A Kriging Approach for CFD/Wind-Tunnel Data Comparison

2005 ◽  
Vol 128 (4) ◽  
pp. 847-855 ◽  
Author(s):  
J.-C. Jouhaud ◽  
P. Sagaut ◽  
B. Labeyrie
Keyword(s):  
Wind Tunnel ◽  
Response Surface ◽  
Uncertain Parameters ◽  
Free Flight ◽  
Wind Tunnel Experiments ◽  
Data Comparison ◽  
Wind Tunnel Data ◽  
Compressible Turbulent Flow ◽  
Kriging Approach ◽  
Insight Into

A Kriging-based method for the parametrization of the response surface spanned by uncertain parameters in computational fluid dynamics is proposed. A multiresolution approach in the sampling space is used to improve the accuracy of the method. It is illustrated considering the problem of the computation of the corrections needed to recover equivalent free-flight conditions from wind-tunnel experiments. Using the surface response approach, optimal corrected values of the freestream Mach number and the angle of attack for the compressible turbulent flow around the RAE 2822 wing are computed. The use of the response surface to gain an insight into the sensitivity of the results with respect to other parameter is also assessed.

Comparison of free-flight and wind tunnel data for a generic fighterconfiguration

1982 ◽  
Author(s):  
G. WINCHENBACH ◽  
R. CHELEKIS ◽  
B. USELTON ◽  
W. HATHAWAY
Keyword(s):  
Wind Tunnel ◽  
Free Flight ◽  
Wind Tunnel Data

Wingbeat frequency of barn swallows and house martins: a comparison between free flight and wind tunnel experiments

2002 ◽  
Vol 205 (16) ◽  
pp. 2461-2467 ◽  
Author(s):  
Felix Liechti ◽  
Lukas Bruderer
Keyword(s):  
Wind Tunnel ◽  
Single Pulse ◽  
Free Flight ◽  
Wind Tunnel Experiments ◽  
Wingbeat Frequency ◽  
Flight Costs ◽  
Radar Echo ◽  
The Mean ◽  
Barn Swallows ◽  
Air Speed

SUMMARYThe flight paths and wingbeat patterns of 39 barn swallows (Hirundo rustica) and 26 house martins (Delichon urbica) were recorded by tracking radar during the spring migration. Depending mostly on flight angle,hirundines performed anything from continuous flapping flight during climbing to single pulse-like wing beats during descent. Unlike most other passerines,hirundines rarely showed regular flapping and rest phases, allowing them to be distinguished from other bird migrants by radar echo signatures. Effective wingbeat frequency (Feff) was calculated as the mean number of wing beats per second, including non-flapping phases. Under comparable flight conditions, Feff was higher in house martins than in barn swallows. Within species, Feff values were higher during climbing and slow flying than during descent. Of the variance in Feff, 71 % could be explained by climb rate,air speed and species; similar results were obtained in the wind tunnel. Under comparable flight conditions, barn swallows and house martins in free flight had significantly lower values of Feff than individuals in wind tunnel experiments (by 40 % and 32 %, respectively). This difference may at least partly be due to the shorter wings of the juveniles tested in the wind tunnel during autumn. However, it seems unlikely that this can account for all of the large difference. It is suggested that wind tunnel experiments might overestimate birds' flight costs compared with free flight.

Comparisons of free-flight and wind-tunnel data on slender cones

AIAA Journal ◽  
1965 ◽  
Vol 3 (2) ◽  
pp. 379-380 ◽  
Author(s):  
JACK D. WHITFIELD ◽  
B. J. GRIFFITH
Keyword(s):  
Wind Tunnel ◽  
Free Flight ◽  
Wind Tunnel Data

Free-flight and wind-tunnel data for a generic fighter configuration

1984 ◽  
Vol 21 (1) ◽  
pp. 5-13 ◽  
Author(s):  
G.L. Winchenbach ◽  
R. L. Uselton ◽  
W. H. Hathaway ◽  
R. M. Chelekis
Keyword(s):  
Wind Tunnel ◽  
Free Flight ◽  
Wind Tunnel Data

scholarly journals Experimental Analysis of a Small-Scale Rotor at Various Inflow Angles

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Amir Kolaei ◽  
Devin Barcelos ◽  
Götz Bramesfeld
Keyword(s):  
Wind Tunnel ◽  
Wind Tunnel Test ◽  
Axial Flow ◽  
Unmanned Aircraft ◽  
Performance Characteristics ◽  
Small Scale ◽  
Flow Conditions ◽  
Wind Tunnel Experiments ◽  
Wind Tunnel Data ◽  
Advance Ratio

The performance characteristics of a rotor that is typically used for small unmanned aircraft were analyzed in a series of wind-tunnel experiments. Wind-tunnel measurements were conducted with the rotor at various inflow angles in order to investigate the effects on the rotor performance of partially or fully edgewise flow as they are typically encountered with small multirotor vehicles. Rotor tests were also performed under static and fully axial flow conditions in order to investigate the aerodynamic performance during hover as well as vertical climb and descent. The wind-tunnel data were corrected to account for the interference of wind-tunnel walls with the rotor wake and the blockage due to the presence of the rotor test stand in the wind-tunnel test section. The results are presented in terms of thrust, power, and roll moment coefficients under different rotor rotational speeds for a T-motor 18x6.1. Additionally, the measured thrust and power coefficients of Master Airscrew Electric 11x7 are compared with available propeller data under static and axial flow conditions for verification purposes. It is shown that the rotor performance characteristics are strongly affected by the freestream advance ratio and the freestream inflow angles. For example, at inflow angles that are typical for multirotor vehicles between about 15° and 0° with respect to the rotor disc, thrust coefficients stay constant or grow with increasing advance ratio, whereas power coefficients remain relatively constant with changing advance ratio.

