add methods to compute speed, density and flow at a line #1888

Job	Run time
pre-build-checks (ubuntu-latest, 3.10)	1m 6s
build (ubuntu-latest, 3.10)	5m 11s
build (macos-12, 3.10)	6m 42s
build (macos-14, 3.10)	2m 53s
build (windows-latest, 3.10)	8m 6s
test (ubuntu-latest, 3.10)	4m 38s
test (ubuntu-latest, 3.11)	4m 19s
test (ubuntu-latest, 3.12)	4m 32s
test (macos-12, 3.10)	6m 49s
test (macos-12, 3.11)	5m 24s
test (macos-12, 3.12)	5m 52s
test (macos-14, 3.10)	2m 24s
test (macos-14, 3.11)	2m 24s
test (macos-14, 3.12)	3m 39s
test (windows-latest, 3.10)	8m 8s
test (windows-latest, 3.11)	6m 45s
test (windows-latest, 3.12)	7m 21s
publish	0s
	1h 26m 13s

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