scholarly journals Airfoil lift calculation using wind tunnel wall pressures

2021 ◽  
pp. 095441002110382
Author(s):  
Sreevishnu Oruganti ◽  
Shreyas Narsipur
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Static Pressure ◽  
Reference Data ◽  
Measurement Techniques ◽  
Surface Flow ◽  
Flow Conditions ◽  
Tunnel Wall ◽  
Number Range ◽  
Sensitivity Studies

An experimental method to calculate lift using static pressure ports on the wind tunnel walls and its associated limits has been explored in this article. While the wall-pressure measurement (WPM) technique for lift calculation has been implemented by other researchers, there is a lack of literature on the sensitivity of the WPM method to airfoil chord length, model thickness, surface roughness, and freestream conditions. Chord sensitivity studies showed that the airfoil chord to test section length ratio plays an important role in the accuracy of the measurements. Models need to be appropriately sized for optimum performance of the WPM method. Additionally, choosing the correct scaling ratio also ensures independence of lift measurements from freestream Reynolds number conditions. Finally, a combination of symmetric and cambered airfoils with thicknesses varying from 6 % − 21 % were tested and successfully validated against reference data for a freestream chord Reynolds number range of 100,000 to 550,000. The WPM method was found to be sensitive to varying surface flow conditions and airfoil thickness and has been shown to be a viable replacement to traditional lift measurement techniques using load balances or airfoils with surface pressure ports.

The effects of surface roughness and tunnel blockage on the flow past spheres

1974 ◽  
Vol 65 (1) ◽  
pp. 113-125 ◽  
Author(s):  
Elmar Achenbach
Keyword(s):  
Surface Roughness ◽  
Reynolds Number ◽  
Drag Coefficient ◽  
Critical Reynolds Number ◽  
Measurement Techniques ◽  
Flow Conditions ◽  
Number Range ◽  
Flow Past ◽  
Reynolds Number Range ◽  
Shedding Frequency

The effect of surface roughness on the flow past spheres has been investigated over the Reynolds number range 5 × 104 < Re < 6 × 106. The drag coefficient has been determined as a function of the Reynolds number for five surface roughnesses. With increasing roughness parameter the critical Reynolds number decreases. At the same time the transcritical drag coefficient rises, having a maximum value of 0·4.The vortex shedding frequency has been measured under subcritical flow conditions. It was found that the Strouhal number for each of the various roughness conditions was equal to its value for a smooth sphere. Beyond the critical Reynolds number no prevailing shedding frequency could be detected by the measurement techniques employed.The drag coefficient of a sphere under the blockage conditions 0·5 < ds/dt < 0·92 has been determined over the Reynolds number range 3 × 104 < Re < 2 × 106. Increasing blockage causes an increase in both the drag coefficient and the critical Reynolds number. The characteristic quantities were referred to the flow conditions in the smallest cross-section between sphere and tube. In addition the effect of the turbulence level on the flow past a sphere under various blockage conditions was studied.

Experimental Results of Flow Nozzle Based on PTC 6 for High Reynolds Number

2014 ◽  
Author(s):  
Noriyuki Furuichi ◽  
Kar-Hooi Cheong ◽  
Yoshiya Terao ◽  
Shinichi Nakao ◽  
Keiji Fujita ◽  
...  
Keyword(s):  
Reynolds Number ◽  
High Reynolds Number ◽  
Discharge Coefficient ◽  
Experimental Results ◽  
Flow Conditions ◽  
Number Range ◽  
Discharge Coefficients ◽  
Reynolds Number Range ◽  
Lower Reynolds Number ◽  
High Reynolds

Discharge coefficients for three flow nozzles based on ASME PTC 6 are measured under many flow conditions at AIST, NMIJ and PTB. The uncertainty of the measurements is from 0.04% to 0.1% and the Reynolds number range is from 1.3×105 to 1.4×107. The discharge coefficients obtained by these experiments is not exactly consistent to one given by PTC 6 for all examined Reynolds number range. The discharge coefficient is influenced by the size of tap diameter even if at the lower Reynolds number region. Experimental results for the tap of 5 mm and 6 mm diameter do not satisfy the requirements based on the validation procedures and the criteria given by PTC 6. The limit of the size of tap diameter determined in PTC 6 is inconsistent with the validation check procedures of the calibration result. An enhanced methodology including the term of the tap diameter is recommended. Otherwise, it is recommended that the calibration test should be performed at as high Reynolds number as possible and the size of tap diameter is desirable to be as small as possible to obtain the discharge coefficient with high accuracy.

