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Numerical methods in flow metrology

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Velocity and temperature field before the flow meter ... The flow conditioner before a turbine flow meter ... A Vortex flow meter with an ultrasonic barrier ... – PowerPoint PPT presentation

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Title: Numerical methods in flow metrology


1
Numerical methods in flow metrology
  • Sampo Sillanpää, Centre for metrology and
    accreditation

2
Contents
  • (Flow) metrology in short
  • Numerical methods in flow metrology
  • Calculation examples
  • Conclusions

3
Short introduction to metrology
  • What about if
  • one litre would not be equal?
  • the mass of one kilogram would vary?
  • nobody knows the exact time?
  • ...the mixture of anesthesia gases would be
    unknown?

4
Metrology - the science of measurement
  • The definition of internationally accepted units
    of a measurement.
  • The realisation of units of measurement by
    scientific methods.
  • The establishment of traceability chains in
    documenting the accuracy of a measurement.

5
Metrology - the science of measurement
  • A traceability (or calibration) chain
  • the documented relationship between the
    measurement result and a measurement standard of
    a national standard laboratory.
  • Measurement result for mass flow

6
Metrology - the science of measurement
  • An example of a calibration chain small gas
    flow measurements in Finland.

7
Numerical methods in flow metrology
  • Velocity and temperature field before the meter
  • Velocity and temperature field inside the meter
  • Numerical simulations in evaluation of the
    measurement uncertainty

8
Velocity and temperature field before the flow
meter
  • The indication of a flow meter might be depended
    on the velocity profile at upstream of the flow
    meter.
  • Investigation of different flow profiles
    generated by
  • 90o bend,
  • double-elbow out of plane,
  • diffuser or nozzle.
  • Turbulent pipe flow

9
Velocity and temperature field inside the meter
  • More complex geometry
  • Usually time depended situation
  • Turbulent or laminar flow

10
Monte Carlo simulation in evaluation of the
measurement uncertainty
  • Usually applied for non-linear measurement models
  • Calculation
  • Measurement model
  • probability density functions
  • model evaluation
  • approximate distribution function
  • estimate of the output quantity value and
    associated standard uncertainty.

11
Simulation examples
  • The flow conditioner before a turbine flow meter
  • Study the efficiency of a new type compounded
    flow conditioner,
  • evaluation and validation.
  • A Vortex flow meter with an ultrasonic barrier
  • Optimise the bluff body shape,
  • minimise the pressure loss.

12
The flow conditioner before a turbine flow meter
Straight length, double-elbow, diffuser and
straight length
Flow conditioner at right and at the left the
computational domain of it
13
The flow conditioner before a turbine flow meter
The computatio-nal grid for gene-rating the
veloci-ty field for the flow conditioner
Computational grid for flow conditioner
14
The flow conditioner before a turbine flow meter
  • Calculation at volume flow rate 1000 m3/h
  • RANS and k - ? RNG turbulence model
  • Wall function
  • Fully implicit (time) discretisation

15
The flow conditioner before a turbine flow meter
With compounded conditioner
Without conditioner
With single perforated plate
Contours of axial and radial velocity vectors 10D
upstream of the flow conditioner
16
A Vortex flow meter with an ultrasonic barrier
  • Traditionally pressure sen-sors are used to
    detect vor-tices generated by a bluff body ?
    pressure losses.
  • New construction, where an ultrasonic barrier is
    used instead of pressure sensors ? smaller bluff
    body ? smaller pressure losses.

17
A Vortex flow meter with an ultrasonic barrier
  • Time depended simulation and structured grid
  • Spatial discretisation
  • convective terms upwind biased discretisation,
  • viscous terms central difference.
  • Time discretisation
  • Runge-Kutta method or
  • approximate factorisation.

18
A Vortex flow meter with an ultrasonic barrier
Comparison between measured and simulated
pressure fields behind the bluff body
19
A Vortex flow meter with an ultrasonic barrier
Pressure field of the simulated vortex street of
a triangular bluff body with a width of 24 mm
facing the edge of the inflow
20
Conclusions
  • Lower costs and better data analysis
  • Installation effects and measurement process
  • Uncertainty calculation
  • Evaluation of the magnitude of uncertainty
    components
  • Mainly in universities, not yet in NMIs

21
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