[ Augmenter le coefficient de Strickler par la technique de réduction de la traînée dans les écoulements à surface libre ]
Volume 24, Issue 1, August 2018, Pages 1–8
Walid Bouchenafa1, Arnaud Lefevre2, and Bernard Quillien3
1 SNF SAS, ZAC de Milieux, Rue Adriene Bolland, 42160. Andrézieux-Bouthéon, France
2 SNF SAS, ZAC de Milieux, Rue Adriene Bolland, 42160. Andrézieux-Bouthéon, France
3 SNF SAS, ZAC de Milieux, Rue Adriene Bolland, 42160. Andrézieux-Bouthéon, France
Original language: French
Copyright © 2018 ISSR Journals. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
The drag reduction method by polymer additives is generally used to reduce friction losses in pipes over long-distances. The interactions between the polymer and the turbulent flow structures tend to change the velocity profile close to the walls by adding an elastic sub-layer between the viscous layer and the logarithmic zone of the boundary layer. This new sub-layer prevents the destabilization of the boundary layer. The gain in linear head losses can reach up to 80%, depending on the roughness of the walls and the concentration of the polymers. The application of this technique to sewer networks and the considerable effect on the reduction of water depth led us to study experimentally the drag reduction in an open- channel flows. Two measurement campaigns are performed on a laboratory flume for different discharges and several polymer concentrations. The surface flow velocities are measured by the LSPIV (Large Scale Particle Image Velocimetry) technique before and after the polymer injection. Backwater curves will be represented for smooth and rough flume walls. The addition of polymers even at low concentrations causes a sharp reduction in friction with a Strickler coefficient increased to 45% and 37% respectively for smooth and rough wall configurations and a decrease in water depth up to 17%. The drag reduction method by adding polymers seems to be a promising technique for limiting freshet levels and controlling river floods.
Author Keywords: Uniform flow, friction, polymers, flood, boundary layer, LSPIV, flood risk.
Volume 24, Issue 1, August 2018, Pages 1–8
Walid Bouchenafa1, Arnaud Lefevre2, and Bernard Quillien3
1 SNF SAS, ZAC de Milieux, Rue Adriene Bolland, 42160. Andrézieux-Bouthéon, France
2 SNF SAS, ZAC de Milieux, Rue Adriene Bolland, 42160. Andrézieux-Bouthéon, France
3 SNF SAS, ZAC de Milieux, Rue Adriene Bolland, 42160. Andrézieux-Bouthéon, France
Original language: French
Copyright © 2018 ISSR Journals. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
The drag reduction method by polymer additives is generally used to reduce friction losses in pipes over long-distances. The interactions between the polymer and the turbulent flow structures tend to change the velocity profile close to the walls by adding an elastic sub-layer between the viscous layer and the logarithmic zone of the boundary layer. This new sub-layer prevents the destabilization of the boundary layer. The gain in linear head losses can reach up to 80%, depending on the roughness of the walls and the concentration of the polymers. The application of this technique to sewer networks and the considerable effect on the reduction of water depth led us to study experimentally the drag reduction in an open- channel flows. Two measurement campaigns are performed on a laboratory flume for different discharges and several polymer concentrations. The surface flow velocities are measured by the LSPIV (Large Scale Particle Image Velocimetry) technique before and after the polymer injection. Backwater curves will be represented for smooth and rough flume walls. The addition of polymers even at low concentrations causes a sharp reduction in friction with a Strickler coefficient increased to 45% and 37% respectively for smooth and rough wall configurations and a decrease in water depth up to 17%. The drag reduction method by adding polymers seems to be a promising technique for limiting freshet levels and controlling river floods.
Author Keywords: Uniform flow, friction, polymers, flood, boundary layer, LSPIV, flood risk.
Abstract: (french)
La technique de réduction de la traînée par l’ajout des polymères est généralement appliquée pour réduire les frottements dans les écoulements en charge à grande distance. Les interactions entre le polymère et les structures turbulentes de l’écoulement ont tendance de modifier le profil de vitesse à proximité de la paroi par la mise en place d’une sous couche élastique entre la couche visqueuse et la zone logarithmique de la couche limite. Cette nouvelle sous couche empêche la déstabilisation de la couche limite. Le gain en perte de charge linéaire peut atteindre jusqu’à 80 % en fonction de la rugosité des parois et la concentration des polymères. L’application de cette technique dans un réseau d’assainissement et l’effet considérable sur la diminution de la hauteur d’eau nous a conduit à étudier expérimentalement la réduction de la traînée dans un canal à ciel- ouvert. Deux campagnes de mesures sont effectuées sur un canal en laboratoire pour différents débits d’écoulement et plusieurs concentrations des polymères. Les vitesses de surface de l’écoulement sont mesurées par la technique LSPIV avant et après l’injection des polymères. Les profils de hauteur d’eau seront représentés pour les parois en mode lisses et rugueuse. L’ajout des polymères même à des faibles concentrations provoque une forte diminution de frottement, avec un coefficient de Strickler augmenté à 45 % et 35% respectivement pour les configurations des parois en mode lisse et rugueuse et une baisse de niveau d’écoulement jusqu’au 17 %. La méthode de réduction de la traînée par l’addition des polymères semble finalement être une technique prometteuse pour limiter l’impact des inondations des rivières.
Author Keywords: écoulement uniforme, frottement, polymères, risque d’inondation, crue, polyacrylamide, couche limite, LSPIV.
How to Cite this Article
Walid Bouchenafa, Arnaud Lefevre, and Bernard Quillien, “Increasing Strickler coefficient by the drag reduction technique in open-channel flows,” International Journal of Innovation and Applied Studies, vol. 24, no. 1, pp. 1–8, August 2018.
