The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
C. Clanet - One of the best experts on this subject based on the ideXlab platform.
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Hysteretic Wave Drag in shallow water
Physical Review Fluids, 2020Co-Authors: G. Benham, Michael Benzaquen, R Bendimerad, C. ClanetAbstract:During motion from deep to shallow water, multiple equilibria may emerge, each with identical Drag. In this study, we show experimentally that the same Drag force may be experienced at several different speeds of body motion in shallow water, and that this can be explained by a localised amplification of the Wave Drag near the shallow Wave speed. Whilst Wave Drag in shallow water has been predicted with varying degrees of accuracy by several inviscid models, the bifurcation properties have not yet been discussed. Here, we address the nonlinear dynamics by considering the quasi-steady motion of a body between deep and shallow water, where the depth is slowly varying. In particular, we illustrate possible hysteresis routes between coexisting equilibrium states that have significantly different velocities, presenting interesting implications for naval and racing applications.
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Wave Drag on asymmetric bodies
Journal of Fluid Mechanics, 2019Co-Authors: G. Benham, J. Boucher, R. Labbe, Michael Benzaquen, C. ClanetAbstract:An asymmetric body with a sharp leading edge and a rounded trailing edge produces a smaller Wave disturbance moving forwards than backwards, and this is reflected in the Wave Drag coefficient. This experimental fact is not captured by Michell's theory for Wave Drag (Michell Lond. Edinb. Dubl. Phil. Mag. J. Sci., vol. 45 (272), 1898, pp. 106-123). In this study, we use a tow-tank experiment to investigate the effects of asymmetry on Wave Drag, and show that these effects can be replicated by modifying Michell's theory to include the growth of a symmetry-breaking boundary layer. We show that asymmetry can have either a positive or a negative effect on Drag, depending on the depth of motion and the Froude number.
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Wave Drag on asymmetric bodies
Journal of Fluid Mechanics, 2019Co-Authors: G. Benham, R. Labbe, Michael Benzaquen, Jean-philippe Boucher, C. ClanetAbstract:An asymmetric body with a sharp leading edge and a rounded trailing edge produces a smaller Wave disturbance moving forwards than backwards, and this is reflected in the Wave Drag coefficient. This experimental fact is not captured by Michell's theory for Wave Drag (Michell 1898). In this study, we use a tow-tank experiment to investigate the effects of asymmetry on Wave Drag, and show that these effects can be replicated by modifying Michell's theory to include the growth of a symmetry-breaking boundary layer. We show that asymmetry can have either a positive or a negative effect on Drag, depending on the depth of motion and the Froude number.
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Wave Drag on a submerged sphere
Physics of Fluids, 2015Co-Authors: Adrien Benusiglio, Frédéric Chevy, Elie Raphaël, C. ClanetAbstract:We measure the Wave Drag acting on fully submerged spheres as a function of their depth and velocity, with an apparatus that measures only the component of the Drag due to the proximity of the free surface. We observe that close to the surface the Wave Drag is of the order of the hydrodynamic Drag. In our range of study, the measured force is more than one order smaller than predictions based on linear response. In order to investigate this discrepancy, we measure the amplitude of the Waves at the origin of the Wave Drag, comparing the measurement with a theoretical model. The model captures the measurements at “large depth” but the Wave’s amplitude saturates at “small depth,” an effect that partially accounts for the difference between the predicted and measured Wave Drag.
G. Benham - One of the best experts on this subject based on the ideXlab platform.
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Hysteretic Wave Drag in shallow water
Physical Review Fluids, 2020Co-Authors: G. Benham, Michael Benzaquen, R Bendimerad, C. ClanetAbstract:During motion from deep to shallow water, multiple equilibria may emerge, each with identical Drag. In this study, we show experimentally that the same Drag force may be experienced at several different speeds of body motion in shallow water, and that this can be explained by a localised amplification of the Wave Drag near the shallow Wave speed. Whilst Wave Drag in shallow water has been predicted with varying degrees of accuracy by several inviscid models, the bifurcation properties have not yet been discussed. Here, we address the nonlinear dynamics by considering the quasi-steady motion of a body between deep and shallow water, where the depth is slowly varying. In particular, we illustrate possible hysteresis routes between coexisting equilibrium states that have significantly different velocities, presenting interesting implications for naval and racing applications.
