The Experts below are selected from a list of 69 Experts worldwide ranked by ideXlab platform

Tongmiin Liou - One of the best experts on this subject based on the ideXlab platform.

  • Turbulent Flows in 2-D and 3-D Simulated SDR Combustors
    Engineering Turbulence Modelling and Experiments, 2014
    Co-Authors: Tongmiin Liou, Y Y Wu
    Abstract:

    The mean velocity and turbulence quantities in simulated 2-D and 3-D SDR combustor flowfields were measured by using a two-component laser Doppler velocimetry system. The Reynolds number, based on the combustor height and bulk mean velocity, and momentum ratio of axial-inlet to Side-Inlets were 4.56×104 and 0.11, respectively, for the 2-D flowfield; 5.92×104 and 0.20 for the 3-D flowfield. It is found that the well-organized dome vortices and separating bubbles in the 2-D flow are absent in the 3-D flow. To provide a reference for turbulence modelling, the 2-D flow is also characterized in terms of the turbulent structure parameter. In addition, the penetration of the axial jet through the Side-inlet jets and the mixing of the axial-inlet with the Side-inlet streams are documented.

  • Self-Sustained Flow Oscillation in a Ducted Combustor with Multiple Inlets
    AIAA Journal, 1995
    Co-Authors: Tongmiin Liou, Y Y Wu
    Abstract:

    The impingement flowfield in a ducted combustor with one axial inlet and dual Side Inlets was characterized qualitatively by smoke flow visualization as well as quantitatively by laser Doppler velocimetry and microphone measured velocity and wall pressure spectral characteristics, respectively. The baseline momentum ratio MR of the axial inlet to Side Inlets was chosen to be 0.27. In this case, a resonant feedback frequency of 365 Hz, which prevailed in the entire combustor, and the second and the third harmonics, which appeared near the impingement region, were observed. The effect of MR on the flow oscillations was further studied, and the results showed that a constant Strouhal number, based on the axial inlet velocity and width, of 0.013 was found for MR < 0.94, and Reynolds number of 103-104 and the frequency of the oscillations varied linearly with the MR. From the investigation of the measured spectra, the feedback mechanism with appropriately proposed feedback distance and convective velocity, and of the chamber resonance curve, the onset of the oscillations was interpreted to be triggered by the coupling between the disturbance feedback frequency and the acoustic frequency of the chamber.

  • Turbulent flows in two-dimensional and three-dimensional simulated SDR combustors
    Experimental Thermal and Fluid Science, 1994
    Co-Authors: Tongmiin Liou, Y Y Wu
    Abstract:

    Abstract The mean velocity and turbulence quantities in simulated two-dimensional (2-D) and three-dimensional (3-D) solid-propellant ducted rocket (SDR) combustor flow fields were measured using a two-component laser-Doppler velocimetry system. The Reynolds number, based on the combustor height and bulk mean velocity and momentum ratio of the axial inlet to Side Inlets were 4.56 × 10 4 and 0.11, respectively, for the 2-D flow field and 5.92 × 10 4 and 0.20 for the 3-D flow field. It is found that the well-organized dome vortices and separating bubbles in the 2-D flow are absent in the 3-D flow. To provide a reference for turbulence modeling, the 2-D flow is also characterized in terms of turbulent structure parameter. In addition, the penetration of the axial jet through the Side-inlet jets and the mixing of the axial-inlet with the Side-inlet streams are documented.

  • Turbulent flows in a model SDR combustor
    Journal of Fluids Engineering-transactions of The Asme, 1993
    Co-Authors: Tongmiin Liou, Y Y Wu
    Abstract:

    An experimental study is reported on the isothermal flow fields in a model solid-propellant ducted rocket combustor with two opposing Side Inlets. The measurements were made by using a four-beam two-color laser-Doppler velocimeter (LDV). Three values of momentum ratio (Ma /Ms ) of the axial- to Side-inlet jet—0.025, 0.11, and 1.28—were selected to investigate their effects on the flow characteristics. The Reynolds number, based on the air density, combustor height, and bulk velocity, was 4.56 × 104 . The flow field was characterized in terms of the mean-velocity vectors and contours, joint probability functions, mean reattachment lengths, spreading rate of the axial-jet width, and Reynolds stress and turbulence kinetic energy contours. The LDV measured mean reattachment lengths were found to well agree with the corresponding flow-visualization photograph. In addition, the three Ma /Ms values provided three characteristic flows which are useful in testing the computational models. Further, correlations between the present cold-flow and previous reading-flow studies were documented in detail. It was found that from the fluid dynamic point of view Ma /Ms = 0.11 was preferable to the other two values of Ma /Ms .

