Search

Contactless Inductive Flow Tomography (CIFT) is a flow measurement technique allowing for visualizing the global flow in electrically conducting fluids. The method is based on the precise measurement of very weak induced magnetic fields arising from the fluid motion under the influence of one or several primary excitation magnetic field(s). The simultaneous use of more than one excitation magnetic field is necessary to fully reconstruct three-dimensional liquid metal flows, yet is not trivial as the scalar values of induced magnetic field at the sensors need to be disentangled for each contribution of the excitation fields. Another approach is to multiplex the excitation fields. Here the temporal resolution of the measurement needs to be kept as high as possible. We apply two trapezoidal-shaped excitation magnetic fields with perpendicular direction to each other to a mechanically driven liquid metal flow. The consecutive application by multiplexing enables to determine the flow structure in the liquid with a temporal resolution down to 3 s with the existing equipment.

Contactless Inductive Flow Tomography (CIFT) is a flow measurement technique allowing for visualizing the global flow in electrically conducting fluids. The method is based on the precise measurement of very weak induced magnetic fields arising from the fluid motion under the influence of one or several primary excitation magnetic field(s). The simultaneous use of more than one excitation magnetic field is necessary to fully reconstruct three-dimensional liquid metal flows, yet is not trivial as the scalar values of induced magnetic field at the sensors need to be disentangled for each contribution of the excitation fields. Another approach is to multiplex the excitation fields. Here the temporal resolution of the measurement needs to be kept as high as possible. We apply two trapezoidal-shaped excitation magnetic fields with perpendicular direction to each other to a mechanically driven liquid metal flow. The consecutive application by multiplexing enables to determine the flow structure in the liquid with a temporal resolution down to 3 s with the existing equipment.

Mit der kontaktlosen induktiven Strömungstomografie (CIFT) lassen sich Geschwindigkeitsfelder in elektrisch leitfähigen Flüssigkeiten global bestimmen. Kenntnisse über den Strömungszustand in Metallschmelzen sind für industrielle Prozesse, wie das Stranggießen von Stahl, von immenser Bedeutung und können auch in der Grundlagenforschung nutzbringend angewendet werden, z.B. zur Analyse von konvektiven Flüssigmetallströmungen als Modellsysteme des Wärmetransportes. Das Verfahren beruht auf der präzisen Messung kleinster Magnetfeldänderungen durch geeignete Sonden und der nachfolgenden Rekonstruktion der Strömungsstruktur durch die Lösung eines linearen inversen Problems. In dieser Veröffentlichung geben wir einen Überblick über die Entwicklungen der letzten Dekade und diskutierten je einen Anwendungsfall für CIFT aus der grundlegenden und der angewandten Fluiddynamik. >>Contactless Inductive Flow Tomography (CIFT) is a flow measurement technique that can reconstruct the global 3D flow in electrically conducting fluids. Knowledge of the flow conditions in liquid metals is of outmost importance for industrial processes as continuous casting of steel. CIFT can also be applied to fundamental research, e.g. to measure convective liquid metal flows. The technique is based on the precise measurement of very small magnetic field changes and the subsequent reconstruction of the flow field by solving the linear inverse problem. This publication illustrates one use-case from fundamental and applied fluid mechanics each.

Contactless Inductive Flow Tomography (CIFT) is a flow measurement technique allowing for visualizing the global flow in electrically conducting fluids. The method is based on the precise measurement of very weak induced magnetic fields arising from the fluid motion under the influence of one or several primary excitation magnetic field(s). The simultaneous use of more than one excitation magnetic field is necessary to fully reconstruct three-dimensional liquid metal flows, yet is not trivial as the scalar values of induced magnetic field at the sensors need to be disentangled for each contribution of the excitation fields. Another approach is to multiplex the excitation fields. Here the temporal resolution of the measurement needs to be kept as high as possible. We apply two trapezoidal-shaped excitation magnetic fields with perpendicular direction to each other to a mechanically driven liquid metal flow. The consecutive application by multiplexing enables to determine the flow structure in the liquid with a temporal resolution down to 3 s with the existing equipment.

