Abstract: The paper concerns separated flow patterns of delta wings and its boundaries, topological analysis of separated flows and vortex flows, vortex breakdown, as well as controlled separation and vortex interaction.Flow patterns about upper and lower surfaces of a series of delta plate wings with sharpened leading-edge sweepback of 15 to 85 deg. at angles of attack up to 90 deg. at low speeds are given. There are nine types of leading-edge separated flows about upper surface; bubble, bubble vortex, streamwise vortex, concentrated stable vortex, bursting vortex, spiral flow, reversed flow, completely separated flow and asymmetric vortex. Boundary diagrams of the separated flows in the angle of attack versus leading-edge sweepback angle plane are discussed.Qualitative theory of differential equations and topology are very useful in analysing three -dimensional flows and vortex flows. Local properties near singular points, global properties and topological rules of differences between the numbers of. nodal and saddle points, as well as the evolution of the topological structures as a function of parameters have been investigated by previous authors. Now concentrated vortex of a slender wing and spiral flow of a moderate sweepback cropped delta wing are studied.Vortex breakdown usually arises in either of two predominant forms, bubble-like and spiral, and the bursting vortex flow-fields of the two-forms are described, moreover, sub-species are mentioned. The Position of vortex bursting point can be determined by jet-like distribution of axial velocity in front of it and wake-like one behind it. Theories of vortex breakdown and theoretical methods to evaluate the position of vortex bursting point are stated. Upstream movement of the bursting point of a: strake-wing is different from that of a very slender wing.Concept of controlled separation in three-dimensional flows is very important in air vehicle configuration design. The types of unstable separated flows about wings and the stability of vortex flows can be controlled by a concentrated stable vortex. The effect of strake vortex on wing vortex is studied. Displacement, coiling or merging may appear due to interaction between two stable vortices rotating in same direction. The merging of two vortices of a double delta wing and that of spanwise blowing on a wing are shown.