HAL (Le Centre pour la Communication Scientifique Directe), Jun 11, 2017
International audienceSustainable sludge management is becoming a major issue for wastewater trea... more International audienceSustainable sludge management is becoming a major issue for wastewater treatment plants due to increasing urban populations and tightening environmental regulations for conventional sludge disposal methods. To address this problem, a good understanding of sludge behavior is vital to improve and optimize the current state of wastewater treatment operations. Rheology being the science that studies the deformation and flow of matter, this behavior is characterized from the sludge rheological properties. Up to now, performing these measurements is long and complex. The aim of this study is to assess the potential of Polarized Light Spectroscopy to predict the sludge’s main rheological parameter. The challenge is big as (i) sludge are very complex material (opaque and very turbid) from which it is difficult to measure a signal of high quality and as (ii) NIRS is mostly used to extract chemically related information from materials, while in this study, the objective is to predict some properties highly related to the physical structure. To overcome these issues, a specific optical setup, implementing light polarization, allowed to filter different components of the diffusely reflected light: part of the signal that has properties close to ballistic photons (i.e low scattered photons) and part of the signal that has been highly scattered, and which carries information about the materials structure. A various panel of 34 sludge samples (primary, secondary, digested, and dehydrated) was collected in different wastewatertreatment plants in France. The multiscattered signal (RMS) has been used to predict, with Partial Least Square, some of the most relevant rheological parameter: viscosity, yield stress, elastic and viscous modulii. Compared to the models built with a classical reflectance (RT), RMS offers better figures of merit (table 1). On the contrary, to predict the sludge’s dry matter, it appeared to be more relevant to use the low scattered signal (RSS), as dry matter is closely dependent to the chemical properties of the material. This study shows that even on highly opaque and turbid material such as sludge, it is possible, by using wave properties of light, to select part of the NIR signal presenting a higher correlation to physical structure of the sludge and being useful to predict sludge's rheological properties
L'utilisation de fluides au comportement rhéologique complexe (seuil d'écoulement, thixot... more L'utilisation de fluides au comportement rhéologique complexe (seuil d'écoulement, thixotropie) est de plus en plus courante dans notre quotidien. Une description globale du comportement n'est pas suffisante et c'est pourquoi ce travail se focalise sur la détermination locale des propriétés de ces matériaux complexes. Pour cela nous nous appuyons sur des méthodes optiques pour obtenir des informations sur la contrainte et la vitesse de cisaillement. Nous avons choisi d'opter pour la PIV (Particle Image Velocimetry) pour l'obtention du gradient de vitesse et la photoélasticimétrie pour la mesure de contrainte. L'emploi de ces deux techniques de mesure oblige que les fluides étudiés soient transparents et biréfringents. Nous étudions alors une solution de Milling Yellow (fluide au comportement rhéologique simple) pour valider nos techniques de mesure et des suspensions de Laponite qui sont des fluides à seuil et thixotropes. La première étape de ce travail ...
International audienceSustainable sludge management is becoming a major issue for wastewater trea... more International audienceSustainable sludge management is becoming a major issue for wastewater treatment plants due to increasing urban populations and tightening environmental regulations for conventional sludge disposal methods. To address this problem, a good understanding of sludge behavior is vital to improve and optimize the current state of wastewater treatment operations. Rheology being the science that studies the deformation and flow of matter, this behavior is characterized from the sludge rheological properties. Up to now, performing these measurements is long and complex. The aim of this study is to assess the potential of Polarized Light Spectroscopy to predict the sludge’s main rheological parameter. The challenge is big as (i) sludge are very complex material (opaque and very turbid) from which it is difficult to measure a signal of high quality and as (ii) NIRS is mostly used to extract chemically related information from materials, while in this study, the objective ...
L'utilisation de fluides au comportement rheologique complexe (seuil d'ecoulement, thixot... more L'utilisation de fluides au comportement rheologique complexe (seuil d'ecoulement, thixotropie) est de plus en plus courante dans notre quotidien. Une description globale du comportement n'est pas suffisante et c'est pourquoi ce travail se focalise sur la determination locale des proprietes de ces materiaux complexes. Pour cela nous nous appuyons sur des methodes optiques pour obtenir des informations sur la contrainte et la vitesse de cisaillement. Nous avons choisi d'opter pour la PIV (Particle Image Velocimetry) pour l'obtention du gradient de vitesse et la photoelasticimetrie pour la mesure de contrainte. L'emploi de ces deux techniques de mesure oblige que les fluides etudies soient transparents et birefringents. Nous etudions alors une solution de Milling Yellow (fluide au comportement rheologique simple) pour valider nos techniques de mesure et des suspensions de Laponite qui sont des fluides a seuil et thixotropes. La premiere etape de ce travail ...
