In this paper, we investigate the performance of particle tracking, exploring the in¯uence of an ... more In this paper, we investigate the performance of particle tracking, exploring the in¯uence of an increasing amount of estimators. Basically, a simple method to determine particle matchings was used. Then, ®rst, temporal extrapolation as well as spatial interpolation are employed. Second, a PIV processing step was incorporated. Tests from simulations show that at relatively high seeding densities the performance was increased by a factor of 4 and 13 for the ®rst and second step, respectively. In a physical experiment of a wake behind a heated cylinder, a clear performance improvement in the case of PIV preprocessing was observed.
By means of detailed measurements it is shown that the outflow characteristics of the commonly us... more By means of detailed measurements it is shown that the outflow characteristics of the commonly used glass cloth type metal distribution bag are strongly influenced by the deformation of the bag. This deformation is caused by the dynamic interaction between the flexible bag and its surrounding flow field. As a consequence, accurate prediction of the fluid flow in the liquid pool cannot be performed if the distortion of the distribution bag is not taken into account. In this article a method is presented to incorporate the influence of the distortion of the flexible bag on the flow. In this method results from water model measurement are used as input for the numerical modeling. These measurements represent in an implicit manner the entire interaction of the flexible distribution bag with the flow field. The modeling results then show that using the measured input leads to a different and more accurate prediction of the mixing in the sump compared to a more conventional method of modeling.
In this report we investigate the performance of particle tracking, exploring the influence of an... more In this report we investigate the performance of particle tracking, exploring the influence of an increasing amount of estimators. Basically, a simple method to determine particle matchings was used. Then, first, temporal extrapolation as well as spatial interpolation are employed. Second, a PIV processing step was incorporated. Tests from simulations show that at relatively high seeding densities the performance was increased with a factor of 4 and 13 for the first and second step, respectively. In a physical experiment of a wake behind a heated cylinder a clear performance improvement in the case of PIV preprocessing was observed.
A technique is described to measure the instantaneous 2D temperature distribution in the wake of ... more A technique is described to measure the instantaneous 2D temperature distribution in the wake of a heated cylinder using`laser-induced¯uorescence'. Rhodamine B, a¯uorescent dye, is used as a temperature indicator. The relation between¯uorescence intensity and temperature is determined by means of calibration experiments in the temperature range of 20±35°C with an accuracy of 0.1°C. The temperature distribution behind the heated cylinder is well visible and can be measured with a high spatial resolution. Corrections for variation in laser energy and intensity distribution in the laser sheet have to be made to further improve the accuracy of the measuring method.
DOI to the publisher's website. • The final author version and the galley proof are versions of t... more DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:
Aluminium alloys are a standard cast metal used in a number of automotive and transportation appl... more Aluminium alloys are a standard cast metal used in a number of automotive and transportation applications, allowing manufacturers to reduce vehicle weight, increase the strength of components and improve emission controls. One of the most challenging problems associated with aluminium casting is the influence of convection during all stages of solidification. The strength of fluid flow changes the as-cast internal structure (microstructure) such that the yield, fracture and fatigue strengths of the cast ingot can vary considerably. Although the importance of fluid flow has been recognised for decades, not even a simple model has been developed to predict the effect on microstructure. The MICAST project aims to identify and control experimentally the fluid-flow patterns that affect microstructure evolution during casting processes, and to develop analytical and advanced numerical models. The microgravity environment of the International Space Station and sounding rockets is of specia...
This paper describes a numerical and experimental study of the effect of heat input on the behavi... more This paper describes a numerical and experimental study of the effect of heat input on the behaviour of the vortices shed from a horizontal cylinder in a horizontal crossflow. The Reynolds number (Re D) is fixed at 75, while the Richardson number (Ri D) is varied between 0 and 1 (corresponding to forced and mixed convection, respectively). In this parameter regime the wake consists of a double row of alternately shed vortices. A rather unexpected effect of the induced heat is the downward motion of the shed vortex structures. Detailed experiments and numerical simulations show that this effect is caused by the difference in strength between the two vortex rows. An analysis of the vorticity sources present during the formation process shows that the thermally induced baroclinic vorticity production is mainly responsible for this.
