Various computational packages have the ability to plot vector fields from discrete data (i.e. measurement of velocity components). I am familiar with Mathematica. Take a look at http://reference.wolfram.com/mathematica/guide/VectorVisualization.html

I am sure equivalent software is available in Matlab

You can also use Tecplot.

Open source "GNUPLOT" would be another better option to visualize all types of the flow patterns

Thank you for your replies. My query is how to find secondary flow field?

Show the results graphically and observe it. If you find the flow component not belong to the primary flow, then it can be classified as secondary flow. Typical example is the duct flow with bent corner.

Secondary flow is clearly visible if you take out the vector data from the CFD software for example in Fluent. You can observe the vectors of secondary flow ..

Abhishek i have experimental data in plane with all three velocity components

Visualize your experimental data using any of the visualization software (GNUPLOT, ParaView, Tecplot, Matlab, Mathematica, MAPLE, etc.). The contour or vector plots may give you significant information about the nature of the flow.

You probably need to define first what is "secondary flow"