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Buoyancy Driven Flow Experiments

The validation of complex computational fluid dynamics (CFD) models, like the Fire Dynamics Simulator (FDS), is a major task in fire safety science.

For model development, enhancement and validation experimental data is needed. The experimental data or rather the experimental setup has to meet the following requirements:

  • reproducible and well known experimental boundary conditions,
  • transferability of the boundary conditions into the CFD models,
  • non-invasive measurements within the area of measurement, and
  • detailed spatial and temporal resolution.

For the non-intrusive measurement of the flow, optical measurements techniques like particle image velocimetry (PIV) or laser Doppler velocimetry (LDV) are suitable. Both techniques are based on an indirect measurement of the flow by means of particles, which are seeded into the flow. PIV is a field measurement whereas LDV is a point measurement.

Thermally driven turbulent plumes are fundamental in natural fires. An experimental setup to measure the hot gas plume above an electrically heated copper block is shown below. Here, the aim is to study the flow, without the additional complexity due to combustion or pyrolysis.

Open Plume SetupExperimental setup for PIV measurement, the green plane is the laser measurement plane

The corresponding PIV measurements allow to capture the turbulent flow in detail. The following figure shows the time-averaged velocity profile for four heating rates.

Open Plume VelocityVelocity profiles above the heating block for four power settings

An extended experimental setup that is motivated by the Steckler experiments was build to investigate the spill plume out of a scaled compartment. In addition to the velocity measurements, gas temperatures are measured at a set of locations of interest, see following figure.

Spill Plume SetupExperimental setup for the investigation of the spill plume

The door's in- and outflow velocities are measured with both techniques, PIV and LDV, to consolidate the experimental data. A characteristic flow pattern is shown below.

Spill Plume DataVelocity profiles of the spill plume measured with PIV and LDV

Future experimental setups will focus on the above mentioned requirements and the reduction of complexity to allow for well-founded validation with numerical methods.

Related Publications

Velocity measurements of a bench scale buoyant plume applying particle image velocimetry
Andreas Meunders, Lukas Arnold, Alexander Belt, Alexander Hundhausen
International journal of heat and mass transfer 123, 473 - 488 (2018)

Temperature and Laser Doppler Velocimetry Measurements of a Spill Plume in a Small Scale Experiment with an Electrical Heat Source
Alexander Belt, Lukas Arnold, Leonie Rommeswinkel, Anna Tscherniewski
FireSS 2nd International Fire Safety Symposium, Neaples, Italy, 7 Jun 2017 - 9 Jun 2017, 797 - 804 (2017)

Temperature and Velocity Field Measurements for a Pure Buoyancy Driven Plume in a Enclosure
Alexander Belt, Lukas Arnold, Leonie Rommeswinkel, Anna Tscherniewski
Fire and Materials 2017, San Francisco, USA, 6 Feb 2017 - 8 Feb 2017, 225-238 (2017)

Related Theses

A study on buoyancy-driven flows: Using particle image velocimetry for validating the Fire Dynamics Simulator
Andreas Meunders
PhD thesis, 2016

Design einer Versuchsanlage zur Untersuchung der Turbulenz von auftriebsgetriebenen Strömungen
Leonie Rommeswinkel
Master thesis, 2017

Experimente zur Validierung des Fire Dynamics Simulator (FDS) – Untersuchung der Thermo- und Fluiddynamik an einer kleinskaligen Einraumgeometrie
Anna Tscherniewski
Master thesis, 2017

PIV-basierte Strömungsmessung im Modellmaßstab: Durchführung und Auswertung
Leonie Rommeswinkel
Bachelor thesis, 2015

PIV-basierte Strömungsmessungen im Modellmaßstab: Simulation und Validierung
Anna Tscherniewski
Bachelor thesis, 2015