page_title: Lorentz force velocimetry
section_title: Low Conducting media: Electrolytic solution or glass melts
hierarchical_section_title: Lorentz force velocimetry / Practical applications / Low Conducting media: Electrolytic solution or glass melts
caption_attribution_description: English: EFC figure
context_page_description: Lorentz force velocimetry is a noncontact electromagnetic flow measurement technique. LFV is particularly suited for the measurement of velocities in liquid metals like steel or aluminium and is currently under development for metallurgical applications.The measurement of flow velocities in hot and aggressive liquids such as liquid aluminium and molten glass constitutes one of the grand challenges of industrial fluid mechanics. Apart from liquids, LFV can also be used to measure the velocity of solid materials as well as for detection of micro-defects in their structures.
  A Lorentz force velocimetry system is called Lorentz force flowmeter. A LFF measures the integrated or bulk Lorentz force resulting from the interaction between a liquid metal in motion and an applied magnetic field. In this case the characteristic length of the magnetic field is of the same order of magnitude as the dimensions of the channel. It must be addressed that in the case where localized magnetic fields are used, it is possible to perform local velocity measurements and thus the term Lorentz force velocimeter is used.
context_section_description: Recent advance in LFV made it possible for metering flow velocity of media which has very low electroconductivity, particularly by varying parameters as well as using some state-of-art force measurement devices enable to measure flow velocity of electrolyte solutions with conductivity that is 10⁶ times smaller than that for the liquid metals. There are variety of industrial and scientific applications where noncontact flow measurement through opaque walls or in opaque liquids is desirable. Such applications include flow metering of chemicals, food, beverages, blood, aqueous solutions in the pharmaceutical industry, molten salts in solar thermal power plants, and high temperature reactors   as well as glass melts for high-precision optics.
  A noncontact flowmeter is a device that is neither in mechanical contact with the liquid nor with the wall of the pipe in which the liquid flows. Noncontact flowmeters are equally useful when walls are contaminated like in the processing of radioactive materials, when pipes are strongly vibrating or in cases when portable flowmeters are to be developed. If the liquid and the wall of the pipe are transparent and the liquid contains tracer particles, optical measurement techniques, are effective enough tool to perform noncontact measurements. However, if either the wall or the liquid are opaque as is often the case in food production, chemical engineering, glass making, and metallurgy, very few possibilities for noncontact flow measurement exist.
  The force measurement system is an important part of the Lorentz force velocimetry. With high resolution force measurement system makes the measurement of even lower conductivity possible. Up to date has the force measurement system continually being developed.   At first the pendulum-like setups was used (Figure 5). One of the experimental facilities consists of two high power (410 mT) magnets made of NdFeB suspended by thin wires on both side of channel thereby creating magnetic field perpendicular to the fluid flow, here deflection is measured by interferometer system,. The second setup consists of state-of-art weighting balance system (Figure 6) from which is being hanged optimized magnets on the base of Halbach array system. While the total mass of both magnet systems are equal (1 kg), this system induces 3 times higher system response due to arrangement of individual elements in the array and it's interaction with predefined fluid profile. Here use of very sensitive force measuring devices is desirable, since flow velocity is being converted from the very tiny detected Lorentz Force. This force in combination with unavoidable dead weight  of the magnet () is around . After that, the method of differential force measurement was developed. With this method two balance were used, one with magnet and the other is with same-weight-dummy. In this way the influence of environment would be reduced. Recently, it have been reported that the flow measurements by this method is possible for saltwater flows whose electrical conductivity is as small as 0.06 S/m (range of electrical conductivity of the regular water from tap).
caption: Fig. 6 : Measurement principle,  state-of-art weighting balance system : 
    
      
        
          
            F
            
              M
            
          
        
      
      {\displaystyle F_{M}}
    
  -measurement force, 
    
      
        
          
            F
            
              G
            
          
        
      
      {\displaystyle F_{G}}
    
  -gravity, 
    
      
        
          
            F
            
              C
            
          
        
      
      {\displaystyle F_{C}}
    
  -force due to spring constant, 
    
      
        
          
            c
            
              s
            
          
        
      
      {\displaystyle c_{s}}
    
  -spring constant, 
    
      
        
          
            l
            
              p
            
          
        
      
      {\displaystyle l_{p}}
    
  -length of beams, a -deflection of pan carrier, 
    
      
        
          
            a
            
              a
              b
            
          
        
      
      {\displaystyle a_{ab}}
    
  -deflection of lever, 
    
      
        
          α
        
      
      {\displaystyle \alpha }
    
   -deflection angle, 
    
      
        
          
            m
            
              0
            
          
        
      
      {\displaystyle m_{0}}
    
  -dead load, 
    
      
        
          g
        
      
      {\displaystyle g}
    
   -gravitational acceleration. Adapted from [17]
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