and Turbulence Control in a Boundary Layer Wind Tunnel Using Passive Hardware Devices

The Climatic Wind Tunnel (CWT) is a new experimental facility of the Institute of Theoretical and Applied Mechanics (ITAM) in Prague, Czech Republic. It is uniquely able to replicate precipitation and freezing effects on structural models in the climatic test section, and simultaneously perform aerodynamic and aeroelastic tests on structural models in the aerodynamic test section. Extensive measurements are carried out to investigate airflow and turbulence characteristics in the empty aerodynamic test section. Capability to experimentally simulate the atmospheric boundary layer (ABL) is studied using castellated barrier wall, Counihan vortex generators, and surface roughness elements. An individual influence of each of these passive hardware devices is separately tested as well, as they are commonly used combined, and their individual contributions to the ABL model characteristics are not well known. The analysis is based on hot-wire anemometer measurements carried out at various cross sections in the aerodynamic test section of the CWT. Experimental results are reported as mean velocity and turbulence intensity fields for the empty aerodynamic test section without passive hardware devices. Vertical profiles of mean velocity, turbulence intensity, and turbulence length scales, as well as power spectral density of velocity fluctuations, are reported for the ABL small-scale model. The barrier is observed to cause a decrease in flow velocity and an increase in turbulence close to surface. Vortex generators enhance turbulence throughout the entire height range under scope. Increased turbulence and decreased flow velocity are particularly exhibited close to surface due to surface roughness. Influence of each of the studied passive hardware devices on flow and turbulence is quantified in a dimensionless form to allow for separately accounting for their effects.

A century of wind tunnels since Eiffel

Fly higher, faster, preserve the life of test pilots and passengers, many challenges faced by man since the dawn of the twentieth century, with aviation pioneers. Contemporary of the first aerial exploits, wind tunnels, artificially recreating conditions encountered during the flight, have powerfully contributed to the progress of aeronautics.But the use of wind tunnels is not limited to aviation. The research for better performance, coupled with concern for energy saving, encourages manufacturers of ground vehicles to perform aerodynamic tests. Buildings and bridge structures are also concerned.This article deals principally with the wind tunnels built at ONERA during the last century. Somme wind tunnels outside ONERA, even outside France, are also evocated when their characteristics do not exist at ONERA.

Aerodynamic Testing of Helicopter Side Intake Retrofit Modifications

Aerodynamic characteristics of helicopter engine side air intakes are investigated. The experimental data set is obtained by wind tunnel testing of a full-scale helicopter fuselage section model. For the simulation of realistic engine operation, engine mass flow rates are reproduced. Five-hole pressure probe data of the aerodynamic interface plane as well as local surface pressure distributions are compared for different geometries and operation conditions. Previous investigations indicate that unshielded, sideways-facing air intakes yield lowest distortion and highest total pressure levels in low speed conditions. In fast forward flight condition, however, forward-facing intake shapes are more beneficial. On this basis, the current research assesses the optimization potential of retrofit modifications such as a rear spoiler (small scoop) and an intake guide vane. Two optimal configurations of retrofit modifications are identified, combining benefits of the various basic intake and plenum chamber shapes.

Experimental investigation on overall performance of a millimeter-scale radial turbine for micro gas turbine

As a major component and work unit of micro gas turbine, the performance of micro turbine directly determines the realizability of micro gas turbine. In order to explore the feasibility, to obtain the performance, and to verify the design results of a micro radial turbine, this paper mainly presents the investigation on overall performance of a micro radial turbine with 10 mm diameter for 50W-class micro gas turbine by the cold model test. Firstly, the aerodynamic performance test platform for high speed micro radial turbine was exhibited. Then, the feasibility and overall performance test of micro radial turbine was carried out. At present, the rotational speed of micro radial turbine has achieved at 359,900 rpm by using hydrostatic gas bearing, which is approximately 80% rotational speed of the design point in cold model test. Thirdly, based on the experimental data and numerical simulation, the operating performance and overall performance of the micro gas turbine were analyzed and discussed in details. The final results indicate that the feasibility of the millimeter-scale micro radial turbine with 10 mm diameter has partly been proven at present level and the micro radial turbine system need to be further improved. These works not only obtain the some valuable experimental data, but also accumulate experience of micro radial turbine design. And this paper not only exhibits the test and design results as engineering reference, but also presents the operation problems and its potential solutions of ultra-high rotational speed experiment and performance test of a micro radial turbine.