Contactless Inductive Flow Tomography (CIFT) is a flow measurement technique allowing for visualizing the global flow in electrically conducting fluids. The method is based on the precise measurement of very weak induced magnetic fields arising from the fluid motion under the influence of one or several primary excitation magnetic field(s). The simultaneous use of more than one excitation magnetic field is necessary to fully reconstruct three-dimensional liquid metal flows, yet is not trivial as the scalar values of induced magnetic field at the sensors need to be disentangled for each contribution of the excitation fields. Another approach is to multiplex the excitation fields. Here the temporal resolution of the measurement needs to be kept as high as possible. We apply two trapezoidal-shaped excitation magnetic fields with perpendicular direction to each other to a mechanically driven liquid metal flow. The consecutive application by multiplexing enables to determine the flow structure in the liquid with a temporal resolution down to 3 s with the existing equipment.

Contactless inductive flow tomography (CIFT) can reconstruct the global 3D flow field in liquid metals. The technique is based on measuring very small magnetic fields induced by currents in the conducting liquid arising from the fluid motion under the influence of two primary excitation fields and solving the according linear inverse problem [1]. We present experimental results of CIFT measurements on a large cylindrical vessel with a height of 640 mm and a diameter of 320 mm, i.e. aspect ratio 0.5, filled with the eutectic alloy GaInSn. The liquid metal is heated from the bottom and cooled from the top, i.e. a so-called Rayleigh-Bénard (RB) convection cell. The temperature gradient drives a complex flow, that varies spatially and temporally [2-5]. The experimental set-up includes a number of Fluxgate sensors for highly sensitive measurements of the induced magnetic field in the order of 10 nT [6] as well as Ultrasound-Doppler velocimetry probes, that directly measure the velocity of the flow along their line-of-sight. Our preliminary measurements used only the excitation field in vertical direction, yet show a very high agreement of the time-dependent velocity profiles measured by UDV and the according CIFT data, projected onto the line-of-sight of the UDV sensors. Acknowledgement This work was supported by the German Research Foundation (DFG) under project no. 374994652. T.V. and F.S. also thank the DFG for support under the grant VO 2331/1. REFERENCES [1] Stefani F., Gundrum T., Gerbeth G., Physical Review E 70: 056306. 2004. [2] Akashi M. et al., J. Fluid Mech. 932 (2022). [3] Zürner T. et al., J. Fluid Mech. 876 (2019). [4] Vogt T. et al., PNAS 115 (2018). [5] Mitra R. et al., Magnetohydrodynamics, vol. 58 (2022) [accepted for publication]. [6] Sieger M. et al., Magnetohydrodynamics, vol. 58 (2022) [accepted for publication].

Contactless inductive flow tomography (CIFT) is a flow measurement technique developed at Helmholtz-Zentrum Dresden-Rossendorf that can reconstruct the global 3D flow field in electrically conducting fluids such as liquid metals. The velocity field of the moving fluid can be reconstructed by solving the underlying inverse problem using appropriate regularization methods. This publication introduces the key concept and mathematical foundation of the method and illustrates the measurement capability of CIFT on two examples: continuous casting of steel in applied fluid dynamics and Rayleigh-Bénard convection as a paradigmatic system in fundamental fluid dynamics.

Contactless inductive flow tomography (CIFT) is a flow measurement technique developed at Helmholtz-Zentrum Dresden-Rossendorf that can reconstruct the global 3D flow field in electrically conducting fluids such as liquid metals. The velocity field of the moving fluid can be reconstructed by solving the underlying inverse problem using appropriate regularization methods. This publication introduces the key concept and mathematical foundation of the method and illustrates the measurement capability of CIFT on two examples: continuous casting of steel in applied fluid dynamics and Rayleigh-Bénard convection as a paradigmatic system in fundamental fluid dynamics.

