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Papers by Djalal Merkoune

Journal of Physics: Conference Series, 2011

ABSTRACT We report experimental results on influence of air bubbles curtain on wave breaking. It ... more ABSTRACT We report experimental results on influence of air bubbles curtain on wave breaking. It was found that position of wave breaking point depends on bubble concentration in water. It was revealed that the effect of wave breaking is very sensitive to the concentration of air bubbles which are situated near free surface of water. We showed that small concentration of artificially created bubbles do not lead to additional dissipation of energy in surface waves but change sufficiently the position of breaking point. This phenomenon could synchronize the breaking of irregular surface waves in the ocean and lead to the generation of spatially inhomogeneous turbulence in the upper layer of the ocean.

Journal of Animal Science, 2017

A study was conducted to evaluate the accuracy of the equation estimating body lipid-to-body prot... more A study was conducted to evaluate the accuracy of the equation estimating body lipid-to-body protein ratio (BLBP) of growing pigs proposed in the NRC (2012) model. In this model, BLBP is set as initial condition for growing finishing pigs to predict body composition from BW and is described by the equation BLBP = (0.305 − 0.000875 × PD Max) × BW 0.45 , in which PD Max (g/d) is the maximum protein deposition potential of the animal. The assessment was done using body composition data of 57 growing barrows (28 ± 2 kg BW) of a terminal cross line. The body protein and lipid content was measured using dual energy absorptiometry. The mean protein deposition of barrows from 25 to 55 kg BW (n = 19) and from 70 to 100 kg BW (n = 20) from the same batch was used to extrapolate the representative PD curve of the barrows as described by the NRC (2012). The maximum value from the curve was used as PD Max (190 g) in the BLBP equation. All the animals were fed at or above recommended nutrient requirements. The residual error analysis for BLBP prediction by the NRC equation revealed a root mean squared prediction errors (RMSPE; as a percentage of observed mean) of 35%. The average BLBP predicted value was 0.62, whereas the average observed value was 0.94. Most of the errors (89%) were due to mean bias and some were due to slope bias (9%). These errors indicate that the NRC-proposed BLBP equation underestimates BLBP. When the default PD Max (145 g/d) for growing barrows was used for BLBP prediction, the RMSPE was reduced to 19%, with 60% of errors partitioned to mean bias and 33% to slope bias. It was therefore concluded that the BLBP equation used in the NRC 2012 model underestimates body lipid-to-body protein ratio in pigs with high genetic potential for protein deposition.

XIIIèmes JNGCGC, Dunkerque, 2014

XIIèmes Journées, Cherbourg, 2012

We report experimental results on influence of air bubbles curtain on wave breaking realized in e... more We report experimental results on influence of air bubbles curtain on wave breaking realized in experi mental wave flume with water depth of 45 cm. It was found that position of wave breaking point depends on bubble d ensity in water. It was revealed that the effect of wave breaking is very sensitive to the concentration of air bubbles near free surface of water. We showed that a small concentration of arti ficially created bubbles do not lead to additional dissipation of energy in surface waves but change sufficiently the position of wave breaking point. To understand phy sical mechanisms of bubbles - wave breaking interaction, we studied the velocity of bubbles using double-tip conductivity probes which is based on the electrical resistance, and vorticity fields of flow caused by rising bubb les using Acoustic Doppler Velocimetry (ADV).

Nous presentons les resultats experimentaux sur l'influence des bulles d'air sur le defer... more Nous presentons les resultats experimentaux sur l'influence des bulles d'air sur le deferlement realise en canal a houle experimental avec une profondeur d'eau de 45 cm. Il a ete constate que la situation du point de deferlement depend de la densite des bulles dans l'eau. Il a ete revele que l'effet de deferlement est tres sensible a la concentration de bulles d'air pres de la surface libre de l'eau. Nous avons montre qu'une faible concentration de bulles creees artificiellement ne conduit pas a une dissipation d'energie supplementaire dans les vagues de surface, mais change suffisamment la position du point de deferlement. Pour comprendre les mecanismes physiques de l’interaction bulles d’air/deferlement, nous avons etudie la vitesse des bulles a l'aide de sondes de conductivite a double pointe qui sont basees sur la resistance electrique, et les champs de vorticite de l'ecoulement causes par les bulles d’air en utilisant Acoustic Doppler...

Natural Hazards and Earth System Sciences, Nov 19, 2013

Formation of freak waves resulting from the wave packets propagating in finite water depth on the... more Formation of freak waves resulting from the wave packets propagating in finite water depth on the background of a current is studied experimentally and numerically. In the experiment, the freak waves appear as a result of dispersion focusing of wave train excited by wave maker with modulated frequency. The space evolution of the frequency modulated train is studied in numerical simulations. We showed that in the water of finite depth, a distance of focusing increases and amplitude in the focal point decreases in comparison with infinite water depth. Experimental results are in good agreement with numerical simulations if wave breaking of surface waves does not occur.