Effects of the inner‐secondary‐air damper opening on flow and combustion in a 600‐MWe down‐fired boiler incorporating multiple‐injection and multiple‐staging

AbstractEffects of adjusting the inner‐secondary‐air damper opening among 100%, 70%, and 50% on the flow, combustion, and NOx emissions of a 600‐MWe down‐fired boiler incorporating multiple‐injection and multiple‐staging technology were investigated. Both 1 : 20‐scale aerodynamic tests and industrial experiments were conducted. The small‐scale tests showed that symmetric flow patterns formed in all cases, and the velocities of boundary and outer secondary air decayed more quickly than the velocity of inner secondary air. As the inner‐secondary‐air damper opening decreased from 100% to 50%, the average dimensionless depth of downward airflow reduced from 0.830 to 0.788 while the horizontal velocity in the recirculation zone increased. Industrial experiments demonstrated that, as the inner‐secondary‐air damper opening decreased from 100% to 50%, the heating rate of fuel‐rich coal/air flow increased from 572 to 687°C/m, the corresponding ignition distance shortened from 1.36 to 1.11 m, and the hopper near‐wall temperature decreased by approximately 50°C. Carbon in fly ash decreased from 7.31% to 6.93%, and NOx emissions rose from 343 to 371 ppm at 6% O2. The boiler efficiency improved from 89.78% to 89.92%. An inner‐secondary‐air damper opening of 70% is more reasonable than 50% and 100% considering the ignition distance, carbon in fly ash, and NOx emissions. Copyright © 2017 Curtin University of Technology and John Wiley & Sons, Ltd.

Effects of tertiary air damper opening on flow, combustion and hopper near-wall temperature of a 600 MWe down-fired boiler with improved multiple-injection multiple-staging technology

In consideration of increasing the tertiary air damper opening of a 600 MWe down-fired boiler with prior multiple-injection multiple-staging technology facilitated the coal burnout, while largely increasing the NOx emissions. Additionally, the flame kernel was greatly moved downwards, thus causing significant temperature variations in the hopper near-wall region and the water wall in the lower furnace was vulnerable to overheating. This work concentrated on the comprehensively improved multiple-injection multiple-staging technology, both 1:20 scale cold aerodynamic tests and industrial experiments were conducted to examine the effects of tertiary air damper opening on flow, combustion, NOx emissions and especially the hopper near-wall temperatures. The aerodynamic tests indicated that, on increasing the tertiary air damper opening from 40 to 70%, all the flow fields exhibit good symmetry. The tertiary air flows downwards along the hopper near-wall region, with a maximum near-wall dimensionless vertical velocity significantly increasing from 0.48 to 0.66, and accordingly, the dimensionless depth of downward airflow increases from 0.744 to 0.846. The industrial experimental results showed that, upon introducing more tertiary air, the ignition distance of fuel-rich coal/air flow shortens from 1.25 to 0.87 m. The coal burnout is enhanced, carbon in fly ash drops from 6.90 to 6.15%, while the NOx emissions slightly increase from 593 to 641 mg/m3 at 6% O2. On reducing the measuring height of hopper near-wall temperature from 9.1 to 3.3 m, the average heating rate increases from 0.44 to 0.63 °C/mm. The increased tertiary air damper opening presents an increasingly obvious cooling effect on the hopper near-wall region, with the temperature reductions around 50 °C, which is conductive to protect the water wall in the lower furnace from overheating.

An enhanced forced vibration rig for wind tunnel testing of bridge deck section models in arbitrary motion

This paper presents a new experimental setup for the aerodynamic section model testing of bridge decks. The rig is designed to move a section model in arbitrary motion in a wind tunnel to imitate the motions of such scaled real bridge motion, step motion or random motion histories to be close to white noise. The proposed setup enables the forces acting on the section model to be measured directly while considering motions that resemble actual bridge motion and still fully utilizing the benefits of the forced vibration testing technique. The excellent performance of the system and testing procedure is proved by performing state-of-the-art forced vibration tests to extract 18 flutter derivatives of the Hardanger Bridge cross-section. The new experimental setup is further used to simulate a three-degree-of-freedom dynamic system driven by white noise to investigate whether the estimates of the aerodynamic derivatives are sensitive to the motion considered. The experimental results demonstrate that the estimates of the aerodynamic derivatives are not sensitive to the motion considered; these results indicate that the principle of superposition is fully applicable for the cross section as long as the motions are within the range considered.