scholarly journals Aerodynamic Free-Flight Conditions in Wind Tunnel Modelling through Reduced-Order Wall Inserts

Fluids ◽  
2021 ◽  
Vol 6 (8) ◽  
pp. 265
Author(s):  
Narges Tabatabaei ◽  
Ramis Örlü ◽  
Ricardo Vinuesa ◽  
Philipp Schlatter
Keyword(s):  
Wind Tunnel ◽  
Layer Growth ◽  
Wind Tunnels ◽  
Good Representation ◽  
Free Flight ◽  
Local Pressure ◽  
Experimental Realization ◽  
Reduced Order ◽  
Moderate Reynolds Number ◽  
Wind Tunnel Data

Parallel sidewalls are the standard bounding walls in wind tunnels when making a wind tunnel model for free-flight condition. The consequence of confinement in wind tunnel tests, known as wall-interference, is one of the main sources of uncertainty in experimental aerodynamics, limiting the realizability of free-flight conditions. Although this has been an issue when designing transonic wind tunnels and/or in cases with large blockage ratios, even subsonic wind tunnels at low-blockage-ratios might require wall corrections if a good representation of free-flight conditions is intended. In order to avoid the cumbersome streamlining methods especially for subsonic wind tunnels, a sensitivity analysis is conducted in order to investigate the effect of inclined sidewalls as a reduced-order wall insert in the airfoil plane. This problem is investigated via Reynolds-averaged Navier–Stokes (RANS) simulations, and a NACA4412 wing at the angles of attack between 0 and 11 degrees at a moderate Reynolds number (400 k) is considered. The simulations are validated with well-resolved large-eddy simulation (LES) results and experimental wind tunnel data. Firstly, the wall-interference contribution in aerodynamic forces, as well as the local pressure coefficients, are assessed. Furthermore, the isolated effect of confinement is analyzed independent of the boundary-layer growth. Secondly, wall-alignment is modified as a calibration parameter in order to reduce wall-interference based on the aforementioned assessment. In the outlined method, we propose the use of linear inserts to account for the effect of wind tunnel walls, which are experimentally simple to realize. The use of these inserts in subsonic wind tunnels with moderate blockage ratio leads to very good agreement between free-flight and wind tunnel data, while this approach benefits from simple manufacturing and experimental realization.

Optimization of the Porosity Distribution in Transonic Wind Tunnel

2012 ◽  
Author(s):  
Antonello Marino ◽  
Aldo Bonfiglioli
Keyword(s):  
Wind Tunnel ◽  
Response Surface ◽  
Design Of Experiment ◽  
Wind Tunnels ◽  
Experimental Setup ◽  
Porosity Distribution ◽  
Variable Porosity ◽  
Wind Tunnel Data ◽  
Transonic Wind Tunnel

During past years, to improve the quality of wind tunnel data in transonic configurations, researchers first designed new wind tunnel geometries (as porous and/or slotted wind tunnels), then developed more accurate correction laws giving acceptable results in certain conditions but absolutely not sufficient to satisfy the increasing aeronautical requirements. Recent studies showed that the quality of wind tunnel data can be improved by using test sections provided with variable streamwise porosity distributions instead of the typical uniform ones. Some authors identified this new concept of variable porosity distribution as the third generation of porous wind tunnels. In order to improve knowledge about effects of the porosity distribution on the wall interference in subsonic/transonic conditions, an experimental investigation was carried out in the PT-1 CIRA transonic wind tunnel in the Mach range between 0.3 and 0.9 (over 400 test points were measured on different models and wall porosity configurations). At this aim, a dedicated experimental setup consisting in five plates positioned on the top and bottom walls of the PT-1 porous test section, has been designed and realized. Setting independently each plate, it is possible to obtain practically unlimited combinations of porosity distributions along the streamwise direction. The final purpose of the present activity was to evaluate the optimal porosity distribution able to minimize wind tunnel wall interferences in the considered Mach range. The huge number of factors (Mach number and the positions of the five plates setting the porosity distribution) made practically impossible to study the porosity distribution effects by using a traditional One Factor At a Time (OFAT) approach. Therefore, the optimum porosity distribution has been achieved through an experiment designed with a Modern Design of Experiment (MDOE) approach. Within the MDOE approach, the RSM (Response Surface Modeling) has been selected. The objective of the experiment, designed with the RSM approach, is to acquire a sufficient number of data to create one or more response surface models to be used to predict the response variable of interest (within a specified uncertainty) as function of the factors which can affect the selected response variables. The best porosity distribution able to improve the quality of wind tunnel data has been found for the PT-1 Wind Tunnel (but results and/or the procedure are applicable to all similar Wind Tunnels). In the present paper, to contextualize the activity, after a short summary of the historical wind tunnel development, the stat of art of the variable streamwise porosity distribution is discussed. Then, the experimental setup to simulate in wind tunnel several streamwise variable porosity distribution and the design of Experiment are described. Finally, the main experimental results are reported and critically analyzed.

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