Dear all，

Happy new year！I'm sorry to bother you. I am a new user of nektar++, I'm currently implementing 1D blood flow simulation based on nektar++. I have two questions now.
I have some questions about the setting of the ordinate in the geometric parameters of blood vessels in the xml file. The abscissa in the geometric parameters of blood vessels is obviously related to the length of blood vessels. But is the ordinate in the geometric parameters of blood vessels related to some parameters of blood vessels? Or is the ordinate arbitrary?
The second question is that there is always negative blood flow velocity in the running result of the xml file I wrote or the xml sample provided by the official. Is this normal? I can only assume at this point that it's due to wave reflections in the blood flow.