Design and Optimization of Winglet Shapes for Cambered Aerofoil

K. Balaji,Apoorva Yadav 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.2

The aim of the current research work is to identify the optimum angle for winglets that control the boundary layer by generating vortices over an aerofoil. A cambered aerofoil was used to compare the spiroid, split-scimitar, and blended winglets with modified angles. Numerical analysis in Fluent software using k-omega SST turbulence models with Navier–stokes equations was carried out. The winglets were tested at a Mach number of 0.03. Based on the simulation results, the optimized winglets were fabricated and tested using a subsonic tunnel. The results showed that the optimum angles for the split, blended and spiroid winglets were respectively 140°, 95° and 40°. The NACA 6321 aerofoil at an angle of 95° for blended winglet has provided higher aerodynamic efficiency when compared to other. The optimized angle of the winglet enhanced the aerodynamic performance of the aircraft by controlling the induced drag at different angles of attack.

Electronic structure studies of nanoferrite Cu(x)Co(1-x)Fe2O4 by X-ray absorption spectroscopy.

Gautam, S,Muthurani, S,Balaji, M,Thakur, P,Padiyan, D Pathinettam,Chae, K H,Kim, S S,Asokan, K American Scientific Publishers 2011 Journal of Nanoscience and Nanotechnology Vol.11 No.1

<P>Pure and mixed cobalt copper ferrites are of great interest due to their widespread application in electronics and medicine. We report on the electronic structure of a nanoferrite Cu(x)Co(1-x)Fe2O4 (0.0 < or = x < or = 1.0) system studied by X-ray absorption spectroscopy. These magnetic nanoferrites (average crystallite size approximately 31-43 nm) were synthesized by an auto combustion method and are characterized by high resolution X-ray diffraction and near edge X-ray absorption fine structure measurements at the O K and Co, Cu, and Fe L-edges. The O K-edge spectra suggest that there is a strong hybridization between O 2p and 3d electrons of Co, Cu and Fe cations and Fe L3,2-edge spectra indicate that Fe ions coexist in mixed valence states (Fe3+ and Fe2+) at tetrahedral and octahedral sites of the spinel structure. Copper and cobalt ions are distributed in the divalent state in octahedral sites of the spinel structure. The origin of high saturation magnetization and coercivity in cobalt-copper ferrites are explained in light of these results.</P>

Significant Incidence of Extra-Articular Tibia Vara Affects Radiological Outcome of Total Knee Arthroplasty

( Balaji Saibaba ),( Mandeep S Dhillon ),( Devendra K Chouhan ),( Rajendra K Kanojia ),( Mahesh Prakash ),( Vikas Bachhal ) 대한슬관절학회 2015 대한슬관절학회지 Vol.27 No.3

Purpose: To identify and quantify the presence of extra-articular tibia vara that might influence the mechanical axis alignment after total knee arthroplasty (TKA). Materials and Methods: A total of 48 TKAs in 30 osteoarthritic Indian patients were prospectively evaluated. The hip-knee-ankle angle (HKA), joint line convergence angle, and varus angulation at the femur and tibia were measured from the preoperative and postoperative standing hip-to-ankle radiographs. Four different methods were used to measure the varus angulation at the tibia: metaphyseo-diaphyseal angle (MDA), the angle between the anatomical axis and mechanical axis of the tibia, the angle between the proximal third and distal third of tibia and the angle between the proximal half and distal half of tibia. Results: Extra-articular tibia vara quantified using MDA had the most positive correlation with HKA. Receiver operating characteristic plotting showed that MDA of >4o predicts abnormal postoperative HKA. Twenty-eight out of 48 knees had MDA of >4o, and 78.6% of these had postoperative HKA under-correction and 21.4% had less than ideal tibial component position. Conclusions: A significant inherent extra-articular varus angulation best measured using MDA exists in the proximal tibia in osteoarthritic Indian patients undergoing TKA. MDA of >4o is associated with abnormal postoperative HKA. Computer navigation may be useful for achieving ideal correction in such cases.