International Journal of Heat and Mass Transfer, 2002
A combined numerical and experimental investigation is presented showing the effect of heat on th... more A combined numerical and experimental investigation is presented showing the effect of heat on the stability of a horizontal vortex street for Re D ¼ 75 and Ri D between 1 and 2. Detailed 2D-HiRes PV experiments are compared with 2D numerical results. The results show that an early transition to 3D of the vortex street takes place for Ri D > 1. Furthermore, the location at which the 2D wake becomes essentially 3D turns out to be dependent on Ri D. For an increasing addition of heat (increasing Ri D), this location is shifted into the direction of the cylinder. By applying 3D measuring techniques, such as 3D-PTV and 3D visualisation techniques, the transition process and the behaviour downstream of the transition point are investigated.
International Journal of Heat and Fluid Flow, 2007
This article presents the investigation on the vortex formation and shedding process behind a hea... more This article presents the investigation on the vortex formation and shedding process behind a heated cylinder which is exposed to a cold cross flow. The Reynolds number is chosen to be 75 while the Grashof number is varied between 0 and 5000 (resulting in a variation from forced to mixed convection). The numerical results show that the addition of heat disturbs the vortex formation process. The vortices shed from the upper half of the cylinder become stronger for increasing heat input. Therefore, the shedding process at the upper half of the cylinder becomes more effective compared with the process at the lower half. Consequently, the vortices shed from the upper half of the cylinder have a higher vorticity extreme and a higher temperature. The results show that the difference in effectiveness is mainly caused by a decreasing effect of strain rate during the formation of an upper vortex. This change in strain rate is caused by a change in flow pattern around the cylinder for increasing Grashof number. For higher heat input more fluid flows underneath the cylinder, resulting in weaker shear layers at the upper part of the cylinder.
The behaviour of vortex structures shed from a heated cylinder is experimentally investigated by ... more The behaviour of vortex structures shed from a heated cylinder is experimentally investigated by means of 2-D particle tracking velocimetry. Within this investigation the e h number was chosen to be 73. The i h number, the dimensionless number which presents the relative importance of the induced heat, varies between 0 and 1. The experiments were carried out in a large towing tank where the disturbances caused by boundary layers could be minimised. The results show that for small i h numbers the induced heat results in a de¯ection of the vortex street in negative y-direction. Within the vortex street a linking of two subsequently shed vortices occurs where the vortex shed from the lower half of the cylinder rotates around the vortex shed from the upper half. These phenomena are assumed to be caused by a strength dierence between the vortices shed from the upper half of the cylinder and the lower half. For i h 1 the eect of the induced heat and buoyancy becomes even more pronounced resulting in a more upwards directed vortex street.
Solidification of alloys is a complex phenomenon arising in many modern experimental techniques a... more Solidification of alloys is a complex phenomenon arising in many modern experimental techniques and industrial technologies involving casting and surface processing. Deep undercooling of alloys below equilibrium liquidus temperature results in ...
A 3D particle-tracking velocimetry (PTV) algorithm is applied to the wake flow behind a heated cy... more A 3D particle-tracking velocimetry (PTV) algorithm is applied to the wake flow behind a heated cylinder. The method is tested in advance with respect to its accuracy and performance. In the accuracy tests, its capability to locate particles in 3D space is tested. It appears that the algorithm can determine the particle position with an accuracy of less than 0.5 camera pixels, equivalent to 0.3 mm in the present test situation. The performance tests show that for particles located in a 2D plane, the algorithm can track the particles with a vector yield reaching 100%, which means that a velocity vector can be determined for almost all particles detected. The calculated velocity vectors for this situation have a standard deviation of less than 1%. The performance is also tested on a mixed convection flow behind a heated cylinder in which the 2D flow transits into a 3D flow. As there is no exact solution of such a flow available, the 3D PTV results are compared with visualisation results. The results show that the 3D PTV method can capture the main features of the 3D transition of the 2D vortex street.
