Article

Longitudinal Aerodynamic Characteristics and Wing Pressure Distributions of a Blended-Wing-Body Configuration at Low and High Reynolds Numbers

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Abstract

Force balance and wing pressure data were obtained on a 0.017-Scale Model of a blended-wing-body configuration (without a simulated propulsion system installation) to validate the capability of computational fluid dynamic codes to predict the performance of such thick sectioned subsonic transport configurations. The tests were conducted in the National Transonic Facility of the Langley Research Center at Reynolds numbers from 3.5 to 25.0 million at Mach numbers from 0.25 to 0.86. Data were obtained in the pitch plane only at angles of attack from -1 to 8 deg at Mach numbers greater than 0.25. A configuration with winglets was tested at a Reynolds number of 25.0 million at Mach numbers from 0.83 to 0.86.

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... to first order in the perturbations by (27): ...
... a a C C AB d (28) because the term of degree eight is the same λ 8 in C in Equation (6b) and in the product of A in Equation (3b) by B in Equation (4b), and thus cancels by subtraction. The coefficients in (27) are the products of three modal factors of the coupled characteristic polynomial Equation (6b), and thus are polynomials of degree six in λ, with leading term λ 6 , viz.: (29) Note that the eight coefficients a d with a = 1, …, 8 in (28), and 4 × 6 = 24 coefficients gb d with (g = 1, …, 4; b = 1, …, 6) in (29) are all determined from the 2 × 4 × 4 = 32 elements of the longitudinal Equation (7a) and lateral Equation (7b) stability matrices for the decoupled case. Substituting (28) and (29) in (27) leads to an identity between polynomials of degree seven in λ, viz.: ...
... The coefficients in (27) are the products of three modal factors of the coupled characteristic polynomial Equation (6b), and thus are polynomials of degree six in λ, with leading term λ 6 , viz.: (29) Note that the eight coefficients a d with a = 1, …, 8 in (28), and 4 × 6 = 24 coefficients gb d with (g = 1, …, 4; b = 1, …, 6) in (29) are all determined from the 2 × 4 × 4 = 32 elements of the longitudinal Equation (7a) and lateral Equation (7b) stability matrices for the decoupled case. Substituting (28) and (29) in (27) leads to an identity between polynomials of degree seven in λ, viz.: ...
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... Qin et al. [5] presented the aerodynamic study of blended wing body configuration designed under the European project, MOB. Richard J. Re [6] performed an experimental investigation to obtain force balance and wing pressure data on a 0.017 scaled model of an early blended-wing-body double deck subsonic transport configuration (without propulsion systems installation) with and without winglet. Ammar et al. [7] designed a 200 passengers capacity BWB aircraft and compared its aerodynamic performance with A320 aircraft with an emphasis on the stability of the aircraft. ...
... A distributed propulsion system has been proposed in order to improve the performance of the BWB [24,25]. According Re [26] the implementation of this system could achieve a reduction of 5.4% in TOGW and 7.8% in weight of fuel. ...
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... With the increasing environment requirements of reductions in fuel burn, noise and NO x emissions for the future civil transport [1] , the current generation civil transports cannot fulfill these requirements. Blended wing body (BWB) configuration is gradually accepted by the aviation industry for its particular advantages, and a wide variety of investigations have been carried out at NASA23 , Boeing4567 , ONERA [8] and DLR [9] for many years. In China, Northwestern Polytechnical University collaborates with Commercial Aircraft Corporation of China, Ltd. (COMAC) on 150-pas- senger BWB configuration design, and it may be the smallest BWB transport among current researches. ...
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... A preliminary study was undertaken to evaluate the accuracy of the three flow solvers in predicting the flow characteristics for a clean-wing (no nacelles) version of the BWB that had been tested in the NTF in 1997. 10,16 A photograph of that model is shown in Fig. 1. Since there was not a typical fuselage, a large fairing was created on top of the wing to cover the sting. ...
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A knowledge-based aerodynamic design method coupled with an unstructured grid Navier-Stokes flow solver was used to improve the propulsion/airframe integration for a blended wing body with boundary-layer ingestion nacelles. A new zonal design capability was used that significantly reduced the time required to achieve a successful design for each nacelle and the elevon between them. A wind-tunnel model was built with interchangeable parts reflecting the baseline and redesigned configurations and tested in the National Transonic Facility. Most of the testing was done at the cruise design conditions (Mach number of 0.85, Reynolds number of 75 million). In general, the predicted improvements in forces and moments as well as the changes in wing pressures between the baseline and redesign were confirmed by the wind-tunnel results. The effectiveness of elevons between the nacelles was also predicted surprisingly well considering the crudeness in the modeling of the control surfaces in the flow code.
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