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
(No Transcript)