We present a family of exact inviscid three-dimensional Beltrami flows in horizontally periodic domain lying between two parallel free-slip boundaries. Significantly, these are not stress free: the horizontal vorticity varies on each boundary. Using direct numerical simulations (employing hyperdiffusion only for stability), we find that largest-scale member is unstable and breaks down into anis...

introduction as a dynamic phenomenon, boundary is one of the basic issues in political geography and geopolitics. it is not a geographical and fixed phenomenon; rather, it has its own internal dynamic features, creates new realities, and affects the lives of people and groups living in its vicinity. different types of boundaries, such as political, social, economic, and virtual can be impenetra...