Contactless inductive flow tomography (CIFT) can reconstruct the global 3D flow field in liquid metals. The technique is based on measuring very small magnetic fields induced by currents in the conducting liquid arising from the fluid motion under the influence of two primary excitation fields and solving the according linear inverse problem [1]. We present experimental results of CIFT measurements on a large cylindrical vessel with a height of 640 mm and a diameter of 320 mm, i.e. aspect ratio 0.5, filled with the eutectic alloy GaInSn. The liquid metal is heated from the bottom and cooled from the top, i.e. a so-called Rayleigh-Bénard (RB) convection cell. The temperature gradient drives a complex flow, that varies spatially and temporally [2-5]. The experimental set-up includes a number of Fluxgate sensors for highly sensitive measurements of the induced magnetic field in the order of 10 nT [6] as well as Ultrasound-Doppler velocimetry probes, that directly measure the velocity of the flow along their line-of-sight. Our preliminary measurements used only the excitation field in vertical direction, yet show a very high agreement of the time-dependent velocity profiles measured by UDV and the according CIFT data, projected onto the line-of-sight of the UDV sensors. Acknowledgement This work was supported by the German Research Foundation (DFG) under project no. 374994652. T.V. and F.S. also thank the DFG for support under the grant VO 2331/1. REFERENCES [1] Stefani F., Gundrum T., Gerbeth G., Physical Review E 70: 056306. 2004. [2] Akashi M. et al., J. Fluid Mech. 932 (2022). [3] Zürner T. et al., J. Fluid Mech. 876 (2019). [4] Vogt T. et al., PNAS 115 (2018). [5] Mitra R. et al., Magnetohydrodynamics, vol. 58 (2022) [accepted for publication]. [6] Sieger M. et al., Magnetohydrodynamics, vol. 58 (2022) [accepted for publication].

Contactless inductive flow tomography (CIFT) can reconstruct the global 3D flow field in liquid metals. The technique is based on measuring very small magnetic fields induced by currents in the conducting liquid arising from the fluid motion under the influence of two primary excitation fields and solving the according linear inverse problem [1]. We present experimental results of CIFT measurements on a large cylindrical vessel with a height of 640 mm and a diameter of 320 mm, i.e. aspect ratio 0.5, filled with the eutectic alloy GaInSn. The liquid metal is heated from the bottom and cooled from the top, i.e. a so-called Rayleigh-Bénard (RB) convection cell. The temperature gradient drives a complex flow, that varies spatially and temporally [2-5]. The experimental set-up includes a number of Fluxgate sensors for highly sensitive measurements of the induced magnetic field in the order of 10 nT [6] as well as Ultrasound-Doppler velocimetry probes, that directly measure the velocity of the flow along their line-of-sight. Our preliminary measurements used only the excitation field in vertical direction, yet show a very high agreement of the time-dependent velocity profiles measured by UDV and the according CIFT data, projected onto the line-of-sight of the UDV sensors. Acknowledgement This work was supported by the German Research Foundation (DFG) under project no. 374994652. T.V. and F.S. also thank the DFG for support under the grant VO 2331/1. REFERENCES [1] Stefani F., Gundrum T., Gerbeth G., Physical Review E 70: 056306. 2004. [2] Akashi M. et al., J. Fluid Mech. 932 (2022). [3] Zürner T. et al., J. Fluid Mech. 876 (2019). [4] Vogt T. et al., PNAS 115 (2018). [5] Mitra R. et al., Magnetohydrodynamics, vol. 58 (2022) [accepted for publication]. [6] Sieger M. et al., Magnetohydrodynamics, vol. 58 (2022) [accepted for publication].

