Setup

Before beginning, keep in mind that the setup I am about so show you are only one of many possibilities. I will aim to explain my decisions, but I encourage you to play around with it yourself as well.

The CSV-format we will look into is shown below. The example is given for a domain consisting of M x N elements. As the domain size must be specified in ParaView to make the grid, I have included the values of N and M when describing each column. We will later come back to why this is benefitial.

xN,     yM,     z1,     P,      U,      V       // Strings to described column
x_1,    y_1,    z_1,    P_1,    U_1,    V_1     // Number values
x_2,    y_2,    z_2,    P_2,    U_2,    V_2
.       .       .       .       .       .
.       .       .       .       .       .
x_NM,   y_NM,   z_NM,   P_NM,   U_NM,   V_NM

First of all, the most essential columns are the three first, defining the domain using a 3D coordinate system. The next columns consist of the obtained results, all as scalar values. To include vector results, e.g. velocity, we therefore have to include the velocity components as separate values. In the case above, U and V represents a velocity vector. An important parameter when writing the coordinates is that the x-values has to change faster than the y-values. Otherwise, we will get an error when creating our structured grid. Following is a demostration of how avoid this error.

  -- Correct --                -- Wrong --
x,      y,      z           x,      y,      z
1,      1,      0           1,      1,      0
2,      1,      0           1,      2,      0
1,      2,      0           2,      1,      0
2,      2,      0           2,      2,      0

Examples

Simple box

Based on my own experience, the fastest way to get known to the setup is to try it out yourself. Let's start with defining the geometry for a 2D-box consisting of 3 x 3 nodes.

x3,	y3,	z1
0,	0,	0
1,	0,	0
2,	0,	0
0,	1,	0
1,	1,	0
2,	1,	0
0,	2,	0
1,	2,	0
2,	2,	0

Although our chosen domain is in 2D, the function in ParaView that converts our table to a structured grid requires three coordinates. Effectively, z = 0 is defined for all points. As already mentioned, note that the x-values are the ones changing the fastest. This is to not get any errors when importing into ParaView.

The top row in the example; "x3 y3 z1" is in ParaView only used to describe the column, thus the values below. So, when we later get into ParaView, we will not have to remember which column represented what, but rather just look at the descriptor. The numbers behind the x, y and z is something I picked up from Bailey's great tutorial on ParaView (see ParaView). They simply describe how many points there are in the current direction, thus for our box geometry of 3 x 3 x 1 nodes we get as shown above. This is helpful knowledge when we later are to convert the points to a structured grid.

Lastly, if we have some results we wish to add, simply insert them as an additional column. 

x3,	y3,	z1,	P
0,	0,	0,	1
1,	0,	0,	1
2,	0,	0,	1
0,	1,	0,	2
1,	1,	0,	2
2,	1,	0,	2
0,	2,	0,	1.5
1,	2,	0,	1.5
2,	2,	0,	1.5

Exampel file: example_1.csv

More advanced

Although we will now look at a more complex visualization, observe how the setup is pretty much just as simple as in the last example. The task is to visualize the flow around a square cylinder. The domain is 2D and consisting of 256 x 176 nodes. As we obviously don't expect you to calculated this now, we have provided you with some data to work with.

x256,	y176,	z1,	P,				U,			V
0,		0,		0,	-0.0112616,		1,			-0.00108238,
1,		0,		0,	-0.0112616,		1,			-0.00216817,
2,		0,		0,	-0.0112615,		1,			-0.00325722,
3,		0,		0,	-0.0112613,		1,			-0.00434934,
4,		0,		0,	-0.0112611,		1,			-0.00544435,
5,		0,		0,	-0.0112607,		1,			-0.00654205,
.		.		.	.				.			.
.		.		.	.				.			.
253,	175,	0,	-7.42356e-05,	1.00768,	0.0270307,
254,	175,	0,	-0.000123269,	1.00802,	0.0272095,
255,	175,	0,	-0.000215282,	1.00844,	0.0272388,

Example file: example_2.csv

Import into ParaView

To import a file into ParaView, click Open or CTRL + O and located your file. To make it a bit more interesting, we will use example_2.csv which is attached in the section above. Then, click Apply, and a table should pop up. Make sure the table is correct, i.e. that the x-values are actually listed in the column named x256, z-coordinates in the column named z1 etc. If your file is not separated by commas, but by e.g. semi-colons, simply change the Field Delimiter Character under Properites (lower left in image below). 

Make points

The easiest way to