Experimental Study on Turbulence Structure in Turbulent Plane Forced Plume

Funatani

Watanabe

2008

In this paper, non-intrusive imaging techniques for simultaneously measuring temperature and velocity fields of thermal liquid flows are described. The experimental methods for temperature imaging considered here are the thermo-sensitive liquid crystal tracers and the laser-induced fluorescence, which are combined with particle image velocimetry (PIV) to measure simultaneously the corresponding 2D and 3D velocity fields. The features of these experimental methods and characteristics are examined, covering the measurable temperature range, uncertainty of measurement, time response and so on. The successful examples of simultaneous measurement of temperature and velocity fields are described for turbulent Rayleigh-Bérnard convection of a horizontal fluid layer and turbulent buoyant plume issuing from a circular nozzle, and their physical mechanisms of transport phenomena are explained.

Section: Combined Lif Piv System For Application To Buoyant Plumesupporting

confidence: 62%

Simultaneous imaging techniques for temperature and velocity fields in thermal fluid flows

Funatani

Watanabe

2008

“…The fundamental characteristics of this flow configuration are reviewed by Chen and Rodi (1980) and List (1982). Later, the turbulence characteristics and its structure of the buoyant jet are studied experimentally by Papanicolaou and List (1988), Murota et al (1989), Subbarao and Cantwell (1992), Tian and Roberts (2003), Funatani et al (2004), Pham et al (2005), Watanabe et al (2005), and numerically by Prourde et al (2008). It should be mentioned that recent experimental studies are focused on the simultaneous measurement of velocity and temperature/concentration field of the buoyant jet, because they play an important role to understand the mechanism of large growth rate of the buoyant jet compared with that of non-buoyant jet.…”

Section: Introductionmentioning

confidence: 99%

Experimental and numerical study on onset of inflow in near field of buoyant jet at low Froude number

Maeda

Syuto

et al. 2011

In the present paper, the onset of inflow in the near field of a vertical buoyant jet issuing from a square duct is studied by experimental flow visualization and numerical simulation. The experimental critical condition for the onset of inflow is obtained from the scanning LIF visualization in the near field of the buoyant jet at various combinations of Froude numbers and Reynolds numbers. The experimental result shows that the critical Froude number increases with an increase in Reynolds number of the buoyant jet. The critical condition is also examined by numerical simulation based on the Navier-Stokes equation and energy conservation equation, under the assumption that the flow separation occurs at the duct exit. The main feature of the inflow observed by experiment is well reproduced in the numerical results.

“…The laminar length of the jet is studied experimentally at some combinations of the source Froude numbers and Reynolds numbers (Mollendorf and Gebhart 1973;Subbarao and Cantwell 1992). Later, turbulence measurements in the buoyant jets are reported by George et al (1977), Papanicolaou and List (1988), Murota et al (1989), Shabbir and George (1994), Dai et al (1994), who measured the turbulence characteristics of velocities and temperatures, using point measurement techniques, such as laser Doppler velocimetry, hot wire/film, thermocouple and laser-induced fluorescence techniques.…”

Section: Introductionmentioning

confidence: 99%

Flow visualization and scanning PIV measurement of three-dimensional structure in near field of strongly buoyant jet

Syuto

Takasugi

et al. 2010

The near-field structure of strongly buoyant jet issuing from a square nozzle at low Froude and Reynolds numbers is studied by using LIF flow visualization and time-resolved scanning PIV. These experimental techniques allow the visualization of unsteady three-dimensional flow phenomenon occurring in the near-field of strongly buoyant jet. It is found that the buoyant jet is unstable to the positive buoyancy forces, which promote the inflow motion near the nozzle exit. The surrounding low temperature fluid moves into the nozzle inside along the nozzle corner and mixes with the high temperature fluid deep into the nozzle. Then, the flow pattern inside the nozzle becomes highly complex to promote the laminar to turbulent transition of the jet. The statistical flow characteristics of the strongly buoyant jet are evaluated from the scanning PIV measurement, and the result indicates the presence of axisymmetric distributions of mean flow and velocity fluctuations in the circle of diameter equal to the square side of the nozzle.