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Hysteretic Wave Drag in shallow water
'American Physical Society (APS)', 2020Co-Authors: G. Benham, Bendimerad R, Benzaquen Michael, Clanet C.Abstract:International audienceDuring motion from deep to shallow water, multiple equilibria may emerge, each with identical Drag. In this study, we show experimentally that the same Drag force may be experienced at several different speeds of body motion in shallow water, and that this can be explained by a localised amplification of the Wave Drag near the shallow Wave speed. Whilst Wave Drag in shallow water has been predicted with varying degrees of accuracy by several inviscid models, the bifurcation properties have not yet been discussed. Here, we address the nonlinear dynamics by considering the quasi-steady motion of a body between deep and shallow water, where the depth is slowly varying. In particular, we illustrate possible hysteresis routes between coexisting equilibrium states that have significantly different velocities, presenting interesting implications for naval and racing applications
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Wave Drag on asymmetric bodies
Journal of Fluid Mechanics, 2019Co-Authors: G. Benham, J. Boucher, R. Labbe, Michael Benzaquen, C. ClanetAbstract:An asymmetric body with a sharp leading edge and a rounded trailing edge produces a smaller Wave disturbance moving forwards than backwards, and this is reflected in the Wave Drag coefficient. This experimental fact is not captured by Michell's theory for Wave Drag (Michell Lond. Edinb. Dubl. Phil. Mag. J. Sci., vol. 45 (272), 1898, pp. 106-123). In this study, we use a tow-tank experiment to investigate the effects of asymmetry on Wave Drag, and show that these effects can be replicated by modifying Michell's theory to include the growth of a symmetry-breaking boundary layer. We show that asymmetry can have either a positive or a negative effect on Drag, depending on the depth of motion and the Froude number.
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Wave Drag on asymmetric bodies
Journal of Fluid Mechanics, 2019Co-Authors: G. Benham, R. Labbe, Michael Benzaquen, Jean-philippe Boucher, C. ClanetAbstract:An asymmetric body with a sharp leading edge and a rounded trailing edge produces a smaller Wave disturbance moving forwards than backwards, and this is reflected in the Wave Drag coefficient. This experimental fact is not captured by Michell's theory for Wave Drag (Michell 1898). In this study, we use a tow-tank experiment to investigate the effects of asymmetry on Wave Drag, and show that these effects can be replicated by modifying Michell's theory to include the growth of a symmetry-breaking boundary layer. We show that asymmetry can have either a positive or a negative effect on Drag, depending on the depth of motion and the Froude number.
Hyeyeong Chun - One of the best experts on this subject based on the ideXlab platform.
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Effects of Convective Gravity Wave Drag in the Southern Hemisphere Winter Stratosphere
Journal of the Atmospheric Sciences, 2013Co-Authors: Hyunjoo Choi, Hyeyeong ChunAbstract:AbstractThe excessively strong polar jet and cold pole in the Southern Hemisphere winter stratosphere are systematic biases in most global climate models and are related to underestimated Wave Drag in the winter extratropical stratosphere—namely, missing gravity Wave Drag (GWD). Cumulus convection is strong in the winter extratropics in association with storm-track regions; thus, convective GWD could be one of the missing GWDs in models that do not adopt source-based nonorographic GWD parameterizations. In this study, the authors use the Whole Atmosphere Community Climate Model (WACCM) and show that the zonal-mean wind and temperature biases in the Southern Hemisphere winter stratosphere of the model are significantly alleviated by including convective GWD (GWDC) parameterizations. The reduction in the wind biases is due to enhanced Wave Drag in the winter extratropical stratosphere, which is caused directly by the additional GWDC and indirectly by the increased existing nonorographic GWD and resolved wav...
