[annan]

Hello everyone,

I am quite new to OpenFOAM, and I have some issues understanding the difference between vectorField and volVectorField, can anyone help me understand ?

Thank you very much

Annan

[HoneyBadger]

Originally Posted by annan

Hello everyone,

I am quite new to OpenFOAM, and I have some issues understanding the difference between vectorField and volVectorField, can anyone help me understand ?

Thank you very much

Annan

I do have the same question? Have you figure it out?

[olesen]

The Field class is just a List with reference counting. So vectorField is really just a list of vectors.
The volVectorField contains the vectors for each cell (the internal field) and a list of ones for each boundary patch.

It probably makes sense if you look at the source code documentation.

[HoneyBadger]

Originally Posted by olesen

The Field class is just a List with reference counting. So vectorField is really just a list of vectors.
The volVectorField contains the vectors for each cell (the internal field) and a list of ones for each boundary patch.

It probably makes sense if you look at the source code documentation.

Thank you Olesen for your replying. I also found some documents sharing the same idea that vectorField is only a list of vectors without geometric information, while volVectorField does. Thank you for confirming that. I think vectorField is a base class which derived to volVectorField, while itself probably is not very useful for users?


Regards
Juntao

[tiam]

A vectorField can certainly be useful, for instance for working with boundary data but not only. Compared to a List, besides for reference counting mentioned by Mark, a Field also has all sorts of mathematical operations implemented.

[mmohaqeqf]

In the Programmer's Guide, they talk about list<type> and Field<type>.
For example, list<vector> and Field<vector>.
Does anyone know what the difference is between these two classes?

[mmohaqeqf]

I am going to answer my own question for future reference:
List<Type> is simply a 1-D array of type "Type", while Field<Type> is a generic template for creating a list of classes of type "Type".

[olesen]

Originally Posted by mmohaqeqf

I am going to answer my own question for future reference:
List<Type> is simply a 1-D array of type "Type", while Field<Type> is a generic template for creating a list of classes of type "Type".

Not quite. A Field is just a List with additional ref-counting for converting to/from tmp and generally intended to hold numerical types of data (eg, scalar, vector etc) whereas List could be anything (eg, strings, etc). Since we define by convention that a field holds numeric type of data, we can define various operator overloading for operating on them. That's how the "a + b" magic works on fields, but not general lists.

Edit: I just realised that I even answered almost the same thing about 2 years ago (in the same thread!!) but apparently nobody reads it. Really makes me wonder why I bother

[mmohaqeqf]

Thanks;
Don't get discouraged, Mark. You are doing a great job.
But, if you think you already have answered one particular question, you can just reference that answer for the possible future similar questions.

[openfoam_aero]

Originally Posted by olesen

Not quite. A Field is just a List with additional ref-counting for converting to/from tmp and generally intended to hold numerical types of data (eg, scalar, vector etc) whereas List could be anything (eg, strings, etc). Since we define by convention that a field holds numeric type of data, we can define various operator overloading for operating on them. That's how the "a + b" magic works on fields, but not general lists.

Edit: I just realised that I even answered almost the same thing about 2 years ago (in the same thread!!) but apparently nobody reads it. Really makes me wonder why I bother

I want to go ahead and ask a questio. You mentioned that a field is intended to hold numeric data. In programmer's guide page 29, there is a definition of Points which got me confused. It reads:

A list of cell vertex point coordinate vectors, i.e. a vectorField, that is renamed pointField using a typedef declaration;

So is it correct to understand this as "a Field being a collection of lists"?

[olesen]

Originally Posted by openfoam_aero

A list of cell vertex point coordinate vectors, i.e. a vectorField, that is renamed pointField using a typedef declaration;

So is it correct to understand this as "a Field being a collection of lists"?

Not quite. A vector (or point) is more like a struct of three values (not a list).