  • ldv measurements of the flowfield in a simulated combustor with axial and Side Inlets
    Experimental Thermal and Fluid Science, 1992
    Co-Authors: Tongmiin Liou, Y Y Wu
    Abstract:

    Abstract The axial and transverse mean velocity and turbulence intensity components as well as Reynolds stresses and turbulent kinetic energy were measured by using a four-beam two-color laser-Doppler velocimetry (LDV) system for the isothermal flowfield of a simulated combustor that consisted of a plexiglass rectangular duct with two opposing 90° Side Inlets and one axial inlet. The Reynolds number, based on the air density, combustor height, and bulk mean velocity, was 4.56 × 10 4 . The ratio of the axial-inlet to Side-inlet jet momentum was 1.28. Various flow regions are characterized by the measured mean flow pattern. The LDV-measured mean reattachment length of the separating bubble compares fairly well with the corresponding flow visualization photograph. Moreover, the lengths needed to reach both unidirectional flow and fully developed mean flow are determined. Regions where turbulence is anisotropic and where turbulent kinetic energy and shear stresses dominate are also identified. The information presented will be useful in testing and developing combustor models in this area.

Y Y Wu - One of the best experts on this subject based on the ideXlab platform.

  • Turbulent Flows in 2-D and 3-D Simulated SDR Combustors
    Engineering Turbulence Modelling and Experiments, 2014
    Co-Authors: Tongmiin Liou, Y Y Wu
    Abstract:

    The mean velocity and turbulence quantities in simulated 2-D and 3-D SDR combustor flowfields were measured by using a two-component laser Doppler velocimetry system. The Reynolds number, based on the combustor height and bulk mean velocity, and momentum ratio of axial-inlet to Side-Inlets were 4.56×104 and 0.11, respectively, for the 2-D flowfield; 5.92×104 and 0.20 for the 3-D flowfield. It is found that the well-organized dome vortices and separating bubbles in the 2-D flow are absent in the 3-D flow. To provide a reference for turbulence modelling, the 2-D flow is also characterized in terms of the turbulent structure parameter. In addition, the penetration of the axial jet through the Side-inlet jets and the mixing of the axial-inlet with the Side-inlet streams are documented.

  • Self-Sustained Flow Oscillation in a Ducted Combustor with Multiple Inlets
    AIAA Journal, 1995
    Co-Authors: Tongmiin Liou, Y Y Wu
    Abstract:

    The impingement flowfield in a ducted combustor with one axial inlet and dual Side Inlets was characterized qualitatively by smoke flow visualization as well as quantitatively by laser Doppler velocimetry and microphone measured velocity and wall pressure spectral characteristics, respectively. The baseline momentum ratio MR of the axial inlet to Side Inlets was chosen to be 0.27. In this case, a resonant feedback frequency of 365 Hz, which prevailed in the entire combustor, and the second and the third harmonics, which appeared near the impingement region, were observed. The effect of MR on the flow oscillations was further studied, and the results showed that a constant Strouhal number, based on the axial inlet velocity and width, of 0.013 was found for MR < 0.94, and Reynolds number of 103-104 and the frequency of the oscillations varied linearly with the MR. From the investigation of the measured spectra, the feedback mechanism with appropriately proposed feedback distance and convective velocity, and of the chamber resonance curve, the onset of the oscillations was interpreted to be triggered by the coupling between the disturbance feedback frequency and the acoustic frequency of the chamber.

  • Turbulent flows in two-dimensional and three-dimensional simulated SDR combustors
    Experimental Thermal and Fluid Science, 1994
    Co-Authors: Tongmiin Liou, Y Y Wu
    Abstract:

    Abstract The mean velocity and turbulence quantities in simulated two-dimensional (2-D) and three-dimensional (3-D) solid-propellant ducted rocket (SDR) combustor flow fields were measured using a two-component laser-Doppler velocimetry system. The Reynolds number, based on the combustor height and bulk mean velocity and momentum ratio of the axial inlet to Side Inlets were 4.56 × 10 4 and 0.11, respectively, for the 2-D flow field and 5.92 × 10 4 and 0.20 for the 3-D flow field. It is found that the well-organized dome vortices and separating bubbles in the 2-D flow are absent in the 3-D flow. To provide a reference for turbulence modeling, the 2-D flow is also characterized in terms of turbulent structure parameter. In addition, the penetration of the axial jet through the Side-inlet jets and the mixing of the axial-inlet with the Side-inlet streams are documented.

