newman command line utility is not designed for sending multiple request in parallel,
but you can use powershell to try running collections multiple times.
$TargetPath=".\newman"
if (test-path ".\newman") {Remove-Item -r $TargetPath -Force}
New-Item -ItemType "directory" -path ".\newman\reports"
New-Item -ItemType "directory" -path ".\newman\logs"
For ($i=0; $i -le 10; $i++) {
$TestNewmanArgs="a.json -r cli,htmlextra --reporter-htmlextra-export newman\report-$i.html"
$argz="run $TestNewmanArgs -k
"$i"
Start-Process -FilePath "C:\Roaming\npm\newman" -ArgumentList $argz -PassThru
}
just store this as ps file and then right click and use run with powershell
this will execute newman in multiple cmd processes
You can also use newmna as a nodejs library and write code to run the scripts in parallel