﻿ ProSTools - Wind Tunnel Testing

## WIND TUNNEL TESTING

#### Aim of the Course:

The main purpose of the course is to gain knowledge in wind tunnel (WT) aerodynamic testing of missile type configuration models. The lectures cover Low and high speed testing, model design, internal and external balances consideration, data acquisition and reduction. Course lectures is supported by related slides and examples of calculation. Related references will be suggested for detail readings. The extensions of the course can be by practical examples of measurements in small laboratory for electromechanical measurements (see "Practical exercises in measurements")

#### Who should attend?

The course is intended for students, engineers - researchers in the research institutions and engineers in the productions factories. It is advanced course in aerodynamics, and it is assumed that attendants have good knowledge in mathematics, gas dynamics and aerodynamics.

#### Duration:

Duration is three weeks (18 working days); 72 lectures (one lecture duration 45 min), but other arrangement is possible.

#### Course Outline

 1. Introduction The role of WT in aerodynamic design, Properties of air, Mach number, Reynolds number, Review of one-dimensional compressible flow equations. Review of aerodynamic forces, coefficients and derivatives, Influence of similarity parameters on aerodynamic coefficients.
 2. Types of WT Aeronautical WT, Smoke tunnels, Water tunnels, Automobile WT, Environmental WT, Open and closed circuits WT, Shock tubes.
 3. Basic WT Subsystems Methods of air accelerating, Power plant, Working sections, Force and moment measurement equipment, Diffusers, Fan-Straightening section, Drive systems.
 4. Flow Similarity Laws Scale effect, Trip strips, Influence of tunnel walls, Influence of wall boundary layer thickness, Influence of flow turbulence.
 5. Internal Balances Measurements of forces and moments by internal balances – introduction. Internal balance construction, Strain gages, Whetstone bridge, Signal conditioner, Axial force bridge, Normal and side force bridge, Rolling moment bridge, pitching and yawing moment bridges.
 6. External Balances Construction of external balance, Force and moment measurements, Advantages and disadvantages of external balance method.
 7. Model Design and Installation Basis of model construction, Body design, Lifting surface design, Control surface design, Force model, Pressure model, Model-balance connection.
 8. Supporting the Model Straight sting, Bent sting, High attitude robotic sting, Advantages and disadvantages.
 9. Continuous Operation WT Layout of WT, Power plant and compressor matching, Diffuser characteristics, Flow returning section, Drop of temperature and cooling the air, Humidity and drying of air.
 10. Intermittent (Blow-down) WT Pressure chamber, Pressure regulating valve and stagnation pressure regulation, First and second diffuser, Working section. Atmospheric entry WT with vacuum pump - Characteristics and layout, Advantages and disadvantages.
 11. Mach number(Ma) regulation Regulation of Ma by setting the nozzle geometry, Regulation of Ma by flow suction in transonic flow, Regulation of Ma by injection of flow, regulating subsonic Ma by pressure difference.
 12. Specifics of Transonic WT and Working Sections Influence of tunnel wall. Methods of cancellation of reflected waves. Two-dimensional working sections.
 13. Hypersonic WT Specifics of hypersonic flow and WT. Measurement of force, pressure and temperature. WT with air heater. Types and Layout of shock tubes, Advantages and disadvantages.
 14. Flow Measurements Static pressure measurements, Total pressure measurement by Pitot probe, Mach number determination, Temperature measurement, Reynolds number determination. Pressure-Sensitive Paint (PSP) method of determination of instantaneous pressure field.
 15. Flow Visualization Index of refraction, Schlieren method, Shadow method, Laser-Doppler anemometry, Interferometer techniques, Smoke technique. Particle Image Velocimetry (PIV) method and apparatus, Advantages and disadvantages.
 16. Balance Calibration Calibration curves and calibration standard, Mathematical bases of multi-dimensional polynomial regression, Calibration techniques, Explanation of calibration software.
 17. Static Tests Standard measurement of six component forces and moments, Base pressure measurement, Measurement of normal force, bending moment and hinge moment on fin alone, Measurement of dawn-wash force.
 18. Dynamic Derivative Measurements Methods of dynamic measurements, Free oscillation measurements, Forced oscillation measurements.
 19. WT Data Acquisition, Reduction and Analyzing Data acquisition cards, Signal filtering, data storing and manipulating, Determining the aerodynamic coefficients from balance data, Correction for sting deformation and flow angular misalignment.
 20. Flow Quality Parameters and Working Section Calibration Pressure fluctuations, Longitudinal, variation of velocity across working section, Mean velocity and Mach number, Variation of mean velocity and flow angularity, Turbulence.
 21. Additional Data Reduction Polynomial representation of aerodynamic coefficients with respect to AOA and control deflection, Fourier representation of aerodynamic coefficients with respect to aerodynamic roll angle, Estimation of centre of pressure, static lateral and longitudinal stability derivatives.
 22. Planning and Organization of WT tests Objectives of WT test programs, Tests programs in design phase and in development phase, Determination of minimal number of runs, Economical aspects.

Lecturer: Dr Miodrag Curcin