adb logcat -c

Usage: logcat [options] [filterspecs]options include:  -s              Set default filter to silent.                  Like specifying filterspec '*:S'  -f <filename>   Log to file. Default is stdout  -r <kbytes>     Rotate log every kbytes. Requires -f  -n <count>      Sets max number of rotated logs to <count>, default 4  -v <format>     Sets the log PRint format, where <format> is:                      brief color long printable process raw tag thread                      threadtime time usec  -D              print dividers between each log buffer  -c              clear (flush) the entire log and exit