A model for minimizing the effects of skin drag and pressure drag is constructed. We show that a simple scaling technique can be used to transform a dual, constrained minimization problem into a volume constrained surface area minimization. We discuss some successes and failures with implementing numerical methods for the problem.

This work aims at understanding the viscous effects of the outer potential flow on Prandtl’s boundary layer. For a body moving with a constant velocity in an otherwise quiescent liquid, the non-zero viscous dissipation of the outer potential flow gives rise to an additional drag, increasing the drag calculated from the boundary layer alone. The drag is considered in three cases here, on a two-d...

An extensive experimental study is conducted to examine effects of different winglet-shapes and orientations on the vortex behind a wing, static surface pressure over the wing, and wing wake of a swept wing at various angles of attack. Four types of winglets, spiroid (forward and aft), blended, and winggrid are used in this investigation. Wing static surface pressure measurements are obtained f...

This paper discusses two adaptive feedback control approaches designed to reattach a massively separated flow over a NACA airfoil with minimal control effort using piezoelectric synthetic jet actuators and various sensors for feedback. One approach uses an adaptive feedback disturbance rejection algorithm in conjunction with a system identification algorithm to develop a reduced-order dynamical...

In many endurance sports, a large part of an athlete’s external power is used to overcome drag. This force has 3 components: friction, pressure, and, in swimming, wave drag. When the athlete’s velocity is very low, friction drag dominates. In normal sports activities, pressure drag dominates, but frictional drag is influential in the velocity range in which the airstream changes from laminar to...

This work investigates the ability of Coanda jet blowing to modify the base pressure of a cylindrical body aligned axially in a flow, and thereby, produce overall drag reduction. It is found that blowing through one or two slot jets concentric to the outer body circumference can significantly influence the entire base flow region. The recirculating wake is eliminated and is replaced by freestre...

Steady incompressible flow around a circular cylinder in an external magnetic field that is aligned with fluid flow direction is studied for Re (Reynolds number) up to 40 and the interaction parameter in the range 0 ≤N ≤ 15 (or 0 ≤M ≤ 30), where M is the Hartmann number related to N by the relation M = √2N Re, using finite difference method. The pressure-Poisson equation is solved to find press...

One of the most efficient methods of reducing drag on planing craft is the use of transverse step on the bottom of a hull. Applying steps on the hull reduces the contact area with water and as a result, it reduces drag of the craft. Planing craft are able to have one or two transverse steps. In this paper, numerical hydrodynamic performance of the stepped planing craft and its step height effec...

An inverse optimization method coupled with a multiobjective Genetic Algorithm has been applied to design a transonic wing for mid-size regional aircraft. Optimization of target pressure distributions was formulated to give minimum induced drag as well as minimum profile drag. The straight isobar pattern of pressure contours was specified on the upper surface of the wing. To design a realistic ...