Supporting system interference on aerodynamic characteristics of an aircraft model in a low-speed wind tunnel

Many kinds of support system, such as tail support system, external/balance support system, side wall support system and wing tip support system are used for wind tunnel testing. The difference between the flow around the test model and the flow around the real aircraft is caused by the support system and results in a difference between aerodynamic characteristics of the test article and the actual one and is referred to as support interference. Support interference is one of the important topics of aerodynamic testing since it can have significant influence on the accuracy of the test data. The support system and support interference become one of the main investigation areas of experiment aerodynamics. The results of experimental investigation of the influence of model support on the determination of aerodynamic coefficients of a wind tunnel model are presented. A discussion is given of the forms of interference occurring in the low speed wind tunnel of the Military Technical Institute due to the model support system. Two types of model attachments, bent sting and external/balance model support are considered. The magnitude of interference on the test results is given. The main interference is on the pitching moment coefficient Cm. The computational results of the interference-free aerodynamic coefficients of a Training Aircraft Model are also given and compared to experimental data. A procedure for eliminating the undesired effect of interference of the model support system on the test results is presented.

Investigation and Analysis on Racing Car Front Wings

A great number of studies have been done on aerodynamic test for the racing car. Due to critical competition among the racing car teams, the results of the studies will only been published when they are obsolete. This study was conducted by using the Computational Fluid Dynamics (CFD) utilising SolidWorksTM to perform simulations about the airflow on the front and rear wings of a racing car with different angles of attack. The analysis generates the theoretical Lift force, Down force, and Drag force for a racing car wing. Consequently, at higher velocity, the down force and interrelated induced drag increases. The maximum speed on a straight part is thus reduced due to the increase in induced drag. Finally, tests from the C15 wind tunnel also show similar trends to those derived from the simulations. Compared with results of Model geometry and wind tunnel tested, it is shown that an angle between -10° and -20° below the horizontal indicates the stalling conditions.

A new method for aerodynamic test of high altitude propellers

A ground test system is designed for aerodynamic performance tests of high altitude propellers. The system is consisted of stable power supply, servo motors, two-component balance constructed by tension-compression sensors, ultrasonic anemometer, data acquisition module. It is loaded on a truck to simulate propellers’ wind-tunnel test for different wind velocities at low density circumstance. The graphical programming language LABVIEW for developing virtual instrument is used to realize the test system control and data acquisition. Aerodynamic performance test of a propeller with 6.8m diameter was completed by using this system. The results verify the feasibility of the ground test method.

Aerodynamic analysis of an active rear split spoiler for improving lateral stability of high-speed vehicles

This paper examines an active rear split spoiler designed for improving lateral stability of high-speed vehicles under high lateral acceleration (high-g) scenarios, such as a tight cornering manoeuvre at high speeds. Downforces produced by the spoiler can enhance the lateral stability of the vehicle under a high-g cornering manoeuvre. On the other hand, the spoiler may introduce additional drags on the vehicle. Aerodynamic analysis and wind tunnel testing are conducted to evaluate the dynamic effects of the active spoiler on a high-speed car. The downforce and drag, as well as their relationship, are investigated using CFD simulations of the car with the active rear split spoiler at different spoiler angles of attack and at different speeds. Then, the achieved CFD simulation results are compared with the experimental data derived from the wind tunnel on the physical car and the spoiler prototype. The observations and findings achieved from the study may provide valuable guidelines for developing active aerodynamic control systems to increase safety of high-speed vehicles.