Prediction of negative peak wind pressures on roofs of low-rise building

K. Balaji Rao,M.B. Anoop,P. Harikrishna,S. Selvi Rajan,Nagesh R. Iyer 한국풍공학회 2014 Wind and Structures, An International Journal (WAS Vol.19 No.6

In this paper, a probability distribution which is consistent with the observed phenomenon at the roof corner and, also on other portions of the roof, of a low-rise building is proposed. The model is consistent with the choice of probability density function suggested by the statistical thermodynamics of open systems and turbulence modelling in fluid mechanics. After presenting the justification based on physical phenomenon and based on statistical arguments, the fit of alpha-stable distribution for prediction of extreme negative wind pressure coefficients is explored. The predictions are compared with those actually observed during wind tunnel experiments (using wind tunnel experimental data obtained from the aerodynamic database of Tokyo Polytechnic University), and those predicted by using Gumbel minimum and Hermite polynomial model. The predictions are also compared with those estimated using a recently proposed non-parametric model in regions where stability criterion (in skewness-kurtosis space) is satisfied. From the comparisons, it is noted that the proposed model can be used to estimate the extreme peak negative wind pressure coefficients. The model has an advantage that it is consistent with the physical processes proposed in the literature for explaining large fluctuations at the roof corners.

Modelling of strains in reinforced concrete flexural members using alpha-stable distribution

K. Balaji Rao,M. B. Anoop,K. Kesavan,S. R. Balasubramanian,K. Ravisankar,Nagesh R. Iyer 사단법인 한국계산역학회 2013 Computers and Concrete, An International Journal Vol.11 No.5

Large fluctuations in surface strain at the level of steel are expected in reinforced concrete flexural members at a given stage of loading due to the emergent structure (emergence of new crack patterns). This has been identified in developing deterministic constitutive models for finite element applications in Ibrahimbegovic et al. (2010). The aim of this paper is to identify a suitable probability distribution for describing the large deviations at far from equilibrium points due to emergent structures, based on phenomenological, thermodynamic and statistical considerations. Motivated by the investigations reported by Prigogine (1978) and Rubi (2008), distributions with heavy tails (namely, alpha-stable distributions) are proposed for modeling the variations in strain in reinforced concrete flexural members to account for the large fluctuations. The applicability of alpha-stable distributions at or in the neighborhood of far from equilibrium points is examined based on the results obtained from carefully planned experimental investigations, on seven reinforced concrete flexural members. It is found that alpha-stable distribution performs better than normal distribution for modeling the observed surface strains in reinforced concrete flexural members at these points.

Structural Analysis of Wing–Fuselage Lug Attachment

K. Balaji,Shubham Sanjay Kolhe,S. V. Khandal 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.3

The objective of this paper is to perform the stress analysis of lug joints of wing–fuselage attachment numerically and to compare the results with theoretical values. The wing and fuselage connecting points or joints are the critical in an aircraft structure. In the present work, numerical stress analysis has been carried out with bending load transfer to lug joint of a two-seated trainer aircraft and then validated with theoretical values at static conditions. The numerical analysis was done with finite element analysis and theoretical study considering stress value and margin of safety obtained. The results revealed that the maximum load to be applied for tongue attachment is 1684 kg and for fork bracket attachment is 851 kg. Finite element analysis showed maximum stress values for tongue and fork bracket, respectively, 23.150 kg/mm2 and 11.07 kg/mm2. It could be concluded that this method enhanced the strength and lifetime of attachment of fuselage and wing configuration.

Influence of Sn Doping on the Structural, Morphological, Optical and Photocatalytic Functionality of ZnO Nanostructures

K. Ganesh Kumar,P. Balaji Bhargav,Nafis Ahmed,C. Balaji 한국전기전자재료학회 2021 Transactions on Electrical and Electronic Material Vol.22 No.6

In the present study, pure and Tin (Sn) doped ZnO (Sn–ZnO) nanostructures are grown using hydrothermal method. The effect of Sn doping on the physical properties of ZnO is extensively studied. Till 4 mol% of Sn doping, the dopant is completely dissolved in the host matrix and no secondary phases are formed as evident from XRD studies. The presence of the constituent elements of the host matrix (Zn,O) and dopant (Sn) is confi rmed using Energy Dispersive X-ray Spectroscopy (EDX). From FESEM images, it is evident that the morphology of the grown structures changes from rods to flowers and flakes with doping. The microstructural analysis is carried out using HRTEM analysis. Various polar and non-polar optical modes present in the samples are analysed using Raman spectra. Two dominant emission bands around ~391 nm, ~470 nm are noticed from photoluminescence (PL) spectra. The potential of the Sn doped ZnO nanostructures in photocatalytic degradation of Rhodamine B is investigated and found that 1 mol% Sn doped ZnO exhibits superior photo catalytic performance.

