Developing Advanced Diagnostics for Convective Heat Transfer

Particle Image Velocimetry (PIV)

This laser diagnostic tool is capable of measuring fluid velocity fields. Fluid seeding particles are illuminated by a laser sheet and are imaged with two cameras, Stereo PIV, in order to obtain three component velocity. A four camera set-up, Tomographic PIV, can also be implemented to take volumetric measurements. This system can run at high speeds, 2 kHz, meaning that both time-averaged and time-resolved data can be taken. Common uses of this tool include measuring film cooling, junction flows, and vortex flowfields.

Velocity profile snapshot immediately upstream of an airfoil

Laser Doppler Velocimetry (LDV)

LDV is a measurement technique that uses the doppler shift of two intersecting lasers to make point velocity measurements in a fluid flow. Laser light reflected by the fluid particles will fluctuate in intensity at frequency which is proportional to the velocity at that location. Being able to measure small volumes enables the capability of determining velocity profiles near walls. Data is typically taken at multiple discrete locations across some distance to generate boundary layer profiles or velocity profiles for internal flows.

Measured boundary layer profile against a correlation

Thermographic Particle Image Velocimetry (TPIV)

This advanced diagnostic capability allows simultaneous temperature and velocity flow field measurements. Laser excitation of solid phosphor particles causes luminescence that is imaged by two optically overlapped cameras, allowing temperature calculation using a two-color ratiometric approach. A standard PIV camera uses these same particles for velocity measurement. This technique can be applied in film cooling and junction flow heat transfer studies, and will enable the calculation of derived quantities such as the turbulent heat flux.

An instantaneous TPIV temperature and velocity snapshot of a heated jet