Flow separation on a spheroid at incidence

1979 ◽  
Vol 92 (4) ◽  
pp. 643-657 ◽  
Author(s):  
Taeyoung Han ◽  
V. C. Patel
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Inviscid Flow ◽  
Reynolds Numbers ◽  
Surface Flow ◽  
Laminar Separation ◽  
Low Reynolds Numbers ◽  
Turbulent Separation

Surface streamline patterns on a spheroid have been examined at several angles of attack. Most of the tests were performed at low Reynolds numbers in a hydraulic flume using coloured dye to make the surface flow visible. A limited number of experiments was also carried out in a wind tunnel, using wool tufts, to study the influence of Reynolds number and turbulent separation. The study has verified some of the important qualitative features of three-dimensional separation criteria proposed earlier by Maskell, Wang and others. The observed locations of laminar separation lines on a spheroid at various incidences have been compared with the numerical solutions of Wang and show qualitative agreement. The quantitative differences are attributed largely to the significant viscous-inviscid flow interaction which is present, especially at large incidences.

scholarly journals Parametric Experiments on Coaxial Airblast Jet Atomization

1990 ◽  
Author(s):  
Zoltan Farago ◽  
Norman Chigier
Keyword(s):  
Reynolds Number ◽  
Flow Rate ◽  
High Speed ◽  
Liquid Sheet ◽  
Velocity Range ◽  
Air Flow Rate ◽  
Flow Conditions ◽  
Number Range ◽  
Reynolds Number Range ◽  
Air Stream

Experiments using high speed, high magnification, and high contrast photography on airblast coaxial atomizers were carried out to study the wave characteristics of liquid surfaces, ligament breakup, and droplet formation. Liquid flow rate was changed from 4 to 50 kg/h, corresponding to a velocity range of 1.5 to 18 m/s, and a Reynolds number range of 1400 to 18000. Air flow rate was varied from 8 to 70 kg/h, corresponding to a velocity range of 22 to 180 m/s, and a Reynolds number range of 13000 to 105000. Tube wall thicknesses of 145 and 320 microns were used. Under different flow conditions, different jet instabilities (capillary, helical and Kelvin-Helmholtz) and different dominant mechanisms of ligament formation were observed. One of the most surprising experimental results is that, under certain flow conditions, the coaxial round liquid jet, surrounded by an axisymmetric annular air stream, forms a flat curling liquid sheet. This liquid sheet breaks into droplet clouds with a frequency of a few thousand Hertz and emits strong oscillations and fluctuating, highly non-axisymmetric vibrations.

The Effects of Reynolds Number on the Stall and Pre-Stall Behaviour of Compact Axial Compressors

2020 ◽  
Author(s):  
Jack Hutchings ◽  
Cesare Hall
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Static Pressure ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Critical Value ◽  
Rotating Stall ◽  
Secondary Flows ◽  
Transitional Flow ◽  
Number Range

Abstract Compact axial compression systems are of interest to the domestic appliance industry. The associated low Reynolds number leads to high losses compared to large-scale compressors due to a transitional flow field with large regions of separation. This paper investigates how Reynolds number variations affect the three-dimensional and unsteady flow field in a compact compressor both pre-stall and in stall. An experimental study has been conducted using a scaled-up singlestage axial compressor across a Reynolds number range of 104 to 105. Steady and unsteady casing static pressure measurements, along with rotor upstream and downstream unsteady velocity measurements, have been used to observe the rotor flow field. As the Reynolds number is reduced below a critical value, 60,000 in the case of the compressor studied, the pressure rise coefficient of the compressor decreases. The exact value of the critical Reynolds number is expected to vary with the compressor geometry. This fall off in performance corresponds to an increase in the compressor rotor secondary flows. Prior to stall, a broadband hump at around 50% of the blade passing frequency is present in the near-field casing static pressure spectra. At Reynolds numbers below the critical value, multiple equally spaced peaks also appear around the peak of the broadband hump. The spacing of these peaks has been found to be exactly equal to the measured stall cell speed once rotating stall is established. When operating in stall, the stall cell is found to increase in size and slow down as Reynolds number decreases. The measured spectra and observed flow structures show that disturbances exist prior to stall at frequencies consistent with the frequencies within stall. The size and shape of the stall cells that form are related to the extent of the three-dimensional flow field present prior to stall. Below a critical value, all of these flow features are highly sensitive to Reynolds number.

scholarly journals Reynolds number and wind tunnel wall effects on the flow field around a generic UHBR engine high-lift configuration