  • ldv measurements of the flowfield in a simulated combustor with axial and Side Inlets
    Experimental Thermal and Fluid Science, 1992
    Co-Authors: Tongmiin Liou, Y Y Wu
    Abstract:

    Abstract The axial and transverse mean velocity and turbulence intensity components as well as Reynolds stresses and turbulent kinetic energy were measured by using a four-beam two-color laser-Doppler velocimetry (LDV) system for the isothermal flowfield of a simulated combustor that consisted of a plexiglass rectangular duct with two opposing 90° Side Inlets and one axial inlet. The Reynolds number, based on the air density, combustor height, and bulk mean velocity, was 4.56 × 10 4 . The ratio of the axial-inlet to Side-inlet jet momentum was 1.28. Various flow regions are characterized by the measured mean flow pattern. The LDV-measured mean reattachment length of the separating bubble compares fairly well with the corresponding flow visualization photograph. Moreover, the lengths needed to reach both unidirectional flow and fully developed mean flow are determined. Regions where turbulence is anisotropic and where turbulent kinetic energy and shear stresses dominate are also identified. The information presented will be useful in testing and developing combustor models in this area.

  • oscillation of impingement flow in a combustor with dual Side Inlets
    1992
    Co-Authors: Tongmiin Liou, Y Y Wu, S M Wu
    Abstract:

    The oscillation of streamwise vortices resulting from a jet-on-jet impingement in a round duct with dual rectangular Side-Inlets was investigated using the particle-tracer visualization technique for Reynolds numbers of 2000 to 26000. The results showed that the vortex patterns could be classified into three oscillation modes: clockwise, impingement, and counter-clockwise modes, and the frequency of the mode shift increased as the Reynolds number was risen.

S M Wu - One of the best experts on this subject based on the ideXlab platform.

  • oscillation of impingement flow in a combustor with dual Side Inlets
    1992
    Co-Authors: Tongmiin Liou, Y Y Wu, S M Wu
    Abstract:

    The oscillation of streamwise vortices resulting from a jet-on-jet impingement in a round duct with dual rectangular Side-Inlets was investigated using the particle-tracer visualization technique for Reynolds numbers of 2000 to 26000. The results showed that the vortex patterns could be classified into three oscillation modes: clockwise, impingement, and counter-clockwise modes, and the frequency of the mode shift increased as the Reynolds number was risen.

  • The Three-Dimensional Jet-Jet Impingement Flow in a Closed-End Cylindrical Duct
    Journal of Fluids Engineering-transactions of The Asme, 1990
    Co-Authors: Tongmiin Liou, Y.-h. Hwang, S M Wu
    Abstract:

    Experimental and theoretical studies are reported on the three-dimensional jet-jet impingement flow in a closed-end cylindrical duct with two 60-deg Side Inlets. The measurements were made using the laser-Doppler velocimeter. The Reynolds number based on the air density, duct diameter, and bulk velocity was 2.6×10 4 . The governing partial differential equations were solved numerically with the k−e turbulence model

Chris Brien - One of the best experts on this subject based on the ideXlab platform.

  • A field and laboratory investigation of kerb Side inlet pits using four media types.
    Journal of Environmental Management, 2019
    Co-Authors: Harsha Sapdhare, Baden Myers, Simon Beecham, Chris Brien, David Pezzaniti, T. Johnson
    Abstract:

