Harry A. Dwyer

Solution of a three-dimensional boundary-layer flow with separation.

A method of calculating accurate solutions of the three-dimensional laminar boundarylayer equations has been developed. The method is applied to a problem that exhibits interesting crossflow phenomena, such as a flow reversal driven by crossflow convective terms and crossflow influences with zero freestream crossflow velocity. The method of solution used is an implicit finite difference scheme, and the stability and convergence properties of this scheme seemed to be good. Also, the important question of initial conditions for threedimensional boundary-layer flow is discussed, and a method of obtaining initial conditions is derived.

Computations of Magnus Effects for a Yawed, Spinning Body of Revolution

Many projectiles used by the Army are slender bodies of revolution which are launched at high spin rates. Magnus forces and moments are generated by the distorted boundary layer which results from a spinning body at angle of yaw. This paper reports the results of a combined theoretical-experimental research effort to develop a method for computing Magnus effects that would be useful in the design of artillery projectiles. The theoretical effort involves: 1) numerical calculation of the fully three-dimensional boundary layer with the added complication of interaction between surface spin and cross flow velocity; and 2) three-dimensi onal inviscid flow calculations over a body plus boundary-layer displacement surface with no plane of symmetry. Experimental measurements of turbulent boundary-layer profile characteristics, wall static pressure, and aerodynamic forces have been obtained to evaluate and provide guidance to the theoretical effort. Comparisons between the theory and the experimental data indicate very close agreement and substantiate the validity of the theoretical approach.

Experimental study of a turbulent cross jet

The turbulent characteristics of a cross jet mixing flow have been measured after the geometric cross point of the centerlines of the two nozzles. The flow has been generated by two circular nozzles and the crossing angle of the jets was fixed at 45 deg with respect to each other. The flowfield is strongly influenced by the cross point stagnation region, which creates an elliptical jet region with unusual turbulence properties. The measurements have been carried out at two Reynolds numbers, Re=5.2 and 6.5 × 10 4 , and some influences of nonsimilarity have been studied

Calculation of low Mach number reacting flows

A numerical method has been developed to calculate low Mach number and reacting flows in general and the burning and vaporization of a hydrocarbon droplet in particular. The method is time accurate and it makes use of the continuity equation to form a pressure correction. The basic transport equations have been given in finite volume form, and a predictor/corrector algorithm has been employed. The continuty equation and the pressure correction step have been solved to high numerical accuracy with the use of a direct solver technique, which also has the advantage of improved efficiency. The physical problem of the burning and vaporization of a high molecular weight hydrocarbon droplet is a very difficult one due to the very large temperature and density gradients in the flow, and also due to the complicated flow structures which develop during a droplets lifetime. The methods used in this research have successfully solved these problems, and a detailed history of the droplet has been calculated and studied.

Unsteady Three-Dimension Flow in Curved Distensible Tubes

The main objective of our current study is to investigate the impact of wall distensibility and wall motion of the aortic arch on the unsteady flow field and the resulting shear on the wall. There are currently very few computational studies in the literature that incorporate unsteady three-dimensional flow solutions with fluid-wall interactions. A major motivation for the present work is its application to fluid flow in the aortic arch where early atherosclerotic lesions important in the development of cardiovascular disease are found. The inability of researchers to precisely and accurately characterize fluid flow in blood vessels, has impeded elucidation of the link between fluiddynamics and vascular disease. The present paper is intended to serve as a part of the foundation for future studies modelling the cardiovascular system which will include the realistic geometry and physiological conditions.

Numerical simulation of chemical kinetics in a supersonic chemical vapor deposition reactor

Numerical simulation is used to study the fluid dynamics and chemical kinetics i n an arc heated plasma reactor for growing diamond films and free standing wafers. The process fluid dynamics are characterized by a supersonic underexpanded impinging jet. It is proposed that surface coverage and growth rate uniformity can be controlled i n the compressible flow field by using supersonic contckred nozzles. The eflects of the nozzle flow field on the reactor chemistry are demonstrated. Chemical kinetic calculations are performed along streamline trajectories to study chemical species distributions in the reactor flow fields. If the methane does not react enough before entering the nozzle region, the temperature drop will freeze the chemistry resulting in too much methane and not enough diamond growing species diflusing into the boundary layer. Shock heating by the terminating normal shock does reinitiate the chemical reactions. +