Aerodynamic Quantities Research Articles

Approximate bridging relations in the transitional regime between continuum and free- molecule flows

Approximate bridging relations for aerodynamic quantities in the transitional regime between free-molecule and continuum flows are developed. Equations are presented for heat transfer, surface shear, and drag, and are proposed for lift and pressure distribution. The equations can be considered as semiempirical. They are derived from models based on simplified kinetic theory; the structure of the equations is such that they are asymptotically correct at the free-molecule and continuum extremes, and this tends to place bounds on errors resulting from a simplified analysis. The equations presented are essentially for blunt bodies; that may be used as engineering approximations in many cases for which more rigorously developed specific relations do not exist.

Comparison of the ionized shock layer about two-and three-dimensional blunt shapes at hypersonic speeds

A comparative study of the ionized shock layer about simple two and three dimensional blunt shapes has been conducted at a Mach number of 15 and an altitude of 100,000 ft. Various shock layer profiles of the aerodynamic and thermodynamic flow quantities and electron densities are given for the inviscid and viscous regions of the flow. It is seen that the largest electron concentrations are present at the blunt nose of the configurations. Both the shock layer thicknesses and electron densities for the two dimensional bodies are greater than for the three dimensional bodies. The Gravalos numerical method was used to determine the inviscid flow results. The non-linearities in the variations of the resulting flow quantities makes it difficult to predict these results accurately by use of simple approximate methods.

Movement of air in the electric wind of the corona discharge

The mechanism of gas movement in the electric wind is considered herein, and an approximate theory presented which relates relevant electrical and aerodynamic quantities. Among others, these relationships are shown to hold for an electrostatic blower, operating on the electric-wind principle: Gas velocity is a linear function of voltage and is proportional to the square root of current; if the density of the gas is not too low, the efficiency of electrokinetic conversion near sparkover is proportional to the square root of the density, and the velocity at constant current is independent of the density; near sparkover efficiency is independent of voltage; velocity increases slowly as additional blowers are stacked in series; the ozone concentration of blower air resulting from the corona discharge is an increasing function of electric-wind velocity. The forms of the equations relating these variables are found to hold in a variety of cases, even though assumed boundary conditions are not observed experimentally. The practical utility of an electrostatic blower is limited by an efficiency of operation in the neighborhood of 1%.

Plasma Physics and Hypersonic Flight

W an object travels through air at altitudes below something like 200,000 ft and at Mach numbers greater than 12 to 15, the production of electrons in the shocked layer of air which surrounds the object has a significant effect on some of the properties of the shocked air. Above some altitude like 200,000 ft the influence of the electrons is felt at even lower Mach numbers, particularly in the ionosphere where the ambient electron density is no longer negligible. The influence of electrons is felt not only on aerodynamic quantities such as heat transfer, drag and flow field, but also on physical quantities such as transport properties, radiative emission and absorption, and electromagnetic signal interaction. The main thesis of the present paper is to show how, and under what conditions, the electrons produced by the passage of a high speed missile through the atmosphere significantly affect both aerodynamic and physical quantities. A plasma may be defined as a gas containing electrons in sufficient quantity to seriously affect the physical properties of the gas. Plasma physics then is simply the physics of such a gas. For example, the air in the shock layer surrounding a hypersonic missile may be in a plasma state if the missile is traveling at an extremely high velocity. We will first discuss in general terms the structure of a hypersonic axially symmetric flow field. This will be followed by a more detailed discussion of the shock front and boundary layer with emphasis on the electron distribution. We will then show an example of an analysis of the Boltzmann equation and the relationship of the electron scattering cross section and the electron velocity distribution function.