Application of optical flow visualisation method Schlieren on cavitation

Pri kavitaciji nastanejo udarni valovi, ki imajo visoke temperature in tlake. S pomočjo metode optične vizualizacije toka tekočin schlieren je mogoče spremljati te spremembe v gostoti. Izbira sistema schlieren z dvema zrcaloma bi izboljšala kvalitativne rezultate in povečala dostopnost in uporabnost metode. V diplomski nalogi je predstavljena optimizirana postavitev Z sistema schlieren. Eksperimenti so bili izvedeni pri različnih nastavitvah ultrazvočne sonde in letalskem propelerju. Iz analize sklepamo, da povečanje amplitude pri enaki frekvenci in zmanjšanje velikosti konice ultrazvočne sonde poveča intenziteto udarnih valov in zmanjša njihovo frekvenco nastanka. Povprečna hitrost udarnih valov je višja od zvočne hitrosti v vodi pri enakih pogojih. Sistem je primeren tudi za opazovanje vrtincev na konicah letalskih propelerjev. Uporaba metode schlieren z dvema zrcaloma je zato primerna za opazovanje in analizo udarnih valov ter opazovanje kavitacije pri večjih sistemih.Cavitation produces shock waves that have high temperatures and pressures. Density gradients that occur can be monitored with an optical flow visualisation technique called the schlieren method. Schlieren system with two mirrors would improve the qualitative results and increases accessibility and usefulness of the method. The diploma thesis presents the optimized layout Z of the schlieren system. Experiments were performed on different settings of the ultrasonic probe and an aircraft propeller. The analysis concludes that increasing the amplitude at the same frequency and reducing the tip size of the ultrasonic probe increases the intensity of the shock waves and reduces their frequency. The average velocity of the shock waves is higher thant the sound velocity in water under the same conditions. The system is also suitable for the observation of propeller blade tip vortices. The use of the schlieren method with two mirrors is therefore suitable for observing and analysis of shock waves and for the observation of cavitation in larger systems