Investigations on electrical properties of (PVA:NaF) polymer electrolytes for electrochemical cell applications

P. Balaji Bhargav,V. Madhu Mohan,A.K. Sharma,V.V.R.N. Rao 한국물리학회 2009 Current Applied Physics Vol.9 No.1

Solid polymer electrolytes based on poly (vinyl alcohol) (PVA) complexed with sodium fluoride (NaF) at different weight percent ratios were prepared using solution cast technique. The structural properties of these electrolyte films were examined by XRD studies. The XRD data revealed that the amorphous domains of PVA polymer matrix increased with increase of NaF salt concentration. The complexation of the salt with the polymer was confirmed by FT-IR studies. Electrical conductivity was measured in the temperature range of 303–373 K and the conductivity was found to increase with the increase of dopant concentration as well as temperature. The dielectric constant (ε') increased with the increase in temperature and decreased with the increase in frequency. A loss peak was identified at 365 K in the dielectric loss spectra and is attributed to the orientation of polar groups. Measurement of transference number was carried out to investigate the nature of charge transport in these polymer electrolyte films using Wagner’s polarization technique and Watanabe technique. Transport number data showed that the charge transport in these polymer electrolyte systems was predominantly due to ions and in particular due to anions. Using these polymer electrolytes, solid state electrochemical cells were fabricated. Various cell parameters like open circuit voltage (OCV), short circuit current (SCC), power density and energy density were determined. Solid polymer electrolytes based on poly (vinyl alcohol) (PVA) complexed with sodium fluoride (NaF) at different weight percent ratios were prepared using solution cast technique. The structural properties of these electrolyte films were examined by XRD studies. The XRD data revealed that the amorphous domains of PVA polymer matrix increased with increase of NaF salt concentration. The complexation of the salt with the polymer was confirmed by FT-IR studies. Electrical conductivity was measured in the temperature range of 303–373 K and the conductivity was found to increase with the increase of dopant concentration as well as temperature. The dielectric constant (ε') increased with the increase in temperature and decreased with the increase in frequency. A loss peak was identified at 365 K in the dielectric loss spectra and is attributed to the orientation of polar groups. Measurement of transference number was carried out to investigate the nature of charge transport in these polymer electrolyte films using Wagner’s polarization technique and Watanabe technique. Transport number data showed that the charge transport in these polymer electrolyte systems was predominantly due to ions and in particular due to anions. Using these polymer electrolytes, solid state electrochemical cells were fabricated. Various cell parameters like open circuit voltage (OCV), short circuit current (SCC), power density and energy density were determined.

Cracking in reinforced concrete flexural members - A reliability model

Rao, K. Balaji,Rao, T.V.S.R. Appa Techno-Press 1999 Structural Engineering and Mechanics, An Int'l Jou Vol.7 No.3

Cracking of reinforced concrete flexural members is a highly random phenomenon. In this paper reliability models are presented to determine the probabilities of failure of flexural members against the limit states of first crack and maximum crackwidth. The models proposed take into account the mechanism of cracking. Based on the reliability models discussed, Eqs. (8) and (9) useful in the reliability-based design of flexural members are presented.

Prediction of negative peak wind pressures on roofs of low-rise building

Rao, K. Balaji,Anoop, M.B.,Harikrishna, P.,Rajan, S. Selvi,Iyer, Nagesh R. Techno-Press 2014 Wind and Structures, An International Journal (WAS Vol.19 No.6

In this paper, a probability distribution which is consistent with the observed phenomenon at the roof corner and, also on other portions of the roof, of a low-rise building is proposed. The model is consistent with the choice of probability density function suggested by the statistical thermodynamics of open systems and turbulence modelling in fluid mechanics. After presenting the justification based on physical phenomenon and based on statistical arguments, the fit of alpha-stable distribution for prediction of extreme negative wind pressure coefficients is explored. The predictions are compared with those actually observed during wind tunnel experiments (using wind tunnel experimental data obtained from the aerodynamic database of Tokyo Polytechnic University), and those predicted by using Gumbel minimum and Hermite polynomial model. The predictions are also compared with those estimated using a recently proposed non-parametric model in regions where stability criterion (in skewness-kurtosis space) is satisfied. From the comparisons, it is noted that the proposed model can be used to estimate the extreme peak negative wind pressure coefficients. The model has an advantage that it is consistent with the physical processes proposed in the literature for explaining large fluctuations at the roof corners.