Contactless inductive flow tomography (CIFT) is a flow measurement technique developed at Helmholtz-Zentrum Dresden-Rossendorf that can reconstruct the global 3D flow field in electrically conducting fluids such as liquid metals. The velocity field of the moving fluid can be reconstructed by solving the underlying inverse problem using appropriate regularization methods. This publication introduces the key concept and mathematical foundation of the method and illustrates the measurement capability of CIFT on two examples: continuous casting of steel in applied fluid dynamics and Rayleigh-Bénard convection as a paradigmatic system in fundamental fluid dynamics.

Contactless inductive flow tomography (CIFT) can reconstruct the complex 3-dimensional flow structure of the large scale circulation in liquid metal filled Rayleigh-Bénard (RB) convection cells. The method relies on the precise measurement of weak magnetic fields induced by currents in the conducting liquid arising from the fluid motion in combination with primary excitation fields. The velocity distribution is reconstructed from the magnetic field measurements by solving a linear inverse problem using the Tikhonov regularization and L-curve method. A number of technical challenges have to be overcome to reach the desired accuracy of the measurement signals. In this paper we will describe our design of a new CIFT set-up for a large RB vessel with a diameter of 320 mm and a height of 640 mm. We outline the major factors perturbing the measurement signal of several tens of nanoteslas and describe solutions to decrease mechanical drifts by thermal expansion to a sub-critical level to enable CIFT measurements for high-Rayleigh number flows.

The time dependent behaviour of the large-scale circulation in a Rayleigh-Bénard convection cell exhibits a rich set of different three-dimensional flow features like rotations or torsional modes. In this paper, the applicability of the contactless inductive flow tomography (CIFT) to visualise these flow features in a cylindrical cell filled with GaInSn is investigated numerically. The simulated flow in the cylinder with a diameter of 320 mm and a height of 640 mm serves as a basis to investigate the quality of the reconstructed velocity field by CIFT.

Contactless inductive flow tomography (CIFT) is a flow measurement technique developed at Helmholtz-Zentrum Dresden-Rossendorf that can reconstruct the global 3D flow field in electrically conducting fluids such as liquid metals. The velocity field of the moving fluid can be reconstructed by solving the underlying inverse problem using appropriate regularization methods. This publication introduces the key concept and mathematical foundation of the method and illustrates the measurement capability of CIFT on two examples: continuous casting of steel in applied fluid dynamics and Rayleigh-Bénard convection as a paradigmatic system in fundamental fluid dynamics.

Contactless inductive flow tomography (CIFT) can reconstruct the global 3D flow field in liquid metals. The technique is based on measuring very small magnetic fields induced by currents in the conducting liquid arising from the fluid motion under the influence of two primary excitation fields and solving the according linear inverse problem [1]. We present experimental results of CIFT measurements on a large cylindrical vessel with a height of 640 mm and a diameter of 320 mm, i.e. aspect ratio 0.5, filled with the eutectic alloy GaInSn. The liquid metal is heated from the bottom and cooled from the top, i.e. a so-called Rayleigh-Bénard (RB) convection cell. The temperature gradient drives a complex flow, that varies spatially and temporally [2-5]. The experimental set-up includes a number of Fluxgate sensors for highly sensitive measurements of the induced magnetic field in the order of 10 nT [6] as well as Ultrasound-Doppler velocimetry probes, that directly measure the velocity of the flow along their line-of-sight. Our preliminary measurements used only the excitation field in vertical direction, yet show a very high agreement of the time-dependent velocity profiles measured by UDV and the according CIFT data, projected onto the line-of-sight of the UDV sensors. Acknowledgement This work was supported by the German Research Foundation (DFG) under project no. 374994652. T.V. and F.S. also thank the DFG for support under the grant VO 2331/1. REFERENCES [1] Stefani F., Gundrum T., Gerbeth G., Physical Review E 70: 056306. 2004. [2] Akashi M. et al., J. Fluid Mech. 932 (2022). [3] Zürner T. et al., J. Fluid Mech. 876 (2019). [4] Vogt T. et al., PNAS 115 (2018). [5] Mitra R. et al., Magnetohydrodynamics, vol. 58 (2022) [accepted for publication]. [6] Sieger M. et al., Magnetohydrodynamics, vol. 58 (2022) [accepted for publication].

