Engineering topics

Fremaux, C. M.

Publications and source records attributed to Fremaux, C. M..

4 records

NASA NTRS2003

Prediction of Flows about Forebodies at High-Angle-of-Attack Dynamic Conditions

A Reynolds-average Navier Stokes method developed for rotorcraft type of flow problems is applied for predicting the forces and moments of forebody models at high-angle-of-attack dynamic conditions and for providing insight into the flow characteristics at these conditions. Wind-tunnel results from rotary testing on generic forebody models conducted by NASA Langley and DERA are used for comparison. This paper focuses on the steady-state flow problem.

vanDam, C. P.↗

NASA NTRS1993

Effect of geometry, static stability, and mass distribution on the tumbling characteristics of generic flying-wing models

Results from an investigation to determine the low-speed tumbling characteristics of twelve generic flying-wing models are summarized. There is a concern that airplanes with flying-wing planforms could inadvertently enter an out-of-control tumbling motion under certain conditions. The objectives of this investigation were to: 1) identify the geometric and mass-related parameters that cause flying wings to be capable of sustained tumbling, 2) analyze some of the driving mechanisms that cause tumbling, and 3) determine the feasibility of using computer simulations to predict the tumbling characteristics of flying wings. Free-tumble and free-to-pitch tests were conducted with dynamically-scaled, generic flying wing models. The use of computer simulations as a predictive tool for tumbling was explored. Results indicated that center-of-gravity location, mass distribution, and geometric aspect ratio strongly affected the tumbling characteristics of the models tested and that positive static stability did not necessarily preclude tumbling. The magnitude of dynamic effects were found to be of the same order as static effects for the models undergoing autorotation-in-pitch. The simulations indicated that the dynamic terms in the equations of motion used to predict tumbling must be obtained using experimental methods that account for the large amplitude/high pitch-rate environment that characterizes tumbling.

Fremaux, C. M.↗

NASA NTRS1991

Tail venting for enhanced yaw damping at spinning conditions

An investigation was conducted in the NASA Langley 20-ft Vertical Spin Tunnel to determine the spin and spin-recovery characteristics of a 1/11-scale model of a low-wing general aviation airplane with a horizontal tail modified with variable-size gaps to allow ventilation of the vertical stabilizer and rudder. Erect spins at symmetric loadings were tested with varying gap sizes on either or both sides of the horizontal tail. The model results indicate that the basic airplane (with no gaps) exhibits a fast, flat spin from which no recoveries can be obtained. The airplane with the modified tail has either a fast, flat spin from which no recoveries or poor recoveries may be made, or a slower, steeper spin from which fair to excellent recoveries may be obtained, depending on the size and orientation of the tail gaps. The major contribution to spin recovery was from the gap on the leeward side of the tail. Gap widths of 15-25 percent of the tail semispan were needed to produce satisfactory recovery from the flat spin.

Stough, H. P., III↗

NASA NTRS1990

Parametric analysis of swept-wing geometry with sheared wing tips

A computational parameter study is presented of potential reductions in induced drag and increases in lateral-directional stability due to sheared wing tips attached to an untwisted wing of moderate sweep and aspect ratio. Sheared tips are swept and tapered wing-tip devices mounted in the plane of the wing. The induced-drag results are obtained using an inviscid, incompressible surface-panel method that models the nonlinear effects due to the deflected and rolled-up wake behind the lifting surface. The induced-drag results with planar sheared tips are compared to straight-tapered tip extensions and nonplanar winglet geometries. The lateral-directional static-stability characteristics of the wing with sheared tips are estimated using a quasi-vortex-lattice method. For certain combinations of sheared-tip sweep and taper, both the induced efficiency of the wing and the relevant static-stability derivatives are predicted to increase compared to the wing with a straight-tapered tip modification.

Fremaux, C. M.↗