Advances and Applications in Fluid Mechanics, 2016

XIIIèmes JNGCGC, Dunkerque, 2014

XIIèmes Journées, Cherbourg, 2012

Journal of Physics: Conference Series, 2011

ABSTRACT We report experimental results on influence of air bubbles curtain on wave breaking. It ... more ABSTRACT We report experimental results on influence of air bubbles curtain on wave breaking. It was found that position of wave breaking point depends on bubble concentration in water. It was revealed that the effect of wave breaking is very sensitive to the concentration of air bubbles which are situated near free surface of water. We showed that small concentration of artificially created bubbles do not lead to additional dissipation of energy in surface waves but change sufficiently the position of breaking point. This phenomenon could synchronize the breaking of irregular surface waves in the ocean and lead to the generation of spatially inhomogeneous turbulence in the upper layer of the ocean.

Journal of Animal Science, 2017

A study was conducted to evaluate the accuracy of the equation estimating body lipid-to-body prot... more A study was conducted to evaluate the accuracy of the equation estimating body lipid-to-body protein ratio (BLBP) of growing pigs proposed in the NRC (2012) model. In this model, BLBP is set as initial condition for growing finishing pigs to predict body composition from BW and is described by the equation BLBP = (0.305 − 0.000875 × PD Max) × BW 0.45 , in which PD Max (g/d) is the maximum protein deposition potential of the animal. The assessment was done using body composition data of 57 growing barrows (28 ± 2 kg BW) of a terminal cross line. The body protein and lipid content was measured using dual energy absorptiometry. The mean protein deposition of barrows from 25 to 55 kg BW (n = 19) and from 70 to 100 kg BW (n = 20) from the same batch was used to extrapolate the representative PD curve of the barrows as described by the NRC (2012). The maximum value from the curve was used as PD Max (190 g) in the BLBP equation. All the animals were fed at or above recommended nutrient requirements. The residual error analysis for BLBP prediction by the NRC equation revealed a root mean squared prediction errors (RMSPE; as a percentage of observed mean) of 35%. The average BLBP predicted value was 0.62, whereas the average observed value was 0.94. Most of the errors (89%) were due to mean bias and some were due to slope bias (9%). These errors indicate that the NRC-proposed BLBP equation underestimates BLBP. When the default PD Max (145 g/d) for growing barrows was used for BLBP prediction, the RMSPE was reduced to 19%, with 60% of errors partitioned to mean bias and 33% to slope bias. It was therefore concluded that the BLBP equation used in the NRC 2012 model underestimates body lipid-to-body protein ratio in pigs with high genetic potential for protein deposition.

XIIIèmes JNGCGC, Dunkerque, 2014

XIIèmes Journées, Cherbourg, 2012

We report experimental results on influence of air bubbles curtain on wave breaking realized in e... more We report experimental results on influence of air bubbles curtain on wave breaking realized in experi mental wave flume with water depth of 45 cm. It was found that position of wave breaking point depends on bubble d ensity in water. It was revealed that the effect of wave breaking is very sensitive to the concentration of air bubbles near free surface of water. We showed that a small concentration of arti ficially created bubbles do not lead to additional dissipation of energy in surface waves but change sufficiently the position of wave breaking point. To understand phy sical mechanisms of bubbles - wave breaking interaction, we studied the velocity of bubbles using double-tip conductivity probes which is based on the electrical resistance, and vorticity fields of flow caused by rising bubb les using Acoustic Doppler Velocimetry (ADV).

Nous presentons les resultats experimentaux sur l'influence des bulles d'air sur le defer... more Nous presentons les resultats experimentaux sur l'influence des bulles d'air sur le deferlement realise en canal a houle experimental avec une profondeur d'eau de 45 cm. Il a ete constate que la situation du point de deferlement depend de la densite des bulles dans l'eau. Il a ete revele que l'effet de deferlement est tres sensible a la concentration de bulles d'air pres de la surface libre de l'eau. Nous avons montre qu'une faible concentration de bulles creees artificiellement ne conduit pas a une dissipation d'energie supplementaire dans les vagues de surface, mais change suffisamment la position du point de deferlement. Pour comprendre les mecanismes physiques de l’interaction bulles d’air/deferlement, nous avons etudie la vitesse des bulles a l'aide de sondes de conductivite a double pointe qui sont basees sur la resistance electrique, et les champs de vorticite de l'ecoulement causes par les bulles d’air en utilisant Acoustic Doppler...

Natural Hazards and Earth System Sciences, Nov 19, 2013

Formation of freak waves resulting from the wave packets propagating in finite water depth on the... more Formation of freak waves resulting from the wave packets propagating in finite water depth on the background of a current is studied experimentally and numerically. In the experiment, the freak waves appear as a result of dispersion focusing of wave train excited by wave maker with modulated frequency. The space evolution of the frequency modulated train is studied in numerical simulations. We showed that in the water of finite depth, a distance of focusing increases and amplitude in the focal point decreases in comparison with infinite water depth. Experimental results are in good agreement with numerical simulations if wave breaking of surface waves does not occur.

Advances and Applications in Fluid Mechanics, 2016

XIIIèmes JNGCGC, Dunkerque, 2014

XIIèmes Journées, Cherbourg, 2012