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Bodapati, S.

Publications and source records attributed to Bodapati, S..

8 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Experiments On Schemes For Adaptive-Wall Wind Tunnels

Report discusses experimental investigation of various convergence schemes for adaptive-wall wind tunnel. Results show side-wall-pressure measurements used as flow variables yield same unconfined-flow conditions as those obtained by measuring streamwise and perpendicular components of velocity with laser Doppler velocimeter. Justifies use of influence coefficients in one-step and iterative convergence schemes. Also shows with one-step convergence scheme, satisfactory adaptation obtained when number of iterations reduced to one (or sometimes two).

Celik, Z. Z.↗
NASA NTRS1987

Evaluation of influence coefficient matrices for an adaptive-wall wind tunnel and applications to one-step convergence scheme

Within the framework of ventilated adaptive-wall wind tunnel testing, experiments were conducted to evaluate the influence coefficients from the side-wall pressure distribution, the streamwise velocity distribution, and the vertical velocity distribution on two control surfaces. Consideration is given to the effects of Mach number, superposition, suction, blowing, and the presence of a nonlifting model. It is shown that a single-step convergence scheme reduces the testing time by eliminating the intermediate experimental iterations; however, its success depends on the accuracy of the influence coefficients.

Celik, Z. Z.↗
NASA NTRS1985

Optimization studies for the development of adaptive wall wind tunnel

The development of adaptive wall wind tunnels makes it possible to establish interference-free boundaries in the region of the model. It is, therefore, feasible to simulate free air conditions. However, the amount of total testing time involved in establishing the required conditions and the complexity of the needed instrumentation prevent currently the use of such methods for routine production testing. Optimization studies have been proposed with the objective to find approaches which will make a more extended application of adaptive wall techniques possible. A new 25cm x 11cm adaptive wall test section was designed and installed to carry out some of these studies. Investigations envisaged are related to the development of a one step convergence method to reduce total testing time, and to measurement procedures which will permit a simplification of the instrumentation. Attention is given to the proposed concept, the test section, instrumentation, and the influence coefficients.

Bodapati, S.↗
NASA NTRS1984

Unsteady wake measurements of an oscillating flap at transonic speeds

The steady and unsteady wake profiles of an airfoil with an oscillating flap were measured at nominal free stream Mach number of 0.8 in the NASA Ames 11 x 11-foot wind tunnel. The instantaneous wake velocity and pressure profiles at four axial locations are presented up to one chord length from the trailing edge. Both fundamental harmonic frequency and typical time history data are presented to observe the effects of airfoil incidence and flap angle. The drag coefficient obtained from the wake pressure measurements is compared with that obtained from the airfoil pressure distribution.

Bodapati, S.↗
NASA NTRS1984

The use of hot-wire anemometry in transonic periodic flow

The unsteady wake profiles of an airfoil with an oscillating flap were measured in the NASA Ames 11 x 11-foot transonic wind tunnel. Laser Doppler Velocimetry (LDV) and holography techniques were used in limited region where optical accessability is available. X-hot-film wire was used to measure the wake profiles in the complete region to obtain magnitude and direction of the flow. A thorough calibration was carried out to determine the sensitivity coefficients of the hot-wire in three different tunnels at transonic speeds. A calculation procedure is established to resolve the hot-wire signals at transonic speeds and applied in the measurements of steady and periodic wake profiles. The effect of flow incidence on the hot-wire signals is evaluated and incorporated in the analyses. Typical hot-wire results are compared with the results of LDV, holography and pitot-static tube embedded with Kulite transducers.

Bodapati, S.↗
NASA NTRS1983

Flow measurements of an airfoil with deflected spoiler

Spoilers are used as an effective control surface in various stages of flight. The steady and unsteady flow characteristics change with incidence and spoiler angle. An experimental investigation is undertaken to understand the flow phenomena. Typical boundary layer and wake profiles at various incidences and spoiler angles are presented and discussed. A laminar separation is observed at low incidence and high spoiler angle. At incidence, a turbulent boundary layer develops and separation point moves downstream. Generally the wake profiles are asymmetric. When different length scales are used, the profiles become self-similar and symmetric. The importance of laser velocimetry in the reverse flow region is demonstrated by comparing the preliminary LDV measurements with the hot-wire results.

Lee, C. S.↗