Residence Time Distribution by Particle Tracing

In this tutorial you will learn how to setup a particle tracing system to obtain the residence time distribution of flow in a T-channel. This method can essentially be applied in conjunction with any incompressible solver, like icoFoam, pisoFoam, pimpleFoam and etc.

  • Solver: pimpleFoam
  • Compatible with: OpenFOAM 7, OpenFOAM v1912
  • Model: incompressible flow, RAS turbulence model, 3D, icoUncoupledKinematicCloud
  • Physical system: Particle tracing in a T-channel for residence time distribution (RTD)


  • Description: In many engineering applications we need to know how long each fluid particle stays in a reactor. This is essentially called the residence time distribution (RTD) of fluid in the reactor. OpenFOAM solvers do not naturally provide such information to us. However, there are some useful tools for particle/tracer tracking in flow system. In this tutorial you will learn how to utilize this tracer tracking system to obtain flow path of tracers inside a T-channel with baffles. The flow system is very simple to minimize unnecessary details and to have enough space for details about setting up tracer/particle tracking system.
    The RTD is obtained by injecting an inert substance or molecule into the reactor (reactor inlets) at t = 0 and measuring the tracer concentration in the outlet stream of the reactor. The tracer should be nonreactive. Its physical properties should be similar to the fluid and it should not affect the flow behavior of the fluid in the reactor. It should not be adsorbed on the reactor walls so that it completely reflects the flow behavior of the reactor.
    In this simulation, tracers are small (100 micron) artificial particles with density 1000 kg/m3(similar to fluid density). These particles with small time constant follow fluid flow path and since we use one-way coupling, tracer presence does not affect the flow behavior. Although the obtained data is not post-processed to obtain RTD, but the raw results can be used for this purpose.

residence-time-distribution (RTD) OpenFOAM

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