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an overview of the past present and future of gravity Wave Drag parametrization for numerical climate and weather prediction models
Atmosphere-ocean, 2003Co-Authors: Youngjoon Kim, Stephen D. Eckermann, Hyeyeong ChunAbstract:Abstract An overview of the parametrization of gravity ‐Wave Drag in numerical ‐weather prediction and climate simulation models is presented. The focus is primarily on understanding the current status of gravity Wave Drag parametrization as a step towards the new parametrizations that will be needed for the next generation of atmospheric models. Both the early history and latest developments in the field are discussed. Parametrizations developed specifically for orographic and convective sources of gravity Waves are described separately, as are newer parametrizations that collectively treat a spectrum of gravity Wave motions. The differences in issues in and approaches for the parametrization of the lower and upper atmospheres are highlighted. Various emerging issues are also discussed, such as explicitly resolved gravity Waves and gravity Wave Drag in models, and a range of unparametrized gravity Wave processes that may need attention for the next generation of gravity Wave Drag parametrizations in models.
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An overview of the past, present and future of gravity‐Wave Drag parametrization for numerical climate and weather prediction models
Atmosphere-Ocean, 2003Co-Authors: Youngjoon Kim, Stephen D. Eckermann, Hyeyeong ChunAbstract:Abstract An overview of the parametrization of gravity ‐Wave Drag in numerical ‐weather prediction and climate simulation models is presented. The focus is primarily on understanding the current status of gravity Wave Drag parametrization as a step towards the new parametrizations that will be needed for the next generation of atmospheric models. Both the early history and latest developments in the field are discussed. Parametrizations developed specifically for orographic and convective sources of gravity Waves are described separately, as are newer parametrizations that collectively treat a spectrum of gravity Wave motions. The differences in issues in and approaches for the parametrization of the lower and upper atmospheres are highlighted. Various emerging issues are also discussed, such as explicitly resolved gravity Waves and gravity Wave Drag in models, and a range of unparametrized gravity Wave processes that may need attention for the next generation of gravity Wave Drag parametrizations in models.
Victor Steinberg - One of the best experts on this subject based on the ideXlab platform.
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Wave Drag due to generation of capillary-gravity surface Waves.
Physical review. E Statistical nonlinear and soft matter physics, 2002Co-Authors: Teodor Burghelea, Victor SteinbergAbstract:The onset of the Wave resistance via the generation of capillary-gravity Waves by a small object moving with a velocity V is investigated experimentally. Due to the existence of a minimum phase velocity V(c) for surface Waves, the problem is similar to the generation of rotons in superfluid helium near their minimum. In both cases, Waves or rotons are produced at V>V(c) due to Cherenkov radiation. We find that the transition to the Wave Drag state is continuous: in the vicinity of the bifurcation the Wave resistance force is proportional to sqrt[V-V(c)] for various fluids. This observation contradicts the theory of Raphaël and de Gennes. We also find that the reduced Wave Drag force for different fluids and different ball size may be scaled in such a way that all the data collapse on a single curve. The capillary-gravity Wave pattern and the shape of the Wave-generating region are investigated both experimentally and theoretically. Good agreement between the theory and the experimental data is found in this case.