    Abstract Kerb Side Inlets with adjacent leaky wells are an emerging tool to harvest stormwater and to reduce runoff volumes and peak flow rates. This is achieved by collecting the first flush runoff into kerb Side storages and infiltrating this water into the surrounding soil, thereby also reducing stormwater pollutant loadings. The hydraulic performance of the kerb Side inlet, filter media and surrounding soil are key factors in the performance of these systems. However, no field or laboratory data are currently available for the hydraulic performance of a kerb Side tree inlet pit. In this study, 12 tree inlet pits were constructed and filled with various media types including gravel, water treatment solids (a recycled waste product), sandy loam and clay to examine (1) leaky well infiltration rates (2) emptying times of the wells and (3) the well capacity (runoff storage volume) before and after runoff filtering through the wells. Using a laboratory model, the water harvesting performance of the kerb Side inlet plate was also examined for various road longitudinal slopes. Using the field and laboratory data, simulation of the well performance was undertaken using the Model for Urban Stormwater Improvement Conceptualisation (MUSIC) to assess the capacity of these systems to reduce runoff volumes at the reSidential street scale. It was hypothesised that the type of filter media used in leaky well systems has a significant impact on the infiltration rate, regardless of the native soil type through which the stormwater eventually infiltrates. The results showed that the infiltration rates of systems filled with gravel were significantly higher than for the other media types, and this was followed by water treatment solids, sandy loam and clay. The results of the MUSIC modelling indicated that 2.8% of the mean annual runoff volume in the catchment could be harvested by the systems at the case study site. It was found that selection of high infiltration rate media and regular maintenance are the key factors for maintaining long-term performance of these systems.

  • Performance of a kerb Side inlet to irrigate street trees and to improve road runoff water quality: a comparison of four media types
    Environmental Science and Pollution Research, 2018
    Co-Authors: Harsha Sapdhare, Baden Myers, Simon Beecham, Chris Brien
    Abstract:

    The TREENET inlet is an emerging water-sensitive urban design technology that consists of a novel kerb Side inlet coupled with a leaky well infiltration system. The Inlets have been retrofitted to existing roads since 2006; however, there is currently little information available on the effectiveness of these inlet and leaky well systems. This study investigated the performance of the kerb Side Inlets and leaky well system for water quality improvement prior to infiltration to native soil. The leaky wells included four filter media types, namely gravel, water treatment solids, sandy loam and clay. To compare the performance of the four filter media types, batch and column studies were performed in the laboratory. The best performance was observed using the sandy loam as a filter media, followed by clay, water treatment solids and then gravel. The selection of effective media for removal of heavy metals is important as each media type has different pollutant removal capacity, infiltration and clogging performance.

Y Y Wu - One of the best experts on this subject based on the ideXlab platform.

  • Turbulent flows in a model SDR combustor
    Journal of Fluids Engineering-transactions of The Asme, 1993
    Co-Authors: Tongmiin Liou, Y Y Wu
    Abstract:

    An experimental study is reported on the isothermal flow fields in a model solid-propellant ducted rocket combustor with two opposing Side Inlets. The measurements were made by using a four-beam two-color laser-Doppler velocimeter (LDV). Three values of momentum ratio (Ma /Ms ) of the axial- to Side-inlet jet—0.025, 0.11, and 1.28—were selected to investigate their effects on the flow characteristics. The Reynolds number, based on the air density, combustor height, and bulk velocity, was 4.56 × 104 . The flow field was characterized in terms of the mean-velocity vectors and contours, joint probability functions, mean reattachment lengths, spreading rate of the axial-jet width, and Reynolds stress and turbulence kinetic energy contours. The LDV measured mean reattachment lengths were found to well agree with the corresponding flow-visualization photograph. In addition, the three Ma /Ms values provided three characteristic flows which are useful in testing the computational models. Further, correlations between the present cold-flow and previous reading-flow studies were documented in detail. It was found that from the fluid dynamic point of view Ma /Ms = 0.11 was preferable to the other two values of Ma /Ms .

  • spectral characteristics of velocity and wall pressure in a ducted flow with dual Side and one axial Inlets
    1992
    Co-Authors: T M Liou, Y Y Wu
    Abstract:

    Abstract : The velocity and wall pressure spectral characteristics of the impingement of multiple inlet jets is a ducted flow was investigated experimentally using LDV and microphone, respectively. The baseline momentum ratio of the axial- to Side-inlet jet (MR) was chosen to be 0.27. In this case, a resonant feedback frequency of 365 Hz, which prevailed in the entire combustor, and the second and the third harmonics, which appeared near the impingement region, were observed. Also, the effect of the MR on the flow oscillations was studied and the results showed that below NR=0.94, a constant Strouhal number, based on the axial inlet velocity and width, of 0.013 was found; is other words, the frequency of the oscillations was triggered by the coupling between the disturbance feedback frequency and the acoustic frequency of the settling chambers of the Side Inlets. (Author)