References and further study

Physical derivations

David Tong, Fluid Mechanics. Author-maintained undergraduate lecture notes. Use the continuum, stress and Navier–Stokes discussions alongside Chapters 1–4; the course also develops vorticity and topics beyond this introductory route.
MIT OpenCourseWare, Couette & Poiseuille Flows, 2.25 Advanced Fluid Mechanics, Fall 2013. Original course material for the wall-driven and pressure-driven experiments in Chapter 3.

D. N. Arnold, F. Brezzi and M. Fortin, A stable finite element for the Stokes equations, Calcolo 21, 337–344 (1984). Original paper introducing the enriched velocity/linear-pressure element discussed in Chapter 5.
FeatFlow, DFG benchmark 2D-2: Reynolds-100 periodic cylinder flow. The specification defines geometry, inlet normalization, outlet, force observations, temporal measurement procedure and reference calculations. Read the setup before comparing a force or Strouhal value.

How does heat spread or move with a fluid? Start heat transfer. Compare momentum diffusivity with thermal diffusivity before adding a transport analogy.
How does a solid resist the fluid load? Start structural mechanics. The traction is shared; the constitutive law and primary unknown are different.
How should I judge a computed number? Continue with numerical simulation for errors, convergence and time integration.
Which assumptions belong in a model? Use mathematical modeling as a companion reference, especially its balance, constitutive-law and boundary chapters.