Large scale turbulent round free jet far field investigations using Shake-The-Box 3D Lagrangian Particle Tracking

Kurzfassung

Turbulent free jet flows have been a focal point of turbulence research for decades, representing a canonical flow with applications ranging from engineering contexts, such as aircraft engines, combustion, HVAC, and heat exchange, to providing fundamental insights into turbulent shear flows in general. This paper presents an experimental investigation of the flow in the far field of a round turbulent jet using large-scale STB on LED illuminated HFSB. The experiment was conducted in a large test room measuring 6 × 4 × 3.4 m^3= 82 m^3, with blackened walls on three sides and a tent-like ceiling (crest height at ~4 m along 6 m) made of black cloth. Air was expelled horizontally at a velocity of U_j = 49.75 m/s and a height of ~1.25 m above the floor at the measurement position using a circular contraction nozzle with a diameter of d = 10 mm, resulting in a Reynolds number of Re_d = 33,000. The particle images were processed using the Variable-Timestep-Shake-The-Box (VT-STB) LPT method, combined with the scanning approach. This allowed for an effective seeding density of over 0.1 particles per pixel. More than 400,000 HFSBs were simultaneously tracked and used as an input for the data assimilation algorithm FlowFit3 to obtain continuous fields of velocity and acceleration.