The determination by coherent lidar of Doppler-velocity profiles in turbulent atmosphere

2003 ◽  
Author(s):  
Luan L. Gurdev ◽  
Tanja N. Dreischuh
Keyword(s):  
Turbulent Atmosphere ◽  
Velocity Profiles ◽  
Doppler Velocity ◽  
Coherent Lidar

scholarly journals A computational model-based approach for atlas construction of aortic Doppler velocity profiles for segmentation purposes

2018 ◽  
Vol 40 ◽  
pp. 23-32 ◽  
Author(s):  
Vedrana Baličević ◽  
Hrvoje Kalinić ◽  
Sven Lončarić ◽  
Maja Čikeš ◽  
Bart Bijnens
Keyword(s):  
Computational Model ◽  
Velocity Profiles ◽  
Doppler Velocity ◽  
Model Based ◽  
Atlas Construction

Statistics of a coherent lidar signal in a turbulent atmosphere

2013 ◽  
Vol 114 (2) ◽  
pp. 314-319 ◽  
Author(s):  
E. A. Shelekhova ◽  
A. P. Shelekhov
Keyword(s):  
Turbulent Atmosphere ◽  
Lidar Signal ◽  
Coherent Lidar

scholarly journals Velocity and concentration profiles of saline and turbidity currents flowing in a straight channel under quasi-uniform conditions

2014 ◽  
Vol 2 (1) ◽  
pp. 167-180 ◽  
Author(s):  
M. Stagnaro ◽  
M. Bolla Pittaluga
Keyword(s):  
Cross Sections ◽  
Longitudinal Velocity ◽  
Fixed Bed ◽  
Velocity Profiles ◽  
Doppler Velocity ◽  
Turbidity Currents ◽  
Straight Channel ◽  
Densimetric Froude Number ◽  
Vertical Coordinate ◽  
Dimensionless Velocity

Abstract. We present a series of detailed experimental observations of saline and turbidity currents flowing in a straight channel. Experiments are performed by continuously feeding the channel with a dense mixture until a quasi-steady configuration is obtained. The flume, 12 m long, is characterized by a concrete fixed bed with a uniform slope of 0.005. Longitudinal velocity profiles are measured in ten cross sections, 1 m apart, employing an ultrasound Doppler velocity profiler. We also measure the density of the mixture using a rake of siphons sampling at different heights from the bottom in order to obtain the vertical density distributions in a cross section where the flow already attained a quasi-uniform configuration. We performed 27 experiments changing the flow discharge, the fractional excess density, the character of the current (saline or turbidity) and the roughness of the bed in order to observe the consequences of these variations on the vertical velocity profiles and on the overall characteristics of the flow. Dimensionless velocity profiles under quasi-uniform flow conditions were obtained by scaling longitudinal velocity with its depth averaged value and the vertical coordinate with the flow thickness. They turned out to be influenced by the Reynolds number of the flow, by the relative bed roughness, and by the presence of sediment in suspension. Unexpectedly, the densimetric Froude number of the current turned out to have no influence on the dimensionless velocity profiles.

Experimental Study of Uniform-Shear Flow Past a Rotating Cylinder

1995 ◽  
Vol 117 (1) ◽  
pp. 62-67 ◽  
Author(s):  
Hyung Jin Sung ◽  
Chong Kuk Chun ◽  
Jae Min Hyun
Keyword(s):  
Experimental Study ◽  
Shear Flow ◽  
Measurement Data ◽  
Rotating Cylinder ◽  
Velocity Profiles ◽  
Doppler Velocity ◽  
Velocity Measurements ◽  
Mean Velocity ◽  
Uniform Shear ◽  
Uniform Shear Flow

An experimental study is made of two-dimensional uniform-shear flow (U = Uc + Gy) past a rotating cylinder of diameter D. A water-tunnel, equipped with a shear generator, was constructed. Laser-Doppler velocity measurements were undertaken to describe the wake characteristics. Data are compiled over the ranges of 600≤Re≤1,200, the shear parameter K[≡GD/Uc] up to 0.15, and the value of the cylinder rotation parameter α[≡ωD/2Uc], – 2.0≤α≤2.0. The power spectra of velocity measurements at downstream locations were analyzed to examine the vortex shedding patterns. In general, the dominant shedding frequency is shifted to a higher value as |α| and K increase. When |α| increases beyond a certain threshold value, the dominant frequency becomes less distinct. If |α| takes a value larger than around 1.5, the velocity field becomes randomized and diffuse, and the organized Karman vortex street activity weakens. The variations of the Strouhal number with K and α are described. The evolution of mean velocity profiles in the wake field is depicted. Characterizations of the velocity profiles, as K and α vary, are made based on the measurement data.

scholarly journals Dry Low Emissions Premixer CCD Modeling and Validation

1998 ◽  
Author(s):  
Harjit S. Hura ◽  
Narendra D. Joshi ◽  
Hukam C. Mongia ◽  
Jon Tonouchi
Keyword(s):  
Boundary Conditions ◽  
Computational Study ◽  
Velocity Profiles ◽  
Doppler Velocity ◽  
Reacting Flow ◽  
Combustion Dynamics ◽  
Optimization Function ◽  
Dissipation Model ◽  
Break Up ◽  
Turbulence Parameters

Computational Combustion Dynamics has been used extensively at General Electric Company for combustion applications. This paper demonstrates an application of Advanced Combustion Code to GE’s lean premixed dry low NOx emissions LM2500 and LM6000 gas turbine combustors. A methodology for anchoring the Double Annular Counter-Rotating Swirler (DACRS) exit conditions to Laser Doppler Velocity data from a reacting single cup experiment is described. The DACRS exit velocity profiles and turbulence parameters are inlet boundary conditions for the annular combustor simulation. Since over 80 per cent of the total air enters the combustor via the premixers, inaccuracies in these boundary conditions have a significant impact on the predicted flame shape, liner temperatures and emissions. The paper shows comparisons between measured and predicted velocity in a rectangular duct equipped with a single DACRS. The k-ε turbulence model and the two-step eddy break up/eddy dissipation combustion models are used to predict the reacting flow field of the natural gas/air flame. The inlet velocity profiles are developed first to match the LV data and the observed flame impingement location at nominal settings of the inlet turbulence parameters. The sum square error between measured and predicted velocity is used as the optimization function. Next, a design of experiment computational study is conducted to determine the inlet turbulence length scale and kinetic energy in order to further improve the data match. The eddy break up model is shown to be more robust than the eddy dissipation model. The eddy dissipation model resulted in slow combustion rates, and high fuel and carbon monoxide emissions.

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