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How to distribute particles randomly at initial time

Dear All,

I would like to simulate a channel turbulent flow with particles by using DPMFoam, there should be constant 20000 particles in the field for each time step.

My question is how to inject those 20000 particles into the field randomly at initial time, if I specify manualInjection in "kinematicCloudProperties" and use a "kinematicCloudPositions" file to specify the location of each particle, it would be troublesome.

Is there any better solution? Please let me know is you are aware of this..

Thank you!

Hi,

I know that the answer is a little bit late and maybe you already found other help.

What I would try to do is to programm a small code that can create you the random positions in a X/Y/Z-Space. You can write them out of your programm as a .txt-File. That means you can use any programming language that you want (not necessarily C++).

Have you already exeriances with programming?

Simon

Hello again,

i was writing a python-program for generating the random numbers and saving them in a file.

I put it in this post. If you want you can just copy it, paste it in your python-editor and edit the parameters.
Maybe there are better way to have the same result. So let me know if you found one.

Code:

#!/usr/bin/env python3

# -*- coding: utf-8 -*-

"""

Created on Mon May 25 10:52:19 2020



@author: simon

"""

# =============================================================================

# Program to generate random positions in a 3D box.

# Replace the positions in your kinematicCloudPositions-file with the points 

# out of the file produced by this python script.

# =============================================================================



#import scipy.interpolate as si

import numpy as np



#Number of positions and size of cubic space where they can be

noOfPositions = 2000



xMin = -0.0025

xMax =  0.0025

yMin = -0.0025

yMax =  0.0025

zMin = -0.0025

zMax =  0.0025



# round the float numbers to a number of digits

xRound = 6

yRound = 6

zRound = 6



# create a new file and open it. 

# Write also the Path from program-folder to saving-folder

file = open('Files/positions.txt', 'w') 



file.write('( \n') 



# create random numbers for X/Y/Z

for i in range(noOfPositions):

    xRand = np.round( np.random.uniform(xMin, xMax) ,xRound)

    yRand = np.round( np.random.uniform(yMin, yMax) ,yRound)

    zRand = np.round( np.random.uniform(zMin, zMax) ,zRound)

    

    # Write the random numbers in the file

    file.write('('+ str(xRand) +' '+ str(yRand) +' '+ str(zRand) +') \n') 

    

file.write(') \n') 



file.close()

As far as I am, the program is not checking if particles are created very close to each other. So they could possibly crash into each other afer calculating in openfoam.

Thank you
Simon

Sorry to answer myself always :D

can someone help me how to inject particles instead at a single timepoint in a specified timeframe?

Maybe just upload the kinematicCloudProperties or what else I have to know for this.
This would be very nice from you.

Thank you
Simon

Latin Hypercube design

Quote:

Originally Posted by Jim Shi (Post 683204)

This is one suitable approach (at least for 2D & 3D cuboids, rectangles) that do not fall directly under CFD or coding, rather than a statistical approach. It suits well for this particular purpose though (generating random positions of particles). The idea is not very complicated : Latin Hypercube Sampling, and is implemented in many packages of statistical languages (R or python for example) like https://github.com/bertcarnell/lhs