In this paper, we investigate the performance of particle tracking, exploring the in¯uence of an ... more In this paper, we investigate the performance of particle tracking, exploring the in¯uence of an increasing amount of estimators. Basically, a simple method to determine particle matchings was used. Then, ®rst, temporal extrapolation as well as spatial interpolation are employed. Second, a PIV processing step was incorporated. Tests from simulations show that at relatively high seeding densities the performance was increased by a factor of 4 and 13 for the ®rst and second step, respectively. In a physical experiment of a wake behind a heated cylinder, a clear performance improvement in the case of PIV preprocessing was observed.
By means of detailed measurements it is shown that the outflow characteristics of the commonly us... more By means of detailed measurements it is shown that the outflow characteristics of the commonly used glass cloth type metal distribution bag are strongly influenced by the deformation of the bag. This deformation is caused by the dynamic interaction between the flexible bag and its surrounding flow field. As a consequence, accurate prediction of the fluid flow in the liquid pool cannot be performed if the distortion of the distribution bag is not taken into account. In this article a method is presented to incorporate the influence of the distortion of the flexible bag on the flow. In this method results from water model measurement are used as input for the numerical modeling. These measurements represent in an implicit manner the entire interaction of the flexible distribution bag with the flow field. The modeling results then show that using the measured input leads to a different and more accurate prediction of the mixing in the sump compared to a more conventional method of modeling.
In this report we investigate the performance of particle tracking, exploring the influence of an... more In this report we investigate the performance of particle tracking, exploring the influence of an increasing amount of estimators. Basically, a simple method to determine particle matchings was used. Then, first, temporal extrapolation as well as spatial interpolation are employed. Second, a PIV processing step was incorporated. Tests from simulations show that at relatively high seeding densities the performance was increased with a factor of 4 and 13 for the first and second step, respectively. In a physical experiment of a wake behind a heated cylinder a clear performance improvement in the case of PIV preprocessing was observed.
A technique is described to measure the instantaneous 2D temperature distribution in the wake of ... more A technique is described to measure the instantaneous 2D temperature distribution in the wake of a heated cylinder using`laser-induced¯uorescence'. Rhodamine B, a¯uorescent dye, is used as a temperature indicator. The relation between¯uorescence intensity and temperature is determined by means of calibration experiments in the temperature range of 20±35°C with an accuracy of 0.1°C. The temperature distribution behind the heated cylinder is well visible and can be measured with a high spatial resolution. Corrections for variation in laser energy and intensity distribution in the laser sheet have to be made to further improve the accuracy of the measuring method.
DOI to the publisher's website. • The final author version and the galley proof are versions of t... more DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:
Aluminium alloys are a standard cast metal used in a number of automotive and transportation appl... more Aluminium alloys are a standard cast metal used in a number of automotive and transportation applications, allowing manufacturers to reduce vehicle weight, increase the strength of components and improve emission controls. One of the most challenging problems associated with aluminium casting is the influence of convection during all stages of solidification. The strength of fluid flow changes the as-cast internal structure (microstructure) such that the yield, fracture and fatigue strengths of the cast ingot can vary considerably. Although the importance of fluid flow has been recognised for decades, not even a simple model has been developed to predict the effect on microstructure. The MICAST project aims to identify and control experimentally the fluid-flow patterns that affect microstructure evolution during casting processes, and to develop analytical and advanced numerical models. The microgravity environment of the International Space Station and sounding rockets is of specia...
This paper describes a numerical and experimental study of the effect of heat input on the behavi... more This paper describes a numerical and experimental study of the effect of heat input on the behaviour of the vortices shed from a horizontal cylinder in a horizontal crossflow. The Reynolds number (Re D) is fixed at 75, while the Richardson number (Ri D) is varied between 0 and 1 (corresponding to forced and mixed convection, respectively). In this parameter regime the wake consists of a double row of alternately shed vortices. A rather unexpected effect of the induced heat is the downward motion of the shed vortex structures. Detailed experiments and numerical simulations show that this effect is caused by the difference in strength between the two vortex rows. An analysis of the vorticity sources present during the formation process shows that the thermally induced baroclinic vorticity production is mainly responsible for this.
