Dr. Laxman Vaitla worked as a Postdoctoral Fellow at Seoul National University in the School of Mechanical and Aerospace Engineering and Konkuk University in the Department of Aerospace and Information Engineering from 2010- '11 and from 2008- '10, respectively. He has received his Ph. D. in 2008 and M. Tech. in 2002 from Indian Institute of Technology (IIT) Kanpur. His primary area of interest is structural dynamics and aeroelasticity (mostly on rotary-wing aeroelasticity).




Publication Type: Journal Article
Year of Publication Publication Type Title
2014 Journal Article J. H. Lim, Shin, S. J., Laxman, V., Kim, J., and Jang, J. S., “Development of an improved framework for the conceptual design of a rotorcraft”, Aircraft Engineering and Aerospace Technology: An International Journal, vol. 86, pp. 375–384, 2014.[Abstract]

Purpose: The purpose of the present paper is to obtain the capability of designing modern rotorcrafts with enhanced accuracy and reliability.

Design/methodology/approach: Among the existing rotorcraft design programs, an appropriate program was selected as a baseline for improvement. It was based on a database comprising conventional fleets of rotorcrafts. The baseline program was not robust because it contained a simple iteration loop, which only monitored the gross weight of the aircraft. Therefore, it is not accurate enough to fulfill the quality and sophistication of a conceptual design framework useful for present and future generations of rotorcrafts. In this paper, the estimation formulas for the sizing and weight of the rotorcraft subsystem were updated by referring to modern aircraft data. In addition, trend curves for various turboshaft engines available these days were established. Instead of using the power estimation algorithm based on the momentum theory with empirical corrections, blade element rotor aerodynamics and trim analysis were developed and incorporated into the present framework. Moreover, the simple iteration loop for the aircraft gross weight was reinforced by adding a mathematical optimization algorithm, such as a genetic algorithm.

Findings: The improved optimization framework for rotorcraft conceptual design which has the capability of designing modern rotorcrafts with enhanced accuracy and reliability was constructed by using MATLAB optimization toolbox.

Practical implications: The optimization framework can be used by the rotorcraft industries at an early stage of the rotorcraft design.

Originality/value: It was verified that the improved optimization framework for the rotorcraft conceptual design has the capability of designing modern rotorcrafts with enhanced accuracy and reliability.

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2011 Journal Article V. Laxman, Lim, J. H., Shin, S. J., Ko, K. H., and Jung, S. N., “Power and Trim Estimation for Helicopter Sizing and Performance Analysis”, International Journal of Aeronautical and Space Sciences, vol. 12, pp. 156–162, 2011.[Abstract]

The preliminary design stage of helicopters consists of various operations and in each operation design several detailed analysis tasks are needed. The analysis tasks include performance and the required power estimation. In helicopter design, those are usually carried out by adopting the momentum theory. In this paper, an explicit form of computational analysis based on the blade element theory and uniform/non-uniform inflow model is developed. The other motivation of the present development is to obtain trim and required power estimation for various helicopter configurations. Sectional and hub loads, power, trim, and flapping equations are derived by using a symbolic tool. Iterative computations are carried out till convergence is achieved in the blade response, inflow, and trim. The predictions regarding the trim and power estimation turn out to be correlated well with the experimental results. The effect of inflow is further investigated. It is found that the present prediction for the lateral cyclic pitch angle is improved with the non-uniform inflow model as compared to that by the uniform inflow model. The presently improved trim and power estimation will be useful for future helicopter sizing and performance analysis. More »»
2010 Journal Article V. Laxman, Chung, C. Hoon, Lee, J. Whan, Yoon, N. Kyung, and Shin, S. Joon, “Aeroelastic Analysis of an Aircraft with High-Aspect Ratio Wings”, 한국항공우주학회 학술발표회 논문집, pp. 315–318, 2010.
2009 Journal Article V. Laxman and Venkatesan, C., “Influence of Dynamic Stall and Dynamic Wake Effects on Helicopter Trim and Rotor Loads”, Journal of the American Helicopter Society, vol. 54, p. 32001, 2009.[Abstract]

Flight test data of helicopters indicate that vibratory levels in the fuselage exhibit a wide spectrum of frequencies including the dominant blade passage frequency and its integer multiples. The present work attempts to understand the reason for the existence of several frequencies in the response of the fuselage and possible cause for this observed phenomenon by formulating a computational aeroelastic model. In this theoretical study, a systematic approach has been undertaken to identify the effects of inflow modeling and sectional aerodynamic load evaluation, on helicopter trim, rotor blade response, and hub loads. Five different combinations of aerodynamic models of increasing complexity, representing rotor inflow and sectional aerodynamic loads, have been proposed. The differential equations of motion are solved in time domain in a sequential manner to obtain the response of all the blades in the rotor system, the inflow variables, and the sectional loads at every time step. The results of the present study show that the aerodynamic model incorporating dynamic wake and dynamic stall effects introduces a wide spectrum of harmonics in the hub loads including blade passage frequency and its integer multiples. The influence of aerodynamic modeling on the variation of trim parameters with forward speed has also been brought out. It is observed that the aerodynamic model incorporating dynamic wake and dynamic stall effects predicts the trim parameters whose variation with forward speed resemble qualitatively similar to those obtained in flight test. A comparison of the variation of blade sectional lift for various aerodynamic models indicates that in the advancing side of the rotor, a dynamic stall model introduces a shift in the azimuth angle at which the minimum lift occurs. The effect of structural flap—lag coupling due to blade pretwist on trim and rotor loads has been studied, and these results are compared with those pertaining to a straight blade configuration.

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2007 Journal Article V. Laxman and Venkatesan, C., “Chaotic response of an airfoil due to aeroelastic coupling and dynamic stall”, AIAA journal, vol. 45, pp. 271–280, 2007.
2006 Journal Article V. Laxman and Venkatesan, C., “Rotor blade dynamic stall model and its influence on airfoil response”, AIAA paper, vol. 1866, p. 2006, 2006.
Publication Type: Conference Proceedings
Year of Publication Publication Type Title
2011 Conference Proceedings J. H. Lim, Shin, S. J., Laxman, V., and Kim, J., “Improvement of a Rotorcraft Preliminary Design Optimization Framework”, Journal & Proceedings, Proceedings's | Technical Reports | Overseas research abstracts | Reference DB | Engineering Design | Part Specification | Aerospace Patents | Publications Scrap | Researchers DB Overseas Development | Domestic Development | Aerospa. 2011.
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