# Thread: Silo design question

1. Raquel Aliaga Guest

## Silo design question

My name is Raquel Aliaga, I am currently working as a researcher at the ITC (Institute of Ceramic Technology), Castellon, Spain. My job focuses particularly on the design of silos, consequently I have to use Jenike's charts fairly often.

I was wondering if there is any computer programme available which is capable of calculating friction factors in a reliable way. I am also interested in knowing if there is another way (such as a data base) that professional silo designers use to obtain these parameters. If there is we could be very interested in it.

I would be very grateful if you could be able to give me any information about how to calculate these parameters accurately and more simply if possible.
Thank you for your help.

2. ## Friction Calculation -Silo Design Question

Dear Raquel,

In a manner of speaking, there is another method that can produce results simular to the Jenike shear cell tester and it has been computerized. I am speaking of the Discrete Element Method (DEM).

As I am sure you are aware, many factors control the apparent friction coefficient: rock shapes by size distribution, surface texture or roughness, moisture, elasticity and plasticity, pressure and time history of measurement related to elastic-plastic rheology, and so on.

The apparent friction, excepting relaxation, moisture, electrostatics, magnetics, Van der Wal and Einstein forces falls in the domain of surface asperity and fabric shear strength of the granular structure.

Many of these characteristics can be modelled with DEM and its off-shoots. DEM today can model complex non-round particles of large proportions. Its main advantage is in modeling larger rock size groups above 10 mm to 1000mm and larger. It can also model finer particles. Every thing is dimensionless. A DEM model size is limited to about one million simple spherical particles at present. More complex shapes utilize some of the degrees of freedom. There are other limits to the model size and size variations. Particles can be fractured and chipped.

There are a number of DEM codes that do various parts of the above described model domain. You can visit our website: www.conveyor-dynamics.com for a brief introduction on the shape complexities. Aside from our DEM code see Itasca (google search) or search for Prof. Peter Cundall, and CSIRO Australia Math and Information Sciences Dr. Paul Cleary.

Just a Thought,

Lawrence Nordell
Conveyor Dynamics, Inc.
Bellingham, Washington, USA 98225
ph 360-671-2200
fx 360-671-8450

3. L.A. van Wijk Guest
I don't think you can use DEM as an alternative to Jenike shearcell tests. On the contrary I believe you need to do shear tests to adjust the the behaviour of your DEM.

Once you have a DEM with material properties that responds correct, you may be able to use it as an alternative to the design flow-graphs of Jenike.

There are numerious databases and lists with bulk material properties but there is not one large one everyone uses.

If you need to design a silo most of the time you can use values listed in the codes. For instance the German DIN1055 Teil 1, American ACI 313-75 or Sowjet SN 302-65. The last is probably renamed?

Please be carefull with whatever values you find in whatever database. I agree with Lawrence Nordell that the properties can vary largely even within materials haven the same name.

4. ## Silo Granular Dynamics

Mr. L.A. van Wijk,

I agree and disagree with your comment on the use of DEM vs the Jenike shear test. As with the shear test, the fundamentals need calibration. DEM captures the shear fabric dynamics and can separate out many variables at play. In time, a library of data will be avaiable to share.

The most obvious benefit is the treatment of larger particle groups. No such test machine is commercially available. Jenike's tester needs a large number of particles across the shear cell, through its depth, and in compaction treatment. Do we look at the particle shapes that yield differeing apparent friction values or the many other attributes that affect friction measurements?

A significant amount of lab measurements are being compiled to authenticate the DEM procedures. Certainly, actual lab measurements are the belt procedure, if the particle group fits within the test machines specs. However, often is not the case. The machine is then testing a psuedonym. By separating the differing influences, we can better determine which procedure will yield the superior result.

Rheology is another important area where constitutive equations can be experimented with to evaluate relaxation time dependent properties. As more of these tools reach commercial status, researchers will acknowledge the benefits and funding will be available to compile such a library.

With appropriate data and granular physical properties, DEM can capture arching, ratholing, wall boundary stresses, elastic foundation interaction with the granular charge stresses and their interdependences, more physical representation of silo granular flow/stresses with all types of reclaim devices.

The Jenike shear cell tester can not differentiate the influence of charge inertias, such as with many types of compaction. Pressure reducing beams and compaction stresses on the granular charge and walls can be simulated in large containers with DEM.

We can debate DEM's applications vs the shear cell tester. I believe both have their place. I also believe, in the near future, DEM will become the tool of choice when the material properties have been cataloged. The more fundamental problem of predicting the true physics in the infinite number of granular charge configurations and their dynamics, along with optimizing charge and withdrawl methods, DEM will provide the answer.

The 3rd International Conference on DEM being held in Santa Fe, New Mexico, September 23-25, 2002 at the La Fonda hotel. Check the website: www.sandia.gov/dem/ .

With appologies, my eyes are blinded by the glory of DEM.

Lawrence Nordell
Conveyor Dynamics, Inc.
www.conveyor-dynamics.com

5. L.A. van Wijk Guest
Lawrence,

You are sure enthusiastic about DEM and I think it is certainly interesting.

Regards,
Arjen van Wijk

6. Author Guest

## Silo Design

Dear Mr. Aliaga,

If I understand your querry correctly, you want to design silos for flow only (not structural design).

We have developped a finite element program to simulate the behaviour of granular materials during storage as well as during flow. We are able to determine flow profiles. If you are interested in our research I can send you some information.

You can contact me under rombach@tu-harburg.de

Best regards
Prof. Dr.-Ing. G. Rombach

7. Jiri Zegzulka Guest
Dear Mr. Raquel Aliaga,
thank you four your interest in our work. In Laboratory of Bulk Materials-Technical University of Ostrava, integrated description of granular material flow has been developed. There are stress state description, stress peaks, flow profile sizes, arch position and pure frequency of stress pulses by bulk materials flow (see Schuettgut 1995) in the work.

I have decided to launch this work part by part, by publishing in technical magazines. The other part of my work named “Stress Peak by Bulk Solid Flow” is going to come out in last edition of the Bulk Solids Handling 2002 and also, other parts are going to be continued.

“A Model of Angle of internal friction” is going to be my eighth paper focused with studying of bulk material properties. Lost energy represented by angle of internal friction is here divided to three partial energies:

1. Energy to particle acceleration

2. Energy consumed to remove of bindings

3. Another energies

Angle of internal friction may be calculated very reliable in the work.

So much sorry, but I don’t understand your comment what is record in the list eDirectory.

We are going to know some more about our work in the follow 3 or 4 years in literature.
If you are interested in my work deeper, we may have an appointment and discuss about your questions.
Thank you for your interest.

Regards,

Jiri Zegzulka,
Director of Laboratory of Bulk Materials

http://www.lsh.vsb.cz/en/default.htm

VSB-Technical University of Ostrava

708 33 Ostrava-Poruba

Czech Republic

8. Anthony Murphy Guest

## Silo/BIn Design

You should visit the web site of the University of Newcastle Australia. TUNRA Bulk Solids Research Facility.
www.bulk.newcastle.edu.au/cbs
They have an extensive product list tested and have a computer generated design software for determing the appropriate bin shape and design to suit the meterial you wish to store and maintain flow out of.
Best Regards
Anthony Murphy
AntWorks Engineering

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