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Wave Drag due to generation of capillary-gravity surface Waves
Physical Review E, 2002Co-Authors: Teodor Burghelea, Victor SteinbergAbstract:The onset of the Wave resistance via the generation of capillary-gravity Waves by a small object moving with a velocity V is investigated experimentally. Due to the existence of a minimum phase velocity V(c) for surface Waves, the problem is similar to the generation of rotons in superfluid helium near their minimum. In both cases, Waves or rotons are produced at V>V(c) due to Cherenkov radiation. We find that the transition to the Wave Drag state is continuous: in the vicinity of the bifurcation the Wave resistance force is proportional to sqrt[V-V(c)] for various fluids. This observation contradicts the theory of Raphael and de Gennes. We also find that the reduced Wave Drag force for different fluids and different ball size may be scaled in such a way that all the data collapse on a single curve. The capillary-gravity Wave pattern and the shape of the Wave-generating region are investigated both experimentally and theoretically. Good agreement between the theory and the experimental data is found in this case.
Michael Benzaquen - One of the best experts on this subject based on the ideXlab platform.
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Unsteady Wave Drag on a Disturbance Moving Along an Arbitrary Trajectory
2020Co-Authors: Lucas Gierczak-galle, Elie Raphaël, Assil Fadle, Maxence Arutkin, Michael BenzaquenAbstract:We derive analytical formulas for the wake and Wave Drag of a disturbance moving arbitrarily at the air-water interface. We show that, provided a constant velocity is reached in finite time, the unsteady surface displacement converges to its well-known steady counterpart as given by Havelock's famous formula. Finally we assess, in a specific situation, to which extent one can rightfully use Havelock's steady Wave Drag formula for non-uniform motion (quasi-static). Such an approach can be used to legitimize or discredit a number of studies which used steady Wave Drag formulas in unsteady situations.
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Hysteretic Wave Drag in shallow water
Physical Review Fluids, 2020Co-Authors: G. Benham, Michael Benzaquen, R Bendimerad, C. ClanetAbstract:During motion from deep to shallow water, multiple equilibria may emerge, each with identical Drag. In this study, we show experimentally that the same Drag force may be experienced at several different speeds of body motion in shallow water, and that this can be explained by a localised amplification of the Wave Drag near the shallow Wave speed. Whilst Wave Drag in shallow water has been predicted with varying degrees of accuracy by several inviscid models, the bifurcation properties have not yet been discussed. Here, we address the nonlinear dynamics by considering the quasi-steady motion of a body between deep and shallow water, where the depth is slowly varying. In particular, we illustrate possible hysteresis routes between coexisting equilibrium states that have significantly different velocities, presenting interesting implications for naval and racing applications.
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Wave Drag on asymmetric bodies
Journal of Fluid Mechanics, 2019Co-Authors: G. Benham, J. Boucher, R. Labbe, Michael Benzaquen, C. ClanetAbstract:An asymmetric body with a sharp leading edge and a rounded trailing edge produces a smaller Wave disturbance moving forwards than backwards, and this is reflected in the Wave Drag coefficient. This experimental fact is not captured by Michell's theory for Wave Drag (Michell Lond. Edinb. Dubl. Phil. Mag. J. Sci., vol. 45 (272), 1898, pp. 106-123). In this study, we use a tow-tank experiment to investigate the effects of asymmetry on Wave Drag, and show that these effects can be replicated by modifying Michell's theory to include the growth of a symmetry-breaking boundary layer. We show that asymmetry can have either a positive or a negative effect on Drag, depending on the depth of motion and the Froude number.
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Wave Drag on asymmetric bodies
Journal of Fluid Mechanics, 2019Co-Authors: G. Benham, R. Labbe, Michael Benzaquen, Jean-philippe Boucher, C. ClanetAbstract:An asymmetric body with a sharp leading edge and a rounded trailing edge produces a smaller Wave disturbance moving forwards than backwards, and this is reflected in the Wave Drag coefficient. This experimental fact is not captured by Michell's theory for Wave Drag (Michell 1898). In this study, we use a tow-tank experiment to investigate the effects of asymmetry on Wave Drag, and show that these effects can be replicated by modifying Michell's theory to include the growth of a symmetry-breaking boundary layer. We show that asymmetry can have either a positive or a negative effect on Drag, depending on the depth of motion and the Froude number.
