A finite difference procedure is employed to evaluate the primary flow field in two typical elbows. The first has an internal wall radius equal to the width; the internal radius of the second sharper elbow is equal to one half of the width. Two dimensional flow is assumed and a 20 by 20 grid network is employed in both cases. The field is transformed into a rectangular one by generalized curvilinear coordinates. Velocity profiles and streamline patterns are presented and discussed. In both cases the outflow attains the parabolic profile assumed for the inflow. The pressure distributions on the internal and external walls have been calculated.
The stagnation region of a shock layer in front of a blunt body re-entering the atmosphere at high altitude and high velocity is considered. At these flight conditions the ionization is out of equilibrium in a considerable fraction of the shock layer thickness. The nonequilibrium phenomenon modifies the distribution of all the thermodynamic, radiative, and transport properties of the gas. To quantitatively evaluate these modifications and their influence upon the radiative heat flux, the governing equations for nonequilibrium conditions are obtained and numerically solved for real air. A simple method of evaluating nonequilibrium absorption and emission coefficients is also proposed. The numerical results show that, while nonequilibrium slightly affects the body heating load, important variations occur in the shock layer structure and the radiative flux emergent at the shock front is considerably reduced with respect to complete equilibrium conditions. This fact must be taken into account in all studies dealing with precursor effects.
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