Experimental and Numerical Investigations of a Turbulent Flow Behavior in Isolated and Nonisolated Conical Diffusers

2011 ◽  
Vol 133 (1) ◽  
Author(s):  
F. Aloui ◽  
E. Berrich ◽  
D. Pierrat
Keyword(s):  
Turbulent Flow ◽  
Flow Behavior ◽  
Piv Measurements ◽  
Numerical Investigations ◽  
Image Velocimetry ◽  
Sst Model ◽  
Proper Orthogonal ◽  
Hydraulic Circuits

In some industrial processes, and especially in agrofood industries, the cleaning in place mechanism used for hydraulic circuits plays an important role. This process needs a good knowledge of the hydrodynamic flows to determinate the appropriate parameters that assure a good cleaning of these circuits without disassembling them. Generally, different arrangements are present in these hydraulic circuits, such as expansions, diffusers, and elbows. The flow crossing these singularities strongly affects the process of cleaning in place. This work is then a contribution to complete recent studies of “aliments quality security” project to ameliorate the quality of the cleaning in place. It presents experimental and numerical investigations of a confined turbulent flow behavior across a conical diffuser (2α=16 deg). The role of a perturbation caused by the presence of an elbow in the test section, upstream of the progressive enlargement, was studied. The main measurements were the static pressure and the instantaneous velocity fields using the particle image velocimetry (PIV). Post-processing of these PIV measurements were adopted using the Γ2 criterion for the vortices detection and the proper orthogonal decomposition (POD) technique to extract the most energetic modes contained in the turbulent flow and to the turbulent flow filtering. A database has been also constituted and was used to test the validity of the most models of turbulence, and in particular, a variant of the shear stress transport (SST) model.

Experimental and Numerical Investigations of a Turbulent Flow Behaviours in Isolated and Non Isolated Conical Diffusers

2009 ◽  
Author(s):  
F. Aloui ◽  
E. Berrich ◽  
D. Pierrat
Keyword(s):  
Turbulent Flow ◽  
Particle Image ◽  
Static Pressure ◽  
Flow Behavior ◽  
Piv Measurements ◽  
Image Velocimetry ◽  
Sst Model ◽  
Proper Orthogonal ◽  
Progressive Enlargement

This work presents an experimental and numerical investigation of a confined turbulent flow behavior across a conical diffuser (2α = 16°). The role of a perturbation caused by the presence of an elbow in the test-section, upstream of the progressive enlargement, was studied. The main measurements were the static pressure, and the instantaneous velocity fields using the Particle Image Velocimetry (PIV). Post-processing of these PIV measurements were adopted using the Γ2 criterion for the vortices detection, and the Proper Orthogonal Decomposition (POD) technique to extract the most energetic modes contained in the turbulent flow and to the turbulent flow filtering. A data base has been also constituted, and was used to test the validity of the most models of turbulence, and in particular, a variant of the SST model.

Determination of Flow Structure in a Tube Array by Particle Image Velocimetry

2011 ◽  
Author(s):  
Njuki Mureithi ◽  
Claude Masabarakiza
Keyword(s):  
Particle Image Velocimetry ◽  
Flow Structure ◽  
Particle Image ◽  
Flow Behavior ◽  
Bubbly Flow ◽  
Large Area ◽  
Two Phase ◽  
Piv Measurements ◽  
Void Fractions ◽  
Image Velocimetry

Particle Image Velocimetry (PIV) presents a possible approach to measuring two-phase flow parameters over a large area, leading to a snap shot of flow behavior in complex geometries such as tube bundles. Tests have been conducted in a 2m long wavy wall channel simulating the open lane within a rotated triangular array. The results show that liquid phase PIV measurements must be limited to very low void fractions. On the other hand, much information can be gained from the gas phase data. The details of the flow structure within the array are revealed. Current measurements, performed in the bubbly flow regime, show that even in this regime, the flow structure is significantly non-uniform and complex. Bubble diameters have been found to be strongly dependent on flow velocity; the effect of turbulence shear at high flow rates breaking up the bubbles to smaller sizes. The PIV measurements yield the complete averaged velocity vector field in the measurement region. The velocity profiles across the measurement section are also obtained. The non-uniform profiles show the challenges associated with attempts to estimate average void fractions and slip ratios in the array.

Vortex Identification Study of a Turbulent Cavity Flow

2018 ◽  
Author(s):  
Khaled J. Hammad
Keyword(s):  
Particle Image ◽  
Vortex Identification ◽  
Cavity Depth ◽  
Piv Measurements ◽  
Vortical Structures ◽  
Image Velocimetry ◽  
Flow Features ◽  
Shallow Cavity ◽  
Pod Analysis ◽  
Proper Orthogonal

A combined vortex identification and Proper Orthogonal Decomposition (POD) analysis is applied to high-resolution Particle Image Velocimetry (PIV) measurements of a turbulent flow past an open shallow cavity. The PIV measurements, at a cavity depth based Reynolds number of 42,000, capture the flow structure and turbulence, upstream, over, and downstream an open cavity having a length-to-depth ratio of four. Vorticity and second invariant Q of the velocity gradient tensor analysis are used to identify the vortical structures and the overall flow field features. POD analysis is applied to the vorticity and Q fields to identify the most energetic vortical structures and flow features. The results demonstrate the superiority of the combined Q-criterion and POD analysis in identifying distinct vortical structures and their evolution.

Cognitive Health Counseling 40+

2013 ◽  
Vol 21 (1) ◽  
pp. 24-33 ◽  
Author(s):  
Anne Eschen ◽  
Franzisca Zehnder ◽  
Mike Martin
Keyword(s):  
Outcome Variable ◽  
Pilot Phase ◽  
Subjective Memory ◽  
Cognitive Health ◽  
Health Counseling ◽  
Agents Of Change ◽  
Main Outcome Variable ◽  
Further Development

This article introduces Cognitive Health Counseling 40+ (CH.CO40+), an individualized intervention that is conceptually based on the orchestration model of quality-of-life management ( Martin & Kliegel, 2010 ) and aims at improving satisfaction with cognitive health in adults aged 40 years and older. We describe the theoretically deduced characteristics of CH.CO40+, its target group, its multifactorial nature, its individualization, the application of subjective and objective measures, the role of participants as agents of change, and the rationale for choosing participants’ satisfaction with their cognitive health as main outcome variable. A pilot phase with 15 middle-aged and six older adults suggests that CH.CO40+ attracts, and may be particularly suitable for, subjective memory complainers. Implications of the pilot data for the further development of the intervention are discussed.

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