# Accession Number:

## ADA179128

# Title:

## Viscous-Inviscid Unsteady Aerodynamics of Wings with Attached Boundary Layers.

# Descriptive Note:

## Final rept. Apr 82-Oct 84,

# Corporate Author:

## VEHICLE RESEARCH CORP PASADENA CA

# Personal Author(s):

# Report Date:

## 1985-09-01

# Pagination or Media Count:

## 101.0

# Abstract:

A linear theory treats the small amplitude pitch-heave-surge motion of a thin wing in an inviscid incompressible fluid. The wings harmonic motion is superimposed upon a straight line path. Along this path, the wing never reverses its direction. Expressions for the instantaneous values of the force, moment, power required to sustain the motion, and energy loss due to shedding of vorticity at the wings trailing edge are given as functions of the parameters defining the wings motion. The theory is expected to provide useful estimates provided the wings velocity transverse to the direction of mean forward flight remains small compared with the value of the wings local forward speed. Next, an unsteady flow about the well-rounded nose of subsonic airfoil is investigated from the viewpoint of leading edge separation flow, the fluid accelerations about the leading edge can be enormous -- according to inviscid flow theory. Such accelerations are limited by viscous flow and separation realities. Then, a theory is presented for optimizing an oscillating airfoil motion. The oscillation chosen is one of pure pitching relative to a large amplitude trajectory. The trajectory is a cycloid. The trajectory and wing motion kinematics are also presented. Finally discussed is a small perturbation fluid dynamics of large amplitude unsteady wing motion.

# Descriptors:

- *AIRFOILS
- *UNSTEADY FLOW
- KINEMATICS
- VELOCITY
- PITCH(MOTION)
- ACCELERATION
- LOADS(FORCES)
- THEORY
- ENERGY
- HARMONICS
- PATHS
- MOTION
- BOUNDARY LAYER
- MOMENTS
- VORTICES
- VORTEX SHEDDING
- SEPARATION
- PERTURBATIONS
- FLUIDS
- SUBSONIC CHARACTERISTICS
- LEADING EDGES
- LOSSES
- FLOW
- MEAN
- FLUID DYNAMICS
- LEVEL FLIGHT
- WINGS
- AMPLITUDE
- OSCILLATION
- INVISCID FLOW
- VISCOUS FLOW
- TRAJECTORIES
- FLOW SEPARATION
- AERODYNAMICS
- INCOMPRESSIBILITY
- TRAILING EDGES
- HEAVING
- THIN WINGS
- POWER ENGINEERING

# Subject Categories:

- Fluid Mechanics