Freely rising light solid spheres

Veldhuis, Christian; Biesheuvel, A.; Lohse, Detlef

doi:10.1016/j.ijmultiphaseflow.2009.01.005

Cited by 44 publications

(63 citation statements)

References 27 publications

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“…The authors elegantly demonstrate that the periodically detaching vortex threads exert an oscillating force on the spheres in a direction transverse to the flow. Yet, Veldhuis et al (2009) demonstrate that this force is usually not restricted to the plane transverse to the flow in the case of buoyant spheres rising freely in a Newtonian fluid. As a consequence, the component of this force in the direction of the spheres' motion is non-zero, which results in a so-called lift-induced drag.…”

Section: Procedures For the Derivation Of A Drag Curve For Sounding Bamentioning

confidence: 96%

Modeling the ascent of sounding balloons: derivation of the vertical air motion

et al. 2011

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Abstract.A new model to describe the ascent of sounding balloons in the troposphere and lower stratosphere (up to ∼30-35 km altitude) is presented. Contrary to previous models, detailed account is taken of both the variation of the drag coefficient with altitude and the heat imbalance between the balloon and the atmosphere. To compensate for the lack of data on the drag coefficient of sounding balloons, a reference curve for the relationship between drag coefficient and Reynolds number is derived from a dataset of flights launched during the Lindenberg Upper Air Methods Intercomparisons (LUAMI) campaign. The transfer of heat from the surrounding air into the balloon is accounted for by solving the radial heat diffusion equation inside the balloon. In its present state, the model does not account for solar radiation, i.e. it is only able to describe the ascent of balloons during the night. It could however be adapted to also represent daytime soundings, with solar radiation modeled as a diffusive process. The potential applications of the model include the forecast of the trajectory of sounding balloons, which can be used to increase the accuracy of the match technique, and the derivation of the air vertical velocity. The latter is obtained by subtracting the ascent rate of the balloon in still air calculated by the model from the actual ascent rate. This technique is shown to provide an approximation for the vertical air motion with an uncertainty error of 0.5 m s −1 in the troposphere and 0.2 m s −1 in the stratosphere. An example of extraction of the air vertical velocity is provided Correspondence to: A. Gallice (aurelien.gallice@gmail.com) in this paper. We show that the air vertical velocities derived from the balloon soundings in this paper are in general agreement with small-scale atmospheric velocity fluctuations related to gravity waves, mechanical turbulence, or other small-scale air motions measured during the SUCCESS campaign (Subsonic Aircraft: Contrail and Cloud Effects Special Study) in the orographically unperturbed mid-latitude middle troposphere.

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Section: Procedures For the Derivation Of A Drag Curve For Sounding Bamentioning

confidence: 96%

Modeling the ascent of sounding balloons: derivation of the vertical air motion

et al. 2011

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“…The motion of single bubbles was surveyed in [38], and oscillating paths of freely rising or falling bodies in viscous fluids were reviewed in [12]. Ascending and sedimenting spheres and respective wake visualizations were studied experimentally in [66][67][68]. A very extensive experimental study and a review on the dynamics and wakes for the motion of a sphere in quiescent fluid is provided in [23].…”

Section: Introductionmentioning

confidence: 99%

A temporal discretization scheme to compute the motion of light particles in viscous flows by an immersed boundary method

Schwarz

Kempe

Fröhlich

2015

Journal of Computational Physics

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“…Marchildon et al [14] and Veldhuis et al [12,13,23] also employed a similar configuration but using only one camera and an arrangement of perpendicular mirrors to see the motion on both normal planes. Even though both methods offer a straightforward means to calculate the 3D coordinates of the moving particles, they require a highly accurate alignment of the cameras or mirrors which considerably decreases the flexibility of this alternative approach.…”

Section: Methodsmentioning

confidence: 99%

“…They found that a temperature difference over the tank depth as minimum as 0.15 °C was enough. This technique was also employed by Veldhuis et al [12,13,23] in their investigations about the motion of falling and rising spheres.…”

Section: Methodsmentioning

confidence: 99%

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Study of drag and orientation of regular particles using stereo vision, Schlieren photography and digital image processing

Carranza

Zhang

2017

Powder Technology

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A new experimental, image-based methodology suitable to track the changes in orientation of non-spherical particles and their influence on the drag coefficient as they settle in fluids is presented. Given the fact that non-spherical solids naturally develop variations in their angular orientation during the fall, none-intrusiveness of the technique of analysis is of paramount importance in order to preserve the particle/fluid interaction undisturbed. Three-dimensional quantitative data about the motion parameters is obtained through single-camera stereo vision whilst qualitative visualizations of the adjacent fluid patterns are achieved with Schlieren photography. The methodology was validated by comparing the magnitudes of the drag coefficient of a set of spherical particles at terminal velocity conditions against those estimated from drag correlations published in the literature. A noteworthy similarity was attained. During the fall of non-spherical solids, once the particle Reynolds number approximated 163 for disks, and 240 for cylinders, or exceeded those values, secondary motions composed by regular oscillations and tumbling were present. They altered the angular orientation of the particles with respect to the main motion direction and caused complete turbulent patterns in the surrounding flow, therefore affecting the instantaneous projected area, drag force, and coefficient of resistance. The impact of the changes in angular orientation onto the drag coefficient was shown graphically as a means for reinforcing existing numerical approaches, however, an explicit relation between both variables could not be observed.

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Freely rising light solid spheres

Cited by 44 publications

References 27 publications

Modeling the ascent of sounding balloons: derivation of the vertical air motion

Modeling the ascent of sounding balloons: derivation of the vertical air motion

A temporal discretization scheme to compute the motion of light particles in viscous flows by an immersed boundary method

Study of drag and orientation of regular particles using stereo vision, Schlieren photography and digital image processing

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