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Mehrotra, S. C.

Publications and source records attributed to Mehrotra, S. C..

13 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Stress analysis of Pathfinder-2 models

Stress analysis of the Pathfinder 2 fighter model was performed to determine a method for leading- and trailing-edge attachment that gives acceptable stress levels. Structural modeling of the wing was done using the finite element code SPAR. For the models studied, one ordinary lap joint was found to be satisfactory for the leading-edge flap, however, the alternating surface segmented lap joint method fo attachment was necessary for the trailing-edge flap to obtain acceptable stress levels.

Mehrotra, S. C.↗
NASA NTRS1983

Flat-plate drag measurements with vortex generators in turbulent boundary layer

Direct drag measurements were obtained on a flat plate with a spanwise row of vortex generators near the leading edge, to produce an array of stream wise vortices within the approaching turbulent boundary layer. The object was to explore the possibility of modifying the large scale structure of the boundary layer through embedded longitudinal vortices with a view to obtaining a reduction in wall shear. Both obstacle and vane type vortex generators were tested at free stream velocities 40 ft/sec to 130 ft/sec corresponding to plate length Reynolds no. 0.3 million to 0.8 million with a nominal boundary layer thickness of approximately 0.6 in. at the leading edge. A few vortex generator configurations were tested both on and off the plate to measure the total drag as well as the plate drag alone. The obstacle type devices reduced the plate drag, indicating that the wake momentum defect predominated even in the presence of streamwise vortices. The vane type vortex generators however always increased the plate drag.

Rao, D. M.↗
NASA NTRS1982

VORCOR: A computer program for calculating characteristics of wings with edge vortex separation by using a vortex-filament and-core model

A computer code base on an improved vortex filament/vortex core method for predicting aerodynamic characteristics of slender wings with edge vortex separations is developed. The code is applicable to camber wings, straked wings or wings with leading edge vortex flaps at subsonic speeds. The prediction of lifting pressure distribution and the computer time are improved by using a pair of concentrated vortex cores above the wing surface. The main features of this computer program are: (1) arbitrary camber shape may be defined and an option for exactly defining leading edge flap geometry is also provided; (2) the side edge vortex system is incorporated.

Pao, J. L.↗
NASA NTRS1982

Structural modeling of high Reynolds number wind tunnel models

A solid uninstrumented wing and a pressure instrumented wing having a tongue and groove type joint have been structurally modeled by using SPAR Structural Analysis System. The solid wing model can be analyzed by SPAR, using either solid elements or plate elements with reasonable accuracy. The instrumented wing models with tongue and groove joint can be modeled by using solid elements. A solid model representation for the wing with tongue and groove joint can be used for the cases where an error of 6 percent in deflections is acceptable.

Mehrotra, S. C.↗
NASA NTRS1981

Computation of wind tunnel model deflections

The experimental deflections for a transport type solid wing model were measured for several single point load conditions. These deflections were compared with those obtained by structural modeling of the wing by using plate and solid elements of Structural Performance Analysis and Redesign (SPAR) program. The solid element representation of the wing showed better agreement with the experimental deflections than the plate representation. The difference between the measured and calculated deflections is about 5 percent.

Mehrotra, S. C.↗
NASA NTRS1980

Low-aspect-ratio wings

Computer program predicts aerodynamic characteristics of wings having attached flow across part of wing and vortex flow across remainder. Program also uses quasi-vortex lattice method to formulate wing boundary conditions.

Lan, C. E.↗
NASA NTRS1980

An analytical study of effects on aeroelasticity on control effectiveness

Various uses of the Elastic Stability Derivative (ELASRAD) program are described. Topics include structural influence coefficient matrices of wings, arrow wing structural analysis, and graphic display of wing structures. The rigid and elastic stability derivatives were calculated for Transonic Aircraft Technology Project aircraft.

Mehrotra, S. C.↗
NASA NTRS1979

An improved Woodward's panel method for calculating leading-edge and side-edge suction forces at subsonic and supersonic speeds

Woodward's panel method for subsonic and supersonic flow was improved by employing control points determined by exactly matching two-dimensional pressure at a finite number of points. The results show great improvement in the predicted pressure distribution of a flapped airfoil. With the paneling scheme of cosine law in both chordwise and spanwise directions, the method is shown to accurately predict leading edge and side edge suction forces of various configurations in subsonic and supersonic flow.

Lan, C. E.↗
NASA NTRS1979

Improved Woodward's panel method for calculating edge suction forces

A new technique to improve Woodward's (1968) unified subsonic and supersonic panel method is described. The pressure prediction is improved based on a new two-dimensional theory. The method used by Lan (1977) is then used to calculate the leading-edge and side-edge suction forces by direct use of the predicted pressure distribution. The method is applicable to both subsonic and supersonic flow. It is shown that the improved Woodward panel method is capable of accurately predicting leading-edge and side-edge suction forces in subsonic and supersonic flow. Therefore, the method can be used not only to predict the vortex lift of complex planforms through the method of suction analogy, but also to calculate some lateral-directional stability derivatives.

Lan, C. E.↗
NASA NTRS1978

A computer program for calculating aerodynamic characteristics of low aspect-ratio wings with partial leading-edge separation

The necessary information for using a computer program to predict distributed and total aerodynamic characteristics for low aspect ratio wings with partial leading-edge separation is presented. The flow is assumed to be steady and inviscid. The wing boundary condition is formulated by the Quasi-Vortex-Lattice method. The leading edge separated vortices are represented by discrete free vortex elements which are aligned with the local velocity vector at midpoints to satisfy the force free condition. The wake behind the trailing edge is also force free. The flow tangency boundary condition is satisfied on the wing, including the leading and trailing edges. The program is restricted to delta wings with zero thickness and no camber. It is written in FORTRAN language and runs on CDC 6600 computer.

Mehrotra, S. C.↗
NASA NTRS1978

A computer program for calculating symmetrical aerodynamic characteristics and lateral-directional stability derivatives of wing-body combinations with blowing jets

The necessary information for using a computer program to calculate the aerodynamic characteristics under symmetrical flight conditions and the lateral-directional stability derivatives of wing-body combinations with upper-surface-blowing (USB) or over-wing-blowing (OWB) jets are described. The following new features were added to the program: (1) a fuselage of arbitrary body of revolution has been included. The effect of wing-body interference can now be investigated, and (2) all nine lateral-directional stability derivatives can be calculated. The program is written in FORTRAN language and runs on CDC Cyber 175 and Honeywell 66/60 computers.

Lan, C. E.↗
NASA NTRS1978

A theoretical investigation of the aerodynamics of low-aspect-ratio wings with partial leading-edge separation

A numerical method is developed to predict distributed and total aerodynamic characteristics for low aspect-ratio wings with partial leading-edge separation. The flow is assumed to be steady and inviscid. The wing boundary condition is formulated by the quasi-vortex-lattice method. The leading-edge separated vortices are represented by discrete free vortex elements which are aligned with the local velocity vector at mid-points to satisfy the force free condition. The wake behind the trailing-edge is also force free. The flow tangency boundary condition is satisfied on the wing, including the leading- and trailing-edges. Comparison of the predicted results with complete leading-edge separation has shown reasonably good agreement. For cases with partial leading-edge separation, the lift is found to be highly nonlinear with angle of attack.

Mehrotra, S. C.↗