The time dependent behaviour of the large-scale circulation in a Rayleigh-Bénard convection cell exhibits a rich set of different three-dimensional flow features like rotations or torsional modes. In this paper, the applicability of the contactless inductive flow tomography (CIFT) to visualise these flow features in a cylindrical cell filled with GaInSn is investigated numerically. The simulated flow in the cylinder with a diameter of 320 mm and a height of 640 mm serves as a basis to investigate the quality of the reconstructed velocity field by CIFT.

The focus of this presentation is on the numerical study of CIFT on the same RB cell, for an experimentally feasible case of 7x6 sensor configuration and developing the measurement system based on the applicability. The two excitation magnetic fields were kept in the order of 1 mT during the simulation. Sensors are kept outside the RB cell to detect the flow-induced perturbations. The original velocity fields were simulated using OpenFoam solver with a high temporal resolution of 0.5 seconds for 8000 seconds. For reconstruction, only the transient condition between 7000th to 8000th second was considered. Torsional mode analysis is also reported.

The time dependent behaviour of the large-scale circulation in a Rayleigh-Bénard convection cell exhibits a rich set of different three-dimensional flow features like rotations or torsional modes. In this paper, the applicability of the contactless inductive flow tomography (CIFT) to visualise these flow features in a cylindrical cell filled with GaInSn is investigated numerically. The simulated flow in the cylinder with a diameter of 320 mm and a height of 640 mm serves as a basis to investigate the quality of the reconstructed velocity field by CIFT.

The focus of this presentation is on the numerical study of CIFT on the same RB cell, for an experimentally feasible case of 7x6 sensor configuration and developing the measurement system based on the applicability. The two excitation magnetic fields were kept in the order of 1 mT during the simulation. Sensors are kept outside the RB cell to detect the flow-induced perturbations. The original velocity fields were simulated using OpenFoam solver with a high temporal resolution of 0.5 seconds for 8000 seconds. For reconstruction, only the transient condition between 7000th to 8000th second was considered. Torsional mode analysis is also reported.

Contactless inductive flow tomography (CIFT) can reconstruct the complex 3-dimensional flow structure of the large scale circulation in liquid metal filled Rayleigh-Bénard (RB) convection cells. The method relies on the precise measurement of weak magnetic fields induced by currents in the conducting liquid arising from the fluid motion in combination with primary excitation fields. The velocity distribution is reconstructed from the magnetic field measurements by solving a linear inverse problem using the Tikhonov regularization and L-curve method. A number of technical challenges have to be overcome to reach the desired accuracy of the measurement signals. In this paper we will describe our design of a new CIFT set-up for a large RB vessel with a diameter of 320 mm and a height of 640 mm. We outline the major factors perturbing the measurement signal of several tens of nanoteslas and describe solutions to decrease mechanical drifts by thermal expansion to a sub-critical level to enable CIFT measurements for high-Rayleigh number flows.

Contactless inductive flow tomography (CIFT) can reconstruct the complex 3-dimensional flow structure of the large scale circulation in liquid metal filled Rayleigh-Bénard (RB) convection cells. The method relies on the precise measurement of weak magnetic fields induced by currents in the conducting liquid arising from the fluid motion in combination with primary excitation fields. The velocity distribution is reconstructed from the magnetic field measurements by solving a linear inverse problem using the Tikhonov regularization and L-curve method. A number of technical challenges have to be overcome to reach the desired accuracy of the measurement signals. In this paper we will describe our design of a new CIFT set-up for a large RB vessel with a diameter of 320 mm and a height of 640 mm. We outline the major factors perturbing the measurement signal of several tens of nanoteslas and describe solutions to decrease mechanical drifts by thermal expansion to a sub-critical level to enable CIFT measurements for high-Rayleigh number flows.

