add methods to compute speed, density and flow at a line #1889

Job	Run time
pre-build-checks (ubuntu-latest, 3.10)	1m 4s
build (ubuntu-latest, 3.10)	5m 27s
build (macos-12, 3.10)	7m 2s
build (macos-14, 3.10)	2m 58s
build (windows-latest, 3.10)	8m 2s
test (ubuntu-latest, 3.10)	4m 41s
test (ubuntu-latest, 3.11)	4m 34s
test (ubuntu-latest, 3.12)	4m 31s
test (macos-12, 3.10)	6m 7s
test (macos-12, 3.11)	5m 46s
test (macos-12, 3.12)	6m 4s
test (macos-14, 3.10)	3m 5s
test (macos-14, 3.11)	2m 31s
test (macos-14, 3.12)	2m 23s
test (windows-latest, 3.10)	7m 44s
test (windows-latest, 3.11)	7m 52s
test (windows-latest, 3.12)	8m 23s
publish	0s
	1h 28m 14s

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