# Geometry

External Flows - Convective flows in TEXSTAN are considered to be an external flow when the pressure gradient is user-supplied from a free-stream velocity distribution that has been derived based on a Mach number distribution, a pressure distribution, or adapted from an Euler solution. The external flow geometries that can be analyzed by setting the input flag kgeom include:

kgeom   geometry for external boundary layer flows
= 1  boundary layer flow on a 2-D planar surface (flat plates, 2-D airfoils, 2-D "flat" nozzles)
= 2  boundary layer flow over an axisymmetric body of revolution (missiles, spheres)
= 3  boundary layer flow inside an axisymmetric body of revolution (axisymmetric nozzles)

Internal Flows - Convective flows in TEXSTAN are considered to be an internal flow when the pressure gradient is considered an unknown variable. Within the numerical procedure it is guessed and often iteratively adjusted to satisfy integral conservation of mass. The internal flow geometries that can be analyzed by setting the input flag kgeom:

kgeom   geometry for internal flows
= 4  flow in a circular pipe
= 5  flow between parallel planes or in flat ducts (requires symmetric thermal boundary conditions)
= 6  flow between parallel planes or in flat ducts (symmetrical or asymmetric thermal boundary conditions)
= 7  flow in an annular duct

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