The focus of this presentation is on the numerical study of CIFT on the same RB cell, for an experimentally feasible case of 7x6 sensor configuration and developing the measurement system based on the applicability. The two excitation magnetic fields were kept in the order of 1 mT during the simulation. Sensors are kept outside the RB cell to detect the flow-induced perturbations. The original velocity fields were simulated using OpenFoam solver with a high temporal resolution of 0.5 seconds for 8000 seconds. For reconstruction, only the transient condition between 7000th to 8000th second was considered. Torsional mode analysis is also reported.

Contactless inductive flow tomography (CIFT) can reconstruct the complex 3-dimensional flow structure of the large scale circulation in liquid metal filled Rayleigh-Bénard (RB) convection cells. The method relies on the precise measurement of weak magnetic fields induced by currents in the conducting liquid arising from the fluid motion in combination with primary excitation fields. The velocity distribution is reconstructed from the magnetic field measurements by solving a linear inverse problem using the Tikhonov regularization and L-curve method. A number of technical challenges have to be overcome to reach the desired accuracy of the measurement signals. In this paper we will describe our design of a new CIFT set-up for a large RB vessel with a diameter of 320 mm and a height of 640 mm. We outline the major factors perturbing the measurement signal of several tens of nanoteslas and describe solutions to decrease mechanical drifts by thermal expansion to a sub-critical level to enable CIFT measurements for high-Rayleigh number flows.

In this talk we give an overview of the current state of the developments of the contactless inductive flow tomography (CIFT) for two different cylindrical cells with aspect ratio 1 and 0.5 for Rayleigh-Bénard convection. Both cylindrical vessels are filled with the eutectic alloy GaInSn. We address the challenges in the flow induced magnetic field measurement and show first reconstructions of the complex three-dimensional flow structure in the cell with aspect ratio 0.5.

The time dependent behaviour of the large-scale circulation in a Rayleigh-Bénard convection cell exhibits a rich set of different three-dimensional flow features like rotations or torsional modes. In this paper, the applicability of the contactless inductive flow tomography (CIFT) to visualise these flow features in a cylindrical cell filled with GaInSn is investigated numerically. The simulated flow in the cylinder with a diameter of 320 mm and a height of 640 mm serves as a basis to investigate the quality of the reconstructed velocity field by CIFT.

The focus of this presentation is on the numerical study of CIFT on the same RB cell, for an experimentally feasible case of 7x6 sensor configuration and developing the measurement system based on the applicability. The two excitation magnetic fields were kept in the order of 1 mT during the simulation. Sensors are kept outside the RB cell to detect the flow-induced perturbations. The original velocity fields were simulated using OpenFoam solver with a high temporal resolution of 0.5 seconds for 8000 seconds. For reconstruction, only the transient condition between 7000th to 8000th second was considered. Torsional mode analysis is also reported.

Contactless inductive flow tomography (CIFT) can reconstruct the complex 3-dimensional flow structure of the large scale circulation in liquid metal filled Rayleigh-Bénard (RB) convection cells. The method relies on the precise measurement of weak magnetic fields induced by currents in the conducting liquid arising from the fluid motion in combination with primary excitation fields. The velocity distribution is reconstructed from the magnetic field measurements by solving a linear inverse problem using the Tikhonov regularization and L-curve method. A number of technical challenges have to be overcome to reach the desired accuracy of the measurement signals. In this paper we will describe our design of a new CIFT set-up for a large RB vessel with a diameter of 320 mm and a height of 640 mm. We outline the major factors perturbing the measurement signal of several tens of nanoteslas and describe solutions to decrease mechanical drifts by thermal expansion to a sub-critical level to enable CIFT measurements for high-Rayleigh number flows.