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Experimental approach

Model description:

The CAE Aerodynamic Validation Model (CAE-AVM) represents a geometry for a small commercial jet aircraft. The aircraft consists of a narrow fuselage, low wing configuration with a wing-fuselage belly fairing, aft fuselage mounted engines and a T-tail. It comprises a transonic supercritical swept wing of high aspect ratio and is designed for a cruise Mach number of 0.85 at corresponding design lift coefficient of 0.50. A drawing and a survey of main geometrical data is shown below. 

The wind tunnel model is designed for measurements of the overall aerodynamic loads and wing pressure distributions. The overall forces and moments are measured by means of an internal strain gauge balance. The design of the model is such that this balance can be mounted on either a ventral Z-sting support, or a dorsal sting support, thereby allowing the model to be used for dedicated support interference investigations. The wing is specifically designed to allow for the measurements of wing pressure distributions, whilst maintaining appropriate stiffness in order to minimize wing deformation under loads. The left and right wing together comprise a total of 180 pressure orifices located in 6 span-wise wing stations (η = 0.20, 0.35, 0.45, 0.55, 0.65 and 0.75).

Two main model configurations are used for the wind tunnel testing: the full-model and wing-fuselage combination (full model without tail and engines). For the full model configuration, the engines are represented by through flow nacelles.

The model design and manufacturing is done by the Dutch National Aerospace Centre, the NLR.

Impression of the CAE-AVM wind tunnel model

 Main geometrical data
 Wing reference area (S) is 0.20751 m²
 Wing reference span (b) is 1.3718 m
 Mean aerodynamic chord (c) is 0.19875 m.
 Wing aspect ratio (A) is 9.0
 Quarter chord sweepback angle (λ) is 35 degrees. 
 Xmrp=0.4954 m (defined in body axis system)
 Ymrp=0.0000 m (i.e. in the vertical symmetry plane)
 Zmrp=0.0000 m (i.e. below the fuselage centreline)


Wind tunnel facility:   

The experimental investigations with the CAE-AVM are performed in the high-speed wind tunnel HST, one of the wind tunnels within the German-Dutch Wind Tunnels organization, DNW. The DNW-HST is a variable density closed-return circuit wind tunnel with a transonic test section.

The 2.00 m wide test section has solid side walls and slotted top and bottom walls. Top and bottom walls can be adjusted to obtain a test section height of 1.60 m or 1.80 m. Each of the test section configurations allows for testing between Mach number 0.15 and 1.35. The stagnation pressure can be varied between 25 and 390 kPa; along with automated pressure and temperature control systems the HST provides individual control of the test sections Mach number and Reynolds number.

The HST features a number of standardized primary model support systems, allowing for longitudinal and/or lateral investigations with full span models. A secondary model support system is available for experimental investigations of the primary support systems interference. The HST further features a dedicated side wall support for half model testing, as well a 2D support system. For assessment of wall interference effects, all test section walls are equipped with wall pressure taps.

Typical steady measurement techniques for HST comprise internal strain gauge balances, external balances and electronic pressure scanning modules. The test sections provides sufficient optical access for application of techniques such as particle image velocimetry, pressure sensitive paint, temperature sensitive paint, infrared thermography and/or wing deformation measurements using stereo imaging techniques. Dynamic data acquisition systems are available as well for investigations of unsteady phenomenon like buffet and/or deep stall characteristics.

Test conditions and test approach:

The main objective of the investigations with the CAE-AVM was to acquire reliable experimental data for comparative analysis and validation of CAE’s Computational Fluid Dynamics (CFD) code. To this end the wind tunnel test comprised:

  • Balance measurements for the overall aerodynamic forces and moments
  • Pressure measurements for assessment of the wing load distribution
  • Wing deformation measurements with stereo pattern recognition
  • Flow visualization with infrared thermography
  • Flow visualization with coloured oil
  • Dedicated support interference measurements
  • Wall pressure measurements

The CAE-AVM was set-up on a 2.5” internal strain gauge balance, which was connected with a ventral z-sting to the primary straight boom model support. This primary support allows for longitudinal investigations in an angle of attack range from -5° to +20°. The ventral z-sting was specifically selected for its low aerodynamic support interference which was also determined experimentally, by means of a secondary (dorsal sting) test set-up.

In parallel with the load measurements, all pressure measurements are made using PSI temperature compensated Electronically Scanned Pressure (ESP) modules. Along with these measurements also the wing deformation was measured for each test condition. To this end a stereo imaging camera set-up was used to measure the relative displacement of UV illuminated markers.

Laminar-turbulent boundary layer transition is fixed on the model using adhesive trip dots on the wings, the vertical and horizontal tail planes, pylons, nacelles and on the fuselage nose. Infrared thermography is used for validation of the effectiveness of the tripping dots on the wing.

All testing was conducted at Reynolds number between 2.0 and 4.7 million, based on the model mean aerodynamic chord. Several Mach numbers are measured, ranging from 0.40 to 0.90. The data were acquired at temperatures between 20 and 40 degrees Celsius.