Robert H. Liebeck

Bio: Robert H. Liebeck is an academic researcher from Douglas Aircraft Company. The author has contributed to research in topics: Airfoil & Lift (force). The author has an hindex of 13, co-authored 22 publications receiving 1899 citations. Previous affiliations of Robert H. Liebeck include California State University, Long Beach.

Design of the Blended Wing Body Subsonic Transport

Abstract: The Boeing Blended-Wing-Body (BWB) airplane concept represents a potential breakthrough in subsonic transport efficiency. Work began on this concept via a study to demonstrate feasibility and begin development of this new class of airplane. In this initial study, 800-passenger BWB and conventional configuration airplanes were sized and compared for a 7000-n mile design range. Both airplanes were based on engine and structural (composite) technology for a 2010 entry into service

Design of Subsonic Airfoils for High Lift

Abstract: Nomenclature c = airfoil chord CL = lift coefficient = L/!/2pV00c CLu = upper-surface lift coefficient Cp = pressure coefficient = (p -p^)/ Ap Vx 2 Mx = freestream Mach number p = static pressure Re^ = freestream Reynolds number based on airfoil chord = V^clv sp = location of leading-edge stagnation point V^ — freestream velocity v local velocity on airfoil surface x = distance along chord line F = circulation about the airfoil 7 = ratio of specific heats v = kinematic viscosity p = density () oo = freestream conditions () t e = conditions at the airfoil trailing edge

Blended-wing-body subsonic commercial transport

Abstract: The Blended-Wing-Body (BWB) airplane concept represents a potential revolution in subsonic transport efficiency for large airplanes. NASA has sponsored an advanced concept study to demonstrate feasibility and begin development of this new class of airplane. In this study, 800 passenger BWB and conventional configuration airplanes have been compared for a 7000 nautical mile design range, where both airplanes are based on technology for a 2020 entry into service. The BWB, shown in Figure 1, has been found to be superior to the conventional configuration in all key measures.

A Class of Airfoils Designed for High Lift in Incompressible Flow

Abstract: The problem studied is that of designing a single element airfoil which provides the maximum possible lift in an unseparated incompressible flow. First, an airfoil velocity distribution is defined and optimized using boundary-layer theory and the calculus of variations. The resulting velocity distribution is then used as an input for an inverse airfoil design program which provides the corresponding airfoil shape. Since there is no guarantee that an arbitrarily defined velocity distribution will yield a physically possible airfoil shape, some parametric adjustments in the optimized distributions are required in order to obtain realistic and practical airfoil geometries. Wind-tunnel tests of two different airfoils (one assuming a laminar rooftop and the other a turbulent rooftop) have been conducted and in both cases the results met the theoretically predicted performance; for example, the laminar section exhibited a low drag range of CD — 0.0085 from CL - 0.8 to CL = 2.2.

Design of optimum propellers

Abstract: Improvements have been made in the equations and computational procedures for design of propellers and wind turbines of maximum efficiency. These eliminate the small angle approximation and some of the light loading approximations prevalent in the classical design theory. An iterative scheme is introduced for accurate calculation of the vortex displacement velocity and the flow angle distribution. Momentum losses due to radial flow can be estimated by either the Prandtl or Goldstein momentum loss function. The methods presented here bring into exact agreement the procedure for design and analysis. Furthermore, the exactness of this agreement makes possible an empirical verification of the Betz condition that a constant-displacement velocity across the wake provides a design of maximum propeller efficiency. A comparison with experimental results is also presented.

Multidisciplinary Aerospace Design Optimization: Survey of Recent Developments

Abstract: The increasing complexity of engineering systems has sparked increasing interest in multidisciplinary optimization (MDO). This paper presents a survey of recent publications in the field of aerospace where interest in MDO has been particularly intense. The two main challenges of MDO are computational expense and organizational complexity. Accordingly the survey is focused on various ways different researchers use to deal with these challenges. The survey is organized by a breakdown of MDO into its conceptual components. Accordingly, the survey includes sections on Mathematical Modeling, Design- oriented Analysis, Approximation Concepts, Optimization Procedures, System Sensitivity, and Human Interface. With the authors'' main expertise being in the structures area, the bulk of the references focus on the interaction of the structures discipline with other disciplines. In particular, two sections at the end focus on two such interactions that have recently been pursued with a particular vigor: Simultaneous Optimization of Structures and Aerodynamics, and Simultaneous Optimization of Structures Combined With Active Control.

Design of the Blended Wing Body Subsonic Transport

Abstract: The Boeing Blended-Wing-Body (BWB) airplane concept represents a potential breakthrough in subsonic transport efficiency. Work began on this concept via a study to demonstrate feasibility and begin development of this new class of airplane. In this initial study, 800-passenger BWB and conventional configuration airplanes were sized and compared for a 7000-n mile design range. Both airplanes were based on engine and structural (composite) technology for a 2010 entry into service

Design of Subsonic Airfoils for High Lift

Abstract: Nomenclature c = airfoil chord CL = lift coefficient = L/!/2pV00c CLu = upper-surface lift coefficient Cp = pressure coefficient = (p -p^)/ Ap Vx 2 Mx = freestream Mach number p = static pressure Re^ = freestream Reynolds number based on airfoil chord = V^clv sp = location of leading-edge stagnation point V^ — freestream velocity v local velocity on airfoil surface x = distance along chord line F = circulation about the airfoil 7 = ratio of specific heats v = kinematic viscosity p = density () oo = freestream conditions () t e = conditions at the airfoil trailing edge

High-Lift Aerodynamics

Abstract: c. f = chord fraction, see Eq. (5.1) H = shape factor of the boundary layer, d*/0 £ = plate length L = lift m = exponent in Cp=x flows, also lift magnification factor (5.1) M = Mach number p = pressure q = dynamic pressure Q = flow rate R = Reynolds number (= u Ox/v in Stratford flows) R6 = Reynolds number based on momentum thickness uee/v S = Stratford's separation constant (4.10); also peripheral distance around a body or wing area / = blowing slot gap, also thickness ratio of a body u = velocity in x-direction u0 = initial velocity at start of deceleration in canonical and Stratford flows v = velocity normal to the wall V = a general velocity x = length in flow direction, or around surface of a body measured from stagnation point if used in connection with boundary-layer flow