Application of photobleaching molecular tagging velocimetry to turbulent bubbly flow in a square duct

• Published in: Experiments in fluids Vol. 47; no. 4-5; pp. 745 - 754
• Main Authors: Hosokawa, Shigeo, Fukunaga, Takayuki, Tomiyama, Akio
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.10.2009; Springer
• Subjects: Biological and medical applications; Dissipation; Ducts; Engineering; Engineering Fluid Dynamics; Engineering Thermodynamics; Exact sciences and technology; Fluid dynamics; Fluid flow; Fluid- and Aerodynamics; Fundamental areas of phenomenology (including applications); Heat and Mass Transfer; Instrumentation for fluid dynamics; Metrological applications; Molecular tagging velocimetry; Multiphase and particle-laden flows; Nonhomogeneous flows; Optics; Physics; Research Article; Turbulence; Turbulent flow; Walls; Bubbly Flow; Velocity Gradient; Laser Doppler Velocimetry; Reynolds Shear Stress; Particle Image Velocimetry; Rectangular pipe; Fluid mechanics; Turbulent flow; Measuring methods; Optical systems; Molecular marker; Experimental study; Two-phase flow; Measurement by laser beam; Bubble flow; Velocity measurement; Turbulence structure; Photobleaching
• ISSN: 0723-4864; 1432-1114
• DOI: 10.1007/s00348-009-0690-x

To evaluate turbulence energy budget in bubbly flows, an image processing method in a photobleaching molecular tagging velocimetry is improved for accurate evaluation of velocity gradients. Turbulence properties in single-phase and two-phase dilute-bubbly flows in a square duct are measured using the improved method. As a result, the following conclusions are obtained: (1) The axial velocity and axial turbulent intensity measured by the present method agree well with those measured by laser Doppler velocimetry not only for the single-phase flow but also for the dilute-bubbly flow. (2) The present method can measure velocity components and velocity gradients in the vicinity of the wall, and therefore the present method is of great use in understanding the mechanism of turbulence generation and dissipation near the wall. (3) The present method can provide detailed information on turbulence structure such as turbulence kinetic energy budget. (4) Bubbles tend to increase not only the turbulence production but also the turbulence dissipation.