  One-dimensional blood flow model accuracy has been verified in many studies.
This work is about introducing gravity into a one-dimensional model. For this
purpose, gravitational force was introduced into the existing model. The
boundary conditions must also be adjusted to account for gravity. For this
purpose, a method for calculating arterial resistance of the terminal arteries
during gravity changes has been developed and presented in this article. The
technique is based on the idea that the human body responds to changes in
gravity in such a way as to maintain the volume of blood delivered to the
organs.Experiments have shown that not only the pressure changes, but also the
flux and pressure waveforms change when the flow is preserved. The method of
adjusting the boundary conditions is such that the flow almost does not change
when gravity appears, but it is possible to estimate the change in pressure
dynamics. This methodology can be used in different cases related to gravity.
