High Speed PIV and Shadowgraphy Measurements in Water Hammer
R. Capanna, P. M. Bardet
Dept. of Mechanical and Aerospace Engineering, The George Washington University, USA
An experimental study addressing the challenge to measure relaxation coefficient of very fast phenomena such as water hammers is presented. A titanium projectile containing a sapphire tube containing water is accelerated and impacts a metal wall creating a water hammer. A compressed air custom built cannon is used to accelerate the projectile and create the impact leading to the water hammer. The sapphire tube, being transparent to green and UV light allows the deployment of non intrusive laser based diagnostic techniques such as Particle Image Velocimetry, Shadowgraphy, and Fiber Optic Hydrophone pressure measurements. These laser based techniques will be deployed at a very high repetition rate (>100 kHZ) to measure the relaxation coefficients between gas and water phase. First experimental results for Shadowgraphy and PIV measurements are presented. The propagation speed of shock wave in the projectile has been estimated from shadowgraphy measurements and matched the theoretical calculation. Discussion on the future development for the presented facility concludes this paper.