An effect of entrance length on development of velocity profile in channel of millimeter dimensions

Jašíková, Darina; Kotek, Michal; Kopecký, Václav

doi:10.1063/1.4953712

Cited by 9 publications

(6 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Theoretically, the fluid flow along the vertical tube can be divided into three parts: the entrance flow region, the fully developed flow region, and the uniform flow region (downstream of the asymptotic limit). The entrance flow region, including both the thermal and hydrodynamic entrance regions, is vitally important for heat and mass transfer in a gas–liquid contactor, especially for lab scale apparatus . In addition, it can increase the pressure drag and create skin friction drag which affects the characteristics of the flow.…”

Section: Introductionmentioning

confidence: 99%

A study of film thickness and hydrodynamic entrance length in liquid laminar film flow along a vertical tube

et al. 2018

View full text Add to dashboard Cite

The liquid film thickness and hydrodynamic entrance length in a vertical tube was studied experimentally and numerically. Measurements using distilled water, 30 wt % MEA and 40 wt % sugar solutions were carried out to investigate the effects of liquid flow rate on the formation of the liquid film. The experimental results validate the new Navier-Stokes based equation in cylindrical coordinates (Eq. 16) and the volume of fluid (VOF) model giving a competitively high prediction of the liquid film thickness especially in the low Reynolds number region. In addition, a new empirical model and an improved minimal surface model have been first proposed for calculation of the hydrodynamic entrance length, with a relatively reasonable average absolute relative deviation (AARD) of 3.03% and 6.83%, respectively. Furthermore, the effects of the hydrodynamic entry length on the gas-liquid interfacial area calculated by the improved minimal surface model were comprehensively studied, and can be ignored if the ratio of the liquid film length (y) and the hydrodynamic entrance length (k E ) is lower than 10. However, it should be noted that the hydrodynamic entrance length cannot be ignored in packed columns in which the liquid flow is very complex due to the packings with different structures and materials.

show abstract

Section: Introductionmentioning

confidence: 99%

A study of film thickness and hydrodynamic entrance length in liquid laminar film flow along a vertical tube

et al. 2018

View full text Add to dashboard Cite

show abstract

“…[2] We elongated the entering distance to avoid the flow instabilities up to 1 m. The entering distance corresponds to 100times of channel widths. The water channel was fulfilled with water avoiding the bubbles.…”

Section: Resultsmentioning

confidence: 99%

“…[1,2] There was developed the a method for analysis of the flow and the air film using the lighting in volume, visualization with CCD camera and microscope lens, optical filters based on defined depth of field measuring plane. [1,2] The next step was the experimental confirmation of theoretical assumptions about the nature of the air film on commercially used materials that have already been tested in hydraulic equipment -hydraulic pumps CKD Blansko. From industrial requirements resulted question, how is the air film depending on the roughness of the base material.…”

Section: Introductionmentioning

confidence: 99%

The interaction between fluid flow and ultra-hydrophobic surface in mini channel

et al. 2017

View full text Add to dashboard Cite

Abstract. Interaction of liquid with ultra-hydrophobic surface is accompanied by creation of layer of air. The effect of the air film has a potential of use in industry in many applications. The quality of the surface is influenced by matrix roughness, the character of physical or chemical cover. There was developed a method for analysis of the liquid flow and the air film using the lighting in volume, visualization with CCD camera and long distance microscope, and optical filters. There were prepared four stainless steel samples of inner channel of dimensions (80 x 8 x 8) mm and initial surface roughness Ra 0.33, Ra 1.0, Ra 2.0, and Ra 2.2. The inner channel was treated with plasma and commercial hydrophobic coating Greblon (WEILBURGER Coatings GmbH). There was realized study focused on the liquid flow velocity profile close to the air film. There are present results for laminar, transient and turbulent flows. The study also estimated the air film thickness depending on the Re number. The knowledge of the air film behaviour helps applied suitable degree of processing and cover for the target application.

show abstract

“…We measure air flow in an empty measurement section of length 400 mm and cross-sectional size 125 × 125 mm of open low-speed wind tunnel with maximum velocity up to 34 m/s. By using the Stereo Particle Image Velocimetry (PIV) technique [10,11] we measure all three components of velocity in a small area at the open end of the tunnel. to the weak in-plane motions than the usual 90° setup).…”

Section: Description Of Experimentsmentioning

confidence: 99%

Influence of secondary flow corner vortex to boundary layer in a channel flow

Duda

Bém

Kovařík

et al. 2019

38th Meeting of Departments of Fluid Mechanics and Thermodynamics

View full text Add to dashboard Cite

Boundary layer in developing channel flow of air is experimentally studied by using the Stereo Particle Image Velocimetry (PIV) technique. The measurement is performed at fixed distance 400 mm from the channel inlet and the Reynolds number (based on the channel length, i.e. the distance from the boundary layer origin) is controlled via the imposed velocity. Re ranges from 8•10 4 to 8•10 5 .The displacement boundary layer thickness δ* varies from 1.7 to 2.5 mm while the momentum one θ from 0.9 to 1.3 mm. It is found, that the critical Reynolds number of transition to turbulence of the boundary layer is lowered by the vicinity of the other perpendicular wall of the square channel; more accurately -it is accelerated by the larger-scale secondary flow, which results into turbulence at slightly lower Reynolds numbers. The laminar-turbulent transition is first apparent on the profiles of the turbulent kinetic energy, later on the velocity profiles. The mechanism might be probably such, that the turbulent flow structures generated in the secondary flow in the corner via Richardson energy transfer mechanism migrate into the laminar boundary layer. While the largescale structures cannot feed from the limited-size boundary layer, the smaller ones can strengthen there.

show abstract

An effect of entrance length on development of velocity profile in channel of millimeter dimensions

Cited by 9 publications

References 6 publications

A study of film thickness and hydrodynamic entrance length in liquid laminar film flow along a vertical tube

A study of film thickness and hydrodynamic entrance length in liquid laminar film flow along a vertical tube

The interaction between fluid flow and ultra-hydrophobic surface in mini channel

Influence of secondary flow corner vortex to boundary layer in a channel flow

Contact Info

Product

Resources

About