2020 ◽  
Vol 11 (4) ◽  
pp. 1009-1023 ◽  
Author(s):  
Junaid Ullah ◽  
Aleš Prachař ◽  
Miroslav Šmíd ◽  
Avraham Seifert ◽  
Vitaly Soudakov ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Wind Tunnel ◽  
Flow Field ◽  
Test Section ◽  
Large Scale ◽  
Scale Model ◽  
Small Scale ◽  
Wall Effects ◽  
Tunnel Wall ◽  
High Lift

Abstract RANS simulations of a generic ultra-high bypass ratio engine high-lift configuration were conducted in three different environments. The purpose of this study is to assess small scale tests in an atmospheric closed test section wind tunnel regarding transferability to large scale tests in an open-jet wind tunnel. Special emphasis was placed on the flow field in the separation prone region downstream from the extended slat cut-out. Validation with wind tunnel test data shows an adequate agreement with CFD results. The cross-comparison of the three sets of simulations allowed to identify the effects of the Reynolds number and the wind tunnel walls on the flow field separately. The simulations reveal significant blockage effects and corner flow separation induced by the test section walls. By comparison, the Reynolds number effects are negligible. A decrease of the incidence angle for the small scale model allows to successfully reproduce the flow field of the large scale model despite severe wind tunnel wall effects.

Effect of Wind-Tunnel Walls on the Flow Past Circular Cylinders and Cooling Tower Models

1977 ◽  
Vol 99 (3) ◽  
pp. 470-479 ◽  
Author(s):  
Ce´sar Farell ◽  
Saul Carrasquel ◽  
Oktay Gu¨ven ◽  
V. C. Patel
Keyword(s):  
Surface Roughness ◽  
Reynolds Number ◽  
Wind Tunnel ◽  
Cooling Tower ◽  
Pressure Coefficient ◽  
Base Pressure ◽  
Circular Cylinders ◽  
Cooling Towers ◽  
Number Range ◽  
Geometry Model

The effect of wind tunnel walls on the mean pressure distributions on rough-walled circular cylinders and on cooling tower models fitted with longitudinal ribs is studied experimentally in the range of Reynolds-number independence. For circular cylinders the results are compared with analytical corrections based on formulae of Allen and Vincenti, and of Maskell, which are found to be generally applicable in this Reynolds number range. For cooling towers, a correction procedure is proposed using the base pressure coefficient, Cpb, and the dimensionless pressure rise to separation, Cpb–Cpm, where Cpm is the minimum value of the pressure coefficient. The base pressure coefficient Cpb for cooling towers is (in the Reynolds-number-independent range) a function of the boundary geometry: model shape, tunnel type (open or closed jet) and blockage, and is independent of surface roughness. The difference Cpb–Cpm, on the other hand, is mainly a function of surface roughness for both cylinders and cooling towers and is very little, if at all, affected by tunnel blockage for blockages less than, say, 15 percent.

Variable Reynolds Number Experimental Study on Aerodynamic Characteristic of Supercritical Airfoil RAE2822

2013 ◽  
Vol 420 ◽  
pp. 42-46
Author(s):  
Na Wang ◽  
Chao Gao
Keyword(s):  
Experimental Study ◽  
Reynolds Number ◽  
Wind Tunnel ◽  
Pressure Distribution ◽  
Pressure Coefficient ◽  
Lower Surface ◽  
Number Range ◽  
Moment Coefficient ◽  
Pressure Distributions ◽  
The Moment

An experimental study of pressure distributions over RAE2822 airfoil in the two-dimensional test section 0.8×0.4 meter of a transonic wind tunnel which is the first pressruized continuous wind tunnel in China is presented. This paper in order to further study the influence of the dynamic of continuous changes Reynolds number at Mach number is 0.66 and 0.80, and the attack angle is from-2 degree to 10 degree, and especially the Reynolds number range from3.0×106to 12×106. The study is focalized on the subsonic range of flow conditions with separation and shock wave in the boundary layer. The influence of pressure distribution and pressure coefficient and moment coefficient caused by Reynolds number increasing are analyzed and discussed. The conclusions showed that the pressure distribution of the lower surface of the airfoil get the influence of the Reynolds number is negligible. The Reynolds number impact on the pressure distribution is faintness at Ma=0.66. Reynolds number increases affect the airfoil central and trailing edge pressure. As the Reynolds number increases, the CL curve move and the gradient increasing. The moment coefficient decreased as the Reynolds number increasing. The CL curve with Cd curve moves left as Reynolds number increasing.

Sign in / Sign up

Export Citation Format

Share Document