You can explain it that way. The basic idea is that you can not use the info of downstream of the flow to decide the upstream flow. High order schemes are usually 'upwind biased'. There are also some high order central schemes. If the numerical scheme is not upwind, it will be unstable even for linear equations. Some people call it linear instability.
【在 w**d 的大作中提到】 : You can explain it that way. The basic idea is that you can not use the : info of downstream of the flow to decide the upstream flow. High order : schemes are usually 'upwind biased'. There are also some high order : central schemes. : If the numerical scheme is not upwind, it will be unstable even for linear : equations. Some people call it linear instability.