Guilkey, JE
1997
Mixing Mechanisms in Turbulent Pipe Flow
Guilkey, J.E.; Kerstein, A.R.; McMurtry, P.A. and Klewicki, J.C.
Phys. Fluids, 9(3):717-23(1997). Funded by ACERC and National Science Foundation.
An experimental investigation of passive scalar mixing in turbulent pipe flow is carried out using a new non-intrusive scalar initialization technique. The measurements support a recently predicted similarity scaling of concentration spectra in flows that are unbounded in one direction. Reflecting this scaling, the scalar variance exhibits a power-law rather than exponential decay, indicating that the traditional plug-flow reactor picture of turbulent pipe-flow mixing omits key physical mechanisms.
Long-Tailed Probability Distributions in Turbulent-Pipe-Flow Mixing
Guilkey, J.E.; Kerstein, A.R.; McMurtry, P.A. and Klewicki, J.C.
Physical Review E, 56(2):1753-758(1997). Funded by ACERC and National Science Foundation.
Exponential-tailed scalar probability density functions (PDF's) are obtained by high-pass filtering scalar concentration time series measured in turbulent pipe flow. This behavior reflects the scale separation of scalar and velocity fluctuations that develops in this flow, such that the low-wave-number scalar fluctuations act as and imposed scalar gradient stirred by finer-scale wall-generated shear. This observation broadens the class of flows in which long-tailed scalar PDF's are anticipated to occur.
1996
Use of Caged Fluorescent Dyes for the Study of Turbulent Passive Scalar Mixing
Guilkey, J.E.; Gee, K.R.; McMurtry, P.A. and Klewicki, J.C.
Experiments and Fluids, 21:237-242, 1996. Funded by National Science Foundation.
The non-intrusive initialization of flow field with distinct spatially segregated scalar components represents a significant experimental difficulty. Here a new technique is described which makes possible the non-intrusive initialization of spatially binary passive scalar field in a laminar or turbulent flow field. This technique uses photoactivatable (caged) fluorescent dyes dissolved in the flow medium. The scalar field within the flow field is tagged or initialized by "uncaging" the appropriate regions with an ultraviolet excimer laser. Mixing between the tagged and untagged regions is quantified using standard laser induced florescence techniques. The method is currently being used to study mixing in a turbulent pipe flow.
Mixing Mechanisms in Turbulent Pipe Flow
Guilkey, J.E.; Kerstein, A.R.; McMurtry, P.A. and Klewicki, J.C.
Physics of Fluids, (in press), 1996. Funded by National Science Foundation.
An experimental investigation of passive scalar mixing in turbulent pipe flow is carried out using a new non-intrusive scalar initialization technique. The measurements support a recently predicted similarity scaling of concentration spectra in flows that are unbounded in one direction. Reflecting this scaling, the scalar variance exhibits a power-law rather than exponential decay, indicating that the traditional plug-flow reactor picture of turbulent pipe-flow mixing omits key physical mechanisms.
Guilkey, JE
1997
Mixing Mechanisms in Turbulent Pipe Flow
Guilkey, J.E.; Kerstein, A.R.; McMurtry, P.A. and Klewicki, J.C.
Phys. Fluids, 9(3):717-23(1997). Funded by ACERC and National Science Foundation.
An experimental investigation of passive scalar mixing in turbulent pipe flow is carried out using a new non-intrusive scalar initialization technique. The measurements support a recently predicted similarity scaling of concentration spectra in flows that are unbounded in one direction. Reflecting this scaling, the scalar variance exhibits a power-law rather than exponential decay, indicating that the traditional plug-flow reactor picture of turbulent pipe-flow mixing omits key physical mechanisms.
Long-Tailed Probability Distributions in Turbulent-Pipe-Flow Mixing
Guilkey, J.E.; Kerstein, A.R.; McMurtry, P.A. and Klewicki, J.C.
Physical Review E, 56(2):1753-758(1997). Funded by ACERC and National Science Foundation.
Exponential-tailed scalar probability density functions (PDF's) are obtained by high-pass filtering scalar concentration time series measured in turbulent pipe flow. This behavior reflects the scale separation of scalar and velocity fluctuations that develops in this flow, such that the low-wave-number scalar fluctuations act as and imposed scalar gradient stirred by finer-scale wall-generated shear. This observation broadens the class of flows in which long-tailed scalar PDF's are anticipated to occur.
1996
Use of Caged Fluorescent Dyes for the Study of Turbulent Passive Scalar Mixing
Guilkey, J.E.; Gee, K.R.; McMurtry, P.A. and Klewicki, J.C.
Experiments and Fluids, 21:237-242, 1996. Funded by National Science Foundation.
The non-intrusive initialization of flow field with distinct spatially segregated scalar components represents a significant experimental difficulty. Here a new technique is described which makes possible the non-intrusive initialization of spatially binary passive scalar field in a laminar or turbulent flow field. This technique uses photoactivatable (caged) fluorescent dyes dissolved in the flow medium. The scalar field within the flow field is tagged or initialized by "uncaging" the appropriate regions with an ultraviolet excimer laser. Mixing between the tagged and untagged regions is quantified using standard laser induced florescence techniques. The method is currently being used to study mixing in a turbulent pipe flow.
Mixing Mechanisms in Turbulent Pipe Flow
Guilkey, J.E.; Kerstein, A.R.; McMurtry, P.A. and Klewicki, J.C.
Physics of Fluids, (in press), 1996. Funded by National Science Foundation.
An experimental investigation of passive scalar mixing in turbulent pipe flow is carried out using a new non-intrusive scalar initialization technique. The measurements support a recently predicted similarity scaling of concentration spectra in flows that are unbounded in one direction. Reflecting this scaling, the scalar variance exhibits a power-law rather than exponential decay, indicating that the traditional plug-flow reactor picture of turbulent pipe-flow mixing omits key physical mechanisms.