Use of tcpdump-W and-R

Tcpdump instructions are as follows:
-W writes the original information package. Format: TCPDUMP-W/tmp/result.txt
I tried it today and found that all the files written in it are garbled if they are viewed using cat and Vim.
Only man tcpdump knows that the generated file must be used
Tcpdump-R, for example, tcpdump-r/tmp/result.txt.
Others:
File instead of analyzing and printing them. They can be printed later with the-r flag. If file is "-", standard output is used.
I used tcpdump to capture the NetFlow data stream of the vro. When I used the-W parameter, I found that the output of tcpdump-W is not equivalent to the NetFlow data that the vro directly sends to me.