Theoretical analysis of the pressure and velocity field of a bundle of rods with flow through them at an angle as a basis for the quasi-continuum theory

This work describes the important contributions which determine the resistance of flow through a grid of rods. The aim of the described procedure is to obtain simple relationships between the resulting pressure gradient and a reference velocity u vector defined by the geometry. Using the functions obtained in this way (which can be transferred to the methods of the quasi-continuum theory) acceptable approximate solutions can be obtained for mechanically complicated conditions of flow. The starting point of the fine structure analysis carried out is the solution of the velocity distribution in a typical rod grid cell, which is obtained approximately on the basis of potential and boundary layer theory. An integration of the pressure and thrust stress distribution over the structure surface with flow defines resistance values xi (theta, Re) in which all the relevant geometry and flow parameters are connected. Together with the release area modelled by eddy pairs, these data from a store of information for a variation calculation, which simulates the important conditions in a bundle with flow through it at an angle. (orig./GL)