This report describes a series of free-flight tests designed to investigate various methods of body shaping to achieve low drag at transonic and supersonic speeds. In all, ten configurations were flown; three had unwaisted bodies, five were designed by area-rule methods and two were designed to achieve a specified pressure distribution in the wing-body junction. All the models had identical val...

This article reports the active control of base flows using the experimental procedure. Active control of base pressure helps in reducing the base drag in aerodynamic devices having suddenly expanded flows. Active control in the form of microjets having 0.5 mm radius placed at forty-five degrees apart is employed to control the base pressure. The Mach numbers of the present analysis are 1.7, 2....

Polymer induced drag reduction in turbulent pipe flow was investigated using a non-intrusive laser based diagnostic technique, namely Particle Image Velocimetry (PIV). The drag reduction was measured in a pressure-driven flow facility, in a horizontal pipe of inner diameter 25.3 mm at Reynolds numbers ranging from 35 000 to 210 000. Three highmolecular-weight polymers (polyethylene oxide 2×10 6...

In this study, a numerical computational fluid dynamics study is conducted in order to predict the aerodynamic forces on the NP car. The turbulent air flow around the car is modeled using the realizable k-ε model. First, results are validated against those presented for the Ahmed’s body. Next, the fluid flow around the car is simulated for different car speeds ( to mph) and fl...

An analysis was performed of the rise characteristics of bubbles, which are also growing, in a pressure Iield which is decreasing exponentially with time. The bubble rise and growth occur due to flash evaporation caused by reducing the pressure in the vapor space above a pool of liquid. Basset’s bubble momentum equation was modified to include the effects of the generated pressure wave, and to ...

Toms (1949) discovered that if a very small amount of drag reducing polymers (DRP) are added in the flow, approximately 10 ppm by weight or less, a substancial reduction in pressure drop at a given flow rate resulted. Then, since 1948, the phenomenon of drag reduction have been studied by many researchers with the objective of understand the drag reduction mechanism. In the last decades, the dr...

In this study, the boundary element method is formulated to evaluate hydrodynamic characteristics of bodies including free surface effect. The method is based on two equations, the perturbation potential boundary integral and the pressure Kutta condition, which are solved simultaneously. The method uses isoparametric elements for both quantity and geometric on the boundary. The method is first ...

In this research, the continuous adjoint method is applied to optimize an airfoil in subsonic and transonic flows. An Euler flow solver is used to analyze the inviscid compressible flow over airfoils in each design cycle. Two design problems appearing in aerodynamic shape optimization, namely inverse pressure design and drag minimization were investigated. In the first part, a test case was car...

2.1 Structure of the atmospheric boundary layer Wind is moving air caused by pressure differences in the atmosphere, initiated by temperature differences. At large heights (~1000 m) the wind is not perpendicular to the isobars but parallel to it due to the Coriolis force (perpendicular to the wind direction, caused by the rotation of the earth). This wind is denoted the geostrophic wind. G : pr...

Aerodynamic shape optimization involves designing the most efficient shapes of bodies that move through fluids. An optimization algorithm perturbs the shape of an airfoil until it finds the shape which best exhibits a given design objective. For an inverse design technique, this objective is a prescribed aerodynamic distribution, usually the surface pressure distribution. Liebeck pressure distr...