Walter Maxwell wrote:
"Dan, a short represents zero impedance, thus if resistance is less than
Zo with zero reactance, the phase of the reflection coefficient is 180
degrees. Conversely, an open represents an infinite impedance thus if
the impedance is greater than Zo, the reflection coefficient is zero
degrees,"

Succinctly and well stated.

Graphics of the voltage vectors (phasors) along open-circuited and
high-impedance terminated transmission lines are gicen by Terman on page
91 of his 1955 opus. At the high-resistance termination point, it is
seen that the incindent and reflected voltages are in-phase and thus
add.

I seem to recall that this results in voltage doubling at the open
circuit due to interruption of current at the open circuit which forces
the magnetic field energy to be temporarily transferred to the electric
field (Cecil`s conservation of energy at work). Again relying on a very
old memory, I believe we called this voltage doubling the "Ferranti
effect".

Best regards, Richard Harrison, KB5WZI