Сравнительный анализ аэродинамических характеристик центробежных пылеуловителей при проведении параллельных сравнительных испытаний

Introduction. The article is devoted to investigations on the “Cyclone” semi-industrial pilot plant which allows for parallel comparative aerodynamic testing of the cylindrical cyclone with “TsN-15u-300” volute and the patented cyclone with the “CSC-200-300” inverted cone. The work objective is to obtain experimentally major aerodynamic characteristics of the centrifugal dust collectors of various shapes without bunkers under the parallel comparative testing with the subsequent analysis of the results. Improving the efficiency, increasing the productivity while reducing the energy consumption for ventilation systems and metal consumption for centrifugal dust collectors, are crucial technological tasks. Materials and Methods . Parallel comparative aerodynamic testing of centrifugal dust collectors of various shapes for the cylindrical cyclone with “TsN-15u-300” volute and the patented cyclone with the “CSC-200-300” inverted cone is conducted. At this, Pitot tubes and two high-precision Testo -521 differential pressure gauges are used. Mathematical calculations of the hydraulic resistance coefficients for the investigated devices are made. Research Results. As a result of the experiments, the behavior of the total pressures and air velocity at various gage points of the inlet and outlet nozzle sections of the cyclone apparatus at different capacities of the fan exhauster is specified. The calculated hydraulic resistance coefficients (HRC) of the “CSC-200-300” device appear 2-2.2 times lower than HRC of “TsN-15u-300” due to the higher flow velocity in the device body. This indicates its best aerodynamics and possibly higher efficiency of the dust collection due to the high flow turbulence. Discussion and Conclusions . The obtained aerodynamic characteristics are used in operation to assess the effectiveness and economic benefits of the cyclone apparatus. Further experimental studies on the pilot plant are needed to verify the conclusions.

Factors affecting the downward flame depth in a 600 MW down-fired boiler incorporating multiple-injection and multiple-staging technology

Considering the excessively deep flame depth existing in a 600 MW down-fired boiler incorporating multiple-injection and multiple-staging technology, 1:20 scale aerodynamic tests were conducted to incrementally improve factors responsible for the deep flame depth. These trials demonstrated that, in all cases, the downward velocity near the wing walls decayed more rapidly than that near the furnace center. Increasing the mass ratio of pulverized coal in fuel-rich flow to that in fuel-lean flow and reducing the secondary air ratio while simultaneously increasing the tertiary air ratio was found to increase the penetration depth. Increasing the distance between adjacent burners, optimally lowering the fuel-rich and fuel-lean flow velocities, and reducing the secondary air velocity all decreased the penetration depth. The comprehensively improved downward airflow depth and air flux into the furnace hopper were reduced by 6.3% and 14.9%, respectively. Cold-state airflow tracing tests were performed in an actual boiler, the improved downward airflow depth reduced apparently, which was consistent with the results from modeling tests. Industrial-scale hot-state experiments determined improved hopper near-wall temperatures of 700–800 °C near the furnace center (values that were lower than those of 800–900 °C near the wing walls). These values were approximately 450 °C less than the prior temperatures at the same location, indicating the flame penetration depth was greatly reduced.

Secondary flow and heat transfer coefficient distributions in the developing flow region of ribbed turbine blade cooling passages

This paper reports an experimental and numerical study of the development and coupling of aerodynamic flows and heat transfer within a model ribbed internal cooling passage to provide insight into the development of secondary flows. Static instrumentation was installed at the end of a long smooth passage and used to measure local flow features in a series of experiments where ribs were incrementally added upstream. This improves test turnaround time and allows higher-resolution heat transfer coefficient distributions to be captured, using a hybrid transient liquid crystal technique. A composite heat transfer coefficient distribution for a 12-rib-pitch passage is reported: notably the behaviour is dominated by the development of the secondary flow in the passage throughout. Both the aerodynamic and heat transfer test data were compared to numerical simulations developed using a commercial computational fluid dynamics solver. By conducting a number of simulations it was possible to interrogate the validity of the underlying assumptions of the experimental strategy; their validity is discussed. The results capture the developing size and strength of the vortical structures in secondary flow. The local flow field was shown to be strongly coupled to the enhancement of heat transfer coefficient. Comparison of the experimental and numerical data generally shows excellent agreement in the level of heat transfer coefficient predicted, though the numerical simulations fail to capture some local enhancement on both the ribbed and smooth surfaces. Where this was the case, the coupled flow and heat transfer measurements were able to identify missing velocity field characteristics.