International Journal of Heat and Mass Transfer, 2002
A combined numerical and experimental investigation is presented showing the effect of heat on th... more A combined numerical and experimental investigation is presented showing the effect of heat on the stability of a horizontal vortex street for Re D ¼ 75 and Ri D between 1 and 2. Detailed 2D-HiRes PV experiments are compared with 2D numerical results. The results show that an early transition to 3D of the vortex street takes place for Ri D > 1. Furthermore, the location at which the 2D wake becomes essentially 3D turns out to be dependent on Ri D. For an increasing addition of heat (increasing Ri D), this location is shifted into the direction of the cylinder. By applying 3D measuring techniques, such as 3D-PTV and 3D visualisation techniques, the transition process and the behaviour downstream of the transition point are investigated.
International Journal of Heat and Fluid Flow, 2007
This article presents the investigation on the vortex formation and shedding process behind a hea... more This article presents the investigation on the vortex formation and shedding process behind a heated cylinder which is exposed to a cold cross flow. The Reynolds number is chosen to be 75 while the Grashof number is varied between 0 and 5000 (resulting in a variation from forced to mixed convection). The numerical results show that the addition of heat disturbs the vortex formation process. The vortices shed from the upper half of the cylinder become stronger for increasing heat input. Therefore, the shedding process at the upper half of the cylinder becomes more effective compared with the process at the lower half. Consequently, the vortices shed from the upper half of the cylinder have a higher vorticity extreme and a higher temperature. The results show that the difference in effectiveness is mainly caused by a decreasing effect of strain rate during the formation of an upper vortex. This change in strain rate is caused by a change in flow pattern around the cylinder for increasing Grashof number. For higher heat input more fluid flows underneath the cylinder, resulting in weaker shear layers at the upper part of the cylinder.
The behaviour of vortex structures shed from a heated cylinder is experimentally investigated by ... more The behaviour of vortex structures shed from a heated cylinder is experimentally investigated by means of 2-D particle tracking velocimetry. Within this investigation the e h number was chosen to be 73. The i h number, the dimensionless number which presents the relative importance of the induced heat, varies between 0 and 1. The experiments were carried out in a large towing tank where the disturbances caused by boundary layers could be minimised. The results show that for small i h numbers the induced heat results in a de¯ection of the vortex street in negative y-direction. Within the vortex street a linking of two subsequently shed vortices occurs where the vortex shed from the lower half of the cylinder rotates around the vortex shed from the upper half. These phenomena are assumed to be caused by a strength dierence between the vortices shed from the upper half of the cylinder and the lower half. For i h 1 the eect of the induced heat and buoyancy becomes even more pronounced resulting in a more upwards directed vortex street.
Solidification of alloys is a complex phenomenon arising in many modern experimental techniques a... more Solidification of alloys is a complex phenomenon arising in many modern experimental techniques and industrial technologies involving casting and surface processing. Deep undercooling of alloys below equilibrium liquidus temperature results in ...
A 3D particle-tracking velocimetry (PTV) algorithm is applied to the wake flow behind a heated cy... more A 3D particle-tracking velocimetry (PTV) algorithm is applied to the wake flow behind a heated cylinder. The method is tested in advance with respect to its accuracy and performance. In the accuracy tests, its capability to locate particles in 3D space is tested. It appears that the algorithm can determine the particle position with an accuracy of less than 0.5 camera pixels, equivalent to 0.3 mm in the present test situation. The performance tests show that for particles located in a 2D plane, the algorithm can track the particles with a vector yield reaching 100%, which means that a velocity vector can be determined for almost all particles detected. The calculated velocity vectors for this situation have a standard deviation of less than 1%. The performance is also tested on a mixed convection flow behind a heated cylinder in which the 2D flow transits into a 3D flow. As there is no exact solution of such a flow available, the 3D PTV results are compared with visualisation results. The results show that the 3D PTV method can capture the main features of the 3D transition of the 2D vortex street.
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Papers by Rene Kieft