WIND ENG

WIND TUNNEL

is a scientific testing facility used primarily in the fields of aircraft and aerospace engineering to study how air flows around objects such as airplanes, rockets, and spacecraft.

subsonic

These operate at speeds less than the speed of sound (Mach < 1).

transonic

These tunnels operate around the speed of sound (approximately Mach 0.8 to 1.2).

supersonic

operate at speeds greater than the speed of sound (Mach > 1), which typically ranges from Mach 1.2 to 5.

hypersonic

typically operate at extremely higher speeds above Mach 5.

Scale models

are used because full-sized objects (like aircraft or rockets) are too large or expensive to test directly.

Geometric Similarity

All parts of the model are scaled versions of the real object. For example, a 1:10 aircraft model.

Kinematic Similarity

Flow streamlines must be similar; depends on velocity and motion replication.

Dynamic Similarity

Forces (inertial, pressure, viscous) must scale appropriately using Reynolds Number (for viscous/inertial forces) and Mach Number (for compressibility).

flow quality

Ensures reliable, consistent aerodynamic results.

Turbulence Intensity (TI)

Defined as % of velocity fluctuation.

Velocity Uniformity

Across the test section, ideally ±0.5% variation.

Yaw/Pitch Angle Uniformity

Less than ±0.05° deviation is acceptable in precision tunnels.

instrument and data collection

Records precise aerodynamic data during testing.

Blockage

is the obstruction of airflow due to the model’s size, altering the pressure

and velocity field in the test section.

wall effects and corrections

Accounts for how test section walls alter airflow around the model.

wind tunnel calibration

Ensures data accuracy and system reliability.

wind tunnel measurement techniques

are essential for analyzing the aerodynamic properties of objects like aircraft, cars, or buildings under controlled wind conditions.

force and moment measurement

This technique involves measuring the aerodynamic forces and moments acting on a model inside the wind tunnel.

pressure measurement

is used to understand how air pressure varies across the surface of a model.

Flow Visualization

help researchers see how air moves around a model.

Velocity Measurement

Understanding how fast and how air flows around a model is essential in aerodynamic studies.

Pitot-Static Probes:

are simple and reliable instruments that measure the difference between total and static pressure to calculate local airflow velocity.

Hot-Wire Anemometry:

uses a heated wire that cools as air passes over it, with the cooling rate indicating airflow speed—ideal for detecting small turbulence and velocity changes.

Laser Doppler Velocimetry (LDV):

is a non-contact method that uses intersecting laser beams; particles passing through scatter light, and the frequency shift reveals flow velocity.

Particle Image Velocimetry (PIV):

uses lasers and high-speed cameras to track tiny particles in the flow, producing detailed velocity maps of airflow patterns over time.

Model Deformation and Displacement

Understanding how a model physically responds to airflow is vital, especially in high-speed tests where aerodynamic forces can cause significant stress.

Photogrammetry

a modern, non-contact method where multiple high-speed cameras are used to track reflective markers placed on the model's surface.

Strain Gauges

small sensors bonded directly to the model’s surface.

Temperature Measurement

are important in wind tunnel tests, particularly at high speeds where friction and compression can heat up the air and model surface.

Thermocouples

commonly used to measure temperatures at specific points.

Infrared Cameras

used for full-surface thermal mapping.