Vocal function after transoral videolaryngoscopic surgery (TOVS) for hypopharyngeal and supraglottic cancer

Conclusion: The resection of the medial and lateral pyriform sinus was associated with post-operative voice impairment after TOVS. Scar contracture around the cricoarytenoid joint lead to arytenoid fixation toward lateral position, and this wound healing process caused insufficient glottis closure. Although oncological and functional outcomes of TOVS was satisfactory, surgeons should mention the risk of post-operative voice impairment in pre-operative counseling.Objectives: Transoral surgery is a minimally invasive treatment option for hypopharyngeal and supraglottic cancer. Post-operative vocal function was satisfactory in most cases, but in some cases vocal cord was fixed and occasionally voice impairment persists.Methods: Vocal function of 55 patients who underwent transoral videolaryngoscopic surgery (TOVS) for hypopharyngeal and supraglottic cancers was evaluated by the GRBAS perceptive scale, aerodynamic tests and acoustic analyses, and the Voice Handicap Index questionnaire. The risk factors for voice impairment were identified.Results: Voice impairment (G score ≧2) was found in 16 cases (29.1%). Univariate analysis revealed that the resection of medial and lateral pyriform sinus (p = .0018) and neck dissection (p = .0421) were associated with post-operative voice impairment. Multivariate analysis revealed that the resection of medial and lateral pyriform sinus (p = .0021) was associated with post-operative voice impairment.

Flutter suppression of long-span suspension bridge with truss girder

Section model wind tunnel test is currently the main technique to investigate the flutter performance of long-span bridges. Further study about applying the wind tunnel test results to the aerodynamic optimization is still needed. Systematical parameters and test principle of the bridge section model are determined by using three long-span steel truss suspension bridges. The flutter critical wind at different attack angles is obtained through section model flutter test. Under the most unfavorable working condition, tests to investigate the effects that upper central stabilized plate, lower central stabilized plate and horizontal stabilized plate have on the flutter performance of the main beam were conducted. According to the test results, the optimal aerodynamic measure was chosen to meet the requirements of the bridge wind resistance in consideration of safety, economy and aesthetics. At last the credibility of the results is confirmed by full bridge aerodynamic elastic model test. That the flutter reduced wind speed of long-span steel truss suspension bridges stays approximately between 4 to 5 is concluded as a reference for the investigation of the flutter performance of future similar steel truss girder suspension bridges.

The Efficacy of Fibroblast Growth Factor for the Treatment of Chronic Vocal Fold Scarring: From Animal Model to Clinical Application.

ObjectivesThis study assessed the regenerative efficacy of basic fibroblast growth factor (FGF) in a rabbit model of chronic vocal fold scarring and then confirmed its utility and safety in a prospective trial of patients with this condition.MethodsFGF was injected three times, at 1-week intervals, into a chronic vocal fold scar created in a rabbit model. After 1 month, mRNA level of procollagen I, hyaluronic acid synthetase 2 (HAS 2), and matrix metalloproteinase 2 (MMP 2) were analyzed by real-time polymerase chain reaction. The relative densities of hyaluronic acid (HA) and collagen were examined 3 months post-injection. From April 2012 to September 2014, a prospective clinical trial was conducted at a tertiary hospital in Korea. FGF was injected into the mild vocal fold scar of 17 consecutive patients with a small glottic gap. The patients underwent perceptual, stroboscopic, acoustic aerodynamic test, and Voice Handicap Index (VHI) survey prior to and 3, 6, and 12 months after FGF injection.ResultsFGF injection of the vocal fold scar decreased the density of collagen and increased mRNA level of HAS 2 and MMP 2 expression significantly compared to the control group injected with phosphate buffered solution in a rabbit model (P<0.05). In the clinical trial, significant improvements in the majority of the subjective and objective voice parameters were registered 3 months after FGF injection and were maintained at 12 months. Complications associated with the FGF injections, such as granuloma, were not observed during the follow-up period.ConclusionBased on the animal model and the prospective clinical trial, vocal fold injections of FGF in patients with mild chronic vocal fold scarring can significantly improve voice quality for as long as 1 year and without side effects. Our results recommend the use of FGF vocal fold injection as an alternative treatment modality for mild chronic vocal fold scarring.

Track-Based Aerodynamic Testing of a Heavy-Duty Vehicle: Coast-Down Measurements

Track-Based Aerodynamic Testing of a Heavy-Duty Vehicle: Coast-Down Measurements