Magnetic Resonance Velocimetry
Magnetic Resonance Velocimetry (MRV) is an experimental method for determining velocity fields in fluid mechanics . MRV is based on the phenomenon of nuclear magnetic resonance and adapts magnetic resonance tomography (MRT) to medical diagnostics for the analysis of technical flows. The speeds are usually determined using the phase contrast tomography method. The speeds are calculated from the phase differences in the image data, which in turn are generated using special gradient methods. Conventional MRI machines can be used for MRV.
The term MRV arose from the increasing use of magnetic resonance tomography to measure the speed of technical flows in engineering.
Applications
The possible applications of MRV in engineering include:
- Analysis of technical flows in complex geometries ( separation , recirculation zones)
- Validation of numerical flow simulations (CFD) using 3D velocity fields
- Iterative design of complex internal flow channels (in combination with rapid prototyping )
- Measurement of velocity and phase composition of multiphase flows
- Analysis of flows through porous media
- Interaction of immiscible fluids
Advantages and Limits
In the area of non-contact speed measurement methods, in contrast to methods such as PIV or LDA, no optical access is required. In addition, no particles have to be added to the fluid. MRV thus allows the analysis of the complete flow field in complex geometries and components. Due to the fact that current MR devices are designed for the nuclear magnetic resonance of hydrogen protons, the proven applications of MRV are limited to water currents. Common scaling concepts compensate for this limitation. To achieve the spatial resolution, individual data acquisition steps must be repeated in large numbers with slight variations. Thus, the MRV technique is limited to steady or periodic flows.
See also
literature
- CJ Elkins, M. Markl, N. Pelc, JK Eaton: 4D Magnetic resonance velocimetry for mean velocity measurements in complex turbulent flows . In: Experiments in Fluids . 34, No. 4, 2003, pp. 494-503. doi : 10.1007 / s00348-003-0587-z .
- C. Elkins, MT Alley: Magnetic resonance velocimetry: applications of magnetic resonance imaging in the measurement of fluid motion . In: Experiments in Fluids . 43, No. 6, 2007, pp. 823-858. doi : 10.1007 / s00348-007-0383-2 .
- E. Fukushima: Nuclear Magnetic Resonance as a Tool to Study Flow . In: Annual Review of Fluid Mechanics . 31, 1999, pp. 95-123. doi : 10.1146 / annurev.fluid.31.1.95 .
- DN Ku, CL Biancheri, RI Pettigrew, JW Peifer, CP Markou, H. Engels: Evaluation of magnetic resonance velocimetry for steady flow . In: Journal of Biomechanical Engineering . 112, No. 4, 1990, pp. 464-472. doi : 10.1115 / 1.2891212 .
Web links
- Brief profile of Prof. John Eaton (Stanford University)
- "Magnetic Resonance Imaging for Mechanical Engineering" group
- Speed and temperature measurement in technical flows. (Medical Physics Group, Freiburg University Medical Center)
- Measurement of cytoplasmic streaming in single plant cells by magnetic resonance velocimetry. (PDF)
Individual evidence
- ^ DN Ku, CL Biancheri, RI Pettigrew, JW Peifer, CP Markou, H. Engels: Evaluation of magnetic resonance velocimetry for steady flow . In: Journal of Biomechanical Engineering . 1990.
- ↑ CJ Elkins, M. Markl, N. Pelc, JK Eaton: 4D Magnetic resonance velocimetry for mean velocity measurements in complex turbulent flows . In: Experiments in Fluids . 2003.
- ↑ C. Elkins, MT Alley: Magnetic resonance velocimetry: Applications of magnetic resonance imaging in the measurement of fluid motion . In: Experiments in Fluids . 2007.
- ↑ E. Fukushima: Nuclear magnetic resonance as a tool to study flow . In: Annual Review of Fluid Mechanics . 1999.