Lagrangian multiphase - Parcel size is much smaller than particle diameter

ard · May 9, 2018, 04:19

Hallo,

I try to simulate an evaporation of a droplet in a pipe flow using lagrangian Particle tracking. My task is to estimate the distance from the injector, where the complete evaporation (particle’s diameter = 0) happen.

Pipe’s length is 5 m, and I put injector in the middle of the geometry, the injector’s velocity is 466 (m/s), and I specified the injector’s input as a point, and it send particles with a an angle of 10° into the pipe. Particle Diameter is actually 0.1 mm, and i specified the flow rate in injector as the mass flow rate (which i calculated my self).
The Problem is unsteady, and the solution seems to be okay. But what I really don’t understand is

“The parcel size (um) is much smaller than the particle diameter (um)“, which it should not happen.

Does anyone have an idea how to fix this ?

Fleiga · August 14, 2020, 06:56

I faced the same problem with a file injection and can not fix it.

In the single injection panel you can define the parcel release method for instance and select constant diameter. I did not testest it yet, but it should work i guess.

I think that fluent takes the parcel as a representative element with properties like part. diameter or velocity. And for fluent it doesnt matter how big the parcel is. All calculations are done with the particles diameter like drag calculation for instance. However, i have collisonal problems, because i guess the parcel-parcel interaction is done by the parcel diameter and not the part. diameter.

May 9, 2018, 04:19	Lagrangian multiphase - Parcel size is much smaller than particle diameter	#1
ard New Member Ardalan Join Date: May 2018 Location: Chemnitz, Germany Posts: 1 Rep Power: 0	Hallo, I try to simulate an evaporation of a droplet in a pipe flow using lagrangian Particle tracking. My task is to estimate the distance from the injector, where the complete evaporation (particle’s diameter = 0) happen. Pipe’s length is 5 m, and I put injector in the middle of the geometry, the injector’s velocity is 466 (m/s), and I specified the injector’s input as a point, and it send particles with a an angle of 10° into the pipe. Particle Diameter is actually 0.1 mm, and i specified the flow rate in injector as the mass flow rate (which i calculated my self). The Problem is unsteady, and the solution seems to be okay. But what I really don’t understand is “The parcel size (um) is much smaller than the particle diameter (um)“, which it should not happen. Does anyone have an idea how to fix this ?

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August 14, 2020, 06:56		#2
Fleiga New Member Kilian Fleisch Join Date: Aug 2020 Posts: 2 Rep Power: 0	I faced the same problem with a file injection and can not fix it. In the single injection panel you can define the parcel release method for instance and select constant diameter. I did not testest it yet, but it should work i guess. I think that fluent takes the parcel as a representative element with properties like part. diameter or velocity. And for fluent it doesnt matter how big the parcel is. All calculations are done with the particles diameter like drag calculation for instance. However, i have collisonal problems, because i guess the parcel-parcel interaction is done by the parcel diameter and not the part. diameter.