Abstract The properties of artificial food bolus are studied by dynamic oscillatory and capillary... more Abstract The properties of artificial food bolus are studied by dynamic oscillatory and capillary rheometry as functions of bolus water content (WC), in the usual range of saliva hydration, for four cereal products: sponge cake, extruded flat bread and their counterpart enriched in legume proteins. All boluses followed the same rheological behavior characterized by (1) solid -like in the linear viscoelastic domain and (2) Herschel-Bulkley model for large shear strain. Hence, four characteristic rheological properties are determined: modulus at viscoelastic plateau, characteristic stress at transition to flow, yield stress and consistency in the flow regime. The decrease of these properties with WC was fitted by an exponential decay function, from which was extracted a coefficient α (5 = α ≤ 30), defined as a coefficient of interaction of the food with water. The values of α are of the same order of magnitude as the plasticization coefficient of starch by water. They were larger for the extruded pea based (EFP, α ≥ 15), and were lower for the sponge cake (SC, α ≤ 15). The variations for the different rheological properties are discussed in terms of matter state, envisioning bolus as a suspension of soft swellable particles. The comparison of these values with those encountered for real boluses from similar foods suggests that these results contribute to define a coefficient of interaction of food with saliva.
Motivated by the seminal work of Lord Lighthill in the sixties, we study the motion of inertial a... more Motivated by the seminal work of Lord Lighthill in the sixties, we study the motion of inertial aquatic swimmers that propels with undulatory gaits. We have uncovered the law linking the swimming velocity to the kinematics of the swimmer and the fluid properties (Nat. Phys. 2014). At high Reynolds numbers, the velocity appears to be equal to 0.4Af/(2π), where A and f are respectively the amplitude and the frequency of the oscillating fin. We have constructed a compliant biomimetic swimmer, whose muscles have been modeled through a torque distribution thanks to a servomotor. A soft polymeric material mimics the flesh and provides the flexibility. By immersing our robot into a water tunnel, we find and characterize the operating point for which the propulsive force balances the drag. We bring the first experimental proof of the former law and probe large amplitude undulations which exhibits nonlinear effects. All data collapse perfectly onto a single master curve. We investigate the r...
A robotic fish is used to test the validity of a simplification made in the context of fish locom... more A robotic fish is used to test the validity of a simplification made in the context of fish locomotion. With this artificial aquatic swimmer, we verify that the momentum equation results from a simple balance between a thrust and a drag that can be treated independently in the small amplitude regime. The thrust produced by the flexible robot is proportional to A2f2, where A and f are the respective tail-beat amplitude and oscillation frequency, irrespective of whether or not f coincides with the resonant frequency of the fish. The drag is proportional to U02, where U0 is the swimming velocity. These three physical quantities set the value of the Strouhal number in this regime. For larger amplitudes, we found that the drag coefficient is not constant but increases quadratically with the fin amplitude. As a consequence, the achieved locomotion velocity decreases, or the Strouhal number increases, as a function of the fin amplitude.
HAL (Le Centre pour la Communication Scientifique Directe), Jun 11, 2017
International audienceSustainable sludge management is becoming a major issue for wastewater trea... more International audienceSustainable sludge management is becoming a major issue for wastewater treatment plants due to increasing urban populations and tightening environmental regulations for conventional sludge disposal methods. To address this problem, a good understanding of sludge behavior is vital to improve and optimize the current state of wastewater treatment operations. Rheology being the science that studies the deformation and flow of matter, this behavior is characterized from the sludge rheological properties. Up to now, performing these measurements is long and complex. The aim of this study is to assess the potential of Polarized Light Spectroscopy to predict the sludge’s main rheological parameter. The challenge is big as (i) sludge are very complex material (opaque and very turbid) from which it is difficult to measure a signal of high quality and as (ii) NIRS is mostly used to extract chemically related information from materials, while in this study, the objective is to predict some properties highly related to the physical structure. To overcome these issues, a specific optical setup, implementing light polarization, allowed to filter different components of the diffusely reflected light: part of the signal that has properties close to ballistic photons (i.e low scattered photons) and part of the signal that has been highly scattered, and which carries information about the materials structure. A various panel of 34 sludge samples (primary, secondary, digested, and dehydrated) was collected in different wastewatertreatment plants in France. The multiscattered signal (RMS) has been used to predict, with Partial Least Square, some of the most relevant rheological parameter: viscosity, yield stress, elastic and viscous modulii. Compared to the models built with a classical reflectance (RT), RMS offers better figures of merit (table 1). On the contrary, to predict the sludge’s dry matter, it appeared to be more relevant to use the low scattered signal (RSS), as dry matter is closely dependent to the chemical properties of the material. This study shows that even on highly opaque and turbid material such as sludge, it is possible, by using wave properties of light, to select part of the NIR signal presenting a higher correlation to physical structure of the sludge and being useful to predict sludge's rheological properties
L'utilisation de fluides au comportement rhéologique complexe (seuil d'écoulement, thixot... more L'utilisation de fluides au comportement rhéologique complexe (seuil d'écoulement, thixotropie) est de plus en plus courante dans notre quotidien. Une description globale du comportement n'est pas suffisante et c'est pourquoi ce travail se focalise sur la détermination locale des propriétés de ces matériaux complexes. Pour cela nous nous appuyons sur des méthodes optiques pour obtenir des informations sur la contrainte et la vitesse de cisaillement. Nous avons choisi d'opter pour la PIV (Particle Image Velocimetry) pour l'obtention du gradient de vitesse et la photoélasticimétrie pour la mesure de contrainte. L'emploi de ces deux techniques de mesure oblige que les fluides étudiés soient transparents et biréfringents. Nous étudions alors une solution de Milling Yellow (fluide au comportement rhéologique simple) pour valider nos techniques de mesure et des suspensions de Laponite qui sont des fluides à seuil et thixotropes. La première étape de ce travail ...
International audienceSustainable sludge management is becoming a major issue for wastewater trea... more International audienceSustainable sludge management is becoming a major issue for wastewater treatment plants due to increasing urban populations and tightening environmental regulations for conventional sludge disposal methods. To address this problem, a good understanding of sludge behavior is vital to improve and optimize the current state of wastewater treatment operations. Rheology being the science that studies the deformation and flow of matter, this behavior is characterized from the sludge rheological properties. Up to now, performing these measurements is long and complex. The aim of this study is to assess the potential of Polarized Light Spectroscopy to predict the sludge’s main rheological parameter. The challenge is big as (i) sludge are very complex material (opaque and very turbid) from which it is difficult to measure a signal of high quality and as (ii) NIRS is mostly used to extract chemically related information from materials, while in this study, the objective ...
L'utilisation de fluides au comportement rheologique complexe (seuil d'ecoulement, thixot... more L'utilisation de fluides au comportement rheologique complexe (seuil d'ecoulement, thixotropie) est de plus en plus courante dans notre quotidien. Une description globale du comportement n'est pas suffisante et c'est pourquoi ce travail se focalise sur la determination locale des proprietes de ces materiaux complexes. Pour cela nous nous appuyons sur des methodes optiques pour obtenir des informations sur la contrainte et la vitesse de cisaillement. Nous avons choisi d'opter pour la PIV (Particle Image Velocimetry) pour l'obtention du gradient de vitesse et la photoelasticimetrie pour la mesure de contrainte. L'emploi de ces deux techniques de mesure oblige que les fluides etudies soient transparents et birefringents. Nous etudions alors une solution de Milling Yellow (fluide au comportement rheologique simple) pour valider nos techniques de mesure et des suspensions de Laponite qui sont des fluides a seuil et thixotropes. La premiere etape de ce travail ...
Abstract The properties of artificial food bolus are studied by dynamic oscillatory and capillary... more Abstract The properties of artificial food bolus are studied by dynamic oscillatory and capillary rheometry as functions of bolus water content (WC), in the usual range of saliva hydration, for four cereal products: sponge cake, extruded flat bread and their counterpart enriched in legume proteins. All boluses followed the same rheological behavior characterized by (1) solid -like in the linear viscoelastic domain and (2) Herschel-Bulkley model for large shear strain. Hence, four characteristic rheological properties are determined: modulus at viscoelastic plateau, characteristic stress at transition to flow, yield stress and consistency in the flow regime. The decrease of these properties with WC was fitted by an exponential decay function, from which was extracted a coefficient α (5 = α ≤ 30), defined as a coefficient of interaction of the food with water. The values of α are of the same order of magnitude as the plasticization coefficient of starch by water. They were larger for the extruded pea based (EFP, α ≥ 15), and were lower for the sponge cake (SC, α ≤ 15). The variations for the different rheological properties are discussed in terms of matter state, envisioning bolus as a suspension of soft swellable particles. The comparison of these values with those encountered for real boluses from similar foods suggests that these results contribute to define a coefficient of interaction of food with saliva.
Motivated by the seminal work of Lord Lighthill in the sixties, we study the motion of inertial a... more Motivated by the seminal work of Lord Lighthill in the sixties, we study the motion of inertial aquatic swimmers that propels with undulatory gaits. We have uncovered the law linking the swimming velocity to the kinematics of the swimmer and the fluid properties (Nat. Phys. 2014). At high Reynolds numbers, the velocity appears to be equal to 0.4Af/(2π), where A and f are respectively the amplitude and the frequency of the oscillating fin. We have constructed a compliant biomimetic swimmer, whose muscles have been modeled through a torque distribution thanks to a servomotor. A soft polymeric material mimics the flesh and provides the flexibility. By immersing our robot into a water tunnel, we find and characterize the operating point for which the propulsive force balances the drag. We bring the first experimental proof of the former law and probe large amplitude undulations which exhibits nonlinear effects. All data collapse perfectly onto a single master curve. We investigate the r...
A robotic fish is used to test the validity of a simplification made in the context of fish locom... more A robotic fish is used to test the validity of a simplification made in the context of fish locomotion. With this artificial aquatic swimmer, we verify that the momentum equation results from a simple balance between a thrust and a drag that can be treated independently in the small amplitude regime. The thrust produced by the flexible robot is proportional to A2f2, where A and f are the respective tail-beat amplitude and oscillation frequency, irrespective of whether or not f coincides with the resonant frequency of the fish. The drag is proportional to U02, where U0 is the swimming velocity. These three physical quantities set the value of the Strouhal number in this regime. For larger amplitudes, we found that the drag coefficient is not constant but increases quadratically with the fin amplitude. As a consequence, the achieved locomotion velocity decreases, or the Strouhal number